Phakic anterior chamber lenses for the correction of myopia

Phakic Anterior Chamber Lenses for the Correction of Myopia A 7-year Cumulative Analysis of Complications in 263 Cases Jorge L. Alio´, MD, PhD,1,2 Fernando de la Hoz, MD,1 Juan J. Pe´rez–Santonja, MD, PhD,1 Jose´ Ma Ruiz–Moreno, MD, PhD,1,2 Jose´ A. Quesada, PhD1 Objective: To perform a prospective, clinical trial to determine the potential cumulative complications of patients implanted with angle-supported phakic intraocular lenses (PIOLs) for the correction of myopia. Design: Nonrandomized, prospective, comparative trial. Participants: Two hundred sixty-three eyes of 160 consecutive patients were included. Intervention: Angle-supported anterior chamber intraocular lenses were implanted into phakic eyes. Main Outcome Measures: Night halos and glare were recorded. Central endothelial cell count, postoperative inflammation, applanation tonometry, cataract development, retinal detachment, and pupil ovalization were recorded by the same physician. Results: Night halos and glare were reported as significant by 20.2% at 1 year and 10% at year 7 of follow-up. This complication was significantly lower in the larger optical zone PIOL (ZSAL-4) than in the ZB5M/ZB5MF group (P ⬍ 0.05). Acute postoperative iritis was observed in 4.56% of cases. High intraocular pressure that required antiglaucoma medications appeared in 7.2% of cases. Central corneal endothelial cell density was significantly decreased at postoperative month 3 (P ⬍ 0.0001). The percentages of cell loss were 3.76% at month 3 and 1.83% at year 1, and then the percentages decreased by 1.37% more at year 2, 0.72% at year 3, 0.3% at year 4, 0.6% at year 5, 0.4% at year 6, and 0.56% at year 7. The total cumulative loss of central endothelial cells after 7 years was 8.37%. Pupil ovalization was present in 5.9% of cases, although smaller degrees of this complication were observed in another 10.3%. Retinal detachment appeared in 3% of cases. The PIOL explantation was decided in 11 cases (4.18%) because of cataract development (9 cases) and extreme pupil ovalization associated with severe glare (2 cases). The Kaplan–Meier cumulative survival analysis study showed an expected period free from complication of 86.5% for IOP elevation, 98.75% for endothelial cell count inferior to 1500 cells/mm2, 86.97% for pupil ovalization, 95.43% for retinal detachment, and 89.02% for explantation. Conclusions: Angle-supported PIOL appeared to be well tolerated by the corneal endothelium with a low rate of other complications. Pupil ovalization seemed to be a specific problem for this type of PIOL. Ophthalmology 1999;106:458 – 466 The surgical correction of myopia with an intraocular lens (IOL) implanted in the phakic eye has been a controversial issue in the past decades. The invasive character of the procedure and a history of severe complications have limited their application until recently. Despite previous controversies, this procedure offers well-defined advantages as a refractive surgical technique because of its simplicity, potential reversibility, precision, and the stability of the refractive correction achieved.1,2 The Originally received: April 21, 1998. Revision accepted: September 3, 1998. Manuscript no. 98206. 1 Instituto Oftalmolo´gico de Alicante, Alicante, Spain. 2 Universidad Miguel Herna´ndez, Alicante, Spain. The authors have no financial interest in any aspect of this article. Address correspondence to Jorge L. Alio´, MD, PhD, Instituto Oftalmolo´gico de Alicante, Avda. Denia, 111, 03015 Alicante, Spain.

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advantages of phakic intraocular lens (PIOL) are more evident in high myopic corrections, in which excimer laser corrections have more limitations and are hampered by problems in night vision, regression, and poor optical quality of the reshaped cornea.3 The development of modern microsurgery, viscoelastics, and the great improvement in surgical knowledge and skills achieved with the development of the aphakic anterior chamber flexible IOLs are positive factors to be considered for the potential of this surgical technique to correct refractive errors. The modern PIOL also has the benefit of the latest technologic development in lens design and industrial production. However, currently, limited data are still available concerning the long-term follow-up of eyes implanted with phakic IOL. The potential complications for eyes implanted with PIOL must be clarified before these lenses are widely used in refractive surgery.

Alio´ et al 䡠 Complications of Phakic AC IOLs for Myopia In this study, we report the results of a large, prospective, nonrandomized, controlled clinical study performed in a consecutive group of patients implanted with angle-supported PIOL analyzed for the first time by cumulative statistical methods to ascertain the potential for complications of this surgical refractive technique.

Patients and Methods Patients Two hundred sixty-three eyes implanted with angle-supported PIOLs since October 1990 were included in this study. All patients were consecutively operated on and followed since their implantation by the same physician in a controlled study. The indications for PIOL implantation were stable axial myopia not treatable by corneal refractive surgery techniques used at our institution; age younger than 50 years and older than 20 years; anterior chamber depth of at least 3.4 mm; central corneal endothelial cell count of at least 2250 cells/mm2; best-corrected spectacle visual acuity of at least 20/200 (0.1); and adequate comprehension of the medical implications of phakic IOL as evidence by signing a written informed consent in accordance with the Helsinki Declaration. No Institutional Review Board approval was required for this study. Exclusion criteria included myopia other than axial; evidence of nuclear sclerosis or developing cataract; history of uveitis, anterior or posterior synechiae, corneal dystrophy; glaucoma or intraocular pressure (IOP) higher than 20 millimeters of mercury (mmHg); or a personal or familial history of retinal detachment. Patients with retinal tears and holes were treated by laser photocoagulation and followed up for 6 months before implant surgery.

Methods A complete preoperative ocular examination was performed on each patient, including gonioscopy, B-scan biometry, and anterior chamber depth estimation by an Ophthasonic Ultrasonic Biometer (Tecknar Inc., St. Louis, MO), applanation Goldmann tonometry (Haag Streit, Bern, Switzerland), and keratometry. The spectacle best-corrected visual acuity was estimated in all patients. A corneal endothelial study of the central cornea was performed by the same physician using a Konan SP5500 contact endothelial cell meter, and cell density, hexagonality, and the coefficient of variation were all documented. At each examination, two to three specular microscopic images (an area of 500 –1000 Um2) of the central portion of each cornea were taken using video specular endothelioscopy. The images were analyzed after digitization by a Konan KC-87 A image analysis system. For each cornea, 100 to 150 cells were digitized and analyzed using the morphometry program of the software. Cell density (cells/square millimeters) was calculated automatically by the computer Cell Analyzer VER 4.00 (Konan Camera Research Institute, Inc., Hyogo, Japan). A subgroup of the first 100 cases implanted with the ZB5M PIOL was followed with a Kowa laser flare meter (LFCM-1000; Kowa Company Ltd, Tokyo, Japan) to ascertain the amount of postoperative subclinical inflammation. Such information was previously published elsewhere.6 Follow-up examinations were made at 48 hours; 15 days; 1, 2, 3, and 6 months; and 1 year after surgery. Additional examinations were performed annually. Patients with complications were examined more frequently as necessary. The endothelial cell study was repeated at the third postoperative month and then annually. A complete ocular examination,

except for gonioscopy, was performed at the third month and then annually. Visits included slit-lamp biomicroscopy, applanation tonometry, peripheral retina examination, spontaneous and bestcorrected visual acuity, and cycloplegic refraction. Perception of night halos and glare was recorded as well in every visit. Surgery was performed by two surgeons: JLA implanted 239 cases while the other 34 cases were implanted by JJPS. Local peribulbar anesthesia with 8 ml of bupivacaine 0.75% and lidocaine 2% was used, and the Honan balloon (Lebanon Corporation, Lebanon, IN) was used for at least 20 minutes before surgery. Mild venous sedation was used when necessary. One drop of 2% pilocarpine (Isopto Carpine 2%; Alcon Cusi, Barcelona, Spain) was instilled in the eye 30 minutes before surgery. The surgical protocol was the same in all cases. With a 45° superblade (Alcon, Forth Worth, TX), a 6-mm valved limbal incision was created superiorly without entering the anterior chamber. Then, a 1-mm paracentesis was made with irrigation of the anterior chamber with 1% Acetylcholine (Alcon Cusi, Barcelona, Spain). The anterior chamber was filled with 2% hydroxypropyl methylcellulose (2% HPMC; Alcon Cusi, Barcelona, Spain) and the incision enlarged to 6 mm with a level-up crescent knife (Alcon, Forth Worth, TX). A 5-mm silicone slide sheet was introduced into the anterior chamber down to the 6-o’clock position, and viscoelastic was again injected over the slide sheet. The PIOL was then introduced toward the 6-o’clock position and the slide was withdrawn. The PIOL was then rotated using a Lester lens dialer (Katena Instruments, Denville, NJ) to the meridian in which the pupil was best centered in relation to the PIOL optic. Special care was taken with this maneuver to prevent damage to the angle structures. The overall diameter of the PIOL to be implanted was estimated intraoperatively by measuring the white-to-white largest corneal meridian diameter using a caliper and then adding 1 mm. We always selected among a total length of 12.5, 13, and 13.5 mm. In cases when the largest corneal diameter plus one did not match the three standard PIOL sizes, the size closest to the larger size was always chosen to avoid postoperative displacement or rotation of the PIOL. After the lens had been placed in the eye, its stability was tested by pressing on the limbus in the meridian of the long axis of the lens to observe any unexpected movements or displacements of the lens. A peripheral iridotomy was always performed using Gill’s scissors (Katena Instruments, Denville, NJ). A three-bite, 10 – 0 running nylon suture was used to close the wound, and, before the knot was tied, irrigation of the anterior chamber with balanced salt solution was performed to remove viscoelastic. Special care was taken to ensure removal of all the viscoelastic by observing the currents of the viscoelastic induced by the balanced salt solution washing of the anterior chamber. The suture was then knotted and a deep sub-Tenon injection of gentamicin (Gevramycin; Schering– Plough, S.A., Madrid, Spain) was administered. Postoperative care included the instillation of 1% cyclopentolate (Alcon Cusi, Barcelona, Spain) and then one drop the next 5 days. Dexamethasone with polymyxin B and neomycin (Maxitrol; Alcon Cusi, Barcelona, Spain) drops were instilled three times a day for 1 month, and topical diclofenac (Voltare´n; Ciba Visio´n, Barcelona, Spain) was instilled three times daily for 3 months. Clinical evaluation of postoperative inflammation was evaluated in every patient and scored after the Uveitis Scoring System Chart.4 The presence of night halos or glare or both was evaluated at the 1-year follow-up, as it was difficult to evaluate earlier. At the end of the first year of follow-up, night halos were recorded as “present but not significant” or “present and significant,” depending on the patient’s subjective estimation of discomfort and how it interfered with quality of life at night.

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Ophthalmology Volume 106, Number 3, March 1999 Phakic Lens Models Used in the Study Two models of PIOL were used in this study. One was the ZB5M model (Chiron Domilens, Lyon, France), which was later named ZB5MF after adding a fluorine surface treatment to improve biocompatibility of the lens. The main features of the lens are singlepiece anterior chamber lens; open loop with total length of 12.5, 13, or 13.5 mm; Kelman-type design of the haptics, 20° angulation; and biconcave optical zone of 5 mm (effective diameter, 4 mm). It is available in 1-diopter increments from ⫺7 to ⫺20 diopters (Fig 1). The ZSAL-4 model (Morcher, Stuttgart, Germany) is a personal design that has similar features concerning the haptic design and 19° angulation. The optic is flat at the anterior surface and concave at the posterior surface (Fig 2). This allows for more distance between the iris plane and the optic of the lens, also reducing the height of the optical edge of the lens, which leaves more space between it and the corneal endothelium. The optic of this lens is 5.5 mm in diameter (effective diameter, 5.0 mm). The lens is supplied in powers ranging from ⫺10 to ⫺23 diopters. This lens became available in Europe in January 1995. The optical edge of the lens is transitional, limiting the convexity of the peripheral edge of the plano– concave diopters with the creation of a triphacetated edge’s surface. No special criteria were followed to choose between ZB5M/ ZB5MF or ZSAL-4 phakic IOL models. In patients with bilateral implants, the two eyes were implanted with the same lens model. Lens Power Calculation. To select the optical power of the IOL, we used the following formula developed by van der Heidje et al5: Piol Power ⫽

⫺n N ⫹ 关nⲐk ⫹ Ps兴 ⫺ d 关nⲐk兴 ⫺ d

Where: Pio ⫽ the power of the negative IOL n ⫽ the refractive index of the aqueous (1.336) d ⫽ distance between the anterior corneal vertex and the principal plane of the IOL in meters k ⫽ dioptric power of the cornea Ps ⫽ equivalent power of the patient’s spectacle correction for the corneal plane Because the distance of the IOL from the anterior surface of the lens is 0.8 mm, the value of d was always calculated as the depth of the anterior chamber minus 0.8 mm. The PIOL was chosen to make the eye from ⫺0.50 to emmetropia. Because the lenses were available in ⫺1-step intervals, a lens was chosen to leave the eye closest to the targeted refraction or slightly myopic. Statistical Analysis. When parametric analysis could be applied, the Student’s t test and analysis of variance (two-way) were applied and differences were considered statistically significant when the probability value was less than 0.05. The Mann–Whitney U test was used for continuous data. When nonparametric tests were needed, the Friedman’s test with the same level of significance was applied to assess the significance of differences between repeated measurements. When this test was significant and multiple comparisons were needed, the Bonferroni’s multiple comparison test was then used. To analyze the normality of the variables, the Kolmogorov–Smirnov test was used with the 0.05 level of significance. The Pearson’s chi-square and two-tailed Fisher’s exact test were used for categoric data. Levels of 0.05 were required for each comparison to be considered significant. The cumulative analysis of complications was studied in every instance by the Kaplan–Meier curves to estimate the relative risk

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for suffering any given complication for the whole series. A mean 95% confidence interval (mean ⫾ 1.96 standard deviation) is given for the estimate time for the occurrence of each complication.

Results A total of 263 PIOL consecutively implanted eyes were included in this study; 157 of the ZB5M model, 80 of the ZB5MF model, and 26 of the ZSAL-4 model bilateral implants were used in 103 patients. When bilateral implants were performed, the same PIOL model was selected for both eyes. Table 1 lists the number of patients in each group being followed from a minimum of 1 year to a maximum of 7 years. The mean follow-up time for patients in this study was 4.89 ⫾ 2.7 years with a range from 1.2 to 7.6 years. The mean PIOL power implanted in the 263 eyes was X ⫽ 16.47 ⫾ 3.025 diopters (minimum, 10 diopters; maximum, 20 diopters). There were no statistically significant differences in the development of any of the complications between ZB5M/ZB5MF and ZSAL-4 group other than halos and glare (P ⬎ 0.01, Friedman’s test). In bilaterally implanted patients, there was no significant difference in the incidence of complications between right and left eyes (P ⬎ 0.05, Student’s t test). Hence, for the following statistical study, we pooled all the cases in a common group to further analyze the individual features that influenced the follow-up of patients. Only when considering halos and glare were the ZB5M/ ZB5MF group and the ZSAL-4 group considered as independent groups.

Halos and Glare Some degree of night halos and glare was reported by 60% of the patients at 1 year of follow-up (157 eyes), although these night halos and glare were considered to be significant by 20.2% of cases (54 eyes) at that point. With time, patients seemed to accommodate to this symptom and, although it was reported in approximately the same proportion of cases, only 10% considered it significant at the 7-year follow-up. There was a statistically higher incidence of “significant” halos and glare reported in patients implanted after January 1995 with the ZB5M/ZB5MF lenses (55 patients) than in the patients implanted with the ZSAL-4 lenses (26 patients) (P ⬍ 0.05, Friedman’s test). Similar levels of “not significant” glare and halos were found in the two groups (P ⬎ 0.05, Friedman’s test).

Postoperative Inflammation Acute postoperative anterior uveitis was observed in 12 cases (4.56%). It was defined as the observation of an evident increase in the level of flare-and-cell counts above normal postoperative baseline levels after the spontaneous postoperatively achieved vision. The anterior uveitis developed from the second to the fifth day after surgery (X ⫽ 3.2 ⫾ 0.9 days). In some cases, inflammation was associated with the development of fibrin membrane formation with a small amount of hypopyon in the absence of ciliary injection (Fig 3). Pain was not reported by any of the patients. In five cases, postoperative uveitis was associated with an elevation of IOP above 25 mmHg. Postoperative uveitis never occurred after the sixth postoperative day. When compared with those patients who did not develop postoperative uveitis, patients who developed uveitis did not suffer from a higher incidence of other complications (P ⬎ 0.05 Fisher’s exact test). Cases with no evident clinical

Alio´ et al 䡠 Complications of Phakic AC IOLs for Myopia

Figure 4. Intraocular pressure (IOP). Kaplan–Meier survival table. After 84 months of follow-up, 86.54% of cases are expected to have normal IOP (⬍21 millimeters of mercury). Figure 1. Clinical appearance of the ZB5MF phakic intraocular lenses 1 month after surgery.

Figure 5. Corneal endothelial cell count. Kaplan–Meier survival table. After 84 months of follow-up, 98.75% of the cases are expected to have a central corneal endothelial density higher than 1500 cells/mm2.

flare meter, and the preliminary results of a pilot study performed on 100 eyes have been published elsewhere by us.6 Figure 2. Clinical appearance of the ZSAL-4 phakic intraocular lenses 1 month after surgery.

anterior uveitis after surgery showed some cells and flare of a 1⫹ grade of the Uveitis Scoring System4 during the first week but not after 2 weeks. This flare-and-cell count was measured by a laser

Figure 3. Acute sterile postoperative inflammation with small hypopyon 3 days after implantation.

Intraocular Pressure An elevation of IOP defined as an increase above 21 mmHg and that required the administration of antiglaucoma treatment was detected in 19 cases (7.2%). None of these required glaucoma surgery to control IOP elevation. There was a significant difference in IOP elevation between the immediate postoperative period and

Figure 6. Significant pupil ovalization observed 3 years after phakic intraocular lens implant. The pupil ovaling is reaching the edge of the optic.

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Ophthalmology Volume 106, Number 3, March 1999 Table 1. Phakic Intraocular Lenses Study Follow-up Period

3 1 2 3 4 5 6

mos yrs yrs yrs yrs yrs yrs

7 yrs

Pupil Ovalization

Type of Lens Implanted

Cases Included in the Study

Cases Lost to Follow-up*

ZB5M/ZB5MF

ZSAL-4

263 251 216 157 49 41 33

NONE 5* 8* 12 13 17 25

237 230 216 169 62 58 58

26 26 8 — — — — —

33

25

58

* All cases lost to follow-up were from the ZB5M/ZB5MF group.

the first and second postoperative months (P ⬍ 0.05 in Bonferroni’s test, P ⬍ 0.05 in Friedman’s test). The Kaplan–Meier survival tables show that after 84 months of follow-up, 86.54% of cases were expected to have a normal IOP (⬍21 mmHg) (Fig 4). No correlation was found between the postoperative elevation of IOP and the development of pupil ovalization or acute anterior uveitis in the early postoperative period (P ⬎ 0.05, Friedman’s test). Pupillary block syndrome did not develop in any of the eyes in this study.

Corneal Endothelium The preoperative mean cell density was 2715.44 ⫾ 393.68 cells/ mm2. After surgery, it decreased to 2690.13 ⫾ 395.08 cells/mm2 at 3 months. This difference was statistically significant (Student’s t test for paired data, P ⬍ 0.05). One year after surgery, cell density was 2640.67 ⫾ 414.19 cells/mm2. When compared to the 3-month value, the differences were found to be statistically significant (Student’s t test for paired data, P ⬍ 0.0001) (Table 2). Statistically significant differences in central endothelial count were found at each postoperative time. The percentage of endothelial cell loss was maximum at the 3-month examination (3.76%) and decreased to 1.83% at the end of the first year and down to 0.56% at the seventh year (Table 2). After the initial loss attributable to the surgical damage, the endothelial loss tended to stabilize after the second year. When the Kaplan–Meier curve was applied to the results of the 7-year follow-up, it was predicted that 84 months after implantation, 98.7% of the cases expect to show a central corneal endothelial density higher than 1500 cells/mm2 (Fig 5).

Significant pupil ovalization, defined as the observation of pupil deviation in the meridian of the placement of the PIOL haptic that reaches the edge of the optic in at least one point (Fig 6), was observed in 16 eyes (6.08%). Lesser degrees of variable ovalization of the pupil were observed in another 27 eyes (10.3%). Four of the cases with significant pupil ovalization were symptomatic and also caused significant reported night glare and halos, as reported by the patients. No correlation was found between the occurrence of ovalization and the gender, dioptric power, or the overall length of the PIOL (P ⬍ 0.05, Fisher’s exact test, Mann– Whitney U test) (Fig 7). Kaplan–Meier’s survival tables indicate that after 84 months of follow-up, 86.97% of patients will not develop pupil ovalization to the degree defined in this study. Significant pupil ovalization was observed in nine cases to occur along the main axis of the PIOL (Fig 8). In the other four eyes, the axis of the ovalization was coincidental with that of the first angle support of the haptic, while in another three eyes, the axis ovalization was along that of the second angle support of the PIOL. When examined by gonioscopy, six of these eyes showed development of a cocoon type of membrane that wrapped around part or the entire plate of the haptic. Ten eyes showed areas of iris atrophy, even some with iris perforation (Fig 9). These findings always appeared in the sector of the iris affected by ovalization. In three of these eyes, extreme ovalization with total sector iris atrophy was observed. Pupil ovalization was not associated with elevation of IOP in any instance.

Phakic Intraocular Lens Explantation Of the 263 cases included in this study, 11 eyes (4.18%) suffered from complications that required explantation. The cause for explantation for nine eyes was the development of a cataract (Fig 10). In all, the explantation was uneventful. A 6-mm incision was made for the explantation, which was closed to 4 mm for phacoemulsification, and implantation of an all-PMMA concave– convex IOL of the AL-3 type (Chiron Domilens, Lyon, France). This IOL is a personal design used by us in eyes elongated more than 28 mm of axial length. The mean age of these patients at PIOL implantation was X ⫽ 42 ⫾ 2.5 years (range, 32–50 years). There was a statistically significant difference in the age when implanted of the group explanted for cataract surgery and all the other patients in the study who did not develop cataract (P ⬍ 0.05, Mann–Whitney U test). Explantation was indicated in the other two eyes because of extreme pupil ovalization with extreme day and night glare that was unbearable for the patients (Fig 9). Kaplan–Meier’s survival

Table 2. Endothelial Cell Count (cells/mm2)

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Time

n

Cell Density (mean ⴞ SD)

Loss (%)

Preoperative Postoperative 3 mos 1 yr 2 yrs 3 yrs 4 yrs 5 yrs 6 yrs 7 yrs

263

2795.44 ⫾ 393.68

—

263 251 216 157 49 41 33 33

2690.13 ⫾ 395.08 2640.67 ⫾ 414.19 2604.41 ⫾ 402.07 2585.55 ⫾ 413.11 2577.89 ⫾ 370.10 2562.42 ⫾ 411.72 2552.17 ⫾ 431.01 2541.92 ⫾ 424.18

3.76 1.83 1.37 0.72 0.3 0.6 0.4 0.56

Cumulative Loss (%)

P (Student’s t test) ⬍0.0001

3.76 5.53 6.83 7.5 7.78 8.33 8.70 9.26

⬍0.0001 ⬍0.0001 ⬍0.0001 ⬍0.0001 ⬍0.0001 ⬍0.0001 ⬍0.0001 ⬍0.05

Alio´ et al 䡠 Complications of Phakic AC IOLs for Myopia

Figure 7. Pupil ovalization. Kaplan–Meier survival table. After 84 months of follow-up, 86.97% of cases are not expected to develop significant pupil ovalization in the terms defined in this study. Figure 10. Nuclear cataract in a case 5 years after implantation.

When the Kaplan–Meier curves were studied after 84 months of follow-up, 95.43% of eyes were not expected to experience a retinal detachment (Fig 12). Details of some of the early cases of retinal detachment have also been reported previously by us.7

Discussion

Figure 8. Pupil ovalization in the meridian of the angle support of the lens haptic.

tables for explantation indicate that after 84 months of follow-up, 89.02% of eyes will retain the PIOL (Fig 11).

Retinal Detachment The incidence of retinal detachment in our study was 3% (eight cases). There was no relationship between the occurrence of retinal detachment and gender, size, or type of PIOL (P ⬎ 0.05; Fisher’s exact test).

Figure 9. Pupil ovalization with areas of iris atrophy and perforation.

The correction of ocular refractive errors by the implantation of PIOLs offers advantages over other refractive surgical techniques that have allowed this procedure to remain as a viable alternative to refractive surgery despite its previous controversial and conflicting history. Phakic intraocular lenses have a well-defined advantage over corneal refractive surgery, especially in moderate and high myopia. Sophisticated refractive surgery techniques such as laser in situ keratomileusis lead to significant corneal optical aberrations due to the formation of an aspheric deformed cornea when used to correct high myopia.3,8 It is important to analyze factors other than refractive change to understand the consequences of a refractive procedure. The lack of reversibility of corneal refractive surgery makes these consequences permanent, and any visual disturbances produced are lifelong. Corneal refractive surgery is affected by regression, especially when high myopic corrections are attempted.2,9 Organic complications such as decentration, corneal opacification due to haze or scarring,10 and mechanical damage to the cornea related to poor quality of the lamellar cut in laser in situ keratomileusis,11 as well as infections affecting the interface12 are additional problems. Moreover, corneal laser refractive surgery requires major financial investments in medical equipment that can become obsolete rapidly because of the constant technologic advances in the field. Conversely, PIOLs are implanted using standard microsurgical techniques that are well known by the majority of ophthalmic surgeons. The surgery is simple and reproducible. The refractive result is stable, and it is potentially reversible by explanting the IOL.13 The optical behavior of the abnormally elongated myopic eye is improved, and the quality of the retinal image is optimized by decreasing optical aberrations and optical magnifications of the im-

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Ophthalmology Volume 106, Number 3, March 1999

Figure 11. Phakic intraocular lens (PIOL) explantation. Kaplan–Meier survival table. After 84 months of follow-up, 89.02% of cases will retain the PIOL in place.

age.14,15 These advantages result from moving the optical correction from the corneal to the intraocular plane. As opposed to clear lens extraction, the other approach suggested for the correction of high myopia, PIOLs, preserve accommodation and do not eliminate or substitute any structural component of the eye.16,17 Posterior capsule opacification is an additional important and as-yet unresolved problem in clear lens extraction.16,17 All of the above-mentioned reasons support the use of PIOL for the correction of refractive errors of the human eye. However, there are potentially important risks for eyes implanted with phakic IOLs that need to be clarified before the procedure is placed into general use. One of the main concerns about this technique has been its potential for damage to the anterior chamber structures,18 especially the corneal endothelium,19 –22 the induction of a chronic elevation of IOP,18 or the subclinical intraocular inflammation.2,6,26 However, the corneal endothelium in this study showed good postoperative behavior. Previous reports on the subject have shown that with previous PIOL models, there is a definitive hazard to the corneal endothelium.1,18 –22 More recent preliminary studies indicated that the new models of angle-supported PIOL are well tolerated by the corneal endothelium because of the substantial improvements made in their design and probably in the quality of surgery.24 The rate of endothelial cell loss found in our study follows a biphasical model figure (Table 2). Most of the endothelial cell loss occurs during the first year after surgery and is probably attributable to surgical trauma. This decrease in the number of endothelial cells continues during the second year, but thereafter, it seems to be similar to that reported after posterior chamber IOL implantation in cataract cases.25 However, despite these encouraging results found in our series and the long-term relative safety for the corneal endothelium as shown by PIOL in this study, we shall caution about the young age at which patients are implanted with a PIOL and the long-term relative risk that these patients may face. According to our results, it might be 20 to 30 years before the patient reaches a point at which the cornea might reach limit values of endothelial cell count (1500 cells/ mm2), a situation in which the eye may harbor a decreased ability to sustain any other types of surgery, including cataract extraction.

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Pupil ovalization has been reported to occur in a significant number of eyes. In the French Multicenter Study, an overall incidence of 22.6% is reported. In 5.8% of the cases, pupil ovalization developed at 1 month, 9.9% at 1 year, 16.7% at 2 years, and 27.5% at 3 years.24 The authors distinguished between discrete nonrelevant ovalization, which was observed in 27 of 30 cases, progressive ovalization in 2, and ovalization associated with iris retraction in the other case. In our study, only cases in which significant ovalization was observed were reported, and the frequency found of 5.9% is different from that of previous figures. The Kaplan–Meier curves indicate that this observation increases with time and that the mean time for our series until the development of significant ovalization was 77 months (6.4 years). Ovalization was associated in 30% of our cases with the development of anterior synechia and atrophic iris changes. The association of pupil ovalization, iris retraction, and atrophy suggests development of ischemic iridopathy and low-grade inflammation, possibly induced by haptic compression of the iris root vessels. We found that ovalization occurred in a significant number of cases not in the meridian of the major axis of the IOL, but in the meridian determined by the tips of the haptic plate. This leads us to believe that the problem could be avoided by improvements in the haptic design, and that excessive or unbalanced pressure at the iris root is the most probable cause of the ovalization. Chronic pressure on the iris root may also be the cause of the chronic breakdown of the blood– ocular barrier measured with the laser flare cell meter, which we previously reported6 and which has been confirmed by other authors.26 In any case, special care should be given in the future to adequate sizing of the PIOL implanted. Intraoperative findings such as the presence of initial ovalization immediately after implantation of the PIOL may indicate inadequate choice of PIOL size for the meridian selected for the implant. Intraoperative angle visualization with a goniolens as a minor may also contribute to a better understanding of this problem. Chronic elevation of IOP that required topical treatment was the other complication found in this study. Topical treatment was sufficient to control these cases, none of which required surgery. Glaucoma was one of the problems encountered with the previous PIOL generations18 that seems to have been avoided in part by the design of the lens

Figure 12. Retinal detachment. Kaplan–Meier survival table. After 84 months of follow-up, 95.43% of cases are not expected to suffer retinal detachment after phakic intraocular lens implantation.

Alio´ et al 䡠 Complications of Phakic AC IOLs for Myopia used in this study. Myopic eyes are especially prone to develop different types of chronic open-angle glaucoma.26 Thus, it is conceivable that the presence of the haptic in the anterior chamber angle could be a further risk for the development of elevation of IOP. This is especially important because anterior synechia30 and pupil ovalization have also been found in this study. However, no correlation was found either between the postoperative elevation of IOP and the presence of ovalization or postoperative elevation of IOP and the development of postoperative acute anterior uveitis. Despite the low cumulative risk predicted by the Kaplan–Meier curves for developing chronic IOP elevation (13.46% at 84 months), we believe that this complication must be carefully monitored, since optic nerve head damage caused by chronic IOP elevation is difficult to detect in high myopia.26 The absence in our study of complications such as pupillary block, which was reported previously in anglesupported PIOL,24 may be related to our inclusion of a peripheral iridotomy in the surgical protocol. Hence, it seems important to keep peripheral iridotomy as part of any protocol for PIOL implantation, as suggested previously by other authors.26 Acute uveitis was a complication observed only during the early postoperative period that seems to be related to irritation of the anterior uvea by surgical manipulations. We did not find any statistically significant associations with other variables in the study that would indicate the need for more intensive topical anti-inflammatory treatment after PIOL implantation. It is our opinion that lens manipulation should be kept at a minimum to avoid triggering of postoperative inflammation. The main cause of explantation was the development of cataract. In this study, all cataracts were of the nuclear type and appeared years after implantation. It seems improbable that the lens implantation triggered the development of cataracts, as this complication was observed in a significantly older age group than the mean age of the study. A careful postoperative examination of the crystalline lens in patients showing a postoperative increase in myopic correction should alert the physician to the development of changes in the lens nucleus. Because cataracts develop earlier in patients with high myopia than in patients without myopia,28,29 and it is difficult to detect the subtle changes during the early stages of nuclear cataract development, it seems important to reconsider PIOL surgery in the older age groups without accommodation. In our study, explantation of the IOL at cataract surgery was uneventful and allowed a planned phacoemulsification procedure without further problems. Another cause of explantation was severe ovalization with iris retraction and atrophy. The PIOLs in these cases were explanted because of serious symptoms, and explantation was extremely difficult. Complications related to the haptic plate contact with the angle tissues have been reported previously29 and are possibly related to the same causes in phakic and aphakic angle-supported anterior chamber lenses. We have previously reported the occurrence of retinal detachment associated with PIOL implantation.7 In the current series, the incidence of retinal detachment showed an

expectation of 4.45% at 79 months. This incidence is higher than that reported for patients with myopia,31 although there are no reports in the literature with patients of the same age and dioptric range. The potential relationship between PIOL implantation and retinal detachment should be studied further. In any case, it seems possible that PIOL implantation, which involves opening the eye with transient lowering of the IOP to atmospheric levels, may be the cause of vitreous instability that may eventually lead either to immediate posterior vitreous detachment and collapse or to chronic alteration of the vitreous structure, which eventually leads to an increased risk for the development of vitreous complications with an increased potential for retinal detachment.7 The results of this study are limited to anterior chamber angle-supported flexible PIOLs. Other types of PIOL, such as iris-fixated anterior chamber PIOL27 and posterior chamber PIOL, which are also offered today as alternatives to patients with high ametropia, may face specific complications other than those reported in this study and also merit controlled studies to ascertain their safety. In summary, this study supports the safety of phakic IOL as a refractive surgical procedure for high myopia, especially regarding the lack of severe complications. In no case was any eye lost because of PIOL implantation itself. However, problems such as pupil ovalization, chronic IOP elevation, and retinal detachment need to be addressed and solved before generalized use of the procedure. As commented on previously by other authors,32–34 there will be patients and surgeons who will find these risks acceptable in relation to the optical correction of the ametropia and quality-of-life benefits that minus anterior chamber lenses offer in the correction of high myopia. However, longer follow-up of patients in clinically controlled studies similar to this study is mandatory to finally confirm their adequacy as a generalized refractive surgical procedure.

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