This is an interesting article in that it documents that diabetic patients have morphological surface cell changes as measured by impression cytology. Patients were qualified as not having dry eye on the basis of a McMonnies symptom questionnaire. Given that over 50% of diabetic patients have reduced corneal sensation, it is likely that many of these patients thought not to have dry eye actually had it. The loss of sensation and dry eye is thought to be, at least in part, related to the peripheral neuropathy of diabetes affecting the ocular surface.
Also of note is that the Schirmer test and tear breakup time were normal in 2/3rds of the patients and corneal and conjunctival staining normal in 95% of patients in this study. These results further confirm the recently reported insensitivity of these tests to accurately identify patients with mild to moderate dry eye. Tear osmolarity is the only generally available objective test which has been shown to accurately diagnose dry eye and measure disease severity over the entire range of disease.
Study of tear function and the conjunctival surface in diabetic patients; Figueroa-Ortiz LC, Jiménez Rodríguez E, García-Ben A, García-Campos J; Archivos de la Sociedad Espanola de Oftalmologia 86 (4), 107-112 (Apr 2011)
OBJECTIVES:
This study was performed to investigate whether different grades of diabetic retinopathy correlate with tear and ocular surface function in diabetic patients without subjective symptoms of dry eye.
METHODS:
A total of 129 eyes of 72 patients without dry eye, assessed using McMonnies questionnaire were recruited to the study. The tear film and ocular surface were evaluated using the Schirmer test, tear film break-up time (BUT), fluorescein and lissamine green staining test, and conjunctival impression cytology. The results were analysed.
RESULTS:
A normal Schirmer test and BUT was obtained in 51 and 67% of the eyes of diabetics patients, respectively. Fluorescein and lissamine green staining were negative in 81 and 95% of the eyes. The area and density of goblet cells was 580.46±370μm(2) and 235.58±109.03 goblets cell/mm(2), respectively. CONCLUSIONS: Diabetic retinopathy patients without subjective symptoms of dry eye and normal Schirmer and BUT test showed pathological grades of squamous metaplasia.
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