Like you said that the optical inaccuracy does not exist, the working principle of the hand-held optometrist and your common desktop equipment, that is, the class of China's Class II medical device optometrists are similar. Medical device optometry is similar, are the use of infrared light source and automatic fog vision device to achieve the purpose of relaxation of eye adjustment, the use of photoelectric technology and automatic control technology to check the refractive error.
And optometry can not replace the photographer optometry and lens correction technology, only to the manual optometry to provide reference.