Rod and Cone Mediated Function in Retinal Disease

National Eye Institute

Investigators

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Abstract

Aims 1 and 2 of this protocol establish normative reference ranges from healthy volunteers (HVs) for a range of functional tests used in clinical/research studies in the NEI clinic. This data is being updated because of new equipment (MonCV) added to the clinic. The functional tests and the number of HVs recruited are shown in the Table below. We now have sufficient number of HVs to establish the normative range for the new RM ERG electrode with the MonCVone. This data is being published in a manuscript in TVST (see section 13 below). Recruitment is ongoing for the other testing. We aim to recruit evenly across age groups and sex; we aim to recruit 30-40 HVs per testing paradigm. Recruitment slows as more subjects are enrolled and we fill specific categories. E.g. For dark adaptation, we have 24 enrolled HVs with even enrollment across age (5-6 per decade) and sex (2-3 of each sex) for every decade except 50-59 years old (N=2 males only). We plan to continue to enroll HVs Specific Aim 3 of this protocol is to quantify local changes in rod and cone photoreceptor function across the retina in participants with retinal disease. We have an ongoing collaboration with Drs. Emily Chew and Alisa Thavikulwat to investigate rod- and cone-mediated function and dark adaptation in patients with macular telangiectasia type II (MacTel II). A novel aspect of our study is to measure dark adaptation simultaneously at multiple loci spanning areas inside and adjacent to the MacTel area. To date we have recruited nine Mactel II patients (two since last CR). I have been working with the co-ordinater and Dr Thavikulwat to identify more MacTel patients returning to the NEI for potential DA testing. In analysis of detailed DA testing from two patients with late-onset retinal degeneration (L-ORD), I identified a rod-plateau that is evident when less than 22% of rhodopsin is bleached ( “partial bleaches”) We did not observe this plateau in nine HVs when tested with the same partial bleaching. A rod-plateau has previously been reported in patients with Sorsby’s fundus dystrophy (SFD) which shares some retinal features with L-ORD including the existence of reticular pseudo-drusen. The working hypothesis is that the rod-plateau may be a associated with RPD. We are working to recruit other patients with RPD (e.g. patients with AMD or pseudoxanthoma elasticum) to test against patients without RPD to test this hypothesis.