A technician's role in the ophthalmic examination (Proceedings)

Article

What makes up the eye?

What makes up the eye?

     • Adnexa (lids), Precorneal Tear Film, Cornea, Anterior chamber, Iris, Lens, Vitreous, Fundus

Eyelids

     • Protect the eye

     • Provide part of and spreads the tear film

     • Regulate the amount of light that enters the eye

     • Clear foreign material

Third eyelid

     • Protects the cornea by removing foreign material

     • Contains the gland of the third eyelid

     • Helps to spread the tear film

     • Only moves passively in the dog

     • Can move actively in the cat

Tear film

     • Outer lipid layer created by the meibomian glands

     • Middle aqueous layer created by the lacrimal gland (65%) and gland of third eyelid (35%)

     • Inner mucin layer created by the coblet cells of conjunctiva

Conjunctiva:

     • Palpebral

     • Bulbar

     • Third eyelid

Cornea

     • More than just a windshield!

     • Accounts for 70% of the focusing power of the dog and cat

     • Only 0.5 mm thick

     • Layers: Epithelium, Stroma, Endothelium and Descetmet's membrane

Anterior chamber

     • Fluid filled space between the cornea and iris

     • Can fill with pus, blood, fat, protein, cells, or tumor

Aqueous humor

     • Produced by glands in the ciliary body

     • Provides nutrition and oxygen to the lens and cornea

     • Provides the fluid support for the eye (IOP)

Iris

     • "color" of the eye

     • The color in dogs is simply different amounts of pigment cells-not different pigments

Pupil

     • Empty space in the center of iris

     • Can be different shapes

     • Controls amount of light entering the eye

     • Shape: Dog – circle, Cat - vertical oval, Horse - horizontal oval

Lens

     • Behind the iris

     • 30% of focus power in the eye

     • Lens is where cataracts occur

     • The lens is anchored by the zonules that extend to the lens from the ciliary body

     • Zonules pull on lens to change its shape in accomodation

Vitreous

     • Jello-like material that fills the back of the eye

     • Holds the retina in place against the back of the eye

Retina

     • The "film" in the eye

     • 10 cell layers that transmit images to the optic nerve and then to the brain

     • Dogs and cats have a tapetum

     • No tapetum: Human and pigs

     • Tapetum Fibrosum: Horses and cows

     • Tapetum Cellulosum: Dogs and cats

History

     • What does your doctor need to know?

     • Signalment, Age, Breed, Sex, Weight, Indoor/outdoor, Other health issues, Known trauma, Other meds

Signalment:

     • Glaucoma in Cockers, Bassets

     • KCS in Cockers, Bulldogs, Pugs, Lhasas, Shih Tzu

     • Retinal degeneration in Poodles, Labs

     • Indolent corneal ulcerations in Boxers, Retrievers

History

     • What did you notice first? How long has the problem been going on? What treatment have you been giving if any? When did the treatment start?

Discharge

     • Color? Character? Constant?

Pain

     • Squinting, Rubbing, Lethargic

     • Color of the eye: Red, Green/orange, Cloudy/white

Vision problems

     • How well can they see? Is the vision different in dark vs. light? Are they bumping into things? If loss: sudden or gradual? Any other systemic problems?

Set your doctor up for success

     • Quiet dark room, Comfortable exam space, Stool or chair, You the technician!

Equipment

     • Gather equipment and proceed to a low lit area

     • Bright light source

     • Schirmer tear strips

     • Fluorescein stain

     • Proparacaine

     • Tono-Pen/Tono-Vet

     • Head loops

     • Direct ophthalmoscope or lens

Ophthalmic examination tests

3 Rules in Order of Testing

     • Schirmer tear test is ALWAYS first!!!!!!

     • Don't do ANY other tests before STT!!

     • Don't forget the STT at the beginning!!!!

Schirmer tear test

     • 1 minute

     • Insert notch between the lower eyelid and cornea

     • Performing: Do not touch the notched end with your fingers. If you like to fold them, do it PRIOR to removing from the plastic package. Always perform test on BOTH eyes.

Dog

     • 15-25 mm = normal

     • 10-15 mm = suspect

     • <10 mm = too dry

Culture

     • Ask your doctor if culture is a possibility, Acquire prior to putting any drops in the eye

     • Can culture: Cornea, Discharge, Lower conjunctival fornix

Fluorescein stain

     • Stains exposed stroma

     • Will not stain the intact corneal epithelium

Rose bengal

     • Stains "sick" epithelial cells, Shows unhealthy tear film, Pathognomonic staining of Herpes virus "dendritic ulcers"

Cytology

     • Wash eye well first, Sample the site affected

Intraocular pressure

     • Tonopen: Applanation tonometry

     • TonoVet: Rebound Tonometer

     • Schiotz: Indentation tonometry

     • Normal IOP: 15-25mmHg

     • Low= uveitis

     • High= glaucoma

Indirect biomicroscopy for fundic examination

     • Large field of view

     • 3D picture with head loops

     • How to : Transilluminator and lens, Hold lens close to the patient's eye, Hold transilluminator next to your eye

Direct biomicroscopy

     • Small view but very magnified

Sensitivity to light

     • Dogs and cats have more rods than cones. Their tapetum reflects light

     • Minimum threshold for light: Cats- 6 times lower than humans, Dogs – somewhere in between

Newsletter

From exam room tips to practice management insights, get trusted veterinary news delivered straight to your inbox—subscribe to dvm360.

Recent Videos
Melissa Evans, CVT, LVT, VTS (ECC)
© 2025 MJH Life Sciences

All rights reserved.