The measurement of contrast sensitivity (CS) vision requires the measurement of contrast sensitivity (CS) chart, which measures two variables: size and contrast; Only one variable was measured by routine visual acuity chart.

Therefore, the visual target of contrast sensitivity (CS) visual acuity chart is usually composed of a series of black (or gray) and white stripes with different frequencies and contrasts. The black-and-white stripes with high contrast are called square waves. If the edge is fuzzy and the black gray stripes corresponding to the white background are called sine wave stripes.

There are two main methods to measure contrast sensitivity (CS) vision. The first method is to keep the spatial frequency unchanged and measure the contrast threshold of a spatial frequency pattern that can be seen just after subjective judgment. Usually, the sinusoidal fringe pattern method is used. The change of the light and shade of the fringe is a sinusoidal curve, and the light and shade gradually shift. When the contrast is lower than this threshold, the fringe gap becomes a uniform gray, and the human eye cannot distinguish the fringe; The second method is to keep the contrast unchanged and determine the threshold of recognizable spatial frequency. Square stripes are used. The light and dark of the stripes are clear without transition zone.

The commonly used contrast sensitivity (CS) visual acuity chart in practical work is the VCTs contrast visual acuity chart. The visual signs are divided into five rows a, B, C, D and E, representing the spatial frequency of 1.5, 3, 6, 12 and 18 cycles / degree. There are 9 circular bar graphs from left to right in each row, and the contrast sensitivity (CS) increases in turn. Figure 9 is a blank graph without bars, and the bars are divided into vertical, right oblique and left oblique.

Inspection steps:

① The examinee's ametropia was completely corrected. The right eye was measured first and then the left eye.

② The distance is 40cm for near contrast sensitivity (CS) and 3M for far contrast sensitivity (CS). Let the examinee first understand the form and identification method of the visual target.

③ Cover the untested eye, start from line a, gradually recognize the direction of the visual mark stripe from 1-9 until it cannot be recognized, and mark the number of the visual mark on the vertical line a on the recording paper. In the same way, from row B, row C... To row E. The other eye was then examined and recorded.

④ Connect the numbers marked on each line of the recording paper with a straight line to form a curve and analyze the results.

The abnormal contrast sensitivity (CS) curve has the following possibilities: the curve is not within the normal range (gray area) in the record form; The difference of contrast sensitivity (CS) curve between two eyes of the patient has more than two numbers of aberrations at any certain frequency.

Normal contrast sensitivity (CS) is the combination of the optical contrast sensitivity (CS) of the eyeball and the contrast of the neuroretinal system. Therefore, the optical changes of any part of the eyeball or the changes of the neuroretinal system can lead to the changes of CSF curve. In general, the contrast sensitivity (CS) curve at low frequency is decreased in the retinal nervous system, and the contrast sensitivity (CS) curve at high frequency is decreased in the corneal and other refractive media.