Cataracts are opacities of the lens. The lens is a normally clear structure located behind the iris. The lens helps to focus light as it reaches the back of the eye. If the opacity in the lens is complete, it can completely obstruct vision. When less than 10% of the lens is affected it is called an incipient cataract. When 11% -99% is involved, it is termed an immature cataract, and when 100% of the lens is involved it is termed mature.
Cataracts develop secondary to diabetes as the high glucose draws water into the lens fibers, causing expansion and disruption of normal organization. Over 85% of dogs with diabetes mellitus develop cataracts. Most form acutely and progress rapidly, resulting in a swollen (intumescent) lens. Further ophthalmic examination may reveal the presence of intraocular inflammation (uveitis). This often develops secondary to the presence of the rapidly progressive cataracts. The presence of red eyes, low intraocular pressures, small pupils poorly responsive to dilation medication, and a hazy appearance within the eyes are all consistent findings for uveitis.
The treatment for cataracts is surgical removal. Unfortunately, there is no medical treatment to reverse cataracts once they have developed. Cataract surgery is not only important to restore vision, but as cataracts progress (especially in diabetic patients) they cause inflammation inside of the eyes and leave the eye at risk for secondary complications such as retinal detachment and glaucoma. Glaucoma due to untreated cataracts is one of the most common reasons for eye removal, as glaucoma is not only blinding, but very painful.
While cataract surgery does offer the only possibility of regaining vision, the prognosis for successful surgery at this time is approximately 85% to 90% in both eyes, with an increased risk of complications if surgery is performed when the eyes are severely inflamed. Potential blinding complications of cataract surgery include retinal detachment, uveitis (inflammation in the eye), glaucoma, infection and hyphema (blood in eye). Corneal ulceration, dry eyes, and temporary intraocular pressure elevation commonly occur following surgery and require medical management to treat these conditions. Aftercare for cataract surgery is extensive and involves multiple topical and oral medications with frequent recheck appointments.
Many times, we recommended starting topical and oral anti-inflammatory medications to control the uveitis. Uncontrolled uveitis risks development of secondary glaucoma. Due to the presence of rapidly developing cataracts, swollen lens, and risk of lens capsular tear, there is a higher risk of developing secondary glaucoma. Should glaucoma develop in either eye, the eye may no longer be a candidate for cataract surgery. Therefore the beginning goal is to minimize any intraocular inflammation in both eyes with topical medications with or without systemic anti-inflammatories until surgery can be performed.
If elected, surgery should be performed when you’re most available to administer post-operative medications. Post-operative patients must have a minimum of one month of strict cage rest, wear an E-collar (cone), and must follow a strict medication regimen to ensure proper healing of the eye and return to vision. Typical follow-up schedule includes returning one day, one week, two weeks, one month, two months, and four months post-operatively at the minimum.
Cataract surgery is an elective procedure with the goal of restoring eyesight to your animal. Any animal that has cataract surgery will likely be on an anti-inflammatory medication for life. However, any animal with cataracts that does not undergo cataract removal will also likely be on a topical anti-inflammatory eye medication for life, and may be susceptible to long-term complications if uveitis develops.
Prior to surgery, patients must be in good health for anesthesia. This is evaluated with general bloodwork (complete blood count, chemistry panel with triglyceride measurement, and urine analysis) and a physical examination. Diabetics must also have a fructosamine and urine culture performed, to ensure their diabetes is well regulated and they do not have an active urinary tract infection. If an infection is present at the time of cataract surgery, it can cause severe inflammation inside the eye, even leading to loss of the eye(s), and surgery will be delayed until the infection is controlled.
When cataracts are so advanced that the back of the eye cannot be seen, an electroretinogram (ERG) must be done to evaluate the function of the retina (film in the camera), and an ocular ultrasound is performed to ensure no retinal detachment is present. If the ERG is low, your pet may still have diminished vision following cataract surgery. If it is extremely low or extinguished, we generally do not recommend performing cataract surgery. If a complete retinal detachment is present, we also do not recommend cataract surgery. However, if a partial detachment is present, we may be able to perform a retinopexy at the time of surgery or a few days to weeks after. The purpose of the retinopexy is to “tack” a barrier around the detached retina to prevent further progression of the lesion.
Surgery itself involves putting your pet under general anesthesia and sterilely operating on the eye under the operating microscope. The surgeon makes a small incision into the cornea (clear surface of the eye), and then removes a part of the lens capsule. The entire cataract is then removed, and an artificial lens is placed within the capsule. In the case that the capsule is loose, already torn, or tears, a new lens may not be able to be placed. However, your pet will still be able to see better than with the cataract, as the cataract will be gone. Pets without an artificial lens may have some trouble with up-close vision, such as water bowls and curbs. Once the new lens is in place, the corneal incision is sutured closed.
The removal of cataracts is a surgical procedure; therefore, some postoperative inflammation is expected. After surgery, it is not uncommon for the eyes to appear more red as a result of the surgery, and there may be an increase in clear ocular discharge. These signs are a normal response to surgery and should resolve over the first 1-2 weeks, with marked improvement in the first 3-4 days. The cornea (clear outer surface of the eye) will also appear slightly cloudy at the area where it meets the sclera (white of the eye). This is a result of the surgical incision and stitches. The stitches will dissolve over a four- to six-week period following surgery, first becoming reddened and eventually leaving behind a small scar. This scar itself will not interfere with vision.
A common question after cataract removal is “how well can my dog see?” In certain cases, vision can be difficult to assess immediately after surgery. Vision is usually improved within two days with continual improvement over the first two weeks. It is not normal for the eyes to remain painful, for vision to fail to improve, or for vision to worsen over the first two weeks. If this occurs, please call your veterinarian immediately. A mild amount of squinting immediately after surgery is normal, but this should resolve after the first couple of days.
Cataract surgery is an invasive surgery that requires diligent post-operative care, including topical and systemic medications. Medications are prescribed to control inflammation and to prevent infection. The overall success of cataract surgery is highly dependent upon close compliance with the medication schedule.
At the time of discharge, most patients are put on 4-5 topical medications (eye drops) 4-6 times daily. They are additionally on 2-3 oral medications (given by mouth, with food). Medication should be given at evenly spaced intervals during your awake hours. If two drops are to be given at the same time, allow at least 5-10 minutes between drops. Be especially careful not to injure the eye with the medication bottle dropper. If debris accumulates near the eyes, you may wipe them gently with a wet cloth. Post-operative cataract patients must be closely monitored as surgical manipulation within the eye can result in adverse side effects, including inflammation. This inflammation post-operatively, if uncontrolled, can be extremely detrimental to the health of this eye.
Patients must wear an E-collar (plastic cone) at all times in the weeks following surgery to prevent trauma to the surfaces of the eyes and the small sutures that are present. The E-collar prevents scratching or injury to the eyes, protects the sutures placed during surgery so that they do not prematurely loosen, and allows for complete healing of the surgical site. The cone is generally more traumatizing for owners than the dogs, and they easily get used to them. Your veterinarian will let you know when it is safe for your pet to stop wearing the E-collar.
During this time, your pet will also need to be kept clean and dry, so please avoid bathing or swimming. If debris or discharge accumulates near either eye, you may wipe this away with a wet cloth.
If everything is within normal limits on the exam the day after surgery, then patients return for another exam in one week. If everything looks good at that examination, they return in another two weeks, or three weeks following surgery. At the three-week recheck, the number or frequency of medications is often reduced. Patients also generally no longer need to wear the E-collar.
Risks and complications
Cataract surgery is generally considered an elective procedure, and is not without risk. There is always a risk associated with general anesthesia, which is why patients are required to have a complete preoperative systemic evaluation. In general, if a patient is considered an excellent candidate, then the success rate of cataract surgery in dogs is between 85 and 90%, pending no pre-existing complicating factors.
Risks associated with the surgery include, but are not limited to:
- Excessive or persistent post-operative inflammation (uveitis)
- Corneal ulceration
- Inability to place an intraocular lens implant
- Retinal detachment
The last three complications may cause permanent blindness in your pet, and may even require surgical removal of the eye due to persistent discomfort.
The most common complications in the immediate post-operative timeframe include corneal ulcers and increased intraocular pressures (often called ocular hypertension rather than glaucoma). Patients may be placed on topical pressure medications temporarily in the immediate post-operative timeframe (a few days to a week), or they may remain on it permanently if they are at actual risk of glaucoma (a permanently elevated pressure that is damaging to sight).
Many diabetic patients also develop keratoconjunctivitis sicca, or dry eye (low tear production) and are placed on a topical tear stimulant that they will remain on for life.
Please monitor closely for any of the following signs and call your veterinarian immediately if any signs are seen or there are any questions:
- Eye pain, which typically manifests as squinting, rubbing, and/or excessive tearing
- Eye infection, which typically manifests as yellow, tan, or green discharge
- Bleeding from the outside or inside of the eye
- Cloudy corneas
- Sudden changes in vision
All patients will remain on at least one topical anti-inflammatory long-term – this may only be once or twice a day and it helps prevent the worst complication of cataract surgery, which is the development of glaucoma.