Definition & Overview
An eye exam is a general term for a range of tests performed to assess eye health. These can range from very simple ones, such as having to read a standard eye chart, to highly complex tests that make use of high-powered lenses and machine to view the eye's internal structures.
Routine eye exams are very important, regardless of age or physical health. These are performed not only to examine prescription for eyeglasses or contact lenses but also to check for common eye diseases and evaluating eye health as an indicator of overall wellness. Moreover, eye doctors are able to detect and diagnose chronic systemic diseases based on eye tests.
Who Should Undergo and Expected Results
Regular eye examinations are recommended for everyone as a routine health maintenance check. Adults must undergo eye tests to keep prescription up-to-date and determine early signs of eye disease. On the other hand, children must also seek the expertise of eye doctors to ensure the normal development of their vision and to confirm visual acuity and skills that are required for schoolwork. Ideally, one routine eye exam per year is suggested.
However, there are cases when an eye exam should be sought more urgently. Among common signs and circumstance that require an eye exam scheduled soon are as follows:
- Eyes appear red or dry, or uncomfortably itchy for unknown reasons
- Seeing flashes of light, dark spots or floaters
- Those who have diabetes or other health condition that affects the eyes
- Difficulty in driving or seeing at night or in the dark
- Those who experience headaches, blurred vision, eye strain or dizziness after using the computer or any device for an extended period
- Those who experience dizziness, motion sickness or having trouble following a moving target
- Having to hold books at a further distance from the face or having to squint to read clearly
- Any changes in vision
- After head trauma that led to changes in vision
Patients who have a family history of conditions like glaucoma or diabetes (diabetic retinopathy), especially those who are in their 50's or older require more eye exams. It is also critical for detecting and diagnosing conditions such as age-related macular degeneration and cataracts.
How is the Procedure Performed?
During eye tests, ophthalmologists examine the eyes for visual clarity to determine the need for prescription glasses or contacts. They also check the eyes for possible diseases or problems that may ultimately lead to vision impairment or loss. An eye exam usually consists of these steps:
- For first-time patients, doctors usually ask about the patient’s medical history or symptoms of vision problems currently being experienced.
- The doctor will perform a visual acuity test to determine the need for glasses or contact lenses to improve vision.
- The doctor will use a light to evaluate the front and inside of the eye. Eye drops may be placed to dilate the eyes or to measure eye pressure.
Depending on the symptoms, the ophthalmologist (eye doctor) may suggest or perform the following tests:
Eye muscle test - This checks the health of muscles that control eye movement and evaluates signs of muscle weakness or poor coordination.
Visual acuity test - This is a standard test to measure the clarity of vision and is usually done by reading letters of different sizes printed on a chart.
Refraction assessment - This is often done using a computerised refractor or through retinoscopy to estimate prescription for glasses or contact lenses. Refraction assessment is usually fine-tuned afterwards through a device that contains different lenses to find a combination that gives the best vision.
Visual field test (Perimetry) - This determines the full extent of one's visual field. Visual field loss may indicate possible eye condition.
Colour vision testing - This evaluates colour deficiency and determines colour blindness.
Slit lamp examination - A slit lamp microscope is used to examine inner eye structures. Fluorescein drops to colour the film of tears over the eyes are usually administered to help reveal any damaged cell.
Retinal examination (Ophthalmoscopy/Funduscopy) - This allows the examination of the back structures of the eye, including the retina, to check for possible eye disease.
Glaucoma screening (Tonometry) - This measures eye (intraocular) pressure to detect glaucoma, a condition that damages optic nerves. This can be done without a machine (non-contact) or using a slit-lamp tonometer (applanation tonometry).
Corneal thickness test: This is recommended when eye pressure is higher than normal and is performed with a special instrument that uses sound waves to measure cornea thickness. This takes only a few seconds and requires an anaesthetic eye drop.
Possible Risks and Complications
Eye exams usually take a few minutes to less than an hour to perform. These routine tests are simple and quick to carry out, and usually without risks and complications. However, certain tests that require anaesthetic or fluorescein drops may temporarily lead to a blurred vision which typically goes away within a few hours.
- Emmett T. Cunningham; Paul Riordan-Eva. Vaughan & Asbury's general ophthalmology. (18th ed.). McGraw-Hill Medical.