Indirect Ophthalmoscopy Flashcards
What is the image formed in indirect ophthalmoscopy?
Real
vertically and horizontaly invertedW
here is the image located?
BEtween observer and lens
At or near the second principal foxus
40-50cm from the observer who must accommodate to view the image
How does emmetropic patient eye affect image?
Image size same regardless of position of lens
How does myopic patient eye affect image?
Image size increases as lens moves away from eye and reduces nearer eye (image within 2nd principal focus)
How does hypertropic patient eye affect image?
Image size decreases as lens moves away from eye and increases nearer eye
What doe stronger condensing lenses produce? Angulation, field of view, laser spot magnification
Less angular magnification
Increased field of view
Increase in laser spot magnification
What do weaker condensing lenses produce? Angulation, field of view, laser spot magnification
More angular magnification
Less field of view
Less laser spot magnification
What affects field of view?
Size of observers pupil
Diameter of condensing lens
Power of condensing lens
How does size of observer pupil affect field of view?
Larger pupil - greater field
How does diameter of condensing lens affect field of view?
Larger diameter = greater field of view
How does power of condensing lens affect field of view?
Higher power = greater field of view but less magnification
How does field of view change with patients pupils size
No change in field of view
Patient pupil size only affects field of illunication
What are advantages of indirect compared to direct ophthalmoscopy
Binocular view
Wider field of view
(25 compared to 6 degrees with direct)
DIsadvantages of indirect
Less magnification
Image inverted
Image in direct opahthlmoscopy
Real
Erect
What is angular magnification of direct ophthalmoscopy
in emmetropic eye?
15x
How does image size change in myopia and hypermetropia in direct ophthalmoscopy?
Myopia = increased
Hypermetropia = reduced
How wide is fiedl of view in direct vs indirect
6 degrees
vs
25 degrees
How does field of view change with myopia, hypermetropia, pupils size, position of patient in direct ophthalmoscopy
Decreases with myopia
Increases with hypermetropia
Increases with larger pupil size
Increases when the observer moves toward the patient
