module 11 Opthalmological emergencies Flashcards
Describe how to perform a complete ophthalmic assessment
The suggested order of eye examination of the dog and cat is as follows:
Gross examination
Vision testing
Neuro-ophthalmic evaluation
Adnexal and anterior segment examination
Schirmer tear test
Administration of topical anaesthetic
Tonometry
Collection of cytology sample (if required)
Fluorescein staining
Administration of mydriatic agent
Fundic examination
Additional tests
Discuss the ophthalmic assessment in terms of gross and specialised examination techniques
GROSS;
Looking for symmetry of the eyes:
Width of the palpebral fissure
Eyelid position
Pupil size/shape
Globe position
Evidence of pain?
Evidence of photophobia?
Is the blinking normal?
Ocular/discharge?
Palpation of the periorbital area – the bony and soft tissue structures to ensure symmetry **Not in cases of suspected fragile eye
Retropulsion of the globe
Finger placed over closed eyelid and apply pressure
Allows evaluation of the third eyelid
Also assess for presence of retrobulbar lesions (increased resistance)
** Not in cases of suspected fragile eye
SPECIALISED EXAMS;
i)ASSESS VISION
a)Menace response-checks entire pathway and is NOT a reflex, requires cognition also.Hand approaches without touching (and without creating a draught).
If no menace response, ddx false negative, facial nerve paralysis, vv young, altered mentation.
b)cotton ball drop test-best one to test in cats.
c) maze test-basically can they negotiate objects in a room.
ii)NEURO-OPTHALMIC ASSESMENT
a)Menace response
b)Dazzle reflex-this is a reflex, and does NOT assess vision. Tests the pathway b/n retina, optic nerve, chiasm,
optic tract, rostral colliculus, and facial nucleus and nerve.
A normal response is a partial blink in response to bright light being shone in eye. Present in youngs as soon as eyelids open.
c)Palpebral reflex-induce blink by touching eyelids. Medial canthus checks Opthalmic branch of Trigeminal n, and lateral canthus checks Maxillary br of Trigeminal n. Very important to check this if menace or dazzle absent.
d)Pupillary Light Response-is NOT a test of vision.Checks pathway between retina, optic nerve, chiasm,
optic tract, pretectal nucleus in the midbrain, oculomotor nerve, ciliary ganglion and iris sphincter muscle.
Absent PLR reflex in an eye that is visual indicates lesion either at the oculomotor nerve (innervates the iris) or the iris itself. Not uncommon in geriatrics because of iris atrophy.
d)Corneal reflex-touch cornea with wisp of cotton wool. Important to do in chronic keratitis or chronic corneal ulcerationetc, but DO NOT do if descemetocoele.
iii)ADNEXA AND ANTERIOR CHAMBER
iv)SCHIRMER
v)TOPICAL ANAESTHESIA
do not use ongoing as can create corneal ulceration.
vi)TONOMETRY-note might need pin horizontal to ground (at any rotation) to minimise error. Must check pressure before dilating a pupil as some glaucomas will dramatically worsen when dilate pupil.
vii)CYTOLOGY SAMPLES
viii)FLUORESCEIN
ix)MYDRIATIC AGENT eg tropicamide takes 30min to work and lasts up to 8 hours.
x)FUNDIC EXAM-darkened room.With dilated pupil.
a) Direct opthalmoscope has approx 10 x mag. use your left eye to examine patient’s left etc. need to be in very close to patient with face. at 20 diopter are in focus approx 20cm. Put your brow right up against browmark on opthalmoscope. At 0 or infinity, retina in focus. 10 diopter front of lens should be in focus and 8 diopters back of lens should be in focus.Gives great detail but not so good for getting the whole panaroma.
b) Use indirect opthalmoscopy eg headlamp or headvisor plus reading glasses if wish, direct light beam on patient’s eye and use a handheld lens up close and place in light beam in front of patient’s eye. your body is away from patient (at armslength). Adjust focus by moving lens closer and further slightly. Better for panaroma and for penetrating densities such as cataracts. To see upper patient eye, you move downwards and vice versa. Image is inverted ie see left and this=right etc.
xi)ADDITIONAL-eg slit lamp microspcopy is a way of judging how deep in eye defects are by presenting purkinje images which are the interfaces ie 1st line is corneal reflection, 2nd is inner surface of cornea, 3rd is anterior lens and 4th is posterior lens. Can do a cheapie version using the slit on direct opthalmoscope and a hand held lens and a head visor with 4x mag. Needs to be done in darked room as reflections interfere.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of CORNEAL ULCERATION/LACERATION
AETIOLOGY due to deficiencies of tear production, problems with lid closure (macropalpebral fissure, CN V issue, CN vii issue, eyelid deficits, eyelash issues eg entropion,disticchiasis etc, viruses such as canine/feline herpes,foreign body/trauma.
CLIN SIGNS;ocular discharge (of any variety), blepharospasm, maybe corneal oedema, maybe iris protrusion
DIAGNOSTIC WORK UP-thorough exam including plr’s and checking behind third eyelid and schirmers if no risk of rupture.fluoro. u/s by specialist if indicated.
TX & MANAGEMENT- if contents of eye protruding through hole greater than 4mm, r/o eye. If penetrating wound and still have plr, might be salvageable with specialist. For chemical keratitis have o flush eye with normal saline for at least 15 minutes before coming in. For melting ulcer use autologous serum. Get autologous serum by drawing up blood and placing aseptically in to red tops, then draw off serum. serum lasts 7 days. apply serum hourly (plus topical and systemic ab’s, pain relief etc).e collars. TEFs not recommended. sometimes can do temporary partial lateral tarsorrhaphy.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of DESCEMETOCOELE
AETIOLOGY-as per corneal ulceration, but the ulcer is deep or healing is not occurring as should eg brachy breed or some other compromising factor why cannot heal.
CLIN SIGNS-as per corneal ulceration. usually also have uveitis.
DIAGNOSTIC WORK UP
TX & MANAGEMENT-should be referral. best if specialist gets samples for culture. Autologous serum, topical ab’s, systemic doxy, usually systemic nsaids, occasionally systemic steroids. AVOID topical steroids or topical nsaids.Temporary tarssorraphy.REFERRAL. E collar.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of UVEITIS
AETIOLOGY;inflammation of iris or ciliary body (anterior) or choroid (posterior).May be due to penetrating injury/trauma or issues within eye, or systemic illness from bloodstream eg parasite, autoimmune ,neoplasia, infectious.
CLIN SIGNS-photophobia, may have miosis, episcleral congestion, corneal oedema, reduced intraocular pressure (due to reduced aqueous humour production and/or
increased uveoscleral outflow as a result of prostaglandin release), aqueous flare (due to breakdown of blood ocular barrier cells can penetrate and seen as cloudiness which is graded 1 to 4). Might see hyphaema (blood cells at bottom) or hypopyon (white cells or pus at bottom)
DIAGNOSTIC WORK UP-if no obvious trauma, MUST work up for a systemic cause ie bloods, urine, possible imaging etc. Suspect systemic if no obvious trauma or history of trauma, if bilateral , and if posterior uveitis present. Do cytology on any draining lesions or any lumps anywhere on body.May need toxo titres etc. When failed to find a cause, sepcialist will need to take ocular samples for cystology and c+s.
TX & MANAGEMENT
A. anti-inflammatories
1.Topical corticosteroid
CONTRAINDICATED if corneal ulceration present
Mainstay of treatment
1% prednisolone acetate or 0.1% dexamethasone
Frequency dependent on CSx and degree of flare (at least 1 more treatment per day than the grade of the flare present on examination)
Slowly tapered as clinical signs resolve (i.e. redness, flare, cell, miosis, lowered IOP)
2.Systemic corticosteroid
Only after systemic infectious process has been ruled out → risks severe systemic illness
Generally reserved for cases where loss of vision is imminent
Prednisolone 0.5-2mg/kg/day divided dose tapering as inflammation subsides
3.Topical non-steroidal
Do not use in patients with glaucoma or pre-disposition to glaucoma
Use in patients with corneal ulceration with care! Not recommended as a treatment with the risk of promoting keratomalacia. (There is a misconception that topical NSAIDs will provide clinically relevant analgesia. They may do so by reducing uveitis but systemic NSAIDs are much more effective for analgesia.)
** Still be cautious as topical NSAIDs can still precipitate melting
Not as potent as steroids
Flurbiprofen 0.3%, diclofenac 0.1% or suprofen 1%
Systemic NSAIDs are recommended pending results of diagnostic testing providing no systemic contraindications
4.Systemic immunosuppressive drugs
E.g. Cyclosporin, Azathioprine, Leflunomide (but probably beyond scope of emergency medicine - specialist level medication and should really only be prescribed by a specialist)
Only when unresponsive to conventional therapy and infectious causes have been excluded
B. Others
1.Mydriatics (e.g. Atropine - see previous warning on Atropine usage)
Reduce pain by reducing ciliary muscle spasm
Also will stabilise blood-aqueous barrier
Frequency dependent on severity
Mild: EOD
Moderate: SID to BID
Severe: BID to TID
Use until pupil dilates then as needed to keep pupil dilated
*** Caution: normal to high IOP indicating risk of glaucoma
Contraindicated in cases with secondary glaucoma
Can reduce tear production → contraindicated in severe ulceration secondary to dry eye (use atropine ointment instead)
2.Topical antibiotics
Only indicated when corneal ulceration or stromal abscess is present
3.Glaucoma treatment – if present
2% dorzolamide TID for secondary glaucoma
4. Tx for tick, antifungal, parasites etc only with evidence.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of GLAUCOMA
AETIOLOGY
1.Congenital glaucoma (rare)
Can affect any breed,very early onset,
rapid onset of buphthalmia (enlarged globe),px grave – requires enucleation
2.Primary glaucoma;breed-specific inherited trait;
American Cocker spaniel, Basset hound, Boston terrier, Beagle, Shiba Inu, Poodle, Chow chow, Shar Pei etc.
Bilateral disease with other eye affeceted months to years later. Breed variation of onset (can be from very young to very old).
3.Secondary glaucoma;due to anterior lens luxation, hyphaema, chronic uveitis, or intraocular neoplasia
Have a high degree of suspicion of concurrent lens luxation in terrier breeds and be aware of really should see a specialist for any pure-breed dog that is not predisposed to glaucoma.
Glaucoma can be further divided into acute and chronic based on rapidity of onset of clinical signs.
CLIN SIGNS;episcleral congestion, bupopthalmia, ocular pain, blindness, fixed dilated pupil, secondary corneal oedema,dry eye, Haab’s striae (severe corneal oedema), optic disc cupping.
DIAGNOSTIC WORK UP;IOP>30mmHg with consistent signs. Should also do cbc, biochem urine, and for cats fiv/feleuk and toxo titre.
TX & MANAGEMENT
1. Latanoprost (brand name Xalatan), Travaprost
First drug to use
Prostaglandin analog
Start to lower IOP within 30 minutes
Contraindication: anterior lens luxation – causes miosis and worsens pupillary block caused by lens luxation
q12-24hrs (most needing q12hours)
- Dorzolamide, brinzolamide, dichlorphenamide, methazolamide
3-5mg/kg
Topical carbonic anhydrase inhibitors
q8hrs - Cosopt (Timolol + dorzolamide)
Mode of action: topical beta blocker + carbonic anhydrase inhibitor
Dosing regimen: q12hrs
Contraindication: renal failure, cardiomyopathy
Use as “prophylactic” treatment in the non-clinical fellow eye in the case of primary glaucoma to delay the development of an intraocular pressure spike - Mannitol (20%)
Second line – only used if above methods cannot decrease IPO within an hour
Mode of action: hyperosmotic agent that dehydrates the vitreous body → lower IOP
Dose: 1–2g/kg IV slowly over 30 minutes or ongoing CRI @ 1-2mg/kg/min
Water withheld for 1-2 hours after mannitol administration then gradually introduced in small amounts
Contraindication: renal disease, cardiovascular disease, dehydration or other debilitating illness
*** Not effective in cases of concurrent intra-ocular inflammation (i.e. uveitis) as osmotic blood eye barrier broken down - Corticosteroid (prednisolone acetate)
–
Feline glaucoma and secondary glaucoma only
Anti-inflammatory
Q12–6hrs
Contraindication: corneal ulceration
MONITORING;
Hourly IOP measurement until 25mmHg for at least 2 consecutive hours
4- to 6-hour interval once IOP is within normal range (10-25mmHg)
Long term: q2-3 monthly check up
REFER asap if bad eye has dazzle response or plr and/or if good eye has consensual plr as vision may be restorable.
Otherwise, if IOP raised for more than a few hours, blindness in eye inevitable.
Enucleation if IOP remains elevated.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of HORNER’S SYNDROME
AETIOLOGYlack of sympathetic tone to affected eye
CLIN SIGNS-affected eye has a miotic (small) pupil which does not dilate in darknes (is important to verify this). Affected eye is enopthalmic, third eyelid prolapsed and smaller palpebral fissure.
DIAGNOSTIC WORK UP; Cause may be a disruption to the sympathetic nerves anyway along the pathway;
a)First Order Lesions:occur along nerves from Hypothalamus in brain,brainstem, spinal cord.eg tumour, vascular incident, intervertebral cervical disc dz etc. MRI etc
b)Preganglionic or Second Order Lesion; along the pathway where nerves have excited spinal cord but travel back up neck to middle ear.eg Foreleg injury because has been pulled, hard leash pull, sometimes tumours/granumomas within chest. eg chest xrays, mri etc
c) Post ganglionic or Third Order Lesion;from ear to eye. These are the most common category. ddxmiddle ear dz, local facial trauma, sometimes have vestibular dz (if extraocular mm. also affected → static strabismus [(Latero-ventral)]
PHARMACOLOGICAL TESTING;
Confirm whether lesion is either a sympathetic dysfunction (Horner’s Syndrome) or a parasympathetic dysfunction (CN III lesion)
Usually can determine from neurological examination with light stimulus in the dark alone and pharmacological testing not required
Failure of dilation of the affected pupil in the dark + other characteristic features → definitive diagnosis of Horner’s
** Must ensure have examined pupil function before pharmacological testing
Basis of pharmacological testing → development of denervation hypersensitivity within the eye of Horner’s patients
Requires development for at least 7-14 days
Denervation hypersensitivity resulting from the sympathetic denervation allows pharmacological testing to be performed to predict the site of the lesion based on increased sensitivity to topical phenylephrine
Denervation hypersensitivity occurs where there is interruption of automatic innervation to a target organ/smooth muscle → loss of degradative enzymes at the synapse → synaptic receptor becomes highly sensitized to receptor agonists
Horner’s Syndrome classified according to the level of the lesion along the sympathetic pathway as 1st order, 2nd order (pre-ganglionic) or 3rd order (post-ganglionic)
Time to pupillary dilation post 1% phenylephrine topically in both eyes is determined
Times to respond should only be used as a guide
Topical 1% phenylephrine → resolution of miosis → mydriasis
3rd order Horner’s syndrome (post-ganglionic lesion): <20 minutes
2nd order Horner’s syndrome (pre-ganglionic lesion): 20-45 minutes
1st order Horner’s syndrome: 60-90 minutes (or no sympathetic denervation of the eye)
TX & MANAGEMENT-no tx necessary for the horner’s syndrome-is not painful nor affect vision. BUT if ongoing does need an internal medicine complete work up to find the underlying cause which MAY NEED extensive tx/diagnostics etc.
At least initially verify lack of pupil dilation in dark and that other eye does, that animal mentally ok and walking ok ,resp ok,eye exam and ear exam. Then further testing if still issues 1-2 weeks.
Describe the aetiology, clinical signs, diagnostic work up, tx & management of PROPTOSIS
AETIOLOGY-trauma
CLIN SIGNS-globe forward of orbit
DIAGNOSTIC WORK UP-check whole animal for other injuries
TX & MANAGEMENT
It is desirable to replace globe asap. It is essential owners apply sterile saline, water or petroleum jelly (vaseline).Appropriate analgesia is essential. Choose a pure μ-receptor agonist where possible. Apply topical anaesthetic and topical ab before thick protective gels. under ga thoroughly flush, suture through eyelids, scalpel blade handle pressure eyeball back in position. Flush flush flush. Leave small opening at medial canthus .Must E collar. Avoid any tugging on neck. Systemic ab’s. Topical ab’s every 4-8 hours. Pain relief. Episcleral congestion takes 6 weeks to resolve. Vision may or may not be saved. Worse px if facial fx, if long nosed breed or if cat, if more than 3 periocular muscles avulsed or if no direct or indirect plr.
Go straight to enucleation if;Enucleation should be considered if:
Owners are unable to provide post-operative care
Globe has ruptured
Three or more extraocular muscles are torn
Eye is completely filled with blood,
o prefers this option.
