| Date | November 2017 | Marks available | 2 | Reference code | 17N.3.HL.TZ0.05 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Explain | Question number | 05 | Adapted from | N/A |
Question
A cataract is a clouding of the lens in the eye, resulting in blurred vision.
[Source: Cataract in Human Eye, Rakesh Ahuja, MD (https://en.wikipedia.org/wiki/Cataract#/media/File:Cataract_in_human_eye.png)]
Explain the use of a local anesthetic during surgery to remove the cataract.
[2]
b.
Describe red-green colour blindness.
[2]
c.
Markscheme
a. reduction/elimination of pain
OR
to block sensory perception
b. blocks synaptic transmission between «sensory neurons and CNS»
OWTTE
c. allows patient to remain aware
d. prevent reflex causing blinking/eye movement
OWTTE
[Max 2 Marks]
b.
a. sex/X-linked «genetic trait»
b. results from absent/defective cone cells
c. cannot distinguish between red and green
[Max 2 Marks]
c.
Examiners report
[N/A]
b.
[N/A]
c.
