Effects of Subsurface Nanoglistenings in Hydrophobic Acrylic IOLS on Lightscatter and Overall Optical Quality and Performance
Purpose
Light scattering of hydrophobic acrylic intraocular lenses (IOLs) is due to subsurface nanoglistenings (SSNG), generally not leading to explantation. We evaluated back and forward light scatter in single-piece hydrophobic acrylic (AcrySof, Alcon) IOLs removed from cadaver eyes and design/power-matched controls, as well as the effect of SSNG on other optical quality/performance indicators.
Methods
17 single-piece AcrySof IOLs exhibiting SSNG were removed from cadaver eyes (11 with a blue light filter – BLF – and 6 without). 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.
Results
Average stray light values (Log (s)) at a scattered angle of 10 degrees were measured as 1.036 +/- 0.270 for BLF lenses, and 0.975 +/- 0.264 for non BLF lenses (controls 0.223 +/- 0.229). MTF and Badal image contrast of cadaver-eye removed lenses were similar to controls (no SSNG) AcrySof lenses.
Conclusion
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, stray light in hydrophobic IOLs due to SSNG is well below the value of stray light hindrance of 1.47 (no lens with a value ≥ 1.47), which would not cause noticeable visual impairments.