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Ocular Diseases of Companion Animals

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1 Ocular Diseases of Companion Animals
Animal Technology VT-116 Adapted from Dr. Kristek

2 The Eyelids Serve to protect, clean, and keep the globe hydrated
Common diseases: Entropion Hair chronically touches cornea Shar Pei, Chow, Bulldog, Golden Retriever, Persian cats, also seen in lambs and kids Can be hereditary or acquired: spastic entropion secondary to pain Ectropion Exposure of conjunctiva leads to inflammation and higher risk of infection St. Bernards, spaniels, hounds

3 The Eyelids Entropion Ectropion

4 The Eyelids Meibomian Glands – aka Tarsal Glands
Produce meibum, a lipid-heavy secretion that slows down tear evaporation and increases surface tension, holding tears in-between eyelids and surface of eyeball

5 Lacrimation

6 The Eyelids Meibomian Gland Adenoma Other eyelid tumors
Most common form of neoplasia in the eyelid in dogs Nearly always benign Most common in dogs > 8 years old Other eyelid tumors Melanoma, basal cell carcinoma, squamous cell carcinoma (SCC), adenomas, papillomas

7

8 “Cherry Eye”

9 Conjunctiva Conjunctivitis – inflammation of the conjunctiva
Most common eye disease in domestic animals Can be due to infection, trauma, or allergic response Common signs: Erythema Discharge Inflammation Discomfort (demonstrated by repeated blinking, squinting, or abnormal head position)

10 Feline Herpesvirus

11 The Cornea Corneal ulcer – a break or erosion in the layers that form the cornea

12 The Cornea Corneal ulcer
Can be the result of trauma, infection, or of idiopathic causes Can affect one or more of the five layers of the cornea: Epithelium Bowman’s Layer/Bowman’s Membrane Stroma Descemet’s membrane Endothelium

13 The Cornea Corneal ulcer Not usually visible to the naked eye
Fluorescein eye stain test Two categories: Simple ulcers Deep Ulcers

14 The Cornea Keratoplasty
A graft of conjunctiva or flap of donor corneal tissue is placed over the site of the descemetocele. The graft provides immediate blood supply to damaged or abnormal cornea to speed healing and increase the amount of medications reaching the area

15 The Cornea Corneal Debridement
Debridement of the ulcer promotes healing by removing the outer non-adhering layer of the cornea with a cotton swab.

16 The Cornea Grid Keratectomy
The tissue under the diseased outer surface of the cornea is altered by making tiny scratches on the surface with a fine gauge hypodermic needle.

17 The Cornea Superficial Keratectomy
The outer or superficial layer of the affected cornea is surgically removed by careful dissection, using an operating microscope.

18 The Cornea Pannus

19 Fluorescein Dye Test PROCEDURE:
Take out the Fluorescein dye strip, being careful to handle the non-dye end Apply a drop of eye wash or saline to the orange end of the strip, and touch the strip to the animal’s eye If only one eye appears infected, touch the normal eye first, then the infected eye Allow the animal to blink

20 Fluorescein Dye Test PROCEDURE cont’d:
Rinse the eyes will with eye wash Use a wood’s lamp, an ophthalmoscope with blue light, or even a simple pen light to examine the surface of the cornea for any retention of stain. It may be very subtle, or very obvious – so take your time examining May wish to darken room to better visualize the stain

21 Fluorescein Dye Test

22 The Uvea Uveitis MANY causes, may be multifactorial Infection
Immune-mediated reaction Metabolic Parasitic Traumatic Neoplastic

23 Uveitis

24 KCS

25 Schirmer Tear Test (STT)
Requires the use of a special tear test strip which looks like a small piece of filter paper, sometimes with a scale in millimeters printed on it The end of the strip is bent and then carefully placed under patient’s lower eyelid Leave the strip in this position for 60 seconds As the tear film travels up the strip, it creates a line that can be measured on the mm scale

26 Schirmer Tear Test

27 Schirmer Tear Test Normal tear production in the dog is mm/minute A KCS diagnosis will be made with less than 10mm/min results AND clinical signs of KCS One low measurement of tear production without clinical signs is not diagnostic of KCS

28 Infectious Bovine Keratoconjunctivitis
“Pink Eye” in cattle Highly Infectious, highly contagious Pathogen is the bacteria Moraxella bovis UV exposure and dust irritants can lead to infection Transmitted by face flies Tx: antibiotics, fly control, reduce dust Nictitating membrane or eyelids may be temporarily sewn over the eye in cases of severe corneal ulceration

29 Infectious Bovine Keratoconjunctivitis

30 The Lens Classification of cataracts: Congenital – present at birth
Juvenile – occurs in young dogs. Usually hereditary Diabetic – related to abnormal glucose metabolism Senile – due to aging Secondary to PRA, diabetes, or uveitis Traumatic – secondary to injury

31 The Lens

32 The Lens Luxated Lens The suspensory ligaments that attach lens to the ciliary break free

33 The Retina and Optic Nerve
Retinal Hemorrage 

34 Open-Angle Glaucoma In open-angle glaucoma, the drainage canals themselves are blocked, but the space between the iris and the canals are open

35 Closed-Angle Glaucoma
In closed-angle glaucoma, the opening to the drainage canals are blocked by another structure, the angle between iris and cornea is closed

36 Tonometry Procedure: Apply topical anesthetic to eye, one drop per eye, repeat 2 to 3 times in 3-5 minute intervals Calibrate your tonometer Elevate patient’s head vertically Rest the base of the tonometer on the center of the eye and let it bear the full weight on the cornea Take a reading off the scale, then remove the tonometer Take 3 to 5 readings from an eye, and average your readings

37 Tonometry For the Schiotz tonometer, the relationship between the IOP and the reading is inverse: the lower the reading, the higher the pressure Normal is 3.5 to 6.5 (using the standard 5.5g weight) If the reading is below 3.5, then additional weight is needed Actual (converted) IOP normals: Dog: 12.2 – 25 mmHg Cat: 10 – 25 mmHg


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