Common eye diseases for veterinary technicians (Proceedings)

Quick Eye Anatomy Review

1. Eyelids

a. Protection

b. Tear distribution

c. Light limitation

2. Conjunctiva

a. Mucus secretion

b. Lymph tissue

3. Tear film

a. Corneal nutrition

b. Lubrication

c. Defense system

4. Cornea

a. Focusing apparatus

b. Anterior wall of eye

5. Anterior chamber

a. Contains and drains aqueous

6. Aqueous

a. Fluid produced by the ciliary body

b. Maintains intraocular pressure and provides nutrition to intraocular structures

7. Iris/Pupil

a. Vascular tissue

b. Regulates light into the eye

8. Lens

a. Focusing apparatus of the eye

9. Vitreous

a. Clear, gelatinous structure

10. Retina

a. 10 cell layers of conduction tissue to transmit light images to the brain

11. Optic Nerve

a. An extension of the brain, allows transmission of images to the brain

Common Ocular Diseases

1. Keratoconjunctivitis sicca (KCS, dry eye)

a. Poor tear production or quality

b. Breed predisposition: shi tzu, cocker spaniel, pug, boston terrier, westie, bulldog etc.

c. Normal tear production is 15-25 mm in 60 seconds

d. Permanent disease, controllable, but not curable—medications must be used lifelong!!

e. Tear stimulant therapy: Tacrolimus or cyclosporine

f. Anti-inflammatory therapy: neopolydex

g. Tear substitutes: Genteal gel

h. Can be blinding if left untreated, or result in perforating ulcers

2. Corneal erosions or ulcers

a. Wound of varying depth in the cornea, can be superficial or deep

b. Most corneal nerves are superficial, so these can be the most uncomfortable

c. The underlying cause needs to be addressed in order for the ulcer to heal

d. Surgical options for patients over 50% depth

e. E-collar is important!

3. Glaucoma

a. Elevation in intraocular pressure (15-25 mmHg is normal)

b. Breed predisposition: cocker spaniel, basset hound, Alaskan breeds, chow chow, shar pei, shi tzu, boston terrier, etc

c. Sink analogy: faucets produce fluid in the eye and it is the drain that clogs.

d. If a primary glaucoma it will ALWAYS affect both eyes eventually

e. With preventative treatment in the unaffected eye you can delay the onset of glaucoma 4-fold

f. Medications are permanent and are aimed at decreasing fluid production in the eye.

g. Discomfort in the form of headaches is present over an IOP of 40 mmHg.

h. Surgical correction to alleviate discomfort is recommended: enucleation, chemical ablation, cyclocryosurgery, intrascleral prosthesis

i. Laser surgery for the visual eye may soon be a good option

4. Cataract

a. Can be young (breed related) or old (age or breed related)

b. Diabetes causes rapidly forming cataracts, about 80% of diabetic patients will develop cataracts in the first year after diagnosis

c. Lens induced uveitis is always present and must be treated with topical anti-inflammatories

d. Surgical success is high (90-95%) and an IOL is placed

5. Uveitis

a. Inflammation inside the eye, most often caused by a systemic disease

b. Workup includes CBC/Chem, chest radiographs, various titers.

c. Therapy involves both treating the underlying systemic problem and treating the symptomatic inflammation

6. Entropion

a. Mostly a young dog problem with an abnormally long and loose eyelid that allows the hairs on the outside of the eyelid to rub on the cornea.

b. Some dogs will outgrow the problem, but final conformation is present at 10-12 months

c. Temporary correction is needed before that time (Staple or suture blepharoplasty)

d. May need several temporary procedures at the puppy grows until it reaches adult conformation. Important not to correct permanently to early.

e. Surgical correction needed if permanent problem. Shorten eyelid and roll it out (Hotz-celsus procedure)

7. Prolapsed gland of the third eyelid

a. Young dogs, breed related (cocker spaniel, bulldog, cockapoo, etc.)

b. Owners always alarmed, but not an ER and not painful for the dog

c. Important to correct, NOT remove!

d. This gland produces about 35% of the total aqueous tear film

e. Create a pocket to replace permanently

8. Sequestrum

a. Cats with a "black spot" on the cornea

b. Usually flatter faced cats

c. Results from chronic irritation (poor blinking, poor tear film, repeatitive erosions, hair from nasal fold rubbing)

d. Surgical removal is the best choice

e. Genteal longterm to prevent recurrence

9. Feline conjunctivitis

a. Feline herpes virus acquired as a kitten usually

b. Lives dormantly in corneal nerves for many years

c. Can cause flare-ups of conjunctivitis commonly

d. Similar to human cold sores

e. Best defense is client education

i. Chronic problem

ii. Stress induced

iii. Genteal and L-lysine to prevent outbreaks

f. Topical and oral antiviral medications (Trifluridine)