Glaucoma comprises a group of diseases that ultimately result in optic nerve head circulation damage, retinal ganglion cell death, and irreversible blindness.1-3 It is a common and painful cause of blindness in dogs, affecting nearly 0.9% of purebreds in North America.4
Levels of Care The goal of the practitioner should be to determine:
- Whether glaucoma is the correct diagnosis
- Whether glaucoma is primary or secondary
- Whether it is acute or chronic.
Once these determinations are made, a treatment plan can be developed.
Diagnosis A glaucoma diagnosis is established by measuring intraocular pressure (IOP) in all red eyes. IOP varies with species, age, breed, time of day, method of restraint, tonometrist, and tonometer. Younger dogs have a higher normal IOP than older ones. The normal IOP range should be established by the tonometrist; in our practice, using a Tono-Pen (reichert.com), we consider normal IOP to be between 8 and 20 mm Hg. Routine screening of dog breeds predisposed to primary glaucoma makes purchase and use of a tonometer cost-effective.
Primary or Secondary Primary glaucoma is caused by abnormal anatomy of the iridocorneal angle and usually occurs between 3 and 9 years of age, rarely in mixed breed dogs. Glaucoma can also be secondary to other eye diseases and conditions, including anterior lens luxation (inherited in at least 45 breeds, including most types of terriers, basset hounds, beagles, and Arctic circle breeds2), chronic anterior uveitis, chronic long-standing cataracts, prior cataract surgery, retinal detachment, hyphema, and intraocular neoplasia. It is not always obvious whether glaucoma is primary or secondary, but effective treatment varies depending on underlying cause.
Acute or Chronic