Ophthalmoscopy Flashcards
What is Ophthalmoscopy?
Simplest method to ascertain the health of internal structures of the eye.
What is Ophthalmoscopy also referred to as?
Fundoscopy
What is Iatrogenic Damage?
Illness caused by medical examination/treatment.
List 4 reasons why it is important to view the structures of the eye?
1) Indication of Visual function
2) Clues of systemic general health status
3) Any abnormalities or presence of pathology can be identified and avoided altogether
4) Assess any Iatrogenic Damage results from invasive procedures carried out
What is the Anterior Segment?
The area in front of the crystalline lens filled with aqueous humour
Anterior + Posterior Chamber
What is the Posterior Segment?
The area behind the crystalline lens filled with vitreous humour
Only Vitreous Chamber.
List some factors that can cause difficulties when viewing the internal structures of the eye.
- Pupil Size
- Opacity
- Insufficient Illumination
- Magnification
- Different needs/disability of a patient
Define Opacity
The quality of lacking transparency or translucence, becoming cloudy.
List the 3 principles that are essential when viewing the internal eye.
1) The patient and the practitioner have to be made emmetropic – parallel light rays fall directly on the retina resulting in no refractive error.
2) The retina of the patient has to be sufficiently illuminated
3) There has to be an optical alignment of the light source and the observer’s pupil.
What is the pupil?
A viewing aperture
In normal conditions, the pupil appears dark to an observer,
Why?
There is an absence of Tapetum Lucidium in human eyes.
What is Tapetum Lucidum?
In any Vertebrates like cats, there is a reflective layer of tissue found in the choroid of the eye which reflects visible light back into the retina, increasing the light available to the photoreceptors. It is a retroreflector because it reflects light back to its source with a minimum of scattering.
What is the functional purpose of Tapetum Lucidium?
It exists to increase visual sensitivity under dim light conditions.
It gives the photoreceptors a “second chance” to absorb light thus improving the abiltiy to see in the dark.
This is what causes an animals eyes to seeminly glow in the dark when a light is shone on them.
What is a Retroreflector?
A device which reflects light back along the incident path, irrespective of the angle of incidence.
What is Visual Sensitivity?
The ability to perceive differences between an object and its background.
What is an Ophthalmoscope?
A device that splits a beam of light so that the light will enter the eye, be reflected and return to the examiner’s eye via the same or a neighbouring path.
What is an Ophthalmoscope?
A device that splits a beam of light so that the light will enter the eye, be reflected and return to the examiner’s eye via the same or a neighbouring path.
What type of Image does Indirect Ophthalmoscopy create?
Aerial and Inverted
What type of Magnification is required for Direct Ophthalmoscopy?
x15
What type of Magnification is required for Indirect Ophthalmoscopy?
x2-5
List some Advantages for Direct Ophthalmoscopy?
- Small and portable
- Good to view ocular media opacities like Cataracts or floaters
- Magnified view of the fundus
- Dilation is generally unrequired
- Real and Erect Image
List some Disadvantages for Direct Ophthalmoscopy?
- Monocular view of the fundus
- No Stereopsis
- Very limited field of view
- Short working distance
- Unable to view the peripheral retina
- 2D Image
Name the 8 Apertures on the Direct Ophthalmoscopy?
1) Micro-spot
2) Small-spot
3) Large spot
4) Fixation Aperture
5) Cobalt Filter
6) Slit beam
7) Red-free filter
8) Polarising filter and half-circle aperture
When should you use a Micro-Spot Aperture?
Allows quick visual entry in very small, undilated pupils
When should you use a Small-Spot Aperture?
Provides an easier view of fundus through undilated pupils
When should you use a Large-Spot Aperture?
Standard aperture for dilated pupils and general examination of the eye
When should you use a Fixation Aperture?
Provides graduated crosshairs for measuring Eccentric Fixation or for locating lesions/abnormalities.
When should you use the Cobalt Filter?
Used with Fluroscein dye because this permits easy viewing of small lesions, abrasions and foreign objects.
When should you use a Slit-beam?
Used to determine elevation or depression of lesions and tumours using the monocular cue of beam bending.
When should you use the Red-free Filter?
Exclude red rays for easy identification and increased contrast between blood vessels from pigment, haemorrhages and vascular lesions.
When would the Red-free filter be most useful?
When assessing Diabetes - they appear dark against the light background of the Fundus.
When should you use a Polarising filter and Half-circle Aperture?
To decrease reflections from the corneal surface
What is the Setting up procedure for Direct Ophthalmoscopy?
1) Room lights off
2) Remove Px Spex - unless very high Rx
3) Raise chair for practitioner comfort
4) Give the patient a small fixation target like a spotlight
5) Hold the Ophthalmoscope in your right hand in front of your RE to assess Pxs RE from the temporal side
How would you explain the Optometric technique of Direct Ophthalmoscopy to a patient?
“I am going to check the health of your eyes. The light will be quite bright, and I will come close to you. Please keep looking at the spot of light for now, but I will ask you to look in different directions in a moment.”
What is a Mittendorf Dot?
Normal Finding = No pathologic significance
A small, circular congenital white opacity on the posterior lens capsule, classically nasal in location, which represents the anterior attachment of the hyaloid artery.
The hyaloid artery is present during gestation and typically regresses completely
What is the procedure for the anterior eye with Direct Ophthalmoscopy?
- Dial-up +10D with the wheel and look through the aperture at 10cm
- Adjust for your prescription only
- Use a large diameter aperture to examine the external features of the eye as it provides the largest field of view.
- This includes lashes, lid margins, palpebral conjunctiva and the sclera. Also, observe the colour of the iris and the size and regularity of the pupil.
- Position the ophthalmoscope about 15’ temporal to the patient’s line of sight
- Study the red reflex in particular as this provides an excellent way to detect any opacity of the media. Opacities will appear as dark areas against a bright red background
- Any dark patches or irregularity of the normal uniform red reflex denotes opacity of the cornea, anterior chamber or the vitreous.
- SLOWLY reduce positive power as you move through the media switch to the medium white beam.
What is the procedure for the posterior eye with Direct Ophthalmoscopy?
- Slowly move closer to the patient and at the same time gradually reduce the power of the lens in the wheel. The power of lens necessary to focus the fundus will depend on any patient and observer uncompensated refractive error
- Focus on the crystalline lens, the vitreous and the fundus
- Locate and examine Optic disc (0D if you and patient are emmetropic)
- Check rest of posterior pole.
- Look at the retinal blood vessels (the Veins are relatively large and dark red)
- Examine more Peripheral Retina
- Find Macula - switch to red-free aperture, return to the disc and move the beam temporally or get the patient to look straight into the light.
What are the common errors in Direct Ophthalmoscopy?
- Not getting close enough to an older patient with a small pupil
- Put your hand on patient’s shoulder or head for support
- Using the cup pallor instead of the deflection of the blood vessels as the determinant of the edge of the cupping.
- Not having patient view in different directions of gaze to obtain a better view of peripheral retina.
What is a Gunn Dot?
Normal Finding = No pathologic significance
Small, white dots which are sometimes visible overlying the large vessels near the optic nerve or the nerve fibre layers.
These are visible reflections of the internal limiting membrane, created by the footplate of the Muller cells.
What is another name for Floaters?
Muscae Volitantes
What is Hyaloid Remnant?
A rare condition in which there remain some parts of the hyaloid artery.
Posteriorly there may be a vascular loop or the thread of an obliterated vessel running forward from the optic disc and floating freely in the vitreous.
Anteriorly there may be some fibrous remnants attached to the posterior lens capsule and others sometimes floating in the vitreous.
What is Bergmeister Papilla?
A veil in front of the retina of the eye.
It is made of a conical mass of glial remnants that are the developmental tissue of the eye that has not been reabsorbed.
What is Myodesopsia
The perception of floaters in the vitreous humour.
What techniques can be used to assess the contour of the Fundus?
Irregularities in the contour of the retina e.g. cupping or swelling can be detected via:
1) A change in the power of the lens may be needed to focus on the structure at different levels.
2) If a streak of light is projected on to the fundus, irregularities of the contour may be observable as deviations.
3) Parallactic motion
How to assess the Optic Disc?
- Colour - Cup is paler
- Margins
- Cup size
- Presence of pigment, choroidal/scleral crescents
What is the principle of Parallax Motion?
Parallax can be used to determine distances.
Parallax is the displacement in the apparent position of an object viewed along 2 different lines of sight.
Near objects show a larger parallax
Further objects show a smaller parallax
What is foreshortening?
Portray an object as closer than it really is or as having less depth or distance as an effect of perspective or angle of vision.
How can Motion Parallax be used in Direct Ophthalmoscopy?
Can be used to work out where an opacity lies within the eye.
If you find possible irregularities, ask the patient to look up or down slightly.
- If the opacity appear to move ‘with’ the red reflex, then it lies anterior to the pupil plane i.e. the cornea or AC.
- If the opacities appear to move ‘against’ the red-reflex, then it must lie posterior to the pupil plane i.e. posterior crystalline lens or vitreous.
- If the opacity remains stationary, then it lies between pupil and lens.
If you note that the opacity is anterior e.g. the cornea as the patient to blink:
- If the opacity moves, it is floating in the tears e.g. mucus or debris.
- If it does not move, it is a True Corneal Opacity.
Where are Cortical Lenticular Opacities most commonly found?
Inferior Nasal aspect of the Crystalline lens
What is Magnification?
Process of enlarging the appearance of something, not the actual size.
What is the formula for Magnification?
M = (K’ / 4) x (1 / 1-wK)
K' = Dioptric length of the eye e.g. 60D K = Ocular Refraction e.g. -5.00 for 5D Myope w = Working distance in metres e.g. -0.025m
What is Field of View?
The field of view is the size of the illuminated retinal patch.
What is the formula for Field of View?
j (m) = g x (K-W/K’)
g = Pupil size W = Reciprocal of Working distance K' = Dioptric length of eye power e.g. 60D K = Ocular Refraction e.g. -5.00D for 5D Myope
What is the relationship between working distance and field of illumination?
If WD increases, the field of illumination decreases
What is the relationship between pupil size and field of illumination?
If pupil size decreases, the field of illumination decreases
If Rx is Hyperopic….
then Field of Illumination is increased
If Rx is Myopic…..
then Field of Illumination is decreased
High Myope =
Greater Magnification
Less Field of View
High Hypermetrope =
Less Magnification
Greater Field of View
