Double Vision – Seeing Double – Causes of Diplopia

What is Diplopia?

Diplopia is also known as Double Vision. It occurs when an individual sees 2 or more images of the same object. Diplopia is different from the blurred vision where a single object appears to be unclear.

The vision in humans is single Binocular vision. This means that the images from both the Eyes are recorded and processed by the Nervous System but it makes a single image. An interruption in this process can make a double vision.

The double vision may be present in 1 Eye known as Monocular or 2 images can be made from both the Eyes together known as Binocular.

Physiological Diplopia

Diplopia can be a normal phenomenon, for example, when focusing on an object that that is close up, another object in the distance can appear double. This is known as Physiological Diplopia. It is generally not noticed because the Brain has the power to suppress these double images.

Normal Vision

The Eye is a complex part of the body that consists of the Visual receptors, a Lens system to focus the Light on the receptors and the Nerves to take the Visual information to the Brain.

At the front of the Eye, there is a Cornea which allows the Light through the Retina. Retina is layer that covers the back of the Eye, which is composed of the Cells known as Rods, Cones and the Nerve Cells.

The Rods and the Cones are the Visual receptors of an Eye. They contain Photosensitive Cells that directly communicate to the Nerve Cells. There is a Lens present between the Cornea and the Retina. The Lens focuses the light coming through the Cornea and forms an image on the Retina.

When light falls on the Retina, the Rods and the Cones React to Light to generate the massage to the Nerve Cells. The Electrical signals or the Impulses travel through the Optic Nerve to the Visual Cortex in the Brain. The impulses from each Eye or 2 Images are fused into a single image. The humans are able to move each Eye with the use of 6 different Muscles that are present on the outside of the Eyeball. These muscles are controlled by the impulses from 3 Cranial Nerves. The Nerves and the muscles together control the Eye movements to keep both of the Eyes pointing correctly at the same object.

A Bony casing in the Skull is present to protect the Eye known as Orbit. This casing has an Aperture at the to allow the Cranial and Visual Nerves to pass the information between the Eyes and the Brain.

Pathophysiology of Diplopia

The damage to any part of the body like system, the Eye, Muscles, Nerves, surrounding parts of the structure and the parts of the Brain that process the visual information can lead to the Diplopia.

The damage to the Eye muscles or the Nerves that supply the Blood to the Eye muscles can result in the bad co-ordination of the Eye movements, visual axis etc. In this case the vision will not be same for both of the Eyes and it can cause Diplopia. Any disease to the structure of the Eye trough Trauma etc will also cause double vision.

Causes of Diplopia

Diplopia can be a sign of the serious disease and it should be checked by a doctor as soon as possible. The Alcohol or drug intoxication is not related to this disease.

Following can be the Causes of Diplopia

1. Monocular Diplopia

   Symptoms

   The Monocular originates form the problem within the Eye and the Double Vision is caused when the unaffected Eye is covered.

   The 2 images appear; this phenomenon is also known as ghosting. Most of the time, the cause of the Diplopia is a Refractive Error. This happens when the Light rays are not focused on Retina by the Lens and these symptoms can be treated by looking trough a Pinhole.

   Causes of the Diplopia

   Opening the Eyes and seeing single, clear image is something that we take for granted but this is an automatic process that depends on the Orchestration of multiple areas of the Vision system.
   
   The Causes of the Diplopia may include
   Cataract
   

   • Dislocation of the Lens
   • Corneal problems
   • Corneal scarring
   • Degeneration of the Muscular part of the Retina
   • Astigmatism

2. Binocular Diplopia

   It is related to the abnormal alignment of the Eyes. In this case the symptoms of Double vision are treated when1 Eye is covered.

3. Strabismus

   In Strabismus or Squint, the Alignment of the Visual Axis is impaired that results in the Double Vision.

   In children, it may result from the Prenatal Infections, Genetic Problems, Brain Disorders, injuries and Degeneration conditions.

   In adults, the Strabismus may cause due to the Stroke, Trauma, Poisoning and Neuropathy.Neuropathy is the Nerve damage.

4. Trauma

   A waft to the Face can fracture the Orbit causing swelling around the Eye and the Ocular Muscles. It results in the Diplopia. Double Vision may occur due to the Hematoma.

The Trauma can also cause the following systemic illness

Systemic Illness

1. Multiple Sclerosis

   Symptoms

   • Loss of concentration and memory
   • Decrease in balance
   • Decrease in coordination
   • Decrease in sensations
   • Numbness
   • Parestheisa

2. Myasthenia Gravis

   Symptoms

   • Drooping of the Eyelid
   • Slurred Speech
   • Muscle weakness

   These symptoms can resolve by taking rest.

3. Diabetes Mellitus

   It is also known as the Sugar Diabetes.

4. Hyperthyroidism

   It is also known as the Grave’s disease.

5. The blur vision can be a result of Osmotic changes that may occur in the Lens. The Lens need to be differentiated from the Diplopia. This condition can occur due to Nerve damage or Microvascular damage.
   

   Symptoms

   The symptoms can be Protrusion of the Eyeball, Eye pain, Light sensitivity, Enlarged Thyroid Gland and Weight Loss.

6. Inflammatory

   It is the Infectious or Non-Infectious inflammation felt in and around or in the related structures of the Eye. This Inflammation may not be due to the Trauma.

   It may also include

   • Sinusitis
   • Orbital Cellulitis
   • Exposure to chemicals
   • Optic Neuritis
   • Cavernous Sinus Thrombosis
   • Autoimmune diseases

7. Vascular

   The disruption in the vascular supply to the Brain due to the Stroke or in the Retina of the Eye due to the Diabetes and Hypertension may cause Diplopia.

   A swollen Blood Vessel in the Brain squeezes the Cranial Nerves which controls the Eye movement and hence cause the double vision.

8. Tumours

   The Tumors or Malignant can also cause Diplopia either by effecting the movement of the Eye, squeezing Nerves or applying pressure to the Visual Cortex of the Brain.

   This is seen in the Paranasal Sinus Tumors or due to the Tumors in the Orbit or near the Skull.

9. Nerve Palsy

   Disruption in the Nerve impulses of the Cranial Nerves will affect the movement of the Eye. These nerves supply the Eye muscles. This will affect the alignment of the Eyes and can cause double vision.

   The people who are suffers from the Diplopia can explain that seeing a single image is a blessing but we do not realize this blessing.