Stem cell dysfunction

The correct approach to the treatment of cataracts in eyes with limbal stem cell disease depends on the stage and severity of both conditions, said Friedrich Kruse MD, of University Hospital Erlangen, Germany, at the XXXIII Congress of the ESCRS in Barcelona, Spain.
He noted that limbal stem cell dysfunction is caused by a decrease in the population or function of corneal epithelial stem cells. That, in turn, makes the cornea unable to maintain the normal homeostasis of corneal epithelium.
When the epithelium degenerates, the conjunctiva moves on top of the cornea, leading to visual impairment. The conjunctivalisation is frequently accompanied by corneal vascularisation, scarring and recurrent epithelial defects.

DIAGNOSTIC CRITERION
However, the most important diagnostic criterion of limbal stem cell disease is the presence of goblet cells on the corneal surface. That can be determined by impression cytology or by in vivo biomicroscopy with the HRT II (Heidelberg).
A simpler way to test for limbal stem cell dysfunction is staining the corneal surface with fluorescein and waiting to see if the stain clears within 10 minutes. If it does not, this is a sign of the loosened epithelial degradation caused by limbal stem cell dysfunction.
In eyes with partial limbal stem cell disease, there are many ways of working around the difficulties, making cataract surgery quite straightforward. However, poor surface quality can still cause some problems with intraocular lens calculation.
In most patients with partial stem cell disease, a procedure called sequential sectoral conjunctival epitheliectomy can enhance the corneal surface quality. A simple method, developed by Prof Harminder Dua, it involves removal of the focal fibrovascular tissue with a crescent blade followed by placement of an amniotic membrane.
Although the procedure needs to be repeated, it can significantly enhance the ocular surface quality in some patients with partial limbal stem cell disease, allowing straightforward cataract surgery.

SLOWLY PROGRESSING CATARACTS
For eyes with total stem cell disease, but early and slowly progressing cataracts, there are a number of stem cell graft procedures that can be used to repair the surface prior to the cataract surgery.
Among the best established procedures is the conjunctival limbal autograft, which involves peeling the fibrovascular tissue from the recipient cornea and then replacing it with conjunctival limbal tissue from the uninjured donor eye.
In bilateral cases, cadaverous conjunctival limbal autografts have been used. There is the need for heavy immunosuppression and therefore the longevity of the procedure is limited, Dr Kruse added.

Friedrich Kruse: friedrich.kruse@uk-erlangen.de