Genetic Eye Disorders in Pediatrics

Introduction

The human eye is a complex structure that is organized and controlled by many genetic factors. Any alteration in the genetic structure can lead to abnormality including visual impairment or total blindness. The abnormality can be hereditary, nonhereditary, or congenital. At present, there are only limited options available for treating the genetic nature of eye disorders.

Several diseases related to the eye have been linked to a genetic abnormality. These diseases are mostly linked to known genes. It is often seen that genetically related syndromes have concurrent ocular manifestations. The reason for these eye manifestations is single loci of genes affected or sometimes multiple genes with defects resulting in abnormal ocular conditions related to the syndromes. The phenotype presentation of the disorder may vary from regular to entirely blind. Several eye abnormalities are present at birth; some can present later in life. In some unfortunate cases, there can be no treatment, and no intervention can be done. In most cases, early diagnosis and proper treatment can lead to restoring normal vision and can indeed be life-saving.

Healthcare professionals such as pediatric ophthalmologists should have a good knowledge of common eye disorders to diagnose and intervene appropriately and deal with other specialists who can improve child care as a team. As more studies are being conducted on the genetic background of ocular diseases, a thorough knowledge of the pathogenesis and etiology of the conditions can lead to better and more effective treatment strategies.

What Is Hereditary Eye Disorder?

The healthcare professional should know the inheritance, genetic patterns, and abnormalities. In his studies, Mendel gained vast knowledge about genetics in his law of segregation and independent assortment. The genes are paired into alleles, and only one allele is transmitted by the parent to the offspring. Some genes are recessive, and some that are dominant. The diseases that are related to dominant genes are present in all generations.

In contrast, the abnormalities carried by the recessive genes may skip one generation and can affect the other generation. In the case of consanguineous marriages, the recessive genes have a high chance of expressing themselves, and the disorders carried by the recessive genes may be present in all generations. X chromosome-linked diseases may be expressed in males and females, who are the carriers.

In some instances, a specific inheritance pattern is not present, and these are usually considered mutated genes. Retinoblastoma can be mutated, gene-related, or sporadic. In Bardet Beidl syndrome, three alleles should be affected. In some ocular abnormalities, only one specific gene is affected. This one abnormal gene is responsible for different ocular manifestations. Myopia is associated with defects in multiple loci of genes and is a pervasive eye disorder. Cornea plana, which is presented as flat cornea and hyperopia, is a recessive gene-related condition that makes it very rare.

Which Pediatric Patient Is Most Likely to Have a Genetic Eye Disorder?

A pediatric patient who is suffering from nystagmus is considered to be at a higher risk of developing a disorder related to eye movement. This nystagmus is a sign of developing eye disorder and should not be considered as a diagnosis. Other disorders are developmental or congenital cataracts, juvenile glaucoma, and myopia at a preschool age. Albinism is also a genetic disorder that is characterized by skin and eye pigmentation. This genetic disorder can sometimes be related to fatal systemic disorders.

What Are Common Hereditary Eye Disorders in Pediatrics?

Certain hereditary eye disorders are common. These include:

• Ocular Coloboma: Approximately 11 percent of pediatric patients are blinded by coloboma. This condition is characterized by an inferior and ventral gap in a few tissues that extend between the optic nerve and the cornea of the eye. This may affect one or both eyes and have a genetic etiology. Clinically it is presented as small eye size and, in very severe cases, absence of one or both eyes. The proper mechanism of coloboma causing a unilateral effect remains unclear, and the knowledge and further research may help develop more therapeutic measures. Failure of choroid fissure fusion results in coloboma. The macula, an essential retina structure, is involved in coloboma. Coloboma has a genetic influence as is usually seen in almost 80 percent of the countries.

• Anterior Segment Dysgenesis: It affects the tissue in front of the vitreous. The importance of the tissue is to focus the light on the retina and aqueous humor, which maintains clarity in vision. One of the types i.e. glaucoma presents with increased intra-ocular pressure. The patient may have increased corneal diameter and enlargement of the eye. Abnormality in the angle of the eye can also be seen. In some cases, the abnormality in the iris can also be seen.

• Leber Congenital Amaurosis: The vision is generated when the light falls on the retina. Any defect in the retina may cause blindness caused by the death of photoreceptor cells in the eye present on the retina.

What Are the Treatment Strategies for Eye Diseases in Pediatrics?

Designing a treatment plan for genetic disorders of the eye remains challenging. The clinical presentation is seen months after the defect has started to invade and involve the ocular cells and tissues. Each condition has its therapeutic targets.

• Gene therapy: This delivers the required products of genes into the diseased or affected cells or tissues of the eye. Injecting viral vectors is a simple technique of delivering genes to affected eye tissue with a low immune response.

• Drug therapy: Small molecule medicines or drugs efficiently administer and control their dose and monitor them across the blood-brain barrier. PCT124 has been effectively proven to benefit the Pax6 mutation that causes iris coloboma. Antioxidants are also proven to be helpful.

Conclusion

Eye diseases have extensive phenotypic and genotypic heterogeneity. However, extensive research has provided clear knowledge of the genes responsible for various ocular diseases. Gene-free treatment should be available, and modulating pathways associated with small and large-molecule drug therapies can have promising effects on ocular diseases in pediatrics. Suppression therapy, antiapoptotic concepts, and neurotropic drugs may also effectively treat defective cells and tissues of the affected eyes. As the knowledge about the pathogenesis and etiology of the ocular disorder increases, the chances of developing better and easier treatment strategies are possible.