RESUMO
CLINICAL RELEVANCE: Optical magnification (OM), electronic magnification (EM), and assistive technology (AT) can be prescribed in low vision rehabilitation (LVR) clinics for near vision goals of patients. This study shows the prescription of OM has not decreased with increased availability of EM and AT. BACKGROUND: Near visual goals are a primary concern for patients with visual impairment. LVR providers can prescribe OM, EM and/or AT to help. With the rapid evolution and availability of EM and AT, we aim to evaluate if there have been changes in the prescription patterns of clinicians with respect to OM over time. We hypothesise that the increased availability of technology may result in declining prescriptions of OM and increasing prescription of EM and AT over time. METHODS: This retrospective study investigated near prescribing between 2008-2017 for 530 new patients to the LVR clinics. Examinations were performed by optometrists specialising in low vision. Near devices prescribed included OM and EM and AT. RESULTS: Most patients attending the LVR clinics were female, over 60 years old and had age related macular degeneration. Near visual goals were a primary concern of 97.2% of the patients. OM was most prescribed in the 0-19 and >60-year-old age groups. Within the 20-39-year-old age group there was the greatest number of both EM and AT prescriptions. OM was most prescribed in patients with visual acuity better than 6/60. EM and AT showed a trend of increasing prescription as visual acuity decreased. EM prescription peaked in <6/60 to 6/240 category while AT trended upwards from <6/21 to no light perception and peaked in patients with no light perception. Referral rates for additional rehabilitation services were 75.7%. CONCLUSIONS: This study shows that the prescription of OM is not declining even as the prescription and the breadth of electronic magnification and assistive technology available is expanding. OM continues to be a viable option for patients, especially in the youngest and oldest cohorts.
RESUMO
SIGNIFICANCE: This case report demonstrates a novel approach of using the optical principle of vergence amplification to correct for a visually impaired patient's ametropia while using a telescope system. This approach is easy to apply clinically. PURPOSE: The purpose of this study was to present a novel approach of correcting high myopia for a patient with visual impairment using a spectacle-mounted telescope. CASE REPORT: A 51-year-old man desired improved distance vision for television viewing and facial recognition. His refractive error was -18.00 diopter sphere in each eye with best-corrected acuities of 5/225 (20/900 Snellen equivalent) for the right eye and 10/225 (20/450) for the left eye. Over the years, multiple attempts at contact lens use were unsuccessful, and the patient used spectacle prescription. After evaluating telescope systems, the patient was successful with a 7 × 30 Beecher Mirage Keplerian telescope system. This system cannot be worn over glasses. To correct his ametropia, a -0.25-diopter minus lens cap was applied in front of the objective lens of the telescope, capitalizing on the property of vergence amplification. In addition, the tube length was adjusted. Adding lenses in front of the telescope and focusing the telescope can both affect the angular magnification of the system. Depending on the lenses used, type of telescope, and refractive error, there can be an increase or decrease in angular magnification. In this case, the minus lens at the front of the telescope decreased the power of the objective lens, and the focusing for the remaining uncorrected myopia increased the power of the ocular lens. Both of these factors contributed to increased resultant angular magnification for this patient. The patient achieved 10/30 (20/60) vision and reported success with his distance vision. CONCLUSIONS: Minus-powered lens caps over the objective lens are a viable option for highly myopic individuals who wish to use premanufactured spectacle-mounted telescopes.
