NORMAL VISION AND VISION WITH A DISLOCATED LENS:
The lens of the eye is an important structure for vision. In order to have normal vision, the lens must be optically clear (free of cloudy or opaque spots) and the lens must remain in the normal position. If the lens moves out of its normal position, light rays are not focused on the retina and the eye becomes either far-sighted or near-sighted (depending upon the direction of lens movement). More importantly, dislocation (luxation) of the lens typically leads to devastating (and with time, blinding) complications in the eye. These include inflammation (uveitis), glaucoma, and retinal detachment. These complications can be quite painful. Glaucoma is increased pressure within the eye. It causes rapid and irreversible vision loss if not treated quickly and appropriately, by damaging both the retina and optic nerve of the eye.
WHY DOES A LENS DISLOCATE?
The main causes for lens luxation are genetics and chronic inflammation within the eye (uveitis). Inherited dislocation of the lens notoriously affects certain breeds. The most common breeds to be affected are the terriers, especially the Jack Russell Terriers and the Fox Terriers. Other commonly affected breeds are Poodles, Beagles, Blue Heelers, and Shar Peis but any breed or mixed breed can be affected. Cats occasionally develop the same condition. In cats, lens dislocation is usually an age-associated degenerative change or it develops due to chronic uveitis. Cataracts can also lead to dislocation of the lens in either species. The disease usually affects both eyes. Therefore, both eyes will receive a thorough eye examination
ANATOMY OF THE NORMAL LENS POSITION:
In order to understand how the lens dislocates, one must first understand a little bit about the anatomy of the eye. The lens is normally held in place by numerous small fibers called lens zonules. The inherited condition of zonular weakness or the damaging effects of intraocular inflammation on these zonules will ultimately lead to rupture of lens zonules. When these hair-like fibers have all broken free, the lens can move freely within the eye. This is the point at which the complications such as glaucoma and uveitis typically develop.
OUTCOME OF LENS LUXATION:
If a lens is dislocated, the eye is at high risk for vision loss. The lens movement affects the nutrition to the lens thus a cataract can develop. Glaucoma is a frequent manifestation of lens luxation (or subluxation) and it can develop rapidly. The short-term incidence of glaucoma in dogs is 65% or greater. This type of glaucoma does not necessarily respond to medical therapy.
TREATMENT OF THIS CONDITION:
Medical therapy can temporarily alleviate some of the discomfort in some cases. It will not correct the problem, however. The ideal therapy, at least for anteriorly luxated lenses, is surgical extraction of the lens (assuming that there has not yet been permanent damage to the eye that would prohibit vision after surgery). If the condition has been chronic and/or has already caused permanent blindness, your pet may be a better candidate for a procedure directed at comfort such as placement of a prosthesis or complete eye removal.
Time is of the essence when dealing with a subluxated or luxated lens. The difference between these terms is only a matter of the severity of the stage of disease. Either situation can cause pressure elevations within the eye. These are SERIOUS glaucoma attacks that can lead to complete and permanent blindness within several days or less. This is an emergency situation!
The goals of surgical removal of the lens are to maintain vision and to eliminate ocular pain. Even with surgery, the prognosis is guarded. However, for an anteriorly-luxated lens, the prognosis with surgery is 75-80% versus about 0% long-term without surgery. If vision loss occurs despite surgery, it is usually due to persistent glaucoma or retinal detachment.
Prior to making a final recommendation for surgery, your pet’s general health needs to be evaluated. Preoperative blood tests are likely to be recommended. Retinal testing, consisting of ocular ultrasound and/or electroretinography, may be recommended to make sure that your pet is a candidate for lens removal surgery.
Once your pet has been evaluated, you will be given a price estimate for the surgery.
WHAT IS INCLUDED IN THE PRICE OF SURGERY:
Anesthetic monitoring (including pulse oximetry, ECG, and CO2 monitoring)
The surgery itself
Medications dispensed on surgery day
Two postoperative examinations
WHAT IS NOT INCLUDED IN THE PRICE OF SURGERY:
Retinal evaluation-if necessary
Recheck examinations after the second postoperative exam
Refills of medications after surgery day
WHAT TO EXPECT AFTER SURGERY:
Vision may be acutely worse after surgery, due to the inflammation associated with surgery as well as the sudden change in refractive error due to loss of the lens. It would be like somebody suddenly changing your glasses or contact lens prescription while you are still stuck with the old pair. The animals seem to partially adapt to their postoperative far-sightedness, especially over the few months following surgery. When your pet goes home, vision may be fuzzy. It should improve as the inflammation decreases and with time. Try to be patient. Unless there is a complication, vision should return.
This surgery is not a "quick fix". The postoperative care is critical and is vital to a successful outcome of surgery. Medical therapy is usually the most intense and time-consuming during the first 1-2 weeks after surgery. Medical therapy will continue for at least 3 months after surgery, usually at a gradually decreasing level. Some patients require long-term medical therapy. In these cases, it is usually due to ongoing pressure problems.
Since there are potential complications (primarily glaucoma or retinal detachment), long-term monitoring will be required. For this reason, multiple rechecks will be needed especially during the first 3-4 months after surgery and usually 1-2 times per year for the rest of the pet’s life. At these visits, potential complications can be addressed and the medical plan can be tailored to your pet’s progress.
The eye should be considered fragile after surgery. All precautions should be taken so that your pet does not damage the eye(s). The protective Elizabethan collar should be worn by your pet for 3 weeks or until directed otherwise by the doctor. Be aware that the E-collar can decrease both vision and hearing during its period of use.
You need to be really committed to these efforts at saving your pet’s eyesight and prepared for the follow-up care and treatments that will be inevitable, even with a perfect surgery.
The main complications for which we will monitor after surgery are glaucoma, retinal detachment, or severe inflammation. If your pet is in the unfortunate percentage of animals that develop these problems despite surgery, they are oftentimes manageable so long as the doctor has the opportunity to treat them promptly. Please call us with any concerns after surgery. We really care about our patients and don’t want you to worry.