Evaluation of filtering bleb function by thermography

Aim: To determine whether thermography can be used to evaluate bleb function. Methods: The surface temperatures of filtering blebs from 39 eyes of 33 post-trabeculectomy patients were measured using thermography. We introduced a new parameter: the temperature decrease in the filtering bleb (TDB) where TDB = (mean temperature of the temporal and nasal bulbar conjunctiva)-(temperature of the filtering bleb). The eyes were classified into good and poor intraocular pressure (IOP) control groups according to the patients' postoperative IOP. The morphological appearance of the filtering blebs were classified by slit-lamp images according to the Indiana Bleb Appearance Grading Scale. The differences in TDB were analysed statistically. Results: Mean overall scores were as follows. The TDB were 0.54 (SD 0.20) degrees C and 0.21 (SD 0.18)degrees C for the good and poor IOP control groups, respectively. The difference between the TDB of the two IOP control groups was significant (p < 0.0001), but there was no significant relationship between morphological classification and TDB. Conclusions: Thermographic measurements suggest that functional blebs have lower temperatures than nonfunctional blebs, and their morphological appearances are not affected by their temperature. Thermography may be useful for the evaluation of bleb function.