Objective Methods of Refraction


Refraction is the process of determining the correct eyeglass or contact lens prescription needed to correct vision problems such as nearsightedness, farsightedness, and astigmatism. It is an important part of a comprehensive eye exam and is typically performed by an eye care professional.

There are several methods of refraction, including both objective and subjective methods. Objective methods do not require input from the patient, while subjective methods involve the patient's feedback in determining the correct prescription.

Objective Methods of Refraction

Autorefractor

An autorefractor is a machine that uses a computer and a light source to measure the refractive error of the eye. The patient looks into the machine and the light is shone into the eye. The reflection of the light is then measured and used to calculate the eyeglass or contact lens prescription needed to correct the patient's vision.

Autorefractors are generally quick and easy to use and do not require any input from the patient. They are often used as a starting point for determining the eyeglass or contact lens prescription, but may not be as accurate as other methods.

Autokeratometer

An autokeratometer is a machine that uses a light source and a camera to measure the curvature of the cornea, which is the clear outer layer of the eye. The measurement is used to calculate the eyeglass or contact lens prescription needed to correct the patient's vision.

Autokeratometers are generally quick and easy to use and do not require any input from the patient. They are often used as a starting point for determining the eyeglass or contact lens prescription, but may not be as accurate as other methods.

Objective Refraction System (ORS)

An objective refraction system (ORS) is a machine that uses a light source and a camera to measure the refractive error of the eye. The patient looks into the machine and the light is shone into the eye. The reflection of the light is then measured and used to calculate the eyeglass or contact lens prescription needed to correct the patient's vision.

ORS systems are generally quick and easy to use and do not require any input from the patient. They are often used as a starting point for determining the eyeglass or contact lens prescription, but may not be as accurate as other methods.

Subjective Methods of Refraction

While objective methods of refraction do not require input from the patient, subjective methods involve the patient's feedback in determining the correct eyeglass or contact lens prescription. These methods are generally more accurate than objective methods, but may take longer to perform.

Phoropter

A phoropter is a machine that is used to determine the eyeglass or contact lens prescription needed to correct the patient's vision. It consists of a series of lenses that the patient looks through while reading an eye chart. The eye care professional will ask the patient which lens is clearer and will use their feedback to determine the correct prescription.

Retinoscopy

Retinoscopy is a method of refraction that involves shining a light into the eye and observing the reflection of the light on the back of the eye (the retina). The eye care professional will use a hand-held instrument called a retinoscope to shine the light into the eye and will adjust the lenses in the phoropter based on the reflection of the light.

The patient will be asked to look at an eye chart while the lenses in the phoropter are adjusted, and the eye care professional will use the patient's feedback to determine the correct eyeglass or contact lens prescription.

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