Primary Congenital Glaucoma (cont.)
Exams and Tests
Often in the childhood patient, the eye examination must be performed under general anesthesia to obtain important information regarding the disease.
The ophthalmologist performs the following examinations in the operating room:
- Tonometry is a method used to measure the pressure inside the eye. Pressures that are recorded while the child is under general anesthesia are usually lower than those obtained in the office because of the effects of the anesthesia.
- The cornea is measured and examined.
- The average diameter of the cornea at birth is less than 10.5 millimeters. Because of elevated IOP, the cornea becomes enlarged. If the cornea is more than 12 millimeters in diameter in the first year of life, glaucoma is a strong possibility.
- The cornea may be swollen as a result of the elevated IOP. It may also appear hazy. This haze usually clears when the pressure returns to normal. In advanced cases, severe clouding of the cornea may occur due to the corneal swelling. This cloudiness of the cornea may persist even after the pressure is reduced inside the eye.
- Haab striae may be seen as a result of elevated IOP. Haab striae are tears in the Descemet membrane, which is the inner tissue layer of the cornea.
- Gonioscopy is performed to check the drainage angle of the eye. This test is important to determine if the angles are open, narrowed, or closed and to rule out any other conditions that could cause elevated IOP. To view the angle, a special contact lens is placed on the eye.
- The angle of the eye is formed where the iris and the cornea come together. Because the iris is frequently abnormal in many types of childhood glaucomas, the angle is often affected. Abnormalities in the angle can cause glaucoma. Therefore, the iris and the angle are always carefully studied with a thorough gonioscopy.
- In children, glaucoma may deepen the anterior chamber. A deep anterior chamber hampers the flow of fluid from the eye and allows it to build up inside the eye, thereby causing high pressure.
- Ophthalmoscopy is a method used to examine the optic nerves for any damage or abnormalities. This may require dilation of the pupils to ensure an adequate examination of the optic nerves.
- The most important indicator of the extent and severity of the disease is any changes in the optic nerve. Unfortunately, by the time that glaucoma is diagnosed in a child, the optic nerve is usually abnormal.
- Fundus photographs, which are pictures of the optic disc (the front surface of the optic nerve), may be taken for future reference and comparison.
The ophthalmologist may also perform the following examinations in the operating room if the proper equipment is available:
- Pachymetry is a method that may be used to evaluate the extent of corneal swelling.
- A-scan ultrasound may be useful to measure the length of the eye.
Francisco Talavera, PharmD, PhD
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