Twelve albino rabbits were treated with cryoretinopexy on the left eye and surface diathermy coagulation on the right eye at the equatorial region in two parallel rows concentric with the limbus. Cryopexy was applied for 10 seconds with Krwawicz´s probe (the diameter of the tip was 1.5 mm) after cooling with dry ice and alcohol mixture. Diathermy coagulation was performed with 40 mA currents for 2 seconds with needle electrode without perforating the sclera.
After the treatment, ERG was recorded with varying length of intervals up to 30 days. The light stimulus was given by 100 watts incadenscent lamp and the illumination at the eye was 800 lux, its duration being 20 msec. Only the sizes of the b-potentials after 30 minutes of dark adaptation were considered.
The patterns of the b -potential changes after cryopexy were roughly divided into 3 types. The first type was seenin 5 eyes, ,and :it consisted of abrupt reductions, followed by slight augmentations, never reaching the pre-treatment level of b -wave even after 30 days. The second type (seen in 3 eyes) showed. initial slight decreases followed by marked increases and remained supernormal at the end of 30 days. The third type(4 eyes) showed marked increases from the early.. post-operative days and ,returned to the original level after 30 days. These changes were demonstrated graphically in figures 3, 4 and 5.
By diathermy coagulation, the same kinds of patterns were observed. The same animal, however, did not show the same pattern as with the cryopexy.
The final b-potential after 30 days were 105.4% of the pre-operative value by cryopexyy and 82.7% by diathermy coagulation. Thus the cryopexy produced less severe changes in ocular tissues than the diathermy coagulation.
The histological. observations. performed also supported this conclusion.
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