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Measurement of refractive error and accommodation with the photorefractor PowerRef II
Author(s) -
Jainta Stephanie,
Jaschinski Wolfgang,
Hoormann Jörg
Publication year - 2004
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/j.1475-1313.2004.00233.x
Subject(s) - accommodation , refractive error , optometry , optics , medicine , physics , visual acuity
The infrared photorefractor PowerRef II (PR II; PlusoptiX AG, Nürnberg, Germany) uses the principle of eccentric photorefraction. In eight subjects the mean non‐cycloplegic refraction measured with the ‘Full Scan’ mode of the PR II at a far viewing distance (0.2 D) was significantly more hypermetropic by 0.6 D compared with subjective refraction. The mean accommodation differed by about this same amount between the PR II and the Canon R1 at three different viewing distances (3, 2 and 1 D). The PR II refraction at the 1 m reference distance was 0.25 D more hypermetropic compared with the subjective refraction at far (5 m); these measures were moderately correlated ( r = 0.7). To determine temporal changes, the ‘Dynamic Scan’ mode was used over a 2‐min period: the mean intraindividual standard deviation was 0.32 mm for pupil diameter and 0.29 D for accommodation, while the absolute measurement error of the ‘Dynamic Scan’ was found to be <0.12 D for the accommodation data. Interindividual reliabilities were satisfactory. However, the PR II did not provide a continuous stream of data and the specified sampling frequency of 25 Hz was rarely realized.