Ease of adaption was the most important factor in predicting which spectacle prescription a participant preferred, showing there is a need for practices to have a smooth adaptation process with every patient when prescribing spectacles. Photo: Apostolos Vamvouras/Unsplash.

Optometrists know all too well the challenges of relying upon a patient’s subjective refraction, given its inherent imprecision, but even one’s best efforts to deliver optimal clarity can fall wide of the mark if the patient struggles to adapt to their new glasses. While spectacle prescriptions are typically written to provide best visual acuity (VA), for some patients an adjustment to ease adaptation is incorporated. A new study shows the soundness of that approach.

Researchers sought to understand which factors predict patient preference between spectacle prescriptions by comparing ease of adaptation, subjective quality of distance vision and optimal distance visual acuity between two pairs of glasses. They found that patients by and large preferred the prescription that was easier to adapt to after either subjective refraction or autorefraction results were modified with that goal in mind, showing that a smooth adaptation process is crucial even if it comes at the expense of distance VA.

This study included a 196-patient dataset in which participants wore two prescriptions, one based on the subjective refraction of an optometrist modified by their judgment to ease adaptation and the other from autorefractor results modified for ease of adaptation by an algorithm. This was a retrospective analysis of a prior study’s data; thus, the test conditions could not be altered to suit this new study’s desired outcomes. The autorefraction vs. subjective refraction design was intended for the prior study; however, as that work included a large dataset of prescriptions modified for ease of patient adaptation, it was well-suited to the present analysis.

Options were worn for three weeks each. Participants then responded to questions about which Rx they preferred and their quality of distance vision and ease of adaptation (on a 0 to 10 scale). Presbyopes did not wear progressive lenses and were only asked to consider distance acuity with single vision lenses.

The researchers used logistic regression analysis to see which variables predicted participants’ responses to the question, “If you had purchased these spectacles for $100, would you be happy with them?” The original study was done in 1996; price would be $200 when adjusted to 2023 value, according to the paper published about the study.

Of all subjects, 94% preferred the prescription deemed easier to adapt to but only 59% preferred the prescription with better subjective quality of distance vision and best visual acuity. Binocular distance visual acuities were not a significant predictor of participant preference or whether a participant said that they would have been happy to pay for a pair of spectacles. “This supports findings that many patients report difficulties adapting to new spectacles, and these problems have led to clinicians developing prescribing rules that allow easier adaptation and comfort with new spectacles,” the researchers explained in their paper for Clinical and Experimental Optometry.

 “While many experienced optometrists may consider adaptation when prescribing a new or changed prescription, there has been little evidence to date to support these prescribing decisions,” notes Amy Hughes, MCOptom, lead author of the study. “In this retrospective analysis, we were able to demonstrate that ease of adaptation is an important predictor of patient preference and acceptance of a new prescription, supporting prescribing for ease of adaptation even where this may somewhat reduce the best-corrected vison.”

As the researchers noted in their journal article, “Once the level of vision that is ‘clear enough’ for the patient has been reached, it is possible that prescribing for any clearer vision will not make the patient any happier with their spectacles and may increase the risk of patient dissatisfaction,” due to difficulties in adapting to a new Rx.

The researchers concluded that these findings highlight how important a smooth adaptation process is to patients. With previous studies finding that patients feel that they receive insufficient information and advice about adapting to new spectacles, there is a need for practices to take steps to ensure that patients have as easy an adaptation period as possible. “This should include information and advice about what to expect and how to get used to a new pair of spectacles, including what type of symptoms may be experienced and why this might happen, strategies to aid adaptation, likely timescales of adaptation and, crucially, what to do if there are difficulties in getting used to a new pair of spectacles and when and how to contact the practice for help,” the authors suggested. “This information should be given to all patients, and not just those with particularly large changes, as even small changes can cause issues for some patients.”

Commenting on prescribing habits in their paper, the researchers advised, “It may be that optometrists remain too wedded to prescribing their subjective refraction result and the best possible visual acuity. Although many optometrists would not hesitate to omit a -0.25D or -0.50D cylinder when prescribing contact lenses, the same patient would be unlikely to be given this option in their spectacles, even if the cylinder was oblique and potentially problematic.” New ODs tend to avoid straying away from using the best visual acuity, they observed, “with more experienced optometrists being more likely to adjust their subjective refraction result to support patient adaptation and comfort using the prescribing rules widely available in the literature.”

Hughes AR, Bullimore M, Elliott D. ‘Ease of adaptation’ predicts preferred spectacle prescriptions better than visual acuity: a retrospective analysis. Clin Exp Opt. January 18, 2024. [Epub ahead of print.]