Variance Analysis Of Contrast Sensitivity For Amblyopia And Normal Eye Based On Spatial Frequency Channels

Contrast sensitivity evaluates the distinguish ability of human eye in differentspatial luminance contrast level, reflecting the ability to discern the complexity spatialstructure of visual world. Contrast sensitivity is tuned by spatial frequency channels,whose tuning curves’ envelope constitutes contrast sensitivity function. Contrastsensitivity, as one of the means of amblyopia diagnosis and treatment evaluation, hasbeen widely applied in clinical and research. Studying the difference of contrastsensitivity between amblyopic eye and normal’s has great significance forunderstanding the pathological mechanisms, diagnosis and treatment of amblyopia.In this paper, contrast sensitivity of174normal children’s eyes and148amblyopic children’s abnormal eyes were measured, the difference of contrastsensitivity between amblyopic eyes and normal’s was analyzed by “contrastsensitivity-spatial frequency channels” model, the number and the bandwidths ofspatial frequency channels were calculated. To ensure the validity of the deducedspatial frequency channels and bandwidths, another independent48cases of contrastsensitivity of amblyopic children’s abnormal eyes were used for cross-validation.Contrast sensitivity deficits in amblyopia were investigated through comparing thedifference in contrast sensitivity between amblyopic eyes and normal’s from the pointof view of spatial frequency channels.We mainly worked in the following areas: 1. The importance of contrast sensitivity study was described first, and then theresearch achievements and status at home and abroad in amblyopia field werereviewed, the specific research objectives and research contents were put forwardfinally.2. According to the psychological theory of physics, contrast sensitivitymeasurement experiment was designed by adopting OPTEC6500visual functiontester.3.174cases of normal children’s eyes and148cases of amblyopic children’sabnormal eyes were examined in the Ophthalmology Center of the Second AffiliatedHospital, Zhejiang University Medical School, each subject’s visual functionexamination result was recorded for statistics.4. Mathematical statistical analysis was conducted on the contrast sensitivity of174normal eyes and100amblyopic eyes. Based on “contrast sensitivity-spatialfrequency channels” model, channel tuning curves of normal and amblyopic subjectswere derived via PCA and Promax, bandwidths of channels were calculated by usingthe method of full width at half maximum (FWHM). These channel tuning curveswere reproduced in a cross-validation study of another independent48cases ofcontrast sensitivity of amblyopic children’s abnormal eyes. The contrast sensitivitydeficits of amblyopic eye were investigated through comparing the differences incontrast sensitivity between amblyopic eye and normal’s from the point of view ofspatial frequency channels.The results showed that there existed three spatial frequency channels both innormal and amblyopic eye when spatial frequency covered1.5~18.0c/deg, at thepeaks of3.0,6.0,12.0c/deg，the bandwidths of normal eye were1.04,1.03,0.98octaves, the bandwidths of amblyopic eye were:1.04,1.02,0.75octaves. Thebandwidths in medium and high spatial frequency of amblyopic eye were narrowerthan normal eye’s. All these results indicated that the reduction in bandwidths of thecorresponding spatial frequency channels may cause contrast sensitivity deficits inamblyopia.