Aneurysm

An aneurysm is a bubble in the wall of a blood vessel. This weak wall can leak or rupture. Severe, one-sided headache or loss of facial or body function are all signs of an aneurysm. Aneurysms can be catastrophic and require immediate medical attention.

Brain tumor

Tumors can cause increased pressure in the brain that gets transmitted to the eye. Swelling near the back of the eyes causes changes to the optic nerve which an eye doctor can see. Loss of side vision, recent double vision or changes in the size of a pupil are other signs of a brain tumor.

Cancers of blood, tissue or skin

Numerous cancers can be found during a detailed eye exam. Skin cancers affect the eyelids and even the outer surfaces of the eye. The most common types of skin cancers are basal cell, squamous cell and melanoma. Leukemia and lymphoma can affect the interior aspect of the eye. Tumors in the breast and other areas can spread to the ocular structures.

Diabetes

Tiny blood vessels in the retina that leak yellow fluid or blood can be a sign of diabetic retinopathy. Sometimes, this disease can appear in eye tissue even before a person has been diagnosed with diabetes. Early detection can help people avoid vision loss and other serious complications.

Giant cell arteritis

Giant cell arteritis (GCA) is a lingering inflammation of medium-sized arteries that affects the arms, upper body and neck. These same arteries help nourish the eyes, and inflammation can result in blurred vision, double vision, or even sudden vision loss in one or both eyes. A dilated eye exam and blood tests for this condition can allow for an early diagnosis of GCA. Medical treatment can  help prevent a lifetime of blindness or even early death.

High blood pressure

High blood pressure affects one in  three Americans. Unusual bends, kinks or bleeding from blood vessels in the back of the eye can signal high blood pressure. High blood pressure is a big known risk factor in the onset and/or progression of glaucoma, diabetic retinopathy, macular degeneration and other diseases. Your doctor may notice signs of high blood pressure during a dilated eye exam.

High cholesterol

A yellow or blue ring around the cornea may be a sign of high cholesterol, especially in a person younger than age 40. Deposits in the blood vessels of the retina can also indicate elevated cholesterol. This may be the precursor to a life-threatening stroke.

Lupus

This inflammatory disease can coincide with dry eyes. Lupus can also cause swelling in the white part of the eye, the middle layer of the eye or the light-sensitive tissue in the back of the eye.

Lyme disease

Lyme disease is an infection spread by ticks, which leads to inflammation throughout the body. Many people with Lyme disease experience inflammation of the optic nerve as well as an increase in floaters at the onset of infection.

Medication toxicities

Several medications may be toxic to the retina and the optic nerve. Symptoms of toxicity include red, scaling eyelids, red eyes, scratchy corneas or conjunctivitis.

Multiple sclerosis

Inflammation of the optic nerve can be a harbinger of multiple sclerosis, a degenerative disease that affects the nervous system. Often, this inflammation goes hand-in-hand with severely blurred vision, painful eye movement or even double vision.

Myasthenia gravis

Myasthenia gravis is an ongoing autoimmune disorder that makes the muscles weak and tire easily. The first symptoms of this condition often involve the eyes. The most common sign of the disease is drooping eyelids in one or both eyes. Other symptoms include double vision, weakness in the arms or legs, or life-threatening problems with breathing, talking, chewing or swallowing.

Rheumatoid arthritis

Ocular signs of rheumatoid arthritis (RA) most commonly include red eyes with deep, severe pain. This symptom can signal scleritis, a painful inflammation of the white part of the eye which requires medical therapy. Dry eye can also be caused by RA. 

Sarcoidosis

This inflammatory disease affects multiple organs the body, including the eyes. The most common eye symptom of this disease is iritis, a recurring, painful inflammation of the iris or colored part of the eye. This condition also causes severe light sensitivity.

Sexually transmitted diseases

Syphilis, herpes, chlamydia, HIV, gonorrhea, genital warts and pubic lice can all affect layers of the eye. These serious conditions are often detected during an eye exam.

Sickle cell disease

People with sickle cell disease, a genetic blood disorder, develop stiff, comma-shaped red blood cells that can block the flow of blood throughout the body. This disease can cause a huge spectrum of ocular changes, from redness and burst blood vessels on the surface of the eye to severe hemorrhages and even retinal detachment inside the eye.

Sjögren's syndrome

This autoimmune disease causes the body's white blood cells to attack the glands that make tears and saliva. Unsurprisingly, dry eyes are a key feature of Sjögren's syndrome. Burning or stinging in the eyes, blurry vision and dry mouth are other symptoms can be seen. 

Stroke

Blood vessels of the retina sometimes contain blockages or clots. These blockages can cause sudden blind spots or give the sense of a "curtain" closing over a person's vision. These signs can point to an increased risk for stroke. A loss of side vison may also be a warning of brain damage caused by a previous stroke.

Thyroid disease

Protruding eyeballs and retracting eyelids are telltale signs of hyperthyroidism, most commonly caused by Graves' Disease. This happens when the thyroid gland produces too much or too little hormone. Sometimes this coincides with dry eye, blurry vision or vision loss.

Vascular disease

Clotting disorders and bleeding disorders may cause visible bleeding in and around the eye. These are known as subconjuctival hemorrhages. These disorders can also cause retinal hemorrhages that threaten vision.

Vitamin A deficiency

Dry eyes and night blindness are both signs of Vitamin A deficiency. Without enough vitamin A, your eyes cannot produce enough moisture to keep them properly lubricated. Night blindness, by preventing production of certain pigments needed for your retina to work properly can be caused by low levels of vitamin A. Vitamin A deficiency is the leading cause of preventable blindness in children worldwide.

It's important to remember that these symptoms don't guarantee you have a certain health condition. Whenever an eye exam reveals a possible health problem, your ophthalmologist will recommend further testing by a specialist or your primary care provider.

The American Academy of Ophthalmology recommends that all adults get a complete eye examination at age 40. This is when early signs of disease or changes in vision may first appear. If you have risk factors such as diabetes, high blood pressure or a family history of eye disease, don't delay — schedule an eye exam at an earlier age.