Vision tests are done to examine many different functions of the eye. While some of the vision tests are done to determine your ability to see details at near and far distances, check for gaps or defects in your field of vision and measure the eye’s ability to see different colors. Other tests are done to check your eye’s sensitivity to glare (brightness acuity), how well your eyes work in coordination to provide depth perception and more. Vision tests are usually done along with the eye examination that checks the overall health of the eyes.

Some common tests to check for low or blurred vision are:

Visual acuity (sharpness) tests.

Visual acuity tests. helps to find out the problem that affects how well you can see and check your ability to see details at near and far distances. These visual acuity tests normally involve reading letters or looking at symbols of different sizes on an eye chart. Generally, each eye is tested one by one and then both eyes may be tested together, with and without corrective lenses (if you wear them). There are several types of visual acuity tests that may be used.

Retinoscopy

To conduct a retinoscopy your optometrist uses a machine called a phoropter which is a thick instrument with numerous lenses and dials you look in to.

A retinoscopy allows the doctor to evaluate your optimal lens prescription. As you look through the phoropter, the optometrist flips different lenses in front of your eyes. As you focus on a prominent object in front of you (often the “E” on the top row of an eye chart), the optometrist shines a light into your eyes and observes how the light affects your eyes with different lenses.

Refraction test.

This test indicates your level of refractive error and finds out the right prescription for glasses or contact lenses. Refractive errors, like Myopia (nearsightedness) or Hyperopia (farsightedness), occur when light rays entering the eye can’t exactly focus on the nerve layer (retina) at the back of the eye. This causes blurred vision. For people who already wear glasses or contact lenses, a refraction test is done as a routine part of an eye exam. However, it can also be done if the outcome of the other visual acuity tests show that your eyesight is below normal and can be corrected by glasses.

Keratometry test

This is a test to measure the shape and curvature of the outside of the eye, known as the cornea. The shape of the cornea affects how your light perceives and reflects light. Some of the people have corneas with steep or elongated curves resulting in a condition called astigmatism. The Keratometry test is used to detect astigmatism, during which you gaze into a special machine. The doctor then adjusts the device so it aligns with your eye. Then the measurements of the machine are that which indicate your cornea’s shape.

Visual field tests.

Visual field tests are used to check for blind spots (called scotoma) in your side (peripheral) vision. Your complete visual field is the entire area your eye can see when you gaze in one fixed direction. The complete visual field is seen at the same time by both eyes. It includes the central visual field that detects the highest degree of detail as well as the peripheral visual fields.

Color vision tests.

Colour vision tests check your ability to distinguish colours. They are used to check colour blindness in people with optic nerve disease or suspected retinal or who have a family history of colour blindness. Colour vision tests are also used to screen applicants for jobs in fields where colour perception is essential, Color vision tests only identify a problem. More testing can be necessary to detect what exactly is causing the problem.

Intraocular pressure measurement

Glaucoma is among the leading causes of blindness. Vision loss happens when the intraocular pressure (IOP) inside the eye is very high, causing damage to the optic nerve. Monitoring IOP regularly is crucial for the early detection of the disease.

Tonometry is a test that measures the pressure inside your eye referred to as IOP. During this test, the eye is numbed with eye drops and a device called a tonometer gently touches your eye to measure the intraocular pressure. The procedure lasts just a few seconds and is painless. The instant results allow the doctor to establish if further glaucoma testing is required.

There are several other methods too for testing IOP, such as non-contact tonometry, electronic tonometry and Schiotz tonometry.

Pediatric Vision Tests 

Vision screening is typically used to check for possible vision problems in children. The most common eye disorders in children include:

• Amblyopia (lazy eye): Children with amblyopia have reduced or blurry vision in one eye.

• Strabismus (crossed eyes): In this disorder, the eyes don’t align with each other and point in different directions.

  When found early, both of these disorders can be easily treated.

Vision screening is also done to find the following vision problems, which affect both children and adults:

• Myopia (nearsightedness), a condition that makes far away things look blurry

• Hyperopia (farsightedness), a condition that makes close-up things look blurry

• Astigmatism (refractive errors), a condition that makes things at any distance look blurry

Why do children need vision screening?

Children should be screened regularly for better vision development.

• Infants. All newborn babies should be checked for eye infections or other disorders.

• 6 months: Eyes and vision should be checked during a regular baby visit.

• 1 to 4 years: Eyes and vision should be checked during general visits.

• 5 years and older: Eyes and vision screening should be done every year.

You may need to get your child screened if there are any symptoms of an eye disorder.

For infants three months or older, symptoms include:

• Not being able to make steady eye contact
• Eyes that don’t look properly aligned

For older children, symptoms include:

• Eyes that don’t look properly lined up
• Squinting
• Closing or covering one eye
• Trouble reading and/or doing close-up work
• Complaints that things are blurry
• Blinking more than usual
• Watery eyes
• Droopy eyelids
• Redness in one or both eyes
• Sensitivity to light