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Kamal K Das, Liliana Werner, John Stover, Jim Schwiegerling; Forward Light Scatter, Stray Light and Image Quality in Intraocular Lenses at Various Light Scattering Angles. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):1073.
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© ARVO (1962-2015); The Authors (2016-present)
Stray light due to significant forward light scattering (FLS) may cause visual impairment. This study evaluates FLS and compares stray light values of new and artificially aged intraocular lenses (IOLs) at light scattering angles of 10, 15, 20, 25 and 30 degrees. Optical quality performance of the IOLs is evaluated based on Modulation Transfer Function (MTF) and letter chart images using a Badal optometer.
FLS of the new and artificially aged AcrySof IOLs was measured with the Complete Angle Scattering Instrument (CASI). The stray light values of these lenses were obtained from the measured FLS data at light scattering angles of 10, 15, 20, 25 and 30 degrees. New AcrySof IQ SN60WF lenses with IOL powers of 15, 21, 23 and 24 Diopters (D) were used to obtain stray light values. AcrySof SN60AT and AcrySof IQ SN60WF lenses were aged in a laboratory for periods equivalent up to accelerated 10 years. The same technique was used to measure FLS and compare stray light values for the aged IOLs. The MTF and image acquisition test systems incorporate a custom eye model with a wet cell for mounting the IOL. Pupil sizes of 3 and 6 mm were used.
The average stray light values of the SN60AT (N=2) was 0.257+/0.260 and 0.249+/0.306 for SN60WF (N=4) at a scattering angle of 10 degrees. The stray light values decreased at higher scattering angles of 15 to 30 degrees for both groups of lenses. The decrease of stray light was faster for SN60WF compared to SN60AT at all angles. The average stray light values for the SN60AT was -0.174+/0.310 and -0.517+/0.072 for SN60WF at a scattering angle of 30 degrees. The stray light values for the IOL powers of 15, 21, 23 and 24 D indicated a linear trend with the exception of one value for the 24D at 10 degrees. Stray light values for 10 years aged SN60WF was lower compared to 10 years aged SN60AT at the tested light scattering angles. The MTF values and Badal bench did not degrade for the laboratory aged IOLs compared to a new IOL.
The forward light scatter and stray light values of all tested IOLs at various light scattering angles were well below the stray light hindrance value of 1.47 and thus would not have a meaningful impact on the visual function. The optical performances of these lenses do not show any impact on the optical quality both at smaller and larger pupils.
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