Surgical outcomes following retropupillary iris claw intraocular lens implantation in aphakic patients

INTRODUCTION

Cataract extraction surgery followed by implantation of a standard in-the-bag intraocular lens (IOL) is one of the most commonly performed ophthalmic surgical procedures worldwide. The most physiological location of placement of an IOL is inside the capsular bag. Loss of the posterior capsule and/or ciliary zonules due to a surgical complication/congenital weakness of zonules/trauma results in inadequate support for the implantation of a standard in-the-bag IOL and subsequent aphakia. Aphakia is a commonly encountered challenge for an ophthalmologist. The options for aphakia treatment include spectacle correction, contact lenses and surgical correction. While prescribing spectacles for aphakia, many problems are encountered, such as distortion, magnification, limitation of the visual field and cosmetically unacceptable appearance of large glasses. Prolonged contact lens usage poses a variety of challenges, which can be broadly classified into infectious and non-infectious. Non-infectious complications due to long-term contact lens usage include corneal abrasion, corneal abscess, limbal vascularisation, marked decentration of the lens and persistent punctate epithelial erosions. Infectious complications which may occur are blepharitis, conjunctivitis and keratoconjunctivitis (with or without ulceration).^[1] Surgical correction of aphakia includes scleral-fixated IOL (SFIOL), angle-supported anterior chamber IOL (ACIOL) and iris-claw IOL (ICIOL), which can either be fixed in front of or behind the iris. Retropupillary fixation of ICIOL preserves the anatomy of the anterior segment. Multiple studies have compared the efficacy and safety of secondary IOLs. Despite their technical complexity, SFIOLs offer several advantages over the ACIOLs by providing a more physiological lens position with proximity to the nodal point, reducing risks of corneal endothelial damage, chronic inflammation, pupillary block and glaucoma, while ensuring improved long-term stability and minimising visual distortions. SFIOLs can be implanted through sutured and sutureless techniques.^[1] Long-term studies involving retropupillary ICIOL have shown reduced incidence of anterior segment complications such as glaucoma and corneal decompensation as compared to ACIOLs.^[2,3] However, very few studies have taken into account the change in corneal endothelium status due to the secondary IOL implantation. This study aims to evaluate the post-operative outcomes in terms of best corrected visual acuity (BCVA), intraocular pressure (IOP), corneal endothelium status and any complications following retropupillary implantation of ICIOLs in primary or secondary aphakia.

MATERIALS AND METHODS

This was a prospective interventional study conducted at a tertiary care referral hospital of western India (from 1 January 2023 to 31 August 2024). A prior approval of the Institutional Ethics Committee (letter no. 02/2023 dated 04 August 2023) was taken and the study was carried out after obtaining proper written consent from the patient, respecting the tenets of the Declaration of Helsinki. Patients in the age group 18–85 years satisfying the inclusion criteria were included in the study. The inclusion criteria were aphakic patients secondary to previous complicated cataract surgery, congenital or traumatic/subluxated lens preventing intraoperative posterior chamber intraocular lens (PC IOL) implantation and intraoperative cataract surgery complications preventing PC IOL implantation. Exclusion criteria were patients with pre-existing corneal pathologies and conditions affecting IOP or the procedure of applanation tonometry, posterior segment and/or other pathologies likely to affect BCVA, unwilling to participate in the study and unwilling to come for follow-ups as advised.

The pre-operative assessments included BCVA on Snellen’s chart (converted to the logarithm of the minimum angle of the resolution equivalents [LogMar]), slit-lamp examination, IOP measurement by Goldmann applanation tonometer, fundus evaluation by indirect and direct ophthalmoscope and corneal endothelium evaluation by TOPCON corporation (TOPCON) specular microscope. The IOL power was calculated using optical biometry (IOLmaster 500, Zeiss). Whenever optical biometry was not possible, a standard conventional A-Scan biometry was employed to measure the axial length which was then fed into the IOLmaster to calculate the IOL power. IOL power was calculated with the sanders retzlaff kraff theoretical (SRK-T), Barrett universal and Haigis formula as applicable. The iris claw lens from Lensai Ophthalmic Private Limited (Bi-convex Polymethyl Methacrylate IOL with 5.40 mm optic and 8.50 mm overall diameter) was used with anterior A constant of 115 and posterior A constant of 117.4. Iris claw lens implantation was done under peribulbar anaesthesia by a single surgeon by opening or enlarging the previous corneo-scleral tunnel and or incision or by making a new self-sealing sclerocorneal tunnel incision in the superior aspect. Two paracentesis openings 90° away from the main incision were made at 3 and 9 o’clock, respectively. After performing adequate anterior vitrectomy (43 eyes underwent primary anterior vitrectomy), if necessary, the iris claw lens, held using the special lens holding forceps, was introduced from the main incision and the claw haptics were tucked behind the iris sequentially using a spatula guided through the side ports. Intraoperative miosis was achieved using intracameral injection of pilocarpine (0.5% weight/volume). A surgical peripheral iridectomy was made at 12 o’clock. Viscosurgical devices were used to deepen or maintain the anterior chamber and protect the endothelium as and when needed. Sutures were taken using 10-0 nonabsorbable monofilament nylon as and when required. A subconjunctival injection of gentamicin and dexamethasone 0.5cc was given at the end of the procedure. Patients were started on topical moxifloxacin eye drops (0.5%w/v) 6 times a day, prednisolone acetate (1% w/v) 6 times a day, and IOP lowering agents (timolol maleate eye drops [0.5% w/v] twice a day) from post-operative day (POD) 1.

The primary outcome in terms of BCVA was assessed at POD 1, 1 week, 1 month, 3 months and 6 months. Patients were also evaluated for any active ocular complaints, IOL stability, corneal endothelium status (endothelial cell count and corneal thickness using specular microscope), IOP, complications and for the need for any intervention at all visits. All the collected data as described above were tested using appropriate statistical tests (paired t-test) and analysed using International business machines (IBM) Statistical Package for the Social Sciences Statistics for Windows, Version 20.0. Parametric tests were used according to the distribution. P < 0.05 was considered statistically significant.

RESULTS

Data from 50 eyes of 47 patients satisfying the enrolment criteria were statistically analysed. The most common aetiology of aphakia in our study was aphakia after cataract surgery (33 patients [66%]) where primary IOL implantation was not possible. The duration of aphakia was <6 months for 33 patients, 6 months to 1 year for 7 patients and more than 1 year for 6 patients. Other aetiologies included congenital subluxation of crystalline lens (13 eyes [26%]) and traumatic subluxation (4 eyes [8%]). The presenting BCVA ranged from hand movement present (HM)+ till 6/6 (with correction). Most of the eyes in our study (24) had pre-operative BCVA correctable till 6/6 [Table 1-4, provided in supplementary link].

The trend of BCVA from pre-operative to the end of the study showed a significant upward trend, with most of the patients attaining a significant improvement in BCVA.

IOP showed a spike at POD 1 week with a gradual reduction over subsequent follow-up visits [Table 2]. At the end of the study period (POD 6 months), majority of the eyes (37) demonstrated only a 0–2% increase in corneal thickness as compared to the pre-operative value [Table 3].

The mean corneal endothelial cell density (ECD) at the beginning of the study period was 2216 cells/mm² (range of 912–3451 cells/mm²). Majority of eyes (37) demonstrated a reduction in ECD of <10% over the course of the study period. Only two eyes had a reduction in ECD of more than 30% whereas 10 eyes demonstrated a reduction in CD of 10–30%. At the end of the study period, the mean CD was found to be 2022.64 cells/mm² (range 616–3510 cells/mm²) [Table 4].

A P = 0.02 (<0.05) denotes that this difference was statistically significant.

Over the duration of the study period, 24 (48%) eyes developed complications. The most common complication was pupil distortion-reported in 9 eyes. Five eyes (20%) had pigment dispersion over the IOL. Other complications noted were retinal detachment (3 eyes), ocular hypertension (3 eyes), iris atrophy (3 eyes) and macular oedema (1 eye). One eye developed macular oedema, which was treated with subtenon injection of triamcinolone acetonide (0.5 mL of 40 mg/mL), one eye developed vitreomacular traction with the development of epiretinal membrane, which was managed with pars plana vitrectomy and epiretinal membrane peeling and one eye developed retinal detachment. This patient refused to undergo any further intervention.

DISCUSSION

An insufficient posterior capsular or ciliary zonular support makes it unfeasible to implant a conventional posterior chamber IOL. Secondary IOL implantation, in a case of loss of capsular or zonular support, includes angle-supported ACIOL, scleral-supported IOL and iris-claw (prepupillary and retropupillary) IOL.^[3] The final choice of the type of IOL depends on the cause of aphakia, status of iris diaphragm, integrity of posterior segment, presence of vitreous in the anterior segment, availability of pars plana vitrectomy, presence of other ocular abnormalities and skill of the surgeon.^[3,4] Angle-supported ACIOL implantation, although technically easier, has been associated with several complications such as deformed pupil, endothelial decompensation and bullous keratopathy.^[5] A study by Baykara et al. concluded that retropupillary fixation of an ICIOL has the advantages of true posterior chamber implantation, resulting in a deeper anterior chamber, greater distance between corneal endothelium and IOL, and a more physiological implantation of the IOL.^[6] In a study conducted by Madhivanan et al. more than 50% of surgeons preferred implanting a retropupillary ICIOL in aphakic patients.^[7] In our study, the mean LogMar BCVA improved from 1.16426 (pre-operative) to 0.40642 by the end of the study period. This final outcome was comparable to another study conducted by Mahajan and Datti, which reported a post-operative mean LogMar BCVA of 0.41 for ICIOL implantation.^[8] Al-Dwairi et al. reported a change in LogMar BCVA of −0.845, which was comparable to our study.^[9] Three eyes (6%) in our study developed ocular hypertension, which was subsequently controlled by topical IOP lowering agents. This result was comparable to a study by Schallenberg et al.^[10] In our study, there has been a reduction in mean IOP over the course of the study period, which correlates with a study by Choi et al., who reported that the post-operative mean IOP was significantly lower than the pre-operative IOP at 1-month follow-up postoperatively and remained stable thereafter.^[11] Baykara et al. showed that the anatomic characteristics of the anterior segment are preserved after retropupillary IC IOL implantation and that there were no cases of peripheral anterior synechiae even 24 months after the surgery, which also indicates that there is a low risk of chronic angle closure after IC IOL implantation.^[6] The rise in IOP can be attributed to obstruction to aqueous outflow by the lens, persistent trabeculitis, or persistent inflammation of iris tissue from the IOL. In our study, pigment dispersion was noted in 5 patients (10%). Pigment dispersion occurs due to the rubbing of the lens with the pigmented iris epithelium. Forlini et al.reported only three cases (out of 320) of pigment dispersion due to the vaulted design of the Artisan aphakic lens and its inverted position, providing adequate space between the iris pigmented epithelium and the optical zone of the lens.^[12] Even Rijneveld et al. reported pigment dispersion as a rare complication in their study.^[13] Pupil distortion was the most common complication seen in our study in 9 patients. This stretching of iris tissue is likely due to asymmetrical fixation of haptic, tight fixation of haptic, or a difference in iris tissue volume that was clamped with both haptics. It was more compared to a similar study conducted by Mahajan and Datti (16.6%).^[8] Baykara et al. reported pupil distortion in only 12.7% of the patients.^[6] A unique feature of our study was the evaluation of corneal thickness and ECD as well. The initial rise in corneal thickness can be attributed to the post-operative corneal oedema, which gradually reduced over subsequent follow-up visits. Majority of the patients in our study reported a reduction in ECD <10%. Chen et al. proposed that the corneal endothelial cell loss may be due to a mechanical irritation between the endothelium and the instruments or the IOL haptics during implantation.^[14] Choi et al. reported that retropupillary fixation of IC IOL resulted in a 16.6% decline in endothelial cell count at the 1-month follow-up postoperatively; however, there was no further reduction until 24 months after the surgery. The authors commented that IOL repositioning and aphakia correction using the retropupillary IC IOL would result in a smaller risk of endothelial injury.^[11] It is the IOL replacement itself that presents a risk for endothelial decompensation since the manoeuvres related to the removal of the dislocated IOL through the scleral tunnel may cause some trauma to the corneal endothelium. Furthermore, ECD decline did not significantly progress after 1 month postoperatively, which may signify that the ECD decline was primarily due to surgical factors related to IOL removal rather than problems of retropupillary ICCIOL per se. In a randomised clinical trial conducted by Kristianslund et al., which studied cases with IOL dislocations for 6 months, an average endothelial cell loss of 10% was observed in patients who underwent IOL replacement with retropupillary IC IOL, whereas a 3% endothelial cell loss was observed in the IOL repositioning group.^[15] Negretti et al. reported that retropupillary IC IOL implantation for correcting aphakia did not significantly decrease endothelial ECD, even in patients who had undergone penetrating keratoplasty for bullous keratopathy.^[16] An increase in corneal thickness was noted in our study during the initial follow-up period, which can be attributed to post-operative stromal oedema. As the inflammation subsided gradually, the oedema also reduced, resulting in a return to pre-operative corneal thickness. Iris atrophy at the enclavation site was noted in 3 of our patients. The mechanism for iris atrophy may be ischemia or mechanical stress on the iris sphincter muscles at the enclavation site.^[14] Gonnermann et al. reported that it occurred in 13.9% of the patients examined, with a mean follow-up duration of 5 months.^[17] Three patients in our study reported retinal detachment. Two of them refused for any further intervention. One patient underwent pars plana vitrectomy with epiretinal membrane peeling under local anaesthesia. Zaleski et al. proposed that the mechanism for the development of retinal detachment is persistent vitreous traction after implantation of an ICIOL. This may occur due to inadequate anterior vitrectomy, which leads to the formation of vitreous traction over the posterior surface of IOL.^[18] Subsequent fibrosis during the healing stage predisposes to detachment.^[18] One patient in our study developed macular oedema, which was treated by subtenon injection of triamcinolone acetate. Mansoori et al. also reported an incidence of cystoid macular oedema (CME) at 4.9%; which was attributed to nucleus drop and or vitreous manipulation during the primary surgery.^[19]

The strength of this study is that it has taken into account the endothelial cell loss encountered due to the surgical technique. Patients having any other disorder which is likely to affect the visual acuity have been excluded; thus, the visual outcome can be directly attributed to the surgery. The limitations of our study have been the absence of a comparison group and a longer follow-up, which could have been beneficial to study the long-term clinical implications and safety of the procedure.

Retropupillary iris claw implantation offers a significant visual rehabilitation to an aphakic patient as majority of patients could attain a BCVA up to 6/6 on Snellen’s chart. No significant elevation in IOP was noted across the study period, and the transient minimal rises were likely due to the associated inflammation of a surgical procedure rather than the IOL itself. Retropupillary position of lens contributes to a minimal reduction in ECD, making it a viable and safe option with respect to the risk of corneal decompensation.

CONCLUSION

Retropupillary iris claw implantation offers a significant visual rehabilitation to an aphakic patient as majority of patients could attain a BCVA uptill 6/6 on Snellen’s chart. No significant elevation in IOP was noted across the study period and the transient minimal rises were likely due to the associated inflammation of a surgical procedure rather than the IOL itself. Retropupillary position of lens contributes to a minimal reduction in endothelial cell density, making it a viable and safe option with respect to the risk of corneal decompensation.