Veterinary ophthalmology for the technician (Proceedings)

• Anatomy

• Medical and Ophthalmic History

      o Signalment

      o Primary complaint

      o Concurrent disease

      o General heath questions (travel, indoor/outdoor, changes in weight, eating, drinking, urination)

      o Vision (night vs. day, vision in unfamiliar environment)

      o Duration of problem

      o Trauma

      o Redness and characteristic of discharge

      o Swelling

      o Color change

      o Pain (rubbing, tearing, squinting, painful to touch, reluctance to open mouth or eat, photophobia, general malaise, or depression)

• What to look for as a Technician

      o Red eye, Cloudy cornea, Mucoid discharge (grey or green), Blepharospasms , Swelling on or around eyelids, Color change to eye, Normal pupil shape and size

• What to do and what not to do?

      o Don't clean discharge,

      o Measure tears prior to putting stain or proparacaine in the eye

      o If cornea has a deep ulcer- Handle eye very gently , Forgo diagnostics (eye tests as well as rectal temperature)

      o Gentle restraint (excessive neck pressure and struggling can cause a fragile eye to worsen)

      o Dogs and cats can become very aggressive if their eye hurts, so be cautious when touching their face

• Diagnostic Tests

      o Tonometry

      o Schirmer Tear Test

          ■ To measure tears for dry eye

          ■ Normal test is 15-20 mm/minute

      o What falsely alters a normal tear test?

          ■ Any drops placed in eye prior to tear test

          ■ Atropine usage, topically or injectable will "dry" up tears

          ■ Benadryl and other anti-histamines will decrease tear production

          ■ Sedation/Anesthesia will lower tear production

      o Fluorescein Stain

          ■ Identify corneal ulceration

          ■ Patency of nasal-lacrimal duct

      o Tonometry

          ■ Tonometry is measuring of the intraocular pressure

          ■ Glaucoma is a high pressure in the eye and is best detected by measuring IOP

          ■ Normal dogs and cats- 13-21mmHg

          ■ Proper restraint for accurate IOP measurement

               • Neck or jugular pressure will cause a false elevation

               • Pulling back on the eyelids will place pressure on the globe

• Basic Exam Tools

      o Transilluminator and direct ophthalmascope

      o Head Loupes (3X-7X magnification)

• Most common ocular diseases

      o Corneal Ulcers

          ■ Superficial/simple

          ■ Infected/malacic

          ■ Desmetocoele

          ■ Rupture

          ■ Puncture/laceration

          ■ Indolent- age related

      o Keratoconjunctivitis Sicca (Dry Eye)

          ■ Causes of Dry Eye

               • Immunogenic, Congenital, Neurogenic , Drug/toxic induced, Infectious, Removal of gland of third eyelid, Uncorrected prolapsed gland of third eyelid, Irradiation of the area, Metabolic diseases

          ■ Clinical Symptoms of KCS

                    • Extremely hyperemic conjunctiva

                    • Ocular discharge is persistent: Thick, yellow, ropey

                    • Keratitis

      o Cataracts

          ■ Why do cataracts occur

                    • Diabetes

                    • Juvenile/ hereditary

                    • Senile

                    • Trauma

          ■ Cataract Surgery (Phacoemulsification)- very successful

      o Uveitis

          ■ Inflammation of the uveal track- iris and choroid

          ■ Clinical Signs

               • Aqueous flare

               • Corneal Edema

               • Keratic Precipitates

               • Miosis

               • Conjunctival hyperemia

               • Hypopyon

               • Hyphema

               • Iris swelling

               • Iris hyperpigmentation (chronic change)

               • Photophobia

          ■ Causes

               • Infectious: 17.6% (algal, bacterial, fungal, protozoal, viral)

               • Immune-mediated/ Idiopathic: 57.8%

               • Metabolic (i.e., lipid aqueous)

               • Neoplasia: 24.5%

               • Miscellaneous (i.e., traumatic)

      o Glaucoma

          ■ Hallmark symptom is elevated intraocular pressure

          ■ Can be very painful, referred pain as migraines and or nausea/vomiting

          ■ Very rapidly blinding

          ■ 2 causes: Primary and Secondary

          ■ Early symptoms are easily missed and can be devastating for vision

          ■ Symptoms of Glaucoma

               • Lethargy

               • Blepharospasms/pain

               • Episcleral congestion

               • Corneal edema

               • Fixed and dilated pupil

               • +/- menace response

               • Mild to moderate aqueous flare

               • Optic n. hyperemia and swelling

      o Retinal Degeneration

          ■ Progressive Retinal Atrophy (PRA)

               • Early symptoms are impaired vision in dim light and darkness

               • Sluggish pupillary light reflex

               • Resting pupillary opening is large

               • Owner sees green reflex (tapetal hyper-reflectivity from thinning retina)

               • Thin Retinal blood vessels

               • Pale optic nerve head

               • Secondary cataracts in late stages

               • Breed predisposition- Labrador Retriever, Cocker Spaniel, Poodle, Portuguese Water Dog, Dachshund, Iris Setter, among others

          ■ Sudden Acquired Retinal Degeneration

               • Unknown cause of sudden vision loss

               • Rapid onset 1-3 weeks

               • Middle age to older dogs

               • Dachshund and Min. Schnauzer most common, but any breed can get it

               • Vision loss is usually accompanied by increased appetite, weight gain, increased water consumption and urination

               • Retinal exam is initially normal

               • Diagnosed via Electroretinogram (ERG)

References:

Essentials of Veterinary Ophthalmology by KN Gelatt; Fundamentals of Veterinary Ophthalmology by Slatter; Small Animal Ophthalmic surgery by KN Gelatt