Abstract
Purpose::
To investigate light scatter characteristics for acrylic intraocular lens models.
Methods::
Several intraocular lens (IOL) types made from SENSAR® and ACRYSOF® acrylics were measured in a liquid cell filled with a saline solution. A pencil beam was projected onto the IOL and the scattered light was measured angle resolved. Subsequently, a very narrow slit was projected onto the IOL and the scattered light was measured again such that the bulk and surface scatter could be separated for large angles. For both illuminations the light scatter was measured for twelve forward directions ranging from -23° to + 23° and in one backward direction. Following measurement the lenses were immersed in purified water. After 14 days a subset was placed into an oven for two days at 35°C in order to create clinically representative vacuoles. Then lenses were re-measured. The results obtained with the pencil beam illumination were compared to light scatter levels of a 20yr old and 70yr old healthy crystalline lens.
Results::
All lens types behaved similarly and the results of the first measurement series showed that the scatter level was below the level of a healthy 20yr old crystalline lens. The procedure used might be improper to simulate the clinical setting accurately but following immersion in purified water the light scatter level was above that of 20yr old crystalline lens for all cases. In most cases the scatter level remained below the level of a 70 yr old crystalline lens. The ACRYSOF lenses which were placed in the oven contained more vacuoles and scattered the most. The bulk scattered intensity for these lenses in backward directions was relatively small, so that the functional significance of the scatter introduced by vacuoles may be underestimated in the clinic.
Conclusions::
Initially, the light scatter level of all intraocular lenses is below that of a 20yr old lens healthy crystalline lens. The light scatter in intraocular lenses increases after immersion for several days in purified water. The forward light scatter of ACRYSOF lenses containing vacuoles is relatively large compared to the backward light scatter intensity. The angle resolved measurement of light scatter of IOLs could be valuable for further improving the quality and performance of IOLs.
Keywords: intraocular lens • optical properties • aging: visual performance