Chapter 8- Optometric instrumentation part 3 Flashcards
What is visual fields also known as?
Perimetry
What is a visual field?
The area of the surroundings which is visible at one time
When would you do a visual fields test?
1- If a patient has glaucoma
2- If there is family history of glaucoma
3- If a patient is over the age of 40 years
The visual field is a projection of what?
The visual pathway in space
What produces visual field defects?
Lesions at any stage of the visual pathway
What is a lesion?
An area of abnormal tissue
The visual pathway is prone to damage from a variety of agents such as:
1- Trauma
2- Pressure from neoplasms- meaning tumour
3- Vascular accidents such as stroke
With both eyes open, how many degrees can you see across?
200 degrees across
In the area of overlap between the left eye and right, how many degrees across can you see?
120 degrees across
With both eyes open, how many degrees can you see up and down?
60 degrees up
70 degrees down
What is the reason why you can only look 60 degrees up?
Because of the eyebrows
Visual test fields can be divided into:
1- Central visual fields- looks at the central 30 degrees
2- Peripheral visual fields- looks at the area beyond 30 degrees
What are the properties of the central retina?
Made up of a high density of cones which is highly concentrated in the fovea.
There is a low density of rods
Has good visual acuity
Good colour vison
For vision at higher light levels (photopic)
What are the properties of the peripheral retina?
Low density of cones
Higher density of rods
Poor visual acuity
Poor colour vision
Suited for vision at lower light levels (scotopic)
What are the two types of visual assessment?
1- Static- stationary
2- Kinetic- involves a moving target
