Eye  Information

Description and Comments of Eye Problems within the breed
A. Entropion-  A conformational defect resulting in "in-rolling" of one or both of the eyelids which may cause ocular irritation. It is likely that entropion is influenced by several genes (polygenic), defining the skin and other structures, which make up the eyelids, the amount and weight of the skin covering the head and face, the orbital contents, and the conformation of the skull.
B. Distichiasis -Eyelashes abnormally located on the eyelid margin, which may cause ocular irritation. Distichiasis may occur at any time in the life of a dog. It is difficult to make a strong recommendation with regard to breeding dogs with this entity. The hereditary basis has not been established, although it seems probable due to the high incidence in some breeds. Reducing the incidence is a logical goal. When diagnosed, distichiasis should be recorded; breeding discretion is advised.
2 C. Corneal dystrophy - epithelial/stromal A non-inflammatory corneal opacity (white to gray) present in one or more of the corneal layers; usually inherited and bilateral.
D. Persistent pupillary membranes (PPMs) Persistent blood vessel remnants in the anterior chamber of the eye which fail to regress normally by 3 months of age. These strands may bridge from iris to iris, iris to cornea, iris to lens, or form sheets of tissue in the anterior chamber. The last three forms pose the greatest threat to vision and when severe, vision impairment or blindness may occur.
E. Cataract -Any opacity of the lens and/or its capsule, regardless of size or location within the lens. Cataracts are assumed to be hereditary unless associated with known trauma, senility, ocular inflammation, specific metabolic diseases, or nutritional deficiencies.
F. Persistent hyperplastic primary vitreous (PHPV)/Persistent hyperplastic tunica vasculosa lentis (PHTVL) Persistent hyperplastic primary vitreous is a congenital defect resulting from abnormalities in the development and regression of the hyaloid artery (the primary vitreous) and the interaction of this blood vessel with the posterior lens capsule/cortex during embryogenesis. This condition is often associated with persistent hyperplastic tunica vasculosa lentis which results from failure of regression of the embryologic vascular network which surrounds the developing lens. The latter fails to regress within the first 2-3 weeks after birth. The defect is currently graded in 6 levels of severity, in which Grade 1 is characterized by uni- or bilateral small, white to brown dots of fibrous tissue mainly centrally, retrolentally on the posterior capsule of the lens. These are stationary and do not affect vision. The more severe forms Grade 2-6 (Grade 2: More extensive central posterior capsular cataract with yellow-brown capsular/retrolental fibrous tissue, Grade 3: Persistent tunica vasculosa lentis-hybrid system vessels appearing as a meshwork with combined grade 2 abnormalities, Grade 4: Lenticonus of varying extent combined with more or less extensive elevation and grade 2 abnormalities, Grade 5: Combination of Grade 3 and 4, Grade 6: Combinations of the first five grades, such as lens coloboma, microphakia, larger retrolental clots of pigment or red material like free blood) usually occur bilaterally and cause visual impairment or blindness. Grade 1: Pass (breeder option) Grade 2-6: Fail (No pass) The majority of affected dogs have a retrolental fibrovascular plaque and variable lenticular defects which include posterior lenticonus/globus, colobomata, intralenticular hemorrhage and/or secondary cataracts. Vision impairment may result. The disease is an inherited disorder in the breed, but the mode of inheritance has not been defined. The results of current studies cannot rule out autosomal recessive or a dominant trait with incomplete penetrance.
G. Persistent hyaloid artery remnant (PHA) Congenital defect resulting from abnormalities in the development and regression of the hyaloid artery. The blood vessel remnant can be present in the vitreous as a small patent vascular strand (PHA) or as a non-vascular strand that appears gray-white (persistent hyaloid remnant).
H. Retinal dysplasia - folds Linear, triangular, curved or curvilinear foci of retinal folding that may be single or multiple. When seen in puppies, this condition may partially or completely resolve with maturity. Its significance to vision is unknown. There are two other forms of retinal dysplasia (geographic, detached) which are known to be inherited in other breeds and, in their most severe form, cause blindness. The genetic relationship between folds and more severe forms of retinal dysplasia is undetermined.
References 1. ACVO Genetics Committee and/or Data from OFA All-Breeds Report.