Behind the barrier: exploring ocular immune privilege (C-100111)

31 January 2022
Winter 2022

Kim Thomas explores ocular immune privilege – how does it work, what benefits does it offer and what happens when it goes wrong?

Domains covered

Communication Clinical practice

In 1905, a 45-year-old Austrian labourer named Alois Glogar, whose corneas had been damaged slaking lime, was examined by ophthalmologist Eduard Zirm. Zirm had another patient: an 11-year-old boy named Karl Bräuer, who’d been blinded after an accident. With the permission of Karl’s father, Zirm removed one of the child’s eyes, trephined two corneal buttons and transplanted them into Glogar, enabling the labourer to return to work.

Long before organ transplants were performed in other parts of the body, and immune suppression medication became available, the corneal transplant succeeded because the new corneas were not rejected by the patient. This is down to immune privilege, a term coined by scientist Sir Peter Medawar in the 1940s. Ocular immune privilege (OIP), which occurs throughout the animal kingdom, has evolved to protect the eye from destructive inflammation that may impair vision. 

As well as limiting visual impairment, OIP has enabled two important medical procedures. One, of course, is corneal transplants.

However, there is a caveat, as Dr Graham Wallace, Senior Lecturer in Immunity and Infection at the University of Birmingham, points out: “If you’ve got a corneal transplant on a vascular bed, where there are new vessels grown, it will very quickly be rejected unless you use immunosuppression.” Symptoms of rejection occur in around one in five full-thickness corneal transplants, although only about 5% of low-risk grafts actually fail because of corneal rejection (NHS, 2021).

The other procedure is cataract surgery: globally, around 28 million cataract operations are performed each year (Lindstrom, 2021). Damian Lake, Lead Corneal Transplant Surgeon at Queen Victoria Hospital, East Grinstead, says: “It’s probably the most commonly performed procedure in the world. But it wouldn’t be possible without immune privilege.”

Sign in to continue

Forgotten password?

Not already a member of the College?

Start enjoying the benefits of College membership today. Take a look at what the College can offer you and view our membership categories and rates.

Related further reading

The College has provided key information to help you identify cases and guidance on managing circumstances that are relevant to optometry practices.

The College of Optometrists offers support to hay fever sufferers on managing their symptoms.

This Halloween we're urging the public to think about their eye health.