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Cataract Surgery in High Myopia
Cataract Surgery in High Myopia LUCIO BURATIO Centro Ambrosiano dl Mlcrochtrurgla Ocu/are, Piazza Repubb/ica, 21 .. 20124 Milan, Italy
High myopia and the complications that follow the extraction of a cataract from a highly myopic eye are described. A comparison between intracapsular and extracapsular techniques is made and the advantages of a posterior chamber IOL are evaluated. Some suggestions for reduction of capsular opacification are given. Precautions to be taken during Nd:Yag laser treatment of the posterior capsule, and vitreoretinal complications are discussed. Keywords: Capsular opacification; Cystoid macular oedema; Extracapsular cataract extraction; High myopia; Posterior chamber IOL; Nd:Yag laser caps ulotomy; Phacoemulsification; Retinal detachment
DEFINITION OF HIGH MYOPIA
Pathological myopia is a refractive defect in which the antero-posterior diameter of the globe is abnormal and in which alterations to various degrees may also occur in the radius of corneal curvature, the power and refraction index of the lens, the sclera, choroid, retina and vitreous [1). Myopia has been defined as negative preoperative refraction values of -6D [2, 31, -8D [4, 51 or -10D [6), by postoperative refraction values of +7D [7,8] or +9D [9], or by considering the power of the implanted intraocular lens (lOL), e.g. + 13 D [101. The current trend for evaluating myopia, however, is based on axial length. Some ophthalmologists define high myopia as axial length equal to or greater than 25.00 mm [10,11], whereas others use different values, such as 27.00mm [12] or 26.5mm [13]. Preoperative refraction is not a precise indicator since it does not exclude myopia oflenticular origin. Moreover, refraction is subject to variations with time and may lack precision due to the poor compliance of the patient or inexact evaluation by the assessor. Postoperative refraction parameters exclude myopias of lenticular nature but do not exclude those myopias that are the result of short corneal radius of curvature. Likewise, the implanted IOL power is not a precise parameter, as lenses have different constants for biometric calculations. Thus the most exact method is the one based on axial length. With a mean value for emmetropic eyes, i.e. a mean keratometry, of 43.40 D and a mean axial length of 23.00 mm, to calculate data for a myopic 0955-3681/91/040271 +08 $03.00/0 © 1991 Ballhere Tindall
eye with a spectacle refraction of -6.00 D, the axial length must be 3.5 mm greater
During cataract surgery, operative strain and postoperative changes, in particular those affecting the vitreous, may place the retina at risk, even in patients that do not belong to a high risk popUlation. Cataract extraction increases the risk of retinal detachment in the normal population; the incidence of retinal detachment following cataract extraction ranges from 0.4 to 3.5% [14-16]. One of the bestknown surveys, involving 5541 eyes submitted to cataract extraction, either by the extracapsular or intracapsular technique, showed an incidence of retinal detachment of 2.2%. The same study reported a greater incidence following ICCE compared with ECCE [141. Folk & Burton [17) emphasized the causative role of lens extraction in the onset of retinal detachment. They observed that in phakic patients with ipsilateral retinal detachment (in the same eye), the risk of retinal detachment in the contralateral phakic eye was low, but increased following cataract extraction. Studies on retinal detachment have reported an incidence in aphakic eyes ranging from 10.1% to 33.0% [18-201. Eur J Implant Ref Surg, Vo/3, December 1991
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Bohringer claimed that the risk of developing retinal detachment in patients older than 60 years with myopia greater than 5 D amounted to 2.4ift compared with 0.06fk in emmetropic patients of the same age group [211; this can be directly ascribed to the vitreoretinal characteristics of the highly myopic eye. Curtin reported that retinal detachment occurred in phakic non-myopic individuals with a frequency of between 0.005 and 0.010
In the case of myopic eyes, as well as for emmetropic eyes, intracapsular extraction, planned extracapsular extraction, and phacoemulsification with or without IOL implantation are the procedures performed most frequently. The various techniques are evaluated in relation to intraoperative and postoperative complications, the implantation of an IOL and recovery of correct visual function. Intracapsular Extraction (ICCE)
This technique, which has been abandoned by most surgeons, has always posed significant postoperative problems, the most important of which is retinal detachment (RD) [7, 25J. Literature data show that the incidence of RD in high myopia ranges from 5l'k [251 to 40% [3, 26J. However, the differing definitions of high myopia of the various authors partially accounts for this difference. In 1976 Ruben carried out an interesting research project on 944 eyes with different degrees of myopia,
submitted to ICCE /26]. According to his study, the rate ofRD varied depending on the refractive defect, i.e. 3.5Ck in myopias between 0 and -4 D, 4.3% in myopias between -4 and -8 D and 40% in myopias between -10 and -20D. However, Naeser and colleagues ascribed more significance to the relatively younger age of the myopic patients submitted to intracapsular cataract extraction. They reported a high incidence of RD (22.2fk) in myopic patients operated on aged under 70 years, and a frequency of 01)( in emmetropic or hypermetropic eyes of patients aged 70 or more at the time of the operation. In 1975 Hyams had already observed a greater incidence of RD in younger myopic patients and he hypothesized that the sudden detachment of the vitreous, following ICCE, a rare event in young phakic patients, may be the cause of the high RD rate. Extracapsular Extraction (ECCE)
The move from intracapsular to extracapsular surgery, in the mid 1970s, can be attributed to the improvement in stability of the Binkhorst lens that was being used at the time, and the possibility of preventing vitreoretinal complications due both to ICCE and the IOL [27, 28J. It soon became apparent that the maintenance of an intact posterior capsule could decrease the incidence of intraoperative and postoperative complications. For this reason, ECCE was immediately adopted by most surgeons, also for highly myopic cases, either with or without the implantation of an IOL and it is now the technique of choice for operations on senile and presenile cataracts not associated with serious ocular pathologies. ECCE provides significant positive results both during surgery and in the postoperative period, as well as in terms of functional recovery in the short and long term [29]. ECCE is most suitable for the peculiar anatomy of the myopic globe, and is characterized by lower intraoperative risk and fewer postoperative vitreoretinal complications than ICCE [7, 8, 131. In this respect it is worth quoting the study carried out by Jaffe [7J on two consecutive series of cataract extractions in myopic patients, the first of 122 intracapsular extractions and the second of 151 extracapsular extractions. Eyes that suffered intraoperative vitreous loss were excluded from the study. The incidence of RD was constantly lower in the group of patients submitted to extracapsular extraction: 0.66% vs 5.7% in ICCE. In his comparative study, Percival reported an ARD incidence (retinal detachment in the aphakic patient) of ll.lift in Eur J Implant Ref Surg, Vol 3, December 1991
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myopic eyes following ICCE without IOL implantation, and 2.2% after ECCE and posterior chamber IOL implantation [28].
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with an incidence of 7% in those patients whose capsule was still intact [41]. McCannell et al. noted the presence of iritis in 61 % of CMO cases observed following ICCE and implantation of an IOL of the Severin type l42]. Intraoperative Complications Miyake l43] demonstrated, by means offluorophotometry, that the breakdown of the blood-aqueous Vitreous loss is the main intraoperative problem barrier, i.e. at the origin of CMO, is greater after during cataract surgery in the emmetropic and, in ICCE and anterior chamber IOL implantation than particular, in the strongly myopic eye. Vitreous loss after ECCE with posterior chamber intraocular lens predisposes to retinal detachment since the capsular implantation. He demonstrated that the best results barrier is no longer intact and there is a high risk of are achieved with capsular fixation. the vitreous strand becoming incarcerated in the Fortunately, CMO is quite a rare occurrence in surgical wound l30]. Literature data show that myopic eyes, even in those that have suffered vitreous loss is a frequent intraoperative compli- vitreous loss. In a follow-up of 36 myopic eyes subcation [8, 31, 33]. Moreover, many authors have mitted to ECCE and IOL implantation Drews associated vitreous loss with RD. Hughes & Awens observed no cases of CMO, even in those that had [34] reported vitreous loss in 13 of20 cases of retinal suffered vitreous loss [44]. Similarly Armstrong [101 detachment (43%) while Schepens observed vitreous observed no cases ofCMO in 40 myopic eyes submitloss in eight out of 72 cases of retinal detachment ted to ECCE and IOL implantation. Ochi et al. [45] following ICCE (11 %) [18]. Krall and colleagues l34] reported an isolated case of CMO in 183 cataract found an incidence of myopia of 14% in 114 cases of extractions from globes with axial length >27 mm. vitreous loss, a condition that is more frequently The one case had suffered intraoperative vitreous associated with this complication (Table 4). Accord- loss and had been implanted with an anterior ing to the studies published by Krall et al. [34], the chamber IOL. incidence of retinal detachment increased to 17% Schepens et al. [46] studied the adherence of the following vitreous loss, compared with cases that vitreous in the macular area by dynamic inspection were free of the complication. by EI Bayadikajiura lens. They claim that CMO can be observed in cases in which the vitreous is completely liquid and the hyaloid is fully detached from Cystoid Macular Oedema (CMO) the posterior retina, a common condition in aphakic myopic eyes, and in eyes with Wagner syndrome. CMO is a classical complication that may be caused by the type of operation, the intraoperative complications, the implant or by a possible initial refracPostoperative Complications tive error 136]. Worst [37] put forward the hypothesis that CMO Literature data on the incidence of RD in myopic results from two pathogenic mechanisms: (1) the eyes submitted to ECCE fall into two categories: (1) exchange of substances between the anterior and patients with intact posterior capsule, and (2) the posterior segments and (2) the traction of the patients submitted to either capsulotomy or laser vitreous onto the macula. He reported a lower incitreatment. dence of CMO following ECCE than after ICCE. The absence of compartmentalization between the an- Patients with intact capsule. If the posterior capsule terior and the posterior segments is responsible for is intact, the movement of the vitreous towards the the complication [38-40]. anterior chamber is inhibited, the loss of hyaluronic Jaffe and colleagues claimed that the incidence of acid is reduced, the incidence of anterior hyaloid CMO is generally low in both ICCE and ECCE, rupture is lower, vitreous tractions are decreased and posterior vitreous detachments occur with when surgery is devoid of complications [36]. Intraoperative vitreous loss and chronic post- reduced frequency 1291. operative iritis can considerably increase the freIn his study on the incidence of posterior vitreous detachment in post-mortem eyes submitted to extraquency ofCMO l301. Winslow and colleagues observed a significant capsular cataract extraction, McDonnel [471 increase in CMO when intraoperative capsulotomy reported a significantly lower rate (40%) in eyes was performed, and in the case of vitreous loss; 12 with intact capsule, compared with those that had months after surgery 38% of the cases had developed undergone primary or secondary capsulotomy (869C lCMO, as determined by fluorangiography, compared It is generally accepted that, when the capsule is cur J Implant Ref Surg. Vol 3. December 1991
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intact, this results in fewer vitreoretinal complications, both in the population in general and in myopic patients [7, 8, 14, 301. Literature data give incidences of 1.1 % r28], 0.7% [7], 2.85% [12], 0.8% r8] and 0% [44]. Since myopia, followed by aphakia, is the most significant risk factor with regard to the onset of retinal detachment, an intact capsule certainly results in fewer complications.
Patients with caps ulotomy. Capsulotomy, a procedure that is often necessary some time after ECCE, partially thwarts the efficacy of primary surgery in terms of vitreoretinal complications. Although technical problems have been solved with the introduction of the Nd:Yag laser, which permits fine control by the surgeon, the clinical complications arising from the absence of a barrier between the two ocular compartments have not yet been resolved. The open capsule increases the risk of aphakic or pseudoaphakic retinal detachment, in particular in myopic patients r48]. Coonan observed an increase in RD from 0.8% to 2.75% r8], following Nd:Yag capsulotomy, while Percival reported a rise in RD from 1.1 % with intact capsule to to 5.5% following Yag laser capsulotomy r28] and many other cases have been mentioned in the literature [49, 50]. Fastemberg et al. described five cases of rhegmatogenous detachment occurring within one month after Vag laser capsulotomy; however, they did not specify the frequency rate on the total number of cases treated [49]. Winslow & Taylor r5l] recently reported on 18 cases of retinal complications after Vag laser capsulotomy and ten retinal detachments. They concluded that retinal complications were due either to the rupture of the capsule or to related vitreous movements, thus excluding a specific link with the Nd:Yag laser. In contrast, Praeger's case study [12] did not highlight any difference between patients submitted to Vag laser capsulotomy and controls. However, since most authors agree that Vag laser cap.sulotomy. is not immune to vitreoretinal complicatIOns, speCIal care must be taken with higher risk ~oups, i.e. ~ccording to Shah's classification [52], hI~hly myopIC patients, individuals with a history of retI.nal detachment in the adelphous eye, and patIents with peripheral rhegmatogenous degeneration. Therefore, the problem has now shifted to the frequency of posterior capsule opacification, the means available to curb opacification and the parameters of a less dangerous procedure of capsulotomy.
Posterior Capsule Opacification
The data on the incidence of secondary cataract vary in the literature, depending on the refracting defect the possible presence of an IOL and the follow-u~ period. It is worth underlining that ECCE recommended for .axial myopias shows the highest incidence ofpostenor capsule opacification requiring laser treatment: mean values range between 45% and 60%. Pathogenesis of such a phenomenon may be related to the younger age of these patients, characterized by more active proliferative opacification of the residual epithelium and stronger capsular retraction. It is generally agreed that the incidence of posterior capsule opacification is lower following the implantation of a posterior chamber IOL. Percival [48] reported a decrease in opacification from 45% (ECCE) to 9% (ECCE + IOL) during a 3year follow-up period and Liesegang et al. [56] observed a 22.1 % incidence of opacification following ECCE without implantation vs 9.1% in ECCE with posterior chamber IOL during a follow-up period of2 ye~rs. Nishi reported a decrease in capsular opacificatIOn, caused by the implantation of a posterior chamber IOL (15% vs 7.1%). All the authors mentioned above recommended the implantation of a posterior chamber IOL, after careful calculation, in the myopic eye. Posterior chamber IOLs do not directly influence the ~isk of retinal detachment. However, they may partIally prevent the opacification of the posterior capsule and the related risk of laser treatment. According to Stark [65], Vag laser capsulotomy causes associated interruption of the anterior hyaloid surface. This phenomenon increases the vitreoretinal risk. The presence of a posterior chamber IOL dams the movements of the vitreous towards the anterior chamber after Vag laser capsulotomy. Terry.et al. [66] reported six cases of vitreous prolapse mto the anterior chamber out of 19 aphakic patients, following Vag laser capsulotomy, and no cas~s of vitreous prolapse out of 30 pseudophakic patIents. Type of IOL and Capsular Opacification
The ~esign of the posterior chamber lens plays a very Important role in the reduction of the incidence of capsular opacification and its development over time. According to recent studies two processes can lead to capsular opacification following ECCE [64]. The first is the transformation of epithelial cells into myofibroblasts that contract and cause the formation of numerous microfolds and small puckers endEur J Implant Ref Surg. Vol 3. December 1991
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ing in the clinical onset of capsular fibrosis. The second process is the migration and proliferation of epithelial cells on the posterior capsule, with the formation of Elschnig's pearls. The effect ofIOL design on the above mechanisms is still the object of controversy. However, it has been ascertained that the two phenomena occur less frequently after the implantation of an IOL. At present, lenses with posteriorly convex optics are attracting attention. Simcoe [67] showed that the adherence of the posterior capsule to the posterior lens surface inhibited the migration of the epithelial cells, thus preventing the formation of Elschnig's pearls. Lindstrom & Harris [581 claimed that the posterior convexity of the lens caused better adhesion between the capsule and the posterior lens surface in general, thus exerting a barrier effect against the formation of Elschnig's pearls. In contrast, Sterlin [68] reported a higher incidence of capsular fibrosis with posteriorly convex lenses. In-vitro studies have confirmed the tendency of the lenticular epithelium to develop metaplasia of the myofibroblasts, stimulated by the close contact between the capsule and the posterior IOL surface. The lens type most suitable to prevent or decrease the size and frequency of pearls and capsular fibrosis is still a controversial matter. However, it appears certain that lenses with a posterior plano-convex surface, continuous laser ridge lenses, and meniscus-type lenses show the best performance, provided that close contact between the capsule and the optic disk or betwe~n the capsule and the space maintainer is effectively maintained. Experience with highly myopic patients indicates that it is advisable to choose a lens which has a 6.57.0mm large optic, is 14-15mm long for sulcus fixation, single piece, posteriorly convex and has loops with an angle of at least 15°. An implant of this type guarantees that the ratio between the size of the globe and the size of the IOL will reflect the true dimensions of the myopic eye, resulting in greater stability and better vitreous support; the large optic promotes contact between the posterior IOL surface and the posterior capsule. The convex posterior surface facilitates the attachment of the posterior capsule to the whole optic making the exploration of the fundus easier (in this respect it is advisable to implant lenses without positioning holes), also due to the effect of the large optic. Better optic centering on the pupillary region can also be achieved. The total IOL length is also a significant parameter in the case of myopic patients. Usually, the diameter of the sulcus approximately corresponds with the corneal diameter from white to white. In the highly myopic patient this ratio is Eur J Implant Ref Surg. Vol 3. December 1991
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more or less constant. However, absolute values increase due to the oversize typical of this type of eye. Regular measurements of the corneal diameter have demonstrated that in the case of high myopia it is advisable to implant a 14.0-15.0 mm lens if ciliary sulcus fixation has been planned. If the lens seems to be too small, it is necessary to choose bag fixation. Standard size lenses can be implanted inthe-bag. PERSONAL CASE STUDY
A group of 242 myopic patients-a total of 359 eyes-of age ranging from 35 to 89, axial length greater than or equal to 26.5 mm at A-scan ultrasonography, submitted to extracapsular cataract extraction, was considered. The mean follow-up period was 36 months (minimum 18 months and maximum 60 months). Extracapsular cataract extraction was performed by means of phacoemulsification on the pupillary plane and at posterior chamber level in 95% of cases (341 eyes), and by planned extracapsular extraction methods with automated II A in 5% of the cases (18 eyes). All operations were carried out by the same surgeon. The patients studied were divided into two groups to allow a schematic classification, and the second group was further subdivided: 203 eyes without IOL. (2) 156 with posterior chamber IOL. (2a) 109 eyes with sulcus fixation. (2b) 47 eyes with capsular fixation.
(1)
One hundred and fifty-six IOLs were implanted, of which 11 had negative dioptric power, three had zero power and 142 had positive power (from + 1 to + 12.00). No IOLs were implanted in 203 eyes for the following reasons: (1) the IOL was deemed to be unnecessary for optical reasons (at the beginning of the study); (2) previous cataract surgery had occurred without IOL in the fellow eye; (3) IOL implantation was refused by the patient. The study covered a mean follow-up period of 36 months during which the following parameters were evaluated: (1) incidence of posterior capsule opacification in the non-implanted eyes and in the eyes with IOL, also with regard to sulcus vs bag fixation; (2) incidence of retinal detachment of the postoperative course before and after possible Nd:Yag laser capsulotomy. Capsulotomy was always performed by means of the Microruptor II by Lasag, on 'fundamental mode', with energy equal to 1.21.4 mJ, three bursts, a number of spots varying from
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4 to 25 and the use of a CGP 1.2 contact lens. The treatment was always implemented by the same ophthalmologist and consisted of capsular openings of variable width (from 3 to 4 mm). Capsulotomy never exceeded the limit of the optic. In this study, an attempt to evaluate the safest procedure to reduce vitreoretinal complications through a statistical analysis of the operated eyes with and without posterior chamber artificial lenses was undertaken. Moreover, the incidence of capsular opacification was studied in the eyes without IOL and in the eyes with IOL, as well as the frequency of retinal detachment in the postoperative period prior to Yag laser treatment and following Nd:Yag laser capsulotomy.
RESULTS
capsular opacification occurred in 119 eyes (33.1%) of the cases after 21 months on average. Retinal Detachment
Patients without an 10L. No retinal detachments were observed in the postoperative period prior to possible Yag laser capsulotomy. Three retinal detachments occurred following Yag laser capsulotomy (1.4%) (Table 3). Table 3
Retinal opacification in myopic patients Retznal detachment Postyag No. Preyag IOL 0 3 No 203 1 2 156 Sulcus + Bag Total 359 1 5
(If
1.4 1.9
Patients with an 10L. One retinal detachment was observed in the eyes with posterior chamber IOLs, Capsular opacification was observed in 154 out of prior to Yag laser treatment (11156,0.64%). Retinal 359 eyes (42.9%). detachment occurred in two eyes following Yag laser capsulotomy (2/156, 1.28%) (Table 3). No compliPatients without an 10L. In the myopic eyes without cations were observed in the 109 eyes with sulcusIOL (203 eyes) posterior capsule opacification fixated IOL prior to laser treatment. requiring Nd:Yag laser capsulotomy accounted for Following capsulotomy, two eyes suffered retinal 59.6% of the cases (121 eyes) (Table 1). Opacification detachment during the first 3 months after treatoccurred, on average, after 1 year. ment (2/109, 1.8%) (Table 4). Only one of the 47 eyes Capsular Opacification
Table 1 Capsular opacification in myopic patients Capsular opacificatIOn No. Yes IOL No No 203 121 82 122 156 34 Sulcus + Bag Total 359 155 204
Iff.
59.6 21.8
Patients with an 10L. Capsular opacification was observed in 34 out of 156 eyes, 21.8% of the eyes with a posterior chamber IOL (Table 2). Table 2 Capsular opacification in myopic patients IOLs Capsular opacificatIOn Yes No IOL No. 27 82 Sulcus 109 Bag 47 7 40 Total 156 34 122
with
'lr
24.8 14.9
Capsular opacification developed in 27 out of 109 eyes with sulcus fixation (24.8lj() during a mean period of 17 months; 14.9% of the 47 eyes with capsular bag fixation suffered from opacification (seven eyes) during a mean period of 19 months. In a nonmyopic control group that had been previously studied (359 eyes with posterior chamber IOL, of which 272 in the sulcus and 87 in the capsular bag)
Table 4 Retinal detachment in myopic patients Retznal detachment Post yag IOL No. Pre yag 2 Sulcus 109 0 1 0 Bag 47 Total 2 156 1
'if
1.8 2.1
with capsular bag fixation suffered retinal detachment without laser treatment (2.1 %). In the remaining follow-up period, and also following laser capsulotomy, no complications ensued.
REMARKS Some significant considerations can be made on analysis of the results. In terms of posterior capsule opacifications we have observed the following. Myopic non-implanted eyes suffer more capsular opacification than eyes with posterior chamber IOLs. On average, 59.6% of the non-implanted eyes (1211203) required laser capsulotomy 12 months after surgery. Opacification occurred in 21.8% of the implanted eyes (34/156) after a longer period of time (18 months). The presence of an intraocular lens retards capsuEur J Implant Ref Surg. Vol 3. December 1991
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lar opacification in myopic patients (12 months without an IOL vs 18 months with an IOU. Among the implanted eyes, those with bag fixation show a lower rate of capsular opacification compared to sulcus fixation. Only 14% of them (7/47) required Yag laser capsulotomy after a longer period of time (19 months with bag fixation vs 17 months with sulcus fixation) but this result is not statistically significant. Both the group without IOLs (1.4%) and the implanted group (1.9%), as well as controls (0.28l7C) r63], have proven that retinal detachment is more frequent after Vag laser capsulotomy. Therefore, it can be inferred that the laser treatment of the capsule is not free of risk for the myopic eye. For this reason, any medical and surgical measures able to reduce opacification can eventually lower the risk of retinal detachment. The first 3 months following capsulotomy appear to be particularly at risk since 80% of retinal complications have been observed during this period of time. The frequency of retinal detachment in myopic eyes with axial length greater than or equal to 26.5 mm is six times higher than in the emmetropic controls examined in another study by the author [63]. No significant differences were observed in terms of retinal detachment between bag vs sulcus fixation (1.8 vs 2.1%). However, it is worth noting that with regard to the group of patients studied, bag-fixated IOLs decreased the percentage of opacification and therefore also the need for the laser treatment of the capsule (as well as the eventual ARD risk).
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also exerts a positive influence on the maintenance of capsular transparency r58, 64, 69]. In practical terms, this means fewer laser capsulotomies and a significantly lower incidence ofvitreoretinal complications. Also after the opening of the capsule, extracapsular extraction has the advantage of keeping vitreoretinal complications at significantly lower levels [56, 63, 65] compared with intracapsular extraction. We recommend implantation of IOLs with large optics, devoid of holes, longer than 14.0 mm and with anterior loop angulation. This allows a more accurate examination of the retinal periphery and causes greater adherence between the capsule and the IOL, thus inhibiting the formation of Elschnig's pearls [64, 68, 69]. The above measures allow the eye to be in a condition best selected to cope with possible retinal complications. REFERENCES
2 3 4
5 6 7 8
CONCLUSIONS
Retinal detachment is one of the most serious complications of cataract extraction [1,4, 7,20]. Percival [13] recommends that combining extracapsular extraction with the implantation of the posterior capsule can prevent the advancement of the vitreous towards the anterior chamber, thus decreasing the traction of the vitreous onto the retinal regions. Moreover, the IOL can either prevent or delay the need for capsulotomy. According to Percival, intracapsular extraction should be avoided, in particular in myopic eyes. On the basis of our experience, with the exception of rare cases characterized by clear contraindications, we advise the implantation of a posterior chamber IOL, if possible in the capsule bag, accompanied by careful checking and adequate prophylaxis of retinal rhegmatogenous lesions occurring both before and after surgery [29]. Implantation of an IOL not only improves visual rehabilitation, but Eur J Implant Ref Surg, Vol 3, December 1991
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BJ Curtin. Clinical Course In 'The Myopias', Harper Row, Philadelphia, 1985. 1M Borish. Clinical Refraction, 3rd edition. The Professional Press Inc., Chicago, 1970; 90. WS Duke Elder. The PractIce of Refraction, 8th edition. St. Louis, CV Mosby Co., 1965; chap. 5. CL Schepens, BA Marden. Data on the natural history of retinal detachment: further characterization of certain unilateral non traumatic cases. Am. J. Ophthalmol., 1966; 61: 213-266. L Laatikainen, A. Tarkkanen. Proliferative vitreoretinopathy after intraocular lens implantation. Acta Ophthalmol., 1985; 63: 380-382. SW Hyams, M Bialic, E Neumann. Myopia aphakis. Br. J. Ophthalmol., 1975; 59: 480. NS Jaffe, HM Clayman, MS Jaffe. Retinal detachment in myopic eyes after intraocular and extracapsular cataract extraction. Am. J. Ophthalmol., 1984; 97: 48-52. P Coonan, WE Fungh, RG Webster, AWAllen, RL Abbott. The incidence of retinal detachment following extracapsular cataract extraction. A ten year study. Ophthalmology, 1985; 92: 1096. K Naeser, C Kobayashi. Epidemiology of aphakic retinal detachment following intracapsular cataract extraction: a follow up study with an analysis of risk factors. J. Cataract Refract. Surg., 1988; 14: 303-308. T Armstrong, S Lichtenstein. Intraocular lenses in myopes. Ophthalmic Surg., 1984; 15: 653-657. RL Lindstrom, TD Lindquist, J Huldin, J Rubenstein. Retinal detachment in axial myopia following extracapsular cataract surgery. In: Cataracts, Raven Press, New York, 1988; 253-260. DL Praeger. Five years follow-up in the surgical management of cataract in high myopia treated with Kelman phacoemulsification technique. Ophthalmology, 1979; 86: 2024. S Percival. High myopia: new definition and the significance ofIOL implantation. Eur. J. Implant Ref. Surg., 1986; 3: 137. HG Scheie, PH Morse, A Aminlari. Incidence of retinal detachment following cataract extraction. Arch. Ophthalmol., 1973; 89: 293-295. NS Jaffe. Cataract Surgery and its Complications, 4th edition, CV Mosby Co., Lt. Louis, 1984: 637-649. MC Kraff, DR Sanders, HL Lieberman. Total cataract extraction through a 3 mm inCIsion: a report of 650 cases. Ophthalmol. Surg., 1979; 10: 46-54. JC Folk, TC Burton, Bilateral aphakic retinal detachment. Retina, 1983; 3: 1-6.
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18 CL Schepens. Retinal detachment and aphakia. Arch. Ophthalmol., 1951; 45: 1-16. 19 E Malbran, R Dodds. Retinal detachment and aphakia. Ophthalmologlca, 1964; 147: 343-360. 20 MT Ashrafzaden, CL Schepens, II Elzeneiny, R Moura, MF Kraushar. Aphakic and phaklc retinal detachment. Arch. Ophthalmol., 1973; 89: 476-483. 21 HR Bohringer. Statistiches zu Haufigheit und rlslko der netzhautablosung. Ophthalmologica, 1956; 131: 331. 22 BJ Curtin. The Myopias: BasIc SCIence and Clinical Management. Harper Row, Philadelphia, 1985; 277-385; 403-435. 23 ES Perkins. Morbidity from myopia. Sightsau Reu., 1979; 49: 11-9. 24 RK Blach. Degenerative myopia. In: Krill AE, Ed. Krill's Hereditary Retinal and Choroidal Diseases. Vol. 2. Clinical Characterlst!cs. Harper Row, Hagerstown, Maryland, 1977; 911-937. 25 HM Clayman, NS Jaffe, DS Light, MS Jaffe, JC Cassdy. Intraocular lenses, axial lengths, and retinal detachment. Am. J. Ophthalmol., 1981; 92: 778. 26 M Ruben, P Rajpurohit. Distribution of myopia aphakic retinal detachments. Br. J. Ophthalmol., 1976; 60: 517-521. 27 CD Binkhorst. The iridocapsular lens and the iris chip lens in pseudophakia. Trans. Am. Acad. Ophthalmol. Otolaryngol., 1973; 77: 589-597. 28 SPB Percival, V Anand, SK Das. Prevalence of aphakic retinal detachment. Br. J . Ophthalmol., 1983; 67: 43-45. 29 L Buratto. Principi di implantologia. In: 'Chirurgia extracapsulare della cataratta e implanto di lenti intraoculari de camera posteriore. C.A.M.O., Milano, 1987. 30 FI TolentinO, CL Schepens, HM Freeman. V!treoretlnal Disorders, WB Sanders Company, Philadelphia, 1976. 31 WG Everett, FG Hurite, EM Sorr. Retinal detachment following cataract extraction by phacoemulsification. Mod . Probl. Ophthalmol., 1977; 18: 503-507. 32 CP Wilkinson. Retinal detachments following intraocular lens implantation. Ophthalmology, 1981; 81: 410-418. 33 WJ Stark, PW Smith, AG Maumenee, AC Terry. Intraocular lens: complication and visual results. In WJ Stark, AC TErry, AE Maumenee (Eds), Anterior Segment Surgery, WiIhams and Wilkins, Baltimore, 1987; 77-83 . 35 P Kroll, H Busse, P Berg. Complications in aphakic eyes after vitreous loss. Ann. Ophthalmol., 1981; 13: 983. 36 N Jaffe, HM Clayman, MS Jaffe. Cystoid macular oedema after intracapsular and extracapsular cataract extraction with and without an intraocular lens. Ophthalmology, 1982; 89: 25-29. 37 J Worst. Extracapsular surgery in lens implantation. Part 4: Some anatomical and pathophysiological implications. Am. Intraocular Implant. Soc. J ., 1978; 4: 7-13. 38 JL Menezo, FJ Marin, M Harto. Iris and macular angiography in intraocular implants. Am. Intraocular Implant. Soc. J., 1984; 10: 28. 39 P Percival. Clinical factors relating to CME after lens implantation. Ophthalmology, 1978; 85: 190-196. 40 L Moses. CME and retinal detachment following cataract surgery. Am. Intraocular Implant. Soc. J., 1979; 5: 326. 41 RL Winslow, BC Taylor, WS Harris. A one year follow up of CME following intraocular lens implantation. Ophthalmology, 1978; 85: 190-196. 42 JMS McCannell, JF Cullen. Pseudophakic CME with the Severin lens. J. Cataract Refract. Surg., 1986; 12: 499-501. 43 K Miyake, M Asakura, M Kobayashi. Effect of intraocular lens fixation on the blood/aqueous barrier. Am. J. Ophthal mol., 1984; 98: 451-455. 44 R Drews. Results in patients with high and low power intraocular lenses. J. Cataract Refract. Surg., 1986; 12: 155-157. 45 T Ochi, A Gon, Y Kora, K Kawai, V Fukado. Intraocular lens implantation and Hygth myopia. J . Cataract Refract. Surg., 1988; 14: 403-408. 46 CL Schepens, MP Avila, AE Jalkh, CL Trempe et al. The role of the vitreous in CME. Surv. Ophthalmol., 1984; 28: 499-504. 47 J McDonnell, A Patel, R Green. Comparison of intracapsular
48 49 50
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63 64 65 66 67 68 69
and extracapsular cataract surgery. Ophthalmology, 1985; 92: 1208-1223. SPB Percival. Long term complication from extracapsular cataract surgery. Trans. Ophthalmol. Soc. U.K., 1985; 104: 915. DM Fastenherg, PL Schwartz, HW Lim. Retinal detachment following neodymium Vag laser capsulotomy. Am. J. Ophthalmol., 1984; 97: 288. ROber, CP Wilkinson, JV Fiore, JM Maggiano. Rhegmatogenous retinal detachments after Nd:Yag laser capsulotomy in phakic and pseudophakic eyes. Am. J . Ophthalmol., 1986; 101: 81-89. RL Winslow, BC Taylor. Retinal complications following Vag laser capsulotomy. Ophthalmology, 1985; 92: 785. GR Shah, JP Gills, DG Durham, WH Asmus. Three thousand Yag lasers in posterior capsulotomies: an analysis of complicatIon and comparison to polishing and surgical discussion. Ophthalmic Surg., 1986; 17: 473-497. R Kratz. Techning phacoemulslfication in California and 200 cases of phacoemulsification. Current Concepts In Cataract Surgery: Selected Proceedings of the Fourth Biennial Cataract Surgical Congress. C.V. Mosby Co., St. Louis, 1976; 121-123. R Wilhelms, JM Emery. Posterior capsule opacification following phacoemulsification. Ophthalmic Surg., 1980; 11: 264-267. R Frezzotti, A Caporossi, D Impagliatelli, A Morocutt, E Polito, C Slni. Rappresentazione della opacizzazione della capsulare posteriore in 12 anni (72-83) di chirurgia extracapsulare. Bol. Ocul. 1985; 1: 55-67. TJ Liesegang, WM Bourne, DM I1strup. Secondary surgical and neodymium-Vag laser discussions. Am. J. Ophthalmol., 1985; 100:510-519. WAllen, Z Hui Rowg. Extracapsular cataract extraction. Prognosis and complication with and without posterior chamber lens implantation. Ann. Ophthalmol., 1987; 19: 329-333. RL Lindstrom, WS Harris. Management of the posterior capsule following posterior chamber lens implantation. Am. Intraocular Implant Soc. J ., 1980; 6: 255-258. A Anis. The mechanism of post operative posterior capsular opacification and mechanical means of preventing it. In: 'Extracapsular Cataract M!crosurgery and Posterior Chamber Intraocular Lens', Camo, Milan, 1987; 568-572. R FrezzottI, A Caporossi, F Menicacci. Impiego dell'Nd:Yag laser nel trattamento della opacizzazione della capsulare posteriore in presenza di IOL. Boll. Ocul., 1987; 5: 767-774. JL Pearce. Capsular fixated posterior chamber lenses in high myopia. Trans. Ophthalmol. Soc. UK, 1985; 104: 586-587. F Verzella. P.E. and transparent lenses. In: F Verzella, Ed, Atlas of Extracapsular Technique. Phacoemulsification and Intraocular Lenses. Bologna, Italy, Lens Edition 1981 : 98-108. LU Buratto, LE Buratto. Cataratta, miopia assile e compllcazioni vitreo retiniche. Att! Soc. Oftal.ltaliana, 1988; 24-27 Nov: 109-112. 0 Nishi. Incidence of posterior capsule opacification In eye with and without posterior chamber intraocular lenses. J. Cataract Refract. Surg., 1986; 12: 519-522. WJ Stark, D Worthen et al. Neodymium Vag lasers an FDA report. Ophthalmology, 1985; 92: 209-212. AC Terry, WJ Stark, AE Maumenee, W Fafaday. Neodymium-Yag laser for posterior capsulotomy. Am. J. Ophthalmol., 1983; 96: 716. CW Simcoe. An ounce of prevention. In: JM Emery, Ed., Current Concepts !n Cataract Surgery Congress. CW Mosby Co, St. Louis, 1978; 213-221. S Sterling, TO Wood. Effect of intraocular lens convexity on posterior capsule opacification. J . Cataract Refract. Surg., 1986; 12: 655-657. R Sellman Tam, RL Lindstrom. Effect of plano-convex posterior chamber lens on capsular opacification from Elschmg's pearl formation. J. Cataract Refract. Surg., 1988; 14: 68-72.
Eur J Implant Ref Surg, Vol 3, December 1991
High myopia and the complications that follow the extraction of a cataract from a highly myopic eye are described. A comparison between intracapsular and extracapsular techniques is made and the advantages of a posterior chamber IOL are evaluated. Some suggestions for reduction of capsular opacification are given. Precautions to be taken during Nd:Yag laser treatment of the posterior capsule, and vitreoretinal complications are discussed. Keywords: Capsular opacification; Cystoid macular oedema; Extracapsular cataract extraction; High myopia; Posterior chamber IOL; Nd:Yag laser caps ulotomy; Phacoemulsification; Retinal detachment
DEFINITION OF HIGH MYOPIA
Pathological myopia is a refractive defect in which the antero-posterior diameter of the globe is abnormal and in which alterations to various degrees may also occur in the radius of corneal curvature, the power and refraction index of the lens, the sclera, choroid, retina and vitreous [1). Myopia has been defined as negative preoperative refraction values of -6D [2, 31, -8D [4, 51 or -10D [6), by postoperative refraction values of +7D [7,8] or +9D [9], or by considering the power of the implanted intraocular lens (lOL), e.g. + 13 D [101. The current trend for evaluating myopia, however, is based on axial length. Some ophthalmologists define high myopia as axial length equal to or greater than 25.00 mm [10,11], whereas others use different values, such as 27.00mm [12] or 26.5mm [13]. Preoperative refraction is not a precise indicator since it does not exclude myopia oflenticular origin. Moreover, refraction is subject to variations with time and may lack precision due to the poor compliance of the patient or inexact evaluation by the assessor. Postoperative refraction parameters exclude myopias of lenticular nature but do not exclude those myopias that are the result of short corneal radius of curvature. Likewise, the implanted IOL power is not a precise parameter, as lenses have different constants for biometric calculations. Thus the most exact method is the one based on axial length. With a mean value for emmetropic eyes, i.e. a mean keratometry, of 43.40 D and a mean axial length of 23.00 mm, to calculate data for a myopic 0955-3681/91/040271 +08 $03.00/0 © 1991 Ballhere Tindall
eye with a spectacle refraction of -6.00 D, the axial length must be 3.5 mm greater
During cataract surgery, operative strain and postoperative changes, in particular those affecting the vitreous, may place the retina at risk, even in patients that do not belong to a high risk popUlation. Cataract extraction increases the risk of retinal detachment in the normal population; the incidence of retinal detachment following cataract extraction ranges from 0.4 to 3.5% [14-16]. One of the bestknown surveys, involving 5541 eyes submitted to cataract extraction, either by the extracapsular or intracapsular technique, showed an incidence of retinal detachment of 2.2%. The same study reported a greater incidence following ICCE compared with ECCE [141. Folk & Burton [17) emphasized the causative role of lens extraction in the onset of retinal detachment. They observed that in phakic patients with ipsilateral retinal detachment (in the same eye), the risk of retinal detachment in the contralateral phakic eye was low, but increased following cataract extraction. Studies on retinal detachment have reported an incidence in aphakic eyes ranging from 10.1% to 33.0% [18-201. Eur J Implant Ref Surg, Vo/3, December 1991
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Bohringer claimed that the risk of developing retinal detachment in patients older than 60 years with myopia greater than 5 D amounted to 2.4ift compared with 0.06fk in emmetropic patients of the same age group [211; this can be directly ascribed to the vitreoretinal characteristics of the highly myopic eye. Curtin reported that retinal detachment occurred in phakic non-myopic individuals with a frequency of between 0.005 and 0.010
In the case of myopic eyes, as well as for emmetropic eyes, intracapsular extraction, planned extracapsular extraction, and phacoemulsification with or without IOL implantation are the procedures performed most frequently. The various techniques are evaluated in relation to intraoperative and postoperative complications, the implantation of an IOL and recovery of correct visual function. Intracapsular Extraction (ICCE)
This technique, which has been abandoned by most surgeons, has always posed significant postoperative problems, the most important of which is retinal detachment (RD) [7, 25J. Literature data show that the incidence of RD in high myopia ranges from 5l'k [251 to 40% [3, 26J. However, the differing definitions of high myopia of the various authors partially accounts for this difference. In 1976 Ruben carried out an interesting research project on 944 eyes with different degrees of myopia,
submitted to ICCE /26]. According to his study, the rate ofRD varied depending on the refractive defect, i.e. 3.5Ck in myopias between 0 and -4 D, 4.3% in myopias between -4 and -8 D and 40% in myopias between -10 and -20D. However, Naeser and colleagues ascribed more significance to the relatively younger age of the myopic patients submitted to intracapsular cataract extraction. They reported a high incidence of RD (22.2fk) in myopic patients operated on aged under 70 years, and a frequency of 01)( in emmetropic or hypermetropic eyes of patients aged 70 or more at the time of the operation. In 1975 Hyams had already observed a greater incidence of RD in younger myopic patients and he hypothesized that the sudden detachment of the vitreous, following ICCE, a rare event in young phakic patients, may be the cause of the high RD rate. Extracapsular Extraction (ECCE)
The move from intracapsular to extracapsular surgery, in the mid 1970s, can be attributed to the improvement in stability of the Binkhorst lens that was being used at the time, and the possibility of preventing vitreoretinal complications due both to ICCE and the IOL [27, 28J. It soon became apparent that the maintenance of an intact posterior capsule could decrease the incidence of intraoperative and postoperative complications. For this reason, ECCE was immediately adopted by most surgeons, also for highly myopic cases, either with or without the implantation of an IOL and it is now the technique of choice for operations on senile and presenile cataracts not associated with serious ocular pathologies. ECCE provides significant positive results both during surgery and in the postoperative period, as well as in terms of functional recovery in the short and long term [29]. ECCE is most suitable for the peculiar anatomy of the myopic globe, and is characterized by lower intraoperative risk and fewer postoperative vitreoretinal complications than ICCE [7, 8, 131. In this respect it is worth quoting the study carried out by Jaffe [7J on two consecutive series of cataract extractions in myopic patients, the first of 122 intracapsular extractions and the second of 151 extracapsular extractions. Eyes that suffered intraoperative vitreous loss were excluded from the study. The incidence of RD was constantly lower in the group of patients submitted to extracapsular extraction: 0.66% vs 5.7% in ICCE. In his comparative study, Percival reported an ARD incidence (retinal detachment in the aphakic patient) of ll.lift in Eur J Implant Ref Surg, Vol 3, December 1991
Cataract Surgery in High Myopia
myopic eyes following ICCE without IOL implantation, and 2.2% after ECCE and posterior chamber IOL implantation [28].
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with an incidence of 7% in those patients whose capsule was still intact [41]. McCannell et al. noted the presence of iritis in 61 % of CMO cases observed following ICCE and implantation of an IOL of the Severin type l42]. Intraoperative Complications Miyake l43] demonstrated, by means offluorophotometry, that the breakdown of the blood-aqueous Vitreous loss is the main intraoperative problem barrier, i.e. at the origin of CMO, is greater after during cataract surgery in the emmetropic and, in ICCE and anterior chamber IOL implantation than particular, in the strongly myopic eye. Vitreous loss after ECCE with posterior chamber intraocular lens predisposes to retinal detachment since the capsular implantation. He demonstrated that the best results barrier is no longer intact and there is a high risk of are achieved with capsular fixation. the vitreous strand becoming incarcerated in the Fortunately, CMO is quite a rare occurrence in surgical wound l30]. Literature data show that myopic eyes, even in those that have suffered vitreous loss is a frequent intraoperative compli- vitreous loss. In a follow-up of 36 myopic eyes subcation [8, 31, 33]. Moreover, many authors have mitted to ECCE and IOL implantation Drews associated vitreous loss with RD. Hughes & Awens observed no cases of CMO, even in those that had [34] reported vitreous loss in 13 of20 cases of retinal suffered vitreous loss [44]. Similarly Armstrong [101 detachment (43%) while Schepens observed vitreous observed no cases ofCMO in 40 myopic eyes submitloss in eight out of 72 cases of retinal detachment ted to ECCE and IOL implantation. Ochi et al. [45] following ICCE (11 %) [18]. Krall and colleagues l34] reported an isolated case of CMO in 183 cataract found an incidence of myopia of 14% in 114 cases of extractions from globes with axial length >27 mm. vitreous loss, a condition that is more frequently The one case had suffered intraoperative vitreous associated with this complication (Table 4). Accord- loss and had been implanted with an anterior ing to the studies published by Krall et al. [34], the chamber IOL. incidence of retinal detachment increased to 17% Schepens et al. [46] studied the adherence of the following vitreous loss, compared with cases that vitreous in the macular area by dynamic inspection were free of the complication. by EI Bayadikajiura lens. They claim that CMO can be observed in cases in which the vitreous is completely liquid and the hyaloid is fully detached from Cystoid Macular Oedema (CMO) the posterior retina, a common condition in aphakic myopic eyes, and in eyes with Wagner syndrome. CMO is a classical complication that may be caused by the type of operation, the intraoperative complications, the implant or by a possible initial refracPostoperative Complications tive error 136]. Worst [37] put forward the hypothesis that CMO Literature data on the incidence of RD in myopic results from two pathogenic mechanisms: (1) the eyes submitted to ECCE fall into two categories: (1) exchange of substances between the anterior and patients with intact posterior capsule, and (2) the posterior segments and (2) the traction of the patients submitted to either capsulotomy or laser vitreous onto the macula. He reported a lower incitreatment. dence of CMO following ECCE than after ICCE. The absence of compartmentalization between the an- Patients with intact capsule. If the posterior capsule terior and the posterior segments is responsible for is intact, the movement of the vitreous towards the the complication [38-40]. anterior chamber is inhibited, the loss of hyaluronic Jaffe and colleagues claimed that the incidence of acid is reduced, the incidence of anterior hyaloid CMO is generally low in both ICCE and ECCE, rupture is lower, vitreous tractions are decreased and posterior vitreous detachments occur with when surgery is devoid of complications [36]. Intraoperative vitreous loss and chronic post- reduced frequency 1291. operative iritis can considerably increase the freIn his study on the incidence of posterior vitreous detachment in post-mortem eyes submitted to extraquency ofCMO l301. Winslow and colleagues observed a significant capsular cataract extraction, McDonnel [471 increase in CMO when intraoperative capsulotomy reported a significantly lower rate (40%) in eyes was performed, and in the case of vitreous loss; 12 with intact capsule, compared with those that had months after surgery 38% of the cases had developed undergone primary or secondary capsulotomy (869C lCMO, as determined by fluorangiography, compared It is generally accepted that, when the capsule is cur J Implant Ref Surg. Vol 3. December 1991
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intact, this results in fewer vitreoretinal complications, both in the population in general and in myopic patients [7, 8, 14, 301. Literature data give incidences of 1.1 % r28], 0.7% [7], 2.85% [12], 0.8% r8] and 0% [44]. Since myopia, followed by aphakia, is the most significant risk factor with regard to the onset of retinal detachment, an intact capsule certainly results in fewer complications.
Patients with caps ulotomy. Capsulotomy, a procedure that is often necessary some time after ECCE, partially thwarts the efficacy of primary surgery in terms of vitreoretinal complications. Although technical problems have been solved with the introduction of the Nd:Yag laser, which permits fine control by the surgeon, the clinical complications arising from the absence of a barrier between the two ocular compartments have not yet been resolved. The open capsule increases the risk of aphakic or pseudoaphakic retinal detachment, in particular in myopic patients r48]. Coonan observed an increase in RD from 0.8% to 2.75% r8], following Nd:Yag capsulotomy, while Percival reported a rise in RD from 1.1 % with intact capsule to to 5.5% following Yag laser capsulotomy r28] and many other cases have been mentioned in the literature [49, 50]. Fastemberg et al. described five cases of rhegmatogenous detachment occurring within one month after Vag laser capsulotomy; however, they did not specify the frequency rate on the total number of cases treated [49]. Winslow & Taylor r5l] recently reported on 18 cases of retinal complications after Vag laser capsulotomy and ten retinal detachments. They concluded that retinal complications were due either to the rupture of the capsule or to related vitreous movements, thus excluding a specific link with the Nd:Yag laser. In contrast, Praeger's case study [12] did not highlight any difference between patients submitted to Vag laser capsulotomy and controls. However, since most authors agree that Vag laser cap.sulotomy. is not immune to vitreoretinal complicatIOns, speCIal care must be taken with higher risk ~oups, i.e. ~ccording to Shah's classification [52], hI~hly myopIC patients, individuals with a history of retI.nal detachment in the adelphous eye, and patIents with peripheral rhegmatogenous degeneration. Therefore, the problem has now shifted to the frequency of posterior capsule opacification, the means available to curb opacification and the parameters of a less dangerous procedure of capsulotomy.
Posterior Capsule Opacification
The data on the incidence of secondary cataract vary in the literature, depending on the refracting defect the possible presence of an IOL and the follow-u~ period. It is worth underlining that ECCE recommended for .axial myopias shows the highest incidence ofpostenor capsule opacification requiring laser treatment: mean values range between 45% and 60%. Pathogenesis of such a phenomenon may be related to the younger age of these patients, characterized by more active proliferative opacification of the residual epithelium and stronger capsular retraction. It is generally agreed that the incidence of posterior capsule opacification is lower following the implantation of a posterior chamber IOL. Percival [48] reported a decrease in opacification from 45% (ECCE) to 9% (ECCE + IOL) during a 3year follow-up period and Liesegang et al. [56] observed a 22.1 % incidence of opacification following ECCE without implantation vs 9.1% in ECCE with posterior chamber IOL during a follow-up period of2 ye~rs. Nishi reported a decrease in capsular opacificatIOn, caused by the implantation of a posterior chamber IOL (15% vs 7.1%). All the authors mentioned above recommended the implantation of a posterior chamber IOL, after careful calculation, in the myopic eye. Posterior chamber IOLs do not directly influence the ~isk of retinal detachment. However, they may partIally prevent the opacification of the posterior capsule and the related risk of laser treatment. According to Stark [65], Vag laser capsulotomy causes associated interruption of the anterior hyaloid surface. This phenomenon increases the vitreoretinal risk. The presence of a posterior chamber IOL dams the movements of the vitreous towards the anterior chamber after Vag laser capsulotomy. Terry.et al. [66] reported six cases of vitreous prolapse mto the anterior chamber out of 19 aphakic patients, following Vag laser capsulotomy, and no cas~s of vitreous prolapse out of 30 pseudophakic patIents. Type of IOL and Capsular Opacification
The ~esign of the posterior chamber lens plays a very Important role in the reduction of the incidence of capsular opacification and its development over time. According to recent studies two processes can lead to capsular opacification following ECCE [64]. The first is the transformation of epithelial cells into myofibroblasts that contract and cause the formation of numerous microfolds and small puckers endEur J Implant Ref Surg. Vol 3. December 1991
Cataract Surgery in High Myopia
ing in the clinical onset of capsular fibrosis. The second process is the migration and proliferation of epithelial cells on the posterior capsule, with the formation of Elschnig's pearls. The effect ofIOL design on the above mechanisms is still the object of controversy. However, it has been ascertained that the two phenomena occur less frequently after the implantation of an IOL. At present, lenses with posteriorly convex optics are attracting attention. Simcoe [67] showed that the adherence of the posterior capsule to the posterior lens surface inhibited the migration of the epithelial cells, thus preventing the formation of Elschnig's pearls. Lindstrom & Harris [581 claimed that the posterior convexity of the lens caused better adhesion between the capsule and the posterior lens surface in general, thus exerting a barrier effect against the formation of Elschnig's pearls. In contrast, Sterlin [68] reported a higher incidence of capsular fibrosis with posteriorly convex lenses. In-vitro studies have confirmed the tendency of the lenticular epithelium to develop metaplasia of the myofibroblasts, stimulated by the close contact between the capsule and the posterior IOL surface. The lens type most suitable to prevent or decrease the size and frequency of pearls and capsular fibrosis is still a controversial matter. However, it appears certain that lenses with a posterior plano-convex surface, continuous laser ridge lenses, and meniscus-type lenses show the best performance, provided that close contact between the capsule and the optic disk or betwe~n the capsule and the space maintainer is effectively maintained. Experience with highly myopic patients indicates that it is advisable to choose a lens which has a 6.57.0mm large optic, is 14-15mm long for sulcus fixation, single piece, posteriorly convex and has loops with an angle of at least 15°. An implant of this type guarantees that the ratio between the size of the globe and the size of the IOL will reflect the true dimensions of the myopic eye, resulting in greater stability and better vitreous support; the large optic promotes contact between the posterior IOL surface and the posterior capsule. The convex posterior surface facilitates the attachment of the posterior capsule to the whole optic making the exploration of the fundus easier (in this respect it is advisable to implant lenses without positioning holes), also due to the effect of the large optic. Better optic centering on the pupillary region can also be achieved. The total IOL length is also a significant parameter in the case of myopic patients. Usually, the diameter of the sulcus approximately corresponds with the corneal diameter from white to white. In the highly myopic patient this ratio is Eur J Implant Ref Surg. Vol 3. December 1991
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more or less constant. However, absolute values increase due to the oversize typical of this type of eye. Regular measurements of the corneal diameter have demonstrated that in the case of high myopia it is advisable to implant a 14.0-15.0 mm lens if ciliary sulcus fixation has been planned. If the lens seems to be too small, it is necessary to choose bag fixation. Standard size lenses can be implanted inthe-bag. PERSONAL CASE STUDY
A group of 242 myopic patients-a total of 359 eyes-of age ranging from 35 to 89, axial length greater than or equal to 26.5 mm at A-scan ultrasonography, submitted to extracapsular cataract extraction, was considered. The mean follow-up period was 36 months (minimum 18 months and maximum 60 months). Extracapsular cataract extraction was performed by means of phacoemulsification on the pupillary plane and at posterior chamber level in 95% of cases (341 eyes), and by planned extracapsular extraction methods with automated II A in 5% of the cases (18 eyes). All operations were carried out by the same surgeon. The patients studied were divided into two groups to allow a schematic classification, and the second group was further subdivided: 203 eyes without IOL. (2) 156 with posterior chamber IOL. (2a) 109 eyes with sulcus fixation. (2b) 47 eyes with capsular fixation.
(1)
One hundred and fifty-six IOLs were implanted, of which 11 had negative dioptric power, three had zero power and 142 had positive power (from + 1 to + 12.00). No IOLs were implanted in 203 eyes for the following reasons: (1) the IOL was deemed to be unnecessary for optical reasons (at the beginning of the study); (2) previous cataract surgery had occurred without IOL in the fellow eye; (3) IOL implantation was refused by the patient. The study covered a mean follow-up period of 36 months during which the following parameters were evaluated: (1) incidence of posterior capsule opacification in the non-implanted eyes and in the eyes with IOL, also with regard to sulcus vs bag fixation; (2) incidence of retinal detachment of the postoperative course before and after possible Nd:Yag laser capsulotomy. Capsulotomy was always performed by means of the Microruptor II by Lasag, on 'fundamental mode', with energy equal to 1.21.4 mJ, three bursts, a number of spots varying from
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4 to 25 and the use of a CGP 1.2 contact lens. The treatment was always implemented by the same ophthalmologist and consisted of capsular openings of variable width (from 3 to 4 mm). Capsulotomy never exceeded the limit of the optic. In this study, an attempt to evaluate the safest procedure to reduce vitreoretinal complications through a statistical analysis of the operated eyes with and without posterior chamber artificial lenses was undertaken. Moreover, the incidence of capsular opacification was studied in the eyes without IOL and in the eyes with IOL, as well as the frequency of retinal detachment in the postoperative period prior to Yag laser treatment and following Nd:Yag laser capsulotomy.
RESULTS
capsular opacification occurred in 119 eyes (33.1%) of the cases after 21 months on average. Retinal Detachment
Patients without an 10L. No retinal detachments were observed in the postoperative period prior to possible Yag laser capsulotomy. Three retinal detachments occurred following Yag laser capsulotomy (1.4%) (Table 3). Table 3
Retinal opacification in myopic patients Retznal detachment Postyag No. Preyag IOL 0 3 No 203 1 2 156 Sulcus + Bag Total 359 1 5
(If
1.4 1.9
Patients with an 10L. One retinal detachment was observed in the eyes with posterior chamber IOLs, Capsular opacification was observed in 154 out of prior to Yag laser treatment (11156,0.64%). Retinal 359 eyes (42.9%). detachment occurred in two eyes following Yag laser capsulotomy (2/156, 1.28%) (Table 3). No compliPatients without an 10L. In the myopic eyes without cations were observed in the 109 eyes with sulcusIOL (203 eyes) posterior capsule opacification fixated IOL prior to laser treatment. requiring Nd:Yag laser capsulotomy accounted for Following capsulotomy, two eyes suffered retinal 59.6% of the cases (121 eyes) (Table 1). Opacification detachment during the first 3 months after treatoccurred, on average, after 1 year. ment (2/109, 1.8%) (Table 4). Only one of the 47 eyes Capsular Opacification
Table 1 Capsular opacification in myopic patients Capsular opacificatIOn No. Yes IOL No No 203 121 82 122 156 34 Sulcus + Bag Total 359 155 204
Iff.
59.6 21.8
Patients with an 10L. Capsular opacification was observed in 34 out of 156 eyes, 21.8% of the eyes with a posterior chamber IOL (Table 2). Table 2 Capsular opacification in myopic patients IOLs Capsular opacificatIOn Yes No IOL No. 27 82 Sulcus 109 Bag 47 7 40 Total 156 34 122
with
'lr
24.8 14.9
Capsular opacification developed in 27 out of 109 eyes with sulcus fixation (24.8lj() during a mean period of 17 months; 14.9% of the 47 eyes with capsular bag fixation suffered from opacification (seven eyes) during a mean period of 19 months. In a nonmyopic control group that had been previously studied (359 eyes with posterior chamber IOL, of which 272 in the sulcus and 87 in the capsular bag)
Table 4 Retinal detachment in myopic patients Retznal detachment Post yag IOL No. Pre yag 2 Sulcus 109 0 1 0 Bag 47 Total 2 156 1
'if
1.8 2.1
with capsular bag fixation suffered retinal detachment without laser treatment (2.1 %). In the remaining follow-up period, and also following laser capsulotomy, no complications ensued.
REMARKS Some significant considerations can be made on analysis of the results. In terms of posterior capsule opacifications we have observed the following. Myopic non-implanted eyes suffer more capsular opacification than eyes with posterior chamber IOLs. On average, 59.6% of the non-implanted eyes (1211203) required laser capsulotomy 12 months after surgery. Opacification occurred in 21.8% of the implanted eyes (34/156) after a longer period of time (18 months). The presence of an intraocular lens retards capsuEur J Implant Ref Surg. Vol 3. December 1991
Cataract Surgery In High Myopia
lar opacification in myopic patients (12 months without an IOL vs 18 months with an IOU. Among the implanted eyes, those with bag fixation show a lower rate of capsular opacification compared to sulcus fixation. Only 14% of them (7/47) required Yag laser capsulotomy after a longer period of time (19 months with bag fixation vs 17 months with sulcus fixation) but this result is not statistically significant. Both the group without IOLs (1.4%) and the implanted group (1.9%), as well as controls (0.28l7C) r63], have proven that retinal detachment is more frequent after Vag laser capsulotomy. Therefore, it can be inferred that the laser treatment of the capsule is not free of risk for the myopic eye. For this reason, any medical and surgical measures able to reduce opacification can eventually lower the risk of retinal detachment. The first 3 months following capsulotomy appear to be particularly at risk since 80% of retinal complications have been observed during this period of time. The frequency of retinal detachment in myopic eyes with axial length greater than or equal to 26.5 mm is six times higher than in the emmetropic controls examined in another study by the author [63]. No significant differences were observed in terms of retinal detachment between bag vs sulcus fixation (1.8 vs 2.1%). However, it is worth noting that with regard to the group of patients studied, bag-fixated IOLs decreased the percentage of opacification and therefore also the need for the laser treatment of the capsule (as well as the eventual ARD risk).
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also exerts a positive influence on the maintenance of capsular transparency r58, 64, 69]. In practical terms, this means fewer laser capsulotomies and a significantly lower incidence ofvitreoretinal complications. Also after the opening of the capsule, extracapsular extraction has the advantage of keeping vitreoretinal complications at significantly lower levels [56, 63, 65] compared with intracapsular extraction. We recommend implantation of IOLs with large optics, devoid of holes, longer than 14.0 mm and with anterior loop angulation. This allows a more accurate examination of the retinal periphery and causes greater adherence between the capsule and the IOL, thus inhibiting the formation of Elschnig's pearls [64, 68, 69]. The above measures allow the eye to be in a condition best selected to cope with possible retinal complications. REFERENCES
2 3 4
5 6 7 8
CONCLUSIONS
Retinal detachment is one of the most serious complications of cataract extraction [1,4, 7,20]. Percival [13] recommends that combining extracapsular extraction with the implantation of the posterior capsule can prevent the advancement of the vitreous towards the anterior chamber, thus decreasing the traction of the vitreous onto the retinal regions. Moreover, the IOL can either prevent or delay the need for capsulotomy. According to Percival, intracapsular extraction should be avoided, in particular in myopic eyes. On the basis of our experience, with the exception of rare cases characterized by clear contraindications, we advise the implantation of a posterior chamber IOL, if possible in the capsule bag, accompanied by careful checking and adequate prophylaxis of retinal rhegmatogenous lesions occurring both before and after surgery [29]. Implantation of an IOL not only improves visual rehabilitation, but Eur J Implant Ref Surg, Vol 3, December 1991
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12 13 14 15 16 17
BJ Curtin. Clinical Course In 'The Myopias', Harper Row, Philadelphia, 1985. 1M Borish. Clinical Refraction, 3rd edition. The Professional Press Inc., Chicago, 1970; 90. WS Duke Elder. The PractIce of Refraction, 8th edition. St. Louis, CV Mosby Co., 1965; chap. 5. CL Schepens, BA Marden. Data on the natural history of retinal detachment: further characterization of certain unilateral non traumatic cases. Am. J. Ophthalmol., 1966; 61: 213-266. L Laatikainen, A. Tarkkanen. Proliferative vitreoretinopathy after intraocular lens implantation. Acta Ophthalmol., 1985; 63: 380-382. SW Hyams, M Bialic, E Neumann. Myopia aphakis. Br. J. Ophthalmol., 1975; 59: 480. NS Jaffe, HM Clayman, MS Jaffe. Retinal detachment in myopic eyes after intraocular and extracapsular cataract extraction. Am. J. Ophthalmol., 1984; 97: 48-52. P Coonan, WE Fungh, RG Webster, AWAllen, RL Abbott. The incidence of retinal detachment following extracapsular cataract extraction. A ten year study. Ophthalmology, 1985; 92: 1096. K Naeser, C Kobayashi. Epidemiology of aphakic retinal detachment following intracapsular cataract extraction: a follow up study with an analysis of risk factors. J. Cataract Refract. Surg., 1988; 14: 303-308. T Armstrong, S Lichtenstein. Intraocular lenses in myopes. Ophthalmic Surg., 1984; 15: 653-657. RL Lindstrom, TD Lindquist, J Huldin, J Rubenstein. Retinal detachment in axial myopia following extracapsular cataract surgery. In: Cataracts, Raven Press, New York, 1988; 253-260. DL Praeger. Five years follow-up in the surgical management of cataract in high myopia treated with Kelman phacoemulsification technique. Ophthalmology, 1979; 86: 2024. S Percival. High myopia: new definition and the significance ofIOL implantation. Eur. J. Implant Ref. Surg., 1986; 3: 137. HG Scheie, PH Morse, A Aminlari. Incidence of retinal detachment following cataract extraction. Arch. Ophthalmol., 1973; 89: 293-295. NS Jaffe. Cataract Surgery and its Complications, 4th edition, CV Mosby Co., Lt. Louis, 1984: 637-649. MC Kraff, DR Sanders, HL Lieberman. Total cataract extraction through a 3 mm inCIsion: a report of 650 cases. Ophthalmol. Surg., 1979; 10: 46-54. JC Folk, TC Burton, Bilateral aphakic retinal detachment. Retina, 1983; 3: 1-6.
L. Buratto
278
18 CL Schepens. Retinal detachment and aphakia. Arch. Ophthalmol., 1951; 45: 1-16. 19 E Malbran, R Dodds. Retinal detachment and aphakia. Ophthalmologlca, 1964; 147: 343-360. 20 MT Ashrafzaden, CL Schepens, II Elzeneiny, R Moura, MF Kraushar. Aphakic and phaklc retinal detachment. Arch. Ophthalmol., 1973; 89: 476-483. 21 HR Bohringer. Statistiches zu Haufigheit und rlslko der netzhautablosung. Ophthalmologica, 1956; 131: 331. 22 BJ Curtin. The Myopias: BasIc SCIence and Clinical Management. Harper Row, Philadelphia, 1985; 277-385; 403-435. 23 ES Perkins. Morbidity from myopia. Sightsau Reu., 1979; 49: 11-9. 24 RK Blach. Degenerative myopia. In: Krill AE, Ed. Krill's Hereditary Retinal and Choroidal Diseases. Vol. 2. Clinical Characterlst!cs. Harper Row, Hagerstown, Maryland, 1977; 911-937. 25 HM Clayman, NS Jaffe, DS Light, MS Jaffe, JC Cassdy. Intraocular lenses, axial lengths, and retinal detachment. Am. J. Ophthalmol., 1981; 92: 778. 26 M Ruben, P Rajpurohit. Distribution of myopia aphakic retinal detachments. Br. J. Ophthalmol., 1976; 60: 517-521. 27 CD Binkhorst. The iridocapsular lens and the iris chip lens in pseudophakia. Trans. Am. Acad. Ophthalmol. Otolaryngol., 1973; 77: 589-597. 28 SPB Percival, V Anand, SK Das. Prevalence of aphakic retinal detachment. Br. J . Ophthalmol., 1983; 67: 43-45. 29 L Buratto. Principi di implantologia. In: 'Chirurgia extracapsulare della cataratta e implanto di lenti intraoculari de camera posteriore. C.A.M.O., Milano, 1987. 30 FI TolentinO, CL Schepens, HM Freeman. V!treoretlnal Disorders, WB Sanders Company, Philadelphia, 1976. 31 WG Everett, FG Hurite, EM Sorr. Retinal detachment following cataract extraction by phacoemulsification. Mod . Probl. Ophthalmol., 1977; 18: 503-507. 32 CP Wilkinson. Retinal detachments following intraocular lens implantation. Ophthalmology, 1981; 81: 410-418. 33 WJ Stark, PW Smith, AG Maumenee, AC Terry. Intraocular lens: complication and visual results. In WJ Stark, AC TErry, AE Maumenee (Eds), Anterior Segment Surgery, WiIhams and Wilkins, Baltimore, 1987; 77-83 . 35 P Kroll, H Busse, P Berg. Complications in aphakic eyes after vitreous loss. Ann. Ophthalmol., 1981; 13: 983. 36 N Jaffe, HM Clayman, MS Jaffe. Cystoid macular oedema after intracapsular and extracapsular cataract extraction with and without an intraocular lens. Ophthalmology, 1982; 89: 25-29. 37 J Worst. Extracapsular surgery in lens implantation. Part 4: Some anatomical and pathophysiological implications. Am. Intraocular Implant. Soc. J ., 1978; 4: 7-13. 38 JL Menezo, FJ Marin, M Harto. Iris and macular angiography in intraocular implants. Am. Intraocular Implant. Soc. J., 1984; 10: 28. 39 P Percival. Clinical factors relating to CME after lens implantation. Ophthalmology, 1978; 85: 190-196. 40 L Moses. CME and retinal detachment following cataract surgery. Am. Intraocular Implant. Soc. J., 1979; 5: 326. 41 RL Winslow, BC Taylor, WS Harris. A one year follow up of CME following intraocular lens implantation. Ophthalmology, 1978; 85: 190-196. 42 JMS McCannell, JF Cullen. Pseudophakic CME with the Severin lens. J. Cataract Refract. Surg., 1986; 12: 499-501. 43 K Miyake, M Asakura, M Kobayashi. Effect of intraocular lens fixation on the blood/aqueous barrier. Am. J. Ophthal mol., 1984; 98: 451-455. 44 R Drews. Results in patients with high and low power intraocular lenses. J. Cataract Refract. Surg., 1986; 12: 155-157. 45 T Ochi, A Gon, Y Kora, K Kawai, V Fukado. Intraocular lens implantation and Hygth myopia. J . Cataract Refract. Surg., 1988; 14: 403-408. 46 CL Schepens, MP Avila, AE Jalkh, CL Trempe et al. The role of the vitreous in CME. Surv. Ophthalmol., 1984; 28: 499-504. 47 J McDonnell, A Patel, R Green. Comparison of intracapsular
48 49 50
51 52
53
54 55
56 57
58 59
60 61 62
63 64 65 66 67 68 69
and extracapsular cataract surgery. Ophthalmology, 1985; 92: 1208-1223. SPB Percival. Long term complication from extracapsular cataract surgery. Trans. Ophthalmol. Soc. U.K., 1985; 104: 915. DM Fastenherg, PL Schwartz, HW Lim. Retinal detachment following neodymium Vag laser capsulotomy. Am. J. Ophthalmol., 1984; 97: 288. ROber, CP Wilkinson, JV Fiore, JM Maggiano. Rhegmatogenous retinal detachments after Nd:Yag laser capsulotomy in phakic and pseudophakic eyes. Am. J . Ophthalmol., 1986; 101: 81-89. RL Winslow, BC Taylor. Retinal complications following Vag laser capsulotomy. Ophthalmology, 1985; 92: 785. GR Shah, JP Gills, DG Durham, WH Asmus. Three thousand Yag lasers in posterior capsulotomies: an analysis of complicatIon and comparison to polishing and surgical discussion. Ophthalmic Surg., 1986; 17: 473-497. R Kratz. Techning phacoemulslfication in California and 200 cases of phacoemulsification. Current Concepts In Cataract Surgery: Selected Proceedings of the Fourth Biennial Cataract Surgical Congress. C.V. Mosby Co., St. Louis, 1976; 121-123. R Wilhelms, JM Emery. Posterior capsule opacification following phacoemulsification. Ophthalmic Surg., 1980; 11: 264-267. R Frezzotti, A Caporossi, D Impagliatelli, A Morocutt, E Polito, C Slni. Rappresentazione della opacizzazione della capsulare posteriore in 12 anni (72-83) di chirurgia extracapsulare. Bol. Ocul. 1985; 1: 55-67. TJ Liesegang, WM Bourne, DM I1strup. Secondary surgical and neodymium-Vag laser discussions. Am. J. Ophthalmol., 1985; 100:510-519. WAllen, Z Hui Rowg. Extracapsular cataract extraction. Prognosis and complication with and without posterior chamber lens implantation. Ann. Ophthalmol., 1987; 19: 329-333. RL Lindstrom, WS Harris. Management of the posterior capsule following posterior chamber lens implantation. Am. Intraocular Implant Soc. J ., 1980; 6: 255-258. A Anis. The mechanism of post operative posterior capsular opacification and mechanical means of preventing it. In: 'Extracapsular Cataract M!crosurgery and Posterior Chamber Intraocular Lens', Camo, Milan, 1987; 568-572. R FrezzottI, A Caporossi, F Menicacci. Impiego dell'Nd:Yag laser nel trattamento della opacizzazione della capsulare posteriore in presenza di IOL. Boll. Ocul., 1987; 5: 767-774. JL Pearce. Capsular fixated posterior chamber lenses in high myopia. Trans. Ophthalmol. Soc. UK, 1985; 104: 586-587. F Verzella. P.E. and transparent lenses. In: F Verzella, Ed, Atlas of Extracapsular Technique. Phacoemulsification and Intraocular Lenses. Bologna, Italy, Lens Edition 1981 : 98-108. LU Buratto, LE Buratto. Cataratta, miopia assile e compllcazioni vitreo retiniche. Att! Soc. Oftal.ltaliana, 1988; 24-27 Nov: 109-112. 0 Nishi. Incidence of posterior capsule opacification In eye with and without posterior chamber intraocular lenses. J. Cataract Refract. Surg., 1986; 12: 519-522. WJ Stark, D Worthen et al. Neodymium Vag lasers an FDA report. Ophthalmology, 1985; 92: 209-212. AC Terry, WJ Stark, AE Maumenee, W Fafaday. Neodymium-Yag laser for posterior capsulotomy. Am. J. Ophthalmol., 1983; 96: 716. CW Simcoe. An ounce of prevention. In: JM Emery, Ed., Current Concepts !n Cataract Surgery Congress. CW Mosby Co, St. Louis, 1978; 213-221. S Sterling, TO Wood. Effect of intraocular lens convexity on posterior capsule opacification. J . Cataract Refract. Surg., 1986; 12: 655-657. R Sellman Tam, RL Lindstrom. Effect of plano-convex posterior chamber lens on capsular opacification from Elschmg's pearl formation. J. Cataract Refract. Surg., 1988; 14: 68-72.
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