EFFECT OF NEODYMIUM-YAG LASER ON SODIUM HYALURONATE IN-VITRO AS A MODEL FOR POSTCAPSULOTOMY INTRAOCULAR-PRESSURE CHANGE

Purpose: To define one possible etiology for the rise in intraocular p ressure (IOP) after neodymium:YAG (Nd:YAG) laser capsulotomy and provi de information for the continued investigation of this process. Settin g: Laser Center, Eye and Ear institute, Pittsburgh, Pennsylvania. Meth ods: Samples of 1% sodium hyaluronate or balanced salt solution (BSS(R )) (control) were placed in a closed system and exposed to varying amo unts of Nd:YAG energy delivered by a Coherent YAG laser. This system w as hydrostatically coupled to a pressure monitor, and changes in press ure were recorded as a function of time. Results: Average pressure inc rease was 0.140 mm Hg/mJ of YAG energy in the sodium hyaluronate sampl es and 0.017 mm Hg/mJ in BSS (P < .01). The relationship between total energy delivered and maximum pressure recorded for both substances wa s nearly linear. Further analysis of treated sodium hyaluronate sample s showed that Nd:YAG energy can produce structural alterations. Conclu sions: Neodymium:YAG laser energy has a pronounced effect on sodium hy aluronate that exceeds the thermal effect seen with BSS when the press ure is monitored in a closed system. These structural changes might co ntribute to the IOP rise seen clinically.