RESUMO
A previous work has reported a methodology to quantify intraocular scattering using a high sensitivity double-pass instrument with a robust index, the frequency scatter index. The purpose of our study was to evaluate an adaptation of the frequency scatter index for use in clinical double-pass systems. A prospective observational study was carried out in a group of patients with nuclear cataracts (n = 52) and in a control group (n = 11) using conventional double-pass systems. The frequency scatter index and the objective scatter index were used to assess the scattering. The Spearman coefficient was calculated to assess the correlation between both indexes, obtained from the double-pass images. Simultaneous measurements were performed with a double-pass and with a Hartmann-Shack wavefront sensor in the control group. The root-mean-square wavefront error and the full width at half maximum of the double-pass image were used to quantify the residual aberrations introduced by the variations in pupil size and retinal eccentricity. Measurement in eyes with different grades of cataracts shows a strong correlation (ρ = 0.929, p < .0001) between the frequency scatter index and the objective scatter index. A certain degree of correlation was observed between the objective scatter index and the root-mean-square and between the objective scatter index and the full width at half maximum, both for measurements with a different pupillary diameter and with a different retinal eccentricity (p < .05). No relationship was observed between the frequency scatter index and the root-mean-square or between the frequency scatter index and the full width at half maximum (p > .05). We have introduced and evaluated an adaptation of a methodology proposed recently for the measurement of intraocular scattering using the double-pass technique with a robust index, which is less affected by ocular aberrations. The frequency scatter index can be applied to conventional double-pass instruments available in clinical environments.
Assuntos
Catarata , Luz , Catarata/diagnóstico , Humanos , Retina , Espalhamento de Radiação , Visão OcularRESUMO
PURPOSE: The aim of this article is to propose a quantitative methodology for determining a criterion to discriminate the nonsurgical nuclear cataract from the surgical one taking into account objective measures of intraocular scattering in patients with good visual acuity (>0.6). METHODS: Two groups of subjects were taken into account: a control group and a group with nuclear cataracts. At a first stage, eyes belonging to the cataract group were classified into "nonsurgical" and "surgical" cataracts by ophthalmologists at their clinical settings. At a second stage a double-pass instrument was also used to determine the objective scatter index (OSI) at the laboratory. Receiver operating characteristic (ROC) curves were used to analyze OSI values to determine a value able to separate between nonsurgical and surgical cataracts. RESULTS: We obtained statistically significant differences among the control and both nuclear cataract groups (p < 0.05). ROC curves determined an OSI criterion level (of 2.1) to suggest surgery in nuclear cataracts with an area under curve of 0.83, i.e. with 80% of sensitivity and 80% of specificity. CONCLUSIONS: ROC analysis allows separating both groups of nuclear cataract, and we determined a value of OSI in nuclear cataract quantification for surgery.
Assuntos
Extração de Catarata , Catarata/diagnóstico , Núcleo do Cristalino/patologia , Curva ROC , Espalhamento de Radiação , Adulto , Idoso , Idoso de 80 Anos ou mais , Catarata/classificação , Humanos , Núcleo do Cristalino/efeitos da radiação , Luz , Pessoa de Meia-Idade , Acuidade Visual , Adulto JovemRESUMO
In this study we present the comparison of the performance of two systems to measure intraocular scattering. Measurements were made by using a psychophysical system based on a brightness comparison method that provides a glare index and a physical system based on the double-pass technique, which gives an objective scatter index by measuring the optical quality of the eye. Three external diffuser filters that simulated different grades of intraocular scattering were used in subjects with normal vision. The two measured indexes showed a graded rise with increasing level of scattering. The discrimination ability obtained for both systems showed that they were able to distinguish among conditions ranging from normal to early cataracts.
Assuntos
Olho , Luz , Fenômenos Fisiológicos Oculares , Psicofísica/métodos , Espalhamento de Radiação , Adulto , Catarata/diagnóstico , Catarata/fisiopatologia , Difusão , Olho/fisiopatologia , Humanos , Visão Ocular/fisiologiaRESUMO
PURPOSE: To use the double-pass technique to evaluate the in vitro optical quality of foldable monofocal intraocular lenses (IOLs) used to correct aphakia. SETTING: Universitat Politècnica de Catalunya, Terrassa, and Instituto de Microcirugía Ocular de Barcelona, Barcelona, Spain; Universidad Nacional de Tucumán, Tucumán, Argentina. METHODS: This study assessed the in vitro optical quality of 7 IOLs before and after injection in an artificial eye that was attached to a double-pass system (Optical Quality Analysis System [OQAS]). The procedure imitated the conventional in vivo technique used to assess the optical quality of eyes with an IOL. The following parameters were evaluated: point-spread function, modulation transfer function (MTF), MTF cutoff frequency, Strehl ratio, and OQAS values. RESULTS: The in vitro optical quality of most IOLs was as good after injection as before injection. In 1 IOL, the post-injection optical quality was statistically significantly different but the optical quality remained high. CONCLUSIONS: Results indicate that after an IOL is placed in the eye, its optical performance will be good, providing good visual quality. The eye cell model attached to the double-pass system was useful and effective for fully characterizing the optical quality of IOLs and evaluating variations resulting from the injection process.