How is a Glasses Prescription Determined?

by Jan 17, 2022

Everyone that wears glasses has a unique prescription for their right eye and left eye. An eye doctor can determine the correct prescription for each eye.


Methods of Determining Glasses Prescription

There are several methods an eye doctor can use to determine a glasses prescription. Some methods require feedback from the patient and are therefore not suitable for infants or non-communicating patients.

The two main methods which do not require any feedback from a patient are retinoscopy and autorefraction.

The main method that does require patient feedback is called subjective refraction.


Using Retinoscopy to Determine a Prescription

Retinoscopy is a technique which requires special training and experience with an instrument called a retinoscope.

Using the retinoscope, an eye doctor can shine a light into the eye of the patient and then use prescription lenses to correct any refractive error in the eye.

This technique simply requires the patient to look at a target in the distance while the doctor performs the retinoscopy.

Since this technique does not require feedback or for the patient to be at a table or in a chair, it is often the best option for children, patients which are bedridden, or patients who cannot easily communicate.

Additionally, this technique can be performed outside of a traditional office as the equipment needed is handheld and very mobile.


Using Autorefraction to Determine a Prescription

Autorefraction is a technique which requires an instrument known as an autorefractor. The autorefractor can estimate a glasses prescription with good accuracy without any patient feedback or operator input.

Since the autorefractor can quickly estimate the glasses prescription, it is often included in a basic eye exam before a more thorough subjective refraction.

Also, some autorefractors are mobile instruments and can be used for screening purposes such as school screenings or at pediatrician’s offices.


Using Subjective Refraction to Determine a Prescription

Subjective refraction is the most common method of determining a glasses prescription.

This is the only method that utilizes patient feedback to refine the prescription before finalization.

In this method, an eye doctor will present a series of lenses and ask for various patient responses, such as which is the lowest line that can be read, which of two lines is clearer, and the famous, which is better, one or two?

By asking these questions, the eye doctor is able to gain insight into the patient’s vision and prescribe the best possible glasses for their specific needs.

In many cases, a subjective refraction is the only technique used to determine the glasses prescription as it is considered to be the gold standard.

If a patient already has had glasses or the eye doctor has evaluated the patient previously, the subjective refraction can be used to identify any changes and modify the glasses prescription as needed.


Importance of Having an Eye Doctor Determine Your Glasses Prescription

Since prescription glasses are made for every individual, it is important that an eye doctor determines your glasses prescription and then regularly checks for any changes.

With age, it is expected that your glasses prescription will change throughout your life and an eye doctor will be able to determine an accurate prescription for your needs.

Our eye doctors at EyeDocs Family Eye Care in Brookville, OH excel in prescription of glasses, contact lenses and the diagnosis of a variety of eye diseases. Call our optometrists at 937-770-1265 or schedule an eye exam appointment online if you would like to be evaluated for a new glasses prescription. Our eye doctors, Dr. Kyle Maxam and Dr. Cara Wampler, provide the highest quality optometry services and eye exams in Brookville, Ohio.

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