Ophthalmology intro and adnexa Flashcards
What direct opthalmoscope settings do we use to look at tapetal reflex
0 dioptres
Go from about 2 foot away
What might decrease or increase the tapetal reflex
Decrease: cataracts
Increase: retinal atrophy
How to differentiate nuclear sclerosis from true cataract
True cataract does obscure the tapetal reflex
Nuclear sclerosis doesn’t obscure tapetal reflex (=pseudoopacity)
How to look at the posterior section of the eye with direct opthalmoloscope
Still use 0 dioptres
Go 2-3cm away from eye for highly magnified view of fungus
What is myopia and hypermetropia and how do we compensate for this when we want to look at the fundus
Myopia = short sightedness
Hypermetropia = long sightedness
Compensate via adjusting dioptres setting
What direct ophthalmoloscope settings do we use to look at anterior segment of the eye
10 dioptres
What shape do the anterior vs posterior suture lines of the lens make
Anterior = Y shape
Posterior = inverse Y
What setting do we use to look at cornea and adnexa on direct ophthalmoscopy
20-30 dioptres
Properties of indirect ophthalmoscopy
Less magnified
Inverted, virtual image
Good for scanning retinas
What is gonioscopy and what is it useful in identifying
= using contact lens for visualising the iridocorneal angle
Can be diagnostic in glaucoma
What is a normal Schirmer tear test result and what is clinical dry eye
Normal = 10-20mm/min
Dry eye = 5mm/min
How does indentation tonometry work
Pushes probe on surface of eye and sees how much it indents; more indentation = lower intraocular pressure
How does applanation tonometry work e.g tonopen
How much pressure does it take to flatten middle 0.5cm of cornea; less pressure means lower intraocular pressure
How does rebound tonometry work e.g tonovet
Speen of rebound of probe going onto eye
What is normal intraocular pressure
- What in glaucoma
- What in inflammation
Normal = 15-22mmHg
Glaucoma = 30-60mmHg
Inflammation = 10mmHg
Why do we flush eye after putting in Fluorescein isothiocyanate stain
Because re-epithelialised ulcer will have dip in the middle that dye can pool in but not a true ulcer
What is rose bengal dye used for
Adheres to areas deficient in mucus e.g in dry eye
Where embryologically do the anterior structures in thee ey come from
Neural crest and mesenchyma
Where do the cornea and lens come from embryologically
From ectoderman placode
WHere do retina and ciliary body come from embryologically
optic vesicle; outpouching of midbrain
Glands in the eyelid/eyelid margin and what do they secrete
Zeiss, Moll, Meibomian
Zeiss secrete aqueous secretion
Moll secrete sebaceous
Meibomian glands made lipid component of tear film
Nerve supply to levator palpebrarum and implications of this
Trigeminal sympathetic supply; so in Horner’s syndrome get upper eyelid drooping (ptosis)
What does orbicularis oculi cause
Closing of the eyelid
Which species often have coloboma of the eyelid and where is it
Cats and snowleopards
Found laterally on the upper eyelid
- May also have optic disc coloboma
4 causes of entropion
1) Tarsal plate defect
2) Excess facial skin
3) Dropping upper lid
4) diamond eye
What is the most common cause of entropion and how do we treat it
Tarsal plate defect
Seen in retrievers, cocker spaniels
Use Hotz-celcus procedure to remove an oval of skin
How can we deal with entropion due to excess facial skin in puppies
Use temporary vertical mattress sutures to evert the eye; should resolve as animal grows
How do deal with entropion caused by drooping upper lid e.g in Cocker spaniels
Do a stades procedure; remove lid and cilia
What is a stades procedure
Make incision at lid margin and remove skin and lashes; then leave open to granulate
Used to correct eyelid drooping causing entropion
How does the Hotz-celcus procedure work
Remove an elipse of tissue about 1mm from eyelid edge and suture up
- Used to correct entropion due to tarsal plate defect
Or can be used to correct diamond eye
How do we estimate amount of skin to remove in a Hotz-celcus procedure
Pinch skin and outturn eyelid in an unsedated patient
Which breeds is diamond eye part of the breed standard for
Bloodhound, St Bernard, Clumber spaniel
What is diamond eye
Ectropion + entropion on the sloping lid edges
What is a Wyman lateral canthoplasty
Involves suturing flaps of orbicularis oculi to correct diamond eye
What is a potential sequelae to ectropion
Exposure keratitis
How to correct ectropion
Wedge resection of excess lid
Or Khunt-Szymanowski procedure to involve lid splitting
What type of tumours are commonly seen on dog eyelids
Benign
- Sebaceous adenoma, squamous papilloma, benign melanome, histocytoma
What type of tumours are commonly seen on cat eyelids
Malignant; squamous cell carcomas
What is distichiasis
Where an extra set of lid hairs comes from the Meibomian gland orifices at lid edge and cause ocular irritation
Why should we not attempt to remove distichiasis hairs via sharp knife surgery on the lid margin itself
Get scarring of area which leads to corneal irritation and pathology
What is trichiasis and what breed anatomy can lead to this
= where hairs growing in normal position are placed abnormally onto the cornea and cause irritation
- E.g dropping upper lid in old cockers (entropion)
- E.g nasal fold hairs in Pekinese etc
- E.g Ingrowing medial canthus hairs in brachycephalics
What is chalazion
Lump on the eyelid due to blockage of the meibomiam gland (can occur due to meibomitis)
What is juvenile cellulitis
where the whole lid becomes swollen due to an allergic reaction to normal staphylococci
- Need steroids +/- antibiotics to deal with it
What type of suture should we use to repair lid trauma
6/0 vicryl
Figure of 8 knots
Movement of the third eyelid
Moves across the eye when the globe is retracted by retractor bulbi
Protrudes both when eye retracted or protruding
Things that might cause third eyelid protrusion
- Retrobulbar space occupying lesion
- Reduced retrobulbar muscle contraction after tranquilisation/tetanus/torovirus
- Reduced orbital contents e.g dehydration, microphthalmia
- enopththalmos from trauma, Horner’s syndrome, ocular pain
Which breeds do we tend to see cherry eye and how do we correct it
Brachycephalics and Mastiffs
- Use pocket technique to correct it
- Could remove gland but bad idea since it controbutes 30% of tear film so risk of dry eye
How are tears removed/flow out
Evaporation
Drainage through nasolacrimal system
Flow aided by orbicularis oculi squeezing on canailculi when blinking
What is keratoconjunctivitis sicca
Dry eye
- insufficient tear production
What would be an indication that KCS is due to a neurological defect
Also seeing a dry nose
What can cause KCS
Neurological issues; ophthalmic branch of trigeminal or facial nerve
Iatrogenically from sulphonamides
Autoimmune; lymphocytic infiltrate into glands
Complications that can arise from parotid duct transposition
Overproduction of tears
Duct can siccatrise and stop producing saliva
Treatment for KCS
Cyclosporine (optimmun 0.2%), artificial tears, protecting gel, pilocarpine drops
What would dogs with deficienct in the mucus component of the tear film present with and what is the cause
Chronic keratitis but NORMAL schirmer tear test
Due to infection or inflammation of the Meibomian gland; so get lipid deficiency and unstable tear film
What congenital defect can cause insufficient tear drainage
Micropunctun or imperforate punctum
WHy might we give adrenaline during surgery for imperforate puncta
To stop haemorrhage which could lead to fibrosis and scarring
What is epiphora
Insufficient tear drainage
What is dacryocystitis
Persistent mucopurulent discharge due to blockage of nasolacrimal duct with inflammation/infection
Which breed has an issue with functional defects in an otherwise patent nasolacrimal duct
Poodles
- See as brown facial tear staining
What procedure to do with globe prolapse
Canthotomy; cut lateral canthus and lift eyelids
If there is an infectious cause of exophthalmos what symptoms will we see
Pain opening mouth
Pus coming out behing top last molar
