To determine the influence of topical anaesthetic drops, age and central corneal thickness (CCT) in the determination of intraocular pressure (IOP) by non contact tonometry (NCT). · METHODS: Ninety-three eyes from 47 patients were examined for CCT and IOP by NCT before and after the instillation of topical anaesthetic drops. · RESULTS: Average age was 66.4 (SD 16, range 34 to 88 years-of-age). Thirty one patients were female and 16 were male. Average basal IOP was 16.0mmHg (SD 4.0, range 8.5 to 26.1). IOP one minute after topical anesthesia instillation was 15.0mmHg (SD 3.8, range 7.7 to 26.7), and 14.9mmHg (SD 3.9, range 7.6 to 26.3) five minutes after the instillation. The differences were statistically significant for the 0 to 1 minute lapse(P =0.0007) and for the 0 to 5 minute lapse (P = 0.0003), but not for the 1 to 5 minute lapse (P =0.27) (Student's t test for paired data). Average CCT before topical anaesthetic drops was 565.4 microns. Simple linear regression analysis demonstrated absence of significant variation between age and IOP changes and between CCT and IOP changes. · CONCLUSION: Our study confirms that the instillation of topical anaesthetics causes a reduction in IOP, which is progressive during the first 5 minutes after instillation. This IOP reduction does not seem to be associated with basal CCT or age.