Lens Luxation
Lens luxation occurs when the zonular fibers (suspensory ligaments) that hold the lens in place break down, allowing the lens to displace from its normal position. Anterior luxation (into the front chamber) is an emergency due to acute glaucoma risk. Posterior luxation (into the vitreous) is less immediately dangerous but still requires management.
Symptoms & Signs
- Sudden eye pain and redness (anterior luxation)
- Visible lens in front chamber
- Cloudy cornea
- Irregular pupil shape
- Sudden vision loss
- Squinting
- Tearing
Causes & Risk Factors
Primary: inherited weakness of zonular fibers (terrier breeds - Jack Russell, Fox Terrier, Shar Pei). ADAMTS17 gene mutation identified. Secondary: chronic glaucoma, uveitis, trauma, intraocular tumors, or cataracts causing lens swelling.
Diagnosis
Slit-lamp biomicroscopy showing displaced lens. Tonometry for intraocular pressure. Gonioscopy of fellow eye. Ultrasound if lens not visible. DNA testing for ADAMTS17 mutation in at-risk breeds.
Treatment
Anterior luxation: emergency surgical removal (intracapsular lens extraction). Posterior luxation: monitoring, miotics to prevent anterior movement, or surgical removal. Prophylactic treatment of fellow eye. Glaucoma management if present.
Prevention
DNA testing breeding stock for ADAMTS17 mutation. Removing carriers from breeding programs. Regular ophthalmic examination of at-risk breeds. Prophylactic miotic therapy for subluxating lenses.
Prognosis
Anterior luxation with prompt surgery: fair for vision preservation. Delayed treatment: poor (secondary glaucoma). Posterior luxation: fair with monitoring. Fellow eye: 50% risk of luxation within months.