Purpose
To examine surgical outcomes in patients with retinitis pigmentosa (RP) undergoing phacoemulsification cataract extraction.
Design
Retrospective observational case series.
Patients and Methods
In this single-institution study of consecutive RP patients who underwent phacoemulsification cataract extraction and intraocular lens implantation by a single surgeon between 2002 and 2012, preoperative, intraoperative, and postoperative records were analyzed with attention to best-corrected visual acuity (BCVA), lens and zonular status, capsular tension ring use, incidence of posterior capsular opacification and neodymium-doped yttrium-aluminum-garnet (YAG) laser capsulotomy, and surgical complications.
Results
Eighty eyes of 47 RP patients (21 male) underwent cataract surgery during the study period at an average age of 48.9 years (range, 31-78 years). Mean follow-up time was 23.3 months (range, 1 day – 95 months). Posterior subcapsular cataracts were present in 97.5% of patients. Mean BCVA improved from 20/340 (logarithm of the minimal angle of resolution [logMAR] 1.23) to 20/129 (0.81) within 3 months of surgery, P < .0001. Eyes with a preoperative vision of 20/40 to 20/200 (47 eyes) improved from a mean of 20/81 (logMAR 0.61) preoperatively to 20/43 (0.33), P < .0001, postoperatively. Posterior capsule opacification occurred in 66 eyes (82.5%), and 42 eyes (52.5%) underwent a YAG laser capsulotomy at a mean of 10.8 months after surgery. Fifteen eyes (18.8%) of 10 patients (21.3%) had signs of phacodonesis (3 eyes noted preoperatively, 8 intraoperatively, and 4 postoperatively). One patient had bilateral dislocated in-the-bag intraocular lenses at 5.5 years and 6 years after surgery.
Conclusion
Cataract surgery yields significantly improved Snellen visual acuity in a majority of RP patients with a preoperative vision of 20/200 or better. Conversely, patients with a preoperative visual acuity of 20/400 or worse generally have more limited objective improvements, likely because of macular involvement, but usually report noticeable subjective improvement. A high prevalence of zonular instability is seen in RP patients undergoing cataract extraction. It is therefore important to conduct a careful preoperative assessment of lens stability with preparation for adjunctive methods that augment intraoperative and postoperative lens stabilization.
Retinitis pigmentosa (RP), the most common inherited cause of retinal degeneration, is a heterogenous group of disorders that feature progressive rod-cone dystrophy, retinal vessel attenuation, bone-spicule pigmentary change, and pale appearance of the optic nerve. Global prevalence of RP has been estimated to be 1 in 4000, affecting more than 1 million individuals. Approximately 20% to 30% of RP patients also have associated nonocular disease, with Usher syndrome (RP with hearing loss and vestibular dysfunction) being the most common variant. One known complication of all hereditary forms of RP is the formation of a posterior subcapsular cataract (PSC). PSC development in the general population is rare and is estimated to occur in only 2.1% of individuals 52 to 85 years old ; however, studies have shown that 50% of RP patients develop PSC, beginning earlier than those with age-related cataracts. Fishman and associates have shown a 41% to 90% probability of PSC formation by age 40, with probabilities reaching over 80% by age 60 for many types of RP.
The characteristic visual disturbances of RP patients are a loss of peripheral visual field, corresponding to progressive peripheral retinal degeneration, and nyctalopia. The superimposition of a PSC over their only remaining visual field may not only cause severe visual dysfunction out of proportion to its appearance, but may also exacerbate glare symptoms, especially at night. Both subjective and objective improvements in postoperative acuity have been reported with cataract surgery in RP patients, albeit with unchanged postoperative visual fields.
Visual outcomes can be difficult to predict when both lenticular and retinal pathologies exist. Further, surgery in the RP population poses risks because of complications of postoperative posterior capsule opacification, aggressive anterior capsule contraction, and zonular weakness resulting in spontaneous lens dislocations. The cause of this latter phenomenon is unknown and a paucity of literature exists regarding its prevalence in this surgical population. For these reasons, we reviewed our experience with cataract extraction in a large group of RP patients with special attention to the outcomes and complications of surgical intervention.
Patients and Methods
This retrospective observational case series was in compliance with the Health Insurance Portability and Accountability Act (HIPAA), was approved by the Institutional Review Board at the University of Illinois at Chicago.
In this single-institution study, medical records of consecutive RP patients who underwent phacoemulsification cataract extraction and intraocular lens (IOL) implantation by a single surgeon (E.Y.T.) between March 2002 and May 2012 were reviewed. Diagnosis of RP was confirmed by 2 retinal specialists via clinical history, physical examination, electrophysiologic testing, and/or genetic analysis. Inheritance pattern of RP, baseline and postoperative Snellen best-corrected visual acuity (BCVA) and zonule status, surgical technique including use of capsular tension rings, and other complications, including development of posterior capsular opacification (PCO) and need for neodymium-doped yttrium-aluminum-garnet (YAG) laser capsulotomy, were recorded. Grading of PSC was based on the Lens Opacification Classification System III. Patients with clinical evidence of coexisting pseudoexfoliation syndrome were excluded from this study.
Statistical Analysis
Snellen BCVA was converted to the logarithm of the minimal angle of resolution (logMAR) scale for data analysis. Student 2-tailed, paired t tests and a Kaplan-Meier survival curve were generated using Microsoft Excel 2007 software. A P value calculated to be less than .05 was considered statistically significant. Given a wide range of preoperative BCVA, subgroup analysis of eyes that were worse than or equal to 20/400, between 20/40 and 20/200, and between 20/20 and 20/30 was also performed.
Results
Demographics
Eighty eyes of 47 patients (21 male) with variable inheritance patterns of RP (including 9 patients with Usher syndrome) were studied. One patient was excluded from the study because of coexistence of pseudoexfoliation. Average age at surgery was 48.9 years (range, 31-78 years), with a mean follow-up time of 23.3 months (range, 1 day – 95 months).
Visual Acuity
Peak postoperative BCVA was achieved within 3 months of surgery for a majority of patients. As shown in Table 1 , mean preoperative BCVA (with the exception of 2 eyes, which were light perception before surgery and not assigned a logMAR value ) improved from 20/340 (logMAR 1.23, standard deviation [SD] 0.99) to 20/129 (0.81, 0.87), P < .0001. Postoperative BCVA improved in 70 eyes (87.5%), remained stable within the same line on the Snellen chart in 8 eyes (10%), and worsened by 1 line on the Snellen chart in 2 eyes (2.5%). The 2 eyes with worsened acuity came from the same patient and changed from 20/50 to 20/60 postoperatively, with no documentation of cystoid macular edema (CME). Eyes with a preoperative BCVA of 20/40 to 20/200 (47 eyes, 58.8%) improved from a mean of 20/81 (logMAR 0.60, SD 0.24) to 20/43 (0.33, 0.22), P < .0001.
| Subgroup | N | Mean Age at Surgery (y) | Mean Preoperative BCVA | Mean Postoperative BCVA (Within 3 Months) | P Value a |
|---|---|---|---|---|---|
| 20/400 and worse | 30 | 49.77 | CF 10 in b (logMAR = 2.39, SD = 0.94) | 20/800 (logMAR = 1.63, SD = 0.94) | <.0001 |
| 20/40 to 20/200 | 47 | 48.58 | 20/81 (logMAR = 0.61, SD = 0.24) | 20/43 (logMAR = 0.33, SD = 0.22) | <.0001 |
| 20/20 to 20/30 | 3 | 46.67 | 20/30 (logMAR = 0.17, SD = 0.08) | 20/23 (logMAR = 0.06, SD = 0.03) | .07 |
| Total | 80 | 48.88 | 20/340 (logMAR = 1.23, SD = 0.99) | 20/129 (logMAR = 0.81, SD = 0.87) | <.0001 |
a Student paired, 2-tailed t test.
b Two eyes were light-perception before surgery and were not assigned a logMAR value.
Of note, nearly every patient in this series reported a subjective improvement in function after surgery, although this claim was not systematically evaluated.
Cataract Severity
Posterior subcapsular cataracts were present in 97.5% of the patients in this study, with 67 eyes having PSC grades based on Lens Opacification Classification System III. Table 2 shows the visual outcomes of patients with different PSC grades. After surgery, a mean logMAR improvement of 0.38 was seen in the 1-1.9+ PSC group, 0.39 in the 2-2.9+ PSC group, and 0.65 in the 3-3.9+ PSC group. All patients were referred for cataract extraction and operated on prior to the development of 4+ PSC.
| PSC | N | Mean Age at Surgery (y) | Mean Preoperative BCVA | LogMAR | Mean Postoperative BCVA (Within 3 Months) | LogMAR | LogMAR Improvement |
|---|---|---|---|---|---|---|---|
| <1+ | 1 | 60 | HM | 3 | 20/60 | 0.48 | 2.52 |
| 1-1.9+ | 17 | 53.18 | 20/750 | 1.57 | 20/300 | 1.20 | 0.37 |
| 2-2.9+ | 34 | 48.77 | 20/200 | 0.97 | 20/75 | 0.58 | 0.39 |
| 3-3.9+ | 15 | 43.93 | 20/400 | 1.32 | 20/100 | 0.66 | 0.66 |
| 4+ | 0 |
a Grading of PSC was based on the Lens Opacification Classification System III.
Posterior Capsule Opacification
Sixty-six eyes in the study (82.5%) developed some level of PCO, and 42 eyes (52.5%) required a YAG posterior capsulotomy at an average of 10.8 months after surgery. Fifteen patients in our study had less than 3 months of follow-up. A Kaplan-Meier survival curve was created to better describe the development of significant PCO and need for YAG capsulotomy. The curve, shown in the Figure , illustrates the high occurrence of YAG capsulotomy in RP patients after cataract extraction, with the majority of patients requiring it within a year of surgery.
Phacodonesis
Fifteen eyes (18.8%) of 10 patients (21.3%) showed signs of phacodonesis or pseudophacodonesis.
As illustrated in Table 3 , 3 eyes (Patients A, B) showed signs of phacodonesis on preoperative examination; a capsular tension ring (CTR) was used in all instances without complication.
| Eye | Pt | Sex | RP Type | Age at Surgery (y) | PSC | Preoperative BCVA | Final BCVA | Phacodonesis | CTR | Complications |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | A | M | — | 40 | 3+ | HM | CF 0.5 ft | Preoperative | Y | None to date |
| 2 | B | F | — | 55 | 3+ | HM | 20/200 | Preoperative | Y | None to date |
| 3 | B | F | — | 55 | 3+ | 20/200 | 20/200 | Preoperative | Y | None to date |
| 4 | C | M | A.R. | 50 | 3+ | HM | CF 1′ | Intraoperative | Y | None to date |
| 5 | D | M | Type 2 Usher | 48 | 3+ | 20/70 | 20/50 | Intraoperative | N | Pseudophacodonesis/iridodonesis noted 44 months after surgery |
| 6 | E | F | — | 61 | — | LP | CF 1.5 ft | Intraoperative | Y | None to date |
| 7 | F | M | — | 76 | 2+ | 20/200 | 20/60 | Intraoperative | N | None to date |
| 8 | G | F | — | 50 | 3+ | 20/200 | 20/70 | Intraoperative | Y | Lens subluxated after CTR placement causing vitreous loss; ACIOL placed |
| 9 | G | F | — | 51 | 3+ | 20/200 | 20/60 | Intraoperative | Y | None to date |
| 10 | H | F | Isolated | 60 | Trace | HM | 20/60 | Intraoperative | Y | None to date |
| 11 | I | M | A.D. | 60 | 1.5+ | CF 2 ft | 20/400 | Intraoperative | Y | Subluxated IOL 6 years after surgery |
| 12 | H | F | Isolated | 59 | 2+ | CF 1 ft | 20/30 | Postoperative | N | Pseudophacodonesis noted 1 week after surgery |
| 13 | I | M | A.D. | 61 | 2+ | 20/400 | 20/400 | Postoperative | N | Subluxated IOL 5.5 years after surgery |
| 14 | J | F | Type 1 Usher | 43 | 3+ | 20/80 | 20/30 | Postoperative | N | Pseudophacodonesis noted 2 weeks after surgery |
| 15 | J | F | Type 1 Usher | 43 | 2.5+ | 20/200 | 20/40 | Postoperative | N | Pseudophacodonesis noted 1 month after surgery |
Eight eyes were found to have zonular instability intraoperatively. One eye (Patient G) had vitreous loss after insertion of a CTR, and an anterior chamber intraocular lens (ACIOL) was placed. Later, the patient’s fellow eye was also found to have phacodonesis intraoperatively; to minimize zonular stress, the lens was prolapsed out of the bag and removed with a chopping technique, and a CTR was placed without complication. Of the remaining patients with intraoperative phacodonesis, 3 received a CTR (Patients C, E, H) and 2 did not (Patients D, F). Patient D was noted to have visually insignificant pseudophacodonesis and iridodonesis 44 months after surgery. Finally, Patient I received a CTR in 1 eye because of mild intraoperative zonular instability. Although the CTR was placed, Patient I ultimately developed an in-the-bag dislocation 6 years after surgery, requiring a posterior vitrectomy, IOL/CTR explant, and placement of an ACIOL.
Of the 4 eyes that first showed signs of zonular weakness postoperatively, 1 was of Patient I, who ultimately developed bilateral in-the-bag dislocations. Dislocation of this lens occurred at 5.5 years after surgery (compared to 6 years in the eye that received a CTR), and repair was done via scleral fixation. The remaining 3 eyes (Patients H, J) showed signs of pseudophacodonesis at 1 week, 2 weeks, and 1 month after surgery, without further complication to date (52-62 months to date).
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