Novel technique using stem cells revives damaged eye

SIMPLE YET EFFECTIVE: The damaged eye (left) has total 


deficiency of limbal stem cells prior to operation. But the 


same eye 


has become functional after the Simple Limbal Epithelial 


Transplantation (SLET) procedure.

Treating blindness caused by burns using limbal stem cells 

harvested from the undamaged eye of the same patient has 

now become cheaper, easier and safer. Results of a pilot 

study of the SLET (simplified technique of limbal 

transplantation) technique conducted at L.V. Prasad Eye 

Institute on six patients, and published recently in the 

British Journal of Ophthalmologyprovides the proof.

Blindness arises when burns permanently damage the 

limbal stem cells found in the eye and causes loss in corneal 

transparency. In such cases, the stem cells are harvested 

from the healthy eye and transplanted to the damaged eye. 

There are currently two ways of using limbal stem cells to 

cure blindness caused by burns.

One is to directly transplant the stem cells to the damaged 

eye. The other technique — cultivated limbal epithelial 

transplantation (CLET) — is to remove a smaller portion (2 

mm by 2 mm) of the limbus containing the stem cells and 

increase (expand) the cells in the laboratory and then 

transplant them to the damaged eye. While both methods

 are good at restoring vision in the damaged eye, they have 

their own disadvantages.

In the case of direct transplantation — CLAU (conjunctival 

limbal autografting), almost 50 per cent of the limbus (6 

mm to 8 mm length of the limbus), has to be removed from

 the healthy eye. Excess removal of stem cells from the 

healthy eye can permanently damage it.

“At the moment, there is no way of knowing the amount of 

limbal stem cells found in an [undamaged] eye,” said Dr. 

Virender S. Sangwan, Head of the Cornea and Anterior 

Segment Services at L.V. Prasad Eye Institute, Hyderabad. 

Doctors would come to know of the “deficiency” in the 

healthy eye in two to three months after the operation. “But 

how the compromised stem cells will manifest in stressful 

conditions like an eye infection will be known later,” he 

explained.

Though the Institute started off by doing direct 

transplantation (CLAU), it has turned its attention to the 

safer CLET alternative.

Though this procedure is safer, it is expensive and patients 

have to visit the hospital twice, one to remove the limbus 

and the other to transplant the expanded stem cells.

The new technique (SLET) developed recently by Dr. 

Sangwan and his team at the Institute and Dr. Sheila 

MacNeil at the University of Sheffield, UK combines the 

best of both methods.

While only a small portion of the tissue is removed from the 

healthy eye (as in the case of CLET), the stem cell expansion 

takes place not in the lab but in the damaged eye itself.

This ensures that the healthy eye is never damaged, the 

procedure is cheaper and there is less risk of contamination 

(as the expansion does not take place in a lab). “It would 

cost only half the earlier procedure (CLET),” he stressed.

If the medium used in the lab provides nutrients for the stem cells, the tear cells do the same job in this case.

The doctors began trying the new technique during the later 

part of 2009 and performed most of the operations in 2010 

and 2011. Altogether 15 cases have been done so far, of 

which ten patients have already completed six months of 

observation time post operation.

The procedure

The procedure is quite simple and takes about an hour to 

perform. In this, the damaged eye is first cleaned and an 

amniotic membrane is pasted on the cornea using biological 

glue. The 2 mm by 2 mm limbal tissue harvested from the 

healthy eye is then cut into eight to nine pieces and placed 

them on the membrane. Glue is then applied on the cut 

limbal tissue so that it sticks to the membrane. The eye is 

then bandaged using soft contact lens.

“The amniotic membrane acts as a scaffold on which the 

stem cells grow and expand,” Dr. Sangwan explained. “It 

took the same time [as the CLET technique] for the 

damaged cornea to be repaired.”

So simple is the procedure that it can be widely adopted by 

specialists across the country. “With extra training, cornea 

specialists can perform the operation,” he assured.

courtesy- The Hindu