Glaucoma

Types of Glaucoma in Old English Sheepdogs

Old English Sheepdogs (OES) are predisposed to a condition called Iridocorneal Angle Abnormality (ICAA). This means the drainage structures in the front of their eyes are malformed, hindering proper fluid flow. While both eyes have ICAA, glaucoma (high pressure inside the eye) affects one eye first. The other eye has a significant risk of developing glaucoma within 6-12 months. Fortunately, using preventive medication (eye drops) in the “healthy eye” can delay the onset of glaucoma in the second eye.

Understanding the risks and types of Glaucoma

There are two main types of glaucoma to be aware of: primary and secondary. Recognizing the differences between these types is crucial in determining the appropriate treatment approach and ensuring the best possible outcome for your dog’s vision.

Primary (inherited) Glaucoma

This is more common in OES and directly linked to ICAA. Because of the malformed drainage structures, fluid builds up inside the eye, increasing pressure and potentially damaging the optic nerve and retina.

Secondary Glaucoma

This can develop due to other eye problems like inflammation, cataracts (clouding of the lens), lens luxation (displacement of the lens), trauma, tumors or as part of multiocular defect (MOD). All these factors can block fluid drainage and raise pressure inside the eye.

Key signs for recognising glaucoma in Old English Sheepdogs

Glaucoma is a serious eye disease that can severely threaten an Old English Sheepdog’s vision. Early detection is vital to preserving sight, as the warning signs of glaucoma can often be subtle. Be vigilant and watch for these indicators.

• Ocular changes: Redness in one or both eyes, excessive tearing or discharge can be early indicators.
• Light sensitivity: Does your dog squint or seem uncomfortable in bright light? This could be a sign of glaucoma.
• Visual alterations: A cloudy, hazy, or bluish appearance in the normally transparent eye might indicate trouble.
• Pupillary abnormalities: Unequal pupil sizes or a dilated pupil that doesn’t respond to light changes are cause for concern.
• Behavioral shifts: Is your OES bumping into furniture or having difficulty navigating familiar areas? These changes could be related to vision loss caused by glaucoma.
• Pain and discomfort: In severe cases, vision loss becomes more likely. Look for signs of pain or discomfort, such as avoiding bright light or pawing at the eye.

How glaucoma damages the eye

Extremely high pressure inside the eye, medically termed intraocular pressure (IOP), is the primary cause of damage in glaucoma. Imagine the delicate structures within the eye being compressed, obstructing proper blood flow. This lack of oxygen and the inability to remove waste products leads to cell death. The cornea, the transparent front part of the eye, can cloud over due to fluid buildup. The iris, the colored part of the eye, can change color due to inflammation, especially noticeable in blue-eyed dogs. Additionally, cataracts can develop within weeks of glaucoma onset.

Why glaucoma often strikes at night

Primary acute glaucoma almost always occurs during the night because pupillary dilation can cause complete closure of the iridocorneal angle, leading to a significant and rapid increase in eye pressure. This sudden rise in pressure can cause severe and irreversible damage if not detected and treated immediately.

An Old English Sheepdog’s eye before (left) and after acute primary glaucoma. This eye has lost its sight.

Comprehensive diagnostic tools for glaucoma in Old English Sheepdogs

Veterinary ophthalmologists (eye specialists) employ a thorough eye exam to diagnose glaucoma, which typically includes several key tests. While both eyes have Iridocorneal Angle Abnormality (ICAA), glaucoma affects one eye first. The other eye is at significant risk of developing glaucoma within 6-12 months. These diagnostic tools collectively provide a comprehensive assessment, enabling veterinarians to create an effective treatment plan and closely monitor the progression of glaucoma in the “healthy eye” to preserve vision and prevent further damage.

Tonometry

This painless test measures intraocular pressure (IOP), the fluid pressure within the eye. Normal IOP in dogs is generally considered less than 20 mmHg. Chronically elevated IOP, typically above 25mmHg for a sustained period, can lead to vision loss. In severe cases, where IOP reaches 40 mmHg or higher, the dog may experience significant pain and potentially require enucleation (eye removal) to alleviate discomfort.

Gonioscopy

The procedure is typically painless for dogs. This specialized examination uses a lens to directly visualize the drainage angle of the eye, which is the critical area where fluid exits. Just before performing gonioscopy, the veterinarian applies anesthetic eye drops to reduce the sensitivity of the eye’s surface, allowing the dog to keep the eye open comfortably during the exam. This test enables the veterinarian to check for Iridocorneal Angle Abnormality (ICAA) and is crucial for determining whether the glaucoma is primary or secondary.

Ultrasound Biomicroscopy (UBM)

While gonioscopy is used to diagnose Iridocorneal Angle Abnormality (ICAA), UBM offers a more detailed examination to assess whether glaucoma is developing in the other eye. UBM uses high-frequency sound waves to create detailed images of the eye’s interior, including the cornea, iris, ciliary body, and drainage angle. This technique is particularly useful for monitoring the eye that has not yet been affected by glaucoma. If UBM shows that the second eye has not yet developed glaucoma, preventive treatments, such as eye drops, may be used to delay its onset. While these eye drops are not effective in reducing pressure in an eye already affected by primary glaucoma, they can be valuable in preventing the development of glaucoma in eyes with severe ICAA.

Fundic Examination

During this examination, the veterinarian will use an ophthalmoscope, a specialized instrument, to examine the back of the eye, also known as the fundus. This allows for the evaluation of potential damage to the retina and optic nerve, both of which can be affected by high IOP in glaucoma.

Assessing glaucoma severity in Old English Sheepdogs

Veterinary ophthalmologists use a multi-faceted approach to determine the severity of glaucoma in Old English Sheepdogs, considering several key factors. By carefully evaluating these factors, veterinarians can formulate the most effective treatment plan and closely monitor the disease’s progression over time, aiming to preserve vision and prevent further damage.

Monitoring Intraocular Pressure (IOP)

IOP, the fluid pressure within the eye, is a critical indicator. Higher IOP values significantly increase the risk of optic nerve damage in a short time period. If IOP reaches a dangerous level of 50 mmHg and stays elevated for more than 6 hours, vision loss becomes a harsh reality.

Primary versus secondary glaucoma

The type of glaucoma, whether inherited (primary) or caused by another eye condition (secondary), plays a role in severity. Primary glaucoma is generally considered more serious because it progresses and affects both eyes. 

Fundus exam reveals nerve damage

A detailed examination of the back of the eye, the fundus, provides crucial clues. The veterinarian will look for signs of optic nerve damage, such as cupping (a hollowing of the nerve) or pallor (paleness), which indicate the extent of nerve damage caused by high pressure.

The role of Iridocorneal Angle Abnormality (ICAA) in Primary Glaucoma

In cases of inherited (primary) glaucoma, a critical factor is Iridocorneal Angle Abnormality (ICAA). ICAA disrupts the eye’s natural drainage system by malforming the drainage angle, the pathway where fluid exits the eye. This blockage leads to a progressive buildup of pressure within the eye, ultimately damaging the optic nerve and retina. While all Old English Sheepdogs diagnosed with primary glaucoma are confirmed to have ICAA, it’s important to note that not all dogs with severe ICAA will develop glaucoma. 

Breeding practices to minimize glaucoma risk

Fortunately, breeders can significantly reduce the prevalence of inherited glaucoma in Old English Sheepdogs through responsible breeding practices. 

ICAA Testing

Testing breeding stock for ICAA allows breeders to identify affected dogs. This vital information guides informed decisions to avoid breeding dogs with severe ICAA. 

Selective breeding

Dogs with mild or moderate ICAA should only be bred with completely unaffected dogs. This selective approach helps ensure healthier offspring with a lower risk of glaucoma. You can read more about this in our article about ICAA.

Exclusion from breeding programs

Excluding dogs with severe ICAA from breeding programs significantly lowers the risk of glaucoma in future generations of Old English Sheepdogs.

The genetic mystery of ICAA in Old English Sheepdogs

The inheritance of Iridocorneal Angle Abnormality (ICAA) in Old English Sheepdogs is still not well understood. Some dogs with severe ICAA develop glaucoma, while others do not, highlighting the need for more research. To uncover the genetic basis of ICAA and why it leads to glaucoma in some cases, researchers need more DNA samples from affected dogs, particularly those that have developed glaucoma. Contributing DNA can help in the development of a future DNA test, enabling better breeding decisions and reducing the risk of glaucoma in the breed. If you want to get involved with this research or donate DNA, please follow this link.

Managing Primary Glaucoma in Old English Sheepdogs

Primary glaucoma is a chronic condition with no cure, but with effective management, you can significantly improve your Old English Sheepdog’s quality of life. The main objectives in treatment are to control intraocular pressure (IOP) to prevent further damage to the optic nerve, manage pain, and preserve any remaining vision. Early intervention is critical—starting treatment as soon as possible greatly increases the chances of maintaining your dog’s sight.

Protecting the second eye

In Old English Sheepdogs at risk of developing glaucoma in the second eye, preventive treatment is vital. Administering medication in the “healthy eye” can significantly delay the onset of glaucoma, providing your dog with additional time of clear vision.

Prognosis and ongoing monitoring

The prognosis for glaucoma varies depending on several factors, including intraocular pressure (IOP) values and how well the dog responds to treatment. For eyes with primary glaucoma, a combination of medical (eye drops) and surgical therapy (laser treatment to reduce the production of aqueous humor, along with a gonioimplant—a small tube with a valve surgically applied to aid in eye drainage) generally results in the best outcomes. However, the prognosis for primary glaucoma remains guarded. The therapy is not curative, and although there are exceptions, most affected eyes eventually go blind. In severe cases, enucleation (removal of the eye) may be necessary to relieve pain and prevent further complications. Regular monitoring and veterinary check-ups are crucial to adapting the treatment plan as needed.

Protecting the health and vision of Old English Sheepdogs

This joint effort between breeders and owners is key to safeguarding the health and vision of Old English Sheepdogs, reducing the impact of glaucoma, and ensuring that these beloved dogs lead long, healthy lives free from the pain and challenges of this eye-disease.

Preventing glaucoma through responsible breeding

Breeders have a crucial responsibility in reducing the risk of primary glaucoma in Old English Sheepdogs. This begins with thorough testing for Iridocorneal Angle Abnormality (ICAA), a genetic defect that increases the likelihood of glaucoma. By utilizing these test results to guide breeding decisions, breeders can significantly decrease the occurrence of glaucoma in future generations, ensuring healthier and happier dogs.

Effective glaucoma management for dog owners

Understanding the importance of specialized care is equally vital. Glaucoma is a complex disease that requires early detection and expert management. General veterinarians, while knowledgeable in many areas, may lack the specific expertise needed to accurately diagnose and treat glaucoma. For example, the high intraocular pressure (IOP) associated with acute primary glaucoma can lead to retinal detachment, which may be mistakenly diagnosed by a general vet as a primary retinal disease, a different condition. This misdiagnosis can result in delayed or improper treatment, risking permanent vision loss and missing the opportunity for preventive care in the second eye.

The importance of consulting an ophthalmologist

To provide the best care for your Old English Sheepdog, it is essential to consult a veterinary ophthalmologist at the first sign of eye problems. Regular eye exams, including specialized tests such as tonometry and gonioscopy, are critical for the early detection and effective management of glaucoma. By seeking the expertise of a specialist, owners can help preserve their dog’s vision and ensure a high quality of life.