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Trisevgeni Giannakopoulou, Sotiris Plainis, Joanna Moschandreas, Ioannis Pallikaris, Miltiadis Tsilimbaris; Patients with severe impairment in one eye show improved performance to defocus-induced blur. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5133.
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It is widely accepted that monocular deprivation results in improved spatial visual performance in the non-deprived eye. The current study investigates whether patients with severe impairment in one eye show any advantages over subjects with normal binocular vision under blur conditions
Sixteen patients (age: 33±8) with severe visual impairment in one eye (VA ≤ at 1m), for a period longer than 2 years (10±8), participated in the study. Only patients aged < 50 years and with monocular deprivation onset > 9 years were included. Fifteen more participants (age: 28±5) with normal binocular vision served as the control group. The effect of defocus, induced by positive lenses up to 2.50D, on the pattern reversal Visual Evoked Potential (VEP) and on visual acuity (VA) was assessed. VEPs were elicited using reversing 10 arcmin checks (4 reversals/sec). The stimulus subtended a circular field of 15 degrees with 100% contrast and 30cd/m2 mean luminance. VA was measured under the same conditions using ETDRS charts. All measurements were performed at 1m viewing distance with best spectacle sphero-cylindrical correction and natural pupils. Pupil diameter was measured with an infrared camera. Performance of the control group was tested both monocularly (dominant eye) and binocularly
In normal subjects VA was always better with binocular than with monocular vision, with the difference being greater for higher levels of retinal blur. In subjects with one functional eye, average VA was less affected by defocus than the monocular values of normal controls. Similarly to VA measurements, average implicit times of the P100 component of the VEPs were shorter in all cases with binocular than monocular stimulation in controls. The effect of defocus on VEP P100 latency (see fig.1) in one-eyed patients was similar to that exhibited in controls under binocular viewing conditions. Note that pupil diameter was on average greater in patients with one eye (5.5±0.4mm) compared to controls under monocular (5.1±0.5mm) and binocular (4.5±0.5mm) vision
Both subjective and electrophysiological results show that patients with one functional eye exhibit better performance under conditions of retinal blur compared to the monocular vision of control normals. These findings are consistent with growing evidence supporting functional changes as a result of altered experience or injury in the adult vision system
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