Most cases of Fuchs endothelial corneal dystrophy (FECD) are the result of genetic instability and accumulated DNA damage in corneal cells, according to a new study. Researchers say this means patients with FECD, a leading cause of age-related vision loss, could benefit from new treatments already in development for related disorders.

Short tandem repeats (STRs) are short sequences of DNA that are repeated a number of times consecutively. They make up 3% of the human genome and are more prone to genetic mutation.

Errors during the DNA repair process can lead these sequences to expand. FECD is one of more than 40 known disorders linked to STR expansions.

STR expansion at a specific location in a gene called TCF4 significantly increases the risk of FECD (Wieben et al, 2012 ).

In a new study published in the journal eBioMedicine, researchers used a high-resolution genome-imaging technique to analyse samples from nine individuals who had undergone corneal transplants to treat FECD.

Scientists found the lengths of FECD-associated STR expansions to be four to 17 times longer in corneal endothelial cells than in blood cells from these patients. These genetically unstable large expansions were not seen in samples from controls.

As this pattern occurred consistently and exclusively in affected corneal endothelial cells, the researchers hypothesised that longer STRs, genetic instability and faulty DNA repair combine to drive FECD onset and progression.

Some companies are developing therapies for other conditions linked to STR expansions. More work is needed, but the new findings suggest these may also have potential in the treatment of FECD.