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Summary

Intraocular pressure (iop) was measured in 73 eyes of 37 clinically normal cats with 2 applanation tonometers (Tono-Pen and Mackay-Marg) and the Schiotz indentation tonometer, using the 5.5- and 7.5-g weights. Statistically, the Tono-Pen tonometer underestimated iop compared with the values obtained by use of the Mackay-Marg tonometer (P < 0.0001) and the Schiotz tonometer, with either weight and either the human (P < 0.01) or the canine (P < 0.0001) calibration tables. Estimates of iop using the human calibration table and either the 5.5− or 7.5-g weight were not significantly different from each other or from those obtained with the Mackay-Marg tonometer. Schiotz measurements obtained with either weight and converted using the canine calibration table were not only significantly (P < 0.0001) different from each other, but were also clinically and significantly (P < 0.0001) higher than measurements obtained with the Tono-Pen and Mackay-Marg tonometers or the Schiotz tonometer, using the human calibration table and either weight. Approximately three quarters of clinically normal cats had an iop ≥ 30 mm of Hg when Schiotz tonometer measurements were converted with the canine conversion table. The human calibration table was the most clinically useful table for converting Schiotz measuremenftrsom clinically normal feline eyes to estimates of iop in mm of Hg. Normal mean (±sd) feline readings with the Schiotz tonometer and the 5.5-g weight was 3.9 ± 1.4 tonometer scale units (range, 1.0 to 7.5; 95% confidence interval [ci], 1.1 to 6.7). Converted mean (±sd) iop estimates, using the 5.5-g weight in normal feline eyes, was 21.6 ± 5.0 mm of Hg (range, 11.2 to 34.5; 95% ci, 11.6 to 31.6) with the human conversion table, and 35.0 ± 5.8 mm of Hg (range, 23.0 to 49.3; 95% ci, 23.4 to 46.6) with the canine conversion table

Free access
in Journal of the American Veterinary Medical Association

Summary

Intraocular pressure (iop) was measured in 114 eyes of 57 clinically normal dogs with 2 applanation tonometers (Tono-Pen and Mackay-Marg) and the Schiotz indentation tonometer, using the 5.5- and 7.5-g weights. Significant differences were not detected between measurements obtained with the Tono-Pen and Mackay-Marg tonometers the Mackay-Marg and Schiotz tonometers using either weight and conversion with the human calibration table, or the Tono-Pen and Schiotz tonometers using the 7.5-g weight and the human calibration table. Values obtained by use of the Tono-Pen tonometer were significantly less (P < 0.005) than values obtained with the Schiotz tonometer when a 5.5-g weight and the human calibration table were used, but the amount was clinically unimportant. Estimates of iop using the Schiotz tonometer and the canine calibration table, and either the 5.5− or 7.5-g weight were clinically and significantly much higher (P < 0.0001) than estimates obtained with the Tono-Pen, Mackay-Marg, or Schiotz tonometers, using the human calibration table and either weight. Sixty to 70% of clinically normal dogs had an iop ≥ 30 mm of Hg when Schiotz scale measurements were converted with the canine conversion table. For clinically normal dogs, the human calibration table was the most clinically useful table for converting Schiotz tonometer measurements to mm of Hg. Normal mean (± sd) canine readings with the Schiotz tonometer and the 5.5-g weight was 4.9 ± 1.5 tonometerscale units (range, 2 to 11; 95% confidence interval, 1.9 to 7.9). Converted means (± sd) for clinically normal dogs with the 5.5-g weight were 18.0 ± 4.1 mm of Hg (range, 6 to 29; 95% confidence interval, 9.8 to 26.2) with the human calibration table, and 30.9 ± 4.7 mm of Hg (range, 17 to 43; 95% confidence interval, 21.5 to 40.3) with the canine conversion table.

Free access
in Journal of the American Veterinary Medical Association

Summary

Comparisons were made of measurements obtained in horses, using 2 applanation tonometers in vivo and in vitro. In vitro comparisons indicated that although neither instrument accurately recorded intraocular pressure (iop), compared with manometric measurements, results of both instruments indicated linear digression from manometric iop values that could readily be corrected, thereby accurately estimating iop in horses. For tonometer 1 (MacKay-Marg), calculated actual lop = 1.48 − 0.9 mm of Hg; and for tonometer 2 (Tono-Pen), calculated actual iop = 1.38 + 2.3 mm of Hg. The coefficients of determination (r2) values were markedly high (0.99 for both equations). In vivo comparisons in clinically normal horses did not reveal significant differences in measured 10P between the 2 instruments, and iop was not altered from baseline after auriculopalpebral nerve block. Mean (± sd) iop in clinically normal horses was 23.5 ± 6.10 mm of Hg and 23.3 ± 6.89 mm of Hg, for tonometers 1 and 2, respectively.

Free access
in American Journal of Veterinary Research

SUMMARY

Comparisons of the MacKay-Marg and Tono-Pen applanation tonometers in open and closed in vitro systems were made for the eyes of cats. Both instruments significantly underestimated intraocular pressure (iop) vs direct manometry (P < 0.001), but in readily predictable manner, with high coefficients of determination (r 2 = 0.99). For tonometer 1 (MacKay-Marg), calculated actual iOP = 1.36 × (MacKay-Marg measurement) − 1.67 mm of Hg; and for tonometer 2 (Tono-Pen), calculated actual iop = 1.37 × (Tono-Pen measurement) + 0.8 mm of Hg, using measurements from 11 enucleated eyes. In vivo comparisons were initially made in 81 clinically normal eyes (n = 41 cats) by applying the Tono-Pen first followed by the MacKay-Marg. Compared with the MacKay-Marg, the Tono-Pen significantly (P < 0.001) underestimated iOP in these cats. When the order of tonometer applanation was subsequently reversed in 73 clinically normal eyes (n = 37 cats) the Tono-Pen again significantly (P < 0.001) underestimated iOP, compared with the MacKay-Marg. Alterations in tonometer order did not result in significant differences in measured iOP for the MacKay-Marg when compared with itself, but Tono-Pen measurements were significantly (P < 0.05) less when its use followed, rather than preceded, that of the MacKay-Marg. Mean (± sd) iop in clinically normal cats when each tonometer was used first was 22.6 ± 4.0 mm of Hg (range, 14 to 32 mm of Hg) for the MacKay-Marg and 19.7 ± 5.6 mm of Hg (9 to 31 mm of Hg) for the Tono-Pen. The mean (± sd) absolute value of the differences between MacKay-Marg measurements and those obtained by use of the Tono-Pen was 3.2 ± 3.1 (range, 0 to 13 mm of Hg difference).

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of cyclophotocoagulation via administration of 100 J with a neodymium: yttrium aluminum garnet (Nd:YAG) laser on corneal touch threshold (CTT), intraocular pressure (IOP), aqueous tear production, and corneal nerve morphology in eyes of dogs.

Animals—15 dogs.

Procedure—Noncontact Nd:YAG laser was transsclerally applied (10 applications; 25 W for 0.1 seconds for each application to each of 4 quadrants) to the ciliary body of the left eye of 15 dogs; the right eye was the control eye. Corneal integrity, CTT, tear production as measured by the Schirmer tear test (STT), and IOP were evaluated for 14 days following laser treatment. On day 14, dogs were euthanatized, eyes harvested, and corneas stained with gold chloride. Major nerve bundles were analyzed by use of a drawing tube attached to a light microscope, and maximum diameters were measured by use of image analysis software.

Results—All laser-treated eyes had significantly higher CTT values, compared with control eyes. Six of 15 laser-treated eyes developed ulcerative keratitis. On most days, IOP was significantly lower in laser-treated eyes in both morning and evening. Laser-treated eyes had a significant decrease of approximately 1 nerve bundle/corneal quadrant. Values for STT or nerve bundle diameters did not differ significantly.

Conclusion and Clinical Relevance—Administration of 100 J with a Nd:YAG laser effectively reduced IOP while increasing CTT and caused a significant decrease in number, but not diameter, of major corneal nerve bundles. Nerve damage and corneal hypoesthesia are etiologic factors in ulcerative keratitis following Nd:YAG cyclophotocoagulation. (Am J Vet Res 2002;63:906–915)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To assess the effects of topically applied 2% dorzolamide hydrochloride–0.5% timolol maleate ophthalmic solution (DHTM) on incidence and severity of postoperative ocular hypertension (POH; ie, intraocular pressure [IOP] > 25 mm Hg) in dogs undergoing cataract extraction by phacoemulsification.

DESIGN Randomized, masked, controlled study.

ANIMALS 103 dogs (180 eyes).

PROCEDURES Pertinent history, signalment, and ophthalmic examination findings were recorded. Dogs received 1 drop of DHTM or sham treatment solution (sterile, buffered, isotonic eye drops) in both eyes 14 hours and 2 hours before anesthetic induction and at the time of corneal incision closure (ie, end of surgery); IOPs were assessed by rebound tonometry 2, 4, 6, and 8 hours after surgery and between 7:30 and 8:00 am on the following day. Dogs with IOPs of 26 to 45 mm Hg received 1 drop of 0.005% latanoprost solution topically; the surgeon's treatment of choice was used for dogs with IOPs > 45 mm Hg. Incidence of POH and postoperative IOPs were compared between treatment groups.

RESULTS DHTM treatment resulted in significantly lower incidence of POH than did sham treatment at the level of the dog (18/53 [34%] vs 31/50 [62%]) and the eye (24/94 [26%] vs 42/86 [48%]). Mean IOP did not differ between groups at the time of POH detection. The DHTM-treated eyes that developed POH were significantly more likely to have a 1-hour follow-up IOP < 25 mm Hg after latanoprost administration than were sham-treated eyes (19/25 [76%] vs 18/35 [51%]; OR, 3.87).

CONCLUSIONS AND CLINICAL RELEVANCE Multidose perioperative administration of DHTM in dogs undergoing phacoemulsification reduced the incidence of POH and improved responsiveness of POH to latanoprost treatment.

Full access
in Journal of the American Veterinary Medical Association

Summary

A white Bengal tiger was determined to have a central retinal lesion and a central visual defect. Because of the known association between feline central retinal degeneration (crd) and taurine deficiency in domestic cats, plasma concentrations of taurine were measured in this tiger. Serum concentrations of taurine, methionine, and cystine also were measured in white Bengal tigers, orange Bengal tigers, taurine-sufficient domestic cats, and taurine-deprived and tissue-taurine-depleted visually impaired cats with crd. Hepatic and brain enzymes responsible for taurine synthesis were identified in tissue specimens from an orange Bengal tiger. Serum taurine concentrations were lower in white vs orange tigers, but were not as low as those in cats with crd. Thus, we concluded that taurine depletion did not account for the central retinal lesion in the white Bengal tiger.

Free access
in Journal of the American Veterinary Medical Association