[Influence of light scattering in the opaque lens on the ability to focus--examination utilizing opacified model lenses]

In order to objectively evaluate the relationship between the quality of images which will be reflected on the retina, through opaque lenses and the grade of opacification, model lenses of nuclear cataract and subcapsular cataract were manufactured. The nuclear cataract model lenses were made of polymethylmethacrylate (PMMA) with and without a cut off wavelength below 380 nm. The lens shape was the biconvex intraocular lens (IOL) type and the opacification was achieved by polymerization of both hydrophile and lyophobic monomers. The model of subcapsular opacification was composed of ultraviolet (UV)-cut IOL and a hard contact lens (HCL). The HCL was attached behind the IOL and whitish corpuscles (T1O2, mean diameter of particle = 0.2 micron) were inserted into the gap between the lenses. Utilizing a still camera with 35 mm film, images were photographed through the nuclear opacified model lenses and evaluated. The model of the subcapsular opacified lens was examined by a simulation camera (CCD) in which the lens was held in water. The image quality obtained from the non-UV absorbed nuclear opacification type lens was markedly poor compared with that from the UV absorbed type lens. Although image contrast became worse with increased nuclear opacification, the worsening of image quality was slight in the opacified lens with a 20% reduction of light transmission. It was even possible to recognize photographed subjects through an opacified lens with 60% transmission. Images through the subcapsular opacified model lenses were not influenced by the opacified area in the models with up to 130 cct light scattering intensity at the central part of opacification. Although the study aimed to simply simulate images reflected on the retina through two types of cataractous lenses, the results obtained showed useful objective information concerning images seen through cataractous eyes.