Sharp cutoff filters in intraocular lenses optimize the balance between light reception and light protection

Abstract

To facilitate the selection of the spectral filter in intraocular lenses (IOLs). Department of Ophthalmology, University Medical Center Utrecht, Utrecht, The Netherlands. The spectral transmission of commercially available IOLs was measured, and information from manufacturer data sheets and the literature was gathered. Illumination with sunlight filtered by the natural eye media (aged 20 and 70 years) and artificial eye media resulted in calculated values for the blue-light damage and the signals from the sensory systems (rods, cones, melatonin suppression, and melanopsin). Results were presented as log differences with respect to the 20-year-old human lens. A single rating value for each lens was calculated to facilitate the selection. The 70-year-old lens showed a reduction in blue-light damage of 0.45 log units compared to the 20-year-old lens, although a similar reduction occurred in the signal from the short-wave-sensitive cones. Intraocular lenses showed a range of nearly 1 log unit in blue-light damage protection. A change in dioptric power in blue-filtering IOLs, with a corresponding change in thickness, strongly influenced behavior. Dioptric power was less of a factor in IOLs with sharp cutoff filters. Blue-filtering IOLs sometimes showed density spectra very different from those of the natural lens; however, their filtering generally caused only mild sensory losses. Nearly none of the IOLs offered an optimum tradeoff between protection and signal reduction. Sharp cutoff filtering near 445 nm provided better performance, removing limitations in optical design.