Abstract
Purpose::
The FDA requires multifocal intraocular lens (MIOL) manufacturers to evaluate night driving visual performance. MIOLs increase the total range of focus but degrade the retinal image at all focal planes. The driving study is required because existing clinical tests may not predict "real-world" performance well enough to assure MIOL safety. In search for a possible alternative to the driving requirement, we have compared clinical vision tests with visual performance during simulated night driving in the University of Iowa’s National Advanced Driving Simulator.*
Methods::
Fifty-five subjects [age 30-60 years, uncorrected acuity (UCVA) 20/10-20/40] completed clinical tests [UCVA, contrast sensitivity (CS), intraocular stray light] and simulated night driving tests [distance to identify road signs and hazards (objects)]. The driving, CS, and stray light tests were performed at baseline and with two "fog" levels produced by diffusing goggles to simulate MIOL light-scattering properties. All driving and CS tests were performed with and without glare.
Results::
Preliminary analysis showed that driving and clinical performance are affected similarly by glare and fog. The light and moderate fog filters increased intraocular stray light by 73% and 100%, respectively. Both filters decreased sign and object recognition distances by about 12%. Glare alone had little effect on either sign or object recognition, but adding glare to fog differentially affected sign and object recognition distances; sign recognition distances decreased only about 5%, whereas object recognition distances decreased about 26%. Both filters decreased CS by about 0.1 log unit for 1.5 and 3.0 c/deg, 0.2 log unit for 6 and 12 c/deg, and 0.05 log unit for 18 c/deg. Glare alone did not affect CS, but selectively increased the effect of fog on CS loss at 1.5 and 3 c/deg.
Conclusions::
One pattern of interaction between glare and fog effects appears to hold for low-frequency tasks (object recognition and low-frequency CS), and another for high-frequency tasks (sign recognition and high-frequency CS). These patterns suggest that CS and stray light tests may provide alternatives to driving simulation studies for evaluating MIOL safety.*Acknowledgements: We thank T. Brown and M. Wilkinson, University of Iowa, for extensive clinical and technical contributions to this research.
Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • contrast sensitivity • intraocular lens