Binocular Indirect Ophthalmoscopy- lecture 1 Flashcards
Indirect ophthalmoscopy involves making the eye highly _____ by placing a ____ power ____ lens where in accordance to the eye?
-myopic
-high
-convex (+13D to +30D)
In front of the eye
Indirect ophthalmoscopy creates what kind of image in front of the lens?
Real, inverted, and laterally reversed
Why is the technique called indirect?
B/c the fundus is seen through a condensing lens
Where is the image formed when performing indirect ophthalmoscopy?
Close to the principle focus of the lens, between the lens and the observer
Preliminary step when you perform BIO
Explain procedure to patient
Wash your hands
How should the headband fit for BIO?
Comfortably without undue tightness
Where should oculars be with the BIO on?
Straight and level
How do you want the eyepieces adjusted on BIO for maximum field of view?
As close to the eyes as possible, with a slight pantascopic tilt; avoid resting on bridge of nose
When you turn your BIO on, what do you want your rheostat at?
To about 50%
When you turn your BIO on, what size do you want your aperture set to?
Largest size
When you turn your BIO on, what filters do you want in place?
None
When you turn your BIO on, what do you want to set the mydriatic pupil setting to?
Maximum dilated
What adjustment knobs are on the right of your BIO?
Clear, red-free, yellow and blue filters
What adjustment knobs are on the left of your BIO?
3 aperture sizes plus diffuser
What do you view when adjusting your interpupillary distance on BIO?
View wall or other object (your thumb) at roughly 40 cm
How do you adjust interpupillary distance for BIO?
- view obj at 40 cm
- monocularly for each eye until the object is centered in the field of view
- with both eyes open, a single clear binocular image of the object should be obtained
If diplopia is encountered, what do you do to adjust the BIO?
Make further adjustments to the PD until a fused img is achieved
How do you adjust the mirror height?
Adjust light vertically using the mirror until it occupies the upper half of the field of view
Available powers of condensing lenses
14D to 40D
Power of lens that is a good balance b/w magnification and field of view
20D
What general power of lenses offer a greater FOV and can aid with examination through small pupils?
Higher power lenses
The power of the condensing lens determines these 3 things:
Working distance
Magnification
Field of view
As the power of the condensing lens decreases, what happens to the field of view, working distance, and magnification?
FOV dec
WD inc
Mag inc
A +30 lens power has what magnification?
2x
A +30 lens power has what FOV?
60 degree
A +30 lens power has what stereopsis?
1/2
A +30 lens power has what working distance from cornea
26 mm
A +20 lens power has what magnification?
3.25x
A +20 lens power has what FOV?
40 degrees
A +20 lens power has what stereopsis?
3/4
A +20 lens power has what working distance from cornea?
47 mm
A +14/+15 lens power has what magnification?
4.17x
A +14/+15 lens power has what FOV?
30 degree
A +14/+15 lens power has what stereopsis?
1
A +14/+15 lens power has what working distance from cornea?
72 mm
What power of lens is used to obtain a panoramic view when detail and stereopsis are not as important, and used with a small pupil?
30D
Is your working distance less or more with a 30D condensing lens?
Less
What power of lens is most widely used, since it provides an adequate field of view, stereopsis and magnification?
20D
What power of condensing lens is most useful for detailed view of the macula or optic disc or for determining elevation of the retina in shallow retinal detachment?
15D
3 important patient preparations for performing BIO, after washing your hands and explaining the test to the pt?
- dilation of eyes
- dark room when possible
- have pt chair fully reclined, enabling practitioner to move around the pt and hence gaining a full 360 degree traverse of the fundus
If you are looking at the super quadrant, where should you be looking from?
180 degrees in the opposite direction (inferiorly to the pt)
What position do you recline you patient to?
Supine position (or in upright seated position) with the height to about waist high or slightly lower
How do you hold the condensing lens?
- grasped b/w tip of flexed index finger and ball of thumb
- extended 3rd finger holds pt’s lid (thumb of opposite hand is used to retract the lid not held by the 3rd finger)
- -3rd finger acts as a pivot that enables the observer to tilt the lens in all planes merely by rocking the forearm on the tip of the finger
How do you obtain a view of the fundus with the lens?
- Place lens close to eye to that lids, conj, and iris may be seen
- Center pupil in lens
- Gradually move lens away from pt, making pupil magnified until it fills the entire area of the lens
If the img of the fundus does not fully fill the lens, what should you do?
- move the condensing lens closer to the eye, recenter the pupil, then lift it again
- adjust your head tilt to better distribute the light entering the patient’s eye
- adjust the ophthalmoscope mirror up/down
- adjust condensing lens laterally
- adjust tilt of condensing lens
- check for bino vision; readjust if necessary
In which directions do you adjust the ophthalmoscope mirror and condensing lens if the img of the fundus does not fully fill the lens?
Mirror: up/down
Lens: laterally
Where must the pupil be located in order to maintain a clear view of the fundus?
Pupil must be kept centered in lens at all times or fundus view is lost
What do slight movements of the eye or hand off the pupil cause when observing the fundus?
Distortion, shadows, or complete loss of view
How do you want your arm and head when observing the fundus?
Keep arm extended and head at arms length from the lens
What can slight adjustments in working distance effect?
Changes in magnification, but larger changes will produce difficulties with accommodation, convergence, and possibly diplopia
Slight tilting of the lens will displace reflections. What will excessive tilting of the lens induce?
Astigmatism that will distort the fundus img
Light intensity that’s adequate for most needs?
Moderate light intensity
Limit exposure to BIO light to how many seconds at a given time?
30 seconds or less
2 options you can give the pt to refresh their tear film
- give pt a chance to blink to refresh tear film
- use artificial tears to aid in comfort (mostly for elderly patients)
Proper room lighting for BIO?
Dark enough for you to achieve sufficient contrast
-avoid too much ambient light
What light intensity do you start with when using BIO?
Don’t begin with the brightest light; once the pt is accustomed to the light, you can gradually turn it up to double-check a selected area
