Abstract
Purpose: :
To determine corneal sensitivity to selective mechanical, chemical and thermal (heat and cold) stimulation of diabetes mellitus type I (DMI) or type II patients (DMII) with diabetic retinopathy with or without history argon laser photocoagulation.
Methods: :
A medical history was obtained from all the patients, with attention to the age, sex, time of DM diagnosis, type of diabetes, time from the onset of retinopathy, type of retinopathy (proliferative or non-proliferative), and laser treatment (focal or panretinal photocoagulation) received by the patient. A complete ophthalmic examination was also performed. Corneal sensitivity to different modalities of stimulus was determined in 52 patients of both sexes (30 male, 22 female; 48.2±1.9 years old) diagnosed of DMI (n=35) or DMII (n=17) at least one year prior to the study. A group of 18 age and sex matched healthy subjects served as a control group. Slit-lamp examination showed no corneal alterations in DM patients. Stimulation of the cornea was performed using a Belmonte gas esthesiometer (Deriva Global, S.L.). Mechanical (air at 0 to 200ml/min flow), chemical (0 to 80% CO2 in air), heat (changing corneal temperature between 0 and +2.0ºC) and cold (changing corneal temperature between 0 and -4.5ºC) 3s-stimuli were applied to the central cornea and sensitivity threshold to each modality of stimulus was determined.
Results: :
Diabetic patients responded to mechanical (100%), chemical (100%), heat (66%) and cold (98%) stimulation of the central cornea. Mechanical (p<0.01), chemical (p<0.001), heat (p<0.001) and cold (p<0.001) thresholds were significantly higher in DM patients than in healthy subjects. No significant correlation was found between sensitivity thresholds and the type of DM, time from DM diagnosis, type of retinopathy or its time from diagnosis. Mechanical threshold was slightly higher and chemical threshold significantly increased (p<0.05) in patients subjected to photocoagulation compared to those that had not undergone the laser treatment.
Conclusions: :
Corneal sensitivity thresholds to selective mechanical, chemical, heat and cold stimulation were increased in diabetic patients. These sensory alterations appear relatively early in both types of DM. Laser photocoagulations seems to further impair corneal sensitivity.
Keywords: innervation: sensation • diabetic retinopathy