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A technician's role in the ophthalmic examination (Proceedings)
What makes up the eye?
What makes up the eye?
• Adnexa (lids), Precorneal Tear Film, Cornea, Anterior chamber, Iris, Lens, Vitreous, Fundus
• Protect the eye
• Provide part of and spreads the tear film
• Regulate the amount of light that enters the eye
• Clear foreign material
• 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
• 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
• Third eyelid
• 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
• Fluid filled space between the cornea and iris
• Can fill with pus, blood, fat, protein, cells, or tumor
• Produced by glands in the ciliary body
• Provides nutrition and oxygen to the lens and cornea
• Provides the fluid support for the eye (IOP)
• "color" of the eye
• The color in dogs is simply different amounts of pigment cells-not different pigments
• 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
• 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
• Jello-like material that fills the back of the eye
• Holds the retina in place against the back of the eye
• 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
• What does your doctor need to know?
• Signalment, Age, Breed, Sex, Weight, Indoor/outdoor, Other health issues, Known trauma, Other meds
• Glaucoma in Cockers, Bassets
• KCS in Cockers, Bulldogs, Pugs, Lhasas, Shih Tzu
• Retinal degeneration in Poodles, Labs
• Indolent corneal ulcerations in Boxers, Retrievers
• 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?
• Color? Character? Constant?
• Squinting, Rubbing, Lethargic
• Color of the eye: Red, Green/orange, Cloudy/white
• 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!
• Gather equipment and proceed to a low lit area
• Bright light source
• Schirmer tear strips
• Fluorescein stain
• 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.
• 15-25 mm = normal
• 10-15 mm = suspect
• <10 mm = too dry
• Ask your doctor if culture is a possibility, Acquire prior to putting any drops in the eye
• Can culture: Cornea, Discharge, Lower conjunctival fornix
• Stains exposed stroma
• Will not stain the intact corneal epithelium
• Stains "sick" epithelial cells, Shows unhealthy tear film, Pathognomonic staining of Herpes virus "dendritic ulcers"
• Wash eye well first, Sample the site affected
• 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
• 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