Ocular diagnostic and therapeutic techniques in food animals

A Modified Schirmer Tear Test in Clinically Normal Horses: Measurement at 30 Seconds versus 60 Seconds

This study sought to compare the Schirmer Tear Test (STT)-1 results at 30 (STT30) versus 60 (STT60) seconds in healthy horses. This study included a total of 56 healthy horses. STT-1 was performed in both eyes, right eye first, and the wetting lengths were measured in STT30 and STT60. To evaluate the reduction of the initial reflex phase, the wetting length velocity was measured during the first 30 seconds. The effects of eye, age, weight, sex, and ambient temperature and humidity on STT values were evaluated. Mean (standard deviation) STT30 and STT60 were 19.06 (3.88) and 24.26 (4.50) mm. There was a linear correlation between the STT 30 and STT60, expressed according to the following equation: STT60 = 2.20 + 1.18 × STT30 (P = .001). STT30 or STT60 values did not vary between the sexes or correlate with age, weight, ambient temperature, or humidity. In conclusion, STT30 allows for an accurate, reliable, and applicable diagnosis of tear production compared with the standard STT60 value. The proposed method is shorter and may be a suitable alternative to the 1-min test.

The effect of environmental and biological factors on STT I and normal total tear protein concentration in Japanese black calves

To identify reference values for the Schirmer tear test I (STT I) in Japanese black cattle, investigate the effects of variables (sex, age, time of day, and environment in the barn including environmental temperature, humidity, illuminance, and ammonia concentration) on tear production, and determine total tear protein concentration. One-hundred-and-thirty-seven Japanese black cattle (67 females and 70 males, age 3–90 days) were evaluated. The mean STT I values was 18.9 ± 2.9 mm/min (n=263) and significant effects were age and ammonia concentration in the barn. Mean total tear protein concentration was 1.18 ± 0.30 mg/ml in healthy cattle older than 15 days (n=38). It was suggested that age and ammonia concentration are related to fluctuation of tear volume.

Ocular pharmacology

Application of sound ocular therapeutic principle is more difficult in food animals than most other species. Financial or husbandry constraints limit the practitioner's ability to use the entire range of ocular drugs available or to use them with adequate frequency. These problems may be dealt with by using systemically administered drugs when effective or by employing vehicles or delivery techniques that necessitate minimal dosing frequency. By far the most important medically treatable eye disease encountered in food animal practice is IBK. Effective therapies include systemic administration of long-acting oxytetracycline, subconjunctival administration of a variety of antibiotics, or topical application of benzathine cloxacillin. Infectious conjunctivitis in sheep and goats due to a variety of agents may be treated successfully with tetracycline in most cases. Conjunctivitis and keratitis secondary to IBR virus usually are given supportive therapy only, although specific antiviral drugs have been used in the treatment of herpetic eye disease in other species. Anterior uveitis is best treated by corticosteroid and mydriatic therapy in addition to treatment of the underlying cause, if identified.

Management of intraoperative and postoperative anesthetic complications in ruminants and swine

Complications that can occur during and following anesthesia in ruminants and swine are discussed. Because many of these complications can be life-threatening, they must be avoided to allow provision of safe general anesthesia. Emphasis is placed on prevention and recognition of these complications and the institution of therapy when they do occur.