Contrast sensitivity (CS) can more comprehensively evaluate the characteristics of visual system form function, and it is a new quantitative method of form function. It plays an important role in the study of psychophysics and electrophysiology of the visual system, and its examination helps to recognize the abnormalities of some visual diseases, which is conducive to their diagnosis.

① Application of contrast sensitivity (CS) in ametropia

The contrast sensitivity (CS) of mild ametropia decreased at high spatial frequency. With the increase of ametropia, the contrast sensitivity (CS) of middle spatial frequency and low spatial frequency also decreased. The contrast sensitivity function (CSF) curve of high myopia decreased significantly in the high spatial frequency region even though the corrected visual acuity was good.

The measurement of contrast sensitivity is also helpful for the fitting of corneal contact lenses and the replacement of lenses. Compared with wearing hard contact lenses, residual astigmatism after wearing soft contact lenses can cause the contrast sensitivity function (CSF) curve to decrease in the high spatial frequency region; If there is too much sediment on the lens of the corneal contact lens or the lens surface is worn, the contrast sensitivity function (CSF) curve will decline. At this time, the visual quality will decline. It should prompt to replace the lens in time.

② Application of contrast sensitivity (CS) in cataract

Cataract refers to the opacity of lens caused by various reasons. The turbid crystal will cause light scattering, reduce the contrast of retina, and cause visual darkening. If a high contrast visual acuity chart is used to evaluate the visual acuity of cataract patients, the patient may have good visual acuity at this time, but the patient complains that he cannot see clearly.

The contrast sensitivity function (CSF) curve decreased in different stages of various types of cataract. In the early stage of cataract, the low spatial frequency and middle spatial frequency of contrast sensitivity function (CSF) curve will decrease if there is no obvious decrease in visual acuity. When cataract developed to maturity, visual acuity decreased significantly, and the low spatial frequency, middle spatial frequency and high spatial frequency of contrast sensitivity function (CSF) curve decreased.

③ Application of contrast sensitivity (CS) in macular diseases

In patients with age-related macular degeneration, the contrast sensitivity function (CSF) curve decreased, and the surface optic nerve system was damaged at high spatial frequency, medium spatial frequency and low spatial frequency. It has been reported that age-related macular degeneration with normal vision also has abnormal contrast sensitivity function (CSF) curve, and the contralateral eye of monocular macular degeneration may also have a decrease in contrast sensitivity (CS). Therefore, contrast sensitivity (CS) is an effective method to detect the visual function change of early age-related macular degeneration, and it is also a subclinical diagnostic method of the disease.

④ Application of contrast sensitivity (CS) in diabetes retinopathy

Diabetes retinopathy is one of the serious complications of diabetes. Even if the patient's visual acuity is 1.0 or above, the related visual loss caused by early vascular damage in patients with diabetes can be found by contrast sensitivity examination. Before the occurrence of fundus lesions in diabetes, there was a partial decrease in contrast sensitivity (CS). In the early stage of diabetes retinopathy, the contrast sensitivity (CS) of low spatial frequency and medium spatial frequency decreased only. When the macula was damaged, the contrast sensitivity (CS) of all spatial frequencies decreased.

⑤ Application of contrast sensitivity (CS) in ocular hypertension and glaucoma

High intraocular pressure represents the upper limit of the normal intraocular pressure distribution curve of the human eye. There should be no damage to the optic papilla and visual field. However, through the contrast sensitivity (CS) examination, it is found that even if the optic papilla and visual field of the patient are normal, the contrast sensitivity (CS) will change significantly, especially for the high spatial frequency area of the specific sensitivity function (CSF) curve, which is significantly lower than the normal.

In all types of glaucoma, even if the central visual acuity is normal, the contrast sensitivity function (CSF) curve also decreases significantly, especially in the high spatial frequency region. Therefore, the decrease of contrast sensitivity (CS) in glaucoma patients is earlier than the damage of optic papilla and visual field. It is more sensitive than visual acuity chart to reflect the course of glaucoma.

⑥ The application of contrast sensitivity (CS) in corneal refractive surgery

Corneal refractive surgery mainly uses excimer laser cutting to change the morphology of the anterior surface of the cornea, thus changing the diopter of the angle and correcting the original ametropia. Contrast sensitivity (CS) examination can effectively evaluate the postoperative visual quality. In the early postoperative period of excimer laser, because of corneal tissue reaction and edema, the contrast sensitivity (CS) decreased significantly, and the visual quality of patients was lower than normal. After a few weeks or months, the patient's visual quality and contrast sensitivity (CS) will return to normal. There are also some patients whose pupil enlarges at night or in dark environment. The enlarged pupil exceeds the cutting area. The visual quality will be greatly affected after the light passes through, resulting in the decrease of contrast sensitivity (CS) and glare. The decrease of contrast sensitivity is related to the preoperative myopia and the optical cutting area. The higher the preoperative degree, the smaller the optical cutting area, and the greater the difference between the central and peripheral corneal curvature after the operation, The more obvious the decrease of contrast sensitivity (CS). The contrast sensitivity (CS) examination can comprehensively, objectively and sensitively reflect the visual function status of patients, and timely and effective diagnosis can be made for the phenomenon that some patients have normal naked eye vision but complain of blurred vision.

⑦ The application of contrast sensitivity (CS) in amblyopia

All amblyopia patients have abnormal contrast sensitivity (CS), but the changes of CS are different in amblyopia caused by different reasons. Strabismus amblyopia only showed the decrease of contrast sensitivity (CS) at high spatial frequency, but the decrease of CS was not consistent with the decrease of visual acuity. The contrast sensitivity (CS) of anisometropic amblyopia patients decreased at all spatial frequencies, and the decrease was basically parallel to the decrease of visual acuity. The contrast sensitivity (CS) of form deprivation amblyopia was almost normal at low spatial frequency, but decreased at high spatial frequency and middle spatial frequency.

Contrast sensitivity (CS) can also be used for visual rehabilitation of amblyopia. The visual stimulator (CAM) uses the bars with strong contrast and different spatial frequencies as the stimulus source to stimulate the amblyopic eye to improve vision, and continuously rotates the bars so that the visual cells of the amblyopic eye can feel the stimulation of bars with different spatial frequencies in all directions. This visual stimulation rehabilitation method can significantly improve the visual acuity of patients, especially for moderate and mild patients with central fixation.