Deutsch
Hrvatski
Русский
Português
is a painful inherited eye disorder in which the crystalline lens becomes displaced from its normal position. It can cause inflammation, glaucoma, permanent vision loss and blindness.
The condition is especially important in many terrier breeds, including Jack Russell Terriers, Parson Russell Terriers, Miniature Bull Terriers and several other breeds with a documented genetic predisposition.
PLL occurs when the delicate fibres supporting the lens progressively weaken or rupture. As the lens loses its normal support, it may move partially or completely out of position.
Clinical signs usually appear in adulthood, commonly between three and eight years of age. A young dog may therefore appear healthy while carrying a genetic variant associated with an increased risk of developing the disease later in life.
The most widely tested form of inherited PLL in terriers is associated with a mutation in the ADAMTS17 gene (c.1473+1G>A).
DNA testing can identify dogs that are genetically clear, heterozygous carriers or homozygous for this mutation, providing important information for breeding decisions and ophthalmological monitoring.
The crystalline lens is a transparent structure located behind the iris. Its primary function is to focus light onto the retina.
The lens is held in position by thin connective-tissue fibres called zonules or suspensory ligaments.
In dogs affected by primary lens luxation, these supporting fibres become structurally unstable and progressively deteriorate.
Eventually, the lens may become partially displaced (subluxation) or completely displaced (luxation).
| Condition | Description | Clinical significance |
|---|---|---|
| Normal lens | Lens remains correctly positioned behind the iris | Normal anatomical support |
| Lens subluxation | Lens becomes partially displaced | Early or progressive lens instability |
| Anterior lens luxation | Lens moves forward into the anterior chamber | High risk of glaucoma and acute ocular complications |
| Posterior lens luxation | Lens moves backward into the vitreous cavity | May cause visual impairment and secondary complications |
Anterior lens luxation is especially dangerous because the displaced lens may interfere with normal intraocular fluid circulation and drainage.
This can cause a rapid increase in intraocular pressure, resulting in secondary glaucoma, severe pain and irreversible damage to the eye.
Suspected anterior lens luxation is a veterinary ophthalmological emergency requiring immediate assessment.
The gene associated with the common inherited form of primary lens luxation in many terrier breeds is ADAMTS17 – ADAM Metallopeptidase with Thrombospondin Type 1 Motif 17.
ADAMTS17 encodes an extracellular protein involved in connective-tissue organization and the normal development and maintenance of tissues supporting the crystalline lens.
Mutations affecting ADAMTS17 can disrupt these structural functions and contribute to degeneration of the zonular fibres.
| Genetic characteristic | Description |
|---|---|
| Gene | ADAMTS17 |
| Full gene name | ADAM Metallopeptidase with Thrombospondin Type 1 Motif 17 |
| Main associated condition | Primary Lens Luxation (PLL) |
| Chromosome | Canine chromosome 3 |
| Molecular role | Extracellular tissue organization and structural support |
| Main consequence of the PLL-associated mutation | Abnormal RNA processing and truncated protein |
| Inheritance | Predominantly autosomal recessive, with a low clinical risk in carriers |
The association between ADAMTS17 and canine PLL was established through genetic research involving Jack Russell Terriers, Miniature Bull Terriers and Lancashire Heelers.
The findings provided the foundation for DNA testing that identifies the disease-associated mutation before clinical symptoms appear.
The commonly tested PLL-associated mutation is:
ADAMTS17 c.1473+1G>A
This mutation occurs at a splice-donor site at the beginning of intron 10.
Normal RNA splicing removes introns and joins coding exons to generate a functional messenger RNA.
The c.1473+1G>A substitution disrupts this process and causes exon 10 skipping, resulting in a frameshift and a prematurely truncated protein.
| Feature | Description |
|---|---|
| Mutation | c.1473+1G>A |
| Gene | ADAMTS17 |
| Mutation type | Single-nucleotide substitution |
| Location | Splice-donor site of intron 10 |
| DNA change | Guanine (G) to adenine (A) |
| RNA consequence | Exon 10 skipping |
| Protein consequence | Frameshift and premature truncation |
| Associated disorder | Primary Lens Luxation |
The original study by Farias and colleagues (2010) demonstrated that the mutation was strongly associated with clinical PLL in three different dog breeds.
Subsequent research by Gould and colleagues (2011) identified the same mutation in PLL-affected dogs from 14 additional breeds.
However, not all dogs with primary lens luxation carry this mutation.
This indicates that genetically distinct forms of PLL also exist.
Consequently, a negative result for ADAMTS17 c.1473+1G>A does not exclude every possible inherited or acquired cause of lens luxation.
Primary lens luxation is particularly associated with terriers and several other susceptible breeds.
The ADAMTS17 mutation has been documented in multiple breeds, and testing is relevant where this specific variant has been established.
| Breed | Relevance |
|---|---|
| Jack Russell Terrier | One of the breeds involved in the original genetic discovery |
| Parson Russell Terrier | Documented ADAMTS17-associated PLL |
| Miniature Bull Terrier | Well-established genetic association |
| Yorkshire Terrier | Documented ADAMTS17 mutation |
| Welsh Terrier | Documented ADAMTS17 mutation |
| Sealyham Terrier | Documented ADAMTS17 mutation |
| Wire Fox Terrier | Documented ADAMTS17 mutation |
| Jagdterrier / German Hunting Terrier | Documented ADAMTS17 mutation |
| Rat Terrier | Documented ADAMTS17 mutation |
| Toy Fox Terrier | Documented ADAMTS17 mutation |
| Patterdale Terrier | Documented ADAMTS17 mutation |
| Tenterfield Terrier | Documented ADAMTS17 mutation |
| Lakeland Terrier | Included in recognized PLL testing programmes |
| Breed | Relevance |
|---|---|
| Lancashire Heeler | One of the original research breeds |
| Chinese Crested Dog | Documented susceptibility |
| Australian Cattle Dog | Included in ADAMTS17 PLL testing |
| Danish-Swedish Farmdog | Included in ADAMTS17 PLL testing |
| Tibetan Terrier | Documented ADAMTS17-associated PLL |
| Volpino Italiano | Documented ADAMTS17-associated PLL |
The presence and frequency of the mutation may differ substantially between breeds.
Furthermore, some breeds affected by primary lens luxation have genetically distinct forms that are not detected by this particular ADAMTS17 test.
Breed-specific recommendations should therefore be considered when interpreting results.
The frequency of the PLL-associated ADAMTS17 mutation varies between breeds and populations.
In research involving Miniature Bull Terriers, estimated mutant allele frequencies ranged from approximately 27% to 39% in the investigated populations.
These frequencies demonstrate that the mutation can be relatively common in certain breeding populations.
| Population measurement | Reported finding |
|---|---|
| Breed | Miniature Bull Terrier |
| Estimated mutant allele frequency | Approximately 27–39% |
| Expected homozygous genotype frequency | Approximately 7.3–15.2% |
| Main interpretation | A substantial frequency of the mutation in the populations investigated |
These figures should not be treated as universal worldwide frequencies.
They also should not be interpreted as the proportion of dogs that will necessarily develop clinically apparent PLL.
Genetic frequency, disease penetrance, age of onset and population sampling all influence the interpretation of such estimates.
ADAMTS17-associated PLL is predominantly inherited as an autosomal recessive condition.
Dogs with two copies of the disease-associated variant have the highest genetic risk.
However, the inheritance pattern has an important additional characteristic: some dogs carrying only one copy of the mutation may also develop PLL.
Research has identified a low but measurable clinical risk in heterozygous carriers.
| DNA result | Genetic status | Clinical interpretation | Transmission to offspring |
|---|---|---|---|
| N/N | Clear | No increased PLL risk attributable to the tested mutation | Does not transmit the mutation |
| N/PLL | Carrier / Low Risk | Low but non-zero risk of clinical PLL | Approximately 50% probability of transmitting the mutation |
| PLL/PLL | High Risk | Substantially increased risk of developing PLL | Transmits the mutation to all offspring |
An N/N dog has two normal copies at the tested ADAMTS17 position.
It cannot transmit the c.1473+1G>A mutation to its offspring.
However, this result does not exclude unrelated eye diseases or other genetic causes of lens luxation.
A heterozygous dog has one normal copy and one mutated copy.
Most carriers remain clinically unaffected.
However, the Orthopedic Foundation for Animals describes an approximate 5–10% risk of developing PLL in carriers.
This estimate should not be assumed to apply identically to every breed or population.
Carriers can transmit the mutation to approximately half of their offspring.
A dog with two copies of the mutation has a substantially increased genetic risk of developing primary lens luxation.
Clinical symptoms may appear years after the DNA test is performed.
A PLL/PLL result does not necessarily mean that the dog already has a displaced lens or impaired vision.
Nevertheless, appropriate veterinary ophthalmological monitoring is particularly important.
Clinical symptoms most commonly appear between three and eight years of age.
The disease frequently affects both eyes, although the onset may not occur simultaneously.
Early signs can be subtle and may be mistaken for less serious eye conditions.
| Early signs | Advanced signs |
|---|---|
| Increased tearing | Severe ocular pain |
| Eye redness | Marked corneal cloudiness |
| Squinting or blinking | Secondary glaucoma |
| Sensitivity to light | Sudden vision deterioration |
| Mild ocular discomfort | Complete lens displacement |
| Changes in pupil appearance | Irreversible vision loss |
| Eye rubbing | Blindness |
The appearance of a red, painful or cloudy eye should never be ignored in a breed predisposed to PLL.
| Characteristic | Anterior luxation | Posterior luxation |
|---|---|---|
| Lens position | In front of its normal position | Behind its normal position |
| Main concern | Acute glaucoma and ocular damage | Visual impairment and secondary complications |
| Eye pain | May be severe | Variable |
| Vision loss | May occur rapidly | Variable |
| Clinical urgency | Ophthalmological emergency | Requires prompt veterinary assessment |
| Treatment | Often requires urgent intervention | Depends on lens position and complications |
Anterior lens luxation may rapidly compromise vision.
Immediate veterinary care is essential when acute lens displacement is suspected.
Diagnosis involves distinguishing the dog's genetic status from its current clinical eye condition.
A DNA test identifies whether the dog carries the tested ADAMTS17 mutation.
Clinical examination establishes whether lens instability or luxation is actually present.
| Diagnostic method | Purpose |
|---|---|
| ADAMTS17 DNA test | Determines genetic status for the tested mutation |
| Slit-lamp biomicroscopy | Assesses lens position and zonular stability |
| Tonometry | Measures intraocular pressure |
| Complete ophthalmological examination | Evaluates ocular structures and complications |
| Ocular ultrasonography | Assesses internal structures when direct visualization is limited |
| Clinical history | Helps distinguish primary from secondary lens luxation |
Genetic testing for the ADAMTS17 mutation associated with Primary Lens Luxation (PLL) is available at AnimaLabs.
Importantly, secondary lens luxation can develop as a consequence of other eye diseases or injuries.
| Primary lens luxation | Secondary lens luxation |
|---|---|
| Often associated with inherited zonular abnormalities | Develops as a consequence of another condition |
| May be associated with ADAMTS17 mutations | May occur without inherited PLL |
| Often develops during adulthood | Can occur at different ages |
| Frequently affects both eyes over time | May be unilateral or bilateral |
| DNA testing can help establish genetic susceptibility | Diagnosis focuses on the underlying ocular disorder |
Possible secondary causes include glaucoma, chronic uveitis, advanced cataracts and ocular trauma.
A genetically clear result does not eliminate these possibilities.
There is currently no treatment that corrects the underlying inherited ADAMTS17 mutation.
Management depends on the location of the lens, severity of ocular complications, visual potential and the dog's overall condition.
| Treatment | Purpose | Important considerations |
|---|---|---|
| Surgical lens removal | Removes a displaced lens | May preserve vision in selected cases |
| Intraocular pressure medication | Helps manage glaucoma | Does not correct the genetic defect |
| Anti-inflammatory medication | Controls selected inflammatory complications | Requires veterinary supervision |
| Ophthalmological monitoring | Detects progressive ocular changes | Particularly important in high-risk dogs |
| Surgery for a blind, painful eye | Provides lasting pain relief | Considered when vision cannot be restored |
Surgery may be recommended for certain cases of lens luxation, particularly when anterior displacement threatens vision.
However, complications may include postoperative inflammation, glaucoma and retinal abnormalities.
Treatment decisions should always be made by a veterinary ophthalmologist.
The prognosis depends strongly on the stage of disease and the speed of appropriate treatment.
Early identification of lens instability may allow closer monitoring and intervention before severe complications occur.
| Clinical situation | General prognosis |
|---|---|
| Genetically high-risk dog without clinical symptoms | Normal vision may be maintained; monitoring is recommended |
| Early lens subluxation | Opportunities for intervention depend on individual findings |
| Recent lens luxation without severe complications | Vision may be preserved in selected cases |
| Luxation complicated by glaucoma | More guarded prognosis |
| Severe, irreversible ocular damage | Vision may not be recoverable |
The most important clinical distinction is between genetic susceptibility and established structural damage.
DNA testing can identify inherited risk, but it cannot establish how much damage has already occurred.
One of the most important applications of PLL DNA testing is the identification of breeding combinations that could produce puppies with two copies of the mutation.
Because clinical PLL often develops after breeding age, the absence of visible symptoms is insufficient for evaluating genetic risk.
| Parental combination | Clear (N/N) | Carrier (N/PLL) | High Risk (PLL/PLL) |
|---|---|---|---|
| N/N × N/N | 100% | 0% | 0% |
| N/N × N/PLL | 50% | 50% | 0% |
| N/PLL × N/PLL | 25% | 50% | 25% |
| N/N × PLL/PLL | 0% | 100% | 0% |
| N/PLL × PLL/PLL | 0% | 50% | 50% |
| PLL/PLL × PLL/PLL | 0% | 0% | 100% |
These percentages represent expected probabilities for each puppy and do not guarantee exact proportions within an individual litter.
| Breeding combination | Genetic interpretation | General recommendation |
|---|---|---|
| N/N × N/N | No puppies inherit the tested mutation | Suitable with respect to this variant |
| N/N × N/PLL | No homozygous high-risk puppies expected | May be considered with careful carrier management |
| N/PLL × N/PLL | 25% high-risk genotype expected | Avoid |
| N/N × PLL/PLL | All puppies inherit one mutated copy | Generally discouraged; requires careful welfare assessment |
| N/PLL × PLL/PLL | 50% high-risk genotype expected | Avoid |
| PLL/PLL × PLL/PLL | All puppies inherit two mutated copies | Avoid |
Importantly, preventing PLL/PLL offspring does not eliminate every possible clinical risk because some heterozygous carriers may also develop the condition.
Breeding decisions must therefore consider both genotype and the welfare of individual animals.
Automatically excluding every carrier of a recessive disease-associated mutation may reduce genetic diversity, particularly when the variant is common in a breed.
Severely narrowing the breeding population can increase inbreeding and potentially increase the frequency of other inherited disorders.
For this reason, some breeding programmes may consider carefully selected, clinically healthy carriers paired exclusively with genetically clear animals.
This strategy prevents offspring from inheriting two copies of the tested mutation while allowing gradual reduction of the variant across generations.
However, PLL requires particular caution because carriers themselves have a low but documented clinical risk.
| Strategy | Potential benefit | Limitation |
|---|---|---|
| DNA testing breeding animals | Identifies mutation carriers | Only evaluates the tested genetic variant |
| Carrier-to-clear mating | Prevents PLL/PLL offspring | Carrier offspring retain some clinical risk |
| Testing future breeding candidates | Supports informed selection | Requires consistent genetic records |
| Routine ophthalmological examinations | Identifies ocular changes | Cannot replace genetic testing |
| Preserving genetic diversity | Reduces excessive loss of breeding lines | Other inherited diseases must also be considered |
The objective should be a sustainable reduction of PLL-associated risk without unnecessarily compromising the overall genetic health of the breed.
No.
A clear genetic result means that the dog does not carry the specific ADAMTS17 c.1473+1G>A variant examined by the test.
It does not exclude every possible inherited or acquired ocular disorder.
| Condition | Excluded by a clear ADAMTS17 PLL result? |
|---|---|
| The tested ADAMTS17 PLL mutation | Yes |
| Other genetic forms of PLL | No |
| Secondary lens luxation | No |
| Glaucoma from other causes | No |
| Cataracts | No |
| Retinal diseases | No |
| Ocular trauma | No |
Different genetic mechanisms can cause similar clinical conditions.
A clear result should therefore be interpreted as a specific molecular finding rather than a comprehensive eye-health certificate.
Primary lens luxation is a particularly important inherited disorder because it can cause severe ocular pain and permanent blindness.
The relatively late onset means that an apparently healthy young dog may carry a high-risk genotype.
DNA testing can identify the genetic status of breeding animals before offspring are produced.
| Benefit | Importance |
|---|---|
| Identification of clear dogs | Establishes absence of the tested mutation |
| Detection of carriers | Helps identify mutation transmission risk |
| Recognition of high-risk genotypes | Supports veterinary monitoring and breeding decisions |
| Predictable inheritance | Allows calculation of offspring genotype probabilities |
| Prevention of high-risk combinations | Reduces the likelihood of producing PLL/PLL puppies |
| Population genetic management | Supports long-term reduction of mutation frequency |
Responsible breeding requires consideration of the individual dog's genotype, clinical eye health, family history and overall genetic diversity.
Primary lens luxation is an inherited eye disorder in which degeneration of the zonular fibres causes the crystalline lens to move from its normal anatomical position.
It can cause inflammation, glaucoma, severe pain and blindness.
The most widely tested form of PLL in terriers is associated with the ADAMTS17 gene, specifically the c.1473+1G>A mutation.
Jack Russell Terriers are among the breeds in which ADAMTS17-associated PLL has been documented. However, the frequency of the mutation varies between populations and breeding lines.
A clear dog has no copies of the tested ADAMTS17 mutation and cannot transmit this specific mutation to its offspring.
A carrier has one copy of the mutation and can transmit it to approximately 50% of offspring.
Most carriers do not develop PLL, but a small clinical risk remains.
Yes. Heterozygous carriers have a low but documented risk of developing clinical PLL.
The Orthopedic Foundation for Animals describes an approximate risk of 5–10%.
It means that the dog carries two copies of the tested PLL mutation and has a substantially increased risk of developing clinical disease.
It does not necessarily indicate that the dog already has symptoms.
Carrier-to-carrier mating is expected to produce approximately 25% offspring with two copies of the PLL mutation. Such matings should be avoided.
A carrier-to-clear mating produces no offspring homozygous for the tested mutation, but approximately half are expected to be carriers.
Such combinations may be considered in carefully managed breeding programmes, taking into account clinical eye health and genetic diversity.
Clinical symptoms commonly appear between three and eight years of age, although individual cases vary.
Yes. Lens displacement can cause significant ocular pain, particularly when accompanied by inflammation or secondary glaucoma.
Yes. Untreated lens luxation, especially anterior luxation complicated by glaucoma, can result in irreversible blindness.
The underlying genetic defect cannot currently be corrected.
However, prompt ophthalmological treatment, including surgery in suitable cases, may preserve vision or relieve pain.
No. DNA testing determines genetic status for a particular mutation, while an ophthalmological examination evaluates the current health and condition of the eyes.
Farias FHG, Johnson GS, Taylor JF, et al. An ADAMTS17 splice donor site mutation in dogs with primary lens luxation. Investigative Ophthalmology & Visual Science. 2010;51(9):4716–4721. DOI: 10.1167/iovs.09-5142.
Gould D, Pettitt L, McLaughlin B, et al. ADAMTS17 mutation associated with primary lens luxation is widespread among breeds. Veterinary Ophthalmology. 2011;14(6):378–384. DOI: 10.1111/j.1463-5224.2011.00892.x.
Mellersh CS. The genetics of eye disorders in the dog. Canine Genetics and Epidemiology. 2014;1:3. DOI: 10.1186/2052-6687-1-3.
University of California, Davis – Veterinary Genetics Laboratory. Primary Lens Luxation (PLL). Genetic testing, inheritance and interpretation of results.
Orthopedic Foundation for Animals. Primary Lens Luxation. Interpretation of normal, carrier and high-risk genotypes.
Online Mendelian Inheritance in Animals (OMIA). Lens Luxation in Dogs. Genetic variant and breed information.
The PLL DNA test identifies whether a dog carries the specific ADAMTS17 c.1473+1G>A mutation.
A clear result does not exclude all causes of lens luxation or other inherited eye disorders.
Heterozygous carriers generally have a low but documented clinical risk, while dogs homozygous for the mutation have a substantially increased risk of developing PLL.
Genetic status does not establish the current condition of the lens or predict the exact age at which clinical signs may develop.
DNA testing does not replace veterinary ophthalmological examination, diagnosis or treatment.
Breeding decisions should consider genotype, clinical eye health, breed-specific recommendations and genetic diversity.