ABSTRACT: The aim of this article is to explain cataracts and the cataract surgical procedure, to clarify the most suitable patient and the most suitable time for cataract surgery, and to describe ways to make the quality of life better for the visually impaired/blind dog that cannot undergo cataract surgery.

Introduction

Many dogs develop cataracts in their lifetime and they can become almost blinded by them, such that their quality of life is affected.

The majority of cataracts can be surgically removed, giving the dogs their vision back and thereby improving their quality of life. However, in some, their cataracts are not suitable for surgery and so the dogs must learn to live with their reduced vision; but there are a number of things that the owner can do to enrich the life of their blind dog.

What is a cataract?

The lens is the main refracting structure in the eye which focuses incoming light rays onto the retina (Figure 1). A cataract is a white opacity of the lens which impairs vision.

Figure 1: Simplified cross-section of an eye

In its normal state, the lens is transparent and consists predominantly of soluble proteins (Figure 2). With increasing age, the solubility of the lens proteins decreases and the centre of the lens (the lens nucleus) becomes denser, imparting a bluish/grey appearance to it (Figure 3).

Figure 2: A normal eye

Figure 3: An eye with a cataract

This age-related change is called nuclear sclerosis. It is reported not to affect a dogs vision since it does not impair the passage of light rays. A cataract, however, does affect a dog’s vision because it does reduce the transmission of light rays.

•   Cataracts can be congenital, inherited, developmental, and secondary to metabolic disease such as diabetes

•   Cataracts can be incomplete and not significantly affect vision but, if the cataract becomes complete and fills the lens, then a dog will struggle to see clearly

•   Cataracts go through stages of development described as immature, mature and hypermature. The more mature the cataract, the greater the impairment of vision. 

Some cataracts develop through these stages so quickly, as in diabetes, that many dogs are given little time to adjust to their reduced vision and become seemingly ‘depressed’ by this dramatic change.

What is the cataract surgical procedure?

The surgical procedure used today is the same as that used in man, whereby a small hand-piece with an ultrasonically vibrating tip is used to break up and soften the cataract, which is then aspirated out of the eye – a technique called phacoemulsification (Figure 4).

Figure 4: Phacoemulsification hand-piece

The phacoemulsification surgical procedure has a number of advantages over the old-fashioned manual extraction of cataracts in that the incision wound in the eye is smaller, the surgical time is shorter, and there is a more complete removal of the lens content, all resulting in a better postoperative result (Figure 5).

Figure 5: Picture of cataract surgery being performed

Modern cataract surgery in the dog carries a 90 to 95 per cent success rate; with dogs returning to their pre-cataract state almost completely, especially if synthetic intraocular lenses (IOL) are implanted at the time of surgery (Figures 6 & 7).

Figure 6: An eye before surgery

Figure 7: The same eye after surgery with an IOL inserted

There is no medical treatment for cataracts.

Who is the ‘ideal’ patient for cataract surgery?

The most suitable patient is one with a gentle/calm temperament, one who has no other significant eye or health problems and one where the cataracts have only recently developed to completion and maturity such that vision is now impaired.

If cataracts are left in eyes for too long, they become progressively hard and there is an increased likelihood that there will be other lens-induced complications in the eye – all of which would render these eyes less suitable for surgery owing to an increased risk of postoperative complications.

The dog must be fit enough to undergo this elective surgical procedure and must, therefore, be examined thoroughly by a veterinary surgeon prior to being referred to a veterinary ophthalmologist to ensure the dog’s suitability.

Pre-anaesthetic blood tests are a normal requirement and, if the dog is diabetic, the patient must be stabilised prior to surgery.

The postoperative management is quite involved and requires a great deal of care by the owner. The dog must be kept as quiet as is possible for a week or two after the surgery and all treatments must be administered according to the ophthalmologists instructions.

These will include frequent topical medication (usually several different drops 3-4 times daily initially) as well as systemic medication. The owners must be available to bring their dogs for re-checks with the ophthalmologist for some time after the surgery in order to ensure that the eyes are responding as expected.

Intra-operative and postoperative complications can arise. Fortunately these are fairly infrequent and rarely of any significance; but must be understood prior to proceeding with the surgery.

 

What difference does cataract surgery make?

A huge difference if all goes well, especially in those dogs where the cataract development and, hence the onset of blindness, was quite rapid (for
example, in dogs with diabetes mellitus) (Figures 8 -11).

Figure 8: Dog before surgery

Figure 9: Same dog after surgery

Figure 10: Dog before surgery

Figure 11: Same dog after surgery

Following successful cataract surgery, dog owners often say things such as “You have returned a puppy to me” or “I had forgotten just how naughty my dog could be!” And the overall feeling from owners is that it was well worth all the effort (Figures 12 & 13).

Figure 12: Dog before surgery

Figure 13: Same dog after surgery

What if a dog cannot have surgery?

Not every dog is suitable for cataract surgery. A dog may have significant underlying disease which would increase its anaesthetic risk – it may be considered too old and/or too excitable, or even aggressive, or the owner might not be able to manage the postoperative care.

The dog may have other significant ocular problems, such as progressive retinal atrophy (PRA) or uncontrolled keratoconjunctivitis sicca (KCS). Also, the cataracts may have been present for too long making them unsuitable for surgery owing to complications of lens-induced uveitis (inflammation and scarring caused by the chronic cataract).

Just because a dog cannot undergo surgery, does not mean it cannot lead a reasonable life. There are many dogs which are blind for a number of reasons yet are still very happy and coping with their visual impairment.

Owners can make things easier for their blind dog by:

•   keeping the layout of their home and their garden the same

•   keeping to familiar walks

•   using plenty of audible cues and toys

•   walking their dogs on a harness and lead rather than on a collar and lead since it makes the dog feel more secure and makes the dog easier for the owner to control

•   finding them a canine ‘friend’ (if practical) – preferably of similar size and temperament and with no eye problems, who hopefully will become ‘their eyes’. It is advisable that owners contact their local dog rescue centres to discuss this further.

Summary

If a dog’s lenses become opaque owing to cataract formation, and the dog’s vision becomes affected, then it is recommended that the dog be presented early to a veterinary surgeon for a diagnosis.

If the dog has cataracts, it should be referred promptly to a veterinary ophthalmologist for consideration for cataract surgery, since the early cataract patient has the better surgical result.

If a dog cannot undergo surgery, however, owners can improve their dog’s quality of life by a few simple changes to their management routine.

Author

Denise Moore

MA VetMB CertVOphthal MRCVS VN

Denise worked for eight years as an veterinary nurse, mostly at the RSPCA Animal Hospital in Putney, London, where she developed a special interest in ophthalmology. She went on to train as a veterinary surgeon and graduated from Cambridge University in 1990. After several years in practice and some eight years at the Royal Veterinary College in London – firstly as an Intern, then as a Resident and finally as a Consultant in Comparative Ophthalmology – Denise headed to the south coast to set up her own ophthalmology referral service for the Grove Lodge Veterinary Hospital in Worthing.

To cite this article use either

DOI: 10.1111/j.2045-0648.2011,00072.x or Veterinary Nursing Journal Vol 26 pp 273-275

 

 

Veterinary Nursing Journal • VOL 26 • August 2011 •