Heterotopia - Types, Causes, Symptoms, Diagnosis, and Treatment

Introduction:

Heterophoria is an eye disorder where the eyes' directions are "not straight," in which one eye points up or down in relation to the other. It is caused by head injuries, orbital tumors, brain stem lesions, and systemic illnesses, including multiple sclerosis, Grave's disease, and myasthenia gravis, and rarely due to congenital abnormalities in muscle attachments. Heterophoria often has no symptoms. If it appears after the age of six to eight years, diplopia is frequently seen and might negatively impact a child's self-esteem. Compensating vergence is the process of using the fusional reserve to treat heterophoria. When left untreated, signs and symptoms manifest and can cause strabismus, or a squint can even result in long-term visual issues.

What Is Heterotopia?

Heterotopia is the abnormality of one or both eyes tilting inwards or outwards from the nose, which prevents parallel vision. Normally, the muscles connected to each eye move simultaneously in the same direction. When there is, an alteration in the function of the ocular muscle or eye muscle results in heterotopia. The misalignment of the eyes' visual axes results in altered vision. Most frequently, heterotopia starts in early childhood. It is also known as squint or crossed eyes, or strabismus.

What Are the Types of Heterotopia?

Heterotopia is distinguished into seven following types

• Esotropia.

• Exotropia.

• Hypertropia.

• Hypotropia.

• Cylotropia.

• Disassociated vertical deviation (DVD).

• Dissociated horizontal deviation (DHD).

Esotropia: Esotropia is an eye alignment condition in which one eye is nasally or inwardly deviated. The divergence might be continuous or episodic. Depending on the situation, the deviating eye may always be the same or alternate between the two.

Exotropia: The condition resulting in the outward-moving eye. Like esotropia, the deviating eye may always be one eye or alternate between the two eyes, and the divergence might be continuous or episodic.

Hypertropia: Upward deviation of one eye in comparison with the other.

Hypotropia: Downward deviation of one eye when both eyes are open.

Cylotropia: The two eyes' visual fields consequently appear tilted in relation to one another in which one or both eyes are rotated around their visual planes.

Disassociated Vertical Deviation (DVD): Ocular motor dysfunction causes one eye to drift upward when the patient concentrates on the other slowly. This can be either unilaterally or bilaterally. The deviation could be latent, not immediately apparent to others, or evident, which is only seen after a cover-uncover test.

Dissociated Horizontal Deviation (DHD): Shift in the balance of the vision that results in altered horizontal ocular alignment without regard to accommodation.

What Are the Causes of Heterotopia?

The major cause of heterotopia in children is still unknown. Although the heterotopia's familial history is noticed, congenital abnormalities in muscle attachments can lead to this condition. The neurological factor responsible for heterotopia are anomalies of visual pathways, brain damage, embryopathy ( developmental abnormality of an embryo or fetus), and anomalies of convergence and divergence The other etiological factors are

• Head injuries

• Orbital or eye tumors.

• Brain stem lesions or abnormalities.

• Systemic illnesses, including multiple sclerosis (disease of the brain and spinal cord or central nervous system which affects the communication between brain and body), Grave's disease (autoimmune disorder with excessive production of thyroid hormones which leads to hyperthyroidism), stroke, and myasthenia gravis (an autoimmune disorder which disrupts antibodies which communicate between nerves and muscle, resulting in skeletal muscles weakness).

• Eye or blood vessel injury.

• A cataract, in an attempt to correct other visual issues, can occasionally result heterotopia.

What Are the Signs and Symptoms of Heterotopia?

The eyes of a newborn may initially be off-center. But by 3 to 4 months of age, the eyes usually begin to line up. Sometimes, the eyes appear out of place because the kid has a wide nose bridge, giving the impression that the eyes are crossed. Generally aligned at a later stage of life, it is necessary to undergo medical investigations if not corrected. Even toddlers could complain of double vision, weary eyes, light sensitivity, or blurry vision. However, the symptoms are not persistent and may worsen when the child gets tired or sick. The most significant signs and symptoms of heterotopia are,

• Inability to focus the eyes simultaneously in the same position results in misalignment of the eyes.

• Unbalanced movements of eyes when both eyes move together.

• Blinking or shutting off one eye when exposed to direct sunlight.

• The act of turning or tilting the head to gaze at something.

How to Diagnose Heterotopia Condition?

Heterotopia is a condition diagnosed by physical examination of the child’s eye. The child may be asked to focus on an object while having each eye covered and then uncovered by the doctor. This enables the physician to determine which eye rotates, how much it rotates, and under what conditions the abnormal turn occurs. Additionally, determine whether the kid has amblyopia (lazy eye), which can occasionally coexist with the heterotopia condition. Regular eye checkups for kids are also advised due to impairment of vision. The other test involves

• Lancaster Red-green Test: The patient uses two lights, red and green, one held by the physician and the other light held by the patient while wearing red-green eye glasses, allowing them to be observed individually from each eye. The Lancaster red-green test may be used to quantitatively detect latent eye position problems quantitatively, whereas the cross-cover test only provides a qualitative evaluation.

• Maddox Rod Test: The double Maddox rod test and the Maddox rod test are very sensitive to ocular discrepancies. The test must be conducted with the least light possible because even low light encourages fusion, which can assess vertical and horizontal deviation.

What Are the Treatment Options for Heterotopia Conditions?

The most common treatment options for heterotopia conditions include

• Some heterotopia conditions get resolved by wearing glasses.

• Amblyopia usually requires a temporary eye patch over the eye for a few weeks or months. This may aid in eye alignment by strengthening the weak eye.

• When there is no improvement with the above options, muscular surgery for the eyes is recommended in rarely to enhance eyesight or better align the eyes. Unfortunately, one or more surgery is required, followed by wearing glasses for a long period.

Conclusion:

The only way to delay the onset of these aberrations, according to Bielschowsky, is to strengthen the fusional mechanism; the latter makes it simpler to suppress fragmented vertical motions. This suggests that early visual rehabilitation in such circumstances of sensory visual loss may be able to stop the unmasking of primitive responses like the dorsal light reflex and subsequently the DVDs (disassociated vertical deviation). Ophthalmologists are increasingly inclined to see the outcomes of heterotopic surgery as satisfactory if good binocular vision is attained. Combining surgery with orthoptic training improves the ocular muscles responsible for deviations.