When people have strong refractive errors, they generally wear corrective lenses full-time. This allows them to navigate daily tasks without blurry vision and eye strain. However, when our optometrist recommends how often we should wear our lenses, our visual acuity is part of their recommendation.
Visual acuity represents how clearly you can see at a particular distance.
A visual acuity of 20/20 is standard for good vision. A ratio that deviates from this standard, like 20/40 or 20/60 suggests that corrective lenses should be worn full-time.
Understanding Visual Acuity
Visual acuity is a term used to describe our visual clarity.
Visual acuity measures the clarity or sharpness of your vision by determining your ability to see fine details at specific distances.
It’s commonly used to identify refractive errors like myopia, hyperopia, or astigmatism that cause objects at various distances to appear blurry.
Beyond these refractive errors, poor visual acuity could suggest conditions like cataracts, which cloud the eye’s natural lens, or macular degeneration, a leading cause of vision loss.
Visual acuity lets us navigate the world and contributes to our daily functioning and overall quality of life. It affects various activities like reading, driving, and recognizing faces. High visual acuity allows people to perceive fine detail, which is helpful for tasks that require precision, while low visual acuity means your vision is blurry and distorted.
Visual acuity is assessed during your routine eye exam and goes hand in hand with evaluating your vision prescription during the appointment.
Breaking Down the Visual Acuity Ratio
Visual acuity is measured as a ratio, the most well known of which is 20/20 vision.
The first number, often 20, represents the distance in feet between you and the eye chart. The second number denotes the distance at which a person with normal vision could read what you were able to read off the chart.
So, for instance, having a visual acuity of 20/40 means that what you can see clearly at 20 feet can be seen clearly by someone with normal vision at 40 feet. In other words, your vision is weaker than normal.
This ratio provides a standardized measure of vision clarity. If your visual acuity ratio deviates significantly from 20/20, it suggests that your vision may need correction.
Visual Acuity vs Refractive Error
While visual acuity provides a glimpse of how well you see at a standardized 20 feet, it’s not the same thing as refractive error.
Refractive errors, like myopia or astigmatism, occur when the shape of your eye prevents light from focusing correctly on the retina, leading to blurry vision.
Visual acuity describes the result of how well you see, whereas refractive errors pinpoint the underlying issue affecting your sight. These two values are interconnected, as refractive errors directly impact your visual clarity.
However, the value of the ratio doesn’t necessarily indicate your refractive error. For instance, having a visual acuity of 20/40 only tells us that your vision isn’t as sharp as the typical 20/20 standard. It doesn’t give as much information about what kind of refractive error you have.
What Prescription Needs to Wear Glasses Full-time
Whether you need to wear glasses full-time depends on your visual acuity and refractive errors. A prescription detailing these values offers insight into whether correct lenses are necessary.
People with significant refractive errors often benefit from wearing glasses throughout the day. For example, someone with high myopia should wear their glasses full-time for clear vision and to reduce the onset of headaches and eye strain.
A visual acuity of 20/20 is considered the benchmark of good vision. When a person’s visual acuity diverges significantly from this benchmark, for instance, at 20/40 or 20/60, it means that their vision might not be sharp enough to navigate some daily tasks without support.
But the strength of your refractive error also plays a role in your optometrist’s suggestion for wearing glasses full-time:
- Moderate to severe myopia: A person with a moderate myopic or nearsighted prescription will benefit from wearing glasses or contacts continuously.
- High hyperopia: A person with a high hyperopic or farsighted prescription should wear corrective lenses to avoid eye strain during close-up tasks.
- Moderate to severe astigmatism: Those with moderate to severe astigmatism should generally also wear lenses full-time.
Ultimately, based on your visual acuity and refractive error, your optometrist will explain whether you’re required (or strongly advised) to wear your glasses full-time.
Schedule an Appointment
Understanding the role of visual acuity and refractive errors can help you make informed decisions about how frequently you should wear your corrective lenses. This helps preserve your vision, ocular health, and the safety of yourself and others.
Connect with our team at Pack & Bianes Optometry to schedule a routine eye exam.
