Inherited diseases of the eye are the best described and characterized of all known inherited conditions in the dog, over 30 mutations have been published to date. Among those described are disorders of the retina, lens as well as markers specific to glaucoma. Unfortunately, many of these ocular disorders are relatively un-treatable in the affected individual and testing is more applicable to utilize in breeding animals to lower the prevalence within at-risk breeds. This screening tests includes a test specifically for primary lens luxation which can be an acute and very painful condition requiring surgical treatment.
What is Primary Lens Luxation?
Displacement of the lens into the anterior chamber of the eye is typically quite painful and can result in increased intraocular pressure and glaucoma if not treated promptly. Having owners watch for warning signs and making plans for immediate medical treatment may increase chances of a positive outcome. Early intervention with glaucoma medications or surgery prior to full luxation may be indicated to decrease the chance of surgical complications.
- Lens Luxation = complete dislocation of the lens
- Lens Subluxation = partial dislocation of the lens
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Primary lens luxation was initially discovered in the Miniature Bull Terrier, Jack Russell Terrier and Lancashire Heeler.
Since the initial publication, the genetic variant for primary lens luxation has also been demonstrated in other breeds. Genetic screening is recommended for the following breeds2,3 and presence of the mutation could be significant in breeds not listed.
Contact us if you have diagnosed lens subluxation in a breed not listed below.
On average, age of onset is between 3 and 8 years.
Testing statistics collected in popular breeds, courtesy of the Orthopedic Foundation for Animals (OFA). View statistics in other at-risk breeds collected by the OFA.
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Prior to full lens luxation, an ophthalmologist may be able to detect lens subluxation or “wobble” of lens as the zonular fibers begin to breakdown. An “aphakic crescent” is the hallmark sign of lens subluxation. Dogs with Primary Lens Luxation typically present with acute lens subluxation of one eye, but are at risk to be affected bilaterally later in life.
Early intervention with glaucoma medications or surgical intervention prior to full luxation may be indicated to decrease the chance of surgical complications.
Anterior Displacement: Displacement of the lens into the anterior chamber of the eye is typically quite painful and can result in increased intraocular pressure and glaucoma if not treated quickly. Warning owners of signs to watch for and having a plan for immediate medical treatment may increase chances of a successful treatment and positive outcome.
Posterior Displacement: Displacement of the lens posteriorly into the vitreous is less likely to result in acute pain and inflammation. Surgical treatment may be contraindicated due to the level of difficulty of the procedure and higher risk for complications.
A G to A transition in the ADAMTS17 gene was significantly associated with Primary Lens Luxation in three different breeds, Miniature Bull Terriers, Jack Russell Terriers and Lancashire Heelers.
Mode of inheritance: Primary lens luxation has been shown to be a recessive trait, however, heterozygotes (carriers) do appear to have a slightly increased risk which could be due to haploinsufficiency.
Haploinsufficiency listen (HA-ploh-IN-suh-FIH-shen-see)When the total level of a gene product (protein) is about half of the normal level, which is not enough for normal function.
About the ADAMTS17 Gene:
The ADAMTS17 gene encodes for a protein of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein family. A mutation in this gene was shown to correlate with ocular disorders and short stature in humans5:
Not all cases of lens subluxation are due to genetics. Lens subluxation may also be secondary due to the following conditions:
- Injury or trauma
- Glaucoma
- Intraocular tumors
- Anterior uveitis
- Collagen disorders
- Idiopathic
Science and Genetics
A G to A transition in the ADAMTS17 gene was significantly associated with Primary Lens Luxation in three different breeds, Miniature Bull Terriers, Jack Russell Terriers and Lancashire Heelers.
Mode of inheritance
When the total level of a gene product (protein) is about half of the normal level, which is not enough for normal function.
About the ADAMTS17 Gene
The ADAMTS17 gene encodes for a protein of the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) protein family. A mutation in this gene was shown to correlate with ocular disorders and short stature in humans5:
Potential Test Outcomes
| Genotype | Phenotype |
|---|---|
| No variant detected | No increased risk based on the variant tested |
| CARRIER: 1 copy of the risk allele in the ADAMTS17 gene |
Slightly increased risk for lens luxation |
| AFFECTED: 2 copies of the risk allele in the ADAMTS17 gene |
Increased risk for lens luxation |
References
- Farias FH, Johnson GS, Taylor JF, Giuliano E, Katz ML, Sanders DN, Schnabel RD, McKay SD, Khan S, Gharahkhani P, et al. (2010). An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Invest Ophthalmol Vis Sci. 51(9):4716-21. DOI
- Orthopedic Foundation for Animals. (2018, July 15). Primary Lens Luxation. Retrieved from: https://www.ofa.org/diseases/dna-tested-diseases/primary-lens-luxation
- WSAVA Hereditary Disease Committee. (2018, April). Canine and Feline Hereditary Disease (DNA) Testing Laboratories. Retrieved from: https://www.vet.upenn.edu/research/academic-departments/clinical-sciences-advanced-medicine/research-labs-centers/penngen/tests-worldwide
- Mellersh CS. The genetics of eye disorders in the dog. Canine Genet Epidemiol. 2014;1(1):3. doi:10.1186/2052-6687-1-3
- Morales, J., Al-Sharif, L., Khalil, D.S., Shinwari, J. M. A., Bavi, P., Al-Mahrouqi, R. A., Al-Rajhi, A., Alkuraya, F. S., Meyer, B. F., Al Tassan, N. (2009) Homozygous mutations in ADAMTS10 and ADAMTS17 cause lenticular myopia, ectopia lentis, glaucoma, spherophakia, and short stature. J. Hum. Genet. 85: 558-568, PubMed 19836009