What an Autorefractor is used for

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An autorefractor is computer controlled and can’t completely remove the need for a qualified optometrist but they can make their lives a lot easier, improve accuracy and make optometry appointments a lot quicker.

Autorefractors are generally used at the beginning of an appointment to measure the refractive error of a person’s eyes, the computer does this automatically and once the patients head is in place on the machine the job takes only a second. The computer then calculates a prescription for the person’s eyes.

This prescription could be used and in situations where free eye tests are being given en masse such as part of a charitable mission to less developed countries the need for speed may mean a portable autorefractor does the entire test and perhaps only those with the most serious refractive error are further examined before giving them glasses.

In most optometrists though the results from the autorefractor are a starting point for the optometrist to use a series of lenses to get the best possible prescription.

The lenses test itself is far from perfect, the patient has to say whether images, usually a series of letters, are clearer or more blurred with different lenses but this is down to the patient’s interpretation and not 100% accurate. Starting of with results from an Autorefrator means that the patient can’t go far wrong from their ideal prescription.

The lenses tests are also far from ideal for children and those with other communication problems, that may sometimes include language. In these cases an autorefractor can come up with a prescription that though not always 100% perfect will drastically improve a persons sight.

To use an autorefractor the optometrist simply needs to ask the patient to put their head into the rest, one eye is examined at a time and the autorefractor uses a light and a recording device to measure at what angle the light comes back out of the patient’s eye: i.e. how much it has been refracted. To do this the light and recording device are aligned separately to avoid problems with shadows.

Other measuring methods including Retinoscopy take a lot longer and require a cyclopegic gel to stop the pupils from dilating, the results may be more accurate from this method but it isn’t always practical when patients don’t have time to wait for their sight to recover, important before going out in bright sunlight or driving.

By using a lens based test after autorefraction any slight errors in measuring a persons eyes can be removed which is why the dual test method is so popular with optometrists and patients wanting to give a test quickly but with a high level of accuracy. It is these kind of tests using an Autorefractor in fact that have led to the rise of free eye tests, a loss leader for opticians to get people in who may buy glasses, the low cost of an autorefractor based test means that such offers make financial sense.

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