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Changes in the health of the eyes happen gradually without any obvious signs of disease.
Changes in the health of the eyes happen gradually without any obvious signs of disease. Eye test helps detect eye problems at an early stage; hence, treatment can be started immediately to reduce the risk of any permanent damage to the eyes. An eye test or examination done by an optometrist or ophthalmologist involves a comprehensive series of tests to evaluate the visual abilities and health of the eyes.
Types of eye tests done by an optometrist
Common eye tests are as follows:
Visual acuity test
This test evaluates how clearly a person can see. Using one eye at a time, a person would be asked to read different letters of the alphabet, printed on a chart that is positioned at a specific distance. Each eye is tested separately, and the responses are used to determine the vision level. Near and far vision are tested by different methods. A distant vision test involves looking at an eye chart about 10-20 feet away, through a special device called phoropter. The optometrist will then place different lenses in front of the eyes to see which lens pair provides the clearest vision. The result determines whether a person is near-sighted or affected by astigmatism. This test may also show that a person does not need vision correction prescription. Another type of chart is used to examine the near vision.
Retinoscopy
A retinoscopy provides an approximation of vision prescription. During this test, the eyes will focus on a target, typically “E” on the top row of an eye chart. The optometrist shines a light into the eyes and watches how the light affects the eyes with different lenses. Based on how the light reflects from the eye, the power of the lens that will help correct the vision is estimated.
Keratometry test
Keratometry test is used to detect astigmatism. During a keratometry test, a person gazes into a special machine that is adjusted to align with the eye. The machine’s measurements indicate the shape and curve of the outside of the eye, known as cornea. Corneas with steep or elongated curves result in a condition known as astigmatism.
Intraocular pressure measurement or glaucoma test
This test measures the intraocular pressure created by the fluid within the eyes. Higher pressure indicates a higher risk of glaucoma.
Visual field tests evaluate the peripheral vision. These tests identify gaps in peripheral vision. They can detect the presence of scotomas or blind spots that may be caused by eye diseases such as glaucoma. Types of visual field tests include:
- Automated perimetry
- Confrontation visual field exam
- Tangent screen exam
Slit-lamp exam
During this test, a lighted magnifying device is used to examine the internal ocular structures of the eyes. This test helps detect early signs of diseases such as cataracts, glaucoma, detached retina, corneal ulcers, dry eye disease, diabetic retinopathy, and macular degeneration.
Ultrasound test
This test uses sound waves to provide a picture of the eye’s internal structure, which helps in detecting ocular tumors, cataracts, retinal structure, and hemorrhage. This eye test is also done for preoperative evaluation for cataract surgery.
Pupillary dilation test
During this eye test, special drops are put in the eye to dilate the pupil. Dilating the pupils help examine the retina for any signs of disease.
Ocular motility test
This test assesses the accuracy of eye movements that are essential for reading, sports, and other skills.
Color vision test
This test checks for signs of color blindness, as well as ocular health problems, which may affect color vision.
Cover test
This test evaluates eye alignment and rules out problems such as eye misalignment or lazy eye.
Stereopsis test
Depth perception and lazy eyes are measured through the use of three-dimensional (3D) glasses.
How should eye tests be scheduled?
Scheduling:
- Children below 3 years of age: Eye problems such as lazy eyes, crossed eyes, or misaligned eyes should be checked by the pediatrician.
- Routine eye test should be done for:
- Children and adolescents: every 1-2 years
- For adults: With no symptoms of vision problems, every 5-10 years; above 40 years of age, every 2-4 years; and above 65 years of age, every year.
- Eye exam should be done more often if a person has
- Any issues with their eyes or vision (uses glasses/contact lenses).
- Family history of eye disease or loss of vision.
- Chronic disease such as diabetes.
- Been taking certain medications that cause side effects that affect the eyes.
If the eye tests yield abnormal results, further testing or treatment plan for an underlying condition would be suggested.