Effects of IOL Opacification on Light Scatter and Overall Optical Quality and Performance
To evaluate light scatter and stray light in a series of intraocular lenses (IOLs) explanted because of postoperative optic opacification (13 calcified hydrophilic acrylic lenses; 1 calcified silicone lens; 4 PMMA lenses with snowflake degeneration), as well as the effect of opacification on other optical quality/performance indicators.
Back scatter was measured with a Scheimpflug camera (EAS-1000 Anterior Segment Analysis System, Nidek, Ltd.). Light transmittance was measured with a Perkin Elmer Lambda 35 UV/Vis spectrophotometer (single-beam configuration; RSA-PE-20 integrating sphere). The Complete Angle Scatter Instrument (CASI) scatterometer was used to directly measure the forward-scattered light of the IOLs, and the stray light values at various angles were calculated. All measurements were done at room temperature in the hydrated state. Modulation Transfer Function (MTF) was then obtained with an optical bench, and a Badal optometer was used to obtain letter chart images through the lenses.
Average stray light values (Log (s)) at a scattered angle of 10 degrees were measured as 1.629 +/- 0.465 for PMMA IOLs (control PMMA = 0.258), 1.791 +/- 0.370 for hydrophilic acrylic IOLs (control hydrophilic acrylic = 1.335), and 1.539 for the silicone lens (control 0.418). MTF and Badal image contrast were drastically reduced in lenses with calcification and snowflake degeneration.
Studies from van den Berg et. al. described the impact of stray light in human vision, with serious hindrance above 1.47 (Log (s)). Based on our results, lenses explanted from patients because of clinically significant opacification are associated with a considerable increase in light scatter and stray light, as well as with a decline of other optical quality/performance indicators.