We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained, higher-level lateral masking known as crowding. The trained task was contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea.

2 AbstractPurpose: The study investigated whether perceptual learning (PL) of a task consisting in detecting a low contrast Gabor patch flanked above and below by high contrast Gabor patches presented monocularly in the preferred retinal locus (PRL) of patients with macular degeneration (MD), improved their residual visual functions. Method:We measured contrast detection thresholds using both a Yes/No task (three MD patients and three controls) and a temporal two-alternative forced-choice task (2AFC; four MD patients and three controls).Results: Both tasks produced a significant improvement in contrast sensitivity for the trained target.However, only in the case of the temporal-2AFC this improvement depended on the target-toflankers distance. Furthermore, in both tasks PL improved visual acuity but with the temporal-2AFC task we found a higher degree of generalization of the training to untrained stimuli and tasks.In fact, we found a reduction of the crowding effect and an improvement of the contrast sensitivity for untrained spatial frequencies.Although PL is more effective with a temporal-2AFC task, it is also present with a Yes/No task, suggesting that PL reflects sensory enhancement, rather than improvement in decision mechanisms.Most importantly, follow-up tests on MD patients showed that PL effects were retained between four and eight months, suggesting PL induced long-term neural plasticity in the visual cortex. Conclusion:The results show for the first time that PL with a collinear configuration has strong, non-invasive and long lasting rehabilitative potential to improve vision in the PRL of patients with central vision loss.3

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The term retinitis pigmentosa (RP) indicates a heterogeneous group of genetic rare ocular diseases in which either rods or cones are prevalently damaged. RP represents the most common hereditary cause of blindness in people from 20 to 60 years old. In general, the different RP forms consist of progressive photo-receptorial neuro-degenerations, which are characterized by variable visual disabilities and considerable socio-sanitary burden. Sometimes, RP patients do not become visually impaired or legally blind until their 40-50 years of age and/or maintain a quite acceptable sight for all their life. Other individuals with RP become completely blind very early or in middle childhood. Although there is no treatment that can effectively cure RP, in some case-series the disease’s progression seems to be reducible by specific preventive approaches. In the most part of RP patients, the quality of vision can be considerably increased by means of nanometer-controlled filters. In the present review, the main aspects of the routine clinical and rehabilitative managements for RP patients are described, particularly focusing on the importance of specific referral Centers to practice a real multidisciplinary governance of these dramatic diseases.