Ophthalmology

ophthalmology

right eye

left eye

both eyes

ophthalmic solution (drops)

ophthalmic ointment

one drop

multiple drops

lid

lid

corners

tear system

conjunctiva

cornea

iris

uvea = iris, ciliary body, choroid

American college of Veterinary (specialty x)

Diplomate of the American College of (specialty x) = board certified specialist

• fibrous tunic (outer) - cornea and sclera
• vascular tunic (middle) - uvea - iris, ciliary body, choroid (front to back)
• neuroretinal tunic (inner) - retina

• palpebrae, tarsae
• skin and hair, muscles, tarsal plate, meibomian glands, cilia/lashes above margin, lined posteriorly by palpebral conjunctiva
• medial/lateral canthus
• protect from external environment, distribute tear film, contribute to oily layer, open at 3-15 days old.

squinting

provides oily layer to tear film, part of eyelid

• third eyelid
• medial canthus. Conjunctiva covering T-shaped cartilage with accessory lacrimal gland at base.  Passively elevates when eye recessed, elevated by pressing on dorsolateral aspect of globe.  
• protection, aqueous tear film from lacrimal gland

part of nictitans, provides aqueous layer of tear film

• three components: mucus from goblet cells of conjunctiva, aqueous from lacrimal glands, oily from meibomian glands.  Mostly aqueous.  
• flushes physical contaminants from ocular surface
• provides for optical clarity of cornea
• contains enzymes, immunoglobulins for protection
• O2 to cornea
• drains into nasolacrimal, onto face
• dries at medial canthus as rust-colored discharge

• drainage of tears.  
• Upper and lower punctum at medial canthus, connect to canaliculi, meet to form lacrimal sac to nasolacrimal duct to nose/pharynx
• blinking pushes tears toward puncta
• overflow causes tear stains, skin issues

• mucosal membrane covering the sclera and inner eyelids, composed of palpebral, bulbar, fornix, nictitans portions, goblet cells.  Highly vascular
• flexible and elastic so globe moves
• immunologically functional mucous membrane
• goblet cells contribute mucus layer to tear film

• for secretion of tears
• 2 glands, orbital (most aqueous tears) and gland of third eyelid
• secrete aqueous portion of tears

tearing

• clear windshield of eye
• 4 layers: epithelium (several cell layers), stroma (thickest, collagen), Descemet's membrane (acellular, very thin basement), endothelium (1 cell layer thick).  
• 1mm thick in c/d
• cornea clear due to arrangement of collagen layers, clarity due to dehydration by corneal epithelium
• nerves in stroma bare and sensitive
• normally avascular
• nutrition from tear film

• chamber delineated by cornea and iris/pupil/iridocorneal angle/lens
• filled with aqueous humor (saline-like fluid made in posterior chamber, clear)
• aqueous humor flows from ciliary body in posterior chamber through pupil to anterior chamber, then drains out iridocorneal angle

• fibrous white portion of eye wall, continuous with cornea.  Relatively spherical in d/c
• has attachments to extraocular mm
• somewhat rigid and helps give globe shape

anterior portion of uveal tract (middle of 3 layers of eyeball).  Vascular and pigmented.  colored portion of eye.

• hole in the iris, different shape for different species
• constricts and dilates using pupillar mm under autonomic control
• high vascularity supplies nutrients to adjacent portions of eye

irides of different colors, can be normal or abnormal, congenital or acquired

large, dilated pupil

small, constricted pupil

• middle portion of uveal tract, posterior continuation of iris.  Small ridge of circumferential tissue behind iris, arranged in finger-like ridges called ciliary processes.  Peripheral attachement for lens zonules (strings).  Ciliary muscle located outside ciliary body.
• mucle makes accommodation, changing lens focal point.  
• ciliary body makes aqueous humor.

thin clear acellular strings attaching circumferentially to lens equator

chamber delinated by back of iris and front of lens

changing focal point of the lens (near and far vision) by pulling or relaxing equator of lens

• lens capsule envelops lens fibers which are arranged to be optically calear.  Suspended in center of visual axis by zonules
• focuses incoming light via accommodation
• vascular, needs fluid for metabolism, clear when healthy (alive). 
• Always making new fibers, push toward center of lens. Makes center hard (nuclear sclerosis) but still clear

normal aging change, hardening of center of lens as fibers move to center.  Light still passes through, clear.

opacity of lens

• clear gel filling the back of the eye, composed of mostly water and collagen
• helps maintain eye shape and position of retina against choroid
• avascular, slow metabolism
• opacities (floaters)

• posterior portion of uveal tract behind ciliary body
• contains tapetum lucidum (better night vision)
• high vascularity (= nutrition for retina)
• pigmentation = "black box" = less light scattering and clearer vision

colored (yellow, green, orange) reflective surface on half back of eye, in choroid.  allows for improved night vision and "deer in the headlights" shine

• innermost light-sensitive layer of eye
• 10 histologic cellular layers
• has neurons that gather at back to form optic nerve
• photoreceptor cells turn light into electrical impulses, transmitted to brain with optic nerve
• rods for night, cones for day
• must be attached to choroid to be functional, atrophies if detached
• very sensitive to pressure, does not heal well.

back half of eye visualized when examining from the front of eye

• examination of the back half of the eye (ophthalmoscope or lenses and focal light)
• uses indirect or direct ophthalmoscopy.  Could use ocular ultrasound, electroretinogram

• protrusion of globe from orbit/socket
• trauma, HBC, dog fight, blow to head, excessive restraint
• replace or remove (eval whole pet and tx, replace eye if recent, 3 or less EOMm ruptured, optic nerve attached and globe in good shape. ASAP, don't refer.  
• remove otherwise.
• unlikely to save vision, guarded to save eye

• examination of the eyes from a distance using the reflection from the back of the eye.
• Highlights minor opacities in the clear ocular media

• menace: cover one eye, move hand towards other eye without touching hair or moving air.  Animal should blink unless very young
• pupillary light reflex (PLR): shine light into eye, note constriction.  Direct is when pupil that received light constricts, indirect other pupil constricts.  DOES NOT MEAN VISION IS INTACT
• palpebral reflex: touch medial or lateral canthus, eye should blink
• dazzle reflex: shine bright light in eye, should blink (+/- globe retraction or turning away)

• diagnostic test to measure quantitative tear production
• Fold strip at notch, place in lower eyelid pocket and keep for 60s.  Measure length of wetness
• blue dye with markings.  Remove mucus first without touching eye.  NO GOOD POST-TOPICAL
• normal >15mm/60s.  Low/KCS is <10, high >30

• test for corneal ulcers, nasolacrimal patency and corneal leakage
• 1-2drops saline on tip of strip, touch to bulbar conjunctiva, flush, examine with cobalt light or Wood's lamp
• 1 strip/P or /eye if infected.  No uptake for normal, ulcer takes stain (stroma hydrophilic).  If stain moves on eye, just mucus/hair. Descemetocele won't take stain.  
• Should appear at nostrils/throat, patent duct.  Not blocked if doesn't appear
• Leak in cornea shows stream of clear, WEAK CORNEA, WILL RUPTURE

• measurement of intraocular pressure (IOP), glaucoma test
• red eye, pain, dilated pupil, corneal edema, vision loss, globe enlargement indicators (Schiotz, tonoPen, TonoVet), normal <20mmHg.  25 borderline, >30mmHg high
• DIGITAL TONOMETRY NO GOOD

• glaucoma test
• assemble tonometer
• apply topical anesthesia to eye (proparacaine, tetracaine etc in fridge)
• confirm calibration on test block (reads 0)
• nose to ceiling
• footplate onto cornea until weight rests, VERTICAL, not on sclera or nictitating
• repeat, average, use chart to convert to meaningful number
• clean, disassemble
• NOT WITH ULCERATIONS, PERFORATION, RECENT SURGERY (use tonopen or tonovet)
• edema, poor position, anterior lens luxation make unreliable (use TonoPen)

• apply clean finger cot, calbrate (hold facing down, then up)
• topical anesthesia
• press button, double dashed lines
• tap cornea PERPENDICULARLY
• chirps with each reading, beeps final reading
• <5% variance okay
• best for corneal edema, anterior lens luxation, okay (ish) after sx, ulceration, perforation

• Press large button to turn on, set for species
• insert tip
• press button (00 = ready)
• hold tip away from cornea as far as end piece
• press button repeatedly for readings
• beeps for final reading
• okay for corneal ulceration, perforation, edema

• similar to fluorescein, vital dye that adheres to devitalized tissues
• good for cats to ID early herpes ulcers
• branching dendritic ulcers

casts a slit beam of light onto eye to magnify for viewer, detailed view and depth differentiation of front of eye

handheld lens and light source, image is upside down and backwards, see MUCH wider portion of fundus at one time, can stay away from P

uses ophthalmoscope, image upright but only small portion seen at one time, constant refocusing, must be close to P

images interior and retrobulbar anatomy, esp when back of eye can't be visualized directly

eval electrical impulses generated by functioning retina when stimulated by flashes of light

• prolapse of the gland of the third eyelid
• caused by weka attachments, breed predisposition.  Replace gland. Sometimes manual, usually surgery.  DON'T REMOVE

• loss of corneal epithelium
• trauma, infection, predisposition, KCS, poor health
• squinting, redness, rubbing, discharge, visible defect, photophobia
• treat primary problem, topical abx to prevent infection, secondary issues if present, NO STEROIDS, NO ANALGESIA, e-collar, sx (conjunctival graft, debridement, keratotomy)
• recheck 1-3 days

• dry eye
• caused by immune-mediated destruction of lacrimal gland, neuro, excision of third eyelid, drugs
• redness, sticky d/c, squinting, dull cornea, corneal disease
• tx with tear replacements, tear stimulants, ocular hygiene, secondary infection tx.  LIFELONG TX
• sx - parotid duct transposition

• inflammation of the conjunctiva
• caused by infection (herpes), allergy, trauma, inflammation
• redness, puffy conjunctiva and lids, watery/mucoid/mucopurulent ocular d/c. 
• tx primary problem (eye redness not primary conjuntivitis)
• topical abx/antiviral, systemic antiviral, topical inflammatories (MAYBE)

• inrolled eyelid margin, hairs rub on eye
• caused by anatomic/breed, squinting, corneal ulceration
• inrolled eyelid (1 to 4), squinting, tearing, rubbing, secondary corneal disease, often in young to young adult.  DIFFERENT that spastic entropion
• sx required

• increased intraocular pressure (IOP) and vision loss
• 1° caused by anatomic/breed, 2° caused by uveitis, lens luxation, iris adhesion, blood or tumor in eye etc.
• drainage of aqueous humor ceases but production continues, pressure causes pain and damages retina
• acute = cloudy eye, redness, dilated pupil, vision loss within hours
• chronic = enlarged globe, large pupil, blind eye
• IOP >25-30mmHg
• tx acute = ER!  topical +/- IV mannitol (dehydrant).  Oral and topical meds available.  Lensectomy if includes anterior lens luxation (terriers)
• shunting and cycloablation sx or salvage (prosthesis, enucleation)
• 2nd EYE ALWAYS AT RISK

• opacities within lens
• incipient, immature, mature (can't visualize), hypermature (lens shrinks).
• breed disposition, diabetes (75%), uveitis, lens trama, retinal disease
• you see white opacity in pupil, vision loss, NOT PAINFUL.  Not nuclear sclerosis (pearliness in >7yo)
• elective cataract sx for healthy eye (shatter lens with ultrasound, aspirate from eye, prosthetic)
• cataract may cause uveitis or glaucoma

• steroids: pink cap
• mydriatics: red cap

sx done under an operating microscope (light and magnification

betadine solution (NOT nolvasan), then rinse with saline

tubes

adjective

noun

loose on surface of eye

constant irritation, cornea heals down onto eyeball, becomes opaque

epithelium (surface), stroma (strength), descemets membrane (basement), endothelium (inner layer)

blood in anterior chamber of eye

pus in anterior chamber of eye

fusiform

abnormal iris adhesion.  Posterior (adhesion to lens) or anterior (adhesion to cornea)

abnormal shape of pupil

motheaten appearance, older dogs, hard to constrict pupil.

eyes point in different directions due to torn muscles

incomplete blinking

eyelid rolling out so palpebra exposed

caused by painful eye, P gives themselves entropion by squinting

ciliary body

• Position the animal so he can’t squirm backwards or resist with the front feet – use
• towel/blanket if needed
• Point the animals’ nose up to the ceiling
• Hold the upper lid open from the top of the head
• Let the drop fall from a distance
• Do not suck back material back into the bottle
• Hold the animal a moment to reduce the urge to rub or shake
• One drop only is usually necessary, but can give another if not sure it went in
• If give more than one drop, it’s usually not harmful, only wasteful
• Wash hands before and after

- ointments: Only a small amount of ointment is usually needed - 1⁄4 to 1/8 “ stripMake a pocket by pulling the lid away from the eye (upper or lower)Usually only have to barely squeeze the tube - let it come out on its ownWatch to make sure the ointment melts onto the eye - let the lids blinkHold the animal for a moment to reduce the urge to rub or shakeIf more ointment is used, it’s usually not harmful, only wastefulWash hands before and after- always wait at least 5 min between topicals given at the same time- give drops before ointments