| Inherited Retinopathies | Miscellaneous |
| Hemeralopia (achromatopsia)-progressive and non-progressive | Preoperative evaluation before cataract surgery |
| CSNB | SARDS |
| PRA | Diagnosis of retinal disorders with no ophthalmoscopic abnormalities |
Animals may be affected with both retinal degeneration and cataract at the same time, so it is obvious that cataract surgery will not restore vision if the retina is not functioning. ERG must be performed on every dog and cat that is a candidate for cataract surgery to rule out the presence of inherited retinopathy.
Because the cataract prevents a readable ophthalmoscopic evaluation of the retina, an ERG is required to determine the prognosis of the surgery. It is important to note that even in the presence of cataracts (or a corneal opacity) that affect vision, sufficient light reaches the retina to generate an electrophysiologic response, provided that the retina is functional.
For example, cases of SARDS and retrobulbar optic neuritis may present similarly with acute loss of vision; a normal-looking fundus; and fixed, dilated pupils. An ERG may be used to differentiate between the two because the response will be extinguished in SARDS (which is a retinal disease) but normal in optic neuritis (which is a postretinal disease).
Both dysplasia’s and degenerations can be detected with the help of ERG. In many dog breeds and in some cat breeds, the ERG may detect changes in retinal function long before ophthalmoscopic or behavioral signs of disease are observed. This early detection is invaluable to breeders wishing to screen their animals for inherited retinal diseases prior to breeding.
In some inherited retinopathies, such as cd in the Alaskan malamute, Gordon setter, and German shorthaired pointer or CSNB in the collie dog and Appaloosa horse, the animal presents with a normal-looking fundus. A definitive diagnosis can only be made with the ERG.
The age at onset of clinical signs is at 8 to 10 weeks, night vision is not affected, behavioural signs are obvious at birth.
Ophthalmoscopic examination reveals no funduscopic abnormalities, but an ERG will show lack of cone function, making it essential for diagnosis.
Unlike the non-progressive cd, the disease progresses and eventually rod function is also affected, and funduscopic abnormalities may be seen.
Progressive Retinal Atrophy is one of the diseases that affect photoreceptor cells.
There are two main forms of PRA recognized in dogs, early-onset or inherited form, also called retinal dysplasia, which is typically diagnosed in puppies around 2-3 months of age, and a late-onset form that is detected in adult dogs, usually between the ages of 3-9 years, called PRA.
CSNB is an inherited, congenital disease affecting night vision in horses and dogs (particularly collies). The disease does not progress to affect day vision. Ophthalmoscopic examination shows no funduscopic abnormalities, but an ERG examination demonstrates impaired bipolar cell activity, making it essential for diagnosis.
SARDS is most common in middle-aged adult dogs, especially obese, spayed females. The typical symptom is acute blindness.
As the name implies, it is a retinal degeneration of sudden onset with both cones and rods affected; the blindness is irreversible.
Pupils are dilated and non-responsive, initially, the fundus looks normal, although ophthalmoscopic signs of progressive retinal degeneration may appear over the next few months.
| BREED | DISEASE | OPHTHALMOSCOPIC SIGNS | BEHAVIORAL SIGNS | ERG ABNORMALITIES |
|---|---|---|---|---|
| Akita | PRA | 1.5-2 yrs | 1-3yrs | 1.5-2 yrs |
| Alaskan malamute | cd | Normal looking fundus | 8-10 wks | 6 wks |
| American cocker spaniel | prcd | 3-5 yrs | 3-5 yrs | 9 mos |
| Bull Mastiff | PRA | 6 mos | 6 mos | 12 mos |
| Cardigan Welsh corgi | rcd3 | 6-16 wks | 6-8 wks | 3-6 wks |
| Collie | rcd2 | 6 wks | 6 wks | 2 wks |
| Dachshund (miniature longhaired) | crd1 | 6-12 mos | 6 mos | 4-9 mos |
| Dachshund (shorthaired) | crd | 3 yrs | 3 yrs | 5 wks |
| English cocker spaniel | prcd | 4-8 yrs | 3-5 yrs | 12 mos |
| German shorthaired pointer | cd | Normal looking fundus | 8-10 wks | 6 wks |
| Irish setter | rcd1 | 12-16 wks | 6-8 wks | 3-6 wks |
| Labrador retriever | prcd | 4-6 yrs | 3-5 yrs | 1.5 yrs |
| Mastiff (Old English) | PRA | 6 mos | 6 mos | 12 mos |
| Miniature schnauzer | PRA-A | 1-2 yrs | 6-12 mos | 6-8 wks |
| Norwegian elkhound | erd | 6-12 mos | 6 wks | 5-6 wks |
| rd | 6-18 mos | 6 mos | 6 wks | |
| Papillon | PRA | 1.2-5 yrs | 7 yrs | 9 mos-1.5 yrs |
| Pit bull terrier | crd2 | 3-6 mos | 8 wks | 7 wks |
| Poodle (toy and miniature) | prcd | 3-5 yrs | 3-5 yrs | 6-9 mos |
| Portuguese water dog | prcd | 3-6 yrs | 3-5 yrs | 1.5 yrs |
| Samoyed | XLPRA1 | 1.5-2 yrs | 2-4 yrs | 6 mos |
| Siberian husky | XLPRA1 | 1.5-2 yrs | 2-4 yrs | 6 mos |
| Tibetan terrier | PRA | 10-18 mos | 6-12 mos | 10 mos |
| “This article was published in Slatter’s Veterinary Ophthalmology, 6th edition By David Maggs, BVSc(Hons), DAVCO, Paul Miller, DVM, DACVO and Ron Ofri, DVM, PhD, DECVO , Table 15-6, Copyright Elsevier (2018).” | ||||
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Substance Tables:
The table below lists substances which may be contained within LKC’s RETeval and RETevet products. Substances listed as Type 1 are within permissible levels in one or more of LKC’s products. Substances listed as Type 2 are used in the production of some components used in LKC products and may be present at trace levels, but are typically destroyed during processing.
RETeval and RETevet Devices
| Substance | CAS # | Type | Listed as causing: |
| Nickel | 7440-02-0 | 1 | Cancer |
| Acrylonitrile | 107-13-1 | 2 | |
| Ethylbenzine | 100-41-4 | 2 | |
| Crystaline Silica | 14808-60-7 | 1 | |
| Lead | 7439-92-1 | 1 | Cancer Developmental Toxicity Male Reproductive Toxicity Female Reproductive Toxicity |
| Methylene Chloride | 75-09-2 | 2 | Cancer Female Reproductive Toxicity |
| Bisphenol A | 80-05-7 | 2 | |
| N-Hexane | 110-54-3 | 2 | Male Reproductive Toxicity |