Lens prolapse, or luxation, is when the lens of the eye becomes dislocated from its proper position.
• A dislocated lens can move into the front (anterior) or the rear (posterior) of the eye, and may be primary (inherited) or secondary (occurring due to another condition)
• Lens luxation can block drainage of the eye's fluid and quickly lead to painful glaucoma or retinal detachment
• Surgical removal of the lens is often the best option, but management strategies may be effective in some cases
• Causes include uveitis, genetics, age, viruses, glaucoma, parasites, injury, exposure to irritants/toxins, and cancer
• Diagnosis is by ophthalmologic exam
• Good prognosis depends on early detection
• Surgical removal of the eye is a common result if other treatments do not work to control pain and/or preserve vision
Signs of lens dislocation in cats may be subtle. Cats may shake their heads or paw at their eyes. Symptoms vary in severity with time. Late stage symptoms are more severe and pronounced than early symptoms.
Lens luxation may be categorized according to where the luxation is occurring (posterior or anterior) and whether it is primary (present from birth) or secondary to another existing condition.
While uncommon in cats, lens dislocation warrants prompt medical attention. This is a painful condition that can cause blindness without timely detection and treatment. With early intervention vision may be spared. Referral to a veterinary ophthalmologist as quickly as possible is recommended for the best outcome.
Glaucoma may develop secondary to lens luxation and lead to additional symptoms:
• Light sensitivity (photophobia)
• Enlargement of the eye (buphthalmos)
• Pupil constriction
• Uneven pupils
Vision loss is usually apparent only when both eyes are affected and primarily manifests in unfamiliar surroundings:
• Bumping into things
• Reluctance to move
Uveitis, or inflammation of iris, can lead to a dislocated lens. Potential causes of uveitis include:
• Feline infectious peritonitis (FIP)
• Feline herpesvirus
• Feline immunodeficiency virus
• Eye injury
• Exposure to toxins
• Eye irritants
• Other viral infections
• Congenital anomalies
• Senescence (age-related degeneration)
Symptoms are usually sudden in onset and include:
• Tearing (epiphora)
• Redness of the eye and surrounding tissue
• Swelling of the eye (buphthalmia)
• Blue haze or cloudiness of the eye
• Iris trembling (iridodonesis)
• Lens trembling (phacodonesis)
• Abnormally positioned clear part of the lens
Diagnosis is usually made by a primary care veterinarian after thorough physical exam and ophthalmic exam including:
• Fluorescein stain of the cornea
• Intraocular pressure measurement (tonometry)
• Schirmer tear test
Referral to a veterinary ophthalmologist may be recommended. If lens luxation is found to be a secondary condition to existing glaucoma, urgent treatment is required. Glaucoma is very painful and can result in loss of vision or the entire eye.
Treatment depends on the type of luxation, and emergency therapy for glaucoma (if present) is the priority.
Anterior lens luxations are treated with:
• Surgical removal of the lens
• Surgical removal of the eye
• Treatment for underlying conditions like glaucoma and/or uveitis
The best way to manage a posterior lens luxation is controversial. Medications may provide better retention of vision than surgery in some cases, especially when uveitis is the underlying cause.
Treatment may not be necessary or is targeted at the underlying cause.
Dislocation of a lens is irreversible, often leading to glaucoma, which affects cats long-term. With lens removal surgery, glaucoma can sometimes be managed with medication only, but often the eye must be removed to achieve permanent resolution of pain. Prognosis after eye removal is good.
If the underlying cause of lens dislocation is cancer, prognosis depends on staging and treatment of the tumor.
There is no specific prevention for lens dislocation. The condition itself is not contagious to other cats, but some underlying causes are (viruses such as FIV, FeLV, FIP; parasites such as T. gondii). Some of these infections can be prevented by vaccination, keeping cats indoors, and regular veterinary care. In congenital cases, prevention is not possible.
Lens dislocation is rare in cats.
• Benign neglect
• Anti-inflammatory medications
• Lens removal surgery
• Eye removal surgery
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