Straylight in fish-eye disease: visual quality and angular dependence of straylight

Aim: To quantify visual complaints by determining straylight values, to investigate the angular dependency of straylight, and to examine the use of straylight for clinical decision making in fish-eye disease (FED) patients. Research design and methods: Straylight was measured in 10 patients with FED using the compensation comparison method (Oculus C-Quant). Additionally, the direct comparison method was used for four patients to measure straylight at different visual angles. Results: Average straylight in untreated eyes with FED was 1.91 log(s). Penetrating keratoplasty and deep anterior Lamellar keratoplasty treated eyes had average straylight levels of 1.53 log(s) and 1.63 log(s), respectively. Straylight in FED was not strongly angle dependent. Conclusions: Straylight was highly elevated (up to 24x age normal value) although visual acuity was relatively well preserved. For several patients, complaints were severe enough to undergo corneal transplantation resulting in reduced straylight and alleviation of complaints. Straylight in FED follows relatively normal angular dependence. We conclude that straylight measurements can support clinical decision-making by quantifying complaints about reduced visual quality, even if visual acuity remains normal.