Chapter 7- Optometric instrumentation part 2 (1) Flashcards
What are the two types of ophthalmoscopy?
1- Direct ophthalmoscopy
2- Indirect ophthalmoscopy
What is direct ophthalmoscopy?
This is a method of examining the external eye, internal eye, and retina
Is ophthalmoscopy done on all patients?
Yes
By law, what should you perform when conducting an eye test?
You must perform an internal and external examination and carry out additional examinations as appear to be necessary to detect signs of injury, disease, or abnormality in the eye or elsewhere.
What is on the front of the direct ophthalmoscope?
A system of filters
What is down at the bottom of a direct ophthalmoscope?
A rheostat which controls the brightness
What should a practitioner do when doing direct ophthalmoscopy?
Remove their glasses, unless they have a high astigmatism or prescription.
What should a patient do when going through direct ophthalmoscopy?
They should remove their glasses.
However, if your patient has a high prescription, the image you’ll see on the ophthalmoscope will be quite disjointed so it’s best for them to keep them on.
When looking at the external eye, what power would you need on your lens wheel on the ophthalmoscope?
+12D
When you move closer to the patient and go through the eye, what should you do?
Reduce the lens power and examine the iris and anterior chamber.
The Px (patient) looks up, down, left, and right.
When examining the crystalline lens, what should you adjust the lens power to?
+8D
When looking behind the lens (optic media), what would you do?
You would reduce the plus power more and examine the vitreous (floaters)
How would you examine the optic disk?
1- Adjust the lens power to 0D
2- Patient looks straight ahead
3- Examine the optic disc- you do this by looking at the vertical C/D ratio (cup/disk ratio) and check the appearance of the disc margins
What is the C/D ratio?
The vertical diameter of the cup expressed as fraction of the vertical diameter of the optic disk. Written in decimal notation.
Why do we measure the C/D ratio?
Because this will help give us an indication as to whether a patient has glaucoma.
What are the blood vessel colours in the eye?
Arteries= lighter red and thinner
Veins= darker red and thicker
What two parts from the ophthalmic artery come into the eye through the optic nerve head?
The central retinal artery and the central retinal vein
Each then branches from the optic nerve head to serve four main quadrants of the retina.
These vessels provide the blood supply for the inner two thirds of the retina.
What type of zone is the macula?
The macular is an avascular zone- no blood vessels present and has the fovea at its centre.
What are the advantages of direct ophthalmoscopy?
1- The image you see is erect- the right way round
2- Good magnification
3- Portable
4- No eyedrops need to be put in
What are the disadvantages of direct ophthalmoscopy?
1- Small field of view
2- 2D image so you can’t tell the depth of anything
3- Difficult with small pupils
A panoptic ophthalmoscope is a form of what?
Indirect ophthalmoscopy
What are the advantages of a panoptic ophthalmoscope?
1- About 5x greater FoV- field of view
2- Good for amblyopes- someone with a lazy eye
What are the disadvantages of a panoptic ophthalmoscope?
1- It is 2D
2- Not superior to the direct ophthalmoscope for detecting diabetic retinopathy.
What is indirect ophthalmoscopy (volk lens)?
Uses a positive lens to form an aerial image which is real and inverted with a magnification of x2 and x5.
To perform volk, what do you need?
A slit lamp
