Clinical evaluation of an automated subjective refraction method implemented in a computer-controlled motorized phoropter.

PURPOSE: To investigate a new algorithm to perform an automated non-cycloplegic refraction in adults. METHODS: Fifty healthy subjects were measured twice (test-retest) with the new automated subjective refraction method and with the conventional clinician subjective refraction procedure. Objective refraction was also measured with the Grand Seiko WAM-5500 autorefractor. The new automated method was inspired on the root finding bisection algorithm and on the Euclidean distances in the power vector domain. The algorithm was implemented in a computer that was synchronized with a customized motorized phoropter. Repeatability was mainly assessed with the within-subject standard deviation (Sw) and accuracy was mainly assessed with the limits of agreement. RESULTS: The within-subject standard deviations of the power vector components (M, J0, J45) obtained for the right eye are (±0.13, ±0.04, ±0.05)D and (±0.17, ±0.03, ±0.07)D, respectively, for the clinical and the automated subjective refraction methods. The limits of agreement (with the clinical method) for the automated and the objective methods are, respectively (±0.56, ±0.18, ±0.31)D and (±0.77, ±0.15, ±0.18)D. Similar results are obtained for the left eye. CONCLUSIONS: The proposed automated method is repeatable and more accurate than objective techniques in healthy adults. However, it is not accurate enough to replace the clinical subjective refraction yet and it should be tested in a wider population in terms of age, refraction and different ocular conditions. Despite these important limitations, this method has been shown to be a potentially valuable method to improve the access to primary eye care services in developing countries.

Spherical subjective refraction with a novel 3D virtual reality based system.

PURPOSE: To conduct a clinical validation of a virtual reality-based experimental system that is able to assess the spherical subjective refraction simplifying the methodology of ocular refraction. METHODS: For the agreement assessment, spherical refraction measurements were obtained from 104 eyes of 52 subjects using three different methods: subjectively with the experimental prototype (Subj.E) and the classical subjective refraction (Subj.C); and objectively with the WAM-5500 autorefractor (WAM). To evaluate precision (intra- and inter-observer variability) of each refractive tool independently, 26 eyes were measured in four occasions. RESULTS: With regard to agreement, the mean difference (±SD) for the spherical equivalent (M) between the new experimental subjective method (Subj.E) and the classical subjective refraction (Subj.C) was -0.034D (±0.454D). The corresponding 95% Limits of Agreement (LoA) were (-0.856D, 0.924D). In relation to precision, intra-observer mean difference for the M component was 0.034±0.195D for the Subj.C, 0.015±0.177D for the WAM and 0.072±0.197D for the Subj.E. Inter-observer variability showed worse precision values, although still clinically valid (below 0.25D) in all instruments. CONCLUSIONS: The spherical equivalent obtained with the new experimental system was precise and in good agreement with the classical subjective routine. The algorithm implemented in this new system and its optical configuration has been shown to be a first valid step for spherical error correction in a semiautomated way.

Concordancia entre dos técnicas subjetivas para determinar la refracción en adultos jóvenes / Concordance between two subjective techniques used to determine refraction in young adults

La refracción subjetiva es una técnica que compara un lente con otro para llegar a una combinación de lentes que resulte en el máximo de agudeza visual. Estudios han evaluado la concordancia intra/inter observadora y con otras técnicas objetivas o subjetivas, principalmente para el cilindro cruzado de Jackson (JCC), pero pocas para el emborronamiento más dial astigmático (EmD). Objetivo: determinar la reproducibilidad de los métodos subjetivos EmD y JCC y la concordancia de estos con el procedimiento objetivo de retinoscopia estática. Método: se realizó un estudio descriptivo de concordancia con 190 sujetos, con medición independiente para cada técnica por dos evaluadores. En el análisis estadístico de las refracciones se usó transformación en notación Fourier. Resultados: EmD tuvo una mejor reproducibilidad para el poder esférico y cilíndrico, pero para el eje fue mejor con el método del JCC. Entre el método objetivo y los subjetivos la concordancia fue más baja en el equivalente esférico (componente M) para el JCC; se aprecia que el sesgo (exactitud) y la precisión son pobres, señalando que las mediciones hechas principalmente en el componente esférico difieren en promedio y en repetición entre estas técnicas. Conclusión: las discrepancias entre evaluadores o procedimientos en el cilindro pueden ser hasta de ±0,50 D y 10° en el eje, pero en la esfera puede ser hasta de 1,00 D; ambas técnicas son válidas para la evaluación de la refracción subjetiva en sujetos jóvenes.

Subjective refraction is a technique whereby one lens is compared to another in order to find a lens combination that results in maximum visual acuity. Studies have evaluated intraobserver or interobserver concordance, along with other objective or subjective techniques, mostly for theJackson Cross Cylinder (JCC), but few for fogging and use of astigmatic dials (EmD, for its initialsin Spanish). Objective: To determine the reproducibility of subjective methods EmD and JCC, as well as their concordance with the objective procedure of static retinoscopy. Methodology: A descriptive concordance study was carried out among 190 individuals, with independent measurementfor each technique by two evaluators. Fourier transformation was used on statistical analysis of refractions. Results: EmD showed a higher reproducibility for the spherical and cylindrical power,but the JCC methodology was better for the axis. Between the objective and subjective methodologies,concordance level was lower in the spherical equivalent (component M), and for the JCC we can see that accuracy and precision are poor, pointing out that measurements made mostly in the spherical component are different on average and in technique repetition. Conclusions: Discrepancies between evaluators or procedures in the cylinder may be of up to ±0.50 D and 10°at the axis, but it can go up to 1.00 D in the sphere; both techniques are valid for the evaluationof subjective refraction in young individuals.