Strabismus is a misalignment of the eyes that occurs as a result of abnormalities in the control of eye muscle movements. The muscles responsible for eye movement ensure the simultaneous movement of the eyes through signals transmitted from the brain. Thanks to normal muscle and eye structure, both eyes focus on the same point at the same time. However, due to certain causes, problems may occur in eye movement. As a result, one eye may turn inward, outward, upward or downward differently from the other. In strabismus, the normal position of the eye cannot be maintained. Although it is most commonly seen in children, strabismus can also occur in adults.
Various diseases, paralysis and physical traumas may be among the causes of eye misalignment. In some cases the same eye turns every time, while in others the eyes may turn alternately. Eye alignment disorders may occur intermittently and may sometimes resolve on their own. However, if treatment is not provided, “amblyopia (lazy eye)” may develop and vision loss may occur.
What Is Strabismus?
Each eyeball is positioned by six extraocular muscles. One of these eye muscles moves the eye to the right and another to the left. The other four muscle groups allow the eyes to rotate at an angle and to look down and up. All eye muscles work together in order to focus on objects or images. Problems occurring in the eye muscles can cause a medical condition called “strabismus,” affecting eye movement and alignment. Strabismus is frequently seen in babies and young children. Strabismus that appears suddenly in older children and adults may indicate an underlying significant problem. Misalignment of the eyes may begin in one eye and, as time progresses, may shift to the other eye. Depending on the direction in which the eyes turn, classification can be made as follows:
Esotropia: Inward turning of the eye
Exotropia: Outward turning of the eye
Hypertropia: Upward turning of the eye
Hypotropia: Downward turning of the eye
In addition, strabismus can be classified according to factors such as whether it is unilateral or bilateral, and whether it is intermittent or constant.
What Are the Symptoms of Strabismus?
Eye crossing or eye deviation can generally be detected through certain symptoms. It may be more likely to occur in babies and children compared to adults. However, with regular check-ups, eye deviation can be diagnosed and early treatment can be provided. The symptoms most commonly appearing as signs of strabismus may include:
Eyes looking in different directions,
Lack of coordination in eye movements,
Double vision,
Impaired depth perception,
Eye strain,
Difficulty reading,
Headache,
Need to tilt or turn the head when looking at an object,
Closing one eye when looking at nearby objects,
Squinting, closing or frequent blinking when looking at distant objects or in bright light.
The listed symptoms may not appear in the same way in everyone. However, untreated strabismus may be accompanied by vision problems.
How Does Strabismus Develop?
In the development of strabismus, weak control of the nerve and muscle structures in the brain that enable eye movements may be held responsible. In addition, problems directly affecting the activity of the eye muscles may be effective. Genetic factors, and therefore family history, may also be an important factor. When eye deviation is present, the medical history of family members may be taken into consideration. Risk factors that can lead to eye alignment problems may generally include:
Neurological (nervous system) disorders,
Uncorrected refractive errors,
Down syndrome,
Hydrocephalus,
Head and eye injuries/traumas,
Graves’ disease,
Visual impairment in the eyes,
Brain tumor,
Cerebral palsy,
Stroke.
In infants younger than 6 months, significant inward turning of both eyes may occur. It may occur occasionally in the early period and become constant after a while. Treatment of strabismus in infants may require eye drops, eye patches, surgery and glasses. Furthermore, in some infants the eyes may appear crossed even though there is no strabismus. This condition is called pseudostrabismus, i.e., “Pseudostrabismus.” In infants, pseudostrabismus may be seen due to excess skin covering the inner corners of the eyes or a flat bridge of the nose. This condition usually disappears as the baby grows.
How Is Strabismus Diagnosed?
In babies, children and adults, a comprehensive eye examination, medical and family history, and various additional tests may be used to diagnose strabismus. A detailed examination of the eyes’ focusing ability and range of movement, as well as of the health of the nervous system, may be necessary. The techniques and tests used in diagnosis are mainly the following:
Family and patient history: Evaluation of current symptoms, medications used, surgical history, disease history, environmental factors and family history are important elements in diagnosis.
Refraction test: An examination aimed at evaluating the eye’s ability to focus light and refractive errors. Using a phoropter, a series of lenses placed in front of the eye, and a lighted retinoscope, it can be measured how light is refracted and focused in the eye.
Visual acuity test: A test used to measure how much visual functions are affected in the presence of eye deviation. It involves reading large and small letters from specific distances.
Focusing and alignment test: Tests used to evaluate whether the eyes work together in harmony and their ability to focus. The test helps detect factors that prevent the eyes from focusing or make coordinated work difficult.
At the same time, the inner and outer tissues of the eye may be examined in order to diagnose or rule out various eye diseases. During this process, your doctor may apply certain eye drops.
How Is Strabismus Treated?
When eye deviation is diagnosed early, it can be corrected with an appropriate treatment plan. A treatment plan may involve the use of one or more methods. In these cases, the preferred strabismus treatment methods for improving eye deviation and coordination are as follows:
Contact lenses and glasses: If there are refractive errors in the eyes and mild strabismus, focusing can be corrected with lenses. Glasses may be preferred for strabismus as well as for refractive and focusing problems.
Prism lenses: Prism lenses may help reduce double vision by changing the angle of the light entering the eye. In some cases, lenses may eliminate eye turning.
Medication therapy: Eye ointments, drops or injections may help bring overactive eye muscles under control. These medications may be applied together with surgery.
Eye exercises: A plan that involves visual activity and provides eye coordination. It enables the strengthening of the neuromuscular connection by stimulating the brain to function effectively together with the eyes.
Strabismus surgery: Strabismus surgery consists of procedures involving the repositioning and adjustment of the length of the eye muscles. It is performed under general anesthesia, and vision therapy may be needed after strabismus surgery. Risks of strabismus surgery may include infection, bleeding, diplopia (double vision) and retinal tear.
Frequently Asked Questions
Alignment problems can occur in newborns and babies. However, in some cases this condition may manifest as “pseudostrabismus.” Nevertheless, eye deviation may develop in children and adults as well. Strabismus, which frequently affects babies and young children, may occur in adults due to various causes. Errors or deviations in eye alignment may cause changes in the perception of distance and proximity, misinterpretation of depth perception, double vision and eye strain. These symptoms may lead to loss of balance and may result in falls, collisions and similar accidents. To ensure early diagnosis and treatment of vision problems, be sure to consult a relevant healthcare institution. Misaligned eyes send two different image signals to the brain. Double vision may occur as a result of the different images coming from both eyes. However, in children, the image from the misaligned eye may be suppressed in the brain. This may only require using the image of the straight and better-seeing eye. Therefore, in children, the information about nearness and distance, known as depth perception, may be misinterpreted. Strabismus occurs when the eyes do not work together and do not look in the same direction. This may also be called eye deviation. The eye may drift inward, outward, upward or downward. In this context, strabismus and eye deviation may be used to describe the same medical condition. Not wearing glasses alone may not be a cause of strabismus. However, not using the glasses recommended by the doctor during the treatment process may bring some problems. Not wearing glasses may lead to progression of eye deviation and lazy eye. The reason is that lenses and glasses specific to eye deviation are prescribed within the scope of strabismus treatment. These lenses may help the eye align and alleviate lazy eye. Prism glasses with special lenses may be used in strabismus treatment. These special lenses are designed to correct the double vision problem by bending light. They are transparent, thick and wedge-shaped. Prism glass lenses may be preferred by being fitted into glasses. Glasses may help the eye remain in a straight position. Surgical interventions may have disadvantages, called complications, alongside their advantages. Complications may not occur in every individual and may not be seen with the same severity. Prevention of complications depends on postoperative care. Risks of strabismus surgery include: infection, bleeding, double vision, allergy to medications and anesthesia, and eyelid drooping. In addition, recurrent misalignment may occur. Strabismus surgery may last approximately thirty minutes to 2 hours. Operation duration may vary depending on the technique and devices used. You may need to rest for about a week after surgery. During the healing process, eye drops, ointments or glasses prescribed by the doctor should be used carefully. Strabismus surgery consists of procedures that change the placement and length of the muscles that move the eye. Surgery is one of the effective methods used to correct strabismus. Using glasses for a period after surgery may be recommended. However, clear vision may not be achieved during the healing period and double vision may be experienced for a few days. In some cases, this period may be longer. When diagnosing strabismus, the medical histories of the mother, father and siblings should be evaluated. Although not always, genetic factors may be effective in the emergence of this condition. Particularly in individuals with strabismus in the family, the likelihood of this condition appearing may be higher. Regular eye check-ups for babies should be ensured, especially in the first six months and at later ages. In diagnosing strabismus in babies, eyeball misalignment and imbalance, and pseudo eye deviation are the first findings to be evaluated. However, misalignment exceeding fifteen degrees and lasting more than three months is accepted as abnormal. In addition, the tests used for diagnosis in babies are the light reflex test, red reflex test, and cover and uncover test. In the light reflex test, the eye alignment of babies who follow a light directed by a specialist from a distance of one meter is examined and compared. In the red reflex test, the red reflex of both eyes is visualized with the help of an ophthalmoscope. The results should be the same. In the cover test, one of the child’s eyes is covered and the child’s focus on a specific target (light, toy, etc.) is observed; this is then repeated for the other eye. In the uncover test, one of the child’s eyes is covered for five seconds and the child is made to focus on the target. The covered eye is then quickly uncovered and the alignment of the eye is closely examined. An eye in an abnormal position may show deviation. Do not neglect the necessary follow-up and check-ups for the protection and maintenance of your eye and neuromuscular health. If you suspect strabismus, you can prevent complaints you may encounter due to strabismus by seeking support from an eye disease specialist.
