Congenital Glaucoma - Types, Causes, Diagnosis, and Treatment

Introduction

Glaucoma is a group of ocular disorders (eye diseases) damaging the optic nerve that relays visual signals to the brain. The damage to the optic nerve causes poor vision or complete loss of vision if left untreated. Glaucoma can affect any age group. But congenital glaucoma affects only infants (from birth to 3 years of age). It is also called infantile glaucoma. Congenital glaucoma is very rare and noticed in approximately 1 in 10000 births. It affects both eyes in most cases.

What Is Congenital Glaucoma?

Congenital glaucoma damages the optic nerve due to increased intraocular pressure (fluid pressure inside the eyes). Usually, there is space inside the eye chamber filled with aqueous humor (clear liquid inside the eye). The aqueous fluid flows in and out of the eye, bringing in nutrients.

In congenital glaucoma, the fluid is not drained properly. It gets collected inside the eyes, which increases intraocular pressure, and the optic nerve gets damaged by the pressure.

What Are the Types of Congenital Glaucoma?

Congenital glaucoma is divided into two types as follows:

1. Primary Congenital Glaucoma - It occurs at the time of birth without the association of any other diseases or conditions. The primary congenital glaucoma is subdivided depending on the age of onset as follows:

• True Congenital Glaucoma - In this type of glaucoma, the enlargement of the eyes is noticed at the time of birth or within one month after birth. The intraocular pressure inside the womb increases and is called newborn glaucoma.

• Infantile Glaucoma - This type of congenital glaucoma is developed in the child approximately from 1 to 3 years of age.

• Juvenile Glaucoma - This type of congenital glaucoma is noticed in children after three years of age but before adulthood.

2. Secondary Congenital Glaucoma - This type of congenital glaucoma occurs associated with other conditions at birth.

• Secondary congenital glaucoma due to eye diseases such as aniridia (absence of colored part of the eye), uveitic glaucoma (glaucoma due to inflammation of the middle layer of the eye), Peter's anomaly (eye disease affecting the front part of the eye).

• Secondary congenital glaucoma due to systemic diseases such as chromosomal, metabolic, and connective tissue disorders.

What Are the Causes of Congenital Glaucoma?

The exact causes of congenital glaucoma are not clearly understood. The risk factors of congenital glaucoma are

• Heredity (parents with a family history pass the disease to the child).

• Autosomal recessive inheritance - Both parents carry a copy of the altered gene without signs and symptoms.

• Genetic reasons.

• Birth defects such as underdeveloped parts of the eye.

What Is the Pathophysiology of Congenital Glaucoma?

An increased quantity of collagen in the trabecular network (network of tissues that allow the aqueous fluid to pass in and out of the eye) obstructs the meshwork. It causes an increase in intraocular pressure. This theory is the most accepted.

The other theory states that the trabecular meshwork is underdeveloped in the child at birth. The outflow of the aqueous fluid decreases due to the poor development of the eye’s drainage system before birth.

What Are the Characteristics of Congenital Glaucoma?

Congenital glaucoma shows no signs at birth. The doctors may note the signs and symptoms after 3 to 6 months. Sometimes the child shows symptoms after three years of age. The characteristic sign of congenital glaucoma are:

• Photophobia (extreme sensitivity to light).

• Epiphora (excessive production of tears).

• Blepharospasms (uncontrolled closing of the eyelids or blinking).

• Buphthalmos (bulging eyes).

• Redness of the eye.

• Cloudy cornea (the transparent clear layer at the front of the eye becomes cloudy).

• Newborns become fussy and refuse to feed due to irritability.

• Poor vision.

• Nystagmus (a disorder of the eye causing rapid and repetitive eye movements).

• Strabismus (crossed eyes).

• Increased myopia (nearsightedness).

How to Diagnose Congenital Glaucoma?

The doctor rules out a family history of glaucoma and consanguineous marriage (marriage between closely related individuals) between parents. Ophthalmologists perform eye examinations for children under anesthesia (medications inducing sleep) because it is difficult to perform diagnostic tests for small children. The diagnostic tests for congenital glaucoma are:

1. Eye drops are used to dilate pupils to examine the retina (the light-sensitive layer at the back of the eye) and optic nerve to detect the damages caused by congenital glaucoma.

2. Tonometry - Ophthalmologists place instruments in the eyes to measure intraocular pressure (IOP). Normal IOP is 10 to 20mm of mercury. This level is elevated in the case of congenital glaucoma.

3. The size and diameter of the cornea are examined. The normal size of the cornea ranges between 9.5 to 11.5 mm. A size greater than 12mm is a sign of glaucoma.

4. Gonioscopy - The procedure measures the angle between the iris and cornea, which helps diagnose glaucoma.

5. Pachymetry - Simple test to measure the thickness of the cornea.

6. Axial length is measured using ultrasound. The axial length is 18mm at birth, and it is increased in cases of congenital glaucoma.

7. Cycloplegic Retinoscopy - Used to evaluate refractive errors.

How to Treat Congenital Glaucoma?

The treatment of congenital glaucoma depends on the disease’s severity and the children’s age. The treatment includes medical and surgical approaches.

1. Medical Approach

• It takes place before the surgical treatment to regulate the aqueous flow.

• Beta-blockers like Timolol and Betaxolol are used to reduce the aqueous flow.

• Prostaglandin analogs like Travoprost increase the aqueous flow.

• Antibiotics are prescribed after the surgery to treat infections.

2. Surgical Approach

• Most doctors prefer microsurgeries in which small tools are used to create drainage canals for excess fluid to drain.

• Angle surgical procedures are done using goniotomy (internal approach) and trabeculotomy (external approach).

• Filtration procedures are:

• Trabeculectomy - Removal of a small amount of tissue to create a new channel for fluids to drain.

• Glaucoma drainage devices are small devices placed in the eye to divert the aqueous fluid to an exterior reservoir.

• Deep Sclerectomy - Removal of the outer part of the trabecular network.

• Cyclodestructive procedures are only for eyes with poor visual prognosis.

Conclusion

The overall prognosis of congenital glaucoma depends on the severity of the disease and early detection of the disease. Congenital glaucoma is treatable only if detected earlier. Early diagnosis and prompt treatment will provide good vision. Intraocular pressure and optic nerve should be evaluated regularly after the surgery. Proper education of the parents and hospital workers about the signs and symptoms of the diseases can prevent blindness in children.