Visual acuity refers to the sharpness or clarity of a person’s vision, which is typically measured at a distance. When an eye doctor determines a patient has 20/150 vision, it signifies a notable degree of visual impairment compared to the standard of sight. It indicates that the ability to see distant objects is significantly reduced.
Understanding the Snellen Scale
The measurement of 20/150 is derived from the Snellen chart, a standardized tool used to test distance visual acuity. This fraction compares the patient’s vision to that of a person with “normal” sight, designated as 20/20 vision. The first number (20) represents the fixed distance in feet at which the patient stands from the chart.
The second number (150) is the distance in feet at which a person with 20/20 vision could clearly read the same line of letters. Therefore, a person with 20/150 vision must stand at 20 feet to see an object clearly that someone with 20/20 vision can see from 150 feet away. This means the visual detail the average eye distinguishes at 150 feet is only visible to the patient when they are much closer.
The larger the second number in the fraction, the worse the visual acuity is considered to be. A person with 20/150 vision can only resolve details at 20 feet that are eight times larger than the smallest details a person with 20/20 vision can see at the same distance. The Snellen scale focuses solely on the central clarity of vision and does not account for other factors like peripheral vision, depth perception, or color vision.
Daily Life with 20/150 Vision
A visual acuity score of 20/150 results in concrete functional limitations, particularly for tasks requiring distance vision. Recognizing a familiar face across a moderate-sized room or parking lot becomes a challenge, often requiring the individual to be much closer for identification. Reading standard-sized print on signs, such as street names or roadside advertisements, is also significantly impaired at a distance.
Operating a motor vehicle is usually not possible with uncorrected 20/150 vision, as this level falls far below the legal driving threshold in most jurisdictions. Many states require vision to be corrected to at least 20/40 or 20/50 for a standard driver’s license. Without correction, a person with 20/150 vision cannot safely perceive hazards or traffic signals in a timely manner while driving.
This level of impairment often necessitates the use of various aids or modifications to maintain independence. Tasks like watching television from a typical viewing distance or reading a menu board can require extra effort or reliance on corrective lenses. The functional consequence of 20/150 vision is a world that appears consistently blurred and lacking in fine detail beyond a short range.
Next Steps: Causes and Corrective Measures
A visual acuity measurement of 20/150 is often the result of an underlying condition that affects how light focuses on the retina. The most common cause is a significant refractive error, such as moderate myopia (nearsightedness), hyperopia (farsightedness), or astigmatism. Myopia is particularly likely to cause poor distance vision at this level.
Other potential causes include the early stages of diseases like cataracts, which cause the eye’s natural lens to cloud, or minor issues affecting the retina or optic nerve. A mild case of diabetic retinopathy or macular degeneration could also present with this degree of visual loss. A comprehensive eye examination is necessary to accurately diagnose the specific cause of the reduced acuity.
Fortunately, 20/150 vision due to a refractive error can typically be fully corrected with prescription eyeglasses or contact lenses, often restoring vision to 20/20 or better. These lenses work by precisely adjusting how light enters the eye, ensuring it focuses directly onto the retina. If the vision loss is due to a disease that cannot be fully corrected, eye care professionals may recommend specialized low-vision aids. These aids, such as powerful magnifiers or telescopes, are designed to maximize the remaining visual capacity and improve the quality of life.