Tears in horses refer to the production and secretion of lacrimal fluid, which serves to lubricate the eye, remove debris, and provide nutrients to ocular tissues. The composition of equine tears includes water, electrolytes, proteins, and lipids, contributing to the maintenance of corneal health and vision. Tear production can be influenced by various factors, including environmental conditions, ocular health, and systemic diseases. Abnormal tear production or composition may indicate underlying health issues or ocular conditions such as keratoconjunctivitis sicca (dry eye) or excessive tearing (epiphora). This page compiles peer-reviewed research studies and scholarly articles that explore the physiology, diagnostic significance, and clinical implications of tear production in equine health.
Ruptures of the urinary bladder and urachus are the most frequent cause of uroperitoneum in foals. Surgical correction is often the first treatment choice, however, nonsurgical methods, such as urine removal via urinary catheters and abdominal drains, have been successfully performed in foals. Unassigned: Two foals were referred to the Equine Perinatology Unit for suspicion of uroperitoneum. The diagnosis was confirmed by hematobiochemical and ultrasound examinations, thus cystorrhaphy and cystoplasty were attempted. Surgeons found a lesion in the dorsocranial margin of the bladder (Case 1) an...
Kamm JL.To describe the repair utilizing integral-anchor barbed suture in equine rectal tears. Methods: 3 horses aged 3 to 10 years old with grade 3 to 4 rectal tears. Methods: Grade 3 and 4 rectal tears were referred for surgical repair immediately after iatrogenic tearing or tearing during parturition. Integral-anchor barbed suture (Stratafix Symmetric PDS Plus, size 1, 18" CT-1) was placed using long-handled instruments or hand closure depending on the accessibility and visibility of the tear. Closure of grade 3 tears was performed using a continuous appositional pattern. A horizontal mattress patt...
Caspers MK, Gier CJ, Reesink HL.Non-septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse. Objective: To review the published literature to determine which tendon sheaths are commonly affected by non-septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non-septic tenosynovitis. Methods: Systematic review. Methods: Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. Th...
Nardi S, Nuti M, Nocera I, Sgorbini M, Marmorini P, Barsotti G.This study assesses lacrimal secretion in healthy foals within 48 hours after birth and evaluates their variations in lacrimal secretion and menace response appearance during the first month of life. A total of 31 Standardbred foals were evaluated. Foals were housed with their dams in 4 × 4 m boxes throughout the study. A complete ophthalmic examination was performed for each animal enrolled in the study, including the foals' dams which were used as a control group to compare the lacrimal secretion of foals at birth with that of adult horses. In foals, the Schirmer Tear Test I (STT I) and m...
Hussein KH, Elmeligy E, Khalphallah A, Al-Lethie AA.This study was performed to investigate the effects of cyclopentolate on ultrasonographic parameters of eye structures, intraocular pressure (IOP), tear production, and pupil size in normal donkeys. Sixteen eyes of eight clinically healthy adult donkeys (2-2.5 years old) weighing 295 ± 34 kg (mean ± standard deviation) were used in this study. Cyclopentolate hydrochloride 1% was instilled in a randomly selected eye and the other eye received normal saline drops as a control. The effect of cyclopentolate was evaluated by ultrasonography. Additionally, changes in IOP and tear production were ...
Ansari Mood M, Rajaei SM, Faghihi H, Ghiadi A.This study was performed to evaluate the effect of topical 1% cyclopentolate hydrochloride on tear production (STT), intraocular pressure (IOP), and vertical pupil diameter (VPD) in healthy Turkman horses. Forty eyes of 20 clinically normal horses were used for this study, which were randomly assigned to two groups. Before instillation of 1% cyclopentolate, the baseline STT, IOP, and VPD of each group were recorded. Then, one drop of cyclopentolate was instilled randomly into one eye of each animal, and the contralateral eye served as control. Measurements were repeated at 20 minutes, 60 min...
Monk CS, Jeong SY, Gibson DJ, Plummer CE.Tetracyclines have activity against matrix metalloproteinases (MMP). Oral medications with effects on the ocular surface are of interest in patients where repeated topical dosing is limited. The aim of this study was to characterize the concentration of minocycline in the tears of normal horses after oral administration and to determine if this level directly inhibits MMP activity. Methods: Five healthy adult ponies were administered oral minocycline (Wedgewood Pharmacy; Swedesboro, NJ) at 4 mg/kg every 12 h for 5 days. Tears were collected at T = 2, 26, 50, 56, 74, 80, and 98 h. Tear minocycl...
Hart KA, Kitchings KM, Kimura S, Norton NA, Myrna KE.OBJECTIVE To compare tear cortisol concentrations between horses and ponies with pituitary pars intermedia dysfunction (PPID) and healthy nonaged (≤ 15 years old) and aged (≥ 20 years old) horses and to determine whether serum and tear cortisol concentrations were correlated. ANIMALS 11 horses and ponies with PPID and 20 healthy control horses and ponies (11 nonaged and 9 aged). PROCEDURES Paired tear and serum samples were obtained from PPID and control animals. All animals were free of active ocular disease. Tear and serum cortisol concentrations were measured with an ELISA and chemilumi...
Beckwith-Cohen B, Elad D, Bdolah-Abram T, Ofri R.To determine baseline tear pH in dogs, horses, and cattle by use of a microelectrode. Methods: 28 dogs, 24 horses, and 29 cattle. Methods: Under manual restraint, tears were collected from each subject's left eye with cotton spears. A Schirmer tear test was performed in the right eye. Tears were extracted from the spears by centrifugation. Tear volume was measured, pH was determined with a microelectrode, and total solids (TS) concentration was measured by refractometry. Results: Mean ± SD pH of tears in cattle, dogs, and horses was 8.32 ± 0.14, 8.05 ± 0.26, and 7.84 ± 0.30, respectively. ...
Wieser B, Tichy A, Nell B.Guinea pigs have a very low threshold of corneal sensitivity and at the same time nearly no reflex tearing compared to dogs, cats, and horses. The question arose whether there is a general correlation between corneal sensitivity and the quantity of reflex tearing. Methods: Totally 160 animals of 8 different species (20 animals per species) were investigated. Methods: The corneal touch threshold (CTT) was measured with a Cochet-Bonnet esthesiometer. The palpebral fissure length (PFL) was measured with a calliper ruler. The Schirmer tear test (STT) was modified by adapting the width of the STT s...
Czerwinski SL, Lyon AW, Skorobohach B, Léguillette R.Ophthalmic antibiotic therapy in large animals is often used empirically because of the lack of pharmacokinetics studies. The purpose of the study was to determine the pharmacokinetics of topical tobramycin 0.3% ophthalmic solution in the tears of normal horses using an automated immunoassay analysis. Results: The mean tobramycin concentrations in the tears at 5, 10, 15, 30 minutes and 1, 2, 4, 6 hours after administration were 759 (±414), 489 (±237), 346 (±227), 147 (±264), 27.6 (±28.4), 14.8 (±66.6), 6.7 (±18.6), and 23.4 (±73.4) mg/L. Mean tobramycin concentration was maintained abo...
Westermeyer HD, Hendrix DV, Ward DA, Cox SK.To determine ocular tissue drug concentrations after topical ocular administration of 0.3% ciprofloxacin and 0.5% moxifloxacin in ophthalmologically normal horses. Methods: 24 ophthalmologically normal adult horses. Methods: 0.3% ciprofloxacin and 0.5% moxifloxacin solutions (0.1 mL) were applied to the ventral conjunctival fornix of 1 eye in each horse as follows: group 1 (n = 8) at 0, 2, 4, and 6 hours; group 2 (8) at 0, 2, 4, 6, and 10 hours; and group 3 (8) at 0, 2, 4, 6, 10, and 14 hours. Tears, cornea, and aqueous humor (AH) were collected at 8, 14, and 18 hours for groups 1, 2, and 3, r...
Selk Ghaffari M, Sabzevari A, Radmehr B.To observe the effect of topical 1% tropicamide on equine tear production as measured by Schirmer I tear test. Methods: Fourteen adult horses received one drop of 1% tropicamide ophthalmic solution in one eye and the opposite eye served as the control. The tear production in both eyes was tested at 1, 2, 4, 6, and 24 h after 1% tropicamide administration. Results: Measurements made 1 h after treatment revealed a significant reduction in Schirmer tear test values in tropicamide treated eyes (P = 0.002). The observed decrease in tear production was maintained up to 4 h after treatment (P = 0.002...
Piccione G, Giannetto C, Fazio F, Giudice E.This study was designed to assess the daily rhythm of tear production in clinically healthy horses, to compare left eye and right eye, and to evaluate the influence of time and gender. Methods: For our study 18 horses (nine female and nine male) were subjected to three different light/dark (L/D) schedules: 12/12 L/D cycles, constant light (24/0 L/D) and constant darkness (0/24 L/D). Methods: In all subjects Schirmer tear tests were performed at 4-h intervals over a 24-h period. Results: A circadian rhythm of tear production was found during the 12/12 L/D period and during constant darkness. Al...
Zapata GL, Britos RM, Pintos ME, Dreizzen E, Lausada NB, Arauz S.The objective of this paper was to determine the physiological values of urea nitrogen and creatinine in tears, and to compare the results with those obtained from serum. Thirty healthy thoroughbred horses were included in the study. Tear fluid samples were obtained using a glass capillary tube placed in lower conjunctival cul-de-sac. Blood samples were taken from the jugular vein. Tear and serum urea nitrogen and creatinine levels were quantitatively analyzed by an enzymatic colorimetric method. Urea nitrogen values were 4.22+/-1.84 mmol/l in tears and 4.44+/-1.78 mmol/l in serum, whereas cre...
Rothschild CM, Sellon DC, Bryan GM, Gay JM, Hines MT.The objectives of this study were to observe the effects of trimethoprim-sulfadiazine on equine tear production and to determine normal fluctuations in Schirmer tear test (STT) values in horses. A randomized, placebo-controlled, blinded clinical trial measuring STT values in 15 horses over an 8-week period was performed. The treatment group (eight horses) received 30 mg/kg trimethoprim-sulfadiazine orally once a day and the control group (seven horses) received placebo (flour) at the same time. All horses were housed outdoors throughout the study. Schirmer tear test values were measured at 0, ...
Brightman AH, Manning JP, Benson GJ, Musselman EE.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, ...
Wieser B, Tichy A, Nell B.Guinea pigs have a very low threshold of corneal sensitivity and at the same time nearly no reflex tearing compared to dogs, cats, and horses. The question arose whether there is a general correlation between corneal sensitivity and the quantity of reflex tearing. Methods: Totally 160 animals of 8 different species (20 animals per species) were investigated. Methods: The corneal touch threshold (CTT) was measured with a Cochet-Bonnet esthesiometer. The palpebral fissure length (PFL) was measured with a calliper ruler. The Schirmer tear test (STT) was modified by adapting the width of the STT s...
Piccione G, Giannetto C, Fazio F, Giudice E.This study was designed to assess the daily rhythm of tear production in clinically healthy horses, to compare left eye and right eye, and to evaluate the influence of time and gender. Methods: For our study 18 horses (nine female and nine male) were subjected to three different light/dark (L/D) schedules: 12/12 L/D cycles, constant light (24/0 L/D) and constant darkness (0/24 L/D). Methods: In all subjects Schirmer tear tests were performed at 4-h intervals over a 24-h period. Results: A circadian rhythm of tear production was found during the 12/12 L/D period and during constant darkness. Al...
Brightman AH, Manning JP, Benson GJ, Musselman EE.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, ...
Beckwith-Cohen B, Elad D, Bdolah-Abram T, Ofri R.To determine baseline tear pH in dogs, horses, and cattle by use of a microelectrode. Methods: 28 dogs, 24 horses, and 29 cattle. Methods: Under manual restraint, tears were collected from each subject's left eye with cotton spears. A Schirmer tear test was performed in the right eye. Tears were extracted from the spears by centrifugation. Tear volume was measured, pH was determined with a microelectrode, and total solids (TS) concentration was measured by refractometry. Results: Mean ± SD pH of tears in cattle, dogs, and horses was 8.32 ± 0.14, 8.05 ± 0.26, and 7.84 ± 0.30, respectively. ...
Hart KA, Kitchings KM, Kimura S, Norton NA, Myrna KE.OBJECTIVE To compare tear cortisol concentrations between horses and ponies with pituitary pars intermedia dysfunction (PPID) and healthy nonaged (≤ 15 years old) and aged (≥ 20 years old) horses and to determine whether serum and tear cortisol concentrations were correlated. ANIMALS 11 horses and ponies with PPID and 20 healthy control horses and ponies (11 nonaged and 9 aged). PROCEDURES Paired tear and serum samples were obtained from PPID and control animals. All animals were free of active ocular disease. Tear and serum cortisol concentrations were measured with an ELISA and chemilumi...
Monk CS, Jeong SY, Gibson DJ, Plummer CE.Tetracyclines have activity against matrix metalloproteinases (MMP). Oral medications with effects on the ocular surface are of interest in patients where repeated topical dosing is limited. The aim of this study was to characterize the concentration of minocycline in the tears of normal horses after oral administration and to determine if this level directly inhibits MMP activity. Methods: Five healthy adult ponies were administered oral minocycline (Wedgewood Pharmacy; Swedesboro, NJ) at 4 mg/kg every 12 h for 5 days. Tears were collected at T = 2, 26, 50, 56, 74, 80, and 98 h. Tear minocycl...
Westermeyer HD, Hendrix DV, Ward DA, Cox SK.To determine ocular tissue drug concentrations after topical ocular administration of 0.3% ciprofloxacin and 0.5% moxifloxacin in ophthalmologically normal horses. Methods: 24 ophthalmologically normal adult horses. Methods: 0.3% ciprofloxacin and 0.5% moxifloxacin solutions (0.1 mL) were applied to the ventral conjunctival fornix of 1 eye in each horse as follows: group 1 (n = 8) at 0, 2, 4, and 6 hours; group 2 (8) at 0, 2, 4, 6, and 10 hours; and group 3 (8) at 0, 2, 4, 6, 10, and 14 hours. Tears, cornea, and aqueous humor (AH) were collected at 8, 14, and 18 hours for groups 1, 2, and 3, r...
Rothschild CM, Sellon DC, Bryan GM, Gay JM, Hines MT.The objectives of this study were to observe the effects of trimethoprim-sulfadiazine on equine tear production and to determine normal fluctuations in Schirmer tear test (STT) values in horses. A randomized, placebo-controlled, blinded clinical trial measuring STT values in 15 horses over an 8-week period was performed. The treatment group (eight horses) received 30 mg/kg trimethoprim-sulfadiazine orally once a day and the control group (seven horses) received placebo (flour) at the same time. All horses were housed outdoors throughout the study. Schirmer tear test values were measured at 0, ...
Selk Ghaffari M, Sabzevari A, Radmehr B.To observe the effect of topical 1% tropicamide on equine tear production as measured by Schirmer I tear test. Methods: Fourteen adult horses received one drop of 1% tropicamide ophthalmic solution in one eye and the opposite eye served as the control. The tear production in both eyes was tested at 1, 2, 4, 6, and 24 h after 1% tropicamide administration. Results: Measurements made 1 h after treatment revealed a significant reduction in Schirmer tear test values in tropicamide treated eyes (P = 0.002). The observed decrease in tear production was maintained up to 4 h after treatment (P = 0.002...
Czerwinski SL, Lyon AW, Skorobohach B, Léguillette R.Ophthalmic antibiotic therapy in large animals is often used empirically because of the lack of pharmacokinetics studies. The purpose of the study was to determine the pharmacokinetics of topical tobramycin 0.3% ophthalmic solution in the tears of normal horses using an automated immunoassay analysis. Results: The mean tobramycin concentrations in the tears at 5, 10, 15, 30 minutes and 1, 2, 4, 6 hours after administration were 759 (±414), 489 (±237), 346 (±227), 147 (±264), 27.6 (±28.4), 14.8 (±66.6), 6.7 (±18.6), and 23.4 (±73.4) mg/L. Mean tobramycin concentration was maintained abo...
Ansari Mood M, Rajaei SM, Faghihi H, Ghiadi A.This study was performed to evaluate the effect of topical 1% cyclopentolate hydrochloride on tear production (STT), intraocular pressure (IOP), and vertical pupil diameter (VPD) in healthy Turkman horses. Forty eyes of 20 clinically normal horses were used for this study, which were randomly assigned to two groups. Before instillation of 1% cyclopentolate, the baseline STT, IOP, and VPD of each group were recorded. Then, one drop of cyclopentolate was instilled randomly into one eye of each animal, and the contralateral eye served as control. Measurements were repeated at 20 minutes, 60 min...
Hussein KH, Elmeligy E, Khalphallah A, Al-Lethie AA.This study was performed to investigate the effects of cyclopentolate on ultrasonographic parameters of eye structures, intraocular pressure (IOP), tear production, and pupil size in normal donkeys. Sixteen eyes of eight clinically healthy adult donkeys (2-2.5 years old) weighing 295 ± 34 kg (mean ± standard deviation) were used in this study. Cyclopentolate hydrochloride 1% was instilled in a randomly selected eye and the other eye received normal saline drops as a control. The effect of cyclopentolate was evaluated by ultrasonography. Additionally, changes in IOP and tear production were ...
Zapata GL, Britos RM, Pintos ME, Dreizzen E, Lausada NB, Arauz S.The objective of this paper was to determine the physiological values of urea nitrogen and creatinine in tears, and to compare the results with those obtained from serum. Thirty healthy thoroughbred horses were included in the study. Tear fluid samples were obtained using a glass capillary tube placed in lower conjunctival cul-de-sac. Blood samples were taken from the jugular vein. Tear and serum urea nitrogen and creatinine levels were quantitatively analyzed by an enzymatic colorimetric method. Urea nitrogen values were 4.22+/-1.84 mmol/l in tears and 4.44+/-1.78 mmol/l in serum, whereas cre...
Nardi S, Nuti M, Nocera I, Sgorbini M, Marmorini P, Barsotti G.This study assesses lacrimal secretion in healthy foals within 48 hours after birth and evaluates their variations in lacrimal secretion and menace response appearance during the first month of life. A total of 31 Standardbred foals were evaluated. Foals were housed with their dams in 4 × 4 m boxes throughout the study. A complete ophthalmic examination was performed for each animal enrolled in the study, including the foals' dams which were used as a control group to compare the lacrimal secretion of foals at birth with that of adult horses. In foals, the Schirmer Tear Test I (STT I) and m...
Kamm JL.To describe the repair utilizing integral-anchor barbed suture in equine rectal tears. Methods: 3 horses aged 3 to 10 years old with grade 3 to 4 rectal tears. Methods: Grade 3 and 4 rectal tears were referred for surgical repair immediately after iatrogenic tearing or tearing during parturition. Integral-anchor barbed suture (Stratafix Symmetric PDS Plus, size 1, 18" CT-1) was placed using long-handled instruments or hand closure depending on the accessibility and visibility of the tear. Closure of grade 3 tears was performed using a continuous appositional pattern. A horizontal mattress patt...
Caspers MK, Gier CJ, Reesink HL.Non-septic tenosynovitis is a clinically relevant and often performance limiting musculoskeletal injury in the horse. Objective: To review the published literature to determine which tendon sheaths are commonly affected by non-septic tenosynovitis and to describe the most frequently reported pathological lesions, outcomes, and surgical complications in equine non-septic tenosynovitis. Methods: Systematic review. Methods: Literature searches were conducted in July 2021 from the online search engines PubMed, Scopus, Web of Science Core, VetMed Resource and ProQuest Theses & Dissertations. Th...
Ruptures of the urinary bladder and urachus are the most frequent cause of uroperitoneum in foals. Surgical correction is often the first treatment choice, however, nonsurgical methods, such as urine removal via urinary catheters and abdominal drains, have been successfully performed in foals. Unassigned: Two foals were referred to the Equine Perinatology Unit for suspicion of uroperitoneum. The diagnosis was confirmed by hematobiochemical and ultrasound examinations, thus cystorrhaphy and cystoplasty were attempted. Surgeons found a lesion in the dorsocranial margin of the bladder (Case 1) an...
