Written by: Prof. Kent Caslo, Professional Director of ELIA, Developmental Optometrist.
BackgroundIn the fourth week of pregnancy the eyes begin to develop in stages. In the first stage, fibers from the fetal brain are pulled forward to create what will become the eyeball. This shape is reminiscent of a cup, which will close over time until the beginning of the last trimester.
In the picture above you can see how the eyeball is formed: the "glass" closes from top to bottom. If there is no complete closure, a condition of missing tissue called coloboma is created. Lack of tissue, coloboma can be in a number of tissues of the eye – from the posterior tissue area (retina) to the anterior tissue area (iris / pupil).
In this picture we see a normal retina:
You can see a bright circle with a blood vessel (the optic nerve) coming out of the center and around an orange background that is the retina. The smaller darker area is the area of central vision. Everything else, peripheral vision.
In the next picture we see a retina with coloboma – the white area, as in most cases this is the area with the missing tissue, is down – where the closure should have taken place.
If the coloboma is in the back of the retina, we will not be able to see it when we look at the eye. On the other hand, if the coloboma is in the front of the iris (the colored part), we can understand it by looking at the eye. Coloboma can appear in one or both poor eyes.
Coloboma in one eye Coloboma in two poor
Effect of coloboma on vision:
- If there is a coloboma of the iris, there may be good vision, but there will be hypersensitivity to light and glare.
- If there is coloboma also or only in the retina, there may be more significant effects on vision depending on the area of injury. To the extent that the missing area is in the peripheral retina there will be almost no effect on vision. If the defect reaches the retinal area responsible for central vision (macula and phobia) it is likely that there will be impaired central vision and difficulty in color vision. If the missing area also includes the optic nerve there will be an effect on both central and peripheral vision.
Treatment There is no medical treatment for iris coloboma and there are only a few options to deal with iris coloboma. If the problem is a lack of iris tissue, there is a possibility of a contact lens with a printed iris so that there is both an improvement in vision and an improvement in the appearance of the eye and lowering the glare. Another treatment option is artificial iris transplant surgery, this surgery is still considered experimental.
The manner of work will be adjusted according to the injury to the eye.
Examples: Difficulty in field of vision (peripheral vision) – Raise awareness of the missing field of vision. Present things in an existing field of vision and help the child develop effective search and orientation methods.If the damage is in the central vision then it is necessary to work with materials of appropriate sizes, correct distances and high contrast. In addition, it is advisable not to emphasize color distinction, although you can try to work on sorting objects by color – if there is a big difference between the colors and the strong colors.