Definition

Diplopia, or double vision, is a symptom where a person sees two images at the same time. It is not a disease itself but rather a symptom of another underlying condition. Identifying and treating the cause of diplopia can restore vision and prevent its recurrence.

Diplopia can be classified into two types: monocular and binocular diplopia. To differentiate between them, a simple test can be done. If the double vision disappears when one eye is closed, the condition is binocular diplopia. If it persists when one eye is closed but disappears when the "sick" eye is closed, it is monocular diplopia. Monocular diplopia is caused by a problem in one eye, while binocular diplopia is due to problems in the brain or the nerves that control eye movement. Once the type of diplopia is identified, the doctor will investigate the underlying cause.

Diplopia is a common complaint in both outpatient and emergency settings. In the United States, there are approximately 805,000 outpatient cases and 50,000 emergency cases of diplopia each year. While diplopia can cause significant concern, only 16% of cases are associated with life-threatening conditions.

Causes

Diplopia can be caused by various conditions affecting the eye, lens, muscles, nerves, or brain.

• In cornea-related diseases, conditions such as cataracts, keratoconus, infection, injury, and dry eyes can lead to diplopia.
• In muscle-related diseases, diplopia may be due to immune diseases like Myasthenia gravis and Graves' disease, which affect the eye muscles.
• In nervous system-related diseases, conditions such as multiple sclerosis, Guillain-Barré syndrome, and diabetes can interfere with vision, potentially causing diplopia.
• In brain-related diseases, stroke, aneurysm, tumor, head trauma, and migraine are brain-related causes of diplopia.

Monocular Diplopia

Monocular diplopia originates in one eye and is less common than binocular diplopia. Patients typically describe seeing a clear image accompanied by a blurrier one. Causes include:

• Severe astigmatism: caused by irregular corneal curvature, leading to blurred and double vision.
• Keratoconus: eye vision problems develop when the cornea thins and bulges forward. This protrusion can produce double vision, blurry vision, and pain when exposed to light (photosensitivity). Corneal edema, or injury and swelling, can also cause vision abnormalities.
• Cataracts: the lens of your eye should be transparent; nevertheless, in the presence of cataracts, it becomes cloudy. Double vision and blurred eyes can result from these changes.
• Dry eyes: your eyes are continually producing tears to keep them moisturized. If your tears stop or their production is disrupted, you will experience a burning sensation, itching, and visual changes.
• Pterygium: an abnormal white membrane on the eye can cause vision changes.

Binocular Diplopia

Binocular diplopia occurs when double vision persists even after one eye is closed. It is caused by:

• Nerve damage: inflammation of the optic nerve, which connects the eye to the brain.
• Diabetes: damage the optic nerve, leading to visual impairments, including diplopia.
• Nerve paralysis: paralysis of the cranial nerves that control eye movements, often due to diabetes or high blood pressure.
• Myasthenia gravis: an immune disorder that disrupts communication between nerves and muscles, causing eye fatigue and double vision.
• Graves' disease: an immune system disorder linked to hyperthyroidism, affecting vision in about 30% of cases.
• Strabismus: underlying condition that results in double vision, most commonly in children. The muscles in the eyes experience damage, inhibiting them from working simultaneously. This can result in a number of vision disorders, such as double vision and permanent blindness.

Risk Factor

• Patients over 50 years of age have a higher risk of developing cerebral palsy
• Vascular diseases such as hypertension and diabetes
• Immune disorders, including Myasthenia gravis and Grave's disease
• Severe astigmatism

Symptoms

If you experience diplopia, you may experience the following symptoms:

• Misalignment of one eye (crossed eyes)
• Pain when moving the eyes
• Pain around the eye, such as in the temple or eyebrow
• Headache
• Nausea
• Weakness in the eye or other parts of the body
• Drooping eyelids

Diagnosis

The doctor will first determine whether the diplopia is monocular or binocular. They will inquire about the onset of symptoms, any history of head trauma, the frequency and duration of the diplopia, and whether it affects one or both eyes. The doctor will also conduct visual field and eye movement tests to assess the involvement of the eye muscles.

Further examinations, such as CT scans and MRIs, may be necessary to identify the underlying cause. Additional tests might include a complete blood count, slit-lamp examination, and blood sugar test to assess overall health and potential contributing factors.

Management

Medical Therapy

• Additional lenses, such as fresnel prisms, may be used to correct eye disorders.
• Wearing an eye patch over one eye.
• Orthoptic exercises can help prevent eye fatigue.

Surgery

If diplopia is caused by strabismus or involvement of the eye muscles, surgical intervention may be recommended to correct the alignment of the eyes.

Activity and Follow-Up Evaluation

Avoid driving or operating machinery until your vision returns to normal or you can see clearly with an eye patch on one eye. Regular follow-up with your doctor is essential for ongoing evaluation and management of the condition.

Complications

Diplopia, both monocular and binocular, can cause symptoms such as nausea and vertigo due to impaired vision. Most others experience eye fatigue and sensitivity to light and sound. Other life-threatening conditions, such as infections and brain tumors can lead to double vision, but these symptoms are less common. In children, diplopia can cause amblyopia or lazy eye.

Prevention

While diplopia itself cannot be prevented, some of the underlying causes can be managed. Wearing a seatbelt and protective glasses during activities that pose a risk of eye injury, such as sports or certain work tasks, can help. Controlling blood sugar levels in diabetic patients is crucial to prevent nerve damage that could lead to diplopia.

When to See a Doctor?

Diplopia should be evaluated by a doctor to determine its underlying cause, as it signals a potential problem with the eyes, brain, or nervous system. While many cases of diplopia are treatable, sudden changes in vision require immediate medical attention. Some conditions associated with diplopia can lead to permanent blindness or may be life-threatening. If double vision is accompanied by severe headaches, it is critical to seek urgent medical care.

Looking for more information about other diseases? Click here!