Fred H. Lambrou

Mechanisms of Intraocuular Pressure Elevation after Pars Plana Vitrectomy

Abstract A prospective study of 222 consecutive patients undergoing pars plana vitrectomy was done to determine the incidence and mechanisms of postoperative intraocular pressure (IOP) elevation. Within 48 hours of surgery, postoperative IOP increased by at least 5 to 22 mmHg in 136 eyes (61.3%) and to 30 mmHg or more in 79 eyes (35.6%). Presumed mechanisms of openangle glaucoma included intraocular gas expansion (28.4%), inflammatory trabecular meshwork obstruction (4.5%), silicone oil-related glaucoma (3.6%), and erythroclastic glaucoma (2.2%). Closed-angle mechanisms included pupillary block glaucoma (6.8%) and ciliary body edema (3.6%). Factors which were associated with postvitrectomy pressure elevation included placement of a scleral buckle, either intraoperatively ( P = 0.003) or before vitrectomy ( P = 0.001), intraoperative scatter endophotocoagulation ( P = 0.041), intraoperative lensectomy ( P = 0.024), and development of postoperative fibrin membranes ( P = 0.038). Surgery was required to lower IOP or relieve pupillary block in 25 eyes (11.3%).

Management of Dislocated Lens Fragments during Phacoemulsification

BACKGROUND Dislocation of nuclear lens fragments during phacoemulsification can lead to a high incidence of glaucoma, uveitis, and poor visual acuity. The correct approach to these patients is uncertain. The authors report on eight patients who underwent pars plana vitrectomy with removal of lens fragments. METHODS Charts of eight consecutive patients who developed dislocation of nuclear lens fragments into the vitreous cavity during phacoemulsification were retrospectively reviewed. All patients underwent a standard three-port pars plana vitrectomy with removal of the dislocated nuclear fragments by pars plana fragmentation. After the vitrectomy, the retina was inspected with indirect ophthalmoscopy. Tears were treated with cryopexy. A fluid-air exchange and scleral buckle were performed when indicated. RESULTS Retinal tears were located at the vitreous base in four of eight patients. After vitrectomy, visual acuity improved in all patients, with 7 of 8 patients achieving visual acuity of 20/40 or better. The type of pseudophakia did not influence the final visual acuity. There were no cases of glaucoma, uveitis, or macular edema with up to 22 months of follow-up. CONCLUSIONS These results suggest that large nuclear fragments dislocated into the posterior segment during phacoemulsification can be removed safely with pars plana vitrectomy and lensectomy with an excellent visual prognosis. Attempts to remove lens fragments during the phacoemulsification through an anterior wound should be avoided because of excessive vitreous traction, leading to retinal break formation.

Treatment of Experimental Intravitreal Fibrin With Tissue Plasminogen Activator

We produced experimental intravitreal fibrin clots in rabbits that had previous gas compression of the vitreous or intact vitreous. Twenty-four hours after production of fibrin, the eyes were injected with 25 micrograms of tissue plasminogen activator or physiologic irrigation solution. In the gas compression group (n = 11), all tissue plasminogen activator-treated eyes cleared within six hours of injection; complete clearing was not seen until six days in the physiologic irrigation solution-treated eyes (n = 9). A similar response was seen in the intact vitreous group. No evidence of toxicity was observed as measured by slit-lamp biomicroscopy, intraocular pressure, corneal thickness, electroretinography, or histopathologic examination.