Hereditary ocular disease of the Shar Pei in which primary open-angle glaucoma and lens luxation coexist, caused by the same variant of the ADAMTS17 gene. The defect in the extracellular matrix of the zonules and of the iridocorneal angle reduces aqueous humour drainage and favours lens instability, with increased intraocular pressure, pain and blindness. It is inherited in an autosomal recessive manner.

Affected breed: Shar Pei (Chinese). No reliable large-scale population frequencies are published; the disease is known in the breed and a genetic test is available for the Shar Pei.

- Increased intraocular pressure with an open angle\n- Ocular pain, redness and blepharospasm\n- Lens luxation or subluxation (may precede or follow the glaucoma)\n- Mydriasis and decreased pupillary reflex\n- Optic nerve atrophy and blindness\n- Occasionally, sclera/iridian stroma thinned by defective zonulopoiesis

Primary glaucoma and lens luxation have been recognised separately in the Shar Pei for years, but their molecular relationship was not established until the study by Oliver and colleagues (2018). By resequencing the ADAMTS17 exons in 10 affected Shar Peis, they identified a homozygous 6-bp deletion in exon 22 (c.3069_3074del) that removes two highly conserved valine residues in the accessory domain of the protein. The variant segregated with the phenotype (POAG, PLL or both) in 63 Shar Peis and was not detected in 95 dogs of other breeds. ADAMTS17 expression in ocular tissue of the affected dog was reduced ~4.2-fold.

- Test Shar Pei breeding animals with the ADAMTS17 test (POAG/PLL)\n- Do not mate two carriers: 25% risk of affected homozygotes\n- A carrier may be mated with a clear dog; offspring intended for breeding must be tested\n- Prioritise breeding dogs that will not develop the disease as the main objective, and reduce the allele frequency as a long-term objective\n- Exclude affected animals from breeding and monitor them clinically at an early stage

It is difficult to differentiate clinically whether lens luxation is primary or secondary to glaucoma, so in practice both processes are considered together as POAG/PLL in the breed. Differential diagnosis with glaucoma secondary to uveitis or tumour and with traumatic luxation. Gonioscopy and biomicroscopy guide; confirmation is molecular. Periodic ophthalmological monitoring of homozygotes allows early interventions and a better visual prognosis.

1. Oliver JAC, Rustidge S, Pettitt L, et al. (2018) Evaluation of ADAMTS17 in Chinese Shar-Pei with primary open-angle glaucoma, primary lens luxation, or both. Am J Vet Res 79:98-106. PMID: 29287154
2. Lazarus JA, Pickett JP, Champagne ES, et al. (1998) Primary lens luxation in the Chinese Shar Pei: clinical and hereditary characteristics. Vet Ophthalmol 1(2-3):101-107. PMID: 11397217