Abstract
Purpose::
To use high resolution and contrast imaging techniques to reveal microscopic retinal structures, including individual retinal pigment epithelial (RPE) cells in human eyes with inherited retinal disease.
Methods::
Adaptive optics scanning laser ophthalmoscopy (AOSLO) was used to image the macular region in patients with retinal degenerative diseases including two patients with cone-rod dystrophy (CRD) and one with bilateral progressive maculopathy. The AOSLO used a low-coherent 840 nm light source for imaging over a 1.2 degree field of view at 30 frames per second. Images were generated from video sequences from which larger field montage images were constructed. Custom written software was used to determine spatial statistics of cell arrays in the images. Fundus-related microperimetery (MP-1, Nidek Technologies America Inc., Greensboro, NC) was used to correlate visual function with the visible structure in one patient with advanced CRD.
Results::
AOSLO images showed patches of intact cone photoreceptors in all the retinal degenerations patients studied. However, AOSLO images also revealed areas with an array of hexagonal structures, presumably RPE cells, in regions where it appeared that cones were missing. In the CRD patient with advanced disease, the RPE cells were visualized in an annular region surrounding a cone-preserved central area. In the two other patients the appearance of RPE cells was more sporadic, appearing in patchy areas where the cone mosaic was not present. The RPE cell shape, size and distribution compared well with measurements from the literature. MP1 microperimetry results indicated scotomas that corresponded to the locations where RPE cells were visible.
Conclusions::
RPE cells in healthy human eyes are not visible, as they are masked by the presence of a contiguous array of intact photoreceptors. Patients with hereditary retinal degenerations causing cone loss in the macula allowed visualization of RPE cells in areas where cones were missing. Regions with visible RPE cells demonstrated loss of visual function measured using microperimetry, suggesting the absence of overlying functional cones. We have directly visualized, for the first time, the mosaic of RPE cells in living human patients using an AOSLO.
Clinical Trial::
www.clinicaltrials.gov NCT00254605
Keywords: imaging/image analysis: clinical • retinal pigment epithelium • macula/fovea