direct ophthalmoscopy Flashcards
What is the PURPOSE of ophthalmoscope?
to assess the the ocular media and fundus
to observe the anterior segment of the eye
What is the PRINCIPLE of opthalmoscope?
the examiner gets in the way of the incident light as retina is illuminated.
What are the 2 FEATURES of ophthalmoscope?
1- Illumination system is with a reflector
2- the viewing system is with neutralising lenses
How is an ophthalmoscope constructed?
- light from batteries at is reflected at 90º using a two-way mirror at 45º in the head portion.
- the examiner looks through the hole in the mirror
- if patient and examiner are both emmetropic, rays from patients funds are parallel and focused onto the observers retina.
State 7 requirements/ properties for using a direct opthalmoscope?
- dim room illumination
- close working distance
- image is erect and real
- no dilation
- monocular (RE with RE)
- limited field of view (2 disc diameters)
- select appropriate viewing apertures
describe the retina with a direct ophthalmoscope?
- can’t see photoreceptors
- gives rise to physiological blind spot
- exit route for optic nerve
How can you carry out a systematic examination?
- check the overall view of the eye
- quality of fundus reflex
- assess disc appearance and macula
- work along major blood vessels - repeat foreach quadrant
State the 6 possible variations between eyes?
- tigroid/ tessellated fundus
- myopic/scleral crescents
- pigmented disc margins
- physiological cup
- choroidal vessels
- cilio-retinal vessels
what is the difference between a caucasian and an asian fundus?
Caucasian funder is a red coloured one and asian one is a darker/ brown coloured background fundus.
State all 7 difficulties that can arise during fundus examination?
- small pupils
- uncooperative patient
- bright room
- poor ophthalmoscope
- High opacity
- high myope
- high astigmatism
