Module 1 Flashcards
Key points of general history:
Breed (looking for inheritance) Age and sex General health (ocular conditions may manifest from systemic disease) Medication (previous or current) Multi-pet (infectious) Source (rescue vs breeder)
Ophthalmic history
What did owner notice
Length of time
Progression (stable or worsening)
Unilateral or bilateral
Clinical examination - off the table
General behaviour Bumping Blepharospasm Photophobia Comformation
Ophthalmic exam - on the table
Considerations: nurse to restrain, darkened room, illumination (in room and focal source), magnification
General examination
Head: symmetry, lid position, discharge, from above (exophthalmos on enophthalmos) and move the head (nystagmus)
Palpebral: afferent CN V (sensory), efferent CN VII (motor)
Corneal reflex: afferent CN V, efferent CN VII
Corneal reflection (purkinje image); information on corneal health
Focal light source - examine lids, conj, TEL, periorbital disease
Retropulse eyes (restricted in branchys)
Vision assessment
Menace: afferent II, efferent VII. Care not to cause air movement, learned response and not present in young animals
Dazzle: bright light quickly shone into each eye, bilateral blink and TEL protrusion. Positive = CN II intact to midbrain and fibres in CN VII nucleus
Other: cotton wool, visual placing, obstacle course
Pupillary Light Reflex
NOT an assessment of vision, blind animals can have PLR
Adrenaline may interfere with PLR
Focal light source, assess in light and dark
Direct and indirect/consensual (via decussation of pupillomotor fibres in optic chiasm)
Swinging flash light (illuminate one eye 2-4s, redirect to opposite eye for 2-4s) and note response
Margus Gunn sign - during swinging flashlight the direct response +ve, consensual PLR +ve, when fellow eye illuminated suddenly dilates. Pathognomonic pre-chiasmal lesion
Distant Direct Ophthalmoscopy
Arm’s length
Dark room
0 D
Fundic light reflex
Pupil size, shape and symmetry
Opacities in visual axis - cast shadow on tapetum and appear black
Parallax - direction of movement of opacity relative to the observer relative to plane of pupil. Anterior opacities move in opposite direction to observer, posterior to pupil opacities move in same direction as observer
Cataracts vs nuclear sclerosis - nuclear sclerosis will not cast a shadow on tapetum and rings can be visualised
The Direct Ophthalmoscope
Features:
- on/off switch with rheostat
- lens magazine
- beam selector (largest beam possible unless small pupil)
- slit beam
- red-free light (green - blood appears black
- cobalt blue (fluorescein)
- graticule (measure lesions)
- detachable Finhoff illuminator
- 20D to +20D
- detailed view the right way up but small field of view and close to animal
Direct Ophthalmoscopy
Initial exam undilated then dilated with tropicamide
Close to your eye, 0D, home through pupil until 2-4cm from patient
Divide into quadrants and examine each section in turn
Assess: optic disc, blood vessels, tapetal fundus, non-tapetal fundus
Depression on the fundus will need minus lenses to examine
Plus lenses to examine anteriorly
0D fundus, +8-12D lens, +20D cornea
Indirect Ophthalmoscopy
- Monocular - focal light source against observer’s temple, obtain retinal reflex, lens (20D) 5-8cm in front of patient’s eye, all in same axis, hands are tied up but cheap
- Monocular indirect ophthalmoscope (Panoptic) - half way house (correctly oriented image)
- Binocular - head set and lens (stereopsis) and frees hands
Wider view of fundus, less magnification, rapid exam, better light penetration improving examination with nuclear sclerosis, immature cataract or anterior chamber/corneal opacities.
Pupils must be adequately dilated. Imagine is upside down and back to front. Lens positioning most common problem if not successful
Slit Lamp Biomicroscopy
Hand-held or table mounted, primarily for anterior chamber
Light beam - wide spot to narrow beam. Altering angle between light beam and microscope portion; optical section can be examined
Use: 1 - direct illumination: using widest beam of light examine adnexa, cornea and intra-ocular structures (+goniolens to examine ciliary cleft), 2 - direct illumination with slit beam: directed obliquely, illuminating opaque structures and optical sectional through transparent structures, 3 - retro and trans-illumination: beam directed behind the lesion, retro-illuminated by light reflected from posterior structure (useful for uveal cysts), 4 - fundic exam: in human ophtho, requires -55D Hruby lens applied to cornea or +90D lens in front of cornea
Consult room tests
STT - aqueous portion, STT I basal and reflex tears over 60s
-Dog: <10mm KCS, 10-15mm under-production, 15-25 norm, >25 over
-Cats are variable
Fluorescein - stains stroma, hydrophilic lipophobic. Not epithelium or descemet’s membrane; they are lipophylic and hydrophobic.
-Blue light enhances, flush, after STT and exam, assess naso-lacrimal drainage (Jones test +ve helpful, -ve means nothing)
Rose Bengal - stains damaged epithelium, dendritic ulcers (FHV), irritant
Local anaesthetic - proxymetacaine or tetracaine (low pH, stings). Aids examination. Can contaminate samples so avoid if possible
Tonometry - measurement of IOP
Schiotz - indentation tonometry, not precise, concave base plate and weight plunger and a pivoted needle with graduated scale. Topical anaesthesia required. cornea must be horizontal. Conversion table used to determine IOP.
Tonopen - applanation tonometry, force required to flatten the cornea, central rod in an outer sleeve, rod contacts cornea and then recoils. Modern Tonopen converts reading digitally. Topical needed
Tonovet - rebound tonometry, bounces magnetised probe at the cornea, detects deceleration of probe caused by cornea. Can be performed without topical.
Gonioscopy
Examination of the opening of the ciliary cleft and pectinate ligaments. For glaucoma patients, as screening for goniodysgenesis in breeding animals and uveal tract neoplasia.
Ciliary cleft in the cat can be examined directly.
Goniolens alters the angle of incidence overcoming total internal refection.
Lenses: Franklin, Koeppe (filled with false tears), Lovac, Barkan-Lovac (has length of tubing for saline)
Topical, lens usually maintained by negative pressure, examined with direct ophthalmoscope, slit-lamp, or hand-held fundus camera
Alternative - small condensing lens (30D) pressed onto the cornea (limited use)
Mydriasis
Tropicamide 1% for diagnostics. Essential to examine lens and retina thoroughly.
Atropine 1% for therapeutics.
NOT in glaucoma
After rest of examination i.e. gonio and IOP
May not be very effective in microphthalmia
