Basic ophthalmic diagnostics and techniques including dos and don'ts (Proceedings)

A. History

The importance of a reliable and accurate history that is relevant to the presentation at your examination-can not be overemphasized. As would be the case with any existing systemic condition, it is especially important to determine if there is a current regimen of medications that are being administered, as directed by a previous veterinarian, of which the owner may be hesitant to mention in fear of concern that you may ask why they did not come to you first for dx and tx. This is especially important when assessing such conditions such as miotic and mydriatic pupils-since the #1 cause of both is drug-induced. Additionally, it is also important to be aware of preexisting conditions and current therapy to avoid prescribing any future medication(s) that could cause serious systemic side-effects.

B. Examination

Ocular examination should be performed prior to a rigorous physical exam to avoid effects of stress changes on ocular features. Attempt to have the patient relaxed on the examination table before your hands-on evaluation. Initially look at facial and ocular features from a distance-to more accurately assess unstimulated features. Attempt to avoid using chemical restraint (if safely possible) or rigorous manual restraint-especially in the cervical region. Chemical restraint affects Schirmer Tear Test (STT) readings, intraocular pressure (IOP) measurements and may cause undesirable elevation of the third eyelid. In some cases, pupillary light responses and diameter may also be affected. Aggressive manual restraint around the neck or eyelids can result in dramatic increased IOP readings.

Basic instruments and supplies required: (an ocular examination should be performed in a darkened room to enhance subtle contrasts of extra- and intraocular structures)

Designated ophthalmic examination sheet-preferably 1 page only and ample diagrams

Light source-preferably halogen

Ocular magnifying loupe- 2 ½ x works best---mag. a must, especially for the over 40 group

Schirmer Tear Test (STT) strips

Fluorescein test strips

Eyewash and cotton balls

Topical anesthetic –Proparacaine

Tonometer-preferably TonoPen® or TonoVet ®

Mydriatic agent-Tropicamide

Direct ophthalmoscope (slit beam)-preferably a condensing lens for more panoramic image

Tissue forceps

Lacrimal cannula-preferably 2 sizes (22 to 25 gauge) (low priority)

± Blunt spatula, glass slides and fixative (gram stain), sterile culturettes←(low priority)

Eye model for explanation purposes

Examination Rules of Thumb

• Always perform diagnostic exam in the same order each time

History→PLR's→STT→ Culture (rare)→Fluor. stain→Top. Anesth.→IOP→Dilate

• Always examine the adnexa and eye in the same order each time (front to back)

Symmetry→Eyelids→Conjunctiva→Cornea/Sclera→Anterior chamber→Iris→Lens→

Vitreous→Retina

C. Dos & Don'ts

• Wipe out mucus with damp cotton before taking Schirmer tear test measurements

• Take culture of cornea before applying fluoroscein dye or proparacaine-bacteriocidal

• If suspecting a blocked puncta, apply fluor. stain liberally and hold nose down for 2 minutes before attempting to flush ducts. Not necessary to flush if fluor. stain is present in nostril(s)

• Use only sterile fluor. strips as Pseudomonas spp grows readily in stored fluor. solutions

• Evaluate degree of entropion both before and after applying topical proparaciane before sx

• Take intraocular pressures before applying mydriatic agent to ↓ chance of inducing glaucoma- especially in old cats

• TonoPen and TonoVet are becoming far more commonly used than traditional Schiotz tonometer but even these instruments require good technique to ensure accuracy

• Avoid dilating an eye with a luxated lens or known glaucoma

• Avoid rigorous manual manipulation of opening eyelids or around the neck while taking IOP to prevent falsely increased measurements

• A cataractous lens does NOT block light to the retina-a fixed & dilated iris is due to something else!

• The longer you wait to have a cataract removed the greater the chance for post-op complications. We DON'T want them "ripe"!

• REMEMBER!-The vast majority of eyes of dogs with muco- to mucopurulent discharge are 2° to inflammation (ex. dry eye-antibiotics not necessary) NOT infection and serous discharge in eyes of cats are due to herpes virus or chlamydia/mycoplasma NOT allergies- don't use topical steroids alone in cats unless you are sure it is not infectious

• Avoid recommending frequent topical eyewash rinsing for KCS as this removes beneficial oil secretions

• Use atropine ONLY if necessary and for shortest period of time possible and only if pain and miosis is evident. Use ointment vs drops in cats (short N L duct to tongue-bitter)

• NEVER prescribe topical anesthetic therapy for corneal pain

• There is NO medical reason to ever prescribe more than 1 drop at a time on the eye

• Antimicrobial and anti-inflammatory agents should not be prescribed for use "every now and then"

• If you manually epilate a distichia-it WILL grow back within 30 days and may be stiffer

• Third eyelid flaps are rarely used anymore to expedite corneal ulcer healing-numerous better tx's—but you must determine underlying etiology

• Chemical cauterization of corneal ulcers is seldom of value

• Debride and grid indolent corneal ulcers only—NEVER deeper ulcers

• It is generally recommended to not perform grid keratotomies in cats due to the potential to "inoculate" the stroma with herpes virus

• Avoid using topical gentocin to treat indolent corneal ulcers-may be epithelial toxic

• In cats, a darkly "pigmented" lesion on the cornea is a sequestrum and a white surface infiltrate is eosinophilic keratitis—concurrent herpes virus infection a possibility

• Use a condensing lens (2.2?) and halogen light source to view fundus instead of a direct ophthalmoscope-if possible- for better panoramic visualization-except in horses

• If retina is detached in a dog→take body temp.(fungal), palpate lymphnodes and CBC (lymphsarcoma), measure blood pressure (hypertension), other

• If retina is detached in a cat→ measure blood pressure (hypertension) , other

• If retinal hemorrhages are noted in a dog→measure blood pressure (hypertension), consider tick-borne disease, other

• If retinal hemorrhage is noted in a cat→ measure blood pressure (hypertension), other

• If hypopyon in a cat is noted→think FIP ± FIV, if KP's are noted→think Toxo, others

• If you want to treat intraocular inflammation→use Pred acetate or Dex phosphate—NOT betamethasone or hydrocortisone

• If you want to treat intraocular infection→use a fluoroquinolone—NOT triple antibiotic