PROBLEMS RELATED TO THE ELASTICITY OF OCULAR COATS  IN INDENTATION TONOMETRY

E. Romao, A. Lauretti-Filho, C. R. Lauretti and M.L.V. Rodrigues

Department of Ophthalmolgy, ORL and CCP, Medical School of Ribeirгo Preto, Brazil

Background: the indentation tonometry is  useful in the measurement of ocular pressure before and after the ministration of treatments, in experimental research in rabbits or other laboratory animals (mainly if the pertinent corrections are carried out). Despite this, it is necessary to consider other problems, caused by the use of this class of tonometry, as the variation of the ocular rigidity coefficient, that may occur according to the weigh adapted to the tonometer.

Objectives:  to study the variations of the ocular rigidity coefficient, according to the weight used in the indentation tonometer, as well with the injection of saline in the anterior chamber of the eye (in order to increase the intraocular pressure).

Method: Indentation tonometry was performed  (SKLAR tonometer) in 27 eyes of 27 adult rabbits, under general anesthesia, using three weights (5,5, 7,5 and 10), carrying out 3 measurements for each eye. The aqueous humor dynamics was studied by manometry, with injection of different volumes of  saline in the anterior chamber of the eye.

Results: the increase of the weight is associated with significant decrease   of ocular rigidity coefficients.  The ocular rigidity coefficient decreases  also, with he increase of the saline volume injected in the anterior chamber of the eye, significantly, until the value of 18,59 mm3.