Canine Eye Disease Screening and Genetics (ACVO CAER)
What to know cold
The CAER (Companion Animal Eye Registry) examination is a standardized screening performed by a board-certified ophthalmologist to identify inherited ocular disease, inform breeding decisions, and provide a permanent record. Know the process: owner and dog identification, history, complete ophthalmic exam (often with pharmacologic dilation), and a standardized form documenting normal findings or specific diagnoses. Know that the exam is a point-in-time assessment and does not guarantee the dog is free of all inherited disease; re-examination is often recommended.
Genetics concepts: simple Mendelian vs polygenic inheritance, penetrance, expressivity, and breed predispositions. High-yield examples include collie eye anomaly (CHD, autosomal recessive), progressive retinal atrophy (multiple forms, breed-specific), primary lens luxation (terrier breeds, ADAMTS17), and breed-related entropion and cataract. Understand the difference between a screening exam and genetic testing, and how each informs breeding.
Traps
Questions test the misconception that a normal CAER exam certifies a dog as genetically clear; it does not, and late-onset diseases may appear after the exam. Another trap: confusing screening with diagnosis of an individual patient, or assuming all inherited diseases are simple recessive.
Rule of thumb
A screening exam is a snapshot, not a guarantee. Worked example: a young dog of a breed with late-onset PRA screens normal at 1 year - counsel that re-examination and, where available, DNA testing are needed before breeding decisions, because the disease may not yet be detectable.