The computer optometry developed in the 1970s to the present day belongs to the objective optometry method. The machine used for this optometry is a combination of optical, electronic, and mechanical instruments, and its principle is basically the same as that of the retinoscopy method.
In addition, an infrared red light source and an automatic fogging device are used to achieve the purpose of relaxing eyeball adjustment. Its simple operation and fast speed are a major advancement in optometry technology.
However, various computer optometry machines inevitably produce certain errors. Although infrared light sources and automatic fog vision devices are used to relax the adjustment, they cannot completely eliminate the effect of adjustment. Especially young people have strong accommodative power, and simple computer optometry is often inaccurate. If it is really necessary to use computer optometry, it should also be done after anaesthetizing the ciliary muscle with eye drops before optometry. The main errors in the results of computer optometry are high myopia and misalignment of the astigmatism axis. Therefore, the results of computer optometry can only be used for clinical reference and cannot be directly used as prescriptions for glasses.
The expression of the power of the glasses: S: means spherical lens, (-) is for nearsightedness, (+) is used for hyperopia and presbyopia; C: means cylindrical lens, used for astigmatism; DS: used to mark the focal lens of spherical lens degree.