Aphakia is a condition in which the natural lens is missing from the eye. The lens is located inside the pupil. It focuses light on the back of the eye. The lens works like a magnifying glass which adjusts itself to various thicknesses.
Some children are born without the lens. Other people or children have it removed during cataract surgery.
- Congenital/pediatric aphakia is divided into primary and secondary aphakia
- Aphakia after cataract (opacity or cloudiness of the crystalline lens) surgery
- Aphakic glaucoma
Causes and Risk Factors
The causes of aphakia depend on their types. Congenital or pediatric aphakia is found in babies born without the lens. In primary aphakia, the baby’s lens does not form at all. In secondary aphakia, the lens has developed. It however gets absorbed back or expelled before the child is born.
The lens becomes stiff and cloudy with cataract. Because cataract interferes with vision, doctors will take out the lens during surgery. The individual is said to be ‘aphakic' once the lens has been removed. Also, aphakic glaucoma can result from cataract surgery. The risk of acquiring it is highest with surgeries done before a baby is four weeks old. Aphakic glaucoma develops 4 to 6 years after surgery.
Signs & Symptoms
The signs of aphakia include:
- Very deep anterior chamber
- The pupil looks jet black due to the absence of lens
- Absence of the crystalline lens
- Inability to focus
Congenital aphakia symptoms vary from infant to infant and may include:
- Abnormally small eyeballs
- Clouding of the lens of the eye
- Absent iris
Diagnosis depends on the symptoms and signs of aphakia. The eye professional will use a retinoscope to determine the refractive power of the eye.
Treatment is aimed at restoring the function of the lens to focus light on the retina.
Aphakic glasses or contact lenses can be used. However, aphakic glasses are not recommended because they distort images. They can also cause anisometropia (unequal refractive errors) and aniseikonia (unequal retinal image sizes). Anisometropia produces confusion which can lead to amblyopia, strabismus and other anomalies. Also, glasses will not work with unilateral aphakia where both eyes are affected because of the differences in image sizes. Glasses are also bigger and heavier compared to lenses.
Aphakia contact lenses are a better option. Contact lenses are prosthetic devices that replace the lens of the eye. They must be fitted as quickly as possible in infants. This is to allow the visual pathway to the brain to begin forming. Three types of contact lenses can be used for pediatric aphakia:
- Rigid gas permeable (RGP) considered the best option
- Silicone elastomer (only during waking hours as they are highly permeable to oxygen)
- Hydrogel lenses (children over four years of age).
Intraocular lenses are implantations on the eye. They carry several advantages:
- Minimal care after surgery
- Normal peripheral vision
- Minimal aniseikonia
- Rapid return of binocular vision
However, the child risks developing visual axis opacification (VAO). VAO can hamper the optical image quality required for normal visual development.
Children must wear contact lenses at all times. The lenses are essential for stimulating vision. Failure to use the lenses could lead to vision loss. It is also important for parents to keep a backup pair of contact lenses at home. The back-up pair will come in handy in case of loss or damage.
A frequent examination to track a child’s visual development is necessary. Children's eyes continue to grow, unlike adults. As the eyes grow, the power to correct the child’s vision will decrease. For this reason, children require frequent changes in the contact lenses.
The infant should be seen weekly or bi-weekly in the first three months after fitting. After that, the baby will be seen monthly for the first year of life. At 6-8 weeks, the contact lenses must be changed. The lenses will then be changed at 6-9 months. They will also be replaced at age one.
Thereafter, the child can be seen every two to three months. Generally, a child requires close medical attention in the first ten years of his/her life. Subsequently, check-ups will be necessary every two years for the rest of his/her life.
Improving a child’s vision if treatment is not administered within a year is difficult. Very little can be done for an aphakic child after eight years.
Aphakia can cause hypermetropia (hyperopia or farsightedness). Hypermetropia is a refractive error where parallel rays enter the eye and are focused behind the retina.
Young children are at risk of developing amblyopia. Amblyopia refers to decreased vision in one or both eyes. It comes about due to the abnormal development of an infant’s vision.
Aphakia also increases the risk of retinal detachment. Retinal detachment is an emergency. It happens when some tissue in the retina pulls away from its usual position.
Parental counseling is necessary. Parents are taught how to care for the child's delicate eyes. They are also made aware of the risk of the child developing amblyopia, hypermetropia, glaucoma, strabismus (misaligned eyes) and so on.