Abstract
Purpose :
To evaluate if sensitivity and just noticeable difference thresholds were modified in patients with retinitis pigmentosa (RP) and Stargardt disease (STGD1).
Methods :
We examined 29 normal observers (29±10 years), 19 RP (43±15 years) and 14 STGD1 (43±14 years) using a temporal contrast sensitivity procedure based on the silent substitution paradigm. L-, M-, S-cone and Rod isolating sine-wave modulations were tested with a dedicated LED stimulator at frequencies that stimulate single retino-geniculate pathway in the perifovea without intrusion by other pathways. L- and M-cones at low (parvocellular) and high frequencies (magnocellular), S-cones at low frequencies (koniocellular) and Rods at medium frequencies (rod driven pathway) were analysed. From the temporal contrast sensitivity procedure, two measures were extracted: the sensitivity and the just noticeable differences (JND). The first corresponds to the inverse of the absolute threshold i.e. the contrast at 50% probability of detection. The JND is the difference threshold and is calculated by subtracting the contrast at 75% probability of detection from the contrast at 25%. Then two Bayesian mixed models were produced to detect the influence of subject group (normal subjects and the two patient groups), of the post receptoral pathway and of the age of the observers on either the sensitivity or the JND thresholds.
Results :
Sensitivities of RP patients were close to normal. STGD1 patients displayed a large sensitivity decrease for most measurements. JND values of STGD1 patients were close to normal while RP patients had larger values than normal observers, specifically parvocellular and rod mediated pathways.
Conclusions :
The two studied perception parameters (sensitivity and JND values) display opposite differences in RP or STGD1 patients. The decreased sensitivity in STGD1 patients can be related to the macular degeneration. RP patients may display a larger uncertainty in stimulus detection because a larger retinal area is affected even though the retinal degeneration is subjacent to the stimulus in the perifovea. The use of JND may allow us to describe early effects of vision loss. Our results exhibit a potential complementarity of the sensitivity and JND methods to describe and follow the development of retinal diseases.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.