Intra-observer repeatability of optical quality measures provided by a double-pass system.
ABSTRACT The aim was to evaluate the intra-observer repeatability of the ocular optical quality measurements provided by a double-pass system in healthy eyes.
A total of 24 healthy eyes of 24 patients with ages ranging from 20 to 60 years were included in the study. Three consecutive measurements were obtained by an experienced examiner with the Optical Quality Assessment System (Visiometrics) of the following parameters defined by the manufacturer as follows: cut-off spatial frequency for the modulation transfer function (COMTF), Strehl ratio, width of the point spread function (PSF) at 10 per cent of its maximal height (PSF10) and width of the PSF at 50 per cent of its maximal height (PSF50). Intra-observer repeatability for 3.0 mm pupil measurements was evaluated by the within-subject standard deviation (S(w) ) and intra-class correlation coefficient (ICC).
The S(w) values for the different parameters evaluated were 4.34 cycles per degree for COMTF, 0.03 for the Strehl ratio, 1.14 arcmin for PSF10 and 0.36 arcmin for PSF50. The ICC values for these parameters were 0.746, 0.627, 0.783 and 0.814 for COMTF, Strehl ratio, PSF10 and PSF50, respectively. Statistically significant correlations were found between COMTF and the S(w) for PSF50 (r = -0.45, p = 0.03), and between the S(w) and the mean value for PSF50 (r = 0.42, p = 0.04). The significance of these correlations would vanish when considering the Bonferroni correction.
Measurements provided by the Optical Quality Assessment System should be considered and interpreted with caution because their consistency seems to be limited, especially in eyes with poor optical quality. The limitation in the validity of measurements due to the use of infrared light instead of middle-wavelength light should also be considered.
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ABSTRACT: Measurements obtained from the right and left eye of a subject are often correlated whereas many statistical tests assume observations in a sample are independent. Hence, data collected from both eyes cannot be combined without taking this correlation into account. Current practice is reviewed with reference to articles published in three optometry journals, viz., Ophthalmic and Physiological Optics (OPO), Optometry and Vision Science (OVS), Clinical and Experimental Optometry (CEO) during the period 2009-2012. Of the 230 articles reviewed, 148/230 (64%) obtained data from one eye and 82/230 (36%) from both eyes. Of the 148 one-eye articles, the right eye, left eye, a randomly selected eye, the better eye, the worse or diseased eye, or the dominant eye were all used as selection criteria. Of the 82 two-eye articles, the analysis utilized data from: (1) one eye only rejecting data from the adjacent eye, (2) both eyes separately, (3) both eyes taking into account the correlation between eyes, or (4) both eyes using one eye as a treated or diseased eye, the other acting as a control. In a proportion of studies, data were combined from both eyes without correction. It is suggested that: (1) investigators should consider whether it is advantageous to collect data from both eyes, (2) if one eye is studied and both are eligible, then it should be chosen at random, and (3) two-eye data can be analysed incorporating eyes as a 'within subjects' factor.Ophthalmic and Physiological Optics 01/2013; 33(1):7-14. · 1.74 Impact Factor
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ABSTRACT: To compare the optical quality measurements obtained from the double-pass system and ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes. Three months after cataract surgery, modulation transfer function (MTF) cutoff frequency, Strehl ratio, objective scatter index, and objective pseudoaccommodation obtained from the double-pass system were compared with total aberration, higher-order aberration, and spherical aberration obtained from ray-tracing aberrometer. In addition, parameters of the double-pass system were compared with subjective visual acuity and the contrast sensitivity score. Forty eyes of 40 patients were included. The MTF cutoff frequency and Strehl ratio were negatively correlated with total aberration (r = -0.503, p = 0.003; r = -0.509, p = 0.003, respectively) and subjective visual acuity (r = -0.453, p = 0.007; r = -0.354, p = 0.040, respectively). The objective scatter index was positively correlated with total aberration (r = 0.451, p = 0.024) and subjective visual acuity (r = 0.516, p = 0.008). The MTF cutoff frequency showed a correlation with contrast sensitivity score under photopic and mesopic conditions. Optical quality parameters obtained from the double-pass system were correlated with ocular aberrations, subjective visual acuity, and contrast sensitivity score in pseudophakic eyes.Optometry and vision science: official publication of the American Academy of Optometry 01/2014; · 1.53 Impact Factor
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ABSTRACT: A number of clinical techniques are available to assess the visual and optical performance of the eye. This report aims to review the advantages and limitations of techniques used in previous studies of patients implanted with intraocular lenses (IOLs), whose designs are ever increasing in optical complexity. Although useful, in-vitro measurements of IOL optical quality cannot account for the wide range of biological variation in ocular anatomy and corneal optics, which will impact on the visual outcome achieved. This further highlights the need for a standardised series of visual performance tests that can be applied to a wide range of IOL designs. The conclusions of this report intend to assist researchers in developing a comprehensive series of investigations to evaluate IOL performance. Repeatable and reproducible in-vivo assessments of visual and optical performance are desirable to further develop IOL concepts and designs, in the hope of improving current post-operative visual satisfaction.Cataracts and Cataract Surgery: Types, Risk Factors, and Treatment Options, Edited by Didier Navarro, 06/2013: chapter Clinical Techniques to Assess the Visual and Optical Performance of Intraocular Lenses: A Review: pages 1-57; Nova Science Publishers, Inc..