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- Author or Editor: Paul A. Gerding Jr x
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Objective—To determine whether an applanation tonometer and rebound tonometer can be used to detect similar intraocular pressure (IOP) measurements in eyes of dogs undergoing phacoemulsification.
Animals—24 dogs (40 eyes) undergoing elective phacoemulsification.
Procedures—IOP measurements were obtained from each eye by use of both the rebound tonometer and applanation tonometer. Central corneal thickness was measured by use of an ultrasonic pachymeter 3 hours before surgery and 2 and 24 hours after surgery. Statistical analysis was performed by use of paired t tests.
Results—Mean ± SD IOP 3 hours before surgery, 2 hours after surgery, and 24 hours after surgery was 11.9 ± 4.7 mm Hg, 15.5 ± 11.7 mm Hg, and 10.9 ± 6.7 mm Hg, respectively, as measured with the rebound tonometer and 12.2 ± 5.3 mm Hg, 15.7 ± 12.5 mm Hg, and 12.4 ± 5.4 mm Hg, respectively, as measured with the applanation tonometer. Measured IOP did not differ significantly between the 2 tonometers 3 hours before surgery and 2 hours after surgery, but measured IOP differed significantly between the tonometers 24 hours after surgery.
Conclusions and Clinical Relevance—Use of a rebound tonometer underestimated IOP, relative to results for use of an applanation tonometer, by 1.65 mm Hg in eyes 24 hours after phacoemulsification. Caution should be used when IOP measurements obtained with a rebound tonometer are in the high part of the reference range, and verification of these values with an applanation tonometer would be advised.
Objective—To evaluate effects of intracameral injection of preservative-free 1% and 2% lidocaine hydrochloride solution on the anterior segment of the eyes in dogs.
Animals—16 adult healthy dogs (8 male and 8 female) judged to be free of ocular disease.
Procedure—Dogs were randomly assigned to 2 groups of 8 dogs each. Group 1 dogs received an intracameral injection of 0.10 mL of preservative-free 1% lidocaine solution in the designated eye, and group 2 dogs received 0.10 mL of preservative-free 2% lidocaine solution in the designated eye. After injection, intraocular pressure was measured every 12 hours for 48 hours and then every 24 hours until 168 hours after injection. Slit-lamp biomicroscopy was performed preceding intracameral injection, 8 hours after injection, and then every 24 hours until 168 hours after injection. Ultrasonic pachymetry and specular microscopy were performed preceding intracameral injection and 72 and 168 hours after injection. Corneal thickness and endothelial cell density and morphology were compared with baseline measurements.
Results—No significant differences were found in intraocular pressure, corneal thickness, endothelial cell density, and morphologic features in either group, compared with baseline. A significant difference in aqueous flare was found for treated and control eyes 8, 24, and 48 hours after injection, compared with baseline. No significant difference in aqueous flare was found between treated and control eyes within either group.
Conclusions and Clinical Relevance—No adverse ocular effects were detected after intracameral injection of preservative-free 1% or 2% lidocaine solution; thus, its use would be safe for intraocular pain management in dogs. (Am J Vet Res 2004;65:1325–1330)
Objective—To determine the electrodiagnostic and histologic response of short-term increases of intraocular pressure (IOP) on transient pattern electroretinograms (PERG) and flash electroretinograms (FERG) in the eyes of dogs.
Animals—8 healthy mixed-breed dogs.
Procedure—Transient PERG and FERG waveforms were recorded from dogs (while anesthetized) as IOP was increased from baseline (7 to 19 mm Hg) to 90 mm Hg. One hundred mean PERG responses and a single FERG response were recorded at each step during 3 recording sessions. Globes of each dog were enucleated after euthanasia on posttreatment day 7 and evaluated by a pathologist.
Results—Increases in spatial frequency resulted in decreased amplitudes of N2 (second negative PERG peak). Increases in IOP resulted in decreases in all 3 PERG waveforms and the FERG waveform. All values began to return to baseline after short-term increases in IOP on day 0, and waveforms were not significantly different on posttreatment days 3 and 7.
Conclusions—Data suggest that short-term increases in IOP affect PERG and FERG waveforms, and PERG waveforms are more sensitive to increases in IOP. Differences were not detected between treated and control eyes on histologic examination. Further studies are necessary to determine at what IOP permanent damage to ganglion and photoreceptor cells will develop and whether PERG is a reliable clinical diagnostic technique for use in dogs to reveal retinal damage that is secondary to increased IOP prior to changes in waveforms generated by FERG in dogs. (Am J Vet Res 2000;61:1087–1091)