For Breeders
What is an ophthalmic screening examination?
The purpose of ophthalmic screening examinations is to identify inherited eye diseases. This is a comprehensive ophthalmic examination, so it may happen that we also find other, non-inherited abnormalities.
What is included among inherited eye diseases?
Abnormalities that:
- occur more frequently in certain breeds than in others (e.g. inherited lens luxation in terriers)
- occur more frequently among related individuals within a breed
- have a characteristic appearance and location (e.g. chorioidal hypoplasia in Collies is always located temporal to the optic disc)
- have a characteristic time of onset and progression
It is important to know that for a significant proportion of these abnormalities, the exact mode of inheritance is not known.
Who may perform ophthalmic screening?
Currently in our country, any veterinarian may perform an ophthalmic screening examination. Nevertheless, it would be ideal if this examination were performed only by those who have the appropriate ophthalmic instruments and knowledge.
What types of ophthalmic screening exist in Hungary?
In Hungary, screening is available either through examinations performed by regular members of the Small Animal Ophthalmology Society (http://kisallatszemeszet.hu/szemeszeti-szurovizsgalatok/) or through ECVO ophthalmic screening.
What does ECVO screening mean?
ECVO (European College of Veterinary Ophthalmologists) ophthalmic screening may only be performed by veterinarians who have demonstrated their knowledge in a multi-stage examination before an international committee. (https://www.ecvo.org/media/examiners_in_other_countries.pdf)
I am the only person in Hungary who has passed this examination.
Who is ECVO screening recommended for?
West of us, a screening certificate is generally required for pedigree registration, and almost only screenings performed by an ECVO panellist are accepted. Therefore, this examination is strongly recommended for those who wish to register or use their dog for breeding in these countries.
Can the examiner exclude any individual from breeding based on the examination?
No. It is important to emphasize that the person performing the ophthalmic screening is not a decision-maker and can only provide a recommendation. The final decision must be made by the breeding organization — it is they who must regulate which affected individuals are accepted for breeding and which are excluded.
What recommendations can be given?
- Breeding with the affected individual is not recommended if the abnormality is proven to be inherited and/or if it causes significant impairment of vision or of another function of the eye (e.g. progressive retinal atrophy).
- If the abnormality is presumably inherited but does not cause a vision problem and does not impair any other function of the eye, the individual may remain in the breeding programme — since excluding every single dog would significantly narrow the gene pool and thereby risk the emergence of new problems.
Can genetic testing replace clinical screening?
Unfortunately, only very rarely. Compared to the large number of diseases known to be inherited, the exact mode of inheritance is known for only very few. Many laboratories offer combined tests that screen for several diseases at once, but it is important to know that a single disease can be caused by multiple mutations. Moreover, it may happen that the breed in question is not even affected by a given disease, so a negative result may look reassuring but is actually worthless. Before requesting a genetic test, make sure that the disease in question actually occurs in that breed, and if so, whether the affected gene segment is known (https://www.ecvo.org/hereditary-eye-diseases/ecvo-manual/chapter-9-breeds-dogs.html).
Why did we create the standardized screening form?
In Hungary, although there are breeds for which ophthalmic screening is mandatory, until now no standardized screening form had been introduced, nor any required set of instruments.
Following the model of the ECVO (European College of Veterinary Ophthalmology) ophthalmic screening examination, the Hungarian Small Animal Ophthalmology Society introduced a standardized, online-fillable screening form at the beginning of 2019, along with an accompanying database, so that we will soon be able to provide statistics on the prevalence of various conditions in breeds found in Hungary. Also based on the ECVO screening regulations, we established a list of the ophthalmic instruments absolutely required for screening. Every member performing ophthalmic screening must have the following equipment: a direct ophthalmoscope, a binocular slit-lamp biomicroscope with at least 10x magnification, an indirect ophthalmoscope together with the magnifying lenses used with it, a tonometer (intraocular pressure meter), and a gonioscopy lens. All of these instruments are essential for a thoroughly conducted ophthalmic screening examination.
The contact details of colleagues who perform ophthalmic screening can be found here: http://kisallatszemeszet.hu/szemeszeti-szurovizsgalatok/
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