Lens Luxation

The lens is a structure inside the eye (behind the iris) responsible for accommodation and focused vision. It is suspended in the eye by thousands of elastic bands or tethers called zonules. If these zonules are damaged or break down prematurely the lens is allowed to move forward or backward inside the eye which is referred to as luxation. Anterior luxation refers to the forward movement of the lens (in front of the iris) whereas Posterior luxation indicates that the lens has moved backwards.

Lens luxation can be primary or secondary. Primary lens luxation is inherited in several breeds of dogs. These breeds include but are not limited to: terrier breeds, Shar Peis, Australian Cattle dogs, Border Collies, and Brittany Spaniels. These breeds experience premature degeneration of the zonules which causes lens luxation typically between 3-6 years of age. Both eyes will be affected by lens luxation; however they are rarely affected at the same time.

Secondary lens luxation occurs due to a process inside the eye that damages the zonules. Examples of these processes would be chronic inflammation, glaucoma, cataracts, trauma, and neoplasia.

Symptoms

Outward signs of a lens luxation may include:

  • Redness in the white part of the eye (bloodshot eye)
  • Excessive tearing
  • Squinting or holding the eye shut
  • Becoming head shy when the eye is approached
  • A cloudiness or haziness to the cornea
  • Vision loss

Diagnosis

A complete ophthalmic exam is necessary for the diagnosis of lens luxations. The ophthalmologist will use a slit lamp biomicroscope to examine the front and back of both eyes. A tonometer will be used to measure the pressure inside the eye. A corneal stain will help to evaluate the health of the cornea and tear film. The ophthalmologist will also assess the presence or potential for vision in the eyes.

Treatment

Early detection of lens luxation is imperative. As the lens shifts inside the eye, it will often block normal fluid flow inside the eye leading to greatly elevated intraocular pressure. The elevated pressure is both blinding and painful. With early detection of an anterior lens luxation, the lens can be removed surgically allowing the pressure to normalize. This in turn stops damage to the optic nerve and retina thus preserving vision.

Medical management alone is often unsuccessful at controlling elevated intraocular pressure long-term in the face of an anterior lens luxation. Thus, surgical intervention is the gold standard in treating anterior lens luxations. Without lens removal, eyes will often become irreversibly blind due to glaucoma which necessitates eye removal or a prosthetic eye.

Medication may be prescribed for long-term management of a posterior lens luxation to prevent the lens from coming forward.

Prognosis

As with any surgery, complications can occur with lens removal. Glaucoma and retinal detachments are the most frequent complications encountered. As the anatomy of the eye has drastically changed prior to surgery, this particular surgery carries a 60% success rate of maintaining a visual and comfortable eye.

Once the lens is removed, your pet will be farsighted. Up close vision will be functional albeit slightly blurred (much like humans requiring glasses to read a menu). The farsightedness does not affect the quality of life in our companion animals.