Intravitreal dislocation of crystalline lens fragments is an infrequent yet serious intraoperative complication of cataract surgery in general and during phacoemulsification in particular. Retained lens fragments are associated with vision-threatening sequelae, including corneal endothelial failure, glaucoma, uveitis, cystoid macular edema (CME), rhegmatogenous retinal detachment (RRD), and endophthalmitis, which affect virtually every structure of the eye. This complication appears to be relatively more common in the hands of inexperienced surgeons 1,2 such as residents, and is increasing in incidence parallel with the increasing prevalence of phacoemulsification. 3–5
Many retrospective series 3–14 have established the efficacy and safety of pars plana lensectomy and vitrectomy in the management of retained lens fragments, but none of these previous studies was restricted to resident-performed cataract extractions. We report a retrospective series of eyes undergoing pars plana vitrectomy (PPV) for retained lens fragments following exclusively resident-performed cataract surgery in order to identify any potential differences in the incidence of this problem, or in the outcome following management of the condition.
MATERIALS AND METHODS
We retrospectively reviewed the records of all patients undergoing cataract extraction by the ophthalmology residents of Baylor College of Medicine at Ben Taub General Hospital and the Houston Veterans Affairs Medical Center over a 4-year time frame (July/95–June/99). All patients who underwent cataract extraction, followed by pars plana lensectomy and vitrectomy for retained lens fragments, were identified.
The following data were recorded: procedure used for cataract extraction (phacoemulsification, extracapsular cataract extraction [ECCE], or intracapsular cataract extraction [ICCE]); experience level of the cataract surgeon; placement or no placement of an intraocular lens (IOL) (at the original cataract surgery, at the time of PPV, or never placed); type of IOL (anterior-chamber IOL [ACIOL] or posterior-chamber IOL [PCIOL]); development of severe complications following PPV; need for further surgical procedures on the eye; and final best-corrected visual acuity.
There was no standardized protocol with regard to the specific PPV surgical technique, or timing of the surgical procedure. All patients underwent three-port PPV, and following vitrectomy, the lens fragments were removed with either a fragmatome or the vitrector, dependent on the size and composition of the lens fragments. Surgical adjuncts, such as liquid perfluorocarbons, were used as needed. The timing of the vitrectomy procedure was based on factors such as corneal clarity, degree of intraocular inflammation, level of intraocular pressure, and in select cases, the patient’s preference. The vitrectomy was performed by a postdoctoral vitreoretinal fellow or faculty member, or both.
During the follow-up period, all relevant complications and subsequent surgical procedures were recorded. Categoric data were compared using the chi-square test and continuous data were analyzed using the Student’s t test.
A total of 3389 eyes underwent cataract extraction during the period of our study. Of these, 2797 (83%) were planned phacoemulsifications, 583 (17%) were ECCEs, and 9 (0.3%) were planned ICCEs.
A subset of 26 eyes (0.8%) required subsequent pars plana lensectomy and vitrectomy for retained lens fragments. Therefore, the cumulative incidence of this complication was 0.8% (95% confidence interval [CI]: 0.6%–1.2%).
Of these eyes, 20 (77%) had initially undergone phacoemulsification, 5 (19%) had initially undergone planned ECCE, and 1 (4%) had undergone a phacoemulsification that was converted intraoperatively to an ECCE. No eyes with retained lens fragments had initially undergone ICCE. Therefore, the rate of retained lens fragments following phacoemulsification was 21 of 2797 (0.8%, including the 1 converted ECCE) and the rate following planned ECCE was 5 of 583 (0.9%). There was no statistically significant difference between these two rates (P =0.71).
Prior to cataract surgery, 21 eyes (81%) had no identifiable risk factor for retained lens fragments, and 5 eyes (19%) had coexisting ocular morbidity, which might have predisposed them to this complication. The coexisting ocular morbidities were: prior trauma, 2 eyes (8%); pseudoexfoliation, 1 eye (4%); posterior polar cataract, 1 eye (4%); and prior PPV with a damaged posterior capsule, 1 eye (4%).
The cataract surgeon was a 3rd-year resident in 19 (73%) cases and a 2nd-year resident in 7 (27%) cases. The exact numbers of phacoemulsifications and ECCEs performed by the 2nd- and 3rd-year residents during this time period could not be precisely determined by our retrospective review; however, the most accurate estimate is that the 2nd-year residents performed approximately 80% of the ECCEs and 7% of the phacoemulsifications during this time frame. The approximate incidence of retained lens fragments is therefore 1.1% for the 2nd-year residents and 0.7% for the 3rd-year residents. Based on the above noted data, patients of the 2nd-year residents were 1.6 times more likely to develop this complication than patients of the 3rd-year residents; however, this value is not statistically significant (P =0.30).
An IOL was placed at the time of the initial cataract surgery in 17 eyes (65%), at the time of PPV in 5 eyes (19%), and not used in 4 eyes (15%). Of the 17 eyes that received an IOL at the time of the initial cataract surgery, 11 received a ciliary sulcus-supported PCIOL and 6 received a flexible open-loop ACIOL. Of the 5 eyes that received an IOL during the PPV surgery, 4 received an ACIOL and 1 received a ciliary sulcus-sutured PCIOL.
No eye in this series presented with a retained lens fragment and concurrent RRD or endophthalmitis. The PPV followed the cataract surgery by a median of 6 days (range: 1–77). Fifteen of the 16 eyes (94%) underwent PPV within 13 days of the cataract surgery.
One or more vision-threatening events developed in 19 eyes (73%). The most frequent complication was CME (8 eyes, 31%). In patients with diabetes mellitus, an attempt was made to distinguish pseudophakic CME from diabetic macular edema (DME), recognizing that this distinction can often be quite difficult even when using both clinical and fluorescein angiographic criteria. Pseudophakic CME developed in 5 eyes (19%), DME in 2 eyes (8%) and combined CME/DME in 1 eye (4%). Other noted complications included the following: RRD (6 eyes, 23%), transient choroidal detachment (4 eyes, 15%), endophthalmitis (2 eyes, 8%), neovascular glaucoma (2 eyes, 8%), and aphakic or pseudophakic bullous keratopathy (2 eyes, 8%).
One or a combination of the following additional surgical procedures was performed on 9 eyes (35%): repeat PPV (4 eyes, 15%), laser photocoagulation of diabetic macular edema (4 eyes, 15%), Nd:YAG vitreolysis (1 eye, 4%), and retinal and cyclocryotherapy (1 eye, 4%).
Follow-up at 6 months was available for 16 eyes. Median best-corrected visual acuity was 20/160 (range: 20/20 to no light perception). Five eyes (31%) were 20/40 or better, 4 eyes (25%) were between 20/50 and 20/160, and 7 eyes (44%) were 20/200 or worse. The etiologies for limited visual outcome (i.e., worse than 20/200) were RRD in 3 eyes (12%), CME in 3 eyes (12%), and combined pseudophakic bullous keratopathy and neovascular glaucoma in 1 eye (4%).
Of the 5 eyes with good (20/40 or better) visual outcomes at 6 months, the median time elapsed between cataract surgery and PPV was 6 days (range: 2–13). Of the 11 eyes with poorer (20/50 or worse) visual outcomes at 6 months, the median time elapsed between cataract surgery and PPV was 7 days (range: 1–65). There was no statistically significant difference in the time elapsed between these two groups (P =0.73).
Over a 4-year period (07/95–06/99), the residents of Baylor College of Medicine performed 3389 cataract extractions at Baylor’s two teaching hospitals. Retained lens fragments were seen in 26 cases (0.8%, 95% CI: 0.6%–1.2%), which is consistent with previously published data.
Many series of resident-performed cataract extractions, particularly in the prephacoemulsification era, reported no cases of retained lens fragments. 15–19 The rate of this complication among surgeons in training, however, appears to be in the range of 0.5%–0.8%. 20–22 In comparison, Fung 2 presented a rate of 0.8% of his own cases, identical to the rate reported by Mathai and Thomas, 14 in a series split between experienced surgeons and residents. The rate of retained lens fragments following cataract surgery performed by the faculty of Baylor College of Medicine during this time period could not be determined by our retrospective analysis.
Most of the eyes in our series (81%) developed retained lens fragments during phacoemulsification. This skew towards phacoemulsification is more pronounced than it is in prior series, 4,6,8 in which only 25% to 71% of retained lens fragments were seen following phacoemulsification, and reflects the increasing trend toward this procedure in general. In fact, most series in the literature 3,5,7,10,12–14 include only phacoemulsifications.
These data do not necessarily imply that phacoemulsification is a more hazardous procedure than ECCE or ICCE, yet it is generally accepted that phacoemulsification is more technically demanding than either ECCE or ICCE. We report no statistically significant difference (P =0.71) between the rates of retained lens fragments following ECCE (0.9%) and phacoemulsfication (0.8%). This may be due to at least three factors. First, many surgeons prefer ECCE for cases judged to be at higher risk for possible lens subluxation (see below). Second, at our institution, junior residents perform most (80%) of the ECCEs, whereas the senior residents perform the majority (93%) of the phacoemulsifications; the less experienced surgeons, performing most of the ECCEs, might be expected to develop a relatively higher rate of complications. Third, at our institution, the residents performed almost 5 times as many phacoemulsifications as ECCEs; this relatively lesser experience with ECCE might translate into a relatively lower skill level, which could account for the similar complication rates.
We attempted to identify any pre-existing conditions that might have predisposed towards lens subluxation. Using multiple logistic regression analysis, the following factors have been identified to significantly increase the risk of vitreous loss during ECCE: glaucoma, pseudoexfoliation, systemic hypertension, traumatic cataract, and surgeon’s inexperience. 23 We identified antecedent trauma or pseudoexfoliation in 3 (11%) eyes. Furthermore, all patients in this series were operated on by relatively inexperienced cataract surgeons. As noted previously, the 2nd-year residents were 1.6 times more likely to experience a retained lens fragment than the 3rd-year residents, although this was not statistically significant (P =0.30).
In this series, 65% of the eyes referred with retained lens fragments received an IOL during the initial cataract surgery, which is within the range (28%–83%) reported in previous series. 3,4,8,10,13 There appears to be a trend toward implanting IOLs in eyes undergoing complicated cataract surgery; earlier series 4,8 reported only 28% to 52% of eyes received IOLs during the initial procedure, whereas later series 3,10,13 reported a rate of 68% to 83%.
We report that the two most visually significant postvitrectomy complications were CME and RRD. These complications were the two most frequent significant adverse events following PPV for retained lens fragments; the indications for the two most frequently performed additional procedures following PPV (respectively, laser photocoagulation for DME and repeat PPV for RRD); and the two most common etiologies for a limited visual outcome. Both CME and RRD were more frequent in this series than in most previous reports.
CME developed in 31% of all eyes requiring PPV in this series. The rate of pseudophakic CME (including the 1 eye with combined CME/DME) was 23%. The rate of severe CME, with vision reduced to 20/200 or worse, was 8% (including the 1 eye with combined CME/DME). Other series 6,8,11,13,14 report overall CME rates of 8% to 56% and “severe” forms of CME (i.e., vision worse than 20/200 or 20/400) in 3% to 5% of cases. 3,4,10 Similarly, in our series, postvitrectomy RRD developed in 23% of all vitrectomized eyes, which is towards the higher end of the range of 3% to 36% reported in prior series. 3,4,6,7,8,10–14
In our series, 16 of 26 patients (62%) were available for follow-up at 6 months following PPV. Of these, 31% achieved vision of 20/40 or better, 25% were between 20/50 and 20/160, and 44% were 20/200 or worse. Prior series 3–7,9–14 reported that 9% to 89% of eyes achieved vision of 20/40 or better, and 11% to 37% had a final vision of 20/200 or worse. Lengths of follow-up differ among these prior studies, but the relatively poorer visual outcomes presented here are consistent with the relatively higher complication rates (particularly CME and RRD) noted in our series of patients. The reasons for the more limited visual results, as compared to prior series, are probably multifactorial but are likely related to the fact that all of these cases initially received operations performed by residents with varying degrees of surgical experience.
The PPVs were performed by postdoctoral fellows or faculty members, or both, at the same hospitals, and most of the postoperative follow-up was performed by the residents. This is in contrast to the previously published reports, which were largely series of patients cared for by full-time faculty members at tertiary referral centers. Due to the retrospective nature of this series, it could not be determined with certainty which PPVs were performed by faculty members themselves, by fellows with faculty supervision, or by fellows without faculty supervision.
The timing of vitrectomy for retained lens fragments has been debated in the literature. Some authors have reported that early intervention (usually defined as within 1–3 weeks of cataract surgery) correlates with better final visual outcome 9,13 or decreased long-term risks of glaucoma. 8 However, numerous other studies, 3–7,10–12 found no advantage to earlier surgery. We report no statistically significant difference in timing of vitrectomy between patients achieving a good (20/40 or better) visual outcome versus those achieving a poorer outcome (P =0.73). We concur with the recommendation to delay PPV whenever possible, until corneal edema subsides and intraocular pressure normalizes. 24
This study highlights certain points. First, although most retained lens fragments occur during phacoemulsification, this complication may develop during planned or converted ECCE. Second, the two major complications that require postoperative monitoring are CME and RRD. These were, in our series, the most common adverse events to occur in the postoperative period, the most common indications requiring further surgical intervention, and the most common etiologies of a limited visual outcome.
In summary, retained lens fragments, particularly among resident-performed cataract extractions, remain an infrequent yet potentially serious complication, with a guarded visual outcome. Although the frequency of lens fragment loss during cataract extraction was comparable to that of previously published studies, a slightly higher number of patients in our study developed CME and RRD, which ultimately limited visual recovery.
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