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Magone MT, Schuck P. Evaluating Moisture Migration in Schirmer Test Strips: Exploring Brand-Specific Variations and Introducing Calibration and Conversion Methods. Cornea 2024; 43:635-640. [PMID: 38015937 PMCID: PMC10980172 DOI: 10.1097/ico.0000000000003430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 10/01/2023] [Accepted: 10/16/2023] [Indexed: 11/30/2023]
Abstract
PURPOSE Schirmer test results are widely used for ocular surface disease assessment, but Schirmer strips are not standardized. We compare the characteristics and tear volume with millimeter moisture migration in different brands of Schirmer strips and introduce methods for volume-based, brand-independent calibration. METHODS Physical parameters of Haag-Streit, EagleVision, TearFlo, Contacare, and MIPL/A6 Schirmer strip brands were compared. Schirmer strip millimeter moisture migration distances were assessed 5 minutes after application of incremental microliter volumes of human tears. Linear regression analysis of data points from each Schirmer strip brand was performed, and the root-mean-square deviation of data points to the best-fit linear regression was calculated. Calibration correction was performed by converting migration distance to the corresponding tear volume. A reference table and calibration method formulas were created. RESULTS Schirmer strips differed in design, shape, and manufacturing precision. Strip width, weight, and length were different between the 5 brands ( P < 0.05). A wide range of Schirmer strip moisture migration values for identical tear volumes was observed among brands. Statistical measurement resulted in a root-mean-square deviation of 2.9 mm for all data points from all brands. Millimeter to volume and weight to volume-based calibration correction methods resulted in a 2.2- and 3.1-fold measurement error reduction, respectively. CONCLUSIONS Our findings highlight the lack of standardization among different brands of Schirmer strips, raising concerns about potential sources of unintentional measurement errors. We propose volume-based Schirmer strip calibration methods and conversion of millimeter to microliter results to achieve brand-independent results and improve Schirmer test accuracy.
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Affiliation(s)
- M. Teresa Magone
- Consult Services Section, National Eye Institute, National Institutes of Health, Bethesda, MD; and
| | - Peter Schuck
- Laboratory of Dynamics of Macromolecular Assembly, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD
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Pe'er O, Ofri R, Sebbag L. Schirmer tear test-1 with open or closed eyelids: An evaluation in brachycephalic and nonbrachycephalic dogs. Vet Ophthalmol 2024. [PMID: 38654458 DOI: 10.1111/vop.13222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 03/08/2024] [Accepted: 04/04/2024] [Indexed: 04/26/2024]
Abstract
PURPOSE Assess aqueous tear production when measured with the dogs' eyelids open or closed. METHODS Thirty healthy dogs (15 Shih Tzus, 15 Labrador retrievers) were recruited. With the order of testing randomized for each dog, two sessions (separated by 30 min) of STT-1 testing were performed with the dogs' eyelids closed or open. Schirmer strip wetness (every 10 s for 60 s) and number of time(s) the strip dislodged during testing were recorded in each eye. Preferred STT-1 method was surveyed via a global Listserv of the veterinary ophthalmology community. RESULTS STT-1 values were significantly higher in closed versus open eyes in Shih Tzus (18.6 ± 2.7 mm/min vs. 16.3 ± 2.5 mm/min; p = .002) and Labrador retrievers (21.6 ± 2.9 mm/min vs. 17.8 ± 3.2 mm/min, p < .001), findings that were also significant at times <60 s for either breed (p ≤ .004). Schirmer strips dislodged from six dogs with open eyelids and no dogs with closed eyelids. Maximal STT-1 difference with closed versus open eyelids was 13 mm/min in Labrador retrievers and 7 mm/min in Shih Tzus. Survey results from 275 veterinarians showed STT-1 performed with "closed eyelids" (38.5%), "open eyelids" (26.9%), or "never paid attention, sometimes closed, sometimes open" (34.6%). CONCLUSIONS Eyelids status (closed or open) during STT-1 testing had a significant impact on aqueous tear secretion in brachycephalic and nonbrachycephalic dogs, highlighting the importance of consistency when repeating STT-1 in a canine patient. STT-1 differences are likely due to sustained reflex tearing throughout the test duration when the dogs' eyelids are closed.
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Affiliation(s)
- Oren Pe'er
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Ron Ofri
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Lionel Sebbag
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
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3
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Ponzini E. Tear biomarkers. Adv Clin Chem 2024; 120:69-115. [PMID: 38762243 DOI: 10.1016/bs.acc.2024.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2024]
Abstract
An extensive exploration of lacrimal fluid molecular biomarkers in understanding and diagnosing a spectrum of ocular and systemic diseases is presented. The chapter provides an overview of lacrimal fluid composition, elucidating the roles of proteins, lipids, metabolites, and nucleic acids within the tear film. Pooled versus single-tear analysis is discussed to underline the benefits and challenges associated with both approaches, offering insights into optimal strategies for tear sample analysis. Subsequently, an in-depth analysis of tear collection methods is presented, with a focus on Schirmer's test strips and microcapillary tubes methods. Alternative tear collection techniques are also explored, shedding light on their applicability and advantages. Variability factors, including age, sex, and diurnal fluctuations, are examined in the context of their impact on tear biomarker analysis. The main body of the chapter is dedicated to discussing specific biomarkers associated with ocular discomfort and a wide array of ocular diseases. From dry eye disease and thyroid-associated ophthalmopathy to keratoconus, age-related macular degeneration, diabetic retinopathy, and glaucoma, the intricate relationship between molecular biomarkers and these conditions is thoroughly dissected. Expanding beyond ocular pathologies, the chapter explores the applicability of tear biomarkers in diagnosing systemic diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, and cancer. This broader perspective underscores the potential of lacrimal fluid analysis in offering non-invasive diagnostic tools for conditions with far-reaching implications.
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Affiliation(s)
- Erika Ponzini
- Department of Materials Science, University of Milano Bicocca, Milan, Italy; COMiB Research Center, University of Milano Bicocca, Milan, Italy.
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Bayram LC, Isler CT, Ekebas G. Determination of reference values for tear production and intraocular pressure in Pygoscelis penguins of the Antarctic Peninsula. BMC Vet Res 2023; 19:235. [PMID: 37946185 PMCID: PMC10636934 DOI: 10.1186/s12917-023-03794-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/28/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND According to the literature review, this is the first study investigating tear production (TP) and intraocular pressure (IOP) in the Pygoscelis penguins living in their natural habitat. The study aimed to establish normal values for standard ocular tests in the genus Pygoscelis, namely, the Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua), and chinstrap (Pygoscelis antarctica) penguins, in four different islands of Antarctica. Sampling was made by specifically using the left eye of the penguins. The Schirmer's tear test type I (STT-I) and the Tonovet® (rebound tonometer) were used to measure the TP and the IOP, respectively. RESULTS The mean TP and IOP values of 129 Adélie, chinstrap, gentoo, and 120 adult Adélie, gentoo penguins were determined as 10.2 ± 4.0 mm/min and 38.9 ± 13.2 mmHg, respectively. No statistical difference was detected between the penguin species for the mean IOP values, while the difference was determined in all the locations. However, statistical differences in the mean TP values were determined between all locations. CONCLUSION The results of this study provide a reference range of Schirmer's tear test (STT) and IOP values in Pygoscelis penguins and show that the IOP is significantly affected by locations. This result can be attributed to the harsh climatic conditions of the Antarctic Peninsula that change very quickly. The described data may help diagnose clinical pathological findings in Pygoscelis penguins. The STT and rebound tonometry appears to be safe and reproducible methods in Pygoscelis penguins, as the results were obtained quickly and were well tolerated by the birds. Based on our results, we propose that similar studies can be initiated in crowded colonies of three penguin species of this genus on the Antarctic Peninsula, the southern Shetland Islands, and other frequently visited islands in Antarctica.
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Affiliation(s)
- Latife Cakir Bayram
- Department of Pathology, Faculty of Veterinary Medicine, Erciyes University, Kayseri, 38280, Turkey.
| | - Cafer Tayer Isler
- Department of Surgery, Faculty of Veterinary Medicine, Hatay Mustafa Kemal University, Hatay, Turkey
| | - Görkem Ekebas
- Department of Pathology, Faculty of Veterinary Medicine, Erciyes University, Kayseri, 38280, Turkey
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de Sampaio MOB, Moore BA, de Seabra NM, Bortolini M, Vieira TC, Martins CB, de Souza ALG, Martins CM, Montiani-Ferreira F. The development of the normal Schirmer tear test results during the dog's first year of life. Vet Ophthalmol 2023; 26:184-190. [PMID: 36943769 DOI: 10.1111/vop.13087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 02/17/2023] [Accepted: 03/02/2023] [Indexed: 03/23/2023]
Abstract
OBJECTIVE To evaluate the relationship between lacrimation and age in a homogeneous group of healthy beagle dogs during the first year of life. MATERIALS AND METHODS Schirmer tear test I (STT I) was performed at an interval of 12-15 days in both eyes of 16 clinically healthy beagle dogs (eight males and eight females) from 94 to 361 days of age. Three different quadratic polynomial regression equations were estimated for the variation in lacrimation: (1) for the entire period (19 observations), (2) for observations 1-4 (days 94-136), and (3) for observations 5-19 (days 150-361). RESULTS By fitting quadratic regression equations to different phases of tear production during the dog's first year of life, it was possible to see that with each day of life, lacrimation increased 0.08 times (8%). From days 94 to 136, however, lacrimal production fell 1.1 times with each day of life. From day 150 to 361, production increased by 0.02 (2%) each day of life. In addition, there was a positive significant and moderate linear correlation between body weight and STT I values (p = .01). CONCLUSION In dogs, during the first year of life, STT I data distribution is parabolic in shape. Age significantly affected tear production. STT I decreased at approximately 108-121 days of age and increased thereafter. Body weight was a significant factor for STT I in young dogs. The establishment of this normal pattern of lacrimation is important for both clinical practitioners and laboratory studies.
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Affiliation(s)
| | - Bret A Moore
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA
| | | | - Mariza Bortolini
- Veterinary Medicine Department, Federal University of Parana, Curitiba, Brazil
| | | | | | | | - Camila Marinelli Martins
- Veterinary Medicine Department, Federal University of Parana, Curitiba, Brazil
- Departamento de Medicina, Universidade Estadual de Ponta Grossa, Ponta Grossa, Brazil
- AAC&T Consultoria em Pesquisa LTDA, Curitiba, Brazil
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Pinard CL. Diagnostic Tests Used During the Ocular Examination. Vet Clin North Am Small Anim Pract 2023; 53:279-298. [PMID: 36813386 DOI: 10.1016/j.cvsm.2022.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
This article provides a review of the required ocular tests during the ophthalmologic examinations of canine and feline patients. Knowledge of medications affecting ocular parameters and awareness of available instrumentation and test materials is essential for accurate diagnoses.
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Affiliation(s)
- Chantale L Pinard
- Department of Clinical Studies, University of Guelph, Ontario Veterinary College, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
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Gijs M, Arumugam S, van de Sande N, Webers CAB, Sethu S, Ghosh A, Shetty R, Vehof J, Nuijts RMMA. Pre-analytical sample handling effects on tear fluid protein levels. Sci Rep 2023; 13:1317. [PMID: 36693949 PMCID: PMC9873914 DOI: 10.1038/s41598-023-28363-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 01/16/2023] [Indexed: 01/25/2023] Open
Abstract
Tear fluid is emerging as a source of non-invasive biomarkers, both for ocular and systemic conditions. Accurate quantification of tear proteins can be improved by standardizing methods to collect and process tear fluid. The aim of this study was to determine sample handling factors that may influence the tear protein biomarker profile. Tear fluid was collected using Schirmer's strips. Tear proteins were extracted by elution through centrifugation. Total protein content was determined using the bicinchoninic acid assay. Key concepts that apply to the entire sample processing cycle are tear sampling, tear storage, protein extraction and data normalization. Differences in wetting or migration length were observed between Schirmer's strips from different manufacturers, and between protein-free and protein-rich solutions. One unit of migration length (mm) did not correspond to one unit of volume (µL). A positive correlation (r = 0.6671, p < 0.0001) was observed between migration length and total tear protein content. The most beneficial storage conditions were strips that were not stored (+ 21.8%), or underwent 'wet' storage (+ 11.1%). Protein recovery was the highest in 400 µL extraction buffer and independent of protein molecular weight. This study helps to explain inter- and intra-variability that is often seen with tear biomarker research. This information is critical to ensure accuracy of test results, as tear biomarkers will be used for patient management and in clinical trials in the near future. This study also highlights the need for standardization of Schirmer's strip manufacturing, tear fluid processing and analyte concentration normalization.
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Affiliation(s)
- Marlies Gijs
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands.
| | - Sinthuja Arumugam
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands
| | - Nienke van de Sande
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands
| | - Carroll A B Webers
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands
| | - Swaminathan Sethu
- GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India
| | - Arkasubhra Ghosh
- GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India
| | - Rohit Shetty
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands.,GROW Research Laboratory, Narayana Nethralaya Foundation, Bangalore, India.,Department of Cornea and Refractive Surgery, Narayana Nethralaya, Bangalore, India
| | - Jelle Vehof
- Department of Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.,Dutch Dry Eye Clinic, Velp, The Netherlands.,Department of Ophthalmology, Vestfold Hospital Trust, Tønsberg, Norway
| | - Rudy M M A Nuijts
- University Eye Clinic Maastricht, School for Mental Health and Neuroscience (MHeNs), Maastricht University Medical Center (MUMC+), P. Debyelaan 25, 6229 HX, Maastricht, The Netherlands.,Department of Ophthalmology, Zuyderland Medical Center, Heerlen, The Netherlands
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8
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Iwashita H, Sebbag L, Leonard BC, Saito A. A review of diagnostic tests for qualitative and quantitative tear film deficiency in dogs. Vet Ophthalmol 2022; 26 Suppl 1:5-15. [PMID: 36575128 DOI: 10.1111/vop.13044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 11/22/2022] [Indexed: 12/29/2022]
Abstract
Dry eye disease (DED) is a complex multifactorial condition caused by loss of ocular surface homeostasis from quantitative and/or qualitative tear film deficiency. Schirmer tear test (STT) is often the only diagnostic test used to assess for DED in veterinary practice. STT is invaluable in the diagnosis and monitoring of quantitative tear film deficiency (i.e., keratoconjunctivitis sicca); however, it is not sufficient to optimize therapy and fully recognize other contributing factors for the disturbance in ocular surface homeostasis. The present work reviews diagnostic tests for assessing aqueous tear production in veterinary medicine, as well as the quality of tears, corneal epithelial barrier integrity, and the lacrimal functional unit.
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Affiliation(s)
| | - Lionel Sebbag
- Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Brian C Leonard
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, California, USA
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9
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Bertram M, Allbaugh RA, Mochel JP, Peraza J, Page L, Sebbag L. Influence of Schirmer strip wetness on volume absorbed, volume recovered, and total protein content in canine tears. Vet Ophthalmol 2021; 24:425-428. [PMID: 33720492 DOI: 10.1111/vop.12876] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 01/31/2021] [Accepted: 02/12/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Determine the protein content and volume of tears sampled by Schirmer strips wetness ranging from 20 to 35 mm. ANIMALS STUDIED Ten healthy beagle dogs. PROCEDURES Each dog underwent 20 tear collections per day (10 sessions in each eye, spaced by ≥1 h) for 4 separate days, providing 200 tear samples for each length of wetness evaluated: 20, 25, 30, and 35 mm. A Schirmer strip was placed in each eye until the selected mm-mark was reached, calculating the volume absorbed (VA) as the difference between the post- and pre-collection weight (assuming 1 mg~1 µL for tear fluid), and the volume recovered (VR) as the amount pipetted from the tube following centrifugation. Total protein content (TPC) was measured with infrared spectroscopy. Outcome measures were compared with the Kruskal-Wallis test. RESULTS Median values for VA (µL), VR (µL) and TPC (mg/mL) were as follows: 20 mm (18, 10, 5.94), 25 mm (22, 12.5, 5.97), 30 mm (25.5, 16, 5.89), and 35 mm (31, 22.5, 7.13). Both VA and VR were significantly greater (p < .001) for Schirmer strips wetness of 35»30»25»20 mm. TPC was significantly greater (p < .001) for 35 > 20-30 mm, but not among other groups (p = 1.000). CONCLUSIONS The study established normative data to consider when canine studies use Schirmer strips to collect tears for bioanalytical purposes (eg, proteomics, pharmacokinetics). Although 35 mm yielded higher VA and VR, the higher TPC could be explained by greater disruption of ocular surface homeostasis. Absorption to 20-30 mm is the suggested length of strip wetness for bioanalytical tear collection in dogs.
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Affiliation(s)
- Morgan Bertram
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Rachel A Allbaugh
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Jonathan P Mochel
- SMART Pharmacology, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Jacqueline Peraza
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Lauren Page
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
| | - Lionel Sebbag
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.,SMART Pharmacology, Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, IA, USA
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