Aphakia

What aphakia means

The lens sits behind the iris (the colored part of the eye) and focuses light onto the retina. It provides about a third of the eye's focusing power and, in younger people, changes shape to focus at different distances (accommodation). Without it, the eye becomes extremely farsighted (hyperopia) and cannot focus up close at all.

Aphakia (no lens) is different from pseudophakia, where the natural lens has been replaced with an artificial intraocular lens (IOL). Most adults who have cataract surgery today are pseudophakic, not aphakic.

Causes

• Cataract surgery without a lens implant: the most common cause. This happens in infants, where an implant is sometimes deferred, in complicated surgery where an implant cannot be safely placed, or historically, before lens implants were routine.
• Trauma: a penetrating injury can destroy or expel the lens, or a blunt injury can dislocate it.
• Lens dislocation (ectopia lentis): the lens can slip out of position in conditions such as Marfan syndrome, homocystinuria and Weill-Marchesani syndrome. A severely displaced lens may leave the pupil functionally aphakic or need removal.
• Congenital aphakia: extremely rare, when the lens fails to develop. It usually occurs with other eye abnormalities.

Symptoms

• very blurred vision at all distances without correction
• inability to focus on near objects (loss of accommodation)
• with aphakic glasses: images appear about 25 to 30 percent larger, straight lines look curved, and there is a ring-shaped blind area at the edge of the lens (the "jack-in-the-box" effect)
• difficulty judging distances
• in one-eyed aphakia corrected with glasses, the two eyes see images of different sizes, causing double vision
• a trembling iris (iridodonesis) visible when the eye moves, because the lens no longer supports it
• color perception shifted toward blue, because the natural lens normally filters some blue and UV light

Complications

• Glaucoma: raised eye pressure is common after cataract surgery in infancy (aphakic glaucoma) and can develop years later. Lifelong pressure checks are needed.
• Amblyopia: in infants and young children, an uncorrected aphakic eye cannot send a clear image to the developing brain, causing permanent poor vision unless corrected and patched early. See amblyopia.
• Retinal detachment: the risk is higher after lens removal, especially with complicated surgery or high myopia.
• Macular swelling (cystoid macular edema) after surgery.
• Corneal problems, particularly with long-term contact lens wear.

Diagnosis

Aphakia is diagnosed during a routine eye examination with a slit lamp. The doctor sees the absence of the lens, a deep front chamber of the eye and a trembling iris. They measure the focusing power needed, check eye pressure and examine the retina. Ultrasound or imaging may be used if the eye cannot be seen clearly or after trauma.

Treatment and correction

Intraocular lens (IOL)

An artificial lens can be implanted:

• at the time of cataract surgery in most adults
• as a secondary procedure later, fixed in front of the iris, attached to the iris, or sewn to the wall of the eye if the usual lens capsule support is missing

IOLs give the most natural vision because they sit where the natural lens was.

Contact lenses

Contact lenses are often the preferred correction for infants, whose eyes are growing rapidly and whose focusing power changes. Research in infants after single-eye cataract surgery found similar visual results with contact lenses and IOLs, with fewer additional surgeries in the contact lens group. Parents insert and remove the lenses, and they are changed as the child grows.

Aphakic glasses

High-powered convex lenses (often +10 diopters or more) are an option, especially for children with aphakia in both eyes. They are thick, heavy and cause magnification and distortion, so they are less suitable when only one eye is aphakic.

Treating amblyopia

Children usually need patching of the better eye for part of the day, along with bifocals or reading glasses, because the aphakic eye cannot focus up close.

Outlook

With good correction, adults with aphakia can achieve useful and often good vision. In children, the outcome depends heavily on how early the cataract was removed, how consistently the eye is corrected and patched, and whether glaucoma develops. Lifelong follow-up with an ophthalmologist is essential.

Frequently asked questions

What is aphakia?

Aphakia is the absence of the lens of the eye. The lens normally focuses light on the retina, so an aphakic eye is very blurry and strongly farsighted. It most often results from cataract surgery without a lens implant, an eye injury or a dislocated lens.

What is the difference between aphakia and pseudophakia?

In aphakia, the eye has no lens at all. In pseudophakia, the natural lens has been replaced with an artificial intraocular lens, which is what happens in most modern cataract surgery. Pseudophakic eyes usually see well without thick glasses.

How is aphakia corrected?

Aphakia is corrected with an intraocular lens implanted during or after surgery, contact lenses, or high-powered aphakic glasses. Contact lenses are commonly used for infants. Children also need treatment for lazy eye and lifelong glaucoma checks.

Can you see without a lens in your eye?

Yes, but very blurrily. The cornea still focuses some light, so you can see shapes, light and color, but detail is lost and you cannot focus up close. Correction with an implant, contact lenses or glasses restores useful vision.