Glaucoma is a group of heterogeneous ocular disorders that cause damage to the retina and optic nerve, which results in irreversible blindness. Primary glaucoma is typically a bilateral disease, however both eyes may not be affected simultaneously.The two most common clinical types of glaucoma in humans and dogs are primary open-angle (POAG) and primary angle-closure glaucoma (PACG). It is estimated that PACG will affect 21 million people in the world by the year 2020 and that 5.3 million will be bilaterally blind. The proportion of all cases affected by significant visual loss is three times higher in PACG than POAG, as considerable damage can occur before symptoms become apparent.

It has been noted that PACG is more prevalent in Asian Indians, Chinese, Inuit and Yupik populations as well as several dog breeds including cocker spaniels, basset hounds, shar-peis, Siberian huskies and chow-chows. In addition, sex plays a role in both humans and dogs as females are overrepresented with this type of glaucoma. As there is a high incidence of PACG among siblings and offspring of affected parents, it is very likely that genetics plays a relevant role in the occurrence of this disease. It has been suggested that several genetic variants, as well as environmental factors (i.e. low sunlight exposure, higher temperatures, atmospheric pressure) and age contribute to the development of PACG.

One way to determine some of the genes that are associated with PACG is by comparing a large group of healthy individuals with another large group of individuals that are affected with glaucoma. This type of genetic analysis is made possible by using genome-wide association studies (GWAS), which allows the identification of significant associations with regions of the genome containing causative mutations for complex diseases such as PACG.

Several susceptibility genetic loci and single nucleotide polymorphisms have been identified as contributing to the development of PACG. GWAS have identified 9 genes/loci for the common adult-onset form of PACG in humans. In basset hounds, 3 genetic loci have been associated with a predisposition for PACG, however no studies have been performed to determine if the genes involved with human PACG are also predisposing factors for PACG in dogs.Therefore, it would be helpful to recognize if dogs affected by PACG carry mutations in the same contributing genes that influence the development of this disease in humans and if these genes contribute to the development of PACG in dogs, so that new animal models can be developed to better understand and establish new genetic therapies for this disease.