Visual acuity measures the sharpness and clarity of vision. Eye care professionals assess this using the Snellen eye chart, a standardized tool that quantifies how well an individual can discern letters or symbols at a specific distance.
What 20/70 Vision Means
When an eye care professional states someone has “20/70 vision,” it means that what they can clearly see at 20 feet, a person with typical 20/20 vision can see from 70 feet away. This assessment is typically done using a Snellen chart from 20 feet away.
Having 20/70 vision in one eye differs from having it in both. When only one eye has this reduced acuity, it is referred to as monocular vision impairment. While the brain often adapts by relying on the stronger eye, the affected eye still processes a blurred image. The World Health Organization classifies 20/70 vision as moderate visual impairment or moderate low vision. If this level of vision cannot be improved with corrective lenses, it is considered low vision.
Implications for Daily Life
Experiencing 20/70 vision in one eye can present practical challenges in daily activities, even with a strong fellow eye. Depth perception is a key area of impact, as it relies on the brain receiving slightly different images from both eyes to accurately judge distances. With one eye having reduced clarity, the brain receives less precise information, affecting the ability to gauge how far away objects are. This can make tasks like reaching for objects, pouring liquids, or navigating uneven terrain more difficult, as depth cues are compromised.
Driving can also be impacted, with vision requirements varying by state and country. Some jurisdictions may allow restricted licenses for individuals with 20/70 vision or worse, potentially limiting driving to daylight hours or requiring specific vehicle modifications. Even if legally permitted, impaired depth perception can increase the risk of motor vehicle accidents.
Beyond driving, activities requiring fine visual discrimination or precise spatial judgment can be challenging. Reading may require holding materials closer or using magnifiers. Sports that depend on hand-eye coordination or judging object speed and distance, like baseball and tennis, can become more difficult. Certain occupations demanding excellent binocular vision, such as operating heavy machinery or detailed assembly work, might also pose challenges. The brain often learns to compensate by relying on other visual cues and head movements, but this adaptation process takes time and conscious effort.
Causes and Potential Solutions
Several conditions can lead to 20/70 vision in one eye. Refractive errors like nearsightedness, farsightedness, or astigmatism are common and often corrected with glasses or contact lenses. If severe or uncorrected, these can lead to amblyopia, or “lazy eye,” where the brain favors the stronger eye, and the weaker eye fails to develop normal vision. Amblyopia is a leading cause of monocular vision loss in children and young adults.
Other causes include cataracts (clouding of the eye’s natural lens) and eye diseases like macular degeneration, glaucoma, or diabetic retinopathy. Eye trauma can also result in reduced vision. The specific cause determines the most appropriate course of action.
Solutions vary by diagnosis. For refractive errors, corrective lenses are typically the first step. For amblyopia, especially in children, treatments like patching the stronger eye or using atropine eye drops can encourage the weaker eye to develop better vision. Vision therapy, involving eye exercises, can improve visual skills, eye coordination, and the brain’s processing of visual information from the affected eye.
For cataracts, surgical removal of the cloudy lens and replacement with an artificial intraocular lens can improve vision. While cataract surgery has a high success rate, it may not restore 20/20 vision, and some individuals may still require corrective lenses. For conditions like macular degeneration or glaucoma, medical treatments such as injections or eye drops might slow disease progression and preserve remaining vision. When vision loss is irreversible, low vision aids (magnifiers, telescopes) and vision rehabilitation services can help individuals maximize remaining vision and maintain independence.