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Objective: To report a series of patients manifesting ulnar neuropathy as an extraocular complication following macular hole surgery and facedown positioning., Methods: Retrospective chart review of 7 patients identified by the operating surgeon as developing ulnar neuropathy during the immediate postoperative period after undergoing vitrectomy surgery with fluid-gas exchange for macular hole followed by at least 1 week of strict facedown positioning., Results: All 7 patients developed symptoms of ulnar neuropathy, including paresthesias, dysesthesias, pain, weakness, and muscle atrophy. Signs included abnormal electromyogram, prolonged nerve conduction velocities, and impaired neurologic clinical test results in patients examined. Symptoms did not resolve with cessation of facedown positioning, and with follow-up ranging from 3 to 24 months all patients had persistent symptoms. All patients had positioned themselves with their arms continuously flexed. Three of 7 patients had placed pressure directly on their bent elbows., Conclusions: Ulnar neuropathy is an extraocular complication of macular hole surgery that can be attributed to arm position during postoperative facedown positioning. Surgeons performing macular hole surgery should caution their patients to minimize the amount of time spent with their elbows in a flexed position. Particular effort should be made to minimize pressure on the bent elbow.

The duration of mixtures of perfluoropropane and air (0% to 20% C3F8) were analyzed in 206 eyes following pars plana vitrectomy for a variety of vitreoretinal disorders using a noninvasive model for calculating the intraocular gas bubble volume. The accuracy of the noninvasive model was tested by comparing the estimated bubble volume with the actual volume withdrawn from 12 eyes with intraocular gas bubbles undergoing a subsequent vitrectomy. The method for estimating intraocular bubble volume had a mean difference between the actual and estimated bubble volume of 0.1 +/- 0.35 mL. The half-life of air (0% C3F8) was 1.3 +/- 0.1 days; 5% C3F8, 4.2 +/- 0.1 days; 10% C3F8, 6.5 +/- 0.2 days; 15% C3F8, 8.0 +/- 0.6 days; and 20% C3F8, 12.5 +/- 1.1 days. The difference between each half-life was statistically significant (P < .01). Linear regression analysis of the half-lives of C3F8 mixtures of up to 20% C3F8 showed a linear increase in half-lives with increasing concentrations of C3F8. The duration of intraocular gas tamponade can be controlled by selecting the appropriate concentration of air and C3F8.

The dynamics of pressure, flow, and ocular volume relationships were examined with respect to extrusion needle use in simulated vitrectomy. Glass-stoppered bottles used with infusion lines with drip chambers lowered the intraocular pressure 4 to 7 inches below the fluid level in the bottle, varying with the amount of fluid in the bottle. Compared with flow rates using the regular tip needle with the steel infusion cannula, the disposable infusion cannula lowered the flow rate by about 25% and the tapered tip extrusion needle decreased outflow by 40% to 50%. Tracer dilution rates were decreased by the use of the disposable infusion port or the aphakic model eye; however, 2 minutes of infusion at a 30-inch bottle height dilution was still sufficient to wash out the tracer to less than 5% of the original concentration.

To investigate the effect of extracapsular lensectomy with posterior capsulotomy, 20,000- and 70,000-dalton dextran was injected into the vitreous of rabbits. The concentration of the 20,000-dalton dextran in the aqueous of aphakic eyes was 14-fold greater than in phakic eyes 3.5 hours after injection of dextran into the vitreous. The aqueous concentration of the 70,000-dalton dextran was four times greater in aphakic eyes after 3.5 hours. The aqueous concentration of a 20,000-dalton dextran in phakic and aphakic eyes became equal between 15.5 and 22.0 hours after injection. Thus, extracapsular lensectomy with posterior capsulotomy increased the rate of movement of a single bolus of both 20,000- and 70,000-dalton dextran preparations from the vitreous to the anterior chamber.

The final visual acuities and prognostic factors predictive of these results were analyzed in 353 eyes that had pars plana vitrectomy for nonclearing diabetic vitreous hemorrhage. Eighty-one percent of the eyes had improved visual acuities on final examination. The percentage of eyes that achieved a visual acuity of 20/100 or better and the percentage that achieved 5/200 or better increased during the study period. Preoperative factors associated with a favorable visual prognosis included the following: preoperative visual acuity of 5/200 or better, absence of iris neovascularization, absence of neovascular glaucoma, clear lens or minimal cataract, and panretinal photocoagulation of at least one fourth of the fundus. Intraoperative factors associated with a favorable visual prognosis included retaining the crystalline lens and absence of an intraocular gas bubble.

Indentation of the eye wall by a scleral buckle displaces volume from the vitreous cavity. We developed a mathematical formula to calculate the volume displacement caused by a scleral buckle and verified the accuracy of this mathematical model by performing scleral buckles in 21 cadaver eyes and three eyes undergoing retinal reattachment surgery. A single 5-mm radial sponge of moderate height displaces about 0.2 mL of fluid and a circumferential 2.5-mm-wide band of moderate height displaces about 0.5 mL of fluid. Larger circumferential tires of 7- to 10-mm width displace 1.1 to 1.8 mL of fluid, depending on the height and configuration of the scleral buckle. A 7- to 10-mm-wide circumferential scleral buckle with a buckle height of 4 mm may displace up to 45% of the volume of the vitreous cavity. This volume displacement should be considered when injecting expansile gases or pharmacologic agents into the vitreous cavity.

We review our experience and present an analysis of 119 consecutive cases of macular pucker treated by vitrectomy and removal of the epiretinal tissue following treatment for acute retinal tears (16 eyes) or rhegmatogenous retinal detachment (103 eyes). Vision improved postoperatively in 104 (87%) of the 119 eyes. Final visual acuity of 20/60 or better was achieved in 38 (75%) of 51 cases in which the macula had not been detached previously and in 12 (24%) of 52 cases with prior macular detachment. Two preoperative factors were associated with a final visual acuity of 20/100 or better: (1) macula not involved by the original retinal detachment, and (2) thin epiretinal membrane.

The rate of movement of 20,000- and 70,000-dalton dextran from vitreous to aqueous was determined after extracapsular lensectomy in rabbits with an intact posterior capsule. Dextran was injected into the vitreous, and 3.5 hours later the aqueous concentration of 20,000-dalton dextran was 10.3-fold greater in the aphakic than the phakic eye. The aqueous concentration of the 70,000-dalton dextran was 3.9-fold greater in the aphakic eye after 3.5 hours. Thus, extracapsular lensectomy with an intact posterior capsule increases the rate of movement of 20,000- and 70,000-dalton dextran from the vitreous to the anterior chamber. In addition, the movement of tracers from vitreous to aqueous is increased further when the posterior capsule is opened.

The results of pars plana vitrectomy for diabetic traction-rhegmatogenous retinal detachment were analyzed in 172 eyes, and the factors associated with a final visual acuity of 5/200 or better were identified. Forty-eight percent of eyes had improved vision on final examination. The proportion of eyes with a final visual acuity of 20/100 or better and 5/200 or better remained virtually the same during the ten-year study interval. Preoperative factors associated with a visual acuity of 5/200 or better were a preoperative visual acuity of 5/200 or better, the absence of iris neovascularization, and the absence of retinal detachment involving the macula. The intraoperative factor associated with a final visual acuity of 5/200 or better was the absence of iatrogenic retinal breaks.

Intraocular gas bubbles are an important source of internal tamponade for the treatment of retinal breaks in eyes requiring vitrectomy. The kinetics of disappearance of air, 20% sulfur hexafluoride, and 10% perfluoropropane were prospectively evaluated in 76 eyes undergoing pars plana vitrectomy. The absorption of each gas approximated a first-order kinetic equation with respect to bubble volume. The half-life of air was 1.6 days in phakic and 0.9 days in aphakic eyes. The half-life of 20% sulfur hexafluoride was 2.8 days in phakic and 2.4 days in aphakic eyes. The half-life of 10% perfluoropropane was 5.7 days in phakic, 4.5 days in aphakic, and 4.3 days in pseudophakic eyes. The difference in half-life among the three gases was significant. Intraocular gases had a shorter half-life in aphakic than in phakic eyes.

We analyzed the results of 105 diabetic vitrectomy cases. The vitrectomies were performed for progressive fibrovascular proliferation that caused epiretinal membranes, vitreopapillary traction, florid neovascularization, or subhyaloid hemorrhage, with or without substantial preoperative visual loss. Eyes with inactive retinal neovascularization, dense vitreous hemorrhage, traction retinal detachment involving the macula, or combined traction and rhegmatogenous retinal detachment were excluded. Seventy-four eyes (70%) had improved final vision. The final vision was unchanged in eight eyes (8%) and was worse in 23 eyes (22%). Factors associated with a favorable visual prognosis included the following: age of 40 years or less, preoperative visual acuity of 5/200 or better, absence of preoperative iris neovascularization, preoperative panretinal photocoagulation, and absence of an iatrogenic retinal break.

The level of final visual acuity results and the prognostic factors predictive of the level were analyzed in 360 eyes that had pars plana vitrectomy for diabetic traction retinal detachment of the macula. Fifty-nine percent of the eyes had improved visual acuity on final examination. The percentage of eyes that achieved a final visual acuity of 20/100 or better and the percentage that achieved 5/200 or better increased from 21% to 36% and from 57% to 72%, respectively, during the study. Preoperative factors associated with a favorable visual prognosis were a visual acuity of 5/200 or better, the absence of iris neovascularization, a clear crystalline lens or only minimal cataract formation, clear media or only mild vitreous hemorrhage, panretinal photocoagulation of at least one fourth of the retina, and the absence of severe preoperative retinal neovascularization. Intraoperative factors associated with a favorable visual prognosis include the avoidance of performing a lensectomy, the absence of iatrogenic retinal breaks, and the avoidance of using intraocular gas bubbles.