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Mario Angi, Oren M Feuerman, Andrea Leonardi; Higher eccentricity of the LED source in photorefraction extends the range of measurement to high ametropias. Invest. Ophthalmol. Vis. Sci. 2014;55(13):435.
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© ARVO (1962-2015); The Authors (2016-present)
Eccentric photorefraction is the most utilized method to screen for refractive errors in young children. However, the currently available instruments have a limited range of measurement (±5 diopters). We investigated whether a higher eccentricity of the LED source in a photorefractometer is able to measure high ametropias (HA) defined as spherical equivalent greater than ±5 D.
The refractive status of consecutive patients accessing a private office for ophthalmic examination was assessed without cycloplegia with a standard autorefractometer (Canon R50) and with a novel videorefractometer (2WIN, Adaptica, Padova, Italy) equipped with both the standard eccentricity LEDs and a customized high eccentricity (5.5 cm) LED. To enrich the study group, soft contact lenses were also used in 10 emmetropic eyes to create HA. Measurements from the customized instrument were obtained by manually calculating the slopes of the light crescent using the software ImageJ. A ROC curve analysiso of 4 cut off intervals (±5, ±7, ±10,±15 D) was performed to assess the diagnostic accuracy of standard and customized 2WIN, taking the autorefractometer readings as gold standard.
Measurements were obtained from 89 eyes, with a mean spherical equivalent error of -3.8D ± 7.0D (range: -22 to +13D). Among these, 36 HA data sets were obtained: 26 spontaneously occurring in patients, and 10 generated with contact lenses. A comparison of AUC values between the standard and customized 2WIN measurements revealed a statistically significant grater diagnostic accuracy of the customized LED for cut-off intervals greater than ±5 D. Outlier analysis of critical slopes values confirm the results from the ROC curve analyses.
The 2WIN videorefractometer with customized high eccentricity LED can efficiently measure high ametropias, thus increasing the diagnostic usefulness of the photorefraction method.
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