Pectinate ligament dysplasia and glaucoma in Flat Coated Retrievers. II. Assessment of prevalence and heritability

Abstract

Pectinate ligament dysplasia (PLD) in dogs is a congenital ocular abnormality affecting the iridocorneal angle, the presence of which may be associated with adult-onset primary glaucoma. This study demonstrates a significant association between PLD and glaucoma in Flat Coated Retrievers, and also a higher prevalence of PLD in Flat Coated Retrievers compared with other breeds. It is shown that the association between PLD and glaucoma was robust and not due to a small increase in PLD with age. There was also a significant association between PLD in offspring and parents and, using the offspring-parents regression, the heritability of PLD was estimated as approximately 0.7. As glaucoma is significantly related to PLD, glaucoma may also be heritable. Thus, glaucoma can be controlled by gonioscopic examination and elimination of animals with a high degree of PLD from a breeding program. Breeding from only those animals with a moderate or low PLD value or score should limit the expected prevalence of glaucoma in the resulting population to < 0.2%. The preceding study describes in detail the PLD survey, gonioscopic technique and some initial results obtained prior to this epidemiological investigation.

Definition, Classification, and Pathophysiology of Canine Glaucoma

“…[34][35][36] Goniodysgenesis, a defect in the development of the angle associated with decreased angle width and/or malformation of the pectinate ligament, has genetic causes in humans and likely in dogs, considering its high incidence in specific breeds. 37,38 Wyman and Ketring 39 reported an incidence of 63% in normotensive basset hounds, whereas in normotensive flat-coated retriever and Bouviers the incidences of different grades of goniodysgenesis were 35% and 75% respectively.…”

“…37,38 Wyman and Ketring 39 reported an incidence of 63% in normotensive basset hounds, whereas in normotensive flat-coated retriever and Bouviers the incidences of different grades of goniodysgenesis were 35% and 75% respectively. 35,40 The rate of goniodysgenesis in a control group of arbitrarily chosen breeds was 6%. 35 However, the highest overall incidence of glaucoma in the predisposed breeds does not exceed 6%, 26 whereas the reported incidence of goniodysgenesis can be up to 10 times higher.…”

“…35,40 The rate of goniodysgenesis in a control group of arbitrarily chosen breeds was 6%. 35 However, the highest overall incidence of glaucoma in the predisposed breeds does not exceed 6%, 26 whereas the reported incidence of goniodysgenesis can be up to 10 times higher. 39,40 Rates of glaucoma in colonies of predisposed breeds descending from the same ancestor and in which strict genetic connections can be assumed reach 10%.…”

“…Involvement of 75% or more of the circumference of the angle is associated with an extremely high risk of glaucoma, whereas involvement of less than 25% is usually considered a variation of normal. 35 A few studies have also reported the grade of goniodysgenesis to be dynamic and to progress with age in certain normotensive dogs. 36,43 …”

Genetics of eye disorders in the dog.

“…A strong and significant correlation between goniodysgenesis and glaucoma was reported in the Great Dane, and the same study reported a high heritability for goniodysgenesis, suggesting glaucoma may be heritable in this breed [138]. A similarly significant association has been reported between pectinate ligament dysplasia and adult-onset primary glaucoma in the Flatcoated retriever, for which the heritability was estimated to be approximately 0.7 [139,140]. To date no mutations have been identified that are associated with angle closure glaucoma in any breed of dog although the first glaucomaassociated locus has recently been identified in Dandie Dinmont Terriers [141].…”