In this modern era of science and technology, when everything is controlled by computerized automated machines. Then why refraction is remained from that list although as an Optometrist we will never ignore the importance of Retinoscopy till now Retinoscopy is the one and only golden procedure for refraction. But at the same time, we can’t also criticize the benefits of modern Autorefractometer machine as they are able to give a result of refractive status of the eye which is almost accurate in a very short period of time which is helpful for the Optometrist to perform many refractions in a very short period of time. Autorefraction is a very good process we can perform with retinoscopy. Optometrist those who have to serve a large number of patient daily basis they can reduce examining time by checking the patient first from autorefractometer then again check the power by retinoscope and finally prescribed the final result after finishing all the subjective test. And it will be also helpful for the future optometrist and young optometrist those who are actually in a learning stage of refraction they can easily get a rough idea weather their refraction is nearly accurate or not by checking the patient in autorefractometer after finishing their refraction process. So, by this way we can take autorefraction as a process of refraction along with retinoscopy.
If we look back to the history of autorefractometer the idea usually applicated first at around 1970’s but it was failed to full fill the clinical purpose because of its inaccurate results due to mainly accommodation and other factors of the eye. Later in Japan another almost accurate autorefractometer first made which based on a scientific idea patented by scientist Antonio Medina Puerta. Usually now days the modern autorefractometer are based on the Schreiner disc principle where double pinholes are placed Infront of the Patient’s eye to determine the level of Ametropia present.
Development of Autorefractometers, we can divide autorefraction into two stages
- Early Objective Autorefractors.
- Modern Autorefractors/ Modern Objective Autorefractors.
- Early Objective Autorefractors: The early developed Autorefractometers are known as early objective autorefractors. Usually, these instruments are based on Optometer/ Badal Principal. And the examiner has to play a vital role while examining these instruments by clearing the object. Most of the times the result is not match with subjective and retinoscopy results as this instrument were unable to perform in accommodation and irregular Astigmatism. Now days when modern autorefractors can perform in case of child and uncooperative patients. The earlier generation of autorefractometers also unable examine in little alignment problem and little movement of patient head also gave error in result. Although these refractometers are the only available automated refraction machine on those times, they use in many clinics due to These machine’s disadvantages scientists start developing modern autorefractometers.
- Modern Autorefractometers: The modern autorefractometers are usually based on the scheiner discs principals. Usually, Objective modern autorefractometers are mostly and popularly used all over the world. But scientist have also developed Autorefractometers that can abele to perform both Subjective and Objective refraction together. As the purpose of development of Modern Autorefractometers is to eliminate the Limitation of its early generation machines so obviously they can’t overcome all the problems properly but they can surely reduce that problem in a large amount.
Procedure of Autorefraction:
Most of the instruments usually have two sides one side is for the patient and the other side is for the examiner. And all the instruments must be placed over an automated table unit. We must provide the patient a very good sitting arrangement in a Ophthalmic chair or a clinical stool where the patient can sit comfortably. Then we have to instructed the patient how to place his chin and head on the chin rest area, after council the patient properly about the examination we have come to the examiner side to focus the target perfectly to get the accurate result. Usually in most of the instruments a colorful image is use as a target where the patient have to focus and the examiner has to place the target properly by clearing the image of the eye on the screen of the machine with the help of a joystick or in many devices automated focusing system also available where the examiner has to only instructed the patient and after that allow the machine for examination. Most of the time the examiner takes three readings separately in different eyes and the machine also provides an average result from the three different results. Now days also Keratometry facility available in autorefractometers which is more helpful in clinical practice. Portable Autorefractometers are also available they can be use in mobile eye care units.