Abstract
Purpose: :
To investigate macular photoreceptor structure with high–resolution in retinal degeneration patients.
Methods: :
Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) imaging was performed using a low–coherence infrared laser to generate high–resolution images of macular photoreceptors in 2 patients with retinitis pigmentosa (RP) and 1 with cone–rod dystrophy (CRD). AOSLO images were correlated with measures of macular function including best–corrected visual acuity, automated perimetry and multifocal electroretinogram (mfERG). Macular photoreceptor size and density, determined from AOSLO images, were compared between the patients and control values from 2 normal eyes.
Results: :
All 3 patients studied had visual acuity correctable to 20/20. In 2 RP patients with normal central visual field thresholds but moderate to severe macular photoreceptor dysfunction as measured using mfERG, cone structure, spacing and density were indistinguishable from normal within 2 degrees of the fovea. In contrast, in a patient with X–linked CRD who had elevated visual field thresholds and reduced mfERG amplitudes centrally, cone density was reduced by 50–75% below normal and cone spacing was approximately 2 times greater than normal values.
Conclusions: :
AOSLO imaging can be used to study macular cones with high–resolution in patients with retinal degenerations. Macular cones display different characteristics depending on the underlying disease. In RP patients with normal vision and central visual field, macular cones were indistinguishable from normal, while in a patient with CRD, macular cone spacing was greater and cone density was lower despite normal visual acuity. AOSLO imaging may provide insight into the mechanisms of cone vision loss in patients with both RP and CRD.
Keywords: retinal degenerations: hereditary • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • macula/fovea