Abstract
We are indebted to Dr Zaidi for raising an interesting question, whether ultraviolet radiation could be a possible cause of idiopathic limbal stem cell (SC) deficiency. Ultraviolet radiation has been implicated as a cause of pterygium, a disease known to manifest focal limbal SC deficiency.1Tseng S.C Concept and application of limbal stem cells.Eye. 1989; 3: 141-157Crossref PubMed Scopus (509) Google Scholar, 2Tseng S.C Lee S.B Li D.Q Limbal stem cell deficiency in the pathogenesis of pterygium.in: Taylor H.R Pterygium. Kugler Publications, The Hague2000: 41-55Google Scholar This may be explained by an in vivo demonstration of albedo focus of incident light on the nasal limbal sclera.3Coroneo M.T Albedo concentration in the anterior eye a phenomenon that locates some solar diseases.Ophthalmic Surg. 1990; 21: 60-66PubMed Google Scholar This is also supported by a theoretical calculation showing that ultraviolet radiation might be concentrated at the nasal limbal area.4Kwok L.S Coroneo M.T A model for pterygium formation.Cornea. 1994; 13: 219-224Crossref PubMed Scopus (126) Google Scholar For the following reasons, we do not believe our reported cases of idiopathic limbal SC deficiency are caused by ultraviolet radiation. First, unlike pterygium, we noted that conjunctivalization of the cornea occurred predominantly from the superior limbal area, followed by the inferior limbal area,5Espana E.M Grueterich M Romano A.C et al.Idiopathic limbal stem cell deficiency.Ophthalmology. 2002; 109: 2004-2010Abstract Full Text Full Text PDF PubMed Scopus (54) Google Scholar which are highly protected and unlikely to be exposed to ultraviolet radiation. Only 2 of 7 patients had nasal corneal conjunctivalization. Second, the majority of our patients were not from areas with high ultraviolet exposure such as Miami or the Caribbean. Therefore, we believe that the etiology of our reported patients with limbal SC deficiency remains poorly known—that is, idiopathic.
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