Here’s What an Eye Exam Can Detect

A comprehensive eye exam (also called a routine eye exam) includes a variety of tests and procedures to evaluate the health of the eyes and vision. The exam takes at least an hour—including the 20 to 30 minutes it takes for pupils to fully dilate—with each test evaluating a different aspect of eye health.

The results are reviewed by an ophthalmologist or optometrist. Depending on a variety of risk factors, the cadence of eye exams varies from person to person.

Eye Conditions

A comprehensive eye examination is performed on a routine basis to check for various conditions of the eye, as well as other health problems. It may take at least an hour to complete, and it may include checking for some or all of the following conditions:

Strabismus

Also referred to as "crossed eyes," strabismus is when one eye is focused on a different object than the other eye and is considered misaligned.

In children, the brain often suppresses the image in the deviated eye; but in adults, a misalignment can cause double vision.

When strabismus is left untreated, it can lead to permanent reduction of vision in the deviated eye; this is called lazy eye (amblyopia). Regular eye exams for screenings and early intervention for strabismus are therefore imperative to prevent long-term vision loss.

Refractive Errors

When a person doesn’t have 20/20 vision (meaning the ability to see clearly, what the average person can see at a distance of 20 feet away), it’s called a refractive error. A test called retinoscopy uses a tool called a retinoscope for an examination aimed at measuring the refractive error of the eyes.

Refractive error is a common eye disorder involving the inability to clearly focus on images. The result is blurred vision, and if the refractive error is severe, it could result in visual impairment.

Refractive errors can include several types of eye conditions, including:

• Astigmatism
• Hyperopia
• Myopia
• Presbyopia

To employ the refraction test, the ophthalmologist may flip back and forth between different lenses you are asked to view, asking you to report which lens appears clearer to you.

Glaucoma

Several different tests can be performed to measure the normal level of fluid pressure inside the eyes. 

Five different eye exams can be used to help diagnose glaucoma. Most routine glaucoma eye exams employ at least two types of glaucoma tests, including tonometry and ophthalmoscopy.

If you are diagnosed with glaucoma, you may want to consider getting a second opinion or consulting with a glaucoma specialist, because some people have glaucoma that is particularly difficult to diagnose or treat.

Optic Nerve

The swinging flashlight test is performed by swinging a light back and forth in front of both eyes and comparing the reaction of light stimulation in both eyes. The swinging flashlight test helps to differentiate whether a decrease in a person’s vision is caused by an eye problem (such as a cataract) or whether it is a defect in the optic nerve.

Conditions that the swinging flashlight test can help detect include:

• Optic neuritis
• Ischemic optic disease
• Retinal disease
• Severe glaucoma causing trauma to the optic nerve
• Optic nerve damage from trauma or a tumor
• Retinal detachment
• Very severe macular degeneration

Retinal Conditions

A retinal examination—also called ophthalmoscopy or funduscopy—is performed to assess the back of your eyes. A retinal examination can be accompanied by an imaging test called digital retinal imaging (high-resolution imaging to take pictures of the inside of the eye) to check for conditions such as:

• A detached retina
• Diabetes
• Macular degeneration

Health Conditions

There are many types of health conditions that can be diagnosed by performing an eye examination. Many conditions can be detected in the earliest stages. Medical conditions that are often detected during an eye exam include:

Pupillary Reaction Conditions

A pupillary reactions test measures how the pupils of the eye respond to light.

An ophthalmologist observes the pupils closely, noting the size and shape, as well as ensuring that both pupils respond consistently, in response to light.

Several conditions are commonly linked with an abnormal pupillary response to light, including:

• Anisocoria: A condition involving one pupil that is wider than the other; it can be normal in many people, but it could indicate a possible infection or nerve problem.
• Cluster headache: A condition involving a cluster of headaches on one side of the face that often causes the pupil on the affected side to be unusually small or “miotic”
• Horner syndrome: A condition involving injured nerves that travel from the brain to the face; the underlying cause could be a stroke, trauma, or a tumor.
• Oculomotor nerve damage: Damage to the nerves that control eye movement
• Brainstem lesions: Such as brain tumors
• Response to certain medications: Such as barbiturates, alcohol, opiates, or other types of sedatives
• Optic nerve injury: Any kind of injury or damage to the optic nerve, including trauma, inflammation, disease, or deterioration

Brain Tumors

Tumors in the brain can cause an increase in pressure in the brain that impacts intraocular pressure (IOP). 

When swelling occurs near the back of the eyes, it causes changes to the optic nerve that can be detected during an eye exam. Other visual changes caused by a brain tumor may include:

• A change in pupil size
• Double vision
• Loss of peripheral (side) vision

Aneurysm

An aneurysm is a weakness in the blood vessel wall; the weakened blood vessel wall could burst and cause a person to have a stroke if the defective blood vessel supplies blood (and oxygen) to the brain.

An eye exam can reveal:

• Increased swelling in the optic nerve
• Increased pressure in the brain

These are all signs of a brain aneurysm.

Various Types of Cancer

A comprehensive eye exam can reveal signs and symptoms of various types of blood, tissue, or skin cancer.

Skin cancer (such as melanoma, squamous cell cancer, and basal cell cancer) can impact the outer surfaces of the eyes and the eyelids.

Sometimes other types of cancer—such as lymphoma and leukemia—can have an impact on the interior structures of the eyes.

An eye exam—using methods such as binocular indirect ophthalmoscopy or a slit-lamp biomicroscope—can help the ophthalmologist detect signs of cancer, such as enlarged blood vessels, that may indicate there is a tumor inside the eye.

Diabetes

Diabetic retinopathy is a common eye disorder that people with diabetes develop.

Sometimes retinopathy occurs in the eyes before a person is diagnosed with diabetes. In fact, it can be the very first indication that a person has diabetes.

Diabetic retinopathy causes tiny blood vessels in the retina to leak yellow fluid or blood. A retinal exam can lead to early detection of diabetic retinopathy, which can help people avoid vision loss and prevent other complications of diabetes..

Hypertension (High Blood Pressure)

An eye exam can reveal some unusual findings in the blood vessels in the back of the eye, such as bleeding and unusual anatomy (like kinks or abnormal bends in the blood vessels).

These signs may be observed during a dilated eye exam. This can be a sign of hypertension, a common disorder that impacts many people.

High Cholesterol

High cholesterol is a condition that can lead to plaques that may be detected during an eye exam.

Another sign of high cholesterol that can be detected during an eye exam is a yellow or blue ring around the cornea (particularly when present in a person less than 40 years old).

Lupus

Lupus is an autoimmune, inflammatory disease that is commonly linked with an eye condition called dry eye syndrome.

Swelling of several parts of the eye can also occur from lupus; this can include swelling of the:

• Sclera: The white part of the eye
• Uvea: Vascular middle layer
• Retina: Light-sensitive tissue in the back of the eye

Lyme Disease

Lyme disease is an infection caused by specific species of ticks. Lyme disease involves symptoms of inflammation of the body as well as inflammation of the optic nerve, which can be detected during a comprehensive eye exam. 

Another symptom that may occur due to Lyme disease is eye floaters (dark lines or spots drifting through a person’s field of vision), which often occur when the infection begins.

Multiple Sclerosis

Multiple sclerosis is a degenerative disorder that impacts the nervous system. It can also affect the optic nerve, causing inflammation.

Oftentimes, inflammation of the optic nerve is exhibited by:

• Blurred vision
• Double vision
• Pain when moving the eyes

These symptoms can be detected during a comprehensive eye exam.

Rheumatoid Arthritis

Signs that can be detected during an eye exam that may indicate a person has rheumatoid arthritis include:

• Inflammation and pain of the sclera of the eye
• Reddened eyes with severe pain

These symptoms may indicate a person has a condition called scleritis and may require immediate medical intervention.

Dry eye is another eye condition that often occurs in people with rheumatoid arthritis.

Sjogren's Syndrome

Sjogren’s syndrome is an autoimmune disorder, manifested by the body’s white cells attacking the glands that produce saliva and tears that lubricate and cleanse the eyes. Therefore, a lack of the proper level of tear production leads to dry eyes in people with this condition.

In addition to symptoms of dry eyes (such as itchy, dry, reddened, and excessive tearing), burning and stinging as well as blurry vision are common symptoms of this autoimmune disorder.

Thyroid Disease

Thyroid disease, such as hyperthyroidism (an overproduction of thyroid hormones), is commonly caused by a condition called Graves' disease.

Grave’s disease can cause symptoms of the eye, including:

• Protruding eyeballs and retracting eyelids (a telltale sign of thyroid disease)
• Blurry vision
• Vision loss

Vascular Disease

Bleeding disorder and blood vessel clotting disorder can manifest as bleeding in and around the eye that is visible.

This bleeding is medically coined subconjunctival hemorrhages, which can also involve retinal bleeding that can lead to vision loss. A comprehensive eye exam can detect hemorrhaging of the eyes, linked with vascular disease.

Vitamin A Deficiency

Night blindness and dry eyes are conditions commonly seen in people who are deficient in vitamin A. This is because vitamin A helps to produce the moisture in the eyes that keeps them lubricated.

Vitamin A deficiency may lead to night blindness by resulting in a lack of certain pigments needed for the proper function of the retina. Vitamin A deficiency is the number one reason for blindness in children worldwide.

A Word From Verywell

A routine eye exam may result in the first step to early diagnosis of many different types of illnesses. Getting regular eye exams is a very important part of taking care of your overall health, so be sure to follow the recommendation of your healthcare provider regarding how often to see your ophthalmologist.