Effects of intracameral injection of epinephrine and 2% lidocaine on pupil diameter, intraocular pressure, and cardiovascular parameters in healthy cats.

Objectives: To investigate the effects of the intracameral injection of epinephrine and two doses of 2% lidocaine on pupil diameter (PD), intraocular pressure (IOP), heart rate (HR), and mean arterial pressure (MAP) in healthy cats.

Methods: Five treatment groups were formed (10 cats/each). Animals received 0.2 mL of epinephrine, 0.2 or 0.3 mL of 2% lidocaine, or 0.2 mL of BSS. Cats were anesthetized, and all solutions were injected intracamerally. PD, IOP, HR, and MAP were assessed at baseline, following anterior chamber paracentesis (T0), and at every 5 minutes, until anesthesia was terminated (T60). PD and IOP continued to be assessed for 2 additional hours during recovery from anesthesia. In another group, cats were not anesthetized and one of the eyes was treated with one drop of 0.5% tropicamide to check for maximal pupil diameter.

Results: Faster onset and longer duration of sufficient mydriasis (>10 mm) were observed in epinephrine treatment group, when comparing with cats treated with both doses of lidocaine. Eyes treated with epinephrine achieved the largest maximum pupil diameter (mm) when comparing with eyes treated with 0.3 mL of lidocaine (11.01 ± 0.16), tropicamide (10.66 ± 0.17), and 0.2 mL of lidocaine (10.23 ± 0.12) (P < .0001). In all groups, IOP decreased significantly at T0, but tended to return to baseline at T60. HR and MAP did not change significantly during time and among treatments.

Conclusions: The intracameral injection of 0.2 mL of 1:100 000 epinephrine and 0.3 mL of 2% lidocaine can be used as an alternative to tropicamide in healthy cats. Both treatments produced satisfactory and long-lasting mydriasis without adverse effects on IOP, HR, and MAP.