Direct Ophthalmoscope Flashcards
Image formed by direct ophthalmoscope
Direct - virtual, erect
What is the field of view in direct ophthalmoscope
About two disc diameters
Retina can be examined to equator
Which ophtahlmoscopy is affected by patients refractive status?
Direct
What is the area of retina viewed in direct ophthalmoscopy dependent on
Size of pupil or size of hole in mirror - whichever is smaller
- Field of view increases with dilated pupil - examiner and subject
Image formed in indirect ophahtlmoscopy
Real image
Vertically and horizontally inverted
Formed between the condensing lens and the observer
What is the field of illumination dependent on in indirect ophthalmoscopy
LArgest in myopia
Smallest in hypermetropia
limited by subjects pupil size
What has a greater field of view
Indirect ophthalmoscopy has grater field of viewW
Which gives greater magnification? What is the magnification of direct ophthalmoscopy?
Direct
x15 in emmetropic patient
Which lens gives wider field of view in indirect?
Higher power lens = wider field of view
28D larger field of view
More magnification in indirect lens?
Higher power lens = less magnification
20D - more magnified
How is magnification of condensing lens determined
60/power
eg 20D = 3x magnification
Which power lens needs to be held further from eye
Lower lens further from eye
Held so that distance where both patient and examiner pupil are conjugate foci - light from one pupil brought to focus at other pupil
