PRA in Shih Tzus: Detecting Progressive Retinal Loss Early

[Progressive retinal atrophy](https://seniorpet.org/knowledge/siamese-cat-progressive-retinal-atrophy "Progressive Retinal Atrophy Guide") (PRA) is a group of inherited retinal degenerations that cause progressive vision loss and eventual blindness. Shih Tzus are a [brachycephalic](https://seniorpet.org/knowledge/persian-cat-brachycephalic-airway "Brachycephalic Syndrome Guide") toy breed with several eye-specific vulnerabilities — including proptosis, corneal disease and dry eye — and PRA is an important cause of vision impairment in older Shih Tzus. This article explains how PRA typically presents in senior Shih Tzus (age 9–10 years for this breed), how it is diagnosed early, how it differs from other eye problems common in the breed, and practical steps owners can take to protect vision and [quality of life](https://seniorpet.org/knowledge/siamese-cat-quality-of-life "Quality of Life Assessment").

Why PRA matters for older Shih Tzus

Shih Tzus have a lifespan of roughly 10–16 years. By 9–10 years many Shih Tzus enter the “senior” life stage when age-related conditions become more common. PRA is particularly significant because:

• It is progressive and irreversible once retinal neurons are lost.
• Early retinal dysfunction can precede owner-noticed vision loss by months to years.
• Coexisting brachycephalic skull conformation and frequent corneal disease can complicate both diagnosis and management.
• Early detection allows timely adaptation of the dog’s environment, monitoring for complications, and evaluation for supportive therapies or clinical trials.

PRA is not the only eye disease to worry about in Shih Tzus. The breed is predisposed to proptosis (eye displacement after trauma), keratoconjunctivitis sicca (dry eye, KCS), corneal ulcers, and cataracts. Distinguishing PRA from these conditions is essential for prognosis and treatment planning.

How PRA typically presents in Shih Tzus

General pattern

• Night vision declines first: PRA usually affects rod photoreceptors before cones in many forms of PRA. Owners often notice difficulty navigating in dim light, hesitance on stairs at night, or “slower” eyes when lights are low.
• Daytime vision loss follows and progresses over months to years.
• The rate of progression varies by the genetic form of PRA; in some dogs it’s insidious over many years, while in others it can be faster.

Breed-specific notes for Shih Tzus

• Because Shih Tzus already have relatively prominent eyes and are prone to corneal disease, some owners may confuse corneal clouding or scarring with retinal disease. Retinal changes occur on fundic (back-of-eye) exam rather than corneal surface.
• Shih Tzus often show very adaptive behavior and may mask early deficits; subtle changes in night navigation or increased startle responses are important clues.
• Secondary cataract formation can mask pupillary responses and make a retina-based diagnosis harder on routine exam; objective testing (ERG) is frequently needed.

Common owner-reported early signs

• Hesitation on stairs or in dim rooms
• Bumping into furniture in low light but navigating well by day
• Slower to find food bowls at night
• Increased reliance on scent or hearing to locate people/objects

How veterinarians detect PRA early

A thorough approach involves history, ophthalmic exam, objective testing, and genetic assessment when available.

Ophthalmic examination

• Direct and indirect ophthalmoscopy to inspect the retina, optic disc, and retinal blood vessels. Early PRA may show subtle tapetal reflex changes or small focal retinal changes.
• Schirmer tear test (for KCS), fluorescein stain (for corneal ulcers), intraocular pressure (to screen for glaucoma), and anterior segment evaluation — all important because coexisting anterior eye disease is common in Shih Tzus.

Electroretinography (ERG)

• ERG is the gold-standard objective test for retinal function. It measures electrical responses of rod and cone photoreceptors and can detect dysfunction before owners notice vision loss and before fundic changes are evident on exam. For Shih Tzus with suspected early PRA, ERG can confirm rod dysfunction consistent with PRA even when the retina looks relatively normal.
• ERG requires sedation or brief anesthesia and referral to a veterinary ophthalmologist or specialty center.

Optical coherence tomography (OCT) and fundus imaging

• OCT provides cross-sectional imaging of retinal layers and can detect thinning of photoreceptor layers. Fundus photography documents progression over time.
• These modalities are increasingly available at specialty centers and are useful for monitoring progression.

Genetic testing

• Multiple genes are implicated in different forms of PRA across breeds. Commercial canine genetic testing laboratories offer panels that include some PRA mutations. Testing can:

- Confirm a known breed-specific mutation when one is identified. - Help with breeding decisions in younger dogs (less relevant for a senior pet, but useful if the dog is intact). - Not all forms of PRA are covered by current tests — a negative test does not rule out PRA if clinical or ERG evidence exists.

• Discuss with your primary veterinarian or an ophthalmologist which tests are appropriate for Shih Tzus.

Clinical research references

• Veterinary ophthalmology textbooks and ACVO guidelines emphasize ERG as the objective test to detect retinal dysfunction early (Gelatt, E. Gelatt’s Veterinary Ophthalmology; American College of Veterinary Ophthalmologists [ACVO] clinical resources).
• Gene therapy for certain canine retinal diseases (e.g., RPE65-associated disorders) has been demonstrated in dogs and humans, illustrating the potential for disease-specific interventions in the future (Acland et al., Hauswirth et al.). These are presently applicable only to specific mutations and within research/clinical trial settings.

Distinguishing PRA from other Shih Tzu eye problems

Because Shih Tzus commonly have front-of-eye disease, it’s important to distinguish visual deficits stemming from corneal disease or cataract from genuine retinal degeneration.

Signs more likely with corneal disease

• Pain (blepharospasm, tearing, pawing at the eye)
• Visible corneal clouding, ulceration, pigmentation, or scarring on the surface
• Fluorescein-positive corneal defects

Signs more likely with cataract

• White, opaque lens on exam
• Reduced menace response and pupillary light reflexes may be altered but the retina could still be functional

How to proceed if you suspect vision loss

• Ask for a referral to a veterinary ophthalmologist for ERG and retinal imaging.
• If the cornea is diseased or cataract is present, treat those conditions aggressively — resolving surface disease may reveal whether vision is retina-mediated.
• Keep in mind that PRA can occur concurrently with cataracts; an ERG helps determine whether cataract surgery would be beneficial.

Practical steps for owners to detect PRA early

Daily and weekly observations

• Check night navigation: walk the dog in a dimly lit hallway or room and note any hesitation or bumping.
• Monitor for changes in behavior: reluctance to go down stairs, increased startle, slower response to commands, or increased reliance on smell.
• Routine photos and videos can document subtle changes over months.

Ask your veterinarian to perform

• Annual to biannual ophthalmic exams in senior Shih Tzus (every 6–12 months after age 8–9). The precise interval can be individualized based on previous eye history; dogs with existing corneal disease or cataracts may need more frequent exams.
• Schirmer tear tests and fluorescein stains during wellness visits to identify treatable front-of-eye disease early.
• Referral for ERG if night-vision loss is suspected, if fundic exam is equivocal, or if owners notice progressive changes.

Preparing for specialty referral

• Bring a timeline of symptoms and photos/videos showing behavior changes.
• Have prior ophthalmic records and any genetic test results available.
• Discuss anesthesia risk factors beforehand: senior dogs may require pre-anesthetic bloodwork and cardiac assessment.

Table: Suggested screening and action plan for senior Shih Tzus (age 9–10 and older)

| Screening/action | Frequency (senior Shih Tzu) | Purpose/what it detects | |---|---:|---| | General wellness exam + basic bloodwork (CBC, chemistry) | Every 6–12 months | Baseline for anesthesia, detect systemic disease (kidney disease common in seniors) | | Routine ophthalmic exam (vet) | Every 6–12 months (sooner if signs) | Detect corneal disease, cataracts, obvious retinal changes | | Schirmer tear test and fluorescein stain | At each ophthalmic exam or sooner if discharge/irritation | Detect KCS and corneal ulcers early | | Funduscopic exam by general practitioner | Annually | Detect tapetal changes, vessel attenuation; may miss early PRA | | Referral ERG + retinal imaging (ophthalmologist) | If night vision loss suspected or fundus atypical; baseline once in early senior years recommended | Detect subclinical retinal dysfunction (objective confirmation of PRA) | | Genetic testing for PRA mutations | Once if available for the breed | May identify known mutations (useful for diagnosis and breeding information) |

Management options and supportive care

There is currently no universally effective cure for PRA once retinal neurons are lost. Management focuses on early detection, supportive care to preserve remaining vision and quality of life, and addressing concurrent ocular disease.

Medical and surgical treatments

• No proven medical therapy halts most forms of PRA. Nutritional supplements (omega-3 fatty acids, antioxidants) are sometimes recommended; evidence of benefit is limited and disease-specific.
• Treat concurrent anterior segment disease vigorously: manage dry eye (topical cyclosporine or tacrolimus), repair corneal ulcers, and control ocular surface inflammation. Uncontrolled corneal disease can cause pain and further vision compromise.
• Cataract surgery is only considered if the retina is functional (confirmed with ERG). Many Shih Tzus with PRA develop cataracts; removing a cataract when the retina is nonfunctional will not restore useful vision.
• For specific genetic forms (e.g., RPE65-associated), gene therapy has been successful in dogs and humans but is not applicable to most PRA cases and is generally only available through clinical trials or specialized centers.

Environmental and quality-of-life modifications

• Improve lighting and contrast at home: use consistent lighting on night routes, avoid moving furniture frequently, and provide non-slip surface rugs.
• Maintain a predictable environment and routines — Shih Tzus adapt well when the environment is consistent.
• Use scent and sound cues: scented mats at feeding stations, bells on family members, and gentle verbal cues.
• Prevent injuries: block off stairs or install ramps, use harnesses instead of collars to reduce neck strain, and avoid sudden changes that could frighten a visually-impaired dog.

Behavioral and safety tips specific to Shih Tzus

• Monitor for mouth/periodontal disease that may cause discomfort and affect appetite; [dental disease](https://seniorpet.org/knowledge/siamese-cat-dental-disease "Dental Disease in Senior Pets") is common in small breeds and can exacerbate systemic disease.
• Because Shih Tzus are brachycephalic, avoid overheating and over-exertion — a visually impaired [Shih Tzu](https://seniorpet.org/knowledge/breed/shih-tzu "Senior Shih Tzu Health Guide") may be less able to signal respiratory distress.
• Keep the dog’s weight healthy to lessen stress on the spine (reducing risk of intervertebral disc disease) and airway.

Interacting medical conditions in senior Shih Tzus

When evaluating a senior Shih Tzu for PRA, consider these common comorbidities:

Periodontal disease

• Small-breed dogs, including Shih Tzus, have a high lifetime risk of dental disease. Chronic dental infection increases systemic inflammatory burden and complicates anesthesia planning for diagnostics or surgery.
• Action: daily tooth brushing and regular professional dental care; pre-anesthetic dental evaluation and prophylaxis.

[Chronic kidney disease](https://seniorpet.org/knowledge/siamese-cat-kidney-disease "Chronic Kidney Disease Management") (CKD)

• CKD is common in older small-breed dogs. Pre-anesthetic bloodwork and blood pressure checks are important before ERG or potential procedures.
• Action: ensure renal function is evaluated prior to sedation or surgery; manage CKD per your veterinarian’s protocol.

Brachycephalic airway syndrome (BAS)

• BAS increases anesthetic risk and can complicate recovery from sedation required for ERG or surgery.
• Action: pre-anesthetic airway assessment, consider lighter sedation protocols when possible, and work closely with the anesthesiologist and veterinary ophthalmologist.

Intervertebral disc disease (IVDD)

• While classic chondrodystrophic breeds are at highest risk, small breeds like Shih Tzus may develop IVDD. Mobility limitations from IVDD can combine with vision loss to impair quality of life.
• Action: low-impact exercise, avoid excessive jumping, use ramps and harnesses, and seek veterinary neurology advice if back/neck pain or neurologic signs appear.

When to see the vet urgently

Seek immediate veterinary attention if your Shih Tzu shows:

• Sudden, dramatic vision loss in one or both eyes
• Eye pain, squinting, sudden cloudiness, or a bulging eye (possible proptosis)
• Redness, discharge, or signs of corneal ulceration
• Marked neurologic signs, sudden weakness, or pain suggesting spinal disease

For suspected PRA without acute pain, schedule a non-urgent ophthalmic referral for ERG and retinal imaging. Early detection allows time to plan and implement environmental and medical support.

Questions to ask your veterinarian or ophthalmologist

• Based on my dog’s history and exam, what is the most likely cause of the vision changes?
• Should we perform an ERG or retinal imaging for early detection?
• Is genetic testing recommended for my Shih Tzu, and which laboratory do you recommend?
• Are there treatable eye diseases (dry eye, corneal ulcers, cataracts) that we should address now?
• What is the anesthesia plan and risk mitigation for a senior Shih Tzu, given potential kidney or airway disease?
• Are there clinical trials or novel treatments appropriate for my dog’s type of PRA?

Prognosis and planning

PRA typically results in gradual loss of vision. With early detection, many Shih Tzus adapt well to reduced vision, especially when owners proactively modify the home and routines. Dogs are highly scent-driven and can maintain a good quality of life even with substantial visual loss.

Work with your veterinarian to:

• Establish a monitoring and re-evaluation schedule (ophthalmology exams and supporting tests)
• Manage concurrent conditions (dental disease, CKD, BAS, IVDD)
• Evaluate the dog’s environmental needs and safety measures
• Discuss palliative and quality-of-life planning if progression is rapid

Final practical checklist for Shih Tzu owners (age 9–10 and older)

• Observe for early signs: test night navigation periodically and keep a log of changes.
• Schedule ophthalmic exams at least every 6–12 months; ask about referral for ERG if any change is suspected.
• Maintain excellent dental care: brush teeth daily, schedule professional cleanings as recommended.
• Screen for systemic disease: regular bloodwork and blood pressure checks before sedated procedures.
• Modify the home: consistent furniture placement, night lighting, ramps for furniture, non-slip rugs.
• Protect the eyes: manage dry eye aggressively and prevent corneal injury; use protective collars when indicated.
• Discuss genetic testing and potential research trials with your vet/ophthalmologist.

Early recognition of PRA in Shih Tzus gives you and your veterinary team the best chance to preserve vision for as long as possible, manage coexisting eye and systemic diseases, and maintain your dog’s quality of life. If you suspect any change in your Shih Tzu’s vision, contact your veterinarian promptly to set up an ophthalmic evaluation and discuss whether ERG and genetic testing are appropriate for your pet.

References and further reading

• Gelatt KN. Gelatt’s Veterinary Ophthalmology. 5th ed. 2013. (textbook reference on diagnostic ophthalmology and ERG)
• American College of Veterinary Ophthalmologists (ACVO) clinical resources and position statements on eye exams and ERG.
• Acland, GM., et al. (2001–2008 series). Studies documenting successful gene therapy for specific canine retinal diseases (e.g., RPE65) and implications for translational therapy.

(Ask your veterinarian for current peer-reviewed articles and specialty resources relevant to PRA in Shih Tzus; diagnostic capabilities and clinical trials are evolving.)