Vetnuus | September 2024 41 cause. If the eye has been affected for some time a considerable amount of keratitis, and even granulation tissue, may be present. After Novasin topical anaesthesia is applied the third eyelid can easily be everted with a cotton-tip to allow examination of the ventral fornix. Remember to use a focal light source and some magnification, the easiest and most widely available tool is your otoscope without the green ear tip and with the magnifying lens in a closed position. Small pieces of plant matter or grass seeds identified in the conjunctiva can easily be removed in a sedated patient with fine forceps. Cacti glochids however are not easy to remove! They are very fine and break off easily. They also have fine hairs preventing extraction and will require general anaesthesia and high magnification to resect them. These fine glochids are often distributed diffusely over the conjunctival and corneal tissues. These patients are best treated by referring them for surgery under an operating microscope. Next, examine the cornea. Start off by evaluating the specular reflection of the surface from a distance. This should be clear and the light reflecting off the corneal surface should not be distorted. If a slight distortion is noted pay close attention to this region with magnification. Again, the most practical tool to use would be the otoscope headlight with the magnification lens. Evaluate the corneal limbus and superficial surface. Look for superficial blood vessels that would indicate an irritation to the cornea. Common foreign bodies noted on the cornea are pieces of plant matter that are flat and physically stuck to the cornea. These are often a slightly tan colour, round to oval shaped, and they do not move with eyelid blinking due to being stuck on the corneal surface by negative pressure or slightly lodged in the upper stromal layer of the cornea. If you have applied Novasin, these may be removed by gentle irrigation. An easy method is to use a 23G yellow catheter attached to a small 5ml syringe filled with saline. Apply generous pressure to the plunger to create a stream of saline directed at the foreign body. Most superficial pieces of plant matter can be dislodged in this manner. If the foreign body is lodged deep within the corneal stromal tissue the best may be to refer the patient for surgery under an operating microscope. If referral is not an option, then under general anaesthetic a fine 25G needle tip may be used to gently remove the foreign body, but caution should be applied, and the owner warned of potential globe rupture if a descemetocele has formed. If the globe ruptures immediate referral is advised, alternatively, an enucleation may be performed. For most of these foreign body injuries, a corneal defect or ulcer may be present once removed. Fluorescein stain examination should be performed once the foreign body is removed to identify corneal lesions. The cobalt blue filter on your ophthalmoscope must be used to examine the eye after the fluorescein stain is applied. If an ulcer is present it is advised to be treated as a routine with topical lubricants, topical antibiotic drops and oral pain control with an appropriate NSAID. Avoid topical NSAIDs/corticosteroids as these will delay healing of the cornea or worse, could result in keratomalacia. Healing should be uneventful within 7-10 days, and always advise a follow-up examination with fluorescein stain examination after 10-14 days. If the cornea does not stain positively anymore, the topical antibiotics may be stopped, and the lubricant may be completed. If healing is not complete, then the course of topical antibiotics should be continued, and the eye examined again within 5-7 days. If healing is still not complete a referral to an ophthalmologist is advised, or a thorough examination under sedation. Regulars I Ophthalmology Column Figure 2: Cactus glochids penetrating the cornea of a dog. The second picture illustrates the fine hairs on each glochid. The last picture is corneal tissue resected with a lamellar keratectomy from the same patient (40x mag). Figure 3: Image one is the cat’s eye from above. Note limited lens content in the posterior segment and no retinal detachment or hyphema. The second image is an unlucky patient with severe lens content rupture and retinal detachment. The linear hyperechoic foreign body can be seen penetrating through the lens in both images. >>>42
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