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Published in Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza, Computer-Aided Glaucoma Diagnosis System, 2020
Arwa Ahmed Gasm Elseid, Alnazier Osman Mohammed Hamza
Siddeeqa et al. (2015) proposed a method to compare retinal nerve fiber layer (RNFL) thickness in black and Indian myopic students at the University of KwaZulu-Natal. A total of 80 (40 black and 40 Indian) participants of both genders, aged between 19 and 24 years (mean and standard deviation: 21 ± 1.7 years) were included in the study. Refractive errors were assessed with the Nidek AR-310A auto-refractor and via subjective refraction. RNFL thicknesses were then measured using the iVue-100 optical coherence tomography device.
The Theory Behind the Resistance Tests (It’s Not Just a Test)
Published in John William Yee, The Neurological Treatment for Nearsightedness and Related Vision Problems, 2019
If you treat it with the Modified Preliminary Drill, the retention period is much longer. An autorefractor reading would indicate that it reduces the sphere even though you are treating the astigmatism. Instead of testing for the resistance level of the astigmatism, just treat the compound anisometropic eye with the Modified Preliminary Drill. The patient would eventually have to perform the Modified Preliminary Drill anyway regardless if astigmatism or anisometropia is predominant.
Multifocal contact lens myopia control: central and peripheral retinal image quality
Published in Clinical and Experimental Optometry, 2023
There is a paucity of data on the actual change in the peripheral retinal image when patients have such plus-power rings added to their regular refractive correction. Empirical data on patients, using autorefractor measurements, report multifocal contact lenses to generate about a dioptre additional peripheral defocus, often accompanied by astigmatism.3,8 The meaning of such measurements, however, is not as transparent as it appears. An autorefractor with its specific measuring procedure, running through the gamut of settings marked in dioptres, registers an optimum value which is then regarded as the best lens power for imaging an object at infinity on the retina. The question here, however, is not the hypothetical lens power for sharpest retinal image, but the quite different one of the actual light spread on the retina when the patient wears a contact lens correction with and without multifocal zones and views target in a range of object distances. Focus mismatch in dioptres does not uniquely translate into image properties.
Impact of Lens Material on Objective Refraction in Eyes with Trifocal Diffractive Intraocular Lenses
Published in Current Eye Research, 2022
Nuria Garzón, Francisco Poyales, María García-Montero, Fidel Vega, María Sagrario Millán, César Albarrán-Diego
The second method to measure ObjRx was with the Nidek OPD-Scan III (Nidek Technologies, Gamagori, Japan). The measurement was performed three times before calculating the mean value. This aberrometer/corneal topographer workstation combines a wavefront aberrometer, an autorefractor, and a pupilometer. The autorefractor relies on the principle of scanning-slit retinoscopy, where the retina is scanned with an infrared slit beam. The device calculates the patient’s refraction (spherical and cylindrical refractive errors, as well as cylinder axis’ angle) based on the wavefront-phase differences.14 As well as providing objective refraction in the form of a spherocylindrical reading, the aberrometer also computes the Zernike coefficients for low- and high-order aberrations. The Zernike coefficients corresponding to low-order aberrations (Z02, Z2+2 and Z2−2) can be used to calculate ObjRx in vector notation (M, J0 and J45) according to the expressions described by Micó et al.15 and Garzon et al.8
Validation of an Objective Method for the Qualitative and Quantitative Assessment of Binocular Accommodative Facility
Published in Current Eye Research, 2020
Jesús Vera, Beatríz Redondo, Rubén Molina, George-Alex Koulieris, Raimundo Jiménez
The objective measurements of accommodation were obtained using the WAM-5500 in dynamic hi-speed mode, which continuously recorded the refractive error while the participants fixed alternatively the Hart charts at distance (5 m) and near (40 cm) over a 60-sec period. The accommodative response measurements with the autorefractor were started in synchrony with participants initiating the BAF test. The start button on the autorefractor produced a “beep” which indicated the commencement of the test to the participants. This procedure was very similar to the one used by Allen et al.,34 aimed to reduce the variability between the moment of objective recording and when the participants started. Although subjects viewed both targets binocularly, AR measures were only obtained from the sighting dominant eye (determined by the hole-in-card method) at the time (right eye dominance was observed in 22 out of 33 participants).35 During the dynamic measurements, the examiner ensured that the instrument remained carefully aligned. Room illumination conditions were maintained at ~150 lux (Illuminance meter T-10, Konica Minolta, Inc., Tokyo, Japan) during the entire experimental session.