Abstract
Purpose: :
To evaluate the architecture of the photoreceptor layer using adaptive optics imaging and to compare its clinical application over standard diagnostic tools in evaluating macular diseases.
Methods: :
We examined patients with macular hole, cone dystrophy and retinal pigment epithelitis (Krill’s disease). Visual acuity and color fundus pictures were taken and posterior segment was examined with Heidelberg Spectralis TM SD-OCT using high speed scans (40 kHz/s, axial resolution 7.0 um). Patients were subjected to additional imaging on a custom built multi-modal Adaptive optics-SLO utilizing a super luminescent diode (SLD) centered at 830 nm with a bandwidth of 62 nm to obtain high resolution reflectance images of the retinal photoreceptor mosaic in the macular region. The images were registered to create a large photoreceptor mosaic and were averaged to improve the overall signal to noise ratio. The AO-SLO mosaic was correlated with clinical OCT scans and fundus photographs.
Results: :
Morphological damage was detected at the single photoreceptor level using the AO-SLO that corresponded with abnormalities seen on standard OCT scans and fundus photographs. In the macular hole patient, AO-SLO imaging assessed the integrity of the cone photoreceptor mosaic before and after surgical repair. In rod-cone dystrophy, the adaptive optics imaging showed irregular rod-cone packing density along with the loss of cone cells in the macular region in both eyes of the patient when compared to the healthy adjacent zones. It is highly significant because clinical picture was simulating age related macular degeneration. In Krill’s disease, the disruption in the RPE layer was seen in SD-OCT slightly temporal to the fovea. AO system depicted changes in the mosaic pattern of the photoreceptor layer with areas of low packing density and dark regions of photoreceptor cell loss.
Conclusions: :
The adaptive optics can evaluate changes in the photoreceptor layer at a very high resolution that are currently undetectable by standard diagnostic methods. A combination of adaptive optics scanning laser ophthalmoscopy (AO-SLO) and SD-OCT provided complimentary views of the retina with enhanced lateral and axial resolution. Such heightened resolution of the retina may provide insights in early detection, prognosis and management of patients with vision threatening macular diseases.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors: visual performance • macula/fovea