Purpose:
The vision loss in Stargardt (STGD) disease begins with a small, regular scotoma that, with time, becomes larger, irregular, and paracentric from eccentric viewing. Eventually, the peripheral field is affected. We present data on measures of field loss and on test-retest variability.
Methods:
32 eyes of 8 males and 8 females, average age 47.2 yrs (SD=16.0, range: 20.8, 66.8) with at least one mutant allele of ABCA4 were studied. IRB approval and informed consent were obtained. Static perimetry was performed on separate days, using the Octopus 900 perimeter (Haag-Streit, Köniz, Switzerland), stimulus size V, the GATE strategy, and a centrally condensed grid of 184 points extending from 56° nasally to 80° temporally. Using Visual Field Modeling and Analysis (VFMA) software, sensitivity data were fit with a thin-plate spline to create 3-dimensional models of the Hill of Vision (Figure), from which the sensitivity volume (dB-sr) for the total field (HOV), Total Volume Loss (TVL), and scotoma volume (SV) were independently measured for test and retest sessions.
Results:
The Table presents the intraclass correlation coefficients (ICC) and confidence intervals for HOV, TVL, and SV1 and SV2 as rated by the two graders. To avoid artificial inflation of the ICC, extreme observations were removed. Test-retest and grader agreements were strong for HOV and TVL, but variable for SV. Test-retest and grader agreements tended to be high for smaller scotomas but less so for large scotomas that approached the edge of the grid and when fixation was eccentric and unstable.
Conclusions:
VFMA enables quantification of the magnitude and extent of vision loss that can serve as endpoints for clinical trials. Improved fixation control during testing should reduce test-retest variability.
Keywords: imaging/image analysis: clinical • visual fields • retinal degenerations: hereditary