|
How are stem
cells used for treating eye disorders?
All eye disorders cannot be treated with stem cells; only
the front part of the eye can be treated.
The eye’s outer surface is exposed to the environment, and
has a constant turnover of cells to maintain the optical transparency
of the cornea. These cells are regenerated from reserve stem
cells, known as limbal stem cells, which are found in an area
called the limbus. The limbus is a transition zone separating
the central transparent cornea and the peripheral area (See
diagram of the eye showing the limbus). The function of limbal
stem cells is to regenerate the epithelial (surface) cells
of the cornea, while also serving as a barrier to ensure that
the conjunctival cells do not grow over the cornea and mar
its transparency.
Diagram of the eye showing
the limbus
Limbal stem cells
help regenerate the surface of the cornea when there is any
decay or damage. However, in cases of chemical burns, allergic
reactions to drugs and auto-immune diseases, the limbal stem
cells may become damaged and lose their ability to regenerate
new cells. This condition is known as ‘limbal stem cell deficiency’
(LSCD). This deficiency can be made up in two ways: by direct
limbal transplants or by culturing the limbal cells in a controlled
environment and transplanting them. The raw surface of the
eye causes pain, redness and decreased vision.
The damage to the limbal cells may be partial or total; it
may be unilateral/in one eye or bilateral/in both eyes. Based
on the extent of damage, doctors make a clinical decision
whether a graft from the same eye will be sufficient, or whether
there is a need to take it from the other eye. There are two
types of grafts – allograft and autograft. In allograft the
cells used for culturing are taken from a relative or donor,
while in autograft the cells for culturing are taken from
the patient.
The
surgery
The procedure involves a relatively minor surgery to remove
the tissue, which is then cultured in a laboratory on a human
amniotic membrane. After almost a fortnight it is then transplanted
into the patient. Following surgery, the patient is checked
in the clinic, with follow-up visits scheduled every 4-6 weeks
till it is found satisfactory.
|
