Lens luxation in dogs

Overview

Forward or backward displacement

The transparent lens normally lies behind the iris and ahead of the vitreous. A thin surrounding capsule moves with the detached lens. The lens focuses light onto the retina. Fine zonular fibres suspend it. Failure of some fibres allows tilting or movement while attachment partly remains. This is subluxation.

A completely detached lens can pass through the pupil into the anterior chamber. Backward luxation drops it into the vitreous cavity. It can also move between these spaces.

Causes

Inherited zonular weakness

Primary luxation involves inherited weakening of suspensory fibres. One ADAMTS17 variant is associated with disease in Miniature Bull Terriers, Lancashire Heelers and Jack Russell Terriers, for example. It also occurred in affected dogs from 14 other breeds. Shar Peis have a different variant in the same gene, associated with luxation and open-angle glaucoma.

Other eye disease or trauma

Chronic glaucoma can enlarge the globe enough to stretch and break fibres. Persistent uveitis can weaken attachment. Advanced cataracts can shrink the lens and disrupt fibres. Intraocular tumours can push it aside. Impact-related luxation can accompany other serious injuries. Age-related degeneration can displace the lens without previously identified disease. Congenital luxation is rare and may accompany a smaller lens.

Risk factors

Inherited disease most often starts at three to eight years. Average onset is 4.5 years. Fibre abnormalities can appear by 20 months. Two copies of the tested variant confer greatest risk. One-copy carriers have lower risk. Carrier risk depends on breed. Variant-frequency estimates in examined Miniature Bull Terrier groups suggested affected proportions of 7.3–15.2%.

One northern European breeding record had 591 PLL-tested Jack Russell Terriers by the end of 2023. Twenty-eight were carriers. One had two risk copies. Five hundred and sixty-two were clear for the tested variant. The breeding programme recorded five luxation cases among dogs born during 2000–2023.

Typical symptoms

Partial displacement can escape notice despite excess movement. Anterior luxation often causes sudden signs.

• Red conjunctiva and eye white.
• Heavy tearing.
• Pawing at the eye.
• Increased blinking.
• Pale surface cloudiness.
• Reduced or lost vision.

The anterior lens edge can appear as a clear ring before the pupil. A posterior lens can sit too low to see through the pupil. Backward displacement may initially cause fewer signs. Inherited disease can affect eyes at different times. Intervals can be days, months or years.

Complications and consequences

Pressure, cornea and retina

An anterior lens can block the pupil and intraocular fluid circulation. Vitreous dragged forwards can also block drainage. Contact with the inner cornea can cause local swelling. Cloudiness can remain despite return to the vitreous cavity. A mobile posterior lens can injure and detach retina. Among 45 late-presenting partially or fully displaced eyes, 35 had glaucoma, or 77.8%.

Diagnosis at the vet

Position and pressure

Both eyes are examined for early fellow-eye changes. Slit-lamp examination identifies abnormal position. A crescent-shaped lens-free gap can appear between pupil and loose lens edge. The lens may tremble with movement. Forward movement can shallow the anterior chamber.

Pressure is measured for treatment-requiring elevation. Measurements over an anterior lens can be falsely high.

Vision and the back of the eye

Ultrasound assesses retina and vitreous if cloudiness blocks the view. It can also locate a posterior lens. Bright-light blinking helps assess visual potential. Fellow-pupil constriction when light enters the affected eye also assesses light perception. History helps distinguish whether glaucoma caused or followed luxation. Genetic testing identifies known breed-associated variants.

Treatment

Emergency anterior luxation care

Treatment depends on position, vision and pressure. Raised pressure is reduced before eye surgery where possible. Some strongly pupil-constricting drops can worsen fluid blockage with an anterior lens. Prompt removal is attempted when vision can be saved. A fully detached lens can be removed intact with its capsule. Removal can leave marked long-sightedness and blurred near vision. An artificial lens can correct the refractive error. Removing a permanently blind, painful eye can relieve pain.

Visual prognosis after anterior treatment

Selected cases may undergo transcorneal repositioning behind the iris. The lens remains inside and can move forwards again.

A 38-dog study repositioned 28 of 41 eyes successfully, or 68.2%. Ten of those 28 reluxated forwards within two to 120 days, or 35.7%. Vision was identified in 16 of 28 after successful reduction, or 57%. Two of the 16 retained vision for under seven days. The other 14 had median preservation of 100 days, ranging seven to 300. Glaucoma was the most common vision-loss cause.

Another study retained vision in seven of 10 surgically extracted eyes, or 70%. Repositioning preserved four of nine, or 44%. Median follow-up was 256 days after extraction and 48 after repositioning. The visual difference was not statistically significant. Anterior segment inflammation was more common after extraction.

Partial or posterior displacement

With sufficiently stable attachment, ultrasound can remove lens contents while preserving the capsule. Treating subluxation before pressure rises can improve prognosis. Posterior lenses may need drops preventing anterior movement. An earlier 34-dog study followed partially or posteriorly displaced eyes without surgery. All 34 checked at four to six weeks retained vision. All 29 checked at three months also saw. At one year, 16 of 20 medically managed eyes retained vision, or 80%. At two years, 11 of 19 did.

Posterior lens removal risks retinal detachment. A seven-year-old Italian Greyhound underwent successful removal through vitreous surgery. The operated eye retained vision at six months. No detachment was seen then.

Prevention

Regular examinations can detect instability before obvious signs. Testing associated variants guides breeding in relevant breeds. Some Chinese Crested breeding guidance recommends PLL testing alongside formal eye examination. One Lancashire Heeler programme gives eye reports 12-month validity. Confirmed or suspected luxation excludes breeding under that programme. Tests help establish whether a known variant can pass to offspring.

Important for dog owners

Tell the emergency clinic when you first noticed a change in the appearance of your dog's eye. Also mention previous eye diseases, as cataracts or glaucoma may help explain why the lens moved. Do not use human or another animal's medication without veterinary advice. Report increased redness or inflammation after prescribed drops. After surgery, eye pressure is monitored so that any increase can be treated promptly. The other eye also needs regular monitoring if your dog has inherited lens luxation.

Frequently asked questions

Is luxation the same as cataract?

In lens luxation, the lens has moved away from its normal position inside the eye. A cataract instead means that the lens itself has become cloudy. Hypermature cataracts can nevertheless weaken attachment and cause luxation. An anterior lens can block fluid circulation.

Can the other lens detach?

Inherited lens luxation often affects both eyes, but symptoms do not necessarily begin on the same day. The vet examines the other eye at the same appointment to look for possible early changes. At first, the other eye may develop only a partial displacement of the lens.

Can dogs see after lens removal?

Some dogs retain useful sight when a lens displaced into the anterior chamber is removed promptly. Without an artificial lens, your dog's vision at close range can remain blurred. Vision may deteriorate later because of conditions such as glaucoma or retinal detachment. For this reason, eye pressure continues to be monitored even after a successful operation.

Can I treat it at home with drops?

Sudden pain or cloudiness needs emergency assessment because an anterior lens can rapidly raise pressure. The vet selects eye drops according to where the lens lies and whether eye pressure is raised. Do not use another animal's drops without veterinary instructions.

Does a clear genetic test exclude luxation?

A clear result means only that the dog does not have the particular variant tested. In some breeds with inherited lens luxation, that same genetic variant has not been found. The lens can also move because of an injury or another eye disease. An eye examination establishes whether the lens is in its normal position at the time of examination.