Each participant underwent a standardized examination. Refraction and corneal curvature were measured using an auto-keratorefractor (Canon RK 5 Auto Ref-Keratometer, Canon Inc. Ltd., Tochigiken, Japan). SE was calculated as the sum of the spherical power and half of the cylinder power. Best-corrected visual acuity was measured monocularly using a LogMAR chart (Lighthouse International, New York, USA) at a distance of 4 meters. Ocular biometry, including axial length (AL), was measured using non-contact partial coherence interferometry (IOL Master V3.01, Carl Zeiss Meditec AG, Jena, Germany). Intraocular pressure (IOP) was measured using Goldmann applanation tonometry (Haag-Streit, Bern, Switzerland) before pupil dilation. Standardized visual field testing was performed with static automated white-on-white threshold perimetry (SITA Fast 24-2, Humphrey Field Analyzer II; Carl Zeiss Meditec, Inc., Oberkochen, Germany). Slit-lamp biomicroscopy (Haag-Streit model BQ-900; Haag-Streit, Switzerland) was performed by the study ophthalmologists to examine the anterior chamber and lens after pupil dilation with tropicamide 1% and phenylephrine hydrochloride 2.5%.
Rk 5 auto ref keratometer
Manufactured by Canon
Sourced in Japan
The Canon RK 5 Auto Ref-Keratometer is a compact and automated device designed for precise refractive and keratometric measurements. It provides objective data on the eye's refractive power and corneal curvature, serving as a valuable tool for eye care professionals.
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Lab products found in correlation
5 protocols using rk 5 auto ref keratometer
1
Standardized Ophthalmic Examination Protocol
2
Objective and Subjective Refraction
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Objective refraction was measured using an autorefractor (Canon RK-5 Auto Ref- Keratometer, Canon Inc Ltd, Tokyo, Japan). Manual subjective refraction was then used to refine vision, using the results of the objective refraction as the starting point. In this study, refraction data were obtained from subjective refraction techniques. If subjective refraction was not available, autorefraction data were used instead. Spherical equivalent (SE) was defined as sphere plus half cylinder. Any myopia was defined as a SE of less than -0.5 diopter (D) while high myopia was defined as a SE of less than -6.0 D.
3
Visual Acuity and Refractive Error Assessment
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Presenting visual acuity was monocularly measured by using a logarithm of the minimum angle of resolution (logmar) number chart (Lighthouse International, New York, USA) at a distance of 4 m. Autorefraction, was performed with an autorefractor machine (Canon RK-5 Auto Ref-Keratometer, Canon Inc. Ltd., Japan). Final refraction was determined by subjective refraction by trained and certified study optometrists. Best-corrected visual acuity after subjective refraction was monocularly assessed and recorded in logMAR scores. VI was defined as best-corrected visual acuity worse than 20/40 in the better eye, based on the US definition (Congdon et al., 2004 (link)). Under-corrected refractive error was defined as an improvement of at least 0.2 logMAR (2 lines equivalent) in the best-corrected visual acuity compared with the presenting visual acuity in the better eye.
4
Comprehensive Ophthalmic Evaluation Protocol
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All subjects underwent a standardized ophthalmic examination. Best-corrected visual acuity was measured on a logMAR chart. Refractive error and corneal curvature were measured using an autorefractor (Canon RK 5 Auto Ref-Keratometer; Canon Inc., Ltd., Tochigiken, Japan). Central corneal thickness was measured with an ultrasound pachymeter (Advent; Mentor O & O Inc., Norwell, MA). Axial length was measured using non-contact partial coherence interferometry (IOL Master V3.01, Carl Zeiss Meditec AG, Jena, Germany). Intraocular pressure (IOP) was measured using the Corvis ST Tonometer (Oculus, Wetzlar, Germany). Subjects were also examined by an ophthalmologist under the slit lamp for anterior segment examination, gonioscopy, and optic disc examination through a dilated pupil with the 78-diopter (D) lens at x16 magnification with a measuring graticule. Optical imaging of the lamina cribrosa was performed as described below. Subjects with glaucoma underwent visual field (VF) assessment on standard automated perimetry (Swedish Interactive Threshold Algorithm Standard algorithm with a 24-2 test pattern, Humphrey Visual Field Analyser II; Carl Zeiss Meditec, Dublin, California, USA).
5
Cycloplegic Refractive Error Measurement
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Refractive error was measured using an auto refractometer (Canon RK-5 Auto Ref-Keratometer; Canon Inc., Ltd., Tokyo, Japan) under cycloplegic conditions. Five consecutive measurements were obtained for each eye of all students, and the mean of measurements was used for analysis. Cycloplegia was preceded with one drop of 0.5% proparacaine, and then two drops of 1% cyclopentolate within a 5-minute interval. If the pupil size was < 6 mm or reflective to light, an additional drop of cyclopentolate was administered every 5 minutes until an acceptable dilation occurred. Myopia was defined as spherical refractive error (SRE) < −0.50 D, hyperopia was defined as SRE > +1.0 D, and emmetropia as SRE −0.5–+1.0 D. This study used the better eye when determining SRE.
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