|Year : 2001 | Volume
| Issue : 3 | Page : 151-152
Ocular surface failure is treatable
Jagiit S Saini
Dept. of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh -160 012, India
Jagiit S Saini
Dept. of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh -160 012
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Saini JS. Ocular surface failure is treatable. Indian J Ophthalmol 2001;49:151-2
The past few years have witnessed significant progress in understanding the cell dynamics of the ocular surface and its clinical applications. Several studies have confirmed that the corneal stem cells probably reside at the limbus in inter-palisade rete ridges, in the basal layer. An intricate neuro-anatomic integration with blind reflex, tear production and clearance complements the continuous self-renewal with both vertical and centripetal horizontal cell kinetics. Application of these concepts is fundamental to understanding diseases of the ocular surface and management principles.
A deficiency of tear film formation (dry eye) is a relatively innocuous clinical problem. Attendant ocular surface failure is a far more serious clinical entity. It is critical however to initiate management of tear film disorders while managing ocular surface failure. Eyes with ocular surface failure generally have chronic symptoms of photophobia, tearing, blepharospasm, and recurrent episodes of pain, chronic inflammation with redness with or without decreased vision. The biomicroscopic findings at slitlamp examination may vary from dull irregular reflex of the corneal epithelium to ingrowth of thickened fibrovascular pannus, chronic keratitis, scarring and calcification. Because conjunctival epithelium is more permeable than corneal epithelium, conjunctivalised corneal surfaces are frequently stained abnormally by fluorescein. The conjunctivalised surface of the cornea always shows a stippled staining pattern with fluorescein, is thinner than adjacent normal corneal epithelium, is irregular, prone to recurrent erosions and attracts new vessels.
Persistent epithelial defects, melting and perforation of the cornea can occur in patients with stem cell deficiency. Corneal stem cell deficiency can be best confirmed histologically by the use of impression cytology which can detect goblet cells containing conjunctival epithelium on the corneal surface. Immunohistochemically, the absence of a cornea-type differentiation (such as absence of keratin CK3), and the presence of mucin in goblet cells, has been shown by monoclonal antibodies. Diagnosis of limbal stem cell deficiency is crucial because patients with this abnormality generally are poor candidates for conventional corneal transplantation. Lamellar or penetrating keratoplasty provides only a temporary replacement of the host's corneal epithelium because the grafted epithelial cells have a limited proliferative capacity and life span. Asymptomatic patients with partial and peripheral conjunctivalisation of the corneal surface may not require intervention.
Corneal and conjunctival epithelial cell phenotypes have been known to co-exist on the corneal surface for prolonged periods without significant extension of the conjunctivalised area nor any transdifferentiation of conjunctival epithelium into corneal phenotype of cells. [6, 7] If the visual axis or most of the corneal surface is covered with conjunctiva-like epithelium, mechanical debridement of conjunctival epithelium can allow adequate corneal epithelial healing to occur from the remaining intact limbal epithelium. In patients with total limbal stem cell deficiency, limbal auto or allotransplantation is indicated for corneal surface reconstruction. Although all techniques used in stem cell transplantation are similar in principle, the source of donor stem cells can vary. Donor tissue can be obtained from the fellow eye (i.e., limbal autograft) in cases of unilateral disease, or from a living related donor (usually gives a better tissue match) or from a cadaver donor (i.e.limbal allograft) when both eyes are affected. Many reports on these procedures have been published. There is a growing body of evidence that limbal transplantation is efficacious in replenishing the stem cells pool when deficient, promoting ocular comfort and improving vision. There is however, limited success with allo-transplants of either fresh or cultured limbal stem cells.
The rediscovery of the virtues of amniotic membrane has provided another surgical tool for restoring the damaged milieu in severely damaged ocular surface disorders. Amnion alone does not restore normal ocular surface epithelium. Residual islands of stem cells or transplanted limbal stem cells are more successful in covering the cornea surface in presence of amnion membrane. [9, 10] There are riddles yet to be solved in completely understanding and modulating the immunobiology of limbal stem cell transplantation. There is hope for a hitherto complex variety of clinical ocular disorders characterised by ocular surface failure and more are likely to fructify in near future. The large number of articles on the subject in peer reviewed mainstream journals testifies to the growing confidence of clinicians and researchers in unfolding newer breakthroughs. Although there are several reviews on the subject in recent years, the authors of the article "New perspectives in ocular surface disorders - an integrated approach for diagnosis and management" published in this issue of the journal are to be complimented for a lucid description for the benefit of practicing ophthalmologists.
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