Aniridia-related keratopathy (ARK) is the kind of condition that makes ophthalmologists uncomfortable. It’s relentless. A PAX6 gene mutation disrupts limbal stem cells — the gatekeepers that keep the cornea clear — and conjunctival tissue quietly invades, clouding the eye like frost creeping across a window. Standard corneal transplants can’t fix this. They patch the surface without addressing the broken stem cell supply underneath. For patients, that means progressive, bilateral vision loss with few effective options remaining.
Researchers at Moorfields Eye Hospital and UCL just changed that calculus.
A Two-Cell Scaffold Targets the Root Problem
By delivering two distinct stem cell types simultaneously, RAFT-OS addresses both the surface and the structural layers conventional transplants leave untouched.
RAFT-OS — Real Architecture for 3D Tissues–Ocular Surface — is a collagen scaffold seeded with two types of donor stem cells: limbal epithelial cells (the surface-renewing layer) to rebuild the corneal surface, and stromal keratocytes (structural support cells) to stabilize the deeper tissue. Think of it like renovating a building by replacing both the facade and the load-bearing walls simultaneously, rather than just repainting over the damage.
The first-in-human trial, published July 23 in JAMA Ophthalmology, treated nine adults with advanced ARK. Key findings:
- Mean ocular surface scores dropped from 9.4 to 5.9 at three months in treated eyes; untreated fellow eyes barely moved (8.4 to ~8.0 at 12 months)
- Treated eyes gained an average of 24 ETDRS letters — nearly five lines on a standard vision chart
- One serious adverse event triggered a protocol amendment; two patients developed persistent epithelial defects
- Follow-up ran to 12 months; funding came from the UK Medical Research Council, Moorfields Eye Charity, and NIHR
“The first-ever optical use of a collagen scaffold containing two types of stem cells,” said Professor Sajjad Ahmad of Moorfields and UCL, according to MedicalXpress, adding that it “has proved effective for a previously untreatable progressive condition leading to sight loss.”
Promising Signal. Not a Verdict.
The ocular surface results are encouraging, but the trial’s size and design mean larger randomized studies must confirm what this first-in-human data can only suggest.
Read the fine print. The confidence interval for visual acuity improvement crosses zero (95% CI −0.97 to 0.04), which means the formal statistical evidence for sustained vision gain is thin. Nine patients, nonrandomized, no placebo arm. This is a first-in-human signal — meaningful, but not yet proof.
Elsewhere, researchers are pursuing PAX6 gene correction to fix the upstream defect entirely. RAFT-OS bets on replacing damaged tissue architecture directly. Both approaches are attacking different floors of the same burning building.
Ahmad’s team plans a larger randomized trial with NHS adoption as the stated goal. For the estimated millions living with aniridia globally — a condition affecting roughly 1 in 40,000 to 1 in 100,000 people, with ARK developing in up to 90% of patients over a lifetime — that pipeline represents the clearest path from a promising first result to a treatment that actually reaches a clinic near you.
