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Recovery of Visual Acuity After Epikeratophakia and Secondary Intraocular Lens Implantation for Aphakia
Recovery of Visual Acuity After Epikeratophakia and Secondary Intraocular Lens Implantation for Aphakia A.K. BATES and B.L. HALLIDAY Moorfields eye Hospital, City Road, London
Recovery of visual acuity was examined in a group of 40 cases reviewed retrospectively after secondary anterior chamber lens implantation and compared with that in 25 cases followed prospectively after epikeratophakia. At 6 months after surgery 68% of those who had received an intraocular lens and 64% of those who underwent epikeratophakia achieved 6/9 visual acuity or better with spectacle correction. However, whilst 95% of the secondary intraocular lens patients had attained 6/12 vision by this time only 72% of those in the epikeratophakia group had done so. Kaplan-Meier analysis showed that the intraocular lens group reached 6/12 vision much more quickly than the epikeratophakia group but this difference is much reduced by the time 6/9 vision is attained and is probably not important clinically. Keywords: Epikeratophakia; Secondary intraocular lens; Visual recovery
INTRODUCTION
Many patients are successfully corrected for monocular aphakia with a contact lens [1]. However, with time, an increasing number are unable to continue contact lens wear for various reasons, including difficulties of manipulation or intolerance due to ocular surface problems [2]. In such cases surgical intervention in the form of secondary intraocular lens implantation or epikeratophakia may be required. Secondary intraocular lens implantation in such cases is usually limited to the use of anterior chamber implants either because cataract extraction was by the intracapsular technique or because extracapsular surgery was complicated by disruption of the posterior capsule. Secondary lens implantation may correct aphakia to within one line of the preoperative Snellen acuity in 90% of cases and result in 6/12 vision in 80% of cases [3-5]. Serious complications of secondary intraocular lens implantation include cystoid macular oedema, uveitis-glaucoma-hyphaema syndrome, chronic uveitis, corneal decompensation, retinal detachment, endophthalmitis and postoperative astigmatism. The reported incidence of these complications are very variable ranging from 5-20% [4,6-8]. Correspondence to: A.K. Bates FRCS, Moornelds Eye Hospital, City Road, London, ECIV 2PD. 0955-3681/91/020103+05 $03.00/0 © 1991 Bailliere Tindall
Epikeratophakia was described for the correction of aphakia in 1980 [9] and there have been several reports of clinical results [10-12]. It is thought to be a safe and reversible extraocular procedure and may be the surgical technique of choice for aphakic correction in those eyes with persistent uveitis, anterior segment abnormalities and perhaps those with a diminished corneal endothelial reserve. Reported complications include over and under correction and astigmatism, failure to re-epithelialize, infection, vascularization and glare [13-15]. A further disadvantage of epikeratophakia which has been reported is that the final visual acuity achieved is poorer than that following secondary intraocular lens implantation and takes much longer to achieve [16,17]. In order to investigate this we have compared the recovery of visual acuity in consecutive patients undergoing epikeratophakia with that in patients undergoing secondary intraocular lens implantation for the correction of aphakia. METHOD
We reviewed retrospectively the visual results of 40 eyes (in 36 patients) that underwent secondary anterior chamber intraocular lens implantation by multiple surgeons. These patients were initially corrected for aphakia with a contact lens and only when cur J Implant Ref Surg, Vol 3, June 1991
104
this was no longer possible or desirable were they considered for surgery. None of the patients was known to have any ocular pathology other than cataract, likely to reduce the final visual acuity, and all had good visual acuity of 6/9 or better. Of the 40 cases 28 had previously undergone intracapsular cataract surgery, eight extracapsular surgery complicated by posterior capsule rupture and four lensectomy following trauma. Rayner or Cilco flexible loop PMMA lenses were introduced through a corneal section with viscoelastic protection. The section was closed with interrupted 10-0 nylon sutures. Anterior vitrectomy was performed when considered necessary by the surgeon. This was the case in ten of the patients who had previously undergone intracapsular surgery and in one of the patients who had previously undergone complicated extracapsular surgery. The mean age of patients undergoing secondary intraocular lens implantation was 70.1 years (range 24-90). Visual recovery was measured by refracted Snellen visual acuity and patients were followed until they had achieved 6/9 vision. The average length of follow-up was 8.3 months. Twenty-five eyes (in 25 patients) were followed prospectively after aphakic correction by epikeratophakia. The indications for surgery in these patients were aphakia following trauma in 11 cases, intracapsular cataract surgery for senile cataract in ten cases, extracapsular cataract surgery for heterochromic cyclitis in two cases, congenital cataract surgery in one case and extracapsular cataract surgery for cataract complicating multiple retinal detachment procedures in one case. In all cases contact lens correction of aphakia had been attempted and had failed. These patients all had good visual acuity, 6/9 or better, and were not known to have any ocular pathology other than cataract, likely to affect final visual outcome. Epikeratophakia lenses were individually manufactured for each patient using a modified contact lens lathe fitted with cryo elements [18]. A computer program was used to calculate the required radius of cut for both the optical zone and the wing of the lens [19]. Epikeratophakia was performed by a standard technique by one surgeon under general anaesthesia. Host epithelium was removed mechanically. A Hessburg-Baron trephine was used to make a partial thickness trephination and then a fashioned 23gauge needle was used to dissect a peripheral lame 1lar pocket. The lens was sewn in with interrupted sutures. Subconjunctival antibiotic was administered at the end of surgery and in the initial ten cases only, a bandage contact lens inserted to help epithelialization. The eye was padded for 24 hours
A.K. Bates, B.L. Halliday
only. In every case epithelialization proceeded steadily with an average time to complete epithelialization of 3.9 days (range 3-6). The mean age of patients in the epikeratophakia group was 47.4 years (range 9-82). Visual recovery was measured by refracted Snellen visual acuity. The average length offollow-up was 8.9 months. RESULTS
The best visual acuities at the closest refraction to 6 months after surgery are shown in Fig. 1. An acuity
~l
== Epikeratophakio
40
'" C '" °15
Q.
Lens implant
30
'0
c '"~
o
20
'"
0..
r
10 0
6/60 Visual acuity
Fig. 1 Refracted visual acuity in all patients at 6 months or longer. Open boxes-epikeratophakia group. hatched boxessecondary intraocular lens group
of 6/9 or better was achieved in 67.5% of the secondary intraocular lens group and in 64.0% of the epikeratophakia group. By 6 months 95.0% of the patients who had received intraocular lenses had reached 6/12 vision, whilst only 72.0% of the epikeratophakia patients had achieved this acuity. The pattern of visual recovery in these two groups of patients is presented as Kaplan-Meier curves which provide estimates of the probability of achieving a given visual acuity at different times [20]. This type of plot has the advantage that it allows the inclusion of censored observations which arise through loss to follow-up or because follow-up has been insufficiently long for patients to achieve a stated visual acuity. Curves are plotted for 6/12 and 6/9 refracted visual acuity (Figs 2, 3). There was a probability of 0.5 of achieving 6/12 vision at 1.75 months in the secondary intraocular lens group and at 4.43 months in the epikeratophakia group. The probability of achieving 6/9 vision reached 0.5 at 3.75 months in the secondary intraocular lens group and at 4.81 months in the epikeratophakia group. Complications in the secondary intraocular lens group of patients are shown in Table 1. All of these resolved, although two required further surgical intervention. Complications in the epikeratophakia Eur J Implant Ref Surg, Vol 3, June 1991
Visual recovery after eplkeratophakla and lens Implantation ?: 1.0 ,,; o
u
C\J
~
go c E 0.5
...
......
o
" ?: :0 o
.0
ct
o
6
12
18
Mont hs from surgery
Fig. 2 Kaplan-Meier curve for probability of attaining 6/12 vision by time t. Solid line-epikeratophakia group, broken line-secondary intraocular lens group
,.,
1.0
''';
u 0
(1)
"-
ID 0'
c:
'c
.§ 0.5 0
" ?:
15
0 .0 0
d:
12
0
18
Months from sur<;jery
Fig. 3 Kaplan-Meier curve for probability of attaining 6/9 vision by time t. Solid line-epikeratophakia group, broken line-secondary intraocular lens group
Table 1 Complications: secondary IOL group No. of Outcome cases Settled on treatment Excessive post-op. uveitis 1 Settled on treatment 1 Fibrinous uveitis Settled spontaneously 2 Cystoid macular oedema Resutured 1 Dehiscence of section IOL replaced 1 Instability of IOL
patients are shown in Table 2; in three cases the lenticule was removed because of poor refractive correction (spherical refractive errors of 4.4, 4.7 and 8.8D at the cornea). Table 2 Complications: epikeratophakia group No. of cases Outcome Poor refractive correction Lenticule removed 3 Stable-no intervention Interface opacities 3 Epithelial breakdown Settled with treatment 2 Settled with treatment Filamentary keratitis 1 Settled with treatment. Suture reaction 1
DISCUSSION
Comparing these two groups of patients 6 months Eur J Implant Ref Surg, Vol 3, June 1991
105
after surgery, 67.5% of those who had received an intraocular lens and 64.0% of those who underwent epikeratophakia achieved 6/9 visual acuity or better with spectacle correction. Although this difference was small there was more scatter in the epikeratophakia group (Fig. 1) and whilst 95.0% of the secondary intraocular lens patients had attained 6/12 vision by this time point only 72.0% of those in the epikeratophakia group had done so . The pattern of visual recovery in the two groups towards 6/12 and 6/9 vision can be compared for all patients in the study using the Kaplan-Meier analysis. This demonstrates that whilst the intraocular lens group attain 6112 vision much more quickly than the epikeratophakia group (probability of 0.5 is reached at 1.75 us 4.43 months), this difference is greatly diminished by the time 6/9 vision is attained (probability of 0.5 is reached at 3.75 us 4.81 months). For the majority of patients these time differences, of only a few weeks, would not be clinically important. The difference between the two groups is therefore better vision with greater predictability at 6 months after surgery in the intraocular lens group with slightly quicker visual rehabilitation. In this study visual acuity was used as the only measure of visual function. Other tests may show further differences between the two surgical techniques. Contrast sensitivity in an epikeratophakia eye is reduced when compared with the fellow normal eye, especially in the presence of a glare source and with dilated pupils [21]. Work in progress is comparing contrast sensitivity in aphakic eyes corrected with contact lens, intraocular implant or epikeratophakia. The complication rate was similar for each of the techniques of aphakic correction. In the epikeratophakia group three patients had a poor refractive result (spherical errors of 4.4, 4.7 and 8.8D) because of early difficulties in calculation of the power of the lenticule. These have been overcome and now 81 % of lenticules produced are within 3D of their predicted correction [20]. In each case the lens was removed with no ill effect. The other complications in this group were minor and settled quickly on treatment. In the secondary intraocular lens group, whilst the number of complications was similar two cases required further intraocular surgery, with its accompanying risks, and the remaining complications each carried the risk of long-term reduction in visual acuity (cystoid macular oedema, excessive or fibrinous uveitis). Thus, whilst the two techniques have similar complication rates the potential severity and reversibility of these complications may be quite different. However, a much larger series with longer
A.K. Bates, B.L. Halliday
106
follow-up would be necessary to evaluate these relative risks more thoroughly. In conclusion both epikeratophakia and secondary intraocular lens implantation offer effective correction of aphakia in those patients who are no longer able or willing to use a contact lens. Epikeratophakia is clearly the procedure of choice in the presence of a disorganized anterior segment, chronic inflammation or a compromised corneal endothelium, although it may not be without its own effects on endothelial cells. In other cases in which there is no contraindication to a secondary intraocular lens the decision as to which procedure is most appropriate depends on a number offactors. Secondary intraocular lens implantation appears to provide slightly earlier visual rehabilit~tion and more predictable improvement in visual acuity within 6 months of surgery, although the differences are not great. Furthermore, on other measures of visual function epikeratophakia may have disadvantages and further work is in progress to elucidate these. On the other hand secondary lens implantation requires intraocular surgery, carries the risk of sight-threatening complications and does not have the same facility of reversibility. All these factors must be weighed before a decision may be reached as to the most prudent technique to correct aphakia in any individual patient.
REFERENCES 1 CM Graham, JKG Dart, RJ Buckley. Extended wear hydrogel and daily wear hard contact lens for aphakia. Success and complications in a longitudinal study. Ophthalmology, 1986; 93: 1489-1494. 2 Oxford Cataract Treatment and Evaluation Team: The use of contact lenses to correct aphakia in a clinical trial of cataract management. Eye, 1990; 4: 138-144.
3 WJ Stark, AE Maumenee, ME Dangel et al. Intraocular lenses. Experience at the Wilmer Institute. Ophthalmology, 1982; 89: 104-108. 4 MC KrafT, DR Sanders, HL Lieberman et al. Secondary intraocular lens implantation. Ophthalmology, 1983; 9: 324-326. 5 JA Stanley. Secondary implantation of intraocular lenses. Trans. Pac. Coast Oto-Ophthalmol. Soc., 1985; 66: 55-58. 6 DJ Apple, N Mamalis, K Loftfield et al. Complications of intraocular lenses. A historical and histopathological review. Surv. Ophthalmol., 1984; 29: 1-54. 7 HJF Shammas, CF Milkie. Secondary lens implantation in Aphakia. Visual results and complications. Am. Intraoc. Implant Soc. J., 1978; 4: 180-183. 8 TR Mazzocco, RP Kratz, B Davidson et al. Secondary lens implantation. Am. Intraoc. Implant Soc. J., 1981; 7: 341-343. 9 HE Kaufman. The correction of aphakia. 36th Edward Jackson Memorial Lecture. Am. J. Ophthalmol., 1980; 89: 1-10. 10 TP Werblin, HE Kaufman, MH Friedlander et al. A prospective study of the use of hyperopic epikeratophakia grafts for the correction of aphakia in adults. Ophthalmology, 1981; 88: 1137-1140. 11 TP Werblin, HE Kaufman, MH Friedlander et al. Epikeratophakia. The surgical correction of aphakia. Update 1981. Ophthalmology, 1982; 89: 916-920. 12 RC Arffa, M Busin, BA Barron et al. Epikeratophakia with commercially prepared tissue for the correction of aphakia in adults. Arch. Ophthalmol., 1986; 104: 1467-1472. 13 TP Werblin. Epikeratophakia. Techniques, complications and clinical results. Int. Ophthalmol. Clin., 1983; 23: 45-58. 14 PS Binder. Optical problems following refractive surgery. Ophthalmology, 1986; 93: 739-745. 15 MB McDonald, HE Kaufman, JV Aquavella et al. The nationwide study of epikeratophakia for aphakia in adults. Am. J. Ophthalmol., 1987; 103: 358-365. 16 HE Kaufman, M. McDonald. Refractive surgery for aphakia and myopia. Trans. Ophthalmol. Soc. U.K., 1945; 104: 43-47. 17 DS Durrie, DL Habrich, TR Dietze. Secondary intraocular lens implantation vs epikeratophakia for the treatment of aphakia. Am. J. Ophthalmol., 1987; 103: 384-391. 18 BL Halliday. Manufacture of epikeratophakia lens. Eye, 1988; 2: 395-399. 19 BL Halliday. Simplified formulae for lathing epikeratophakia lenses. Ophthalmic Surg., 1991; in press. 20 SJ Pocock. Clinical Trials: A Practical Approach. Chichester: Wiley, 1983. 21 BL Halliday. Alternatives to contact lens wear: epikeratophakia. Trans. Brit. Contact Lens Ass. Int. Coni, 1988; 76-78.
Editor: Could you expand on the choice that has to recovery of visual acuity after epikeratophakia be made between epikeratophakia and secondary in- should be a significant factor in deciding between traocular lens implantation as a management of these two procedures. The aim of this paper was to aphakia. address this question, by comparing the pattern and time course of recovery of visual acuity in these two Answer: Our paper concerns the management of groups. The levels of final visual acuity, refractive aphakic patients, who are unsuitable for, or who errors, degrees of astigmatism etc., have all been have become intolerant to contact lens correction of adequately documented in both these groups of their aphakia. A number of these patients are patients by us, and by others elsewhere. For this clearly unsuitable for either secondary intraocular reason, we have not included detailed values of lens implantation, or for epikeratophakia. There uncorrected and corrected visual acuities in the two remains quite a large group of patients for whom groups of patients at multiple time points, nor have either procedure would be suitable, but at the we quoted comparative degrees of corneal astigmapresent time, there is doubt as to which is the prefer- tism. Furthermore, it is specifically for this reason, able procedure in such cases. The question has been that we have chosen the Kaplan-Meier method of raised, as to whether the relatively slower rate of demonstrating our results, so that they would not be Eur J Implant Ref Surg, Val 3. June 1991
Visual recovery after eplkeratophakia and lens Implantation
adversely affected by the fact that patients have reached different stages of follow-up, have been refracted at different time points, and in some cases have not yet achieved stable visual acuity. The reason why only 72% of the epikeratophakia patients reach a visual acuity of 6112 at 6 months is related to changes occurring in the lenticule, and in the cornea overall, and is similar to findings in other studies. In stating that all of the patients in the two groups had good visual acuity, i.e. 6/9 or better, and were not known to have any other ocular pathology than cataract, the implication was that none of these patients had any macular pathology, and therefore were all felt to have the potential to achieve 6/9 or better vision after their aphakic correction by whichever means.
Eur J Implant Ref Surg. Val 3. June 1991
107
The reasons why seven patients had not attained the visual acuity of 6/12 after 6 months in the epikeratophakia group, were not presented since these patients are all expected to attain such a visual acuity in due course. It is simply a reflection of this technique that they have not done so at this stage. The quoted value of 81% of lenticules produced, being within three dioptres of their predicted correction, is similar to values presented by other workers, and may well be as accurate as this technique will allow. It is fully appreciated that this compares poorly with the precision of modern intraocular lens calculation, and this is clearly a factor which must be considered in the decision as to which technique should be used to correct aphakic patients for whom either epikeratophakia or secondary lens implantation would be suitable.
Recovery of visual acuity was examined in a group of 40 cases reviewed retrospectively after secondary anterior chamber lens implantation and compared with that in 25 cases followed prospectively after epikeratophakia. At 6 months after surgery 68% of those who had received an intraocular lens and 64% of those who underwent epikeratophakia achieved 6/9 visual acuity or better with spectacle correction. However, whilst 95% of the secondary intraocular lens patients had attained 6/12 vision by this time only 72% of those in the epikeratophakia group had done so. Kaplan-Meier analysis showed that the intraocular lens group reached 6/12 vision much more quickly than the epikeratophakia group but this difference is much reduced by the time 6/9 vision is attained and is probably not important clinically. Keywords: Epikeratophakia; Secondary intraocular lens; Visual recovery
INTRODUCTION
Many patients are successfully corrected for monocular aphakia with a contact lens [1]. However, with time, an increasing number are unable to continue contact lens wear for various reasons, including difficulties of manipulation or intolerance due to ocular surface problems [2]. In such cases surgical intervention in the form of secondary intraocular lens implantation or epikeratophakia may be required. Secondary intraocular lens implantation in such cases is usually limited to the use of anterior chamber implants either because cataract extraction was by the intracapsular technique or because extracapsular surgery was complicated by disruption of the posterior capsule. Secondary lens implantation may correct aphakia to within one line of the preoperative Snellen acuity in 90% of cases and result in 6/12 vision in 80% of cases [3-5]. Serious complications of secondary intraocular lens implantation include cystoid macular oedema, uveitis-glaucoma-hyphaema syndrome, chronic uveitis, corneal decompensation, retinal detachment, endophthalmitis and postoperative astigmatism. The reported incidence of these complications are very variable ranging from 5-20% [4,6-8]. Correspondence to: A.K. Bates FRCS, Moornelds Eye Hospital, City Road, London, ECIV 2PD. 0955-3681/91/020103+05 $03.00/0 © 1991 Bailliere Tindall
Epikeratophakia was described for the correction of aphakia in 1980 [9] and there have been several reports of clinical results [10-12]. It is thought to be a safe and reversible extraocular procedure and may be the surgical technique of choice for aphakic correction in those eyes with persistent uveitis, anterior segment abnormalities and perhaps those with a diminished corneal endothelial reserve. Reported complications include over and under correction and astigmatism, failure to re-epithelialize, infection, vascularization and glare [13-15]. A further disadvantage of epikeratophakia which has been reported is that the final visual acuity achieved is poorer than that following secondary intraocular lens implantation and takes much longer to achieve [16,17]. In order to investigate this we have compared the recovery of visual acuity in consecutive patients undergoing epikeratophakia with that in patients undergoing secondary intraocular lens implantation for the correction of aphakia. METHOD
We reviewed retrospectively the visual results of 40 eyes (in 36 patients) that underwent secondary anterior chamber intraocular lens implantation by multiple surgeons. These patients were initially corrected for aphakia with a contact lens and only when cur J Implant Ref Surg, Vol 3, June 1991
104
this was no longer possible or desirable were they considered for surgery. None of the patients was known to have any ocular pathology other than cataract, likely to reduce the final visual acuity, and all had good visual acuity of 6/9 or better. Of the 40 cases 28 had previously undergone intracapsular cataract surgery, eight extracapsular surgery complicated by posterior capsule rupture and four lensectomy following trauma. Rayner or Cilco flexible loop PMMA lenses were introduced through a corneal section with viscoelastic protection. The section was closed with interrupted 10-0 nylon sutures. Anterior vitrectomy was performed when considered necessary by the surgeon. This was the case in ten of the patients who had previously undergone intracapsular surgery and in one of the patients who had previously undergone complicated extracapsular surgery. The mean age of patients undergoing secondary intraocular lens implantation was 70.1 years (range 24-90). Visual recovery was measured by refracted Snellen visual acuity and patients were followed until they had achieved 6/9 vision. The average length of follow-up was 8.3 months. Twenty-five eyes (in 25 patients) were followed prospectively after aphakic correction by epikeratophakia. The indications for surgery in these patients were aphakia following trauma in 11 cases, intracapsular cataract surgery for senile cataract in ten cases, extracapsular cataract surgery for heterochromic cyclitis in two cases, congenital cataract surgery in one case and extracapsular cataract surgery for cataract complicating multiple retinal detachment procedures in one case. In all cases contact lens correction of aphakia had been attempted and had failed. These patients all had good visual acuity, 6/9 or better, and were not known to have any ocular pathology other than cataract, likely to affect final visual outcome. Epikeratophakia lenses were individually manufactured for each patient using a modified contact lens lathe fitted with cryo elements [18]. A computer program was used to calculate the required radius of cut for both the optical zone and the wing of the lens [19]. Epikeratophakia was performed by a standard technique by one surgeon under general anaesthesia. Host epithelium was removed mechanically. A Hessburg-Baron trephine was used to make a partial thickness trephination and then a fashioned 23gauge needle was used to dissect a peripheral lame 1lar pocket. The lens was sewn in with interrupted sutures. Subconjunctival antibiotic was administered at the end of surgery and in the initial ten cases only, a bandage contact lens inserted to help epithelialization. The eye was padded for 24 hours
A.K. Bates, B.L. Halliday
only. In every case epithelialization proceeded steadily with an average time to complete epithelialization of 3.9 days (range 3-6). The mean age of patients in the epikeratophakia group was 47.4 years (range 9-82). Visual recovery was measured by refracted Snellen visual acuity. The average length offollow-up was 8.9 months. RESULTS
The best visual acuities at the closest refraction to 6 months after surgery are shown in Fig. 1. An acuity
~l
== Epikeratophakio
40
'" C '" °15
Q.
Lens implant
30
'0
c '"~
o
20
'"
0..
r
10 0
6/60 Visual acuity
Fig. 1 Refracted visual acuity in all patients at 6 months or longer. Open boxes-epikeratophakia group. hatched boxessecondary intraocular lens group
of 6/9 or better was achieved in 67.5% of the secondary intraocular lens group and in 64.0% of the epikeratophakia group. By 6 months 95.0% of the patients who had received intraocular lenses had reached 6/12 vision, whilst only 72.0% of the epikeratophakia patients had achieved this acuity. The pattern of visual recovery in these two groups of patients is presented as Kaplan-Meier curves which provide estimates of the probability of achieving a given visual acuity at different times [20]. This type of plot has the advantage that it allows the inclusion of censored observations which arise through loss to follow-up or because follow-up has been insufficiently long for patients to achieve a stated visual acuity. Curves are plotted for 6/12 and 6/9 refracted visual acuity (Figs 2, 3). There was a probability of 0.5 of achieving 6/12 vision at 1.75 months in the secondary intraocular lens group and at 4.43 months in the epikeratophakia group. The probability of achieving 6/9 vision reached 0.5 at 3.75 months in the secondary intraocular lens group and at 4.81 months in the epikeratophakia group. Complications in the secondary intraocular lens group of patients are shown in Table 1. All of these resolved, although two required further surgical intervention. Complications in the epikeratophakia Eur J Implant Ref Surg, Vol 3, June 1991
Visual recovery after eplkeratophakla and lens Implantation ?: 1.0 ,,; o
u
C\J
~
go c E 0.5
...
......
o
" ?: :0 o
.0
ct
o
6
12
18
Mont hs from surgery
Fig. 2 Kaplan-Meier curve for probability of attaining 6/12 vision by time t. Solid line-epikeratophakia group, broken line-secondary intraocular lens group
,.,
1.0
''';
u 0
(1)
"-
ID 0'
c:
'c
.§ 0.5 0
" ?:
15
0 .0 0
d:
12
0
18
Months from sur<;jery
Fig. 3 Kaplan-Meier curve for probability of attaining 6/9 vision by time t. Solid line-epikeratophakia group, broken line-secondary intraocular lens group
Table 1 Complications: secondary IOL group No. of Outcome cases Settled on treatment Excessive post-op. uveitis 1 Settled on treatment 1 Fibrinous uveitis Settled spontaneously 2 Cystoid macular oedema Resutured 1 Dehiscence of section IOL replaced 1 Instability of IOL
patients are shown in Table 2; in three cases the lenticule was removed because of poor refractive correction (spherical refractive errors of 4.4, 4.7 and 8.8D at the cornea). Table 2 Complications: epikeratophakia group No. of cases Outcome Poor refractive correction Lenticule removed 3 Stable-no intervention Interface opacities 3 Epithelial breakdown Settled with treatment 2 Settled with treatment Filamentary keratitis 1 Settled with treatment. Suture reaction 1
DISCUSSION
Comparing these two groups of patients 6 months Eur J Implant Ref Surg, Vol 3, June 1991
105
after surgery, 67.5% of those who had received an intraocular lens and 64.0% of those who underwent epikeratophakia achieved 6/9 visual acuity or better with spectacle correction. Although this difference was small there was more scatter in the epikeratophakia group (Fig. 1) and whilst 95.0% of the secondary intraocular lens patients had attained 6/12 vision by this time point only 72.0% of those in the epikeratophakia group had done so . The pattern of visual recovery in the two groups towards 6/12 and 6/9 vision can be compared for all patients in the study using the Kaplan-Meier analysis. This demonstrates that whilst the intraocular lens group attain 6112 vision much more quickly than the epikeratophakia group (probability of 0.5 is reached at 1.75 us 4.43 months), this difference is greatly diminished by the time 6/9 vision is attained (probability of 0.5 is reached at 3.75 us 4.81 months). For the majority of patients these time differences, of only a few weeks, would not be clinically important. The difference between the two groups is therefore better vision with greater predictability at 6 months after surgery in the intraocular lens group with slightly quicker visual rehabilitation. In this study visual acuity was used as the only measure of visual function. Other tests may show further differences between the two surgical techniques. Contrast sensitivity in an epikeratophakia eye is reduced when compared with the fellow normal eye, especially in the presence of a glare source and with dilated pupils [21]. Work in progress is comparing contrast sensitivity in aphakic eyes corrected with contact lens, intraocular implant or epikeratophakia. The complication rate was similar for each of the techniques of aphakic correction. In the epikeratophakia group three patients had a poor refractive result (spherical errors of 4.4, 4.7 and 8.8D) because of early difficulties in calculation of the power of the lenticule. These have been overcome and now 81 % of lenticules produced are within 3D of their predicted correction [20]. In each case the lens was removed with no ill effect. The other complications in this group were minor and settled quickly on treatment. In the secondary intraocular lens group, whilst the number of complications was similar two cases required further intraocular surgery, with its accompanying risks, and the remaining complications each carried the risk of long-term reduction in visual acuity (cystoid macular oedema, excessive or fibrinous uveitis). Thus, whilst the two techniques have similar complication rates the potential severity and reversibility of these complications may be quite different. However, a much larger series with longer
A.K. Bates, B.L. Halliday
106
follow-up would be necessary to evaluate these relative risks more thoroughly. In conclusion both epikeratophakia and secondary intraocular lens implantation offer effective correction of aphakia in those patients who are no longer able or willing to use a contact lens. Epikeratophakia is clearly the procedure of choice in the presence of a disorganized anterior segment, chronic inflammation or a compromised corneal endothelium, although it may not be without its own effects on endothelial cells. In other cases in which there is no contraindication to a secondary intraocular lens the decision as to which procedure is most appropriate depends on a number offactors. Secondary intraocular lens implantation appears to provide slightly earlier visual rehabilit~tion and more predictable improvement in visual acuity within 6 months of surgery, although the differences are not great. Furthermore, on other measures of visual function epikeratophakia may have disadvantages and further work is in progress to elucidate these. On the other hand secondary lens implantation requires intraocular surgery, carries the risk of sight-threatening complications and does not have the same facility of reversibility. All these factors must be weighed before a decision may be reached as to the most prudent technique to correct aphakia in any individual patient.
REFERENCES 1 CM Graham, JKG Dart, RJ Buckley. Extended wear hydrogel and daily wear hard contact lens for aphakia. Success and complications in a longitudinal study. Ophthalmology, 1986; 93: 1489-1494. 2 Oxford Cataract Treatment and Evaluation Team: The use of contact lenses to correct aphakia in a clinical trial of cataract management. Eye, 1990; 4: 138-144.
3 WJ Stark, AE Maumenee, ME Dangel et al. Intraocular lenses. Experience at the Wilmer Institute. Ophthalmology, 1982; 89: 104-108. 4 MC KrafT, DR Sanders, HL Lieberman et al. Secondary intraocular lens implantation. Ophthalmology, 1983; 9: 324-326. 5 JA Stanley. Secondary implantation of intraocular lenses. Trans. Pac. Coast Oto-Ophthalmol. Soc., 1985; 66: 55-58. 6 DJ Apple, N Mamalis, K Loftfield et al. Complications of intraocular lenses. A historical and histopathological review. Surv. Ophthalmol., 1984; 29: 1-54. 7 HJF Shammas, CF Milkie. Secondary lens implantation in Aphakia. Visual results and complications. Am. Intraoc. Implant Soc. J., 1978; 4: 180-183. 8 TR Mazzocco, RP Kratz, B Davidson et al. Secondary lens implantation. Am. Intraoc. Implant Soc. J., 1981; 7: 341-343. 9 HE Kaufman. The correction of aphakia. 36th Edward Jackson Memorial Lecture. Am. J. Ophthalmol., 1980; 89: 1-10. 10 TP Werblin, HE Kaufman, MH Friedlander et al. A prospective study of the use of hyperopic epikeratophakia grafts for the correction of aphakia in adults. Ophthalmology, 1981; 88: 1137-1140. 11 TP Werblin, HE Kaufman, MH Friedlander et al. Epikeratophakia. The surgical correction of aphakia. Update 1981. Ophthalmology, 1982; 89: 916-920. 12 RC Arffa, M Busin, BA Barron et al. Epikeratophakia with commercially prepared tissue for the correction of aphakia in adults. Arch. Ophthalmol., 1986; 104: 1467-1472. 13 TP Werblin. Epikeratophakia. Techniques, complications and clinical results. Int. Ophthalmol. Clin., 1983; 23: 45-58. 14 PS Binder. Optical problems following refractive surgery. Ophthalmology, 1986; 93: 739-745. 15 MB McDonald, HE Kaufman, JV Aquavella et al. The nationwide study of epikeratophakia for aphakia in adults. Am. J. Ophthalmol., 1987; 103: 358-365. 16 HE Kaufman, M. McDonald. Refractive surgery for aphakia and myopia. Trans. Ophthalmol. Soc. U.K., 1945; 104: 43-47. 17 DS Durrie, DL Habrich, TR Dietze. Secondary intraocular lens implantation vs epikeratophakia for the treatment of aphakia. Am. J. Ophthalmol., 1987; 103: 384-391. 18 BL Halliday. Manufacture of epikeratophakia lens. Eye, 1988; 2: 395-399. 19 BL Halliday. Simplified formulae for lathing epikeratophakia lenses. Ophthalmic Surg., 1991; in press. 20 SJ Pocock. Clinical Trials: A Practical Approach. Chichester: Wiley, 1983. 21 BL Halliday. Alternatives to contact lens wear: epikeratophakia. Trans. Brit. Contact Lens Ass. Int. Coni, 1988; 76-78.
Editor: Could you expand on the choice that has to recovery of visual acuity after epikeratophakia be made between epikeratophakia and secondary in- should be a significant factor in deciding between traocular lens implantation as a management of these two procedures. The aim of this paper was to aphakia. address this question, by comparing the pattern and time course of recovery of visual acuity in these two Answer: Our paper concerns the management of groups. The levels of final visual acuity, refractive aphakic patients, who are unsuitable for, or who errors, degrees of astigmatism etc., have all been have become intolerant to contact lens correction of adequately documented in both these groups of their aphakia. A number of these patients are patients by us, and by others elsewhere. For this clearly unsuitable for either secondary intraocular reason, we have not included detailed values of lens implantation, or for epikeratophakia. There uncorrected and corrected visual acuities in the two remains quite a large group of patients for whom groups of patients at multiple time points, nor have either procedure would be suitable, but at the we quoted comparative degrees of corneal astigmapresent time, there is doubt as to which is the prefer- tism. Furthermore, it is specifically for this reason, able procedure in such cases. The question has been that we have chosen the Kaplan-Meier method of raised, as to whether the relatively slower rate of demonstrating our results, so that they would not be Eur J Implant Ref Surg, Val 3. June 1991
Visual recovery after eplkeratophakia and lens Implantation
adversely affected by the fact that patients have reached different stages of follow-up, have been refracted at different time points, and in some cases have not yet achieved stable visual acuity. The reason why only 72% of the epikeratophakia patients reach a visual acuity of 6112 at 6 months is related to changes occurring in the lenticule, and in the cornea overall, and is similar to findings in other studies. In stating that all of the patients in the two groups had good visual acuity, i.e. 6/9 or better, and were not known to have any other ocular pathology than cataract, the implication was that none of these patients had any macular pathology, and therefore were all felt to have the potential to achieve 6/9 or better vision after their aphakic correction by whichever means.
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The reasons why seven patients had not attained the visual acuity of 6/12 after 6 months in the epikeratophakia group, were not presented since these patients are all expected to attain such a visual acuity in due course. It is simply a reflection of this technique that they have not done so at this stage. The quoted value of 81% of lenticules produced, being within three dioptres of their predicted correction, is similar to values presented by other workers, and may well be as accurate as this technique will allow. It is fully appreciated that this compares poorly with the precision of modern intraocular lens calculation, and this is clearly a factor which must be considered in the decision as to which technique should be used to correct aphakic patients for whom either epikeratophakia or secondary lens implantation would be suitable.