Light scatter due to intraocular lens opacification vs subsurface nanoglistenings

Session Details

Session Title: Pseudophakic IOLs: Monofocal. Cataract Surgery Instrumentation

Session Date/Time: Saturday 05/09/2015 | 16:00-18:30

Paper Time: 16:00

Venue: Room 10

First Author: : L.Werner USA

Co Author(s): :    J. Stover   J. Schwiegerling   K. Das              

Abstract Details

Purpose:

Calcification and snowflake degeneration are causes of postoperative opacification of hydrophilic acrylic/silicone and polymethylmethacrylate (PMMA) intraocular lenses (IOLs), respectively, causing significant forward light scattering generally requiring IOL explantation. Light scattering of hydrophobic acrylic lenses is due to subsurface nanoglistenings (SSNG), generally not leading to explantation. We evaluate the effects of calcification and snowflake degeneration, as well as SSNG on stray light and other optical quality/performance indicators.

Setting:

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah; The Scatter Works, Inc., Tucson, Arizona; College of Optical Sciences, University of Arizona, Tucson, Arizona.

Methods:

14 IOLs were explanted from patients due to calcification (13 hydrophilic acrylic, 1 silicone), 4 PMMA IOLs were explanted because of snowflake degeneration. 17 single-piece AcrySof (Alcon) IOLs exhibiting SSNG were removed from cadaver eyes (11 with a blue light filter – BLF – and 6 without). The forward scattering of IOLs, including new IOL controls was measured using a Complete Angle Scatter Instrument; stray light values at various angles were calculated. The Modulation Transfer Function (MTF) was obtained with an optical bench; a Badal optometer was used to capture letter chart images through the lenses.

Results:

Average stray light values (Log (s)) at a scattered angle of 10 degrees were 1.792 +/- 0.371 for calcified hydrophilic acrylic IOLs (control 1.335), 1.539 for the calcified silicone lens (control 0.418), and 1.629 +/- 0.466 for PMMA IOLs with snowflake degeneration (control 0.258). The values for the AcrySof IOLs with SSNG were 1.061+/- 0.233 for BLF lenses, and 0.975 +/- 0.287 for non BLF lenses (controls 0.223 +/- 0.229). MTF and Badal image contrast were drastically reduced in lenses with calcification and snowflake degeneration, but were similar to controls (no SSNG) in AcrySof lenses.

Conclusions:

Studies from van den Berg and associates find the impact of stray light in human vision, with serious hindrance above 1.47 (Log (s)). 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 be expected to cause noticeable visual impairments. Based on our results stray light due to calcification and snowflake degeneration reduced MTF and image contrast, while stray light due to SSNG did not.

Financial Interest:

One of the authors gains financially from product or procedure presented, One of the authors research is funded, fully or partially, by a competing company, One of the authors research is funded, fully or partially, by a company producing, developing or supplying the product or procedure presented, One of the authors is employed by a for-profit company with an interest in the subject of the presentation