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Rebecca Y. Weng, Ravi C. Bakaraju, Cathleen Fedtke, Klaus Ehrmann, Darrin Falk, Padmaja R. Sankaridurg, Arthur Ho, Brien A. Holden; Accommodative Response in Monocular and Binocular Viewing Conditions with Different Stimuli. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1362.
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Reduced blur-sensitivity has been associated with increased accommodative lag, development of myopia and its progression. It has been reported that theaccommodative response (AR) measured in binocular viewing condition (BC) could differ from that under monocular condition (MC). This study re-examines the effect of monocular and binocular viewing on static AR for different fixation targets (FT).
Six emmetropic and six myopic subjects (18-30 years) with a spherical equivalent prescription of 0 to -6.00D and astigmatism ≤ 1.00D were enrolled. Monocular and binocular steady-state AR were measured (5 repeats) using the Shin-Nippon NVision K5001 (Grand-Seiko, Japan) for target vergences of 3, 4 and 5D. The following FTs were used: modified (8-arms) Maltese cross, 6/12 and 6/24 Snellen E. All FTs were adjusted in size for their respective target distances. All myopic participants were corrected with 1-Day Acuvue Moist soft contact lenses (Vistakon, USA). Von Graefe technique was used to measure distance and near phorias. Participants’ right eyes were measured, while they viewed FTs under mesopic lighting both monocularly and binocularly. The order of testing for ocular conditions (OC) and FTs was randomized.
The mean spherical equivalent of the emmetropic and myopic groups was -0.08D ± 0.35D and -3.71D ± 1.86D respectively. Mean refractions obtained for both OCs and for all three FTs indicated a lag of accommodation at all near distances for both groups. No significant differences were found between monocular and binocular measurements in any refractive components (M, J0 and J45). Mean slopes of the AR functions were near identical for both OCs. The greatest difference between OCs was 0.11D at 33cm with the 6/24 Snellen E (BC: -2.28D and MC: -2.17D). Further, no significant differences (p>0.58) were found between the three FTs. The maximum difference between FTs was 0.13D at 33cm under MC (Maltese cross: -2.30D and 6/24 Snellen E: -2.17D) and 0.12D at 20cm under BC (6/24 Snellen Letter E: -3.94D and 6/12 Snellen E: -3.82D). Most participants were exophoric at all distances (range: +3 prism dioptre (p.d.) to -19p.d.), the magnitude of exophoria increased linearly with increase in object vergence.
We found no significant differences in the steady-state accommodativestimulus-response functions, in monocular and binocular viewing conditions, forboth emmetropes and myopes.
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