It is actually quite common for people to have some differences in vision between their two eyes. Small differences are normal and typically do not cause any problems. However, more significant differences may require correction with prescription eyeglasses or contact lenses to allow both eyes to work together properly. In this article, we will explore the causes for varying vision between eyes, when it becomes problematic, and what can be done to improve binocular vision.
What Causes Differing Vision Between Eyes?
There are several potential reasons why the two eyes may develop with different visual abilities:
Genetics
Genes play a major role in eye and vision development. Many aspects like nearsightedness, farsightedness, astigmatism, and eye muscle coordination have genetic influences. If there are differences in these traits between your parents’ eyes, you may inherit some of those differences.
Environmental Factors
Things like nutrition, sunlight exposure, toxin exposure, and injuries can affect each eye uniquely during development in the womb and during childhood. For example, if one eye had more sun damage or trauma than the other, vision clarity could be impacted.
Asymmetrical Focus
If one eye is more dominant and takes over focus, the weaker eye can gradually lose visual sharpness from inadequate stimulation during development. This often leads to subtle prescription differences between the two eyes.
Eye Misalignment
Conditions like strabismus (crossed eyes) or amblyopia (lazy eye) cause the eyes to focus independently and disrupt proper binocular vision. The misaligned eye typically develops much poorer vision ability.
Specific Eye Diseases
Certain eye disorders like cataracts, glaucoma, macular degeneration or diabetic retinopathy often affect one eye earlier or more severely. This understandably creates a difference in visual acuity between the eyes.
How Much Difference is Normal?
Small differences of up to 0.5 diopters in prescription strength between each eye are very common and generally inconsequential. To put this into perspective, a 0.5 diopter difference means one eye may see an object clearly at 20 feet, while the other eye needs to be at 16 feet for the same sharp focus. The brain automatically coordinates the two views effectively.
Larger prescription variations between eyes are also fairly common, though they begin causing more significant vision challenges. Differences of 1.0 diopters or more make it difficult for the eyes and brain to fuse the two disparate images together. This can lead to eyestrain, headaches, blurred vision, and reduced stereoscopic depth perception.
Typically, prescription variations greater than 2.0 diopters between eyes are considered abnormal and in need of vision correction. At this point, simply glasses or contacts alone may not fix the binocular vision issues satisfactorily, and vision therapy could also be required.
When Are Vision Differences Problematic?
Here are some key signs that having different vision in each eye has become a serious concern:
– Consistent headaches or eyestrain when reading or doing near work
– Difficulty sustaining clear binocular focus at all distances
– Frequent double vision when tired or backgrounds are busy
– Excessive squinting, rubbing eyes or tilting head to see better
– Poor hand-eye coordination or difficulty judging distances
– Motion sickness or dizziness with activities like reading in a car
– Aching eyes or visual fatigue after short periods of visual concentration
Experiencing one or more of these symptoms indicates a significant enough difference between the two eyes that correcting and aligning vision optimally will likely provide tremendous relief. Ignoring the problem usually allows it to gradually worsen over time.
Evaluating and Treating Unequal Vision
If you suspect your eyes have different vision abilities, the first step is a comprehensive eye exam by an optometrist or ophthalmologist. They have several methods to precisely measure and compare refractive errors and visual acuity between eyes. Cycloplegic agents may be used to reveal hidden focus problems. Ocular motility testing will check eye alignment and movement coordination. These results help diagnose specific conditions causing unequal vision.
The main treatment options include:
Corrective Lenses
Prescription glasses or contacts can compensate for clarity differences between eyes. Sometimes different prescriptions are needed for each eye, or visual acuity must be balanced by slightly over-minusing the better eye.
Patching Therapy
Patching the good eye forces the weaker eye to work harder, improving its focus ability. This is especially effective for children with significant refractive or eye alignment differences.
Vision Therapy
Specialized eye exercises and training activities can straighten eye alignment, build fusion skills, enhance focusing capability in the weaker eye, and train the brain to better integrate bilateral visual inputs.
Surgery
For cases like cataracts, glaucoma or strabismus, surgical intervention may be required to physically improve visual function to make vision between the eyes more equal.
With the right diagnosis and treatment plan, substantial improvements in binocular vision function are possible. This provides better visual clarity, comfort and reduced eyestrain for work and daily living. If you suspect your vision is unequal between eyes, see an eye doctor to discuss the options.
Conclusion
Mild differences in vision between eyes are normal due to typical genetic and developmental variations. Small prescription discrepancies under 0.5 diopters are generally inconsequential. However, if the vision difference between your eyes is greater than 2 diopters, it can impair visual function and comfort significantly. Symptoms like headaches, double vision and poor eye coordination indicate a need for professional eye care. Precision measurement of visual acuity in each eye will determine if corrective lenses, vision therapy, patching or surgery can help align your eyes and optimize binocular vision skills for clear, comfortable sight.
