Dark adaptation impairment in patients with drusen

Abstract

Purpose : The functional impairment induced by drusen in age-related macular degeneration (AMD) is not fully characterized. The purpose of this study is to evaluate the difference between patients with drusen and healthy controls in terms of dark adaptation (DA), and to explore if there are differences by drusen type, namely soft drusen and reticular pseudodrusen (RPD).

Methods : Prospective, observational study. Patients aged 50 and above with predominant soft drusen or RPD associated with early AMD in one eye with no other ocular comorbidities and healthy controls were selected. All patients received a complete ophthalmic exam, including imaging. Two observers classified fundus images as showing predominantly soft drusen, RPD or none. DA test(AdaptDx,Maculogix) was performed in all subjects. RIT, descrived as the time to recover visual sensitivity to 0.0005 scot cd/m², was the main variable. A RIT>12 minutes was considered abnormal. If after 20 minutes the RIT could not be determined, subject was considered to have a RIT of 20 minutes. The comparison of median RIT between groups (Mann-Whitney test) was the main outcome. Secondary outcomes included comparison of percent of abnormal RIT between groups (Fisher exact test), comparison of median RIT between the subgroup of soft drusen and RPD (Mann-Whitney test) and a multivariable linear regression model to evaluate the independent contribution of baseline features on RIT.

Results : We included 20 eyes of 20 patients, 12 with drusen (8 soft drusen, 4 RPD) and 8 controls. The groups were similar in all measured baseline features (age, sex, best-corrected visual acuity -BCVA-, arterial hypertension, diabetes, smoking status and family history of AMD; p≥0.08). Patients with drusen showed a higher RIT than controls (20 vs 6.46 minutes, p=0.001). A larger percentage of patients with drusen showed an abnormal RIT as compared to controls (91.7 vs 12.5%, p=0.001). No statistical significant difference was found between RIT in patients with soft drusen and RPD (18.7 vs 20, p=0.11), although all patients with RPD showed always a RIT>20. Presence of drusen and age (p≤0.047) were associated with a larger RIT after adjustment for sex and BCVA.

Conclusions : Patients with drusen showed a larger RIT (worse DA) than healthy controls. In this sample, more than 90% of patients with drusen showed an abnormal RIT. RIT could not be determined in any patient with RPD (>20), suggesting a very poor dark adaptation.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.