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Ocular parameters related to drug delivery in the canine and equine eye: aqueous and vitreous humor volume and scleral surface area and thickness.
Abstract: To measure the ocular surface area, scleral thickness, and the aqueous and vitreous humor volumes in the canine and equine eye. Animals studied Fourteen canine and 16 equine cadaver eyes. Methods: Eyes were measured either fresh or following fixation in formalin. Ocular surface area was calculated using the fluid displacement method. Globes were hemisected and aqueous and vitreous humor were collected and quantitated. Scleral thickness was measured by digital caliper, by image projection, and by ultrasonic biomicroscopy (UBM). Results: Mean +/- standard deviation (SD) scleral surface areas in canine and equine eyes were 12.87 +/- 2.24 and 57.23 +/- 5.63 cm2, respectively. Mean +/- SD aqueous humor volume was 0.77 +/- 0.24 in the dog and 3.04 +/- 1.27 mL in the horse. Mean vitreous humor volume was 1.7 +/- 0.86 mL for the canine eye and 26.15 +/- 4.87 mL for the equine eye. In canine and equine eyes, the sclera was thinnest at the ocular equator: 0.34 +/- 0.13 mm (canine) and 0.53 +/- 0.1 (equine). There were no significant differences between the direct caliper and projected thickness measurements or differences between measurements in the superior, inferior, nasal, and temporal quadrants of the eye. Scleral thickness in fresh tissue was greater than in fixed tissue at most sites. Conclusions: The UBM measurement method appeared to be most consistent and reproducible when compared to direct measurement techniques. Formalin fixation of the eyes was associated with significantly thinner scleral tissue than with fresh ocular tissue.
Publication Date: 2005-07-13 PubMed ID: 16008707DOI: 10.1111/j.1463-5224.2005.00401.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research aimed to measure the ocular surface area, the thickness of the sclera, and the volumes of the aqueous and vitreous humor in cadaver eyes from dogs and horses, and it discovered that certain measurement methods were more consistent and that formalin fixation resulted in thinner scleral tissue.
Methods
- The study involved 14 canine eyes and 16 equine eyes, all of which were sourced from cadavers.
- These eyes were either measured fresh or after being fixed in formalin, a solution used to preserve biological specimens.
- The researchers used the fluid displacement method to calculate the ocular surface area.
- To collect and quantify the aqueous and vitreous humor, the globes of the eyes were divided into two hemispheres.
- Scleral thickness was determined through three methods: direct measurements with a digital caliper, image projection, and ultrasonic biomicroscopy (UBM).
Results
- The average scleral surface areas in canine and equine eyes were approximately 12.87 cm2 and 57.23 cm2, respectively.
- Canine aqueous humor volume averaged at 0.77 mL, while for equine eyes, it was around 3.04 mL.
- Vitreous humor volume averaged at 1.7 mL for canine eyes and 26.15 mL for equine eyes.
- The thinnest section of the sclera, for both canine and equine eyes, was located at the ocular equator, with thicknesses being about 0.34 mm for canines and 0.53 mm for equines.
- There were negligible differences between the direct caliper and projected thickness measurements, and also no marked difference between measurements in the superior, inferior, nasal, and temporal quadrants of the eye.
- Scleral thickness when measured in fresh tissue was higher than in formalin-fixed tissue at most sites.
Conclusions
- Of the scleral thickness measurement methods, the researchers found UBM to be the most consistent and reproducible.
- The study’s authors observed that formalin fixation resulted in a significant reduction in scleral thickness when compared to fresh ocular tissue.
Cite This Article
APA
Gilger BC, Reeves KA, Salmon JH.
(2005).
Ocular parameters related to drug delivery in the canine and equine eye: aqueous and vitreous humor volume and scleral surface area and thickness.
Vet Ophthalmol, 8(4), 265-269.
https://doi.org/10.1111/j.1463-5224.2005.00401.x Publication
Researcher Affiliations
- College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA. brian_gilger@ncsu.edu
MeSH Terms
- Animals
- Aqueous Humor
- Dogs / anatomy & histology
- Drug Delivery Systems / veterinary
- Horses / anatomy & histology
- Ophthalmic Solutions / administration & dosage
- Reference Values
- Sclera / anatomy & histology
- Vitreous Body / anatomy & histology
Citations
This article has been cited 9 times.- Terhaar HM, Henriksen ML, Uhl LK, Boeckling C, Mehaffy C, Hess A, Lappin MR. Pro-inflammatory cytokines in aqueous humor from dogs with anterior uveitis and post-operative ocular hypertension following phacoemulsification, primary glaucoma, and normal healthy eyes. PLoS One 2022;17(8):e0273449.
- Knickelbein KE, Lassaline ME, Kim S, Scharbrough MS, Thomasy SM. Corneal thickness and anterior chamber depth of the normal adult horse as measured by ultrasound biomicroscopy. Vet Ophthalmol 2022 May;25 Suppl 1(Suppl 1):17-24.
- Wang L, Zhou MB, Zhang H. The Emerging Role of Topical Ocular Drugs to Target the Posterior Eye. Ophthalmol Ther 2021 Sep;10(3):465-494.
- Mora-Pereira M, Abarca EM, Duran S, Ravis W, McMullen RJ Jr, Fischer BM, Lee YP, Wooldridge AA. Sustained-release voriconazole-thermogel for subconjunctival injection in horses: ocular toxicity and in-vivo studies. BMC Vet Res 2020 Apr 16;16(1):115.
- Thomasy SM, Eaton JS, Timberlake MJ, Miller PE, Matsumoto S, Murphy CJ. Species Differences in the Geometry of the Anterior Segment Differentially Affect Anterior Chamber Cell Scoring Systems in Laboratory Animals. J Ocul Pharmacol Ther 2016 Jan-Feb;32(1):28-37.
- Beltran WA. The use of canine models of inherited retinal degeneration to test novel therapeutic approaches. Vet Ophthalmol 2009 May-Jun;12(3):192-204.
- Tucker-Retter EK, Yamagata M, Gilger B, Oh A. Retrospective Assessment of Carbonic Anhydrase Inhibitors in Topical or Episcleral Implant Form for the Treatment of Equine Glaucoma. Vet Ophthalmol 2025 Nov;28(6):977-982.
- Higa K, Kimoto R, Kojima T, Dogru M, Müller-Lierheim WGK, Shimazaki J. Therapeutic Aqueous Humor Concentrations of Latanoprost Attained in Rats by Administration in a Very-High-Molecular-Weight Hyaluronic Acid Eye Drop. Pharmaceutics 2024 Apr 9;16(4).
- Morén S, Kallberg M, Strom L. Equine uveitis: Outcome and adverse effects after one or two intravitreal low-dose gentamicin injections. Equine Vet J 2025 Jan;57(1):160-168.
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