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Michael G Quigley, Ian Powell, Walter Wittich; Optical modeling shows retinal illumination is increased in hyperopes and short axial length eyes.Is this the reason for increased AMD seen in these patients?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5216.
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The working model for age-related macular degeneration (AMD) has light playing a role in its instigation however epidemiologic studies have not been able to make this association. Hyperopes are a sub-group of the population at increased risk of the disease. We calculate retinal illuminance (energy/cm2) in different eyes to determine its relationship to the eye’s refractive components in addition the relative contribution of these components to the illuminance.
Using a simple Gullstrand model eye, the retinal illuminance (energy/cm2) was calculated in a typical hyperopic eye (+1.5D) and a typical myopic eye (-4.3D) as determined with average refractive ocular parameters from the Reykjavik eye study. These results were confirmed using the ray-tracing feature in an optical design software program (Opticsoft II). The retinal illuminance (RI) was then calculated using the individual (raw data) refractive ocular parameters of 68 randomly chosen eyes from the Reykjavik eye study with the computer software. ( NB pupil size is not affected by refractive error).
The RI was calculated to be 66% more in a hyperopic than a myopic eye using the simple model and 64% more using the computer model. The calculated RI in the 68 eyes would be 2.1% greater for every diopter increasing hyperopia and 6.9% less for every mm increase in axial length.
Hyperopic and short axial lengths eyes would receive significantly more retinal illuminance than myopic or long axial length ones. Given hyperopic and short axial length eyes’ increased risk of AMD and the working model for the disease, the results support retinal light exposure as a risk factor in AMD.
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