Equis ISSN 2398-2977

Therapeutics: eye

Contributor(s): Paul Gerding, Graham Munroe

Introduction

  • Always demonstrate administration of drugs to the eye for owners who will be instilling preparations unsupervised.
  • Culture and sensitivity/cytology is a routine part of the diagnosis of eye infections → modify initial broad-spectrum antibiosis according to microbiologic results.
  • Topical preparations are preferable to systemic.
  • If medication is applied bilaterally where one eye is being treated prophylactically, treat the unaffected eye first to avoid cross contamination during administration.
  • There are 3 barriers to the passage of drugs into the eye:
    • Corneal epithelial layer.
    • Blood-aqueous barrier. 
    • Blood-retinal barrier.
  • Corneal epithelial layer:
  • Blood aqueous barrier:
    • Junctions between cells of the non-pigmented ciliary body epithelium and the iris capillary endothelium.
  • Blood retinal barrier:
    • Intercellular junctions:
      • Vascular endothelium of retinal vessels and choroidal vessels.
      • Retinal pigment epithelium.
  • Factors determining how well drugs cross these barriers:
    • * Lipid solubility.
    • * Hydrophilic or polar drugs.
    • * Protein binding affinity.
    • Molecular weight.
  • Damage or disease to barriers: affects their function - usually increasing the passage of drugs, eg uveitis Uveitis: anterior - overview.
  • Topics contained within this section:
    • Anti-infectives.
    • Anti-inflammatories.
    • Mydriatics and cycloplegics.
    • Local anesthetics.
    • Miscellaneous preparations and uses.
    • Methods of administration.

Types of drugs available for therapy of the eye

  • Antibiotics:
    • Topical.
    • Subconjunctival.
    • Systemic.
    • Intra-ocular.
  • Antifungals:
    • Topical.
    • Subconjunctival (miconazole Miconazole).
  • Antiviral:
    • Topical only.
  • Anti-inflammatory drugs:
    • Corticosteroids - topical/subconjunctival/systemic.
    • Non-steroidal drugs - topical/systemic.
    • Antihistamines - topical/systemic.
    • DMSO Dimethyl sulfoxide - topical/systemic.
  • Autonomic drugs:
    • Parasympathomimetics (miotics) - topical.
    • Parasympatholytics (mydriatics) - topical.
    • Sympathomimetics - topical.
  • Disinfectants:
    • 1% povidone-iodine Povidone-iodine solution diluted in saline - topical.
  • Corneal dehydrating agents:
    • 5% hypertonic saline ointment - topical.
  • Artificial tears - topical.
  • Ocular lubricants - topical.
  • Anticollagenase drugs - topical:
    • EDTA:
      • 0.2-1% K or Na EDTA in artificial tears.
      • 5 ml saline in 7 ml vacutainer EDTA anticoagulant.
      • Impairs healing - withdraw rapidly once repair started.
    • Acetylcysteine:
      • 5% mucinolytic → long-term degrades tear film.
      • 2-3 days at most.
    • Serum.
    • Povidone-iodine Povidone-iodine.
    • Tetracycline Therapeutics: tetracyclines:
      • Doxycycline 0.1% solution in artificial tears.
      • q1-2h.
  • Irrigating solutions - topical:

Anti-infectives

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Anti-inflammatories

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Mydriatics and others

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Administration

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lavach J K et al (1984) Current concepts in equine ocular therapeutics. Vet Clin North Am Large Anim Pract (3), 435-449 PubMed.
  • Tammeus J et al (1983) Therapeutic extended wear contact lens for corneal injury in a horse.  JAVMA 182 (3), 286 PubMed.
  • Frauenfelder H et al (1979) Placement of a subpalpebral catheter in a standing horse. Vet Med Small Anim Clin 74 (5), 724-730 PubMed.

Other sources of information

  • Matthews A (2004) Ophthalmic Therapeutics. In: Equine Clinical Pharmacology. Eds: Bertone J J & Horspool L J I. Saunders, UK. pp 217-245.
  • Derived from The Veterinary Formulary (2001) Ed: Bishop Y. 5th edn. Pharmaceutical Press; published is association with the British Veterinary Association, UK.


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