Sudden Inability To Focus Eyes: Identifying Causes Of Acute Diplopia

Diplopia, also called “double vision,” can be alarming for patients of all types. Double or sudden blurred vision does not have a single cause. A range of health conditions, some more serious than others, are linked to the sudden inability to focus the eyes.

Learning more about diplopia, and the variety of conditions that cause it, allows patients to select the best treatment option to prevent further vision loss and negative health effects.

Diplopia (double vision) is seeing two identical images at the same time. These identical images may appear vertically, horizontally, or diagonally. Patients may also develop diplopia in one or both eyes.

The causes and severity of diplopia can vary greatly. The underlying cause of double vision plays a hand in the gravity of the condition. For instance diplopia caused by a refractive error such as astigmatism is less severe then diplopia caused by a potentially serious health condition like diabetes.

There are two primary types of diplopia:

Monocular diplopia: This occurs when a patient experiences double vision with only one eye open. In this form of the condition, the second image appears as a “ghost.”

In general, the causes are more benign and less likely to be caused by serious neurological problems.

Binocular diplopia: This form of diplopia occurs when a patient only has double vision when both eyes are open. Binocular diplopia is often more severe, and may have serious neurological causes.

While the primary symptom of diplopia is double vision, patients with the condition may experience a range of other symptoms including:

• One or both eyes not lining up—giving patients a “wandering” or cross-eyed look

• Pain when moving eyes

• Sudden inability to focus the eyes

• Pain in areas around the eye like the temple and eyebrows

• Headaches

• Nausea

• Droopy eyelids

• Weakness in or around the eye

Symptoms will vary by case and depend on the medical condition which is causing double vision to occur.

There are many causes of diplopia. Most are connected to an issue in one or more parts of the eye.

The cornea is the clear window that focuses light in the eye. Issues in the cornea can distort the surface of the eye, leading to double vision.

Corneal conditions that can lead to diplopia include:

• Keratoconus

• Infections like shingles or herpes

• Scars

• Dry eye

The lens is located in the opening of the eye behind the pupil. Its primary function is to focus light onto the retina in the back of the eye.

Cataracts are the most common lens-related problem that can lead to double vision. A cataract is an ocular condition where the lens inside of the eye has become cloudy and hardened over time, allowing less and less light to enter. Patients can often alleviate cataract related diplopia through surgery.

A group of muscles surrounding the eye socket control the movement of the eyes and keep them aligned with one another. Weakness in one or more of these muscles prevents the eyes from moving in sync, which can cause double vision.

Conditions that can affect the eye muscles and cause diplopia include:

• Graves' disease: A thyroid condition that affects eye muscles.

• Strabismus: Also known as “misaligned eyes,” and is caused by a weak or paralyzed eye muscle that prevents alignment.

• Myasthenia gravis: An autoimmune illness where nerves stop communicating with eye muscles and to tell them what to do.

Nerves connect the eyes and the brain and carry important messages which can control eye movements.

Some nerve-related conditions that lead to diplopia include:

• Diabetes: A metabolic disease which alters the body's ability to process blood sugar.

• Multiple sclerosis: A chronic neurological disease which affects the central nervous system and can damage the nerves that control eye movement.

• Guillain-Barre syndrome: A nerve condition which causes muscle weakness. The earliest symptoms appear in the eyes.

• Myasthenia gravis: An autoimmune disease where the immune system attacks nerves involved in eye movement.

Certain parts of the brain help process visual information. This visual information is then transmitted to the eyes. Conditions and injuries that affect these areas of the brain can cause diplopia.

Brain conditions that may cause double vision include:

• Brain aneurysm: A bulging or ballooning blood vessel in the brain.

• Stroke: A blocked artery that cuts off blood flow to areas of the brain.

• Brain tumor: A growth of cells in or around the brain.

• Migraines: A neurological disorder that causes intense headaches and nausea.

• Internal pressure: Pressure inside the skull often caused by an injury or health problem.

• Infection or trauma to the brain: A violent jolt or blow to the brain.

If a patient is experiencing diplopia, or sudden blurry vision, they should immediately schedule an appointment with their eye doctor for a proper diagnosis. The eye doctor will typically perform one or more tests to determine the root cause of the problem, and find an appropriate treatment.

A patient's doctor may ask them to close one eye to determine if the diplopia is binocular or monocular. The doctor may also ask if the double vision is vertical or horizontal to determine which eye muscles are affected.

As the eye doctor gathers more information, they may conduct further tests to determine the underlying condition of a patient’s double vision. Tests will vary depending on what the doctor believes the underlying condition is. Some tests the eye doctor might conduct include blood tests, physical exams, a CT exam, or an MRI.

Once the doctor determines an underlying cause, they may suggest treatment options for diplopia and related symptoms. Treatment options will depend on the cause and severity of the patient's double vision.

For mild cases, doctors may recommend prism lenses to realign the eyes. For more severe cases, patients may require medication or surgery. If diplopia is caused by a more serious medical issue, patients will need to take additional steps to treat that medical condition.