Abstract
Purpose:
To study the structure and function of the cone photoreceptors in a young female (23 years old) harboring a missense mutation (p.Arg45Trp) of the Retinitis Pigmentosa 1 Like 1 (RP1L1) gene, over 2-years follow-up. The same genetic variant was found in two asymptomatic family members, i.e., the proband’s father and her brother.
Methods:
High-resolution retinal images of the cone mosaic were obtained with a flood-illumination adaptive optics (AO) retinal camera in all family members. Best Corrected Visual acuity (BCVA), Contrast Sensitivity Function (CSF), combined scanning laser ophthalmoscope (SLO) and spectral domain-optical coherence tomography (SD-OCT) imaging, microperimetry (MP1), Goldmann visual field, full-field and multifocal electroretinography (mfERG) were also performed.<br />
Results:
In the proband, BCVA (≤4/20) was almost stable in both eyes during the entire follow-up. Analysis of AO images demonstrated severe cone loss across the central 9 degrees of eccentricity with respect to controls. Adaptive optics was reliable to monitor the changes of the cone mosaic at a cellular level during follow-up. Both automated segmentation and texture analysis of SD-OCT images provided biomarkers to unveil the abnormalities of the photoreceptor layer’s integrity. The mfERG N1-P1 response amplitude densities (RADs) were severely reduced across the central 10 degrees in comparison with age-matched controls. The proband’s father had 20/20 BCVA and normal CSF in both eyes, nevertheless significant cone loss was found across the central 7 degrees of eccentricity; SD-OCT texture analysis and mfERG recordings showed abnormal values with respect to controls in the same retinal areas in both eyes. No abnormalities of the cone structure and function were found in the asymptomatic proband’s brother. Occult Macular Dystrophy (OMD) was diagnosed based on our genetic and clinical findings.<br />
Conclusions:
The complementary use of en face and cross-section high-resolution retinal imaging tools allows to detect and to track pathological retinal changes with high accuracy over time. The quantitative assessment of photoreceptor survival or loss, based on AO imaging, is valuable for monitoring disease progression at a cellular level.<br />