Flashcards in Clinical examination of the eye 1 and 2 Deck (43):
3 main owner concerns
- altered appearance
- loss of vision
1st part of opthalmic exam
Hands-off observation of facial/ocular symmetry
How do you take a tear reading?
Schirmer tear test 1 (STT1 - i.e. no anaesthesia)
- BEFORE light, eyelid manipulation
- do LATERALLY, b/w eyelid and cornea, don't poke cornea, 3rd eyelid shouldn't interfere
How do corneal sensitivities vary?
sensitivity varies depending on the number of corneal nn - humans have many, dogs have much less, brachycephalics the least
Where do you insert the tip of the STT notch into?
into the lower conjunctival fornix
Outline STT-1 results
Rough guide (always correlate with CS, other eye):
15mm/min + are normal
10 mm/min less are low
In between =unclear so repeat test
Describe the progression of dry eye (KCS)
asymmetrical and progressive
When to do assess the menace response...
after STT1 readings but can do it before
Outline menace response examination
Quickly part fingers in front of eye
You may touch medial/lateral canthi before testing
This is a learned response (cortical, not reflex)
Tests for vision (crudely)
How do you examine the eye with light?
From outside inwards:
- eyelids and nictitans
- tear film and NSL
- intraocular structures (uvea, lens, retina)
Name 3 light exam techniques
1 transillumination/slit examination
2 direct opthalmoscopy (DO) - distant and close-up
3 indirect opthalmoscopy (IO)
What are the 2 points of transillumination/slit exam
- Anterior structures of the eye (transilluminable versus non- transilluminable structures)
- Reflexes (dazzle, PLR via direct (R and L) and indirect (R to L)
Name non-transilluminable structures of anterior eye
eyelids, conjunctiva, 3rd eyelid
List transilluminable structures of the anterior eye
cornea, iris and anterior lens
- assess contour and lesion depth (ulcer, cataract)
What is a rheostat?
Part of the opthalmoscope - it is the on/off switch and dimmer
Name light filters on an opthalmoscope
BLUE - to show fluorescein dye (ulcers)
GREEN - red free, blood/BVs appear black, pigment remains brown
What can you see with a circular, bright beam
Overall brightness and moisture
PLR and dazzle reflexes (blinding cataracts have no effect on these if the light is bright enough)
What do you use the slit beam to asses? 3
Surface contour - cornea, iris, anterior lens
Layers - cornea (ulcer depth), lens (cataract localisation)
Anterior chamber - aqueous humor quality (transparent/turbid, blood/cells/protein)
What is flare?
What you see when you pass through aqueous humor that has debris in it. Results in keratic precipitates if these settle.
What is the major limitation of examining the cornea with light?
ulcer depth calculation requires a fine (0.1mm) focused slit from a slit lamp, which hand help opthalmoscopes don't have, and require years of practice under investigation.
List changes of the anterior chamber (AC)
- Aqueous flare = 'tyndall effect'
- Keratic precipitates (deposits on ventral endothelium)
- Hyphema (blood)
- Hypopion (WBC accumulation, pus)
- Posterior/anterior synechia
- Anterior lens luxation (ALL)
- Anterior presentation of the vitreous
- Protein accumulation in AC
What is the 'tyndall effect'?
AKA aqueous flare
An accumulation of proteins and cells in the AC
- Becomes keratic precipitates when these materials settle ventrally
How can you differentiate nuclear sclerosis from a cataract?
How can you examine the posterior segment of the eye?
- CDO or IO
- Retina mostly, also vitreous and lens
Describe direct opthalmoscopy
Look directly through opthalmoscope into eye
2 methods - distant (DDO) and close (CDO)
Describe indirect opthalmoscopy (IO)
Look indirectly, at image of the fundus.
-Use a 15-20-30D lens and hand held/head-mounted opthalmoscope
- inverted, L to R,
--> VIRTUAL image ( as upside down and back to front)
- wide field of view but less magnified
What is the lens wheel on an opthalmoscope?
found on the part of the opthalmoscope facing the patient, it has:
- positive lenses (green or black) 20,18....,6,4,2
- mid point = neutral setting = 0 (for perfect vision, adjust if you wear glasses, different for DDO and CDO)
- negative lenses (red) -2,-18,-16...-20
How do you adjust the mid point/neutral setting for someone who is near sighted?
From -2 to -4
How do you adjust the mid point/neutral setting for someone who is far-sighted?
from +2 to +4
What do you aim to do with DDO?
Aim to use the tapetal reflection (angle your view towards the patient, make the patient's pupil shine). Thus the tapetal light retroilluminates the lens. This helps to differentiate nuclear sclerosis and cataracts:
- Nuclear scleorsis = transparent
- Cataracts = black
What should you do with CDO?
- locate optic disc
- divide into quarters
- make a mental collage - big area, all BVs lead to optic disc)
- right eye to right eye THEN left eye to left eye (or if you cannot close one of your eyes, 'go over' the nose)
Using CDO, if you see a lesion clearly at a reading of 0 where is it likely to be?
at the back of the eye
Using CDO, if you see a lesion clearly at a reading of +15 to +10 where is it likely to be?
How does the diopeter power with indirect opthalmoscopy (IO) affect the magnification?
The larger the diopeter power, the lower the magnification
How does the magnification with indirect opthalmoscopy (IO) affect the field of view?
The lower the magnification the larger the field of view, therefore increased diopter power, decreases magnification, increases field of view
What is a panoptic opthalmoscope?
A type of indirect opthalmoscopy where the benefits of a wide filed of view and normal anatomy (i.e. not upside down and back to front) are combined
List some additional tests for the opthalmic exam
- Fluorescein staining - ulcer, jones test
- IOP - tonometry
- Gonioscopy - a specialist's tool
- Imaging (US, CT, MRI)
Outline the fluorescein staining
- strips are preferred over drops
- adheres to stroma (hydrophilic)
- repelled by epithelium
- don't touch strip to cornea (dry or wet)
- wet strip with saline
- apply a drop onto dorsal conjunctiva
- look for ulcers or nasolacrimal duct patency
- rinse thoroughly with saline, examine corneal surface and always look with a blue light
What is the Jones test?
an adaptation of the fluorescein test.
- do not rinse
- wait a few minutes
How can IOP be assessed?
Indentation (old, cheap, inaccurate) - Schiotz
Applanation (new, expensive, accurate) - Tonopen Vet
Rebound (new, expensive, accurate) - Tonovet
What is tonometry useful in?
Distinguishing glaucoma (increased IOP) from uveitis (decreased IOP).
Normal IOP range is 12-22(24) mmHg
What is gonioscopy?
Gonioscopy is an eye examination to look at the front part of your eye (anterior chamber) between the cornea and the iris. Gonioscopy is a painless examination to see whether the area where fluid drains out of your eye (ICA) is open or closed.
BUT a narrow or closed ICA doesn't always correlate with glaucoma (i.e. a raised IOP)