1 The ophthalmic examination

A full ophthalmic examination should be performed on all animals presenting with an ocular complaint. To perform this properly it is important to have a standard approach to all patients together with appropriate facilities and equipment.

The basic parts of the ophthalmic examination are:

• History taking

• Hands-off examination

• Hands-on examination

– Schirmer tear test readings

– Vision testing and neurological testing

– Ophthalmoscopy.

Further tests include:

• Ophthalmic dyes

• Nasolacrimal duct investigation

• Tonometry

• Laboratory investigation.

Table 1.1 Facilities and equipment required for the ophthalmic examination

General practice	Those with an interest in ophthalmology
• Room capable of being fully darkened • Table of adjustable height • Pen torch • Direct ophthalmoscope • Magnifying lens • Magnifying loupe • Tonometer (Shiotz)	All items listed left plus: • Slit lamp biomicrosope • Finhoff transilluminator • Indirect ophthalmoscope • Goniolens • Tonopen or Tonovet tonometer

Disposable items required for ophthalmic examination are:

• Schirmer tear test papers

• Fluorescein paper test strips

• Rose Bengal dye (for specialty ophthalmology practice)

• Cotton wool and gauze swabs

• Tropicamide (Mydriacyl 1% Alcon)

• Topical anaesthetic (proxymetacaine)

• Sterile saline

• Lacrimal cannulae

• Bacterial swabs and transport media

• Slides and laboratory equipment.

HISTORY

History taking can be divided into general history and that specifically pertaining to the eyes. A general history should consider the following points:

• Genetics: As breed pedigree dogs and cats can suffer from inherited eye diseases, the breed is of importance. Even in crossbred dogs the general type of dog might be relevant – for example, terriers are prone to lens luxation which is seen in pedigree wire haired fox terriers and miniature bull terriers among others, but is common in all types of Jack Russell from the pedigree Parson terrier to the general terrier type. In cats, corneal sequestrum is a common condition in Persians and Burmese while retinal degeneration is recognized in Siamese and Abyssinian breeds. Clearly we should not assume that just because a patient is a particular breed it will definitely be suffering from a certain condition – but breed-related diseases are frequently encountered in veterinary ophthalmology.

• Age: This is always a factor to be considered. Conditions such as entropion and prolapse of the nictitans gland (cherry eye) are common in young animals (3–12 months) while neoplasia is more common in older patients. Congenital problems such as cataract and collie eye anomaly should be considered when patients come in for their initial vaccinations (see Appendix 4).

• Sex: Although of less importance with regard to ophthalmology than for some other disciplines, the sex of the patient might have some influence on its ocular disease. For example, young male dogs are more prone to entropion while keratoconjunctivitis sicca is seen in neutered females more commonly than entire males.

• General health: Many ocular conditions can be manifestations of systemic disease and questions related to appetite, general demeanour and concurrent illness are extremely important. Patients might be presented with sudden blindness as the owner’s complaint, which turns out to be due to diabetes mellitus and the owner has failed to appreciate that the polydipsia, weight loss and so on were actually due to a serious medical condition.

• Medications administered: Previous or ongoing medication may be the cause of some ophthalmic conditions. An example is the dog with colitis which is treated with sulfasalazine (Salazopyrin) and develops an acute, severe bilateral keratoconjunctivitis sicca. Some ophthalmic drugs can cause a localized hypersensitivity which exacerbates the ocular disease. Owners are notorious for using left-over medication from a previous problem – which might not even have been for the pet! Such actions can be deleterious to the patient.

• Presence of other pets in the house: This is particularly relevant when considering infectious diseases such as feline herpes virus where repeated infection can be a problem. If the owner has more than one pet it is important to find out if others are affected. The presence of a new puppy in a home with a cat might be relevant if the puppy is brought to the surgery with an acutely painful eye – it is quite likely that the cat has scratched it!

• Source of the pet: Cats from rescue centres and/or breeders may have pre-existing diseases such as herpes or Chlamydophila infections, while dogs from puppy farms may be prone to inherited ocular disease since unscrupulous breeders pay no attention to such things.

• Travel history: This is becoming more and more relevant in the UK since the introduction of the Pets Passports schemes but is relevant in all countries. Several Mediterranean diseases such as leishmania and ehrlichia can have ocular involvement.

Once a thorough general history has been taken we can move on to the more specific ophthalmic history. This will include asking the owners the following questions:

• What was the first thing the owner noticed wrong with the eye(s)? Were they concerned about discharge, pain, redness or other change in colour, an alteration in appearance of the eye (e.g. bulging or sunken) or perhaps they noted a decrease in vision.

• When did they notice something wrong? The time span of the disease is relevant – some owners will bring a pet along to the surgery immediately while there are those owners who leave the pet for weeks or even months before presenting it.

• Progression of the problem? Has the problem got worse, better or stayed the same since it was first noticed? Has it been present continuously or has it been intermittent? If the latter, has the owner noticed any ‘trigger factor’ which brought on a return of the symptoms? For example, did the atopic Labrador always have itchy eyes when he returned from a walk through certain fields? (This could suggest an allergic component.)

• Is the problem unilateral or bilateral? As mentioned in the general history taking, systemic disease may be the underlying problem and this is much more likely with bilateral conditions. With infectious disease we might also expect a bilateral presentation although it is not unusual for one eye to be affected before the other – Chlamydophila in cats is an example where a delay of a few days can be seen before the second eye develops symptoms.

• Treatment – has the owner given any medication? If so, what, and was it beneficial or detrimental?

• Previous ocular history? It is important to establish whether the pet has had any ocular problem in the past – and, if so, was the presentation the same and was it the same eye which was affected? Also, response to treatment given previously is relevant.

THE OPHTHALMIC EXAMINATION

Hands-off examination

While the history is being taken the patient should be observed. Dogs are allowed to wander off the lead and investigate the consulting room while cats are encouraged out of their baskets and then watched from a distance. It is important to look at the behaviour of the pet, along with the gross appearance of the eyes and face. Signs of ocular discomfort – blepharospasm, increased lacrimation or other discharge, symmetry of the eyes and face – sunken or small eyes, enlargement of the globe, periorbital swellings or squints for example. Clues might inform us that the animal has been rubbing – periorbital hair loss and erythema or saliva staining on the front legs where the animal licks then rubs the face might be evidence of self-trauma. Basic assessment of the visual ability of the patient can be undertaken at this time – blind animals will often stay close to the owner and not move around the room, while if they do move they are often very cautious, sniffing the environment and exhibiting a high stepping gait.

Hands-on examination

The first part of the hands-on examination takes place in a well-lit room. The patient should be gently restrained – one hand under the chin and the other behind the back of the head is usually sufficient. A trained nurse is invaluable during ocular examinations – most owners are not very good at restraining their pets in general, and when you are very close to the biting end it is particularly important that the patient is properly held by a confident adult!

A close inspection of the gross appearance of the eyes and face is performed with illumination such as a pen torch. Particular things to consider include the presence of any ocular discharge – the nature of it, whether unilateral or bilateral and the amount of it. Some dogs commonly have a small amount of mucoid discharge at the medial canthus, especially those with doliocephalic conformation such as Dobermanns, and it can be considered a normal finding in such animals. The size of both eyes should be compared – they should be symmetrical but if one is larger than the other it is necessary to establish whether one is enlarged (hydrophthalmic) or if one is shrunken (microphthalmic). In addition to size, the actual position of the eyes should be noted – looking from above the patient directly down on the head can assist in establishing the presence of exophthalmos, enophthalmos or strabismus. General head symmetry and the presence of periorbital swellings should also be noted.

It might be necessary to take samples for laboratory analysis at this stage if indicated. Swabs for bacterial culture and isolation should be taken before any discharges are cleaned away.

Schirmer tear test readings

Schirmer tear test readings should be taken before the eyes are cleaned or handled further. Commercial tear testing strips are used (colour bar calibrated strips are the easiest to use and are available from Schering-Plough). The strips come in sterile plastic wallets. The strips should be bent at the notch while still in their plastic wallet (to prevent sweat and grease from hands interfering with the readings). The packet is opened and each test paper is held at the distal end. The shorter piece is placed in the ventral conjunctival sac half to two-thirds along from the medial canthus (i.e. out of the way of the third eyelid) (Figure 1.1). The strip is left in position for 1 minute before removing it and immediately reading the level of wetting on the scale (see Table 1.2). It is easier to hold the patient’s eye closed to prevent the strip from falling out prematurely. Topical anaesthetics are not used prior to measurement.

Figure 1.1 Schirmer tear test in a cat showing placement of paper strip.

Table 1.2 Schirmer tear test readings in dogs and cats

	Dog	Cat
Normal	15–25 mm/min	Readings variable and often lower than in the dog, especially in stressed cats
Borderline	10–15 mm/min
Keratoconjunctivitis sicca	<10 mm/min