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

Abstract

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.

Reference values, intertest correlations, and test-retest repeatability of selected tear film tests in healthy cats

“…54 In addition, the test strips used in our study e improve measurement reliability and enhance measurement precision, compared with a conventional fluorescein strip, 55 thus eliminating the need to average the results of multiple, consecutive TFBUT measurements. 16,18,38 Differences in study methodology notwithstanding, most healthy cats have been reported to have TFBUTs > 10 seconds, 16,18,19,38 which is comparable to findings from the present study, in which only 2.5% of this healthy population had TFBUTs < 9.1 seconds. On the basis of data from the present and previous studies, tear film instability should be suspected in cats with TFBUTs < 9 or 10 seconds.…”

“…6 Rapid TFBUT suggests an unstable tear film and has been reported for cats with conjunctivitis, [18][19][20] chronic nonhealing ulcers, 15 and corneal sequestra 15,16 as well as those previously infected with FHV-1. 19 In the present study, TFBUT (median, 12.4 seconds; 95% CR, 9.1 to 17.7 seconds) was shorter than TFBUTs reported in other studies 16,18,19,38 (mean, 13.5 to 21 seconds). This may be attributable to differences in the number of eyes tested, age range of cats tested, interexaminer variation (especially given the subjectivity of this assay), number of measurements made each time, the source and volume of fluorescein used, and method of application.…”

“…20,[36][37][38][39][40] Unlike dogs, in which tear production decreases with increasing age 41 but is unchanged by sex, 41,42 we found no effect of age or sex on this measure in the feline population tested. Despite the relative consistency of results among studies reporting mean STT-1 values of cats, it is unclear what the lower limit for STT-1 values should be in healthy cats.…”

Evaluation of tear production with modified Schirmer tear test-1 during the neonatal period in cats

“…However, values of the modified Schirmer tear test-1 (mSTT-1) observed in our study are very below reference values described for the standard Schirmer tear test (SST) in healthy young and adult cats (Cullen et al 2005a, Lim & Cullen 2005, Lim et al 2009). …”

“…In accordance to Williams (2005), in one minute, the wetting of the strip is related only to residual pre-existing tears in the conjunctival fornix, being necessary four additional minutes to accurately evaluate tear reflex production. However, the one minute SST-1 remains the standard test to assess tear production in veterinary ophthalmology (Silva & Galera 2004, Cullen et al 2005a, Hartley et al 2006, Grahn et al 2005, Lim & Cullen 2005.…”