Abstract
Purpose :
Two-color dark-adapted perimetry (2cDAP) is an emerging clinical tool for characterizing the pattern of rod versus cone-dependent deficits across a patient’s visual field; 2cDAP has become important in gene-therapy clinical trials given its ability to localize and quantify changes in rod-driven responses. However, custom modifications of static perimeters are often made, limiting their widespread use and comparability across clinical sites. This observational clinical study tested the hypothesis that a commercially available, unmodified Octopus 900-Pro perimeter can characterize rod function by detecting a 2 log-unit difference in retinal sensitivities in healthy subjects between blue and red (450 nm and 610 nm wavelength) stimuli, as expected based upon validated spectral sensitivity curves.
Methods :
Ten healthy volunteers with no retinal pathology participated in this IRB-approved study (23-60 years old; 3 females). Subjects were tested with standard (unmodified) Octopus 900-Pro perimeters at the Casey Eye Institute (CEI, n=4) and the Illinois Eye and Ear Infirmary (IEEI, n=6). Testing of the right eye with appropriate refractive correction for measurements within the central 20-degrees of the visual field was performed (left eyes were patched). Fifteen locations from 45o nasal to 60o temporal were tested along the horizontal meridian of the visual field using a Goldmann III stimulus. Testing parameters and statistical analysis were performed as previously described.
Results :
An unmodified Octopus 900-Pro perimeter utilized at two clinical sites successfully detected an approximately 2-log difference in threshold values for blue compared to red stimuli outside of the fovea in healthy subjects (Figure 1), which corresponds to the expected difference for rod sensitivity to blue vs red stimuli based on spectral sensitivity curves. In the rod-free fovea, red and blue thresholds were equivalent, consistent with the cone-pathway mediating foveal sensitivity.
Conclusions :
Commercially available, unmodified Octopus 900-Pro perimeters may be used to reliably measure rod-photoreceptor function. Thus, custom device modifications are likely not necessary for most clinical and research evaluations of retinal degeneration patients, including potentially for monitoring disease progression and response to gene-based therapies.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.