Functional clinical endpoints and their correlations in eyes with AMD with and without subretinal drusenoid deposits—a pilot study

Purpose To evaluate functional clinical endpoints and their structural correlations in AMD, with a focus on subretinal drusenoid deposits (SDD). Methods This prospective study enroled 50 participants (11 controls, 17 intermediate AMD (iAMD) with no SDD, 11 iAMD with SDD and 11 non-foveal atrophic AMD). Participants underwent best-corrected visual acuity (BCVA), low luminance visual acuity (LLVA), low luminance questionnaire (LLQ), scotopic thresholds, rod-intercept time (RIT), photopic flicker electroretinograms and multimodal imaging. Functional and structural relationships were assessed. Results Compared with healthy participants, BCVA, LLVA, scotopic thresholds were depressed, and RIT prolonged in iAMD patients with SDD ( p = 0.028, p = 0.045, p = 0.014 and p < 0.0001 respectively). Patients with SDD also had reduced scotopic function and delayed RIT compared to iAMD without SDD ( p = 0.005 and p < 0.0001). Eyes with SDD and non-foveal atrophy did not differ functionally. Nor did healthy subjects compared with iAMD without SDD. Functional parameters were significantly associated with scotopic thresholds ( r = 0.39–0.64). BCVA, LLVA and scotopic thresholds correlated well with ONL volume, ONL thickness and choroidal thickness ( r = 0.34–0.61). Conclusion Eyes with SDD are surrogate markers of photoreceptor abnormalities comparable with non-central atrophy and should be sub-analysed in clinical trials evaluating potential prophylactic agents to decrease the progression of AMD and may even require different therapeutic interventions.