Diplopia (Double Vision)

Among the most common complaints encountered in eye disease examinations is diplopia, or “double vision” as it is popularly known. Our eyes are actually programmed to work in harmony, like different instruments of an orchestra, providing us with a single, clear image. However, just as the harmony of the music is disrupted if one of the orchestra members—say, the violin—is out of tune, if one or both eyes do not function correctly, the brain may receive two separate images of the same object. This results in diplopia, that is, double vision.

What Is Diplopia (Double Vision)?

Diplopia means perceiving a single object as two separate images. Essentially, it may result from the brain’s inability to fuse images from both eyes (fusion disorder) or from disruptions in the eye’s optical system. To use a more concrete analogy, our eyes each function like a separate camera, and there is an “editor” in the brain who combines these “two separate shots” into a single image. If this editor cannot overlay the two recordings correctly—for instance, due to a technical malfunction or synchronization error—two different images appear on the screen. A person’s visual quality and daily life can be seriously affected by this situation.

What Are the Types of Diplopia?

What Is Monocular Diplopia?

Monocular diplopia occurs when double vision continues with one eye open and persists when the other eye is closed. That is, if you keep your right eye closed and continue to experience double vision with your left eye (or vice versa), it indicates monocular diplopia. In monocular diplopia, the problem generally arises from the eye’s own structural or optical defects. For example, if there is a refractive error such as astigmatism in the eye, the incoming light rays may form more than one focal point on the retina. In that case, one might encounter double vision described as “blurry image or a shadow image.”

Similarly, in conditions such as cataracts (loss of clarity in the lens) or keratoconus (thinning and conical deformation of the cornea), incorrect refraction of light can lead to monocular diplopia. We might compare these examples to a camera lens defect; if there are scratches or distortions on the lens, the single lens itself creates two different focuses, and the single object you photograph appears duplicated.

What Is Binocular Diplopia?

Binocular diplopia, on the other hand, is when double vision is experienced while both eyes are open, and it disappears when one eye is closed. In other words, both cameras continue recording, but the brain cannot properly combine these two images. This type of diplopia is usually related to a problem affecting the eye muscles or their coordinated movement. Strabismus (eye misalignment) is one of the most well-known causes of binocular diplopia. One eye may deviate inward, outward, upward, or downward, and because the visual axes are not parallel, two different perspectives result, and the brain cannot superimpose them.

Sometimes neurological causes, for instance cranial nerve palsies (involving cranial nerves III, IV, or VI), lead to binocular diplopia. Simply put, if one of the nerves controlling the eye muscles is damaged, that eye may not rotate sufficiently or position itself correctly. Depending on the direction of gaze, the person frequently describes horizontal, vertical, or even oblique double images. It is as if the same scene is filmed from two different angles that cannot be overlapped.

How Does Monocular Diplopia Occur?

Factors contributing to monocular diplopia generally stem from disruption of the eye’s own “optical axis” (the pathway through which light enters and reaches the retina). These can be summarized as follows:

Refractive Errors:

• Astigmatism: The asymmetric curvature of the cornea or lens distributes light rays to multiple focal points rather than focusing them on a single point.
• High Myopia or Hyperopia: In some cases, very high levels of refractive error can also cause shadowy or double images through focus errors.

Corneal Problems:

• Keratoconus: The cornea becomes thinner and more cone-shaped, causing severe astigmatism and potentially leading to monocular diplopia.
• Corneal Scars: Opacities or surface irregularities in the cornea following infection, trauma, or surgery prevent proper refraction of light.

Lens Conditions:

• Cataracts: A lens that has lost its transparency may refract light in a scattered manner, making a single object appear as if doubled.
• Lens Subluxation (Displacement of the Lens): Owing to trauma or connective tissue disorders, the normal position of the lens is disturbed, leading to irregular refraction of light.

Retinal and Macular Diseases:

• Macular Degeneration: When the retina’s center fails to receive a clear image, the brain may sometimes interpret the incoming light signals as duplicates.
• Epiretinal Membrane: Thin membranes forming on the retina, especially in the foveal area (responsible for sharp vision), can cause distorted vision.

When such conditions are suspected, the first step is to thoroughly evaluate all components of the eye’s optical system (cornea, lens, retina). A detailed examination using a biomicroscope, optical coherence tomography (OCT), or corneal topography can be extremely helpful in detecting the site of abnormality. The key factor in monocular diplopia is that double vision continues when the other eye is closed. Accordingly, a simple “Cover Test” at the outset is quite helpful for diagnosis.

Under What Circumstances Does Binocular Diplopia Develop?

The fundamental dynamic of binocular diplopia is the inability of the extraocular muscles to work in harmony or the loss of “parallel alignment” of the eyes. In most cases, there is an imbalance of neurological or musculoskeletal origin. Here are the most common causes:

• Strabismus (Eye Misalignment):

Eye deviation may be present from childhood (congenital) or can occur in later life due to various traumas or neurological disorders leading to eye muscle weakness, nerve palsy, or laxity of the muscle tendons.

• Cranial Nerve Palsies:

Third Nerve Palsy (Oculomotor Palsy): Drooping of the eyelid (ptosis) and an outward/downward position of the eye may appear; patients commonly experience double vision.

1. Fourth Nerve Palsy (Trochlear Palsy): Vertical diplopia is especially noticeable when descending stairs or reading a book. The head is often tilted (compensatory head position).
2. Sixth Nerve Palsy (Abducens Palsy): If the eye cannot move outward, the patient experiences horizontal double vision.

• Myasthenia Gravis:

In this autoimmune disease, muscle contraction strength decreases over the course of the day. While vision may be better in the morning, eyelid drooping and double vision become more pronounced by evening. It is as if the body’s energy reserves are depleted, and the eye muscles become fatigued.

• Goiter/Graves’ Disease (Thyroid Ophthalmopathy):

Due to hyperactivity of the thyroid gland, tissues and muscles around the eyes can swell, pushing the eyeballs forward and creating a strabismus-like picture. When alignment is compromised, diplopia appears.

• Orbital Masses or Trauma:

Tumors, infections, or fractures in the orbit can mechanically obstruct free movement of the eye or displace the eyeball, causing double vision.

• Neurological Diseases (Multiple Sclerosis, Stroke, etc.):

Lesions in the brainstem or other areas that control eye movements (e.g., lesions in brainstem structures or MLF syndrome) can lead to diplopia.

Each of these causes can present with varying degrees and directions of double vision. Neurological examinations, visual field tests, or cranial MRI may be ordered to clarify the diagnosis. In binocular diplopia, closing one eye restores normal vision—this is the most distinguishing feature.

What Symptoms Accompany Diplopia?

A person complaining of diplopia may not just say “I see double.” The following symptoms may also appear:

• Headaches and Eye Fatigue: When the brain struggles to fuse two misaligned images, the person may experience intense headaches and a feeling of pressure around the eyes.
• Visual Confusion and Difficulty: Misperception of object positions disrupts the sense of distance and depth. This can be dangerous when descending stairs or driving.
• Difficulty Keeping Track of Lines While Reading: Letters may overlap; reading becomes highly tiring, and concentration suffers.
• Changes in Head Position: Particularly in vertical diplopia, the person may unconsciously tilt their head sideways or forward to reduce the double vision.

If you see “two lamps, two car headlights, or two human faces” and it reduces your quality of life, you should definitely consult a specialist.

What Diseases Underlie Diplopia?

Diplopia can be merely a symptom and can act as a warning sign of more serious conditions. For example:

• Diabetes: Microvascular disease can lead to temporary palsies of cranial nerves III, IV, or VI.
• Hypertension: High blood pressure similarly affects small vessels supplying the nerves, damaging the eye nerves.
• Aneurysm or Brain Tumors: They may compress areas in the brainstem or near cranial nerves, causing diplopia.
• Multiple Sclerosis (MS): In demyelinating conditions of the central nervous system, such as MS, specific conditions like internuclear ophthalmoplegia can lead to diplopia.
• Thyroid Diseases: Disorders like Graves’ disease can involve the eye muscles and connective tissue, causing swelling and double vision.

Like a bomb placed in a building’s foundation, diplopia may start with very minor signals. Ignoring these can lead to missing subsequent complications. Therefore, if diplopia is accompanied by other symptoms (sudden vision loss, speech disorder, balance problems, etc.), seeking medical help is crucial.

How Is Diplopia Diagnosed?

Many methods are used in diagnosing diplopia, but the first and most important step is taking a thorough patient history. An ophthalmologist or neurologist will try to learn in detail when the diplopia began, what circumstances increase or reduce it, and whether there is a history of trauma or systemic illness.

• Cover Test: Helps to determine if it is monocular or binocular.
• Eye Movement Examination: The performance of the eye in all directions of gaze is assessed; any limitation of muscles or nerves is noted.
• Cover-Uncover Test and Alternate Cover Test: Used to detect latent misalignment (heterophoria) or manifest misalignment (heterotropia) between the eyes.
• Prism Tests: Prism lenses are used to measure the degree of double vision and the direction and magnitude of eye deviation.
• Biomicroscopy and Fundoscopy: The anterior segment of the eye (cornea, iris, lens) and the posterior segment (retina, optic nerve) are examined in detail.
• Radiological Examinations (MRI, CT): If there is suspicion involving the nervous system or the orbital region, brain imaging is requested.
• Blood Tests: Look for signs of systemic illnesses such as diabetes or thyroid disorders.
• Electrophysiological Tests: In conditions like myasthenia gravis, examinations such as EMG can provide guidance.

Just as an engineer needs diverse measurements to understand a building’s structural balance, the ophthalmologist requires multifaceted data to find the source of diplopia.

What Treatment Methods Are Available?

Treatment for diplopia depends entirely on the underlying cause. Let’s look at the commonly used approaches:

Correctable Refractive Errors:

• Glasses or contact lenses can correct problems like astigmatism, myopia, and hyperopia. Some patients with monocular diplopia can find relief simply with proper eyeglasses.
• Rigid or specially designed lenses can minimize distortions caused by corneal diseases like keratoconus.

Prism Glasses (Prismatic Correction):

• In binocular diplopia, if the axis misalignment is mild and doesn’t require surgery, prism glasses may be suitable.
• Temporary solutions such as Fresnel prisms are often used when nerve palsies are newly developing, as the nerve may recover over months.

Occlusion Therapy (Patching):

• Temporarily covering one eye is the surest way to prevent double vision, but depth perception is lost in daily life.
• In children at risk of amblyopia, the doctor applies this method with a specific plan.

Surgical Interventions:

• Strabismus surgeries can realign the position of the eye muscles, restoring coordinated alignment.
• Orbital surgeries (for tumors, trauma, thyroid ophthalmopathy) aim to correct mechanical or volumetric issues.

Botulinum Toxin Applications:

• Temporarily blocks excessive muscle activity. For instance, in sixth nerve palsy, botulinum toxin can be injected into the lateral rectus muscle to compensate for the eye being turned inward.
• The effect lasts for a few months, sometimes allowing partial nerve recovery in the meantime.

Treating Underlying Systemic Diseases:

• Conditions like diabetes and hypertension must be brought under control.
• Medications for myasthenia gravis (e.g., pyridostigmine) and immunosuppressive therapies can reduce muscle weakness leading to diplopia.
• In thyroid disorders, treatments to balance hormone levels and reduce orbital pressure (e.g., corticosteroids) or surgery may be considered.

Rehabilitation and Orthotics:

• Vision therapy or orthoptic exercises can be beneficial, especially for convergence insufficiency.
• Computer programs and special exercise charts are used to improve coordination of the eye muscles.

Treating diplopia is somewhat like carpentry; once you identify which piece is bent, which screw is loose, or which board is rotten, you make the appropriate correction. Sometimes just tightening one loose screw solves the problem; other times the entire structure must be overhauled.

When Should You Seek Urgent Medical Attention?

Diplopia is not always an emergency; however, it is crucial to visit a healthcare facility without delay in the following circumstances:

• Sudden Onset of Double Vision: If you suddenly notice double vision upon waking up or if it develops very quickly, it may be due to conditions requiring urgent intervention, such as brain vascular diseases or nerve compression.
• Severe Headache, Speech Difficulties, and Weakness in the Body: A stroke (paralysis) should be suspected.
• Severe Eye Pain and Redness: Could be due to infections or an acute glaucoma attack.
• Double Vision After Trauma: A blow to the head, orbital fractures, or concussion may require emergency evaluation.

A patient with trauma or sudden-onset double vision who thinks “I’ll wait a bit, maybe it will go away” may face irreparable harm later on.

How Does Diplopia Affect Daily Life?

Double vision significantly impairs a person’s quality of life and daily functioning. Even seemingly simple daily activities become a major challenge:

• Driving: Seeing oncoming car headlights or traffic lights doubled can increase the risk of accidents.
• Using Stairs: Those with vertical or oblique diplopia particularly struggle due to impaired depth perception.
• Reading and Computer Use: Seeing overlapping lines causes rapid eye fatigue and headaches.
• Social Interaction: Seeing two images of a person’s face or finding it hard to maintain eye contact can disrupt interpersonal relations.
• Psychological Effects: Individuals with long-term diplopia may be more prone to depression or anxiety and may withdraw from social settings.

Many patients develop their own strategies to cope with diplopia, such as tilting the head, partially closing one eye, or avoiding bright light. However, these behaviors can cause neck pain and permanent posture problems.

Which Specialists Should One Consult for the Diagnosis and Treatment of Diplopia?

The first point of contact is usually an ophthalmologist (eye specialist). The eye doctor conducts initial screening to determine whether the diplopia stems from an ocular cause or a neurological/systemic problem. If a neurological cause is suspected, a neurology specialist is consulted for brain imaging and neurological tests. If necessary, other specialties such as endocrinology and internal medicine collaborate to solve the underlying cause.

Conclusion and Recommendations

Diplopia (double vision) can be an important clue for both eye health and general health. It could be resolved in a few minutes with a simple correction of an astigmatic error, or it could be a sign of a serious condition like an aneurysm in the brain’s blood vessels. That’s why it is crucial not to take diplopia lightly and to seek expert opinion.

• Have Regular Eye Examinations: Especially if you have systemic issues like diabetes, hypertension, or thyroid disease, seeing an eye doctor at least once a year is beneficial.
• Early Diagnosis Can Be Life-Saving: If sudden double vision is accompanied by severe headache, speech difficulty, or body weakness, seeking immediate medical help can save time in managing life-threatening conditions like stroke.
• Follow Your Treatment Plan: If prism glasses, botulinum toxin injections, or surgery are recommended, adhere to these diligently. Each treatment has its own success rate and possible side effects.
• Rest Your Eyes and Exercise Them: For mild cases of diplopia, eye exercises or taking regular breaks during work/reading can be beneficial.
• Don’t Skip Follow-ups and Check-ups: Diplopia may worsen over time, or it may improve spontaneously (e.g., minor nerve palsies). Therefore, maintaining regular control examinations and updating treatments when necessary is important.

Remember, the eyes are one of the primary gateways through which our body connects with the outside world. Any problem in this gateway directly impacts our quality of life. If you notice an unusual change like double vision, see a specialist. An informed approach, along with early diagnosis and proper treatment, can largely alleviate the difficulties caused by diplopia.

When experiencing double vision (diplopia), one should treat the eyes with the same care as when a weak tooth needs extraction or a cavity needs filling: do not neglect them, but rather address the issue thoroughly and follow your doctor’s instructions precisely. Ultimately, providing the brain—our central “director”—with the highest quality “broadcast” possible is an indispensable part of a healthy life.