Simple perception test can accurately predict success of laser surgery for age-related vision loss

by European Society of Cataract and Refractive Surgeons

edited by Gaby Clark, reviewed by Robert Egan

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Laser blended vision is a treatment for presbyopia, the natural deterioration of our ability to see things close up that develops in people 40 and older. This type of laser surgery aims to correct one eye for seeing clearly in the distance and the other for near vision. It relies on the brain's ability to coordinate both eyes for clear vision at all ranges, which most, but not all, people can do.

New research presented today (Sunday) at the 44th Congress of the European Society of Cataract and Refractive Surgeons (ESCRS) shows that a simple test using standard eye-testing equipment and a patient's own perception can accurately predict whether this type of surgery will be suitable for each patient.

The research was presented by Brendan Cummings, a consultant ophthalmologist at the Wellington Eye Clinic in Dublin, Ireland. He said, "When people develop presbyopia, they may need different lenses to see objects that are near and far away, for example, two pairs of glasses or bifocal lenses. Laser blended vision is a procedure that aims to give people the ability to see clearly at all distances without the need for glasses, but because it relies on the brain's ability to blend what can be seen by two eyes with different abilities, it does not work for every patient."

In order to test whether laser blended vision is suitable for a patient, Cummings and his colleagues used a phoropter. This is the machine used in standard eye tests, which allows an ophthalmologist or optometrist to switch between many different lenses to measure refractive error and select the correct prescription.

The researchers begin the test by finding the correct lenses to maximize a patient's distance vision, then ask patients to mentally benchmark this as 100%. Next, they defocus just one of the patient's eyes by making it short-sighted and ask how this compares. The whole process is repeated with the other eye defocused.

If patients say their vision is at least 80% as good with one eye defocused, this suggests they will be able to successfully blend the view from their eyes and are suitable for the laser surgery. The test also allows ophthalmologists to identify which of the patient's eyes is dominant so it can be treated for distance vision, with the nondominant eye treated for near vision.

The study included 1,341 patients with a variety of vision problems (short-sighted, long-sighted or neither). Using the test before laser surgery identified a small number of patients who were not suitable for the treatment (30 people, or 1.66%). There was also a very high success rate following the test and laser surgery, with 96.9% of patients successfully adapting to their laser blended vision.

Cummings said, "We found that a simple, low-tech assessment of perceived distance vision and eye dominance has a very high predictive value for a patient's tolerance of blended vision. This is true for all patients regardless of their prescription before surgery.

"This means we can learn about how patients' brains process vision before surgery to screen out patients who are not good candidates for blended vision. This approach is valuable for clinicians too, as we want to provide the correct treatment strategies for each individual patient."

Dr. Joaquín Fernández, ESCRS secretary, CEO of Qvision and medical director of the Andalusian Ophthalmology Institute at Vithas Hospitals, Almería, Spain, who was not involved in the research, said, "We know that our vision tends to deteriorate as we reach our 40s. In particular, we struggle to see things close up, which means things like reading text can become difficult. This condition, known as presbyopia, happens because the lenses in our eyes become less flexible over time. In the past, we have relied on glasses to treat the problem, but more and more alternative options are available, including surgery.

"Both patients and specialists need reliable criteria to determine whether an intervention is appropriate and to predict which patients are most likely to benefit. Although new technologies are currently being developed to assess sensory dominance in a more innovative way, these tools are not yet available to all professionals. Therefore, studies such as the present one are of considerable practical value, as they provide clinically applicable information for patient selection, treatment planning and the future assessment of new technologies from a cost-effectiveness perspective."

Key medical concepts

Presbyopia

Clinical categories

Ophthalmology Provided by European Society of Cataract and Refractive Surgeons Who's behind this story?

Gaby Clark

MA in English, copy editor since 2021 with experience in higher education and health content. Dedicated to trustworthy science news. Full profile →

Robert Egan

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