Quantitative photorefraction using an off-center flash source.

School of Optometry, University of Waterloo, Ontario, Canada.
American journal of optometry and physiological optics 01/1989; 65(12):962-71. DOI: 10.1097/00006324-198812000-00008
Source: PubMed

ABSTRACT When an eye is refracted by "eccentric photorefraction" with a flash source off-centered from a camera lens, a crescent of light is formed in the margin of the pupil. The size of the crescent varies directly with the eye's refractive error. This photographic method has been used in vision screening studies of young children where the appearance of a crescent indicated that the refractive error was above a certain threshold. Usually quantification of the refraction could not be achieved by the photorefractor but relied upon subsequent testing using retinoscopy. My research aimed to expand eccentric photorefraction so as to enable it to provide quantification of the eye's refractive error. This was achieved by varying the eccentricity of the flash source from the camera lens and then calibrating the instrument over a large range of refractive errors. The calibration modified a previously derived optical relation which defined the eye's refractive error in terms of the eccentricity of the source for a given pupil size. Eccentric photorefraction of 26 infants and children aged 7 to 48 months showed a good correlation with retinoscopy (r = 0.82). It is concluded that this method would be complementary to other photorefractive methods (e.g., isotropic) particularly as it is able to measure a large range of refractive errors once the astigmatic meridians of the eye are known.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper calculates the medical expenditures for pediatric Medicaid enrollees with fetal alcohol syndrome (FAS), those with and those without reported intellectual disability (ID). The pediatric portion of the MarketScan® Medicaid Multi-State databases for the years 2003-2005 was used. Children with FAS were identified based on International Classification of Diseases, Ninth Revision, Clinical Modification codes. Children without FAS formed the comparison group. Annual mean, median, and 95(th) percentile total expenditures were calculated for those continuously enrolled during 2005. Children with FAS incurred annual mean medical expenditures that were nine times as high as those of children without FAS during 2005 ($16,782 vs. $1,859). ID more commonly was listed as a medical diagnosis among children with FAS than among children in the comparison group (12% vs. 0.5%), and mean expenditures of children with FAS and ID were 2.8 times those of children with FAS but without reported ID. Children with FAS incurred higher medical expenditures compared with children without FAS. A subset of children with FAS who had ID sufficiently serious to be recorded in medical records increased those expenditures still further. Our estimate of mean expenditures for children with FAS was several times higher than previous estimates in the United States.
    Neurotoxicology and Teratology 11/2010; 33(2):322-4. · 3.18 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Diabetes demands early diagnosis, prompt treatment, continuous monitoring and follow up. Physicians play a pivotal role in diabetes management. However, evidence suggests that sub-optimal knowledge of guidelines and other issues may lead to ineffective management and poor patient outcomes. The aim of this research was to identify clinical diabetologist's perspectives on evidence based diabetes management, benefits of and barriers to the practice of evidence based guidelines in management of type 2 diabetes. Clinical diabetologists were administered a semi-structured questionnaire. Qualitative responses were analysed to identify key words, phrases and concepts from respondents. Majority of diabetologist (78.2%) preferred ADA guidelines alone or in combination with others guidelines where as 12.7% diabetologist follow all the guidelines on case by case basis. 27% and 25% diabetologists opined that guidelines ensure uniform standard of care across patient and achievement of diabetes management goals respectively. Poor awareness among physicians (22.7%), western guidelines being not applicable to Indian patients (22.7%), cost to patient (18.2%) were some of the barrier to practice of evidence based diabetes management. Some of the mechanism suggested to improve the practice of evidence based diabetes management included education of physicians in EBM (28.9%), making practice of evidence based guidelines legally binding (10.5%) and wider dissemination of existing guidelines (7.8%).
    Diabetes research and clinical practice 02/2012; 95(2):189-93. · 2.74 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The accuracy and precision of retinoscopy need to be evaluated in an objective and unambiguous manner to judge an individual's performance in this task during training or in research for consistent measurements of refractive error. This study describes and evaluates a psychophysical technique for obtaining simultaneous and unbiased estimates of accuracy and precision in retinoscopy. Subjects with zero to 12 years of experience with retinoscopy performed the psychophysical task on a model eye (75 subjects) and on a cyclopleged human eye with spherical refractive error (30 subjects). Subjects made forced choice judgments of 'with' or 'against' for lens powers within ±0.5 D of expected neutrality (in 0.12 D steps), each placed 20 times before the eye in random order. Accuracy and precision were determined from the mean and standard deviation of the resultant psychometric function. Subjects could be qualitatively divided into those with good and poor accuracy and precision based on the task outcomes. The median and inter-quartile range of accuracy (no experience: 0.16 ± 0.34 D; four or more years of experience: 0.06 ± 0.11 D) and precision (no experience: 0.30 ± 0.39 D; four or more years of experience group: 0.13 ± 0.08 D) improved with task experience (p < 0.001). Median accuracy and precision in the human eye were similar to the model eye (p > 0.8). Accuracy and precision were poorly correlated with each other for both the human eye and model eye (|ρ| ≤ 0.20; p ≥ 0.09 for all). The psychophysical retinoscopic task could differentiate subjects based on their accuracy and precision and also capture key elements of improvement in retinoscopic performance with experience. Retinoscopic performance using this task was similar to previous reports using routine clinical retinoscopy. Therefore, the psychophysical technique may be used to evaluate and monitor objectively retinoscopic performance.
    Clinical and Experimental Optometry 10/2013; · 0.92 Impact Factor