Primary and secondary implantation of scleral-fixated posterior chamber intraocular lenses in adult patients.

PURPOSE: The purpose of this study is to evaluate and to compare the results of primary and secondary scleral-fixated posterior chamber intraocular lens (PCIOL) implantations in adult patients.
MATERIALS AND METHODS: A retrospective analysis of scleral-fixated PCIOLs-implanted during (primary group) or after (secondary group) cataract surgery was performed. The median follow-up time of 96 patients was 6 months (minimum: 6; maximum: 35 months). Outcome measures were indications, corrected distance visual acuity (CDVA), change in visual acuity and complications.
RESULTS: A total of 37 patients (38.5%) had primary implantations and 59 (61.5%) had secondary implantations. Penetrating keratoplasty was combined with secondary implantation in 13 cases. The median post-operative CDVA was 0.5 in decimal notation in both groups (P = 0.576). The CDVA improved by at least one Snellen line or remained unchanged in 35 eyes (94.6%) in the primary group and in 52 eyes (88.1%) in the secondary group (P = 0.263). Eyes with CDVA of 0.5 or higher were 62.2% (n = 23) in the primary group and 67.8% (n = 40) in the secondary group post-operatively (P = 0.066). The difference in early and late complications were not statistically significant between groups (P = 0.637, P = 0.154, respectively). Regarding late complications, 30 eyes (81%) in the primary group and 40 eyes (67.9%) in the secondary group had no complications (P = 0.154).
CONCLUSION: Both primary and secondary scleral-fixated PCIOL implantations can provide favorable visual outcomes with lower complication rates. An important consideration is the appropriate timing for scleral fixation, taking into account the patient's characteristics and the course of the operation.

INTRODUCTION

In the absence of adequate lens capsular support during cataract surgery, the decision should be made whether to perform a primary implantation at the same session or a secondary implantation after a period of time.123 Implantation of an anterior chamber intraocular lens (ACIOL) is associated with a relatively high rate of complications.4567 Several reports concerning scleral-fixated posterior chamber intraocular lenses (PCIOL) have been reported with mostly favorable results.4891011 However, the surgical technique of scleral-fixated PCIOL insertion is more technically demanding.111213 Histological studies of the anterior segment showed that the best position in these eyes is sulcus fixation.1415 The purpose of this study was to compare the outcomes of primary and secondary scleral-fixated PCIOL implantations in adult patients.

MATERIALS AND METHODS

This study was approved by the institutional board. A chart review was performed of the medical records of 96 patients who underwent scleral-fixated PCIOL implantation between April 2004 and September 2009 with follow-up for at least 6 months. A total of 32 patients (33.3%) were females and 64 (66.7%) were men. The median age at the time of implantation was 67 years (minimum [min]: 17 years; maximum [max]: 86 years). The median follow-up was 6 months (min: 6 months; max: 35 months).

The indications for scleral-fixated intraocular lens (IOL) implantation were extensive capsular deficiency precluding safe and stable IOL implantation in the bag or in the sulcus, corneal decompensation due to ACIOL, IOL subluxation, crystalline lens subluxation or contact lens intolerance. Uveitis, endothelial dysfunction corneal dystrophy, retinal hole, subretinal fluid, extensive lattice degeneration or major retinal diseases were contraindications for scleral-fixated PCIOL insertion. The decision for primary or secondary implantation was made according to the type of anesthesia, patient comfort and general medical stability of patient and preference of individual surgeon.

All patients were informed about complications of the procedure and the possible need for future IOL removal or exchange and written informed consent was obtained pre-operatively.

IOL powers were calculated using the Sanders-Retzlaff-Kraff II formula. In primary implantation, the IOL power was adjusted according to the A-constant of the scleral-fixated IOL selected for implantation. The surgical maneuvers used for each surgery have been documented.16 In primary scleral-fixated PCIOL implantation, the corneal incision performed for cataract extraction was used or the wound was enlarged to 8 mm in phacoemulsification cases. In secondary scleral-fixated PCIOL implantation, the conjunctiva was opened and triangular, partial thickness scleral flaps were created at the 8 O’clock and 2 O’clock positions. A superior three-laminar corneal incision was performed and an ocular viscoelastic device was injected into the anterior chamber. In phakic patients, cataract surgery was performed by phacoemulsification, extracapsular or intracapsular extraction. Subluxated IOL were explanted through the anterior incision. Anterior vitrectomy was performed in all cases during the primary scleral-fixated IOL implantation and as warranted, during the secondary implantation with a vitrector. A 10-0 polypropylene suture on curved needles (PC-9; Alcon Laboratories, Inc., Texas, USA) was tied to the eyelets of the haptics of a polymethylmethacrylate lens (CZ 70 BD; Alcon, Fort Worth, Texas, USA). A guide needle (27 gauges) was inserted from the sclera to the ciliary sulcus 0.8-1.0 mm from the limbus while remaining under the flap, measured by a caliper from the corneoscleral limbus and marked by pressing the corresponding arm of the caliper to the sclera. The tip of the fixation needle was engaged in the opening of the guide needle and pulled from ciliary sulcus to exit the eye. The same procedure was performed with the second fixation needle. The IOL was introduced into the eye. By pulling both of the sutures, the haptics were drawn into the ciliary sulcus. The cornea was sutured using 10-0 monofilament nylon suture (Alcon Laboratories Inc., Texas, USA) in a continuous fashion. The polypropylene sutures were tied and left long under the triangular scleral flaps. The scleral flaps and conjunctival incisions were closed using 10-0 monofilament nylon sutures. At the end of the surgery, subconjunctival corticosteroids and antibiotics were injected.

Post-operative examinations were performed at 1 day, 1 week, 4 weeks, 3 months, and 6 months post-operatively. Thereafter, examinations were scheduled at approximately 6-month intervals. Post-operatively, topical antibiotics (four times/day) were used for 2 weeks and corticosteroids (four times/day) were used for 1 month and tapered thereafter. Anti-glaucomatous medications were used when required.

Main outcome measures were age, gender, follow-up time, pre-operative and post-operative corrected distance visual acuity (CDVA), change in visual acuity and complications. Outcome measures (unless noted otherwise) were those obtained at the most recent follow-up examination. Visual acuities were measured and reported in decimal units. Visual acuities were converted to the logarithm of the minimum angle of resolution (logMAR) units for statistical analysis. Visual acuity of counting fingers was converted to 2.00 logMAR and hand motion was converted to 3.00 logMAR.17 No patient had a perception of light with or without projection.

Data analysis was performed using the statistical package for social sciences for Windows software (SPSS version 16.0, SPSS Inc., Chicago, USA). Normality distribution of continuous variables (age, follow-up time, pre-operative and post-operative CDVA), was tested by Kolmogorov-Smirnov test, histogram and P-P plots. As all continuous variables were distributed abnormally, descriptive statistics were demonstrated as median (min-max). Mann-Whitney U test was used to compare the continuous variables between the groups. Categorical variables were presented as frequency (%). Pearson Chi-square test was used to compare the categorical variables between the groups.

RESULTS

The scleral-fixated PCIOL implantation was performed in 37 patients (38.5%) as primary implantation (primary group) and in 59 patients (61.5%) as secondary implantation (secondary group). Penetrating keratoplasty was combined with secondary implantation in 13 cases.

The median age was 69 years (min: 24; max: 86 years) and 67 years (min: 17; max: 85 years) in the primary group and secondary group, respectively (P = 0.89, Mann-Whitney U test). The median follow-up was 6 months in both groups (min: 6; max: 14 months in primary group and min: 6; max: 35 months in secondary group, P = 0.112, Mann-Whitney U test).

Indications for the scleral-fixated PCIOL implantation (lens status) are summarized in Table 1. In the primary group; scleral-fixated PCIOL implantation was performed during the cataract surgery because of posterior capsule complications encountered during extracapsular cataract extraction in 8 eyes (21.6%), phacoemulsification in 15 eyes (40.6%) and subluxation of the crystalline lens in 14 eyes (37.8%). In the secondary group, a total of 39 eyes (66.1%) were aphakic at the time of surgery, with a median aphakic period of 5 months (min: 1 month; max: 60 months). Thirty aphakic eyes (50.8%) had previous complicated phacoemulsification related to posterior capsule rupture or zonular dialyses, 4 aphakic (6.8%) eyes had previous uncomplicated cataract surgery due to congenital cataract and 5 eyes (8.5%) had previous reoperation due to the penetrating ocular injury. Seven eyes (11.9%) had ACIOL-related complications and 13 eyes (22%) had IOL dislocation.

Table 1

Indications for scleral-fixated PCIOL (lens status)

The median pre-operative CDVA was 0.05 (min: Counting fingers; max: 0.6) in the primary group and 0.05 (min: Counting fingers; max: 1.0) in the secondary group, which was statistically different between groups (P < 0.001, Mann-Whitney U test). The median post-operative CDVA was 0.5 (min: Counting fingers; max: 1.0) in the primary group and 0.5 (min: Counting fingers; max: 1.0) in the secondary group, with no statistically significant difference between the groups (P = 0.576, Mann-Whitney U test) [Table 2].

Table 2

Pre-operative and post-operative visual acuities

The CDVA improved at least one Snellen line or stayed unchanged in 35 (94.6%) eyes in the primary group and in 52 (88.1%) eyes in secondary group. The change in visual acuity was not statistically significant between the groups (P = 0.263, Pearson Chi-square test). Visual loss of one or more Snellen lines occurred in 2 (5.4%) eyes (cystoid macular edema sequelae, n = 1; tilted IOL, n = 1) in the primary group and 7 (11.9%) eyes (cystoid macular edema sequelae, n = 3; glaucoma, n = 1; graft failure without rejection, n = 1; tilted IOL, n = 1; bullous keratopathy, n = 1) in the secondary group.

The median (min-max) spherical equivalent was 2.00 D (0-6.00 D) and 1.75 D (0-5.00 D) in the primary and secondary groups respectively (P = 0.121). The median (min-max) cylindrical power was 2.00 D (0-6.00 D) and 2.00 D (0-6.00 D) in the primary and secondary groups respectively (P = 0.885). Patients were divided into three groups according to their CDVAs (0.1 or less, between 0.2-0.4 and 0.5 or more). Regarding these visual acuity categories, the groups were statistically different in the pre-operative period (P < 0.001, Pearson Chi-square test) and they were similar in the post-operative period (P = 0.066, Pearson Chi-square test). Post-operatively, 62.2% (n = 23) of the eyes had CDVA of 0.5 or higher in the primary group while 67.8% (n = 40) of the eyes in the secondary group had CDVA of 0.5 or higher. Non-surgery related causes of CDVA of less than 0.2 were age-related macular degeneration (n = 2), traumatic foveal choroidopathy (n = 3), traumatic partial leukoma (n = 5) and retinitis pigmentosa (n = 1) in the primary group and age-related macular degeneration (n = 4) in the secondary group.

Early and late post-operative complications are listed in Table 3. In the early post-operative period, adverse events occurred in 13 eyes (35.1%) in the primary group and in 17 eyes (28.8%) in the secondary group (P = 0.637, Pearson Chi-square test). Most of these were mild and transient. Elevated intraocular pressure (IOP) occurred in 3 (8.1%) eyes in the primary group and in 11 (18.6%) eyes in the secondary group. Eight eyes (three in the primary group, five in the secondary group) had pre-operative glaucoma. Elevated IOP was transient in six eyes and was controlled by anti-glaucomatous agents in eight eyes (one in primary group, seven in secondary group). No eyes required glaucoma surgery.

Table 3

Pre-operative and post-operative complications

Regarding late complications (at least 1 month post-operatively), 30 eyes (81.0%) in the primary group and 40 eyes (67.9%) in the secondary group had no complications (P = 0.154, Pearson Chi-square test). Cystoid macular edema occurred in 2 eyes (5.4%) in the primary group and in 4 (6.8%) in the secondary group; in four of these eyes (1 in the primary group; 3 in the secondary group), CDVA deteriorated in spite of peri-ocular and topical treatment with corticosteroids. The other surgery-related causes of visual acuity of less than 0.2 were tilted IOL (n = 1) in the primary group; bullous keratopathy (n = 1), glaucoma (n = 1), graft failure without rejection (n = 1) and tilted IOL (n = 1) in the secondary group. No patient had endophthalmitis, hypotony, retinal detachment or spontaneous dislocation of the IOL caused by breakage of the polypropylene sutures during follow-up.

Seven eyes (5.8%) required post-operative surgical intervention. One adult patient underwent grafting with processed human pericardium for exposed polypropylene suture and two penetrating keratoplasty patients underwent re-suturing for a leaking corneal wound. One patient was added to a keratoplasty waiting list due to the bullous keratopathy. Three patients refused further surgery for tilted IOL and graft failure.

All the penetrating keratoplasties were performed in combination with secondary scleral-fixation surgery. Two of these eyes needed re-suturing for leaking corneal wound, two underwent graft rejection reaction and one graft failed without rejection. All the penetrating keratoplasties were performed in combination with secondary scleral-fixation surgery. Two of these eyes needed re-suturing for leaking corneal wound, two underwent graft rejection and one graft failed without rejection. The median (min-max) spherical equivalent was 1.75 D (0-5.00 D) and 2.00 (0-6.00 D) in patients without keratoplasty and with keratoplasty respectively (P = 0.188). The median (min-max) cylindrical power was 2.00 D (0-5.50 D) and 2.50 D (0-6.00 D) in patients without keratoplasty and with keratoplasty respectively (P = 0.078). The median (min-max) post-operative CDVA was 0.5 (counting fingers-1.00) and 0.4 (counting fingers-0.9) respectively, in patients without keratoplasty and with keratoplasty (P = 0.01).

DISCUSSION

PCIOL are the standard of care in current cataract surgery. Ideally, the lens is placed in the capsular bag, which affords stable fixation at a position closest to the nodal point of the eye. However, there will always be instances where in the bag implantation isn’t possible, requiring that the IOL be sutured to the sclera; weakness of the lens zonules in various conditions, trauma and surgical complications during the cataract surgery are just some examples.2 Lack of capsular support is common in aphakic eyes, especially following removal of traumatic cataracts. Trans-scleral suturing of posterior chamber IOL is well-established and a good option in patients with insufficient capsular support or zonular support, either as a primary or secondary implantation. A number of reports on secondary scleral-fixated PCIOL implantation exist in the literature.12181920 However, to the best of our knowledge, primary and secondary scleral-fixated PCIOL implantation has been compared only in one study.21

Posterior capsular rupture with or without vitreous loss is the most common intraoperative complication during the cataract surgery.2223 In the absence of adequate capsular support, the surgeon has to decide whether to perform a primary or secondary implantation. The type of anesthesia, the general medical stability of the patient and compliance, the surgical time spent to fix the complications and the surgeon's experience are factors affecting the decision-making process.

The surgical technique of scleral-fixated PCIOL implantation requires good surgical skills and meticulous intraocular maneuvers, which cannot be performed under stressful conditions and poor patient compliance. The procedure of scleral-fixated PCIOL implantation is associated with prolonged operating times because of time spent for creating scleral flaps, suturing the IOL haptics, vitrectomy and IOL implantation. Additional time is added to the first part (complicated cataract extraction), which can add higher risks for post-operative inflammation associated with cystoid macular edema in primary implantations.21 Besides this, light-induced retinal injury may also be another disadvantage of primary implantation.2425 On the other hand, patients undergoing secondary scleral-fixated PCIOL implantation are presumably a healthier patient group with better visual potential and without inflammation and any ocular sequelae.

Lee et al. reported a statistically significantly higher complication rate in the early post-operative period and less favorable visual outcome in the primary group.21 Contrary to Lee et al.'s study, we found similar complication rates and visual outcomes in primary and secondary groups. The possible causes of higher early and late post-operative complications in the secondary group, although not statistically significant, can be the prolonged operation time during the first surgery due to more challenging intraoperative complications, which can also be the reason for the secondary implantation, combination of penetrating keratoplasty in 13 cases, complicated ACIOL in 7 cases and traumatic background in 5 cases.

Cystoid macular edema was noted to be the most common complication in some series that reported a rate of 5.5-11% in secondary implantations.18212627 In our study, the incidence of cystoid macular edema sequelae was 5.4% in the primary group and 6.8% in the secondary group.

Another important complication was elevated IOP. The groups had similar ratios of pre-operative elevated IOP. In the single study comparing primary and secondary scleral-fixated IOL implantations, glaucoma was reported to be 16.7% and 12.0% after primary and secondary implantations, respectively.21 Sufficient anterior vitrectomy in the primary group could be the reason for the simultaneous scleral-fixated IOL implantation and could prevent the post-operative IOP rise. All patients with elevated IOP were treated medically and glaucoma surgery was not required.

Anterior chamber and vitreous hemorrhages were transient and pupillary distortion did not affect the final visual acuity in any patient. Two patients with CDVA of less than 0.2 due to a tilted IOL refused further surgical intervention to re-center the IOL.

Only one patient developed suture exposure after 37 months in the secondary group and the suture node was covered using processed human pericardium to reduce the risk of “suture wick” endophthalmitis. In this study, we used partial-thickness triangular scleral flaps to cover and protect the suture knots and the polypropylene sutures were tied and left long under the triangular scleral flaps. When the suture ends are left long enough to lie parallel to the sclera, the sharp ends do not cause erosion of the overlying conjunctiva. We think that the low suture exposure rate in our study is related to the protective scleral flaps and the long suture ends.

The groups were similar regarding the median CDVA (P = 0.576) and the change in the CDVA (P = 0.263). These results are comparable to previous studies.1820212428 Surgery-related complications causing visual acuity of less than 0.2 were similar between groups. The CDVA can deteriorate not only due to surgery, but also due to non-surgery-related causes (e.g. pre-operative pathologies, history of trauma or previous complicated surgeries and age-related macular degeneration).

The limitations of this study are its single-center and retrospective nature, variable duration of follow-up, small heterogeneous pre-operative indications. Prospective, randomized trials with longer follow-up are required to identify the safety and efficacy of primary and secondary scleral-fixated PCIOL implantations in homogeneous patient populations.

CONCLUSION

Both primary and secondary scleral-fixated PCIOL implantations can provide favorable visual outcomes with less complication rates in cases with inadequate capsular or zonular support for PCIOL implantation. Poorer visual outcomes are often related to ocular comorbidities associated with the underlying pathology necessitating extracapsular fixation. The important consideration is the appropriate time for scleral fixation while accounting for the characteristics of each patient and the course of each surgery. Although primary implantation has the advantage of a single operation and the avoiding a period of aphakia with poor vision after cataract extraction, secondary implantation can be a logical option in incompatible patients and in prolonged surgeries.