Injuries remain the most serious public health problem facing developed nations. Yet, a persistent inadequacy exists both in the standardized documentation of eye injuries and in their treatment. With appropriate surgical and medical intervention, a majority of the reported injured eyes recovered functional levels of visual acuity. It appears that glasses, including prescription glasses and even non-prescription sunglasses, can offer measurable protection which results in a lower incidence of severe eye injuries to those wearing glasses.
Objective
To examine whether slowed rod-mediated dark adaptation in adults in normal macular health at baseline is associated with the incidence of age-related macular degeneration (AMD) three years later.
Design
Prospective cohort
Participants
Adults ≥ 60 years old were recruited from primary care ophthalmology clinics. Both eyes were required to be step 1 (normal) on the AREDS 9-step AMD classification system based on color fundus photographs graded by experienced and masked evaluators.
Methods
Rod-mediated dark adaptation was assessed at baseline in one eye following a photobleach using a computerized dark adaptometer with targets centered at 5° on the inferior vertical meridian. Speed of dark adaptation was characterized by the rod-intercept value, with abnormal dark adaptation defined as rod-intercept ≥ 12.3 minutes. Demographic characteristics, best-corrected visual acuity, and smoking status were also assessed. Log-binomial regression was used to calculate unadjusted and adjusted risk ratios (RRs) and associated 95% confidence intervals (CIs) for the association between baseline dark adaptation and incident AMD.
Main Outcome Measure
AMD presence at the three-year follow-up visit for the eye tested for dark adaptation at baseline.
Results
Both baseline and follow-up visits were completed by 325 persons (mean age 67.8 years). At baseline 263 participants had normal dark adaptation with mean rod intercept of 9.1 (SD 1.5), and 62 had abnormal dark adaptation with mean rod intercept of 15.1 (SD 4.0). After adjustment for age and smoking, those with abnormal dark adaptation in the tested eye at baseline were almost 2 times more likely to have AMD in that eye (RR 1.92, 95% CI 1.03-3.62) by the time of the follow-up visit, as compared to those who had normal dark adaptation at baseline.
Conclusions
Delayed rod-mediated dark adaptation in older adults in normal macular health is associated with incident early AMD three years later, and thus is a functional biomarker for early disease. The biological relevance of this test is high, because it assesses translocation of vitamin A derivatives across the retinal pigment epithelium and Bruch's membrane, two tissues with prominent age- and AMD-related pathology.
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