Comparison of Near-infrared and Short-wavelength Autofluorescence in Retinitis Pigmentosa

Purpose: To compare near-infrared autofluorescence (NIR-AF) and short-wavelength (SW) AF in retinitis pigmentosa (RP) and assess their relationships to underlying retinal structure and visual function.

Methods: SW-AF, NIR-AF, and spectral domain optical coherence tomography (SD-OCT) images were acquired from 31 patients (31 eyes) with RP and registered to each other. Microperimetry was performed on a subset of 12 patients. For both SW-AF and NIR-AF images, three independent observers measured the area enclosed by the outer border of the hyperautofluorescent ring and the distance from the fovea to the outer and inner border of the ring. For SD-OCT images, the distance from the fovea to the location where the inner segment ellipsoid (ISe) band became undetectable was measured.

Results: All eyes had a hyperautofluorescent ring on both SW-AF and NIR-AF. The position of the outer border of the ring was similar for both modalities. On NIR-AF the signal outside the ring was lower than inside the ring, resulting in a high contrast between the two areas. Also, the inner border of the ring was closer to the fovea on NIR-AF than SW-AF, corresponding to a location on SD-OCT where the ISe band was at least partially intact. Visual sensitivity was relatively preserved within the ring, reduced across the ring, and markedly decreased or nonrecordable outside the ring.

Conclusions: SW-AF and NIR-AF are both useful for monitoring disease progression in RP; however, NIR-AF may have advantages clinically and could unveil a process that precedes the formation of fluorophores that emit the SW-AF signal.