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Clinical features and outcomes of pars plana vitrectomy in patients with retained lens fragments after phacoemulsification

Ho, Shu Fen MRCOphth, FRCS(Glasg); Zaman, Anwar FRCOphth, MA

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Journal of Cataract & Refractive Surgery: December 2007 - Volume 33 - Issue 12 - p 2106-2110
doi: 10.1016/j.jcrs.2007.07.037
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Abstract

A dropped nucleus is one of the most serious complications of phacoemulsification. The incidence ranges between 0.001% and 0.015%.1 Pars plana vitrectomy (PPV) in these patients leads to improved vision and is the procedure of choice. Studies showed that 44% to 71% of patients achieve a visual acuity of 20/40 or better.2–14

Complications associated with vitrectomy include retinal detachment (RD) and cystoid macular edema (CME).10,11,15 The incidence of RD varies from 0% to 45.4% (median 15.9%)2–14 and of CME, from 5% to 22% (median 20%).3,4,8 In our clinical experience, we noted fewer complications after PPV for dropped nuclei than reported in previous studies. Thus, we conducted a review of data of patients who had the procedure at our institution from 2000 to 2006 and compared the results with those in published studies to confirm that modern vitrectomy surgery has better results than surgery that was reported in the 1990s.

PATIENTS AND METHODS

The medical records of consecutive patients who had PPV for posteriorly dislocated lens fragments after phacoemulsification between January 2000 and June 2006 at the Vitreo-Retinal Service, Queen's Medical Centre, were retrospectively reviewed. Eyes with traumatic lens dislocation and spontaneous lens dislocation were not included.

The data collected included demographics, preexisting eye conditions, and details of previous cataract surgery. Visual acuity at presentation, intraocular pressure (IOP), anterior segment findings (eg, corneal edema, anterior uveitis, soft lens matter, visible vitreous) at presentation, and posterior segment findings at presentation were also evaluated. Other parameters included details of the vitreoretinal procedure, including date, interval between phacoemulsification and vitreoretinal surgery; use of ultrasound fragmentation and/or heavy liquids; final visual acuity; and complications during the follow-up period.

Visual acuity was recorded as Snellen values. Visual acuity was categorized as good (6/12 or better), moderate visual loss (6/18 to 6/36), or severe visual loss (6/60 or worse). Raised IOP was defined as IOP greater than 25 mm Hg and severe anterior uveitis as anterior chamber reaction of 3+ cells. Patients were considered to have developed problems with IOP during the follow-up period when the IOP was 25 mm Hg or greater and there was no history of glaucoma or when additional treatment was needed to control IOP in patients with glaucoma. The interval between cataract surgery and PPV was divided into 3 groups: less than 1 week, between 1 week and 1 month, and more than 1 month.

Statistical analysis was performed using SPSS (version 14, SPSS, Inc.). The relationship between anterior vitrectomy and raised IOP was analyzed with the chi-square test. The Spearman's rank correlation test was used to evaluate the relationship between the timing of vitrectomy and the final visual acuity. The null hypothesis was rejected when the P value was 0.05 or less.

RESULTS

Eighty-two patients were identified; 37 were men, and 45 were women. The median age was 78 (range 48 to 85 years). The median follow-up period was 27 months (range 4 months to 4 years).

Of the 82 patients with dropped nuclei, 7 had dense nuclei, 5 had small pupils, 4 had posterior polar cataracts, 4 had vitrectomized eyes, 3 had high myopia (greater than −4.00 diopters), 3 had underlying lens instability, and 2 had pseudoexfoliation. Other preexisting eye conditions included diabetic mellitus (8) and primary open-angle glaucoma (8). No patient was taking tamsulosin hydrochloride (Flomax) or similar medication, and none had intraoperative floppy-iris syndrome.

Visual acuity at presentation was 6/12 or better in 1.2% of eyes, between 6/18 and 6/36 in 14.6%, and 6/60 or worse in 62.2%. Elevated IOP (≥25 mm Hg) occurred in 38 patients (46.3%), corneal edema in 35 (42.7%), severe uveitis in 18 (38.6%), soft lens matter in the anterior chamber in 12 (14.6%), and hypotony in 2 (2.4%). There were 3 cases of vitreous hemorrhage and no cases of preexisting RD.

The mean IOP in patients with an elevated IOP was 40.2 mm Hg ± 10.43 (SD) (median 38 mm Hg; range 25 to 64 mm Hg). More than 95% of cases occurred within the first week after cataract surgery (median 1 day). Of the 38 patients with elevated IOP, 32 (84%) had visible vitreous in the anterior chamber, 18 (47.3%) had increased inflammation, and 12 (32%) had soft lens matter in the anterior chamber.

Patients in whom anterior vitrectomy was performed at the time of cataract surgery had a lower incidence of elevated IOP (36%) than those who did not have anterior vitrectomy (71%) (Table 1). The chi-square test with continuity correction showed that anterior vitrectomy was associated with a statistically significantly lower incidence of elevated IOP (chi square = 7.66, degrees of freedom = 1, P = .006). The type of intraocular lens (IOL) implanted (anterior chamber or posterior chamber) had no statistically significant relationship with elevated IOP (P = .735).

Table 1
Table 1:
Relationship between anterior vitrectomy before referral and raised IOP.

Pars plan vitrectomy was performed at the same time as cataract surgery in 7.3% of the patients. Sixty-six percent had PPV within the first week after surgery; 13.4% between 8 days and 15 days; 1.2% between 22 days and 28 days; 4.9% after 28 days.

During PPV, ultrasound fragmentation was used in 28 eyes (34%) and heavy liquid was used in 11 eyes (13%). An iatrogenic retinal tear was found in 2 patients, who were treated with cryotherapy and gas exchange.

At the last follow-up visit, visual acuity was 6/12 or better in 58.5% of patients, 6/18 to 6/36 in 20.7%, and 6/60 or worse in 14.6%. Table 2 shows the reasons for poor visual acuity. In 12 patients (45%), the cause was preexisting ocular conditions.

Table 2
Table 2:
Primary attributed causes of reduced vision after PPV to retrieve dropped nucleus.

There were few postoperative complications. Glaucoma was found in 6 eyes; CME and RD in 4 eyes (4.9%) each; and worsening of diabetic retinopathy, epiretinal membrane, and postoperative astigmatism in 1 eye (1.2%) each. No patient developed endophthalmitis.

One patient developed RD during the second week after PPV and the other 3 patients developed RD 3 months after PPV (Table 3). Of these patients, 1 had late vitrectomy. No co-variable (eg, nucleus size, IOL type) was statistically significantly associated with RD, although the method of IOL removal approached significance (P value = .059). A comparison of lens fragment removal by ultrasound versus heavy liquid showed neither method was statistically significantly associated with uveitis (P = .454) or elevated IOP (P = .198).

Table 3
Table 3:
Characteristics of patients who developed RD after PPV.

Of the 62 patients having early PPV, 24 (38.7%) had a visual acuity worse than 6/18. After adjusting for preexisting ocular disease, 12 patients (19.3%) had a visual acuity worse than 6/18. The comparable figure for the 4 patients having late vitrectomy were 2 (50.0%) and 0 (0%) (Tables 4, A and B). The Spearman's rank correlation between the timing of PPV and final visual acuity was 0.013 (P = .91).

Table 4A
Table 4A:
Relationship between timing of PPV after phacoemulsification and final visual acuity.
Table 4B
Table 4B:
Relationship between timing of PPV after phacoemulsification and final visual acuity after adjusting for preexisting ocular condition and modifiable condition (thick posterior capsule and patient refused secondary IOL).

DISCUSSION

Pars plana vitrectomy is the surgical procedure of choice in the management of posteriorly dislocated lens fragments after cataract surgery. Lens fragments were successfully removed in all patients, leading to improvement in vision and control of inflammation and IOP. In our series, visual acuity was 6/12 or better in 58.5% of patients, which is consistent with findings (44% to 71%) in previous studies.2–14

Elevated IOP occurred in 46.3% of cases; the incidence in other series2,4,6,8–10 ranges from 25% to 52%. In our study, anterior vitrectomy had a clear association with a decreased incidence of elevated IOP, and we believe this is the first report of such an association. We therefore recommend that anterior vitrectomy be routinely performed in all cases of dropped nuclei. Fastenberg et al.16 advocate anterior vitrectomy for this reason but did not support this strategy with evidence. Contrary to what some believe, we found no association between anterior vitrectomy and RD, a result supported by Ang and Whyte.17

In addition, as in other studies, 4,6,8,18 we found no association between delayed PPV and complications such as elevated IOP (Table 5) and reduced visual acuity. This is in contrast to other studies5 that report an association between delayed surgery and these complications.

Table 5
Table 5:
Relationship between development of glaucoma (IOP >25 mm Hg or <25 mm Hg but required glaucoma medication) and timing of vitrectomy.

The incidence of RD before PPV was low. This may indicate that current cataract surgeons are more experienced in dealing with dropped nuclei. Individual inspection of the notes from each operation showed that surgeons did not attempt to retrieve the posteriorly dislocated lens material with a lens loop, forceful irrigation, cryoprobe, phaco probe, or other means that can cause vitreous and retinal traction.12 In addition, we noticed that older studies had higher rates of RD after PPV than the more recent series, including ours (median 9.15% versus 5.15%) (Table 6). Smiddy et al.22 provide a likely explanation for the lower rates of RD after PPV; that is, a meticulous search of entry sites for open iatrogenic peripheral retinal breaks and use of ultrasound only when necessary. The proposal that delayed vitrectomy is associated with RD after PPV5 was not supported by our study.

Table 6
Table 6:
Retinal detachment associated with retained lens fragments.

In conclusion, our retrospective review showed that anterior vitrectomy is helpful in reducing the incidence of elevated IOP after dropped nuclei. It also found that irrespective of its timing, vitrectomy surgery for dropped nuclei is associated with a good clinical outcome as well as a low incidence of complications such as RD and endophthalmitis

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