Non-progressive congenital night blindness due to dysfunction of the retinal ON pathway; daytime vision is preserved. In the horse, forms associated with TRPM1 (leopard complex) and with GRM6 have been described; the one in the Tennessee Walking Horse corresponds to GRM6. The test is complementary to the ophthalmological examination and electroretinography.

American Saddle Horse, Trotón americano, Caballo miniatura, Missouri Fox Trotting, Morgan, Cuarto de Milla, Racking Horse, Rocky Mountain, Spotted Saddle and Tennessee Walking Horse. Frequencies: limited data.

- Night blindness from birth
- Apparently normal daytime vision
- Stationary course (non-progressive)

The dossier records the variant GRM6 NC_009157.3:g.2655618C>T (XM_001916934.4:c.533C>T; p.Thr178Met; rs1138010744), on ECA14. No author or year is stated.

- Genotype breeding animals (distinguish GRM6 from TRPM1)
- Avoid matings between carriers
- Record the visual phenotype of the offspring

Differential diagnosis with other blindnesses (cerebellar atrophy, cataracts, uveitis) and with the leopard complex (TRPM1). Complementary: electroretinography and adaptometry.

1. OMIA:002692 Ceguera nocturna congénita estacionaria (GRM6) del caballo