The sight test and eye examination

An introduction to the work optometrists undertake during a sight test

This guide provides information on the sight testing process.

The vast majority of sight tests in the UK are conducted by optometrists. The sight test performs two functions:

  • An ocular health check: An optometrist will check for any eye health abnormalities and underlying health conditions, referring if necessary
  • Checking the eye for any refractive error that may require corrective lenses

It is a common misconception that optometrists just prescribe glasses. Optometrists are community primary care eye specialists who are experts in detecting eye conditions. The sight test is one of the best value and most important public health measures.

Optometrists should be the first port of call for any eye related issues.

The sight test procedure
Optometrists perform a number of procedures during a routine sight test. Most optometrists begin the sight test by establishing the reason for the visit, which may be routine, or could have been prompted by a specific concern. The optometrist may ask questions about the patient’s eyes and vision, ocular history, general health, medications, family history, occupation and hobbies.

The optometrist will measure the level of vision in each eye, and assess the patient’s binocular vision status (how well the eyes work together). The optometrist will normally use an ophthalmoscope or slit-lamp biomicroscope to examine the health of the eyes internally and externally, to check for any abnormalities. These tests can sometimes detect signs of underlying general health conditions such as diabetes or hypertension.

The optometrist will also establish whether an optical appliance, such as glasses or contact lenses, is required to correct the vision at specific distances. This is usually done by asking the patient to view letters on a chart through different lenses; other methods can be used to establish an accurate optical prescription in patients who are unable to respond, such as very young children.

At the end of the sight test, the optometrists will explain the results of the sight test, whether there is any need for corrective lenses, and issue a prescription or refer the patient to a medical practitioner if required.

Additional tests
Optometrists may perform a number of other tests as necessary, for example to check the intraocular pressure inside the eye, measure visual fields (peripheral vision) or to check stereoscopic (3D) and colour vision.

A tonometer measures the pressure in the eye. There are various different tonometers and common ones blow a small puff of air into the eye. Raised pressure in the eye is often a sign of an ocular abnormality such as glaucoma.

A visual fields test will examine your peripheral (side) vision. These tests are used to detect blind spots in peripheral vision which are often symptomatic of certain eye conditions most notably glaucoma.