Prescription Shooting Glasses
By Alton P. Chiu
About 4% of the worldwide population is visually impaired, so it is natural to adapt eyeglasses to aid marksmanship. Bullseye pistol shooters use a wireframe with a near focus lens tuned to the front sight for the dominant eye and occlusion of the other eye. However, they are not ideal for action matches (e.g. IPSC) or field use. This vignette explores how to adapt regular eyeglasses for “run-n-gun” purposes, namely the importance of optical center placement and options such as coating and materials.
The lens optical center is where light passes through without changing direction and causing distortions. When ordering glasses, opticians align the optical center with the everyday pupil position for best clarity during daily use. The problem arises from the fact that the everyday pupil position could be mismatched with the standing, sitting, and prone shooting positions. This misalignment causes distortions, blurred image, and color fringing that degrades accuracy and consistency of the sight picture.
Differing shooting positions utilize different parts of the eyeglass lens. Offhand and sitting rifle positions, as well as isosceles pistol stance, all share a similar pupil position, whilst the prone rifle position can place the pupil higher. Although keeping one’s head upright is good practice, that can prove challenging with the prone position especially on rifles with nonadjustable buttstocks. As a compromise, the author chose to average the pupil position of his sitting and prone rifle positions to achieve acceptable clarity across various situations.
Different rifles can also give different pupil position as the distance between the stock comb and the sight plane, aka Drop at Comb (DAC), can alter the head position. Open-sighted rifles such as Mauser 98s can have low DAC, leading users with longer faces to tilt their heads forward in order to align with the sight plane. This can position the pupil higher up on the lens. Modern rifles such as AR-15s, especially with a tall sight plane such as a lower-1/3 co-witnessed red dot sight, can have tall DAC. The resulting head-up stature can help limit pupil position shift between shooting positions. Because the sample...
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