Strabismus or cross eye is a medical condition in which the alignment of the eyes is not proper, which gives a sense that both the eyes are not focusing together rather are focusing in different directions. Strabismus or cross eye may appear in many forms like when one eye looks up and the other looks down or while one eye looks in, the other looks out. The condition may either appear all the time or sometimes, in scenarios when an individual is suffering from some kind of illness or is distressed.
What is Strabismus or Cross Eye?
Strabismus or cross eye occurs when the muscle control over the eyes is weak, which further causes the eyes to look in different directions.
The eye is supported by six different muscles, which receive signal from the brain. These signals are interpreted in terms of movement of the eyes along with the coordination of both the eyes to focus at a same point together. However, there are certain cases when these eye muscles are unable to coordinate appropriate movement of the eyes, thereby resulting in uncoordinated eye movement. A proper vision allows an individual to perceive good depth of the object or person standing in front. In case of strabismus, the person sees everything double, due to separate focus of each eye, thus brain receives different images from each eye which further results in poor vision and confusion.
The reason behind poor vision is the perception of brain which ignores the image from the turned eye which progressively leaves behind reduced vision. This condition is also called lazy eye or amblyopia.
Strabismus or Cross eye is also common in infants and toddlers. Their eyes appear to be misaligned but this is false strabismus or pseudostrasbismus. It is called so because either the nose of the baby is flat around the eyes or the inner corners of the eyes are covered with extra skin. The condition subsides slowly when the size of the face of the baby starts to grow, usually up to three years of age, and it fixes itself. In case, the condition persists then, an optometrist should be consulted.
Types of Strabismus or Cross Eye
There are different types of strabismus, which are categorized on the basis of the direction of the turned eye. These are:
- Small-Angled Misalignment: Condition in which, the misalignment of eyes is quite less.
- Large-Angled Misalignment: Contrary to the small angled misalignment, there exists a significant misalignment in between the eyes. It is of several types depending on the direction of the eye:
- Esotropia: It occurs when one eye turns inwards.
- Exotropia: Exotropia involves outward turning of the eye.
- Hypertropia: When the eye turns upwards then the condition is called hypertropia.
- Hypotropia: In case of hypotropia, the eye turns downwards.
- Duane’s Syndrome: This condition involves difficulty in moving the eyes sideways and retracting them.
Characteristics of Strabismus or Cross Eye
The prominent characteristics of Strabismus are:
- Visibly misaligned eyes
- Presence of double vision
- Impairment of vision
- Loss of perception of depth.
Epidemiology of Strabismus or Cross Eye
According to recent researches, as much as four percent of population possesses strabismus or Cross Eye in some form. It can be both large as well as small angled. Amongst the above population, almost one-third are the cases of children who later develop lazy eye.
Prognosis of Strabismus or Cross Eye
The outlook for strabismus or Cross Eye is good if detected and treated early. In some cases, even after corrective treatment, vision problems may persist and would require regular monitoring. It may further require surgery and a compulsion to wear glasses. When the treatment for strabismus or cross eye is delayed, then it may also result in permanent loss of vision.
Causes of Strabismus or Cross Eye
The muscles that support the eye are called extraocular muscles. These are a set of six muscles which help in attaining the binocular vision. When these extraocular muscles suffer from anatomical or neurological problems, then the brain signals relating to eye movement are not interpreted appropriately. This results in Strabismus or Cross Eye. Other causes behind, strabismus or Cross Eye are eye injuries, familial genetics and other health conditions.
Risk Factors of Strabismus or Cross Eye
The common risk factors that pose a threat of strabismus or cross eye are:
- Prior presence of the condition within the family.
- Presence of a brain condition like a disorder, brain stroke, brain injury or a tumor.
- Damaged retina.
- History of diabetes.
- Existence of farsightedness.
- Pre-term birth.
Complications of Strabismus or Cross Eye
The complications related to Strabismus or Cross Eye usually arise due to strabismus related surgery. The complications that usually occur are:
- Unsatisfactory alignment of the eye.
- Presence of change in refraction of the eye, but it is usually temporary.
- Diplopia or double vision.
- Sclera perforation during the surgery due to involuntary passing of the suture needle deep in the eye. It is indeed a serious complication, which gives way to endopthalmitis.
- Occurrence of infections in the eye after surgery.
- Allergic reactions towards post-surgery medications and surgical suture material.
- Shift in the eyelid position or ptosis.
- Dellen, a thick bulbous formation on cornea or sclera which prevents lubrication in the eye.
- Scarring of conjunctiva.
- Conjunctival cyst.
Diagnosis of Strabismus or Cross Eye
The diagnostic procedure for the diagnosis of strabismus or Cross Eye involves:
- Examination of the Patient’s History: The patient’s history is checked for existing symptoms as well as prior presence of general health issues.
- Visual Acuity Test to Check for Strabismus or Cross Eye: This test is conducted to check the central vision of the eye to assess the extent of vision that has been affected. For normal vision, the test result should be 20/20; any deviation from this value marks a problem in central vision.
- Test for Refraction to Diagnose Strabismus or Cross Eye: This test is conducted to check the presence of refractive errors like nearsightedness, farsightedness or astigmatism. In case, the error exists then the test also determines optimal lens power which is needed to compensate the condition.
- Alignment and Focus Test to Identify Strabismus or Cross Eye: This test checks the accuracy of eyes while focusing on something. It also checks for the coordination between the eyes.
- Analysis of Eye Health: This test is done to rule out the possibility of any underlying eye condition which might contribute to strabismus or cross eye.
Treatment of Strabismus or Cross Eye
The treatments available for strabismus or cross eye are of both types surgical and non-surgical, which aim at improving the alignment and coordination of the eye.
- Non-Surgical Measure for Strabismus or Cross Eye: These include:
- Vision Therapy: It involves following a definitive program which constitutes visual activities that help in reinforcing the appropriate eye movement, focus and coordination.
- Prism Lenses: These types of lenses possess a prism which helps in bending the light entering the eye to such an extent that turning of the eye gets reduced.
- Contact lenses/Spectacles: These advised only in some cases of strabismus or cross eye.
- Eye Surgery to Treat Strabismus or Cross Eye: The eye surgery is opted for severe cases of strabismus or cross eye or the cases that do not respond well to non-surgical treatments. The surgery aims at altering the position and length of extraocular muscles to prevent misalignment of eyes.
Exercises for Strabismus or Cross Eye
Apart from above treatments, there are certain exercises that help in improving the condition of strabismus or cross eye. These are commonly advised during the vision therapy. These include:
- Brock String Exercise for Strabismus or Cross Eye: For this exercise, a five feet long string is taken which contains three beads of different colors. One end of the string is kept stationary while the other end is held tightly in front of the nose. The beads are placed at an equal distance and focused on such that the bead which is focused on appears as the intersection of two identical strings.
- Pencil Pushup Exercise to Correct Strabismus or Cross Eye: These are simple eye workouts which involve focusing of eyes at one fixed point by holding a pencil in front at a distance of arm’s length. Then slowly the pencil is brought near towards the nose. Once the vision starts to blur, the pencil should be taken away from the eye.
- Barrel Cards Exercise to Rectify Strabismus or Cross Eye: This exercise is specifically for extropia, in which three red barrels are drawn lengthwise with progressing size, on one side of a card and same is done with other side but in green color. The card is then held lengthwise against the nose with largest barrel farthest. Then the setup is taken far enough such that the image of the both colors gets doubled. The gaze is done for five seconds and the exercise is then repeated for other barrels.
Can Strabismus or Cross Eye be Prevented?
There are no definitive measures that can prevent the occurrence of strabismus; however, preventing the occurrence of the risk factors can reduce the chances of occurrence of the condition. These include prevention of premature delivery and partially correcting hyperopia.
Strabismus or cross eye is a common condition in which the eyes focus in an uncoordinated manner which leads to their misalignment. The condition is usually treatable and has a good outlook but only in the cases when immediate therapy and treatment is administered. The cases in which therapy does not work well, surgical measures are opted to fix the eye muscles and help in improvement of vision.
- American Association for Pediatric Ophthalmology and Strabismus. What Is Strabismus? https://aapos.org/glossary/strabismus
- American Academy of Ophthalmology. Strabismus (Crossed Eyes). https://www.aao.org/eye-health/diseases/strabismus
- Mayo Clinic. Strabismus (crossed eyes). https://www.mayoclinic.org/diseases-conditions/strabismus/symptoms-causes/syc-20377455
- Cleveland Clinic. Strabismus (Crossed Eyes). https://my.clevelandclinic.org/health/diseases/8591-strabismus-crossed-eyes
- WebMD. Strabismus (Crossed Eyes). https://www.webmd.com/eye-health/strabismus
- American Optometric Association. Strabismus (Crossed Eyes). https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/strabismus
- All About Vision. Strabismus Symptoms, Causes and Treatment. https://www.allaboutvision.com/conditions/strabismus.htm