Direct Ophthalmascopy Flashcards
what is the purpose of ophthalmoscopy?
Examine retina or the fundus
• Only place in body that veins and arteries can be seen
- Provide clinically valuable information
- Both ocular conditions and systemic conditions
what are the advantages and disadvantages of direct ophthalmoscopy?
Advantages • Portable • Easy to use • Upright image • Magnification ~ 15x • Can use w/o dilation
- Disadvantages
- Small field of view
- Lack of stereopsis
- Media opacities can degrade image
what is the basic principle of direct ophthalmoscopy?
The light source is reflected through the
subject’s pupil to illuminate an area of
the fundus
• This illuminated area becomes the
object for the observation system of the
ophthalmoscope
what is the FOV of direct oph?
~6.5-10 deg
what are the 3 factors affecting FOV?
- Pupil size of patient
• Small pupil vs large pupil - Distance
• Examiner to sight hole
• Examiner to patient - Refractive error
• Hyperopes (shorter eye) ↑ FOV
• Myopes (longer eye) ↓ FOV
What power should we dial inside the lens
wheel when examining the fundus?
if you and/or the patient are uncorrected and
ametropic, the lens power necessary to focus on the
fundus will be the
sum of the refractive errors and your accommodative
state.
For example: If you are a -3 myope and your patient
is a -5 myope and neither of you are wearing glasses
or contact lenses during the assessment, you will
likely need a -8 lens to focus on the fundus.
Official (Open), Non-sensitive
LOOK AT CHART FOR FUNCTIONS OF APERTURES AND FILTERS
ok
what are some things to look out for in direct oph? DDNVCRMMF
- disc colour
- disk margins
- NRR
- venous pulsation
- CDR
- retinal vessels
- mid periphery
- macula + fovea
what is a normal and abnormal disc colour finding? what factors affect the disc colour?
normal healthy: orange-pink
abnormal: pale indicates ischemia
affected by optical media (e.g. cataract) or the instrument used (e.g. Optos Daytona).
what is a normal and abnormal disc margin finding? are all abnormal findings a cause of concern?
normal: distinct
abnormal: blurry
no. can be a normal variation caused by tilted disk
what is a normal and abnormal NRR finding? are all abnormal findings a cause of concern?
normal: following the ISNT rule
abnormal: Thinning of the NRR indicates possible glaucomatous optic disc. In addition, there might be notching
(typically at the superior-temporal or inferior-temporal regions)
what is venous pulsations?
rhythmic pulsations occurring on the central retinal veins due a change in the
pressure along the retinal vein as it traverses the lamina cribrosa.
what is an abnormal CDR finding?
CD ratio >/= 0.7
CD ratio enlargement >/= 0.2
CD ratio asymmetry >/= 0.2
**this are signs of glaucoma!
.what do we look for in the retinal vessels? what is the norm?
• An assessment of the AV ratio (thickness of A compared to V) usually is conducted
after the second bifurcation of the vessels.
The normal A/V ratio is 1:2, 2:3.
• Tortuosity may be a congenital variation or indicate the presence of vascular pathology
(e.g. hypertensive retinopathy)
.what is the mid periphery?
The mid-periphery refers to the regions of the posterior pole outside the macula area.
some of the commonly seen lesions can be normal physiological variation or abnormal in a diseased eye.
