ABSTRACT: This article addresses the management of patients with cataracts or lens luxation. It explains the selection of patients for cataract surgery, as well as the state-of-the-art surgical technique for cataract removal and the required after-care. Furthermore the treatment modalities for lens luxation are discussed. The second part of the article focuses on the nursing aspects of these conditions and, in particular, the necessary after-care following intraocular surgery. Possible short- and long-term complications are visually impaired and blind dogs.

Cataract assessment

If a cataract significantly impairs vision, the owners might wish for their dog to have cataract surgery. However, before cataract surgery can be attempted, it is important that the patient is examined for concurrent systemic and ocular diseases.

Are concurrent conditions present that will increase the patient’s anaesthetic risk? Are potentially infectious foci present elsewhere in the body that should be addressed prior to surgery?

Cataract surgery interrupts the barrier between the eye and the body (blood- ocular barrier), so focal infections – including, for example, dental disease or urinary tract infections – can have detrimental effects on a newly operated eye.

Ocular surface diseases, such as ‘dry eye’, can interfere with wound healing and intraocular inflammation at the time of surgery will impair the successful outcome. Treatable conditions should, therefore, be addressed before surgery, to allow the best possible result.

In cases of concurrent ocular diseases that result in visual impairment themselves – retinal atrophy or retinal detachment, for instance – the benefits of cataract surgery might be limited and will have to be discussed between owner and ophthalmologist.

Cataracts often prevent visualisation of the posterior segment of the eye; thus additional diagnositic tools, such as ultrasound (Figure 1) and electro- retinography (Figure 2) are needed to examine the ocular anatomy and retinal function respectively.

Figure 1: Ocular ultrasound of a 12-year picture of an eye The canine lens – cataract surgery and lens removal

Figure 2: Electroretinography (ERG) in a 15-month old miniature long-haired dachshund. A normal single-flash ERG trace is shown in the right bottom corner

A patient that is suitable for cataract surgery will often need anti-inflammatory medication before surgery.

Cataract surgery

The recommended surgical technique for cataract removal is phacoemulsification. After an initial corneal incision (~3mm) a round opening is created centrally in the anterior lens capsule. The cataractous lens material is then removed using special phacoemulsification units that are available in different referral institutions. If the surgical situation allows it, an intraocular lens is placed into the now empty lens capsule (Figure 3). Finally the corneal wound is sutured.

Figure 3: An 18-month-old Cocker spaniel, three months after cataract surgery. Note the healed incision at 12 o'clock. The pupil is dilated and the intraocular lens is visible

After-care

Post operative treatment with antibiotics, as well as anti-inflammatory medication, is essential over an extended period of time. Patients will need to be monitored for complications, such as glaucoma, and retinal detachment that can occur at any time following cataract surgery.

Lens luxation

Different opinions exist with regards to the treatment of lens luxations.

An anterior lens luxation always presents a surgical emergency. The anteriorly luxated lens is mostly removed in total through an extensive excision (~160°) of the peripheral cornea (Figure 4). Lenses that are only partially dislocated (subluxation) or posteriorly luxated can be removed; retrieving them from the posterior segment of the eye, however, requires more manipulation of the vitreous (hydrogel that fills the posterior segment) and results in a greater risk for retinal detachment and subsequent vision loss.

Figure 4: A 4 Vi-year-old Yorkshire terrier one day after lens removal. Note the extensive corneal wound that is necessary to extract the luxated lens. The arrows mark the extent of the corneal incision

Many veterinary ophthalmologists prefer the use of eye drops that result in a constricted pupil (miosis). This aims at entrapping the lens in the posterior segment to prevent an anterior lens luxation. The patients are usually on this medication twice daily and for the long term. However, the lens can still occasionally luxate anteriorly, in which case urgent surgical removal becomes necessary.

Nursing aspects

Cataracts will present regularly in general practice. Owners of diabetic patients, in particular, should be informed early on about this common sequela.

If dogs are affected by vision-impairing cataracts or lens luxation, and surgery is needed, it is important that owners are prepared for the regular and extended medication required to prevent complications.

Topical medication should be made as positive as possible for the dog and followed by a ‘treat’ or gentle play. If dogs continue to object to topical medication, this might indicate undue discomfort. Pain management must be discussed and an adverse reaction to the medication should be considered if there is no other reason for the discomfort.

The nursing staff should ensure that owners are confident with the application of eye drops/ointment, as well as the giving of oral medication. For an easy way to administer topical medication, the dog sits with its back to the owner so it can’t back off. One hand supports the chin; the other is resting on the head and holds the tube or bottle. By moving the skin with the hand that is resting on the head, the upper eyelid can be opened and the drug administered (Figure 5).

Figure 5: Administration of ophthalmic medication in a dog. One hand is resting on the head, elevating the upper eyelid and administering the medication at the same time.

In referral hospitals, the nursing staff will be responsible for pre- and after-care of the surgical patients. This routinely involves the frequent application of anti-inflammatory
drops and mydriatics (drugs that dilate the pupil) immediately before surgery. Afterwards, the recovery from anaesthesia should be as gentle as possible, to avoid head-shaking or trauma.

The recovery kennel should be well- padded and dogs should be monitored at all times and wear a Buster collar or foot bandage when waking up, to prevent self-trauma. Anti-inflammatory medications, as well as antibiotics, are administered depending on the ophthalmologists preference.

The suture material used in ophthalmic surgery is particularly delicate (0.02¬0.04 mm in diameter); hence the newly operated eye should be treated as fragile. To prevent patients from rubbing, the use of a Buster collar is advisable. Patients should be kept quiet for at least two to three weeks to ensure uncomplicated wound healing (lead walks only). Dogs should not be ‘pilled’ to administer oral medication.

To minimise fluctuation of intraocular pressure, the dog should be managed so that it does not put (or receive) pressure on its neck. A harness, instead of a collar, is an easy way of preventing this during exercise.

As complications can occur at any time after intraocular surgery, owners should be encouraged to present their animals for regular re-examinations as advised by their ophthalmologist.

If the lens in a dog is removed and can not be replaced by an artificial lens, the dog will be long-sighted. This means that close structures will appear ‘blurry’, while objects in the distance can be seen without problems. Contact lenses or ‘Doggies’ to compensate for this are commercially available; but they are challenging to maintain and can be poorly tolerated.

Sometimes patients become blind, regardless of treatment, and many owners become concerned about the dog’s quality of life and even consider euthanasia. In the author’s experience, most dogs cope incredibly well with the loss of vision as they use their other senses – such as smell and hearing – to compensate. 

Author

Claudia Busse DVM MRCVS

Claudia Busse graduated from the School of Veterinary Medicine, Hanover, Germany in 2004. Afterwards, she completed a doctoral thesis on inherited ocular diseases and worked in general practice. In 2005, she started a rotating internship at the Animat Health Trust in Newmarket and subsequently completed a residency in veterinary ophthalmology. Claudia currently works at the AHT as a clinician in ophthalmology.

To cite this article use either

DOI: 10.1111/j.2045-0648.2010.00015.x or Veterinary Nursing Journal Vol 26 pp 59-61

Recommended reading

The book Living with blind dogs by Caroline D Levin is an excellent help for (he owner dealing with this difficult situation. It explains the ocular anatomy, different reasons for blindness and ways to help the dog in this new situation.

Sally Turner's book Veterinary Ophthalmology A Manual for Nurses and Technicians provides further reading for nursing staff with deeper interest in patients with ophthalmic diseases.

Further reading

BSAVA Manual of Small Animal Ophthalmology, Ed. Simon Petersen-Jones and Sheila Crispin, 2nd edition, BSAVA, Gloucester. 

Veterinary Ophthalmology. Ed. Kirk N Gelatt, 4th edition, Blackwell Publishing.

 

Veterinary Nursing Journal • Vol 26 • February 2011 •