A method for the prescription of inexpensive spectacles by non-specialist healthcare workers: S-Glasses

Abstract

Purpose Globally, 153 million people are visually impaired from uncorrected refractive error. The aim of this research was to verify a method whereby autorefractors could be used by non-specialist health-workers to prescribe spectacles, which used a small stock of preformed lenses that fit frames with standardised apertures. These spectacles were named S-Glasses (Smart Glasses). Patients and methods This prospective, single-cohort exploratory study enrolled 53 patients with 94 eligible eyes having uncorrected vision of 6/18 or worse. Eyes with best-corrected vision worse than 6/12 were excluded. An autorefractor was used to obtain refractions, which were adjusted so that eyes with astigmatism less than 2.00 dioptres (D) received spherical equivalent lenses, and eyes with more astigmatism received toric lenses with a 2.50 D cylindrical element set at one of four meridians. The primary outcome was to compare S-Glasses vision with the WHO definition of visual impairment (6/18). Where astigmatism was 2.00 D or greater, comparison with spherical equivalent was made. Mixed-model analysis with repeated effect was used to account for possible correlation between the vision of fellow eyes of the same individual. Results S-Glasses corrected 100% of eyes with astigmatism less than 3.00 D and 69% of eyes with astigmatism of 3.00 D or greater. Spherical equivalent lenses corrected 25% of eyes with astigmatism of 2.00 À 2.99 D and 11% with astigmatism of at least 3.00 D. Discussion S-Glasses could be beneficial to resource-poor populations without trained refractionists. This novel approach, using approximate toric lenses, results in superior vision for astigmatic patients compared with the practice of providing spherical equivalent alone.

Prevalence, associations and characteristics of severe uncorrected refractive error in the Australian National Eye Health Survey

“…Our data identified that older Indigenous Australians and those residing in outer regional locations may benefit the most from focussed resource allocation. There is real‐world evidence that spherical equivalent correction (only) derived from an auto‐refractor can be effective for correcting patients with low degrees of astigmatism . While we acknowledge this is not optimal, given close to 70% of Indigenous participants with severe uncorrected refractive error had a cylinder equal to or less than 1 dioptre, there may be a case for spherical lenses that fit frames with standardised apertures to be stocked in Aboriginal Health Services in the most inaccessible regions of Australia and health workers could dispense spectacles using auto‐refraction results.…”

“…Third, we did not perform subjective refraction, but rather relied on the refraction from an auto‐refractor. Nonetheless, there is evidence that refractions measured by auto‐refractors can correct vision close to that of subjective refractions . Furthermore, the accuracy of auto‐refractors have been shown to be sufficient for screening purposes .…”

Vision Stations: Addressing Corrective Vision Needs with Low-cost Technologies

“…In recognizing the key element of direct and immediate glasses provision, the benefits of self-refraction, and the potential of nonprofessional team members, our model is similar in spirit to other approaches. 12,28,29 The impact is also similar: rapid improvement in people's ability to achieve their goals and improved quality of life.…”

Self-adjustable glasses in the developing world

“…In the case of high-level spherical refractive errors, inaccurate self-refraction can occur because self-adjustable spectacles are incapable of correcting astigmatism, while with high-level cylindrical refractive errors, this can occur because the range of correction with this device is limited to −6 to +6 D. 9 , 32 Recently, a study has reported successful results for all types of refractive errors including astigmatism with “Smart Glasses” (S-Glasses; [Treacy MP, Dublin, Ireland]), which are a set of preformed lenses that fit frames with standardized apertures supported by an autorefractometer operated by a nonspecialist health worker. 43 Due to the availability of such alternatives, self-adjustable spectacle technology needs to be improved to meet the needs of a wide range of refractive errors if the load on existing eye-care systems is to be reduced.…”