Mapping the Dense Scotoma and Its Enlargement in Stargardt Disease

Abstract

Purpose To describe the enlargement of the dense scotoma over time in Stargardt disease, and to highlight methodological issues in tracking enlargement. Methods Retrospective study of patients with full mapping of the border of the dense scotoma using the MP-1 for at least two visits. Results Fourteen eyes of 7 patients met this criterion. Patients had median of 3 visits (range 2 to 5), with median total f/u of 4.5 years (range 1.5-8). Mean baseline visual acuity was 20/56 (range 20/25-20/200), mean baseline dense scotoma area was 2.23mm2 (range 0.41-5.48), and mean dense scotoma enlargement rate was 1.36mm2/year (range 0.22-2.91). The younger patients tended to have more rapid loss of visual acuity, which tended to plateau when the VA was 20/100 or worse. The patients who developed Stargardt before age 20, and the single patient who developed Stargardt disease after age 40, had more rapid enlargement rates, with preservation of central vision in the oldest patient. The ability to precisely define the dense scotoma area was dependent upon the density location of the points tested; this led to significant variability in the assessment of the scotoma enlargement rate in 3 of the 7 patients. The dense scotoma was not described adequately by the extent of the homogeneous dark area on fundus autofluorescence imaging. Conclusion Microperimetry is necessary for mapping the scotoma in patients with Stargardt disease, since current imaging is not adequate. Standardized grid testing, plus a standardized procedure for refining the border of the dense scotoma, should allow more precise testing and longitudinal assessment of enlargement rates.

Peripheral Visual Fields in ABCA4 Stargardt Disease and Correlation With Disease Extent on Ultra-widefield Fundus Autofluorescence

“…29–32 The measurement of the area of central scotomas in patients with STGD is also challenging because fixation is decreased. 31,33,34 Microperimetry has proven to be valuable in measuring macular function and in detecting disease progression in patients with STGD. 31,35–39 However, its utility is limited to the macular region.…”

“…31,33,34 Microperimetry has proven to be valuable in measuring macular function and in detecting disease progression in patients with STGD. 31,35–39 However, its utility is limited to the macular region. Although STGD universally starts in the macula, over time the disease progresses toward the periphery.…”

“…15 Therefore, in patients whose transition areas of progression are located outside the posterior pole, the widefield kinetic perimetry may be suitable to follow these peripheral changes. Moreover, given that in STGD the area of the central scotoma usually exceeds the area of hypoautofluorescent abnormalities in the posterior pole, 31 it’s also possible that the peripheral areas of abnormal hypofluorescence may be underestimated on the peripheral visual fields. Thus, the UWF-FAF alone may not be adequate to estimate the areas of peripheral vision loss and widefield kinetic perimetry may be still necessary.…”

Juvenile Macular Degenerations

“…Deficits in color vision 33 and central visual field 34 progressively increase typically accompanying a decrease in visual acuity.…”

Abnormal Visual Function Outside the Area of Atrophy Defined by Short-Wavelength Fundus Autofluorescence in Stargardt Disease

“…Patients underwent microperimetry, visual acuity testing, SW-AF and OCT imaging every 6 months. 17 In our center, we supplemented the protocol microperimetric testing 18 with dense scotoma mapping 10 to define the full extent of the dense scotoma when it exceeded the grid used for testing. This study afforded us the opportunity to assess retinal function outside the area of central atrophy and loss of autofluorescence, and to determine to what extent photoreceptor function is compromised in retinal areas unexpected to have functional loss based on the SW-AF.…”