The effect of pinholes of different sizes on visual acuity under different refracting states and ambient lighting conditions*

Abstract

Purpose: The purpose of this pilot study was to investigate the effect of different size pinholes on visual acuity (VA) at near (0.4 m) while various factors were altered. The alterations made involved accommodation and illumination.

Method: Four subjects were selected and their ages ranged from 7 to 14 years. Subjective refractions were performed and then near visual acuities were measured at 0.4 m under two different lighting conditions (460 lux and 1 lux) by adding stigmatic (or spherical) lenses of positive and negative powers in front of pinholes of diameters 1.5 mm and 2 mm.

Results: The results showed that there was an improvement in VA in most, however, the size of the pinhole played a minor role. Low illumination did have a drastic effect on our results not only by decreasing the amount of lenses used for near that gave more positive results, but also when the pinhole was placed in front of the subjects. According to Borish, the pinhole does improve VA by a
straight forward process of elimination produced by spherical aberrations of the eye. However, this did not seem to be the case in this study under conditions of low illumination.
Conclusion: The pinhole effect offers improvement in VA at near by reducing the amount of blupresented to the retina. This study showed that alsubjects had an improvement in VA of at least two
lines in high illumination. Pinhole size did not alte the results sufficiently thus suggesting that a pinhole, no matter the size, should increase the VA. However this was not the case when illumination was decreased.