Pulsed electron avalanche knife (PEAK) for intraocular surgery.

PURPOSE: To develop a better and more economical instrument for precise, tractionless, "cold" cutting during intraocular surgery. The use of highly localized electric fields rather than laser light as the means of tissue dissection was investigated. METHODS: A high electric field at the tip of a fine wire can, like lasers, initiate plasma formation. Micrometer-length plasma streamers are generated when an insulated 25 micron (microm) wire, exposed to physiological medium at one end, is subjected to nanosecond electrical pulses between 1 and 8 kV in magnitude. The explosive evaporation of water in the vicinity of these streamers cuts soft tissue without heat deposition into surrounding material (cold cutting). Streamers of plasma and the dynamics of water evaporation were imaged using an inverted microscope and fast flash photography. Cutting effectiveness was evaluated on both polyacrylamide gels, on different tissues from excised bovine eyes, and in vivo on rabbit retina. Standard histology techniques were used to examine the tissue. RESULTS: Electric pulses with energies between 150 and 670 microJ produced plasma streamers in saline between 10 and 200 microm in length. Application of electric discharges to dense (10%) polyacrylamide gels resulted in fracturing of the gel without ejection of bulk material. In both dense and softer (6%) gels, layer by layer shaving was possible with pulse energy rather than number of pulses as the determinant of ultimate cutting depth. The instrument made precise partial or full-thickness cuts of retina, iris, lens, and lens capsule without any evidence of thermal damage. Because different tissues require distinct energies for dissection, tissue-selective cutting on complex structures can be performed if the appropriate pulse energies are used; for example, retina can be dissected without damage to the major retinal vessels. CONCLUSIONS: This instrument, called the Pulsed Electron Avalanche Knife (PEAK), can quickly and precisely cut intraocular tissues without traction. The small delivery probe and modest cost make it promising for many ophthalmic applications, including retinal, cataract, and glaucoma surgery. In addition, the instrument may be useful in nonophthalmic procedures such as intravascular surgery and neurosurgery.

Corticosteroid therapy for optic disc neovascularization secondary to chronic uveitis.

PURPOSE: To report successful corticosteroid treatment of optic disc neovascularization associated with uveitis. METHODS: Retrospective review of medical records. RESULTS: Nine patients were identified with chronic uveitis and optic disc neovascularization without clinical or angiographic evidence of retinal ischemia. Ages ranged from 14 to 37 years (median age, 27). All patients were treated with either oral and/or subtenon's corticosteroids. Partial regression of the neovascularization was observed in all patients within 2 to 6 weeks (median, 5 weeks) after initiating treatment. Eight of nine patients had complete resolution of disc neovascularization at a median of 3 months (range, 2 to 42 months) after initiation of treatment and a median follow-up of 24 months (range, 7 to 144 months). Recurrence of disc neovascularization occurred in two patients, but it regressed again after further corticosteroid therapy. CONCLUSIONS: Optic disc neovascularization may occur in patients with chronic uveitis in the absence of retinal ischemia. This neovascularization can be successfully treated with corticosteroids.

Optic nerve head neovascularization in a patient with inactive cytomegalovirus retinitis and immune recovery.

PURPOSE: To report a case of optic nerve head neovascularization in a patient with acquired immunodeficiency syndrome (AIDS) associated with inactive cytomegalovirus retinitis and immune recovery. METHOD: Case report. RESULTS: We examined a 29-year-old man with AIDS and inactive cytomegalovirus retinitis and found vitritis and prominent optic nerve head neovascularization. The patient had been treated with reverse transcriptase and protease inhibitors, resulting in a notable rise in CD4+ lymphocyte count and an undetectable human immunodeficiency virus (HIV)-RNA viral load. No cause of neovascularization other than intraocular inflammation was detected. CONCLUSION: Immune recovery in a setting of inactive cytomegalovirus retinitis can result in optic nerve head neovascularization, as seen in our patient.