Does LASIK Surgery Affect Binocular Vision?

Lasik and binocular vision

Refractive laser surgery has continuously been developing and expanding since it was first introduced in the early 1990s and, today, it is a widely performed procedure amongst a large proportion of eye clinics throughout the world. Several methods are used in refractive laser surgery, and Laser In Situ Keratomileusis (LASIK) with femtosecond laser is usually the preferred procedure. As an increasing number of people undergo refractive surgery, and even if the refractive result after surgery is perfect, the outcome is not always successful. One of such outcome problems is the presence of Decompensation of binocular vision anomalies which is rarely mentioned in reports considering the outcome of refractive surgery such as LASIK. Although binocular inhibition in post-LASIK patients increases as the visual sensitivity difference between the two eyes increases, there is little understanding about how the LASIK affects their binocular function. The aim of this review article is to provide a review of the research concerned with binocular vision in people who undergo LASIK surgery.

While normal or comfortable binocular vision is not usually listed as a criterion for success of LASIK and binocular impairment was not mentioned as an adverse complication of LASIK by the American Academy of Ophthalmology on safety and efficacy of LASIK, binocular vision impairment can still be a potential threat to a successful postoperative outcome for some of the patients undergoing refractive surgery such as LASIK.

What is binocular vision?
Binocular vision can be defined as the ability to maintain visual focus on an object with both eyes, creating a single visual image. While lack of binocular vision is normal in infants, adults without binocular vision experience distortions in depth perception and visual measurement of distance.

What is binocular summation?
In normal circumstances, observers with normal vision usually perform better on visual tasks when using both eyes than they do when using either of the two eyes alone. This phenomenon is known as binocular summation.

Scientific and clinical evidence
One of the best ways of determining the effects of refractive surgery (LASIK procedure) on binocular vision is by comparing binocular vision pre-surgery values against post-surgery values. One of such studies was performed in Ciudad Victoria, México from May 30th 2007 until July 31th of 2008. The study was done in patients who decided to have LASIK for either myopia, hyperopia, with or without astigmatism. There were 15 patients; 10 women and 5 men in total with their age ranging from 24 to 39 years. The main key objective of the study was to find out if refractive surgery i.e. LASIK, DOES change the binocular vision values. At the end of the study, the results shown binocular vision was satisfactory. However, there slight were changes in phoria and binocular vision values which was probably due to the overcorrection of myopia and not due to the LASIK procedure, itself.

Therefore, the researchers concluded that LASIK surgery does not change binocular vision values. To avoid any overcorrection related errors, it was recommended that a full binocular evaluation should be done before refraction surgery such as LASIK. In other words, it is important to test binocular vision status before the surgical decision is made. It would also be highly desirable for refractive surgeons to lean on functional optometry in order to evaluate binocular vision.

Conclusion
Based on the above studies and discussion, one would like to stress the importance of awareness amongst eye care providers of potential binocular problems after refractive surgery. To prevent potential problems it is recommended to have a thorough history and binocular evaluation before any surgery is performed. Furthermore, it is necessary to have more similar research in order to state a predictable model of binocular vision results after surgery.

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