Study Finds, Function of Clear Central Aperture Diameter wit
A Study was conducted to assess the effect of clear central apertures of different diameters with a defocused retinal periphery, using a range of visual performance tasks.

30 visually normal subjects were enrolled. Subjects wore five different spectacles during testing, all corrected for distance refraction, in random order: three single-vision spectacles with clear central apertures of 10, 12.5, and 15° radii with the periphery defocused. Static and kinetic visual field sensitivities, reading rate and comprehension, head movements, global saccadic tracking, and saccadic visual search were evaluated.

--Reading rate and comprehension did not differ across the five test conditions; however, increased head movement was found with the smallest aperture compared with the PAL condition with adjusted P less than .05.

--Static visual field sensitivity was reduced for all three apertures in eccentric regions when compared with the SVL and PAL conditions with adjusted P less than .05, whereas kinetic sensitivity did not differ for any lens condition.

--The 15° aperture was superior to the 10 and 12.5° apertures based on its similarity to the SVL and PAL spectacle conditions in head movement during reading, the Michigan Tracking Test, and the vertical results of the Developmental Eye Movement Test.

Conclusively, a 15° aperture surrounded by a peripheral myopic defocus has the least negative impact on visual performance. This discovery has significant implications for the development of spectacle and contact lens designs that enhance myopia therapy while minimizing visual performance.