SUMMARY
Applanation tonometry has some disadvantages such as potencial risk of infection, need of anesthetic eye drops and possibility of being influenced by hipojluorescence or hiperjluorescence of lacrimal film, corneal thickness and astigmatism. Non-contact tonometry offers advantages such as small risk of infection and ease of use.
We analysed 80 eyes of patients from the Glaucoma Service and from the General Clinic of the Ophthalmology Service of Hospital de Clinicas de Porto Alegre, to compare noncontact tonometry with applanation tonometry. Intraocular pressure (IOP) was evaluated with the manual applanation tonometer (Perkins) and with the non-contact tonometer (Topcon CT-20). Keratometry and paquimetry were also evaluated.
This study showed good correlation between two tonometers, although non-contact tonometer had the tendency of registering predominantly higher pressures. This difference was statistically significant only when IOP was above 20 mmHg in patients with glaucoma.
Keratometry showed a positive correlation with applanation tonometer (r = 0.22; P < 0.05) and paquimetry (thicker corneas) showed a positive correlation with non-contact tonometry (r = 0.34; P < 0.001).
We suggest that measures above 20 mmHg with non-contact tonometer should be confirmed by applanation tonometry, to avoid mistaken or precipitated clinicai decisions. Intraocular measures below 20 mmHg do not seem to offer false-negative results.
Key-words:
Applanation tonometry; Non-contact tonometry; Glaucoma