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Vittorio Silvestri, Evelyn Moore, Sean Lui, Silvestri Giuliana; Correlation of the Geographical Distribution of Drusen in the Human Macula in the Irish Nun Eye Study (INES). Invest. Ophthalmol. Vis. Sci. 2014;55(13):647.
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Age-related Macular degeneration (AMD) is the leading cause of blindness in elderly populations. Drusen are considered hallmarks of AMD and are strong predictors of subsequent advancement of the disease. Sun exposure has been implicated in the pathogenesis of AMD. The Irish Nun Eye Study (INES) was a study designed to investigate the prevalence of AMD in communities with protected lifestyles compared to the general population with specific reference to light exposure. The aim of this part of the project was to investigate the geographical distribution of drusen around the macula. Due to protection from the eyelid, the drusen accumulation in the inferior quadrant was expected to be least.
Stereoscopic fundus photos were captured of fields F1 (optic disc centred) and F2 (macula centred) using a Nidek AFC210 fundus camera. Using the EDTRS grading grid overlaid on the fundus images in Adobe Photoshop, data was recorded on the morphology and distribution of drusen within the nine macular subfields and analysis of the distribution of drusen according to number of drusen and largest drusen per quadrant was carried out and analysed using the chi-squared test. The right eye was selected in all cases unless there was no available image where the left eye was selected. As the central macula is always exposed to light and is protected by the luteal pigment, this was excluded from the analysis
The study failed to find a relationship between UV and visible light exposure and AMD however drusen were more likely to be present in the superior, nasal and temporal quadrants with significantly less drusen in the inferior quadrant (p< 0.001). The inferior quadrant was also least likely to contain the largest druse (p< 0.001). This finding is in keeping with the results from the Beaver Dam Study1 which also reported that drusen were more likely to develop in the superior and temporal quadrants.
We conclude that light exposure is not a risk factor for AMD in the INES but that drusen accumulation was least prevalent in the inferior quadrant. The finding would be in keeping with outdoor conditions as in bright lighting conditions the inferior macula is usually in shadow. Reference 1: Cruickshanks KJ, et al. Arch Ophthalmol 1993;111:514-518
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