Methods

The medical records of consecutive patients who underwent vitrectomy for vitreous floaters between January 2006 and June 2010 were reviewed. All patients were operated at the Academic Medical Center Amsterdam, a tertiary academic referral center. All patients gave informed consent for the procedure. Patients often were examined on multiple visits before consideration of surgical intervention to confirm the persistence of the symptoms and to provide detailed information to each patient regarding the potential risks of the procedure. Data were retrieved from an electronic patient file containing structured operation notes and reports of all visits.

Operations were performed with the Alcon Accurus or Alcon Constellation machine (Alcon Laboratories, Fort Worth, Texas, USA) and a BIOM wide-angle viewing system (Binocular Indirect Ophthalmol Microscope; Oculus Inc, Wetzlar, Germany). For the Accurus 25-gauge procedures, infusion pressure was set at 30 mm Hg, vacuum was set at 500 mm Hg, and cutting rate varied between 1000 and 1500 cuts/minute. For the Constellation 25-gauge procedures, infusion pressure was 25 mm Hg, vacuum was 300 mm Hg, and cutting rate varied between 2500 and 5000 cuts/minute. For all 20-gauge procedures, infusion pressure was set at 20 mm Hg and vacuum was set at 300 mm Hg, with cutting rate varying between 1000 and 2500 cuts/minute. If the posterior hyaloid was attached, a PVD always was induced. Vitreous was removed up to the vitreous base. We did not use visualization aids during the PVD induction. Shaving of the vitreous base was performed only around retinal breaks. An extensive internal search was performed in all cases using visualization with the BIOM system and scleral indentation, and the location of retinal breaks were drawn in the chart. All peripheral lesions that resembled breaks or areas of traction were treated with external cryotherapy.

Parameters retrieved were patient characteristics, preoperative and postoperative VA, preoperative phakic status, combined phacoemulsification, comorbidity, active PVD induction, intraoperative peripheral retinal breaks or traction areas, application of cryocoagulation, and tamponade type.

Statistical analysis was performed using SPSS software for Windows version 16.0 (SPSS Inc, Chicago, Illinois, USA) for chi-square test, Wilcoxon signed-rank test, Mann–Whitney U test, and Kruskal-Wallis analysis. For analysis, VA was converted to logarithm of the minimal angle of resolution (logMAR) values, whereby counting fingers was converted to 1.40 logMAR and hand movements was converted to 2.70 logMAR.

Results

A total of 116 eyes from 97 patients were included. All cases had a history of persistent floaters for at least 6 months. Mean follow-up was 10.1 months (range, 3 to 57 months). Mean patient age was 58.7 years (range, 26 to 86 years). Most operations were performed under local anesthesia. General anesthesia was used only in patients who made a specific request. The posterior hyaloid was still attached in 30 (25.9%) cases. In all of these, we actively induced a full PVD. We found that the necessity of PVD induction was related significantly to patient age. Patients in whom a PVD had to be induced were on average younger than patients with a preexisting PVD (55.2 and 59.9 years, respectively; P = .021, Mann–Whitney U test).

We treated 86 eyes for primary floaters and 30 eyes that had floaters secondary to other ocular disease (10 RRD, 3 Fuchs uveitis, 3 anterior uveitis, 1 intermediate uveitis, 6 posterior uveitis, 2 retinitis pigmentosa, 5 other). There was no difference in age between these groups (mean age, 59.6 and 56.1 years, respectively; P = .233, Mann–Whitney U test). The cases secondary to RRD all had been treated with external buckle surgery. All uveitis-related cases were quiet without medication and had no uveitis activity for at least 1 year preceding the surgery. In the primary floaters, we had to induce a PVD in 26 (30.2%) of 86 cases, and in the secondary floaters, this was necessary in 4 (13.3%) of 30 cases. This difference did not quite reach significance ( P = .069, chi-square test).

From the total of 116 cases, we detected 1 or more iatrogenic retinal break in 19 cases (16.4%). All breaks were treated with external cryopexy and air or gas tamponade. In the remaining 97 cases without breaks, other precursors were found. In 11 cases, only retinal traction tufts were found and treated with cryocoagulation. In 3 cases, we encountered retinal breaks with signs of chronicity (surrounding subretinal pigmentation or sclerosed flaps). We considered these breaks to be preexisting and treated these with cryocoagulation and internal tamponade. In 2 cases, a retinal break was found at the preoperative examination and was treated with laser coagulation before surgery. In total, we used gas tamponade (SF ₆ 20%) in 4 cases (3.4%) and air tamponade in 43 cases (37.1%). In 19 of these cases, gas tamponade (4 SF ₆ and 15 air) was used for prevention of retinal detachment in eyes with iatrogenic breaks. In the remaining 24 cases of air tamponade, this tamponade was used to prevent hypotony in 25-gauge vitrectomy.

In the 29 cases that underwent 20-gauge vitrectomy, we found iatrogenic retinal breaks in 20.1%, whereas breaks were found in 25-gauge cases in 14.9%. This difference was not statistically significant ( P = .469, chi-square test). Breaks tended to occur more frequently in the cases of primary floaters (18.6%) compared with the cases of secondary floaters (10.0%), but this difference was not statistically significant ( P = .273, chi-square test). We did find a relation between occurrence of breaks and PVD induction. In the cases with PVD induction, retinal breaks were found in 30.5%, and in the eyes that had preexisting PVD and did not require active induction, retinal breaks were found in only 11.6% of cases. This difference was statistically significant ( P = .019, chi-square test).

We measured the postoperative intraocular pressure (IOP) at day 1. Six eyes (5.2%) were hypotonus, defined as an IOP of 5 mm Hg or less. The hypotony resolved spontaneously within 1 week. None of the eyes had clinical signs of hypotony, like Descemet wrinkling or choroidal folds. All cases of hypotony had undergone 25-gauge vitrectomy. In 9 eyes (7.8%), the IOP was increased, defined as an IOP of 25 mm Hg or more. These were treated with topical antiglaucoma medication, and in all cases, IOP returned to normal within 3 weeks after operation. Postoperative day 1 IOP was significantly higher after 20-gauge vitrectomy (mean, 16.2 mm Hg) than after 25-gauge vitrectomy (mean, 13.3 mm Hg; P = .011, Mann–Whitney U test).

Thirty-six cases were phakic without cataract (31%), 54 cases (46.6%) were pseudophakic, and in 26 cases (22.4%), the vitrectomy was combined with cataract extraction. In the phakic cases, cataract developed during follow-up in 18 (50%). In 9 cases, the cataract already was treated before the end of follow-up. A macular pucker developed in 2 cases, 1 in a primary floater case and 1 in a case after uveitis. A choroidal hemorrhage occurred during 1 operation. The hemorrhage developed during the vitrectomy, but remained anterior to the equator and resolved spontaneously. RRD occurred in 3 cases (2.5%), all within 3 months after surgery. All 3 cases were operations for primary floaters. Two cases were attached after 1 operation and retained good VA. In 1 case, proliferative vitreoretinopathy developed, requiring 3 retinal attachment procedures and ending with very poor visual function (VA of hand movements). In none of the 10 patients who had an RRD before the procedure did an RRD developed during follow-up. There were no cases of endophthalmitis in our series.

Overall, the mean logMAR VA improved from 0.20 to 0.13 ( P < .001, Wilcoxon signed-rank test). Improvement was significantly greater in cases where a combined vitrectomy and phacoemulsification was performed. Mean logMAR VA change was −0.06 for the phakic eyes (n = 36), −0.02 for the pseudophakic eyes (n = 54), and −0.22 for the combined procedures (n = 26). This difference in improvement of VA was statistically significant ( P < .001, Kruskal-Wallis test). Preoperative VA was on average lower in secondary cases (0.37) than in primary cases (0.15; P < .001, Mann–Whitney U test). We compared VA change between the primary and the secondary cases. In the 86 primary cases, the mean logMAR VA change was −0.058, and in the 30 secondary cases, the mean logMAR VA change was −0.127. Thus, in the secondary cases, the mean VA seemed to improve more than in the primary cases. This difference was not statistically significant ( P = .192, Mann–Whitney U test).