Opthalmic Examination 1 Flashcards
What 3 aspects must be taken into account when recognising lesions?
- tissue response to injury
- interaction between tissues in the eye
- possible stages of every disease process
3 main owner concerns in ophthalmic Hx?
- altered appearance of the eye
- loss of vision
- presence of pain
3 main aspects to judge facial/ocular symmetry?
- draw line lateral-medial canthi, see how much of the globe lies above/below the line
- medial canthus - pupil distance
- 3rd eyelid surface area (NOT pigment!)
How is the 3rd eyelid naturally extruded? When may this not be the case?
- pain/discomfort -> retropulsion of the globe -> displacement of retrobulbar fat pad rostrally -> protrusion of 3rd eyelid
- IF globe is pushed out/bulging [exopthalmus] AND 3rd eyelid is protruded suspect space occupying lesion (tumour/cysts etc.)
When should STT be carried out? How is this carried out?
- before use of light or eye maniopulation
- place laterally (avoid TE) between eyelid and cornea (lower conjuctival fornix,) care not to poke cornea
- wait 1 min per eye
- test both eyes and compare
Which species have most and least sensitive cornea
(most sense) Humans, Rabbits, Cats, Dogs, Brachycephalic Dogs, Brachy Cats (least sense)
How does STT2 differ?
Local Anasthetic applied before test
Simplified analysis and reference ranges of STT readings
15mm/min normal
- inbetween unclear, repeat
When may a “normal” STT result be abnormal?
Ulcer present but STT 17mm - normal? NO, should be tearing up d/t pain from ulcer -> off the scale STT. So 17 is LOW and ulcer likely d/t dry eye.
How does KCS present?
- Keratoconjuntivitis Sicca
- asymmetrical and progressive dry eye
When should menace test be carried out?
preferably after STT test
Is the menance response a reflex? What does it test?
- NO learnt response, cortical (not subcortical reflex)
- tests vision (cortex involved) but v. crude
What cranial nerve provides touch innervation to the globe and ocular region?
Opthalmic branch of trigem
What are the 3 light examination techniques?
- Tranillumination/Slit examination
- Direct ophthalmoscopy (distant and close)
- Indirect Opthalmoscopy
What can be assessed using transilulmination/slit examination?
- Anterior structure of the eye
- eyelids, conjunctiva and TE
- cornea, iris and anterior lens (contour and lesion depth of cataracts and ulcers) - Reflexes
- dazzle reflexes
- PLRs (direct and indirect)
> NB: blinding cataracts will not always stop these reflexes
What colour light is used to visualise fluorescin dye?
Blue
What other colours of light are available on an opthalmoscope?
Greeen - no red so blood/blood vessels appear black but pigment remains brown
Why does indirect PLR occour?
Decussation of fibres at the optic chiasm
How is the PLR test carried out?
- Test one eye, check for constriction of the other
- swinging torch test - switch between both eyes, both should remain constricted
Damage where will affect PLR?
- retina
- optic nerve before the chiasm
What limitation doe a standard general practice opthalmoscope have?
- cannot tell depth of ulcers without v. expesive refrerral slit lamp biomicroscope thingy.
What can be seen using a slit lamp ion transilluminable structure?
- surface contour (cornea, iris, anterior chamber, anterior and posterior bellies of the lens)
- layers (cornea, lens cataract localisation possible)
- anterior chamber (quality of aqueous humour, transparent v. turbid “flare”)
How thick is the cornea?
~0.5mm dogs
~0.8mm LA
How can ulcer depth be defined in general practice?
Pothole? Deep
What is necessary in order to see both anterior and posterior bellies of the lens?
Massively dilated pupil!
