[Corneal epithelium squamous metaplasia determination as diagnostic factor in limbal deficiency].

Purpose: To determine the correlation between the squamous metaplasia grade of the corneal surface and the clinical severity of the limbal deficiency in patients with this disorder.
Methods: We studied 98 eyes of patients with limbal deficiency by impression cytology. These patients were divided into four groups in relation to their clinical severity: 14 eyes had no symptoms, 34 eyes showed a mild grade of limbal deficiency, 28 eyes had a moderate grade and 22 eyes had severe limbal deficiency. Corneal cytology was performed in each patient. Cellular size, nuclear size, nuclear changes and the nuclear-cytoplasmic (N:C) ratio were defined in corneal epithelial cells, in addition to evaluation for the presence of goblet cells in the corneal epithelium.
Results: In patients with limbal deficiency without symptoms, we found that the cellular size was 477 (SD140) microm2 and the N:C ratio was 1:5.25 (SD1.5). In patients with mild limbal deficiency, the cellular size was 764 (SD122.6) microm2 and the N:C ratio was 1:8.2 (SD1.4). These patients did not show corneal conjunctivalization. In patients with moderate limbal deficiency the cellular size was 1,162 (SD340.2) microm2 and the N:C ratio was 1:13.2 (SD3.6). Some patients showed corneal conjunctivalization that was defined by the presence of goblet cells in the corneal epithelium. In patients with severe limbal deficiency, the cellular size was 2,036 (SD382) microm2 and the N:C ratio was 1:23.6 (SD4.0). Corneal conjunctivalization was present in all of these patients.
Conclusions: There was a correlation between limbal deficiency severity and squamous metaplasia grade defined by impression cytology. Impression cytology was very useful for the diagnosis of cases of mild or subclinical limbal deficiency.