Scanning laser densitometry and color perimetry demonstrate reduced photopigment density and sensitivity in two patients with retinal degeneration

Purpose. To test the feasibility of scanning laser densitometry with a modi fied Rodenstock scanning laser ophthalmoscope (SLO) to measure the rod and cone photopigment distribution in patients with retinal diseases. Methods. Scanning laser densitometry was performed using a modified Rodenstock scann ing laser ophthalmoscope. The distribution of the photopigments was calcula ted from dark adapted and bleached images taken with the 514 nm laser of th e SLO. This wavelength is absorbed by rod and cone photopigments. Discrimin ation is possible due to their different spatial distribution. Additionally , to measure retinal sensitivity profiles, dark adapted two color static pe rimetry with a Tubinger manual perimeter was performed along the horizontal meridian with 1 degrees spacing. Results. A patient with retinitis pigment osa had slightly reduced photopigment density within the central +/- 5 degr ees but no detectable photopigment for eccentricities beyond 5 degrees. A p atient with cone dystrophy had nearly normal pigment density beyond +/- 5 d egrees, but considerably reduced photopigment density within the central +/ - 5 degrees. Within the central +/- 5 degrees, the patient with retinitis p igmentosa had normal sensitivity for the red stimulus and reduced sensitivi ty for the green stimulus. There was no measurable function beyond 7 degree s. The patient with cone dystrophy had normal sensitivity for the green sti mulus outside the foveal center and reduced sensitivity for the red stimulu s at the foveal center. The results of color perimetry for this patient wit h a central scotoma were probably influenced by eccentric fixation. Conclus ion. Scanning laser densitometry with a modified Rodenstock SLO is a useful method to assess the human photopigment distribution. Densitometry results were confirmed by dark adapted two color static perimetry. Photopigment di stribution and retinal sensitivity profiles can be measured with high spati al resolution. This may help to measure exactly the temporal development of retinal diseases and to test the success of different therapeutic treatmen ts. Both methods have limitations at the present state of development. Howe ver, some of these limitations can be overcome by further improving the ins truments. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.