Premium
Clinical evaluation of the Grand Seiko Auto Ref/Keratometer WAM‐5500
Author(s) -
Sheppard Amy L.,
Davies Leon N.
Publication year - 2010
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.1475-1313.2009.00701.x
Subject(s) - keratometer , repeatability , refractive error , medicine , ophthalmology , astigmatism , subjective refraction , optometry , refraction , limits of agreement , orthodontics , mathematics , eye disease , optics , cornea , nuclear medicine , physics , statistics
Purpose: A clinical evaluation of the Grand Seiko Auto Ref/Keratometer WAM‐5500 (Japan) was performed to evaluate validity and repeatability compared with non‐cycloplegic subjective refraction and Javal–Schiotz keratometry. An investigation into the dynamic recording capabilities of the instrument was also conducted. Methods: Refractive error measurements were obtained from 150 eyes of 75 subjects (aged 25.12 ± 9.03 years), subjectively by a masked optometrist, and objectively with the WAM‐5500 at a second session. Keratometry measurements from the WAM‐5500 were compared to Javal–Schiotz readings. Intratest variability was examined on all subjects, whilst intertest variability was assessed on a subgroup of 44 eyes 7–14 days after the initial objective measures. The accuracy of the dynamic recording mode of the instrument and its tolerance to longitudinal movement was evaluated using a model eye. An additional evaluation of the dynamic mode was performed using a human eye in relaxed and accommodated states. Results: Refractive error determined by the WAM‐5500 was found to be very similar ( p = 0.77) to subjective refraction (difference, −0.01 ± 0.38 D). The instrument was accurate and reliable over a wide range of refractive errors (−6.38 to +4.88 D). WAM‐5500 keratometry values were steeper by approximately 0.05 mm in both the vertical and horizontal meridians. High intertest repeatability was demonstrated for all parameters measured: for sphere, cylinder power and MSE, over 90% of retest values fell within ±0.50 D of initial testing. In dynamic (high‐speed) mode, the root‐mean‐square of the fluctuations was 0.005 ± 0.0005 D and a high level of recording accuracy was maintained when the measurement ring was significantly blurred by longitudinal movement of the instrument head. Conclusion: The WAM‐5500 Auto Ref/Keratometer represents a reliable and valid objective refraction tool for general optometric practice, with important additional features allowing pupil size determination and easy conversion into high‐speed mode, increasing its usefulness post‐surgically following accommodating intra‐ocular lens implantation, and as a research tool in the study of accommodation.