Effect of four local anesthetics (tetracaine, bupivacaine, lidocaine and proparacaine) on intraocular pressure in rabbits- Comparison of an applanation and a rebound tonometer

The type of device used, the type of local anesthetic agents, and the animal species may affect the intraocular pressure (IOP). Therefore, in order to determine these issues, the effects of four local anesthetics were investigated in 10 adult rabbits by ICare TA01i and Tono-Pen Vet tonometers. In the right eye of half of the rabbits and in the left eye of the other half of the rabbits, one drop of tetracaine was instilled. The IOP in each rabbit was measured using two tonometers, ICare and Tono-Pen Vet, before and each 5 minutes until 40 minutes later. The effects of other drugs were also studied at least with one-week interval. Based on the results of ICare tonometer, tetracaine significantly reduced the IOP immediately and 25 minutes after instillation. IOP changes after instillation of bupivacaine, lidocaine and proparacaine were not significant at any time compared to baseline values (p > 0.05). Based on the results of Tono-Pen Vet tonometer, all drugs reduced the IOP immediately after use; however, the effects of bupivacaine and lidocaine on IOP were much lower than that of tetracaine and proparacaine. The average duration of corneal anesthesia were 20, 15.5, 7.5 and 21 minutes for tetracaine, bupivacaine, lidocaine, and proparacaine, respectively. It is concluded that IOP reduction by local anesthetics when Tono-Pen Vet is used is much greater than the ICare tonometer measurements. Also, the reduction of IOP with each of the devices when tetracaine or proparacaine is used is greater than when bupivacaine or lidocaine is used.