Comparison of Rebound and Applanation Tonometry in Eyes With Focal Corneal Edema.

Rebound tonometry is more reliable than applanation in feline corneal edema; measure clear cornea when possible.

This study evaluated how focal corneal edema affects intraocular pressure (IOP) measurements obtained with handheld tonometers commonly used in feline ophthalmology. In vivo testing on 10 glaucomatous cat eyes compared rebound tonometers (TONOVET Plus and TONOVET) with applanation tonometry (Tono-Pen Vet) in areas of corneal edema versus clear cornea. Ex vivo cannulation studies on four additional feline eyes provided reference manometric pressures from 5-70 mmHg. Results demonstrated that rebound tonometry readings were 4.0 mmHg lower in edematous regions, while applanation readings were 13.0 mmHg higher compared to clear cornea. Rebound tonometers maintained acceptable accuracy and precision in clear cornea but showed degradation with edema. Applanation tonometry significantly underestimated high IOPs and performed worse overall. All tonometers demonstrated reduced precision in edematous cornea, with applanation showing significantly greater precision loss. The findings suggest rebound tonometry is more reliable in edematous cornea, though obtaining measurements from clear corneal regions when clinically feasible is recommended for improved accuracy in feline patients.

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