A few times during the life of The Eye Doc Blog I’ve been approached by numerous merchandisers to review or place banner ads promoting pinhole glasses. This begs the question do pinhole glasses work? The simple answer is it will make the image a little clearer and much darker. Comparing the vision from pinhole glasses to that attained by prescription lenses is like comparing your vision at midday versus 20 minutes after the sun sets. OK, maybe pinhole glasses aren’t that good. Pinhole glasses however do have a valuable purpose.
How Do Pinhole Glasses Work
First let’s discuss how prescription lenses focus light on the eye. Prescription lenses focus light on the fovea (the most sensitive part of the retina where we have our best visual acuity) by taking all of light that is entering the eye and focusing it at one point, on the fovea. The further the light is from the center of the pupil the more it most be focused to allow us to see clearly. Light that enters the pupil at the center does not have to be focused at all. This is how pinhole glasses work. Pinhole glasses block out all of the light in the periphery that must be focused in order to hit the fovea and allows in only the light that enters directly into the center of the pupil and thus does not need to be focused.
Do Pinhole Glasses Serve Any Purpose
Pinhole glasses are used in a doctor’s office to see if a patient, presenting with a red eye, for instance, can see better if she was wearing her glasses. As an example, a new patient presents to an eye doctor’s office with a red eye. After we have asked them the typical questions to provide some history about her red eye we want to see how well she is seeing. Often, a patient with a red eye was driven to the office by someone else and didn’t bring their glasses. After we check their vision we see that they have 20/80 vision in their red eye. Now the question becomes is their poor vision due to not wearing their glasses or is there another cause? Enter pinhole glasses, or more likely a pinhole occluder (a paddle with lots of little holes in it). We recheck our patient’s vision while she is looking through all of those little holes and lo and behold her vision through the pinhole glasses is 20/30. It’s still not 20/20, however we now have an additional degree of comfort that if she was wearing her glasses her vision would be normal. A pinhole is used to see if the vision is likely to improve with glasses.
So there you have it. Pinhole glasses, while certainly not a substitute for prescription eyewear, do serve a purpose as a screening tool for refractive conditions.