Abstract
Purpose::
To facilitate the selection of the spectral filter in intraocular lenses.
Methods::
We measured the spectral transmission of commercially available intraocular lenses, and gathered information from manufacturers datasheets and from the literature. Illumination with sunlight filtered by the natural (age 20 and 70), 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. Artificial lenses also included hypothetical ones with common sharp cutoff filters.
Results::
The 70 year old lens offers a reduction in blue light damage of 0.45 log unit compared to the 20 year lens; a similar reduction occurs in the signal from the short wave sensitive (SWS) cones. Intraocular lenses showed a range of nearly 1 log unit in blue light damage protection. A change in dioptric power in blue blocking lenses, with a corresponding change in thickness, strongly influenced behavior; cutoff filters were far less sensitive.
Conclusions::
Blue blocking lenses showed peculiar density spectra compared to the natural lens, but their filtering generally caused only mild sensory losses. Nearly none of these lenses offers an optimal trade-off between protection and signal reduction. Sharp cutoff filters provide a better performance and also remove limitations in the optical design. With a criterion loss of 0.2 log unit in signal compared to that of the young lens the optimal cutoff wavelength lies at 445 nm.
Keywords: intraocular lens • radiation damage: light/UV • photoreceptors: visual performance