Most people with aphakia require some type of vision correction, although people who were very near-sighted before they became aphakic sometimes require no correction for distance or near vision. Learn about this condition and how it affects eyesight. The absence of the lens of the eye is known as aphakia. The lens is a nearly transparent structure that sits behind the iris, which is the colored part of the eye that expands and contracts depending on the amount of light that reaches it. The lens is biconvex, meaning that it curves outward on both sides, and its sole function is to focus light rays onto the retina. People may have a lens surgically removed, for example, during cataract surgery. Very rarely a person may be born without one or both lenses, a condition known as congenital aphakia. Aphakia can also result from dislocation of one or both lenses as a result of trauma. If you have aphakia, your ability to focus is impaired and you will have difficulty seeing.
Symptoms of Aphakia
People with aphakia have defective vision and suffer from hypermetropia, or long sightedness. While the term long sightedness may seem like it means the ability to see long distances, it does not. A person with “high” long sightedness—that is, someone who is very long sighted—has a prescription or visual acuity of +4.00 or more and is likely to require glasses for both distance and near vision. Aphakia also causes loss of accommodation, meaning that the eye cannot maintain its focus on an object as that object moves closer or farther away. Other vision changes you may notice include erythropsia, in which objects appear reddish, and cyanopsia, in which everything appears to have a blue tint. Either of these symptoms can occur after cataract surgery and are temporary. The colors become intensified because the missing lens lets in a lot more sunlight, and the blue and red rays that were once absorbed by the lens now reach the retina.
What Causes Aphakia?
There are three main causes of aphakia:
- Aphakia caused by a genetic defect: Congenital aphakia has two forms—a primary from that leads to severe eye malformations, and a less severe secondary form. Mutations in the FOXE3 gene have been identified in families with aphakia.
- Aphakia after surgery: Aphakia is usually associated with the surgical removal of a cataract.
- Aphakia after trauma: Trauma can cause extrusion of the lens (when the lens is pushed or forced out of place), or dislocation of the lens.
How Is Aphakia Diagnosed?
Your eye doctor can determine whether you have aphakia by examining you and looking at your medical history. There may be additional reason to suspect aphakia if you have previously had cataract surgery. There are several signs that can indicate a missing lens:
- A scar in the limbal ring (the black ring around the iris); this may be apparent in a person who has undergone surgery
- Iridodonesis — the iris jiggles because it lacks the support of the lens
- The finding of a small hypermetropic fundus (the fundus is the interior surface of the eye, opposite the lens, and hypermetropic means that the eyeball is too short, so light doesn’t focus clearly on the retina, but rather behind it)
An eye examination is performed to determine your visual acuity/prescription (distance, near vision, refraction). If you suffer from aphakia, this will confirm the absence of the lens. The cornea, iris, anterior chamber, and fundus will be examined and your eye pressure will be tested.
How Is Aphakia Treated?
Aphakia can be corrected with glasses, contacts, or surgery. Aphakic glasses can only be used if the condition affects both eyes, and there are several disadvantages for those who use them, most notably a higher than normal magnification, a considerable decrease in field of vision, and the cosmetically unacceptable appearance of the thick lenses, which magnify the eyes. Treatment of babies with aphakia may involve the use of specialty contact lenses. These contacts lenses are safe for the baby to sleep in and they can be used for a longer duration than traditional contact lenses. In addition to wearing contact lenses, babies with aphakia may need eye drops or an eye patch—or both—to encourage the use of the eye with aphakia. Treatment for aphakia in children and infants is very important; if the condition goes untreated it can lead to amblyopia. According to the American Association for Pediatric Ophthalmology and Strabismus, both surgical and optical treatment must be provided urgently for childhood cataracts. After the cataracts are removed, the parents have to choose the type of optical correction that will be used.
The choices include aphakic (high power) contact lenses with bifocal glasses; aphakic (high power) glasses; and intraocular lenses with bifocal glasses. Aphakic contact lenses provide optimum optical correction. Adults with cataracts undergo cataract surgery with intraocular lens implantation. A synthetic, artificial lens is placed inside the eye to replaces the focusing power of a natural lens that is surgically removed. This routine procedure results in few complications. Outcomes of cataract surgery are usually very good. Most have significant improvement in vision. While implantation of an intraocular lens is routine in adults, it can cause significant vision problems, such as myopia, in children. When to implant intraocular lenses in a child is controversial, and the procedure carries risks of complications at any age. Children who undergo intraocular lens implantation, as well as those with high-power contact lenses, will also require bifocal glasses to fine-tune the refraction and allow vision at distance and near.
What Is the Prognosis for Aphakia?
The prognosis for patients with aphakia is usually good unless there are complications. During childhood, the size of the eye and the refractive error change rapidly. Optical correction in children requires frequent adjustments to ensure that optimal vision is maintained. Failure to make these changes in a timely manner may result in permanent visual loss.