Description

STEP 1: GROSS INSPECTION

The ocular assessment begins with careful observation of the patient from a distance without touching the patient (as this may cause distortion of the palpebral fissure). While observing, ask yourself:

• Are both eyes open normally? Is there evidence of pain or photophobia? Is the animal blinking normally?
• Are the eyes of normal size and position? Is there evidence of exophthalmos or buphthalmos? Are the pupils of equal size?
• Is the eyelid conformation normal? Is there evidence of entropion or ectropion (usually of the lower lid)? Is the 3^rd eyelid elevated?
• Is there ocular discharge? What is its nature?

STEP 2: ASSESSING VISION  

Vision is most commonly tested by evaluating the menace response. This involves making a sudden threatening gesture, which is supposed to elicit a blink response. It is important to note that the menace response involves cerebral cortical integration and interpretation and therefore is not a reflex. The menace response should be evaluated in one eye while the other eye is being covered. Be careful not to touch the eyelashes/hair of the patient or to cause wind movement, as this may lead to a "false positive" response; consider making the menace gesture behind a glass partition.

STEP 3: PUPILS

Use a dim light, and stand at a distance so you can visualize both pupils simultaneously, using the tapetal reflection

Next, use a bright light to evaluate the Pupillary Light Reflex (PLR). Unlike the menace response, the PLR is a subcortical reflex. Therefore, it does NOT test vision, and a normal PLR may be found in a cortically blind animal..

If one of the pupils does not react to light, or if it can’t be visualized (e.g., in cases of hyphema), the consensual PLR should be checked.

STEP 4: EXAMINING THE ANTERIOR STRUCTURES OF THE EYE

The rest of the examination is continued in the dark, using magnification and a focal light source, as the anterior structures of the eye are examined in an anatomical order.

4A: Eyelids & Eyelashes

Evaluate the size of the palpebral fissure, looking for a narrowed or enlarged fissure. Carefully examine the skin, looking for discharge and for signs of dermatological disorders, such as dermatitis, alopecia, scaling, swelling, crusting, ulceration, etc. Pay particular attention to the eyelid margin. In a normal animal, you should see the entire margin in close contact with the globe. Lack of contact may be due to ectropion (drooping lid). On the other hand, if you cannot see the margin, or parts of it, the lid may be everted (entropion). Eyelash abnormalities may be better visualized if the lid is slightly retracted. Dark lashes can then be highlighted against the background of the white conjunctiva.

4B: Third Eyelid & Conjunctiva

At rest, the 3^rd eyelid should be mostly retracted and hardly visible. Examine the conjunctiva lining the inner aspect of the eyelids and globe for change in color, congestion, edema, prominent vessels, masses, thickening, discharge, moistness or subconjunctival hemorrhage.

4C: Cornea

The normal cornea should be smooth and transparent. Any deviation from these characteristics represents pathological changes. Look for loss of transparency due to edema, pigmentation, vascularization, cellular infiltration, lipid or mineral deposition, or fibrosis. Look for surface irregularities which may be due to ulceration, perforation and iris prolapse, granulation tissue, or keratoconus.

4D: Anterior Chamber

Assess the depth of the anterior chamber (best visualized from the side), as it may be increased or decreased in various intraocular diseases. In normal animals, the aqueous filling the anterior chamber should be clear. Look for any opacities or masses such as blood, fibrin, hypopyon, aqueous flare, luxated lens, persistent pupillary membranes, iris cysts, or vitreous strands.

4E: Iris & Pupil

Look for alterations in pupil shape, which may be due to adhesions, or iris atrophy, hypoplasia or coloboma. Changes in the color of the pupil may indicate cataract, hemorrhage, or retinal detachment. The size of the pupil may be altered in uveitis, glaucoma and various diseases of the retina or the nervous system.

Examine the surface of the iris for any masses or changes in color. These may be due to inflammation, hemorrhage, or neoplasia. Fluttering of the iris may indicate lens luxation.

4F: Lens

The lens may be examined with direct visualization or by retroillumination using tapetal reflection. The two main pathologies are luxation or opacities, which would indicate cataract

STEP 5: OPHTHALMOSCOPY

Ophthalmoscopy should be conducted in a dark room, following pupil dilation. Carefully inspect the entire fundus, evaluating changes in the tapetum, non-tapetum, blood vessels, and optic disc.

Learning Objectives:-

• Which 3 things should you look for before you even touch the patient
• How to assess cortical vision
• How to assess subcortical reflexes
• How to examine all of the ocular tissues
• What tests should you perform on a patient presenting with a red eye?

Areas Covered in the Session:-

• Equipment needed for ophthalmic examination
• Examination from a distance
• Evaluating vision and subcortical reflexes
• Examination of anterior structures-eyelids, conjunctiva, cornea, anterior chamber, iris and pupil
• Post-dilation examination – lens and fundus
• Special diagnostic techniques.

Why Should You Attend?

Many veterinarians are apprehensive about performing an ophthalmic examination of their patients. However, ophthalmic examination should not be complicated or expensive! All that’s required is a good light source, a few accessories and drugs, and an understanding of the anatomy of the eye. Following this talk, you will never be scared of doing an ophthalmic examination.

Who will Benefit? 

General practitioners; veterinary technicians and nurses.