Investigation Of The Mechanism Of Near-infrared Induced Cataract

Abstract

Purpose: : This study examines the mechanism of near-infrared, namely infrared A (IRA), light induced cataract.

Methods: : Near infrared (wavelength 808 nm; power 0.6 W; exposed area 6 mm diameter) was exposed to the vicinity of the boundary of the iris and pupil of 6 rabbits eyes for six minutes (The part around the crystalline lens attained thermal equilibrium under this exposure in the preliminary experiment). We checked the ocular condition before and after exposure by slit-lamp. After injection of 0.2% aqueous solution of microencapsulated liquid crystal (MTLC changes color through red, yellow, green and blue with temperature elevation) into the anterior chamber of a second rabbit group, infrared (power 0.2 W; exposed area 6 mm diameter) was again exposed. Temperature distribution in the anterior chamber under the exposure was measured.

Results: : Myosis by iridocyclitis, discoloration of iris and iris atrophy were observed from immediately after exposure in the area under exposure. One day after exposure, posterior synechia of the iris and cortical cataract were seen in the exposed area. Lens opacity of the pupillary zone was very light. No ocular change was seen in non-exposed control eyes. The first temperature changes in the anterior chamber of IRA exposed eyes were observed to the right above the iris where the temperature reached over 40ºC.

Conclusions: : The mechanism of infrared induced cataract was that IRA absorbed by the iris and pupil generated heat. This heat was secondarily transported to the lens and induced cataract.

Keywords: cataract • radiation damage: light/UV • laser