The inherent autofluorescence (AF) of the fundus originates from RPE lipofuscin. While RPE lipofuscin is amassed even in healthy eyes, homozygous mutations in ABCA4 are well known to confer accelerated formation of these fluorophores. Moreover, imaging of fundus AF by confocal scanning laser ophthalmoscopy (cSLO) has shown that the patterns and intensities of AF deviate from normal in several retinal disorders. Thus we aim to demonstrate that a standardized approach to quantifying fundus AF (qAF) can assist in the diagnosis of retinal disease, in the monitoring of disease progression and in the assessment of therapeutic outcomes. To enable this investigation we have gathered normative qAF data from a large number of participants with healthy eye status (aged 6-60) so as to establish ranges of qAF values with respect to age, gender and ethnicity. Going forward we will use these normal values to examine for genotype/phenotype correlations between specific ABCA4 alleles and fundus AF levels (qAF) in patients diagnosed with ABCA4- associated disease (Aim 1.1). In longitudinal studies we will measure changes in qAF values after 1 and 2 year follow-up of ABCA4-affected individuals (Aim 1.2). We will determine whether the carrier state (heterozygous) of ABCA4 is associated with elevated RPE lipofuscin, the latter being measured as qAF and compared to age-matched normals (Aim 1.3). We will also investigate the cellular basis of retinal flecks (Aim 1.4).
In Aim 2, we will determine whether the quantification of fundus SW-AF can aid in differentiating between pattern dystrophy (PD) associated with PRPH2/RDS mutations versus similar phenotypes observed with ABCA4 variants (Aim 2.1). We will also compare qAF values in individuals presenting with bull's eye macular dystrophy that is of ABCA4- versus non-ABCA4 origin (Aim 2.2). In patients with RP, we will measure qAF over the autofluorescent rings that are often a feature of this disorder. qAF Intensities inside, within and outside the rings will be compared to levels in our normal controls so as to further the use of fundus AF imaging to monitor disease progression in RP.
In Aim 4, we will determine whether elevated fundus AF is a factor influencing the onset and progression of AMD when controlling for specific CFH and ARMS2 alleles. In summary, the studies proposed in this application will examine the contribution that the lipofuscin of retina makes to the onset and progression of several retinal diseases and will demonstrate that quantitation of fundus AF facilitates the diagnosis and monitoring of some retinal disorders.
Retinal degeneration remains a major cause of legal blindness. Despite advances in the genetics of retinal degeneration, associated pathogenic processes largely defy elucidation. The work proposed in this application will address disease mechanisms that may be influential in both early onset and age-related macular degeneration and in some forms of retinitis pigmentosa.
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