Ophthalmology Flashcards
The basic parts of the ophthalmic examination are: (3)
- History taking
- Hands-off examination
- Hands-on examination
(- Schirmer tear test readings
- Vision testing and neurological testing
- Ophthalmoscopy
- Ophthalmic dyes
- Tonometry)
The basic parts of the Hands-on ophthalmic examination are: (5)
- Schirmer tear test readings
- Vision testing and neurological testing
- Ophthalmoscopy
- Ophthalmic dyes
- Tonometry
corneal sequestrum
A corneal sequestrum is when an area of the cornea ‘dies off’ and reacts with surrounding healthy cornea.
Over time the cornea rejects this abnormal tissue and attempts to ‘wall’ the area off causing a sequestrum.
typical patients are persian cats (predisposed)
General history should include: (6)
- Breed/genetics
- Age
- General health
- Presence of other pets in house
- Source of the pet! (e.g. infectious diseases in shelter animals like herpes and chlamydia cats)
- Reason for examination
Collecting a complete ophthalmic history
Hands-off examination (3)
- Observation from distance
- Notice:
-signs of ocular discomfort – blepharospasm
-increased lacrimation
-symmetry of the eyes and face
-enlargement of the globe
-periorbital swelling
-periorbital hair loss and erythema - Basic assessment of visual ability
Basic Diagnostic Instruments and Supplies in ophthalmology
Topical anesthetic for eyes
Proxymethacaine, trade name (Alcaine 5mg/ml)
Oftan Obucain -silmätipat sisältävät oksibuprokaiinia (common in finland)
The effect comes on approximately one minute after application and lasts approx. 5 min.
Topical anesthetics are not indicated as treatment in painful conditions, due to their tissue toxicity (delay healing so cannot be used regularly).
short acting mydriatic
Tropicamide eye drops 0,5-1%
Tropicamide is an anticholinergic drug and that works by non‐selectively blocking muscarinic receptors to cause mydriasis and cycloplegia.
(Cycloplegia is the paralysis of the ciliary muscle of the eye resulting in dilatation of the pupil and paralysis of accommodation. )
direct vs indirect ophthalmoscope
direct is handheld
In direct ophthalmoscopy, the examiner looks directly through the device’s viewing aperture to visualize the fundus (the interior surface of the eye). The light from the instrument illuminates the retina, allowing the examiner to see its details.
Direct ophthalmoscopes provide a limited field of view of the retina, usually around 5-15 degrees. This narrow field of view can make it challenging to examine the entire retina at once.
provides an upright, unreversed image of around 15 times magnification
indirect is a headset/loupes
Indirect ophthalmoscopes consist of a light source mounted on a headband or handheld device, along with a condensing lens. They also require the use of a handheld lens, known as a condensing or viewing lens.
In indirect ophthalmoscopy, the examiner sits at arm’s length from the patient and holds the condensing lens in front of the patient’s eye. The light from the ophthalmoscope is used to illuminate the retina, and the examiner views the magnified image of the fundus through the condensing lens.
Indirect ophthalmoscopes provide a wider field of view compared to direct ophthalmoscopes, typically around 20-30 degrees. This broader field of view allows for better visualization of the peripheral retina and a more comprehensive examination.
produces a reversed, inverted image magnified 2 to 5 times
How to begin an ophtho Examination: (6)
- Explain shortly to the owner what and why you will do.
- Both eyes, not just “sick” eye
- Start from „healthy“ eye
- Ask owner to help you
- Towel wrapping where needed
- Give some comments about findings
during the examination.
Hands-on examination -course (5)
- Examine from the front, sides and from above.
- Presence of ocular discharge – the nature of it, uni/bilateral.
- The size of both eyes, head symmetry.
- Position of the eyes (exophthalmos, enophthalmos, strabismus).
- Eyelid changes, periocular alopecia and discharge form eyes or nostrils
STT
The Schirmer tear test measures production of the watery part of the tears.
- Should be done before the eyes are cleaned or handled further.
- The strips should be bent at the notch while still in their plastic wallet.
- Hold the stripes at the distal end placed in the ventral conjuctival sac.
- Placed at the lateral to middle third of the lower eyelid.
epiphora
excessive tear production
What is buphthalmos?
Buphthalmos is the medical term for an inherited congenital enlargement of your eye.
STT results
The stripe is left in position for 1 minute before removing it and immediately reading the level of wetting on the scale.
Dogs, normal: 15-25 mm/min
Borderline: 10-15 mm/min
KCS: < 10 mm/min
KCS is rare in cats but e.g. can be caused by chronic herpes virus.
Exclude the following if animal has blepharospasm (painful eye): (4)
- Foreign body in conjunctiva, cornea, under eyelids, third eyelid.
- Aberrant cilia or hair (distichia or ectopic cilia).
- Evaluated by staining with Fluorescein – for detecting corneal ulcer.
- Third eyelid examination – use topical anesthesia, blunt tipped ophtho forceps and a light source/magnification.
Corneal Pannus
Corneal pannus means the growth of fine blood vessels onto the clear corneal surface. The treatment depends on the cause.
Pannus is an abnormal layer of fibrovascular tissue or granulation tissue. In GSDs it is often UV ray induced (so, sunglasses may be seen in use).
Ectopic cilia
To examine the Eyelids/cornea/anterior chamber/lens, you need:
Biomicroscope, light and magnification 10 x and 16 x
Describe a Biomicroscope
Full beam/round beam → examine for distichiasis, ectopic cilia, as well as punctal anomalies, corneal foreign bodies. Useful for dazzle reflex testing (partial blink in response to a bright light).
Slit beam → gives indication of the depth of lesions (cornea/lens).
* 0,8 mm helps us visualize transparent tissue generating a parallel-piped (Tyndall effect).
* 0,1 mm epithelium, stroma and endothelium become visible
Eyelids are examined for (5)
position, the presence of swelling,
eyelash abnormalities and the position and size of nasolacrimal punctae.
Most common Ophthalmic dye
Fluorescein test
- Water–soluble dye which stains corneal ulcers green.
- Impregnated strips or single-use vials can be used.
- The intact cornea is lipophilic – no uptake of fluorescein. When epithelium is damaged – dye will adhere to the stroma.
- Descemet’s membrane ulcers might not stain bright green.
- One drop of the stain is applied on the cornea, try to only touch the bulbar conjunctiva.
- Flush excess dye away with sterile saline to prevent false positives.
- Blue light (cobalt blue filter) to view.
Green stain in the area of corneal ulcer = the fluorescein test is positive
Deep ulcers (Descemet’s membrane or ulcer)
The membrane will not stain but will present as a clear spot in the middle of the green stained walls.
Jones test
Initial assessment of the nasolacrimal drainage system can be made
using fluorescein dye (Jones test).
A drop is placed in each eye and the nostrils are observed for the appearance of green color.
False negatives are common. Results take longer in brachys due to anatomy.
Rose Bengal dye
- Indications: defects in the superficial corneal epithelium.
- Paper strips and solution
- Examine with normal white light + magnification.
- Small dendritic ulcers in feline herpetic keratitis.
Direct ophthalmoscopy
- upright image of the patient’s fundus
- noninverted and magnified 15 to 17 times
- the field of view is much more restricted as compared with indirect techniques due to the higher magnification
- focal fundic lesions/optic nerve hypoplasia/anterior chamber
- Low cost
- Lack of stereopsis (difficult to discern depth of lesion)
- Limited evaluation of the peripheral fundus
- Proximity of the examiner’s face to the patient
Steps of fundic examination: Direct ophthalmoscope
- Dark room, lens set to 0 D for fundus.
Locate the patient’s fundic/tapetal reflection
from approximately an arm’s length distance.
May reveal:
Anisocoria (different pupil size)
Dyscoria (abnormal pupil shape)
Absence tapetal reflection
Aphakic crescent if the lens is subluxated or
luxated
Strabismus (abnormal direction of gaze)
Nuclear sclerosis
- Then move 2 to 4 cm from the patient’s eye to widen the field of view
- Identify the optic nerve, then
thoroughly examine the remainder of
the fundus in quadrants.
Direct ophthalmoscope slit beam for evaluating
fundic elevations and depressions & anterior segment magnification.
Direct ophthalmoscope:
graticule grid for →
size estimation
Direct ophthalmoscope:
cobalt blue light for →
viewing corneal fluorescein uptake
Direct ophthalmoscope:
red-free light for →
differentiation of
hemorrhage (appears black) and
pigment (appears brown)
A direct ophthalmoscope held 2 cm from the cornea can focus on what structures at what diopters?
(the lens wheel should be rotated through positive diopters to bring various structures into focus)
- Cornea +15 to +20
- Anterior chamber +12 to +20
- Iris and pupil +12
- Lens +8 to +12
- Vitreous 0 to +10
whats this
Monocular indirect ophthalmoscope (Indirect ophthalmoscopy)
you can still evaluate the fundus this way
whats this
Binocular indirect ophthalmoscope
(Indirect ophthalmoscopy)
this one tends to show you more
describe this
Indirect ophthalmoscopy:
* 20 D or 30 D (diopter) handheld lenses for dogs and cats
* Large field of view
* Inverted and reversed image is obtained
* Low magnification
* Safer working distance from the patient (your face is farther away, your hand is still held in front of the eye)
* Expensive
Neuro-ophthalmology assessment. step
1. Explain.
- Menace response – cover one eye with one hand and stimulate (hand/finger) the other eye avoiding air currents. Perform on medial and lateral side. Eyelid closure is expected. Not present in dogs and cats under age 8-12 weeks.
- Afferent: retina and Optic nerve (CN II)
- Efferent: ipsilateral Facial nerve (CN VII)
Positive – vision is present
Negative – blindness, facial nerve paralysis or cerebellar lesion
Neuro-ophthalmology assessment steps
4. & 5. Explain.
- Maze testing- unfamiliar room, mixture of objects randomly placed in the room, animal at one corner and owner at the other side.
- Visual placing response (pictured)
Neuro-ophthalmology assessment step
7. Explain.
Pupillary light reflexes (PLR) in a dim light conditions (Focal strong light for pupil examination).
Direct
* Afferent: retina, optic nerve (CN II)
* Efferent: ipsilateral parasympathetic part of the oculomotor (CN III).
Indirect or consensual
* Afferent: retina-optic nerve (CN II)
* Efferent: contralateral parasympathetic part of the oculomotor (CN III)
* Negative – retinal, optic nerve or oculomotor nerve lesions
What is the Tyndall effect in the slit lamp?
Similarly, the slit lamp makes use of the Tyndell effect to illuminate particles that may be floating in the fluids inside your eye. Called “cells,” these particles are the byproducts of inflammation (white blood cells) and can be observed using the slit lamp as a light source.
