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American Foundation for the Blind® | Reader's Digest Partners for Sight

The Difference between a Vision Screening and a Comprehensive Eye Examination

What Is a Vision Screening?

A vision screening is a relatively short examination that can indicate the presence of a vision problem or a potential vision problem. A vision screening cannot diagnose exactly what is wrong with your eyes; instead, it can indicate that you should make an appointment with an ophthalmologist or optometrist for a more comprehensive dilated eye examination.

However, there is no clear evidence on the accurateness and effectiveness of a visual screening for open-angle glaucoma (U.S. Preventive Services Task Force, 2013). A comprehensive dilated eye exam is the most effective detection method.

What Is a Comprehensive Dilated Eye Examination?

A comprehensive dilated eye examination generally lasts between 30 and 60 minutes, and is performed by an ophthalmologist or optometrist. It should always include the following components:

A Health and Medication History

  • Your overall health and that of your immediate family
  • The medications you are taking (both prescription and over-the-counter)
  • Questions about high blood pressure (hypertension), diabetes, smoking, and sun exposure.

A Vision History

  • How well you can see at present, including any recent changes in your vision
  • Eye diseases that you or your family members have had, including macular degeneration and glaucoma
  • Previous eye treatments, surgeries, or injuries
  • The date of your last eye examination

As part of the vision history, the doctor may ask you the following questions:

  • Are you having any problems with your vision?
  • How long have you had these problems?
  • When do these problems occur?
  • When was your last eye examination?
  • Do you have any family history of eye problems?
  • How is your general health?
  • What medications are you taking?
  • Do you have any allergies?

This history of your own health and that of your family can give the doctor an indication of any issues that may be affecting, or could affect, your vision.

An Eye Health Evaluation

  • An examination of the external parts of your eyes: the whites of the eyes, the iris, pupil, eyelids, and eyelashes.
  • A dilated internal eye examination: Special eye drops will dilate, or open, your pupil, which allows the doctor to observe the inner parts of your eye, such as the retina and optic nerve. This can help to detect subtle changes of the optic nerve in persons without any visual symptoms and potentially lead to early detection of disease.
  • A test of the fluid pressure within your eyes to check for the possibility of glaucoma.

A Refraction, or Visual Acuity Testing

a phoropter

A refraction helps determine the sharpness or clarity of both your near (reading) and distance vision.

This includes testing your vision with different lenses (sometimes contained in a machine called a phoropter, pictured at right) to determine if your vision can be improved or corrected with regular glasses or contact lenses.

Visual Field Testing

Visual field testing helps determine how much side (or peripheral) vision you have and how much surrounding area you can see.

Humphrey Field Analyzer

The most common type of visual field test in a comprehensive eye exam is called a confrontation field test, in which the doctor briefly flashes several fingers in each of the four quadrants (above, below, right, and left) of your visual field while seated opposite you.

In some cases, your doctor may also want to perform a more precise visual field measurement, using a computerized visual field analyzer, such as the Humphrey Field Analyzer (pictured at left).

Your Examination Results

The doctor will be able to determine if the visual problems you are experiencing are normal age-related changes or are disease-related, and if additional testing, referral to another doctor or specialist, or treatments are needed.

Locate an Eye Care Professional in Your Area

Also see What is a Low Vision Examination? on this website.

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