Pinhole Visual Acuity knew as Pinhole Vision is an important examination tool in the field of ophthalmology and optometry.
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What is Pinhole?
The pinhole is an eye shield with several small holes or one hole that allow light rays to directly reach the retina without the interference of optical problems of the eye. The pinhole vision test is an excellent method for screening uncorrected refractive errors such as myopia, hypermetropia, astigmatism and it also helps to rule out disorders of the ocular media.
How does pinhole work?
A pinhole cuts off all the peripheral rays and allows only a central parallel beam of rays to enter the eye and vision improvement is seen in cases of refractive errors.
The pinhole allows only central rays of light to enter the eyes so that looking through a pinhole improve vision in refractive errors.
The size of the hole in the pinhole is 1.2 mm.
A 1.2 mm aperture pinhole is commonly used in ophthalmology clinics.
Pinhole test interpretation
If the distance vision is less than 6/6 or 20/20 all patients should be asked to look through a pinhole and improvement if any in visual acuity should be recorded.
If the cause for diminution of vision is not the refractive error like cataract then improvement in vision is not seen. The results of the pinhole test can be summarized as.
- Visual acuity improves with pinhole cause is the refractive error, which can be corrected by appropriate refraction and correction.
- No improvement in visual acuity with pinhole causes is corneal causes like corneal opacity, corneal oedema, and causes in the lens like a cataract.
- The decrease in visual acuity with pinhole cause may be the central corneal opacity, central lens opacity, and macular diseases.
The main benefit of using this pinhole during refraction and visual acuity test is to differentiate the cause of decreased visual acuity which is due to the refractive error or any other pathological conditions of an eye. If Visual acuity is not improved with pinhole and the patient have less than 6/6 or 20/20 vision the further investigations and examinations were made by eye care professionals.
Pinhole eyeglasses (also known as stenopeic glasses which is derived from the Greek words for “little opening”) are eyeglasses having many small holes in their opaque metal or plastic surface. These holes have the effect of reducing the width of the bundle of diverging rays coming from each point on the viewed object.
Pinhole glasses have been marketed by various companies all over the world by making advertisement like Anti-myopia Pinhole Glasses, Eye Exercise glasses, Eyesight Improve Natural Healing, Anti-fatigue glasses and they also promote as they could permanently improve eyesight. However, there is no scientific evidence has been found to support these claims. Some studies have suggested that symptoms including tired eyes, eye strain, hot or burning sensation, eye discomfort, difficulty concentrating, blurred vision, and double vision were more severe with multi pinhole glasses.