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A total of 44 eyes of 22 ferrets were examined by B-mode ultrasonography. Four dimensions were measured: the distance from the corneal surface to the anterior lens surface (M1), the axial lens thickness (M2), the distance from the posterior lens surface to the retina (M3) and the distance from the anterior cornea to the retina (M4). The values obtained were (mean, standard deviation, range): M1: 1.31 +/- 0.16 mm (1-1.7); M2: 3.42 +/- 0.15 mm (3.2-3.7); M3: 2.26 +/- 0.11 mm (2.1-2.5); M4: 7 +/- 0.24 mm (6.4-7.7). To our knowledge this is the first description of ocular biometric measurement in the ferret. These values show little variability of ocular dimensions in ferrets.

Dexmedetomidine is an excellent option for surgery or diagnostic ocular procedures in dogs when a specific control of IOP is required. However, it must be used in combination with mydriatics in ophthalmic surgical or diagnostic procedures, which require complete dilation of the pupil.

Intraocular pressure (IOP) and tear production are commonly affected by general anaesthesia. It is necessary to have a good control of both to guarantee successful ophthalmic surgery. The purpose of this research was to evaluate if the protocol based on the administration of morphine-alfaxalone-midazolam as premedication, alfaxalone as induction and sevoflurane as maintenance, can induce changes on IOP and Schirmer's tear test (STT-1) in healthy dogs. Twenty-two adult mixed-breed dogs scheduled for an ovariohysterectomy were enrolled for the study. IOP and STT-1 were registered at baseline (T), 5 minutes (T), 10 minutes (T) and 15 minutes (T) after premedication with a morphine-alfaxalone-midazolam combination; 5 minutes (T) after induction with alfaxalone and 15 minutes (T) and 25 minutes (T) after maintenance with sevoflurane. A one-way analysis of variance was performed to analyse the difference between IOP and STT-1 over time, respectively. The present study shows a slightly statistically significant increase in IOP (P<0.05) after premedication, induction and maintenance that can be associated with this anaesthetic protocol. STT-1 showed a statistically significant reduction during all the procedures (P<0.001). These results should be taken into consideration, especially in dogs with damaged corneas, in those predisposed to glaucoma and in those due to undergo intraocular surgery. Ocular lubrication is necessary if this protocol is used.

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