The worse eye is not as bad as it seems to be in AMD cases

Effect of Disease Progression on the PRL Location in Patients With Bilateral Central Vision Loss

Purpose

To investigate the effect of disease progression on the monocular preferred retinal locus (PRL) of the better eye (BE) and worse eye (WE) of patients with central vision loss.

Methods

Fifty-one patients with bilateral macular diseases were included. The monocular PRL was recorded for each eye (N = 102 eyes) with the MP-1 microperimeter in two visits that were 458 ± 249 days apart. For each eye and visit, the PRL distance from the former fovea, polar angle, and scotoma size were measured. The change in PRL location from visit 1 to visit 2 was evaluated with the differential map analysis.

Results

Scotoma size increased significantly in both eyes. The PRL distance from the former fovea increased significantly from visit 1 to visit 2 in the BE, but not in the WE. The polar angle was relatively stable in both visits for the BE. The change in PRL location in the BE was predicted only by the PRL distance from the former fovea in visits 1 and 2, but not by polar angle or scotoma size. For the WE, the change in PRL location depended on the change in PRL location in the BE, rather than on measurements made on that eye.

Conclusions

Disease progression affects monocular PRL location differently in the 2 eyes. The results suggest a recalibration of the oculomotor system with its reference at the PRL from the BE.

Translational Relevance

These findings are important for deciding the course of treatment and/or for developing rehabilitation techniques focusing on PRL relocation.

Binocular contrast summation and inhibition depends on spatial frequency, eccentricity and binocular disparity

PURPOSE

When central vision is compromised, visually-guided behaviour becomes dependent on peripheral retina, often at a preferred retinal locus (PRL). Previous studies have examined adaptation to central vision loss with monocular 2D paradigms, whereas in real tasks, patients make binocular eye movements to targets of various sizes and depth in 3D environments.

METHODS

We therefore examined monocular and binocular contrast sensitivity functions with a 26-AFC (alternate forced choice) band-pass filtered letter identification task at 2° or 6° eccentricity in observers with simulated central vision loss. Binocular stimuli were presented in corresponding or non-corresponding stereoscopic retinal locations. Gaze-contingent scotomas (0.5° radius disks of pink noise) were simulated independently in each eye with a 1000 Hz eye tracker and 120 Hz dichoptic shutter glasses.

RESULTS

Contrast sensitivity was higher for binocular than monocular conditions, but only exceeded probability summation at low-mid spatial frequencies in corresponding retinal locations. At high spatial frequencies or non-corresponding retinal locations, binocular contrast sensitivity showed evidence of interocular suppression.

CONCLUSIONS

These results suggest that binocular vision deficits may be underestimated by monocular vision tests and identify a method that can be used to select a PRL based on binocular contrast summation.

Bilateral eccentric vision training on pseudovitelliform dystrophy with microperimetry biofeedback

Low vision patients with eccentric viewing (EV) use extrafoveal retinal areas to compensate for the loss of central vision. Such retinal loci are known as the preferred retinal locus (PRL). It is known that EV is accompanied by unstable fixation. Microperimetry systems with biofeedback training have been used as a rehabilitation aid to improve fixation stability in EV patients. Normally, only the best or dominant eye is selected for such rehabilitation. This case report describes the rehabilitation on both eyes by means of PRL relocation with MAIA microperimetry (Centervue, Padova, Italy) with biofeedback training technology of a 74-year-old woman diagnosed with adult pseudovitelliform dystrophy. The patient presented binocularly similar anatomical and functional characteristics with the PRL located over the dystrophic area. At the end of the 3 months rehabilitation period, the PRL was successfully relocated inferiorly from the fovea showing relevant visual acuity improvement.

Residual stereopsis in age-related macular degeneration patients and its impact on vision-related abilities: a pilot study

OBJECTIVE

To determine the effect of residual stereopsis on vision-related abilities of low vision (LV) patients with age-related macular degeneration (AMD).

METHODS

Prospective non-randomized observational case series. Inclusion criteria included documented AMD, LV with best corrected visual acuity (BCVA) of 20/50-20/400 in the better eye, and ages between 50 and 90 years. Stereoacuity was measured using the near Frisby Stereotest. Vision related abilities were documented with the VA LV VFQ-48 questionnaire.

RESULTS

Twenty-seven subjects with mean age of 84±6 years old were recruited, of which 59.3% (16/27) were female. 59.3% (16/27) of the subjects were not able to see any stereoacuity plate, 25.9% (7/27) had stereoacuity of 340s of arc (SOA), 11.1% (3/27) had stereoacuity of 170 SOA and 3.7% (1/27) had stereoacuity of 85 SOA. The mean Overall Functional Visual Abilities (OFVA) score was significantly higher in those with stereopsis (2.25±0.99) than those without stereopsis (1.50±0.92) (P=0.028).

CONCLUSIONS

LV patients with stereopsis have better OFVA than those without. Stereopsis should be considered as a component of LV rehabilitation and considered as an outcome measure in research and clinical practice.