How aniridia affects the eye
Aniridia means “without iris.” In congenital aniridia the iris, the colored ring that controls how much light enters the eye, is partly or completely missing from birth. It is rare. European guidelines put its incidence at between 1 in 48,000 and 1 in 96,000, and in most people it is caused by a change in a gene called PAX6.[1]
The missing iris is the most visible sign, but aniridia affects almost every part of the eye. The guidelines list the main symptoms as light sensitivity, glare, low vision, a dry and irritated eye surface, and nystagmus (involuntary eye movements).[1] Several separate problems tend to build up over a lifetime:
- An underdeveloped fovea. The fovea is the small central part of the retina used for fine detail. It is underdeveloped in 79% to 92% of people with aniridia, and it is a major reason vision is reduced from childhood.[1]
- Glaucoma and cataract. More than half of people with aniridia develop glaucoma, and cataract has been reported in up to 90%.[1]
- A fragile corneal surface. This is the part a scleral lens can help with, and it is explained below.
Aniridia-associated keratopathy
The cornea’s surface is renewed by stem cells at its edge, a ring called the limbus. In aniridia these stem cells are deficient or don’t work properly. Over time the conjunctiva (the thin, vessel-filled tissue over the white of the eye) creeps onto the cornea, bringing blood vessels and haze with it. This is called aniridia-associated keratopathy, or AAK. It causes pain and light sensitivity, and it gradually clouds vision.[1]
AAK is very common: the guidelines report it in 78% to 96% of people with congenital aniridia, and dry eye in 56% to 96%.[1] It usually starts at the edge of the cornea in childhood and progresses over time.
How a scleral lens can help the eye surface in aniridia
A scleral lens is a large rigid gas-permeable lens. It rests on the sclera (the white of the eye) and arches over the entire cornea and limbus without touching them. Before insertion it is filled with sterile, preservative-free saline, which stays trapped over the cornea while the lens is worn.
For a fragile aniridic surface, that does three things:
- It keeps the cornea bathed. The surface stays moist for as long as the lens is in, rather than drying between blinks and drops.
- It shields the surface from the eyelid. The lid slides over the smooth lens instead of rubbing a damaged cornea with every blink.
- It can sharpen vision. The saline layer smooths out an irregular corneal surface optically, which can reduce the blur that comes from the cornea itself.
The European ANIRIDIA-NET guidelines list scleral lenses as an option for dry eye and early stem cell deficiency in aniridia, alongside lubricants, cyclosporine drops, and serum eye drops. They note that a scleral lens doesn’t sit directly on the cornea or limbus, protects the cornea, and keeps the eye lubricated, but can be difficult to fit to the eye.[1]
What the research shows
The evidence in aniridia itself is very thin. We found one published report of scleral lens treatment specifically for aniridic keratopathy. It describes a single 30-year-old woman whose left eye developed a persistent surface defect that drops and serum eye drops had not healed. After she began wearing a PROSE scleral device (a type of custom scleral lens), the defect healed quickly and her vision improved. When her right eye later developed surface problems, it was treated the same way, and the cornea stayed clear for the three years reported.[2] One case can show what is possible. It can’t tell you how likely that result is.
Studies of limbal stem cell deficiency in general are mixed. Aniridic keratopathy is one form of limbal stem cell deficiency (LSCD), and there are small studies of scleral lenses for LSCD from any cause. They were not about aniridia specifically.
- In a series of 31 eyes with LSCD evaluated for PROSE, vision improved in 27 eyes, on average from about 20/145 to 20/58. The surface disease score stayed stable overall, and 24 of the 31 eyes were still wearing the device at last follow-up, for about 10 hours a day on average.[3]
- A second study of 27 eyes with LSCD found a more cautious picture. Vision improved in 7 eyes, stayed stable in 13, and worsened in 7. The LSCD itself improved in 7 eyes, was stable in 8, and worsened in 12. In some of the worsening eyes, imaging showed the lens pressing on the limbus, and the authors suggested low oxygen at the limbus might be to blame. They concluded that scleral lenses can help most eyes but need close monitoring of the fit.[4]
Advanced keratopathy is usually treated surgically. In a long-term review of 92 eyes with AAK at one referral center, eyes at earlier stages were managed medically and their vision stayed stable. Eyes at later stages more often needed limbal stem cell transplantation or an artificial cornea (keratoprosthesis).[5] A scleral lens is most likely to be considered before that point, or when surgery isn’t an option.
Other options, compared
Aniridia care is usually shared between several specialists. A scleral lens is one tool for the eye surface, used alongside the others.
| Option | What it does | Typically suited to |
|---|---|---|
| Preservative-free lubricants | Supplement the tear film | All stages of dry eye and keratopathy |
| Cyclosporine or serum eye drops | Reduce surface inflammation or support healing | More advanced dry eye and early keratopathy |
| Tinted or photochromic glasses | Reduce light entering the eye; correct refractive error | Light sensitivity; the guideline-recommended choice |
| Soft contact lenses | Correct vision or cover the cornea | Strongly discouraged in aniridia because of the risk to the limbus |
| Scleral lenses | Hold saline over the cornea and limbus and shield them from the lid | Dry eye and early keratopathy not controlled by drops |
| Artificial iris implants | Replace the iris inside the eye | Severe light sensitivity in selected eyes, with significant surgical risks |
| Limbal stem cell transplant or keratoprosthesis | Restore or replace the corneal surface | Advanced keratopathy |
The guidelines describe artificial iris implants as reducing light sensitivity in many patients, but list risks including glaucoma, worsening keratopathy, and loss of the cells that keep the cornea clear.[1]
Questions to ask a scleral lens fitter
- How many patients with aniridia or limbal stem cell deficiency do you fit?
- How will you check that the lens isn’t pressing on the edge of my cornea?
- How often will you want to see me, and how will you share findings with my cornea and glaucoma specialists?
- Can I keep using my current drops, and when should I put them in?
- If my child is being fitted, how will you teach us both to put the lens in and take it out?
- What will we watch for that would mean the lens is making the surface worse?
Common questions
Can a scleral lens replace my missing iris?
No. A standard scleral lens is clear and doesn't block light the way an iris does. European aniridia guidelines discourage colored, tinted, and prosthetic contact lenses because of the fragile eye surface, and recommend tinted or photochromic glasses for light sensitivity instead. We found no published studies of tinted scleral lenses in aniridia.
Will a scleral lens make my vision normal?
Usually not. In aniridia, vision is often limited by an underdeveloped fovea, the part of the retina used for detail. A scleral lens can only improve the part of the blur that comes from the corneal surface. Ask your eye doctor how much of your blur comes from each.
Can a scleral lens stop aniridic keratopathy getting worse?
There is no good evidence that it does. A single case report describes a scleral lens healing a persistent surface defect and keeping the cornea clear for several years. In wider studies of limbal stem cell deficiency, some eyes improved and some worsened during lens wear, so close monitoring matters.
Why are soft contact lenses discouraged in aniridia?
European guidelines strongly discourage soft contact lenses because they can reduce oxygen to the edge of the cornea, which may trigger or speed up the stem cell problem behind aniridic keratopathy. Scleral lenses are designed to vault the cornea and its edge rather than rest on them, but the fit still needs checking.
Can children with aniridia wear scleral lenses?
Children are fitted with scleral lenses for surface disease at some specialist centers, and a parent usually helps with putting them in and taking them out. Whether a lens is right for your child depends on their eye surface, glaucoma status, and how well the family can manage the daily routine.