Schirmer tear test, phenol red thread tear test, eye blink frequency and corneal sensitivity in the guinea pig

OBJECTIVE: To establish reference values for Schirmer tear tests (STT) I and II, phenol red thread (PRT) tear test and eye blink frequency, and to determine corneal sensitivity for normal guinea pigs. ANIMALS STUDIED: One hundred and eight eyes of 54 adult Duncan-Hartley guinea pigs. PROCEDURE: Schirmer tear test (STT) I and then STT II were performed in 36 guinea pigs. PRT and STT I were compared in 18 adult Duncan-Hartley guinea pigs. Corneal sensitivity was determined in 23 guinea pigs by evaluating the corneal touch threshold (CTT) of five different regions using a Cochet-Bonnet esthesiometer. Eye blink frequency was measured in 10 guinea pigs over a period of 20 min and in 17 guinea pigs over a period of 10 min. RESULTS: Mean STT I was 0.36 mm +/- 1.09 mm (wetting/min) and mean STT II was 0.43 mm +/- 1.29 mm (wetting/min). There was no significant difference between mean STT I and mean STT II (P = 0.79). The mean PRT-value was 16 +/- 4.7 mm (wetting/15 s), and the mean STT I-value in the same guinea pigs was 0.6 +/- 1.83 mm (wetting/min). Corneal sensitivity was significantly higher in the center than in the four limbal regions. The mean CTT for central, ventral, nasal, temporal and dorsal regions was 2, 1.7, 1.7, 1.7 and 1.6 cm or 3.7, 5.2, 5.6, 5.7 and 6.4 g/mm(2), respectively. Eye blink frequency was between two to five (mean 3.4 +/- 1.04) blinks per eye over 20 min in guinea pigs in their home environment, while in handheld and restrained guinea pigs eye blink frequency showed a variation between 0 and 17 blinks per eye (mean 3.24 +/- 3.64 blinks per eye) over 10 min. CONCLUSIONS: As there were no significant differences between STT I and STT II results, reflex tear secretion in the guinea pig may not exist. The most likely explanation is a lower corneal sensitivity in the guinea pig than in other species, such as cats, dogs and horses. Because of the small amount of tears, PRT is the preferred test for tear measurement in the guinea pig.     

Evaluation of results for Schirmer tear tests conducted with and without application of a topical anesthetic in clinically normal dogs of 5 breeds

OBJECTIVE: To evaluate, for clinically normal dogs, results of Schirmer tear tests in eyes without topical anesthetic (STT) and to detect differences associated with breed, sex, age, day, and time of day in eyes in which STT was performed after use of topical anesthetic (STTa). ANIMALS: 41 Beagles, 43 Labrador Retrievers, 25 Golden Retrievers, 26 English Springer Spaniels, and 22 Shetland Sheepdogs. PROCEDURE: Beagles had STT and STTa values measured twice daily for 5 days. Client-owned dogs of 4 other breeds had STT and STTa values measured once. RESULTS: Mean +/- SD values of Beagles for STT and STTa were 20.2 +/- 2.5 and 3.8 +/- 2.7 mm/min. Mean values for STT and STTa were as follows: Labrador Retriever, 22.9 +/- 4.1 and 9.6 +/- 3.8 mm/min; English Springer Spaniel; 20.7 +/- 3.2 and 5.4 +/- 3.4 mm/min; Golden Retriever, 21.8 + 3.7 and 8.8 +/- 3.1 mm/min; and Shetland Sheepdog, 15.8 +/- 1.8 and 3.6 +/- 2.8 mm/min. Overall mean values for STT and STTa were 20.2 +/- 3.0 and 6.2 +/- 3.1 mm/min. Differences for STT and STTa were detected among breeds, but significant differences were not associated with sex or age within each breed or in overall values for all dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results for the STT reported here compare favorably with reported values, except for results of Shetland Sheepdogs; however, results for the STTa differ dramatically from reported values. Clinicians should consider effects attributable to breed when evaluating results of STT and STTa in dogs.     

Results of diagnostic ophthalmic testing in healthy guinea pigs

OBJECTIVE-To report values for tear production, central corneal touch threshold (CTT), and intraocular pressure (IOP) in healthy guinea pigs and determine results of aerobic bacterial culture and cytologic examination of conjunctival swab specimens. DESIGN-Cross-sectional study. ANIMALS-31 Healthy guinea pigs (62 eyes) of various ages and breeds. PROCEDURES-Tear production was measured by the phenol red thread tear test (PRT) and Schirmer tear test (STT) before and after topical anesthetic application, CTT was measured with an esthesiometer, and IOP was measured by applanation tonometry. RESULTS-Combining data from all eyes, mean +/- SD PRT values before and after topical anesthetic administration were 21.26 +/- 4.19 mm/15 s and 22.47 +/- 3.31 mm/15 s, respectively, and mean IOP was 18.27 +/- 4.55 mm Hg. Median STT values before and after topical anesthetic administration were 3 mm/min (range, 0 to 12 mm/min) and 4 mm/min (range, 0 to 11 mm/min), respectively, and median CTT was 2.0 cm (range, 0.5 to 3.0 cm). Values did not differ between eyes for any test, but significant differences were identified for PRT values between males and females and between values obtained before and after topical anesthetic administration. Common bacterial isolates included Corynebacterium spp, Streptococcus spp, and Staphylococcus spp. Cytologic examination of conjunctival swab specimens revealed mainly basal epithelial cells; lymphocytes were common. CONCLUSIONS AND CLINICAL RELEVANCE-Results provided information on values for PRT, STT, CTT, and IOP in healthy guinea pigs and on expected findings for aerobic bacterial culture and cytologic examination of conjunctival swab specimens.     

Tear film breakup times in young healthy cats before and after anesthesia

The objectives of this study were: (i) to determine tear film breakup times (BUTs) in young healthy cats; (ii) to determine tear film BUTs in feline eyes within 8-20 h following general anesthesia; (iii) to determine if tear film BUTs vary significantly preoperatively when compared with values obtained 8-20 h postoperatively; (iv) to determine if Schirmer tear test (STT) values correlate with tear film BUTs in young healthy cats; and (v) to determine if the isolation of particular etiologic agents from conjunctival swabs of healthy cats affects tear film BUTs. We studied eighteen healthy Domestic Short-haired (n=14) and Domestic Long-haired (n=4) cats, with normal ocular examinations, ranging in age from 0.5 to 3 years. Complete ophthalmic examinations, including tear film BUTs, were performed on all cats. Conjunctival swabs from each eye of all cats and blood samples from all cats were collected and submitted for polymerase chain reaction screening for feline herpes virus, Chlamydophila felis, Mycoplasma spp., and calicivirus. In 10 of 18 cats, STT values and tear film BUTs were measured before general anesthesia was administered and again within 8-20 h following the end of anesthesia. Mean preanesthesia tear film BUTs for all 18 cats were 17.4+/-4.6 s OD and 16.0+/-4.5 s OS. Mean postanesthesia tear film BUT results were 12.5+/-4.3 and 13.1+/-4.0 s OD and OS, respectively. Postanesthesia tear film BUTs were significantly more rapid than those measured before anesthesia (OD only). There was also a positive correlation, both before and after anesthesia, between STT values in both eyes (OU) and tear film BUTs OU. The isolation or lack of isolation of conjunctival microorganisms using PCR did not significantly affect tear film BUTs. Mean tear film BUT in young healthy domestic cats is 16.7+/-4.5 s. Tear BUT is positively correlated with STT values. Although mean tear film BUTs OD at 8-20 h following anesthesia were more rapid than preanesthesia values, this difference did not appear clinically relevant.     

Decreased tear production associated with general anesthesia in the horse

Schirmer I tear tests were conducted on 14 horses. The test was performed before and after IV administration of xylazine hydrochloride, during maintenance anesthesia with halothane in oxygen, and 3 hours after discontinuation of anesthesia. Xylazine hydrochloride did not decrease tear production from the mean base-line value of 23.94 +/- 5.23 mm/min after its IV administration. Tear production was decreased to mean values of 15.57 +/- 4.29 mm/min at 30 minutes and 13.84 +/- 4.25 mm/min at 60 minutes during the maintenance of halothane anesthesia. Three hours after anesthesia was discontinued, tear production returned to a mean value of 22.58 +/- 4.12 mm/min.     

Effect of atropine sulfate on tear production in the cat when used with ketamine hydrochloride and acetylpromazine maleate

Schirmer I tear tests were done on 10 cats before and during anesthesia induced with ketamine hydrochloride in combination with acetylpromazine maleate, with and without atropine sulfate as a preanesthetic agent. Use of atropine sulfate alone decreased tear production from a mean base-line value of 16.9 +/- 3.7 mm/min to 8.2 +/- 4.9 mm/min, 10 minutes after its subcutaneous administration. Tear production continued to decrease from 8.2 +/- 4.9 mm/min to a mean of 2.3 +/- 2.5 mm/min at 30 minutes after the administration of the ketamine hydrochloride and acetylpromazine maleate combination.     

Evaluation of the Schirmer tear test in clinically normal rabbits

Mean (+/- SD) value for results of the Schirmer tear test without use of topical anesthesia on 142 rabbit eyes was 5.30 (+/- 2.96) mm/min; range was 15 mm/min, with low value of 0 and high value of 15 mm/min. Two SD from the mean provided a normal clinical range of 0 to 11.2 mm/min for inclusion of 95% of the population. Significant differences were not evident between eye (right vs left) or gender or among breeds; interaction among eye, gender, and breed also was not observed. Although mean values for 2 breeds were significantly different from values in the other 10 breeds and from each other, they were still within the proposed normal range of 2 SD. The Schirmer tear test without topical anesthesia may be useful in rabbits for evaluation of increased values correlated with ocular irritation, rather than for determination of decreased values associated with keratoconjunctivitis sicca.     

Analysis of tear uptake by the Schirmer tear test strip in the canine eye

OBJECTIVE: To analyze the uptake of tears in a Schirmer tear test (STT) in vitro and in vitro. MATERIALS AND METHODS: Uptake of fluid by Schirmer tear test strips was studied in vitro by examining fluid uptake over time from an unlimited fluid supply as well as with specific fluid volumes applied to the test strip. Uptake of fluid by Schirmer tear test strips was evaluated in a population of 100 ophthalmologically normal dogs together with a group of 40 dogs with tear film abnormalities such as keratoconjunctivitis sicca (KCS) or epiphora. Each animal was given a full ophthalmic examination followed by a standard Schirmer tear test extended over between 3 and 5 min with the STT reading recorded every 5 s and plotted over time. To determine the effect of ocular irritation by the test strip, uptake of tears by test strips was determined before and after topical anesthesia in 20 dogs. RESULTS: In vitro examination of fluid uptake by the STT strips showed an initial rapid uptake followed by a gradual reduction in rate of uptake. Temporal evaluation of STT in vivo showed a similar rapid initial uptake of tear fluid, followed in the majority of cases by a sudden change to a steady state uptake of fluid. The initial gradient was 29.3 +/- 16.9 mm/min followed by a steady state uptake of 5.2 +/- 2.3 mm/min in normal dogs and 1.9 +/- 1.3 mm/min in dogs with KCS. This corresponds to a steady state tear turnover of 7.8 +/- 3.4 microL/min in normal dogs and 2.8 +/- 1.9 microL/min in animals with KCS. Dogs with nasolacrimal blockage and resultant epiphora showed a high initial gradient but final gradients were not statistically different from those of normal dogs. Discussion and conclusions Temporal evaluation of tear uptake by the STT shows substantial differences in rate of tear uptake at different time-points during the period of the test. RESULTS: of this study suggest that the initial rapid rise in STT value represents uptake from the tear lake followed by a slower tear uptake of tears from steady state tear production. Temporal examination of the Schirmer tear test allows a more precise evaluation of tear production than the standard STT measuring tear uptake in 1 min, together with estimation of the contribution to the test strip tear uptake of tears from the residual tear lake volume and those from continual tear production.     

Tear production in normal juvenile dogs

Objective To establish a baseline range or average for tear production in normal juvenile dogs and evaluate the effects of age, weight, and gender on Schirmer tear test (STT) in juvenile dogs. Materials and methods Healthy puppies of various breeds <6 months of age. STT1 and STT2 were performed in both eyes of each subject. Statistical analysis was performed using a backwards stepwise regression model with repeated measures. Using continuous variables of STT1 and STT2 as the dependent variables separately, the independent variables were age (days), eye (left or right), gender (male or female), ocular disease processes in eyes or not, and weight (kg). Results Eighty‐six eyes from 27 males and 16 females were included in this study. Ages ranged from 25 to 133 (mean ± SEM: 61.74 ± 24.15) days and weights ranged from 0.88 to 8.86 (3.27 ± 2.22) kg. STT1 results ranged from 0 to 26 (15.76 ± 5.79) mm/min. STT2 results ranged from 0 to 24 (8.79 ± 5.01) mm/min. Age, weight, and gender significantly affected STT1 results. Weight and gender significantly affected STT2 results. STT1 values increased by 0.15 mm/min for each 1 day increase in age and by 0.84 mm/min for each 1 kg increase in body weight. STT2 values increased by 0.57 mm/min for each 1 kg increase in body weight. Conclusions Age, weight, and gender significantly affect tear production in normal juvenile dogs. STT1 increases to adult values at approximately 9–10 weeks of age.     

Effect of topical 0.02% tacrolimus aqueous suspension on tear production in dogs with keratoconjunctivitis sicca

Objective To investigate the effect of 0.02% tacrolimus in aqueous suspension on tear production in dogs with keratoconjunctivitis sicca (KCS). Animals studied One hundred five dogs diagnosed with KCS [Schirmer tear test (STT) ≤ 10 mm/min and clinical signs of dry eye]. Eyes with marginally decreased STT (11 ≤ 15 mm/min) and clinical signs of dry eye were also evaluated. Procedure The investigation was conducted in two parts: an initial efficacy study and a subsequent double blinded controlled study. In the efficacy study, the effect of topical tacrolimus (formerly FK‐506) on tear production in dogs with primary KCS was evaluated. Dogs were divided into four categories: 1) 59 eyes (38 dogs) naïve to tear stimulation therapy with initial STT ≤ 10 mm/min; 2) 28 eyes (21 dogs) naïve to tear stimulation therapy with initial STT 11 ≤ 15 mm/min; 3) 30 eyes (15 dogs) maintained successfully on CsA therapy; 4) 47 eyes (24 dogs) unresponsive to CsA therapy. STT and clinical signs were evaluated prior to and after 6 to 8 weeks of twice daily tacrolimus administration. Tacrolimus was substituted for CsA therapy in categories 3 and 4. The controlled study compared the effect of topical tacrolimus in aqueous suspension to administration of the aqueous carrier alone on tear production in 20 dogs with primary KCS. Results In the efficacy study, STT increased by 5 mm/min in 84.7%, 25.0%, 26.7% and 51.1% of eyes in categories 1, 2, 3 and 4 respectively after tacrolimus administration. Eighty‐three percent of eyes with extremely low initial STT (≤ 2 mm/min), increased 5 mm/min after tacrolimus. In the controlled study, STT increased by 5 mm/min in 7/10 dogs (14/20 eyes) that received tacrolimus and in none of the 10 dogs that received aqueous carrier alone. Dogs receiving just the aqueous carrier were subsequently treated with tacrolimus, and STT increased 5 mm/min in 9 dogs (18/20 eyes) after administration. Conclusions Twice daily administration of 0.02% tacrolimus in aqueous suspension effectively increased tear production in dogs with KCS. Topical tacrolimus is a promising alternative to topical CsA for treatment of KCS and may be beneficial in patients with less than optimal response to topical CsA.     

Use of punctal occlusion in the treatment of canine keratoconjunctivitis sicca

Twenty eyes of 10 dogs with keratoconjunctivitis sicca (KCS) were treated by occlusion of the ventral nasolacrimal punctum with a silicone punctal plug in order to increase the volume of the remaining tear lake. Punctal size was measured using a commercially available punctal gauge and the appropriate sized plug was inserted under local anaesthesia. Seven dogs showed an increase in Schirmer tear test I (STT) value. STT values immediately prior to plug placement were 2.3 +/- 1.7 mm/minute. STT values with punctal occlusion were 6.1 +/- 4.1 mm/minute, giving a mean increase of 3.8 +/- 2.7 mm/minute (P<0.001). In 14 eyes of eight dogs, the increase in STT values was accompanied by a clinical improvement in the appearance of the ocular surface. In the three dogs with no increase in STT values, the use of punctal plugs reduced the frequency of artificial tear replacement therapy required to maintain a healthy ocular surface. These results show that use of punctal plugs in dogs with KCS may be appropriate where other lacrimomimetic medications have been unsuccessful.     

Determination of reference values for intraocular pressure and Schirmer tear test in clinically normal ostriches (Struthio camelus)

The purpose of this study was to establish normal physiologic reference values for intraocular pressure (IOP) and Schirmer tear test (STT) results in clinically normal ostriches (Struthio camelus). Twenty ostriches of both sexes, 10 juveniles (1.5-2 yr of age) and 10 adults, were included in this study. Complete ophthalmic examination was performed prior to this investigation. STT was performed by inserting a standard sterile STT strip over the ventral lid margin into the ventral conjunctival sac for 60 sec. Following the STT, IOP was measured using applanation tonometry with the Tono-Pen Vet tonometer after topical instillation of one drop of 0.5% proparacaine ophthalmic solution. The mean +/- SD and range of Tono-Pen readings of IOP for all birds was 18.8 +/- 3.5, with a range of 12-24. Mean IOP in juvenile ostriches was 19.7 +/- 3.6. Mean IOP in adult ostriches was 16.9 +/- 2.9. There was no statistically significant difference between young and adult birds (P = 0.07). The mean STT values in the present study were 16.3 +/- 2.5 mm/1 min when measurements from both eyes were averaged. Mean STT in juvenile and adult ostriches was 15.4 +/- 1.8 and 17.2 +/- 2.9 mm/1 min, respectively. There was no statistically significant difference between young and adult birds (P = 0.11). No statistically significant differences between genders were found for any of the results (P > or = 0.41). In conclusion, this study provides normal reference range values for STT and IOP in clinically healthy ostriches.     

Reference values for Schirmer tear tests I and II in clinically normal pigs

Objective To determine reference values for Schirmer tear tests I and II in clinically normal pigs. Animal studied Twenty clinically normal Landrace pigs (10 males and females) without ocular abnormalities were used in this study. Procedures In all pigs, Schirmer tear tests (STT) I and II were performed by using a sterile Schirmer tear test standardized strip (Schirmer‐Tränentest^®, Germany) placed in the lower conjunctival fornix for 1 min. Results For each test (STT I and STT II), no differences were observed between the right and left eyes (P ≥ 0.5). The mean ± SD STT I value was 15.6 ± 3.7 mm/min (range, 10–22 mm/min), while the mean STT II value was 12.4 ± 3.8 mm/minute (range, 5–18 mm/min). The mean STT II value was significantly lower than the STT I level (P < 0.001). Animal gender did not have a significant effect on STT I and II values (P = 0.52). The mean ± SD STT I/II values of 10 juvenile pigs were significantly lower than the mean ± SD STT I/II values of 10 adult pigs (P < 0.001). Conclusions This study of 20 Landrace pigs provided valuable information on normal STT I/II in this species. Knowledge of normal STT reference values in pigs enables the clinician to evaluate corneal pathology and diagnose tear deficiency syndromes with greater accuracy.     

Serum and urine inorganic fluoride concentrations and urine oxalate concentrations following methoxyflurane anesthesia in the dog.

Plasma fluoride, urine fluoride and urine oxalate concentrations were measured before administering an anesthetic to 8 dogs, and at 0, 3, 9, 24, 48, and 72 hours following 1.5 hours of anesthesia with 1% methoxyflurane. Plasma and urine osmolalities were measured and compared with fluoride and oxalate values. Fluoride concentration increased in both plasma and urine following anesthesia when compared with the preanesthetic concentrations. Maximum mean plasma inorganic fluoride was 106.71 mumoles per liter (+/- 25.44 SE) at 9 hours after exposure to methoxyflurane was completed. By 72 hours after exposure to methoxyflurane the plasma fluoride concentration was 23.47 microM/L (+/- 5.74 SE). Mean urine inorganic fluoride concentration was highest at 9 hours after exposure to methoxyflurane and reached 6047.03 microM/L (+/- 1378.46 SE) as compared to the mean preanesthetic base-line concentration of 542.68 microM/L (+/- 132.93 SE), and the 72 hour mean urine fluoride concentration which was 1593.78 microM/L (+/- 579.46 SE). Urine oxalate concentrations, when compared with urine osmolality (mg/mOsm), increased throughout the study. The 72-hour concentration after exposure to methoxyflurane was 2.5 times the preanesthetic (mg/mOsm) oxalate concentration. Plasma osmolality did not change markedly during the study. Urine osmolalities varied between animals and collection times, but a consistent pattern did not occur. Clinical and laboratory signs of renal dysfunction were not observed in any animal during the study.     

Schirmer tear tests and intraocular pressures in conscious and anesthetized koalas (Phascolarctus cinereus)

Objective To estimate mean Schirmer tear test (STT) and intraocular pressure (IOP) values in healthy koalas both conscious and anesthetized. Methods Data were gathered from koalas in Victoria, Australia. Conscious examinations were performed on captive koalas. Free‐ranging (wild) koalas were examined under anesthesia. Anesthesia was induced using alfaxalone, and animals were maintained on oxygen and isoflurane if required. All animals were healthy and had no surface ocular pathology detectable during slit lamp biomicroscopy. STT I tests were performed using commercial STT test strips placed in the lower fornix for 1 min. IOP was measured using an applanation tonometer after topical anesthesia. The higher value of the two eyes for both STT and IOP was analyzed. STT was measured in 53 koalas (34 conscious, 19 anesthetized) and IOP was measured in 43 koalas (30 conscious, 13 anesthetized). A two‐sample t‐test was used to compare means. A P‐value <0.05 was regarded as significant. Mean ± SD is presented. Results The mean higher STT in conscious koalas was 10.3 ± 3.6 mm wetting/min and in anesthetized koalas it decreased to 3.8 ± 4.0 mm wetting/min (P < 0.0001). The mean higher IOP in conscious koalas was 15.3 ± 5.1 mmHg, and in anesthetized koalas it was 13.8 ± 3.4 mmHg (P = 0.32). There was no effect of sex on either STT or IOP. Conclusions The mean and SD of STT and IOP values for koalas both conscious and anesthetized were reported. The mean STT was significantly reduced by alfaxalone anesthesia.     

Effect of removal of lacrimal and third eyelid glands on Schirmer tear test results in cats

Schirmer tear tests I and II values for 10 healthy cats were 16.2 +/- 3.8 mm/min and 13.2 +/- 3.4 mm/min, respectively. Surgical removal of the lacrimal gland or the third eyelid gland from the left eye resulted in decreased Schirmer tear test-I values. Clinical signs of keratoconjunctivitis sicca were not seen until the lacrimal and third eyelid glands were removed, at which time the Schirmer tear test-I value was close to 0 mm/min. Conjunctival glands (accessory lacrimal glands of Krause and Wolfring) appeared to contribute little to tear production in these cats.     

Postanesthetic effects of two durations of isoflurane anesthesia in African pygmy hedgehogs (Atelerix albiventris)

Background: African pygmy hedgehogs (Atelerix albiventris) are popular companion animals that require chemical immobilization to facilitate examination. The objective of this study was to evaluate effects of isoflurane anesthetic duration on recovery time, food intake, and body weight following anesthesia in African pygmy hedgehogs. Methods: Eight healthy, adult hedgehogs (4 male, 4 female) were used in this randomized, blinded, complete cross-over study. Two different isoflurane anesthetic durations of 15 minutes (ISO15) and 45 minutes (ISO45) were evaluated with a 2-week wash-out period between treatments. Physiologic parameters, reflexes, and behaviors were monitored to assess anesthesia quality. Food intake (grams of food per kg of body weight) and body weight were measured both before and after anesthesia to assess postsedation effects. Result: There was no statistically significant difference in body weight between or within treatments following the anesthetic events. A decrease in postanesthetic food intake from baseline values was noted with both treatments (ISO15: −16% [−40% to 167%]); (ISO45: −13% [−38% to 43%]), but these fluctuations were not statistically significant between or within treatments. The total amount of food consumed per hedgehog over the 6 days following anesthesia was 99 ± 23 g/kg (ISO15) and 108 ± 28 g/kg (ISO45, P = 0.15). Conclusions and clinical relevance: Differences in duration of isoflurane anesthesia of either 15 or 45 minutes does not have a clinically relevant effect on recovery time or postanesthetic food intake in hedgehogs.     

Blood pressure response to tourniquet use in anesthetized horses

Blood pressure during anesthesia and surgery was compared for 2 groups of horses. Group A, consisting of 23 horses, had a tourniquet placed on the distal portion of a limb. The other group of 20 horses (group B) had surgery of comparable nature and duration as did group-A horses, but a tourniquet was not used. There was a statistical difference (P less than 0.05) in the peak systolic arterial blood pressure between the groups; group-A horses had a mean (+/- SEM) peak of 151 +/- 6 mm of Hg and group-B horses had a peak of 118 +/- 4 mm of Hg. In addition, group-A horses had immediate decrease in blood pressure, coincident with tourniquet deflation. The blood pressure decrease of 23 +/- 3 mm of Hg represented 16% of immediate predeflation blood pressure. Comparable blood pressure decrease was not observed at the end of surgery in group-B horses. Significant difference was not found when other factors that could affect blood pressure were considered. These factors included preanesthetic medication, anesthetic agents, mode of ventilation, pretourniquet inflation blood pressure, and duration of tourniquet inflation. Significant (P less than 0.05) difference in peak blood pressure was observed when the tourniquet was placed on the dependent, compared with the uppermost, limb, with changes more pronounced when the tourniquet was placed on the dependent limb. Tourniquet placement was associated with hypertension, and tourniquet deflation was associated with blood pressure decrease in these anesthetized horses.     

Schirmer tear test results in normal horses and ponies: effect of age,season, environment,sex, time of day and placement of strips

Tear production was evaluated in 39 horses and 29 ponies using Schirmer tear test strips to determine whether diurnal or weekly fluctuations occur, whether location of strip placement has an effect, if values are the same for both eyes in an animal and whether sex, age, stabling vs. pasture and winter vs. summer had an effect. There was no test in which the raw score was less than 10 mm, although there were many occasions where tear wetting exceeded 35 mm. Analysis of the raw (continuous) scores by linear regression provided no evidence that signalment, housing or season or location of strip placement affected results. The distribution of tear test scores for a 'population' of eyes did not differ when the right eye was compared with the left eye or when the same eye was compared at different times on the same day. Individual test wetting values for opposing eyes measured at the same time, and also wetting values for the same eye measured at different times on the same day sometimes differed substantially. In winter maximum tear wetting exceeded 35 mm more frequently in the STT I than in the STT II even in housed horses and ponies, but there was no consistent significant difference. There appears to be wide variability in the STT I in normal horses and ponies.     

Effect of lacrimal punctal occlusion on tear production and tear fluorescein dilution in normal dogs

OBJECTIVE: To evaluate effects of lacrimal punctal plugs positioned in either the upper, lower, or combination of upper and lower lacrimal canaliculi on plug retention and tolerance; tear production, as measured by the Schirmer tear test; and the dilution of fluorescein within the tear film in normal dogs. MATERIAL AND METHODS: Lacrimal punctal plugs were positioned in the lower, upper, or combination of lower and upper plugs in six laboratory-quality Beagles under topical anesthesia. Retention of plugs was evaluated daily from 8 to 23 days by visual inspection and slit-lamp biomicroscopy. Schirmer tear tests (STT 1 without topical anesthesia) were performed at 48-h intervals. Dilution of fluorescein was determined at 5- and 45-min post-fluorescein instillations once weekly. RESULTS: Lacrimal punctal plugs of 0.4 and 0.6 mm in diameter were retained for 14 (lower plugs: 100%) and 23 days (75%), and for the upper plugs at 8 days less often (75%), and were infrequently locally nonirritating. Combination of lower and upper plugs seemed to adversely affect retention of either plug. When loss of the plugs occurred, a next larger size plug was necessary suggesting some stretching of the lacrimal canaliculi occurred. Pre- and postplug placement STT results indicated no change with lower and combination lacrimal punctal plugs, but decreased levels following upper lacrimal punctal plugs. Tear fluorescein levels at 5 and 45 min in control eye (no punctum plugs) were 3.39% and 0.14%, respectively. With lower, upper, and the combination of lower and upper lacrimal puncta plugs, tear fluorescein levels at 45 min were higher than the controls (lower: 0.76%; upper: 0.45%, and combination 0.56%). CONCLUSION: Lacrimal punctal silicone plugs are retained for 8-23 days in the lower, upper, and combined lower and upper canaliculi at high rates. Effects on STT levels appear limited. Fluorescein within the tear film persists longer with all different positioned lacrimal punctum plugs than in the control eyes.