Contact lens substitution can cause discomfort, adverse events
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Few soft contact lens types perform identically in the clinical setting, so substitution of a prescribed lens can result in patient dissatisfaction and adverse events, according to a review article in Contact Lens and Anterior Eye.
“[As practitioners and researchers], we were concerned that there was growing support, particularly since the pandemic, toward buying things online,” co-author Lyndon Jones, BSc, PhD, DSc, FCAHS, FCOptom, DipCLP, DipOrth, FAAO, FIACLE, FBCLA, professor at University of Waterloo and director of the Centre for Ocular Research & Education, told Healio Optometry.
Online contact lens sellers may substitute cheaper lenses for those that were prescribed, Jones said.
“Some patients can pretty much wear anything, but the majority of patients have been prescribed a particular lens, particular replacement period and particular material and design because that’s the one that works best with their ocular surface,” Jones said.
He said he put together a group of well-respected practitioners and researchers to conduct an evidence-based review, systematically selecting 16 lens properties for which, “if you were to not prescribe that particular element, there is a potential opportunity for things to go awry,” Jones said.
According to the study, the parameters were surface treatment, internal wetting agent, oxygen permeability, water content, modulus, total diameter, back optic zone radius, thickness, edge profile, back surface design, optical design, power, tint, UV protection, wearing modality and replacement frequency.
Jones and colleagues wrote that their objective was to present evidence from contact lens literature to show “why all contact lenses are not the same and to consider the potential consequences of inappropriate lens substitution.”
Jones said that the researchers were surprised by the number of studies “that actually supported the fact that substitution without consultation can produce complications.”
“Given the wide range of parameters and properties available, few soft contact lenses are identical in their clinical performances,” the researchers said.
They concluded that substitution of 15 out of 16 of the properties evaluated resulted in between one and six potential aspects of patient dissatisfaction and adverse events. The only exception was back surface design.
“Probably the reason for that is that very few companies actually disclose what their back surface designs are,” Jones told Healio.
“Some of these [online supply] companies may come back and say they’ve done substitution, and the patients have been OK,” he said. “But how do you know they’re OK? Are they still wearing the lenses? How do you know their wearing time didn’t go down or that they weren’t as comfortable at the beginning of the month as they were at the end of the month? You don’t know because you’re not collecting the data.”
Jones said some patients may have “eyes like concrete,” but not the majority.
“We’ve had situations where companies have made incredibly small changes to a lens design and perhaps tweaked the edge format or made a tiny change to the midperipheral thickness or something apparently as inconsequential as changing the engraving on the lens that shows whether or not it’s inside out — and some patients know it, as they are incredibly impacted by even the most subtle change,” he said.
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