Abstract
Purpose: :
Angioid streaks (AS) are a hallmark of pathology in Bruchs membrane in pseudoxanthoma elasticum (PXE). The natural course of AS involves narrow short radial discontinuous hypopigmented streaks, more pigmented lengthened and widened streaks and finally end–stage macular degeneration with or without CNV, diffuse choroidal sclerosis or helicoid peripapillary atrophy. The aim of this study was to investigate if functional impairment is correlated with morphologic severity and if fundus controlled microperimetry is capable of detecting functional deficits.
Methods: :
10 eyes of 10 patients were included (median age: 50 years; range 36–70 years). The diagnosis of PXE was based on the typical clinical features and mutation analysis in the ABCC6 gene. Patients were investigated by means of fundus biomicroscopy, digital fundus photography, digital fluorescein and indocyanin green angiography, cSLO fundus autofluorescence imaging, and optical cohorence tomography. Fundus controlled static threshold perimetry was performed with the MP1 (Nidek, Inc., Italy); Goldmann III stimuli (100ms) with a white background illumination were used with 4–2 test strategy. The range of luminance was 0–20 dB. At least 3 areas were tested inside the AS compared with at least 3 contiguous areas outside the AS in an area of 44 x 36 degrees. A difference of 5 dB between these areas was considered to be significant.
Results: :
AS were divided into 3 groups according their funduscopic appearance. In group 1 (4 eyes) subtle fine reddish AS with a diameter of 100–200 microns were measured and revealed mean differential light thresholds of 13.6+–4.5 dB of the AS compared with 13.0+–4.2 dB of the adjacent area. Group 2 (2 eyes) showed more pronounced grey lines with atrophic borders and revealed mean differential light thresholds of 6.9+–3.2 dB of the AS and 15.0+–2.7 dB of the adjacent area. Group 3 (3 eyes) showed atrophic AS and scars and revealed mean differential light thresholds of 0.6+–4.6 dB of the AS versus 15.1+–3.3 dB of the adjacent area.
Conclusions: :
There was close correlation of clinical stage of AS and functional impairment of retinal sensitivity. Subtle fine reddish AS (stage 1) may exhibit normal sensitivity, whereas stage 2 and stage 3 may show significant sensitivity loss of the corresponding neurosensory retina. This findings supports the notion, that AS may undergo progressive morphologic changes with concurrent alteration of the photoreceptor cells. Fundus controlled microperimetry appears to be a powerful tool to detect such alteration and to map retinal sensitivity in AS.
Keywords: retinal degenerations: hereditary • perimetry • imaging/image analysis: clinical