Esotropia is an eye condition where one or both eyes turn inward. This inward turning can be constant or intermittent. It is a type of strabismus, the medical term for eye misalignment. While it can occur at any age, esotropia is most frequently observed in infants and young children, often called “cross-eyed”.
Identifying Esotropia
The primary sign of esotropia is the visible inward turn of one or both eyes. Children with this condition might also exhibit behaviors such as frequent squinting, especially in bright environments, or consistently rubbing one eye. Some individuals may tilt or turn their head in an unusual way to align their vision or reduce double vision. Difficulty with depth perception is another common indicator, as the eyes struggle to work together for 3D vision.
Pseudostrabismus
Parents often become concerned about their infant’s eye alignment, mistaking a normal facial feature for esotropia. Pseudostrabismus, or false crossed eyes, is a common condition in babies where the eyes appear to turn inward but are actually aligned correctly. This illusion often results from a wide nasal bridge or prominent skin folds on the inner eyelids, known as epicanthal folds. These folds can cover the white part of the eye near the nose, creating the appearance of inward deviation.
A healthcare professional can differentiate pseudostrabismus from esotropia through a thorough eye examination. One key method involves observing the corneal light reflex, a reflection of light on the eye’s surface. In pseudostrabismus, this light reflection will appear symmetrically in the center of both pupils, even if the eyes look crossed. In contrast, with esotropia, the light reflection will be off-center in the misaligned eye.
Underlying Causes
Esotropia can stem from various factors affecting eye muscle coordination or the brain’s control over eye movements. Understanding these causes helps guide appropriate management.
Accommodative esotropia is a common form, particularly in children, and is directly linked to uncorrected farsightedness, also known as hyperopia. When a person is farsighted, their eyes must exert extra effort to focus clearly on objects, especially those close up. This excessive focusing effort, called accommodation, is naturally coupled with an inward turning of the eyes, known as accommodative convergence. If the degree of hyperopia is significant, this over-focusing can lead to the eyes crossing inward.
Infantile esotropia, sometimes referred to as congenital esotropia, manifests early in life, typically within the first six months. The precise cause of this type of esotropia remains unknown, though it is thought to involve issues with the brain’s eye movement control development. This condition usually presents as a large, constant inward turn of the eyes and is not associated with significant farsightedness. It can be accompanied by other eye movement issues.
Less common causes of esotropia include abnormalities in eye muscles or issues with nerves that transmit signals to them. For instance, a weakness in the lateral rectus muscle can lead to an inward turn. Neurological conditions, such as cerebral palsy, hydrocephalus, or certain brain tumors, can also disrupt the brain pathways controlling eye alignment, resulting in esotropia.
Professional Diagnosis and Treatment
Diagnosing esotropia involves a comprehensive eye examination performed by an eye care specialist, such as an ophthalmologist or optometrist. The examination typically includes several tests designed to assess visual acuity, how the eyes focus light, and their alignment and movement. A key diagnostic tool is the cover test, where the doctor covers one eye and observes the movement of the other eye to detect any misalignment.
Another important diagnostic step is a refraction exam, often performed with pupil-dilating eye drops. This test helps determine the extent of any farsightedness (hyperopia) and allows the doctor to prescribe corrective lenses accurately. By temporarily relaxing the eye’s focusing muscles, the true refractive error can be measured, which is especially relevant for diagnosing accommodative esotropia.
Treatment for esotropia is tailored to the specific type and underlying cause, with the goals of achieving proper eye alignment and good vision in both eyes. For accommodative esotropia, eyeglasses are frequently the first line of treatment. These glasses correct the underlying farsightedness, reducing the need for the eyes to over-focus and thus helping them straighten. Consistent wear of the prescribed eyeglasses is important for maintaining alignment.
Eye patching is another common treatment, particularly when amblyopia, or “lazy eye,” is present. Amblyopia can develop if the brain starts to ignore the image from the misaligned eye to avoid double vision, leading to reduced vision in that eye. Patching the stronger, dominant eye forces the brain to use the weaker, misaligned eye, thereby strengthening its vision. This therapy can continue for weeks to several months, aiming to improve visual acuity before other interventions.
When eyeglasses or patching are insufficient to correct the misalignment, or for types like infantile esotropia where glasses are not effective, eye muscle surgery may be recommended. During surgery, an ophthalmologist adjusts the length or position of the eye muscles to physically realign the eyes. While surgery can significantly improve eye alignment, it may not eliminate the need for glasses in cases of accommodative esotropia, as the glasses still correct the underlying refractive error.