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Amy Kalia, Luis Lesmes, Michael Dorr, Tapan Gandhi, Garga Chatterjee, Peter Bex, Pawan Sinha; Development of Contrast Sensitivity Following Extended Congenital Blindness. Journal of Vision 2013;13(9):281. doi: https://doi.org/10.1167/13.9.281.
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We report on the recovery of vision in patients who were treated for very early onset (<1 year) cataracts after long-term deprivation (8-19 years). Previously reported cases of sight restoration either had significant visual experience for the first few years, or were treated within the first half-year after birth [Fine, et al., 2003; Maurer, Ellemberg and Lewis, 2006]. Through Project Prakash, we had the opportunity to study a large number of patients in India who were blind since early in life and treated past the age for normal development of contrast sensitivity. Patients were tested in two sessions separated by six months; the first test session was conducted one week to 2 years after treatment. The pre-surgery acuity of these patients ranged from light perception to finger counting at a distance of one meter. Patients were tested binocularly on an iPad [Dorr, et al., ECVP 2012]. The test presented band-passed Lea symbols using a Bayesian adaptive method to estimate contrast sensitivity functions [Lesmes, et al., 2010]. Results show that all patients recovered some vision in the lower spatial frequency range, and some patients even showed peak sensitivities (thresholds<1%) that were equivalent to sighted controls, but shifted to lower frequencies. Some patients showed significant improvements after six months, suggesting neural adaptation to the newly acquired visual input, but the extent of improvement was highly variable across patients. The age, level of pre-operative vision (light perception vs. finger counting), and time since treatment did not predict the extent of improvement over time. These results suggest that the human visual system has the capacity to develop contrast sensitivity after long-term deprivation, but it is still unknown which factors influence the extent of recovery.
Meeting abstract presented at VSS 2013
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