E Tanaka, Y Nishiwaki, K Oda, A Hirakata, T Hida, T Fujiwara
Kyorin Eye Center, Ophthalmology, Mitaka, Japan
Purpose: The spectacle lenses with powers more than 4Diopter (D), so-called high power spectacles, have been prescribed as reading aids for persons with low vision. We investigate into how far we can expect from this genre of reading aid.
Method: We retrospectively looked into the records of 62 acquired low vision patients (aged 55.5±18.9) in Kyorin Eye Center to whom we had tried prescription of spectacles for reading. We examined the lens power (additional power to 5m correction) considered appropriate at the examination , the lens power actually prescribed after trials at home, subjective impressions for lenses they tried, visual acuity, reading performance, and refractive error.
Result and Discussion: Spectacles were prescribed to 41 out of 62 patients. The ratio of patients who were prescribed lenses of 3 to 4D was 43%, 31% for 4 to 6D, 5% for 6 to 8D, 7% for 8 to 10D, and only 2% for over 10D. Significant difference was observed between appropriate lens powers (6.34±4.8D, max 30D) and prescribed powers (4.1±1.7D, max 10D). Almost half of prescribed patients did not accept appropriate power for their reading, in another words, they should have needed additional magnification. When comparing patients who comfortably used high power (>=6D) with those who could not, more hyperope tended to be found in those who could not use it. None of the other factors were significant.
Conclusion: Focusing distance of spectacle lenses that large proportion of low vision patients could wear comfortably was no closer than 15cm, ie, 6D.
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