ABSTRACT: There are many conditions which affect the eye and require surgery. Often these procedures require specialised equipment and the veterinary nurse may need specialised knowledge to assist the veterinary surgeon. Implementing some small changes in your approach to dealing with ophthalmic cases can make a positive difference to their outcome. Abnormal conformation of the eyelids is one of the most common eyelid problems encountered in small animal practice. For this reason I have concentrated here on entropion surgery as the patient undergoing this procedure requires special attention from the veterinary nurse at many different stages throughout.

Entropion

Entropion is a ‘turning-in’ of the eyelid (Figure 1). It can occur on the upper or lower eyelid and affects different areas of the lids.

Figure 1: Entropion of the lower eyelid in a Rottweiler dog

In Mastiffs, the lateral canthus of the eyelid is often affected, while in brachycephalic breeds, it is generally the region of the medial lower eyelid. The main functions of the eyelids are the entrapment of debris, distribution of the tear film and protection of the eye.

In the absence of a fully functional eyelid, secondary conditions can develop resulting in further damage to the eye.

Trichiasis (normal hairs on the eyelid rubbing on the eyeball) can occur with the rolling-in of the eyelids; these hairs irritate the cornea and lead to corneal ulceration.

Entropions can be seen in both dogs and cats, but are more common in dogs. It can be a congenital or developmental disorder, but the most frequently encountered form is breed-related primary entropion. Certain breeds, such as Shar-Pei, can develop entropion at a very young age, with symptoms developing in the first few weeks of life in some cases.

Clinical signs and treatment

Signs of entropion include:

•   visible inversion of the eyelid

•   blepharospasm

•   epiphora

•   pain (demonstrated by the animal rubbing at the affected eye)

•   redness of the conjunctiva and, sometimes, cornea.

Treatment is usually surgical to achieve a permanent resolution to the problem. In some cases, juvenile entropion may resolve as the animal grows and temporary tacking sutures are used to evert the eyelids, as an interim measure, while waiting to see if this will occur.

The surgical technique most frequently used is the Hotz-Celsus. This involves excising an elliptical piece of skin and underlying muscle adjacent to the eyelid margin. The goal of the procedure is to evert the eyelid to a better anatomical position. The technique is modified in some cases, for example, shortening of the eyelid may be carried out at the same time.

Assessment of the patient

Before any medication is administered to the patient, a thorough assessment is carried out. Minimal restraint is required to ensure that tension is not placed on the skin around the face, as this will alter the position of the eyelids. The required degree of correction must be assessed before any anaesthesic agents are administered because the eyelid position will alter afterwards.

As ulcers often result from entropions, the eye should be stained with water- soluble fluorescein dye. This dye adheres to any exposed corneal stroma. When the overlying corneal epithelium is missing and the stroma exposed, a green stain uptake at the site of the corneal ulcer will be observed (Figure 2). If ulcers are present, the appropriate course of treatment for this must be decided upon.

Figure 2: The green stain of the fluorescein visible at the site of a corneal ulcer in a dog's eye

Preparation of the eye for surgery

A povidone/iodine solution, not scrub, is essential when aseptically preparing the eye, as the scrub will damage the corneal epithelium. The solution can have residual activity for up to one hour and the molecules can penetrate the sebum layer of the skin. It is virucidal, bactericidal and fungicidal. A 1:50 dilution in saline can be made up and stored for up to two weeks. A 1:10 dilution may then be used on the skin.

An easy way to obtain this dilution is to add 10 mls of the solution to a 1 litre saline bag. This can be reused over the two-week period. Once the animal is anaesthetised, the endotracheal tube should be tied in place around the lower jaw. This is done so that it does not interfere with the surgical site or compromise sterility.

Once the patient is stable, the following steps can be followed to prepare the eye:

•   Wear non-sterile gloves to decrease the risk of contamination.

•   Place an ophthalmic gel (Vidisic) in the eye to collect the hairs during clipping.

•   Using a small electrical clippers, clip an area of 2cm beyond the surgical site. Take care not to pinch the skin or cause clipper burn, because the skin in this area is very delicate and vascular. The cilia should not be clipped, and if the entropion is affecting the upper lid where these are present, a pair of scissors with some lubricant placed on the blades should be used to gently trim them.

•   Brush away hair or you can use sticky tape to remove the smaller hairs.

•   Clean the conjunctival fornix of the remaining debris with sterile cotton buds – taking care not to touch the cornea. The 1:50 dilution should be used here.

•   Clean the skin, using the 1:10 dilution, for at least two one-minute sessions before flushing with sterile saline. This will remove some of the debris along with the gel.

The nurse is also responsible for setting up the theatre for the surgeon. With ocular surgeries, there are a few special requirements in the theatre. A comfortable chair is useful – with armrests if possible – because arm rests improve the control required for the delicate nature of ophthalmic procedures. The height of the chair and operating room table should be adjustable to help aid positioning.

The correct positioning of the head is „ very important to enable the surgeon to make accurate incisions. This is facilitated with a vacuum bean-filled bag, a Buster cushion, whi
ch enables very accurate positioning of the head (Figure 3).

Figure 3: A cat positioned for entropion surgery – use of a Buster cushion to aid positioning for entropian surgery

Once the head is in position, a good surgical light source should be directed at the surgical site, taking care that it is not in place for too long or it could potentially damage the retina (Figure 4). Ideally, it should only be turned on once the surgeon is ready to start the surgery and switched off immediately once the procedure is complete.

Figure 4: The theatre set-up. Note the surgeon's positioning, the lighting and the positioning of additional equipment in the theatre

 

Monitoring the anaesthetised ophthalmic patient

Monitoring a patient during eye surgery can be challenging. 

First, the head is often in an unusual position on the Buster cushion. This can cause kinking of the endotracheal tube,

which can be corrected either with the placement of a small sandbag or some tape to maintain it in a patent position and keep the neck straight.

Second, during normal anaesthesia, the nurse would check the jaw tone and mucous membrane colour to assess anaesthesia. In ophthalmic procedures, the head is draped and these monitoring areas are inaccessible. In addition, the position of the eye, pupil size and the palpebral reflexes cannot be checked to confirm anaesthesia depth. While you can still rely on femoral pulses and observing patient breathing, additional monitoring equipment is recommended.

Additional monitoring equipment

Pulse oximetry, capnography, electrocardiography, and Doppler machines all have their place in monitoring the respiratory and cardiovascular systems during anaesthesia. A very good and inexpensive piece of equipment to have in the practice is an oesophageal stethoscope. It can be placed easily and non-invasively before surgery and allows monitoring of the cardiac rhythm and rate.

Ophthalmic instruments and their care

For eyelid surgery, an exhaustive list of additional instruments is not required. The materials used for entropion surgery are listed in Table 1 and illustrated in Figure 5.

Figure 5: Surgical instruments and materials required for entropion surgery

Ophthalmic instruments are much more delicate than other instruments in veterinary practice. They are lightweight and require minimal manipulation. To avoid damaging them, a specific cleaning routine should be adhered to when dealing with ophthalmic instruments:

1.   Once removed from theatre, open out the instruments and place in cold distilled water. This is to remove any blood before it sticks.

2.   Wipe them with a lint-free cloth and avoid using anything harsh such as a brush.

3.   The instruments can then be placed in a single layer, into an ultrasonic bath. Make sure they are not touching each other. This cycle should take 15 minutes. They are then removed from the bath and rinsed in water to remove the cleaning solution.

4.   Air dry or dry with a cloth before being lubricated and checked for any damage.

5.   Silicone protective cuffs can be placed on the tips of some of the instruments to protect them, if required.

Plastic instrument boxes with rubber fingers separating the instruments are very useful for storing them as they decrease the risk of damage and can be re-used many times.

Postoperative care

Immediately after surgery, the eye is gently cleaned with saline-soaked swabs and a topical antibiotic ointment is applied (Figure 6). One of the main postoperative complications of this type of surgery is self-trauma. The eyelid is a very vascular area, and if the patient were to scratch the wound, it could cause a great deal of damage.

Figure 6:. A cat with an Elizabethan collar in place receiving topical antibiotics immediately after surgery

The most common method of preventing this is the placement of an Elizabethan collar. It should be an appropriate size to prevent the patient interfering with the surgical site, rubbing it on anything in its surroundings, or removing the collar itself. This should be placed on the animal before it wakes up. If this collar cannot be tolerated by the patient, an alternative option is to bandage the dew claws, or place socks on them.

Eye medication should be clearly labelled with directions and storage instructions, because some preparations need to be refrigerated. It is very important to demonstrate to owners the correct method of administrating the ointment before they leave the clinic, as they are often so excited on seeing their pet that they do not listen to the instructions from the nurse! Point out that, if labelled for the left eye, it is the animal’s left eye (right as they look at it). This prevents medication being administered to the wrong eye. _

The owners should wipe the eyelid gently with some cooled boiled water and soaked cotton wool if there is any discharge, rather than letting it build up. After this, the ointment can be applied. Be sure to highlight the fact that only 1-2mm of ointment is enough to medicate the eye – too much can cause irritation.

Follow-up checks are required for entropion surgery. The sutures are dissolvable; but as there will be swelling at the surgical site for the initial postoperative days, it is important to re-evaluate after this stage. A ten-day check up is routinely scheduled, but the owners are always advised to contact the clinic sooner if the wound becomes red or develops a purulent discharge.

The prognosis is very good in the majority of these cases. 

Author

Susan Reddan

RVN Cert (Exotics) Dip AVN (Surg) Grad Dip Adult ED

Susan qualified as a veterinary nurse in 2001. Since then, she has completed a Certificate in Veterinary Nursing in Exotics and Wildlife and achieved a Diploma in Advanced Veterinary Nursing. Susan currently works as head nurse in Crescent Veterinary Clinic in Limerick and enjoys all aspects of nursing.

To cite this article use either

DOI: 10.1111/j.2045-0648.2012.00237.x or Veterinary Nursing Journal Vol 27 pp 409-412

Useful references

TURNER. S. [2005] Veterinary Ophthalmology, A Manual for Nurses and Technicians. London. Elsevier. PETERSON-JONES. S., and CRISPIN., S. [2002] BSAVA Manual of Small Animal Ophthalmology. 2nd ed. Gloucester. BSAVA.

GELATT. K, and GELATT. J. [2011] Veterinary Ophthalmic Surgery. London. Elsevier MITCHELL. N. Understanding eye medications and discharging the ophthalmic patient. Veterinary Ireland Journal. 2(4): 198-199.

Diploma in Advanced Surgical Nursing lecture notes. 2007.

   

• VOL 27 • November 2012 • Veterinary Nursing Journal