A clinic tests two laser settings using an optical model with the same focusing defect as a person's eye. The person sees nearby objects clearly, but distant objects are blurred.
Light from a distant object is used in each test.
| Test | Shape of cornea compared with before treatment | Position where the light is focused |
|---|---|---|
| Before treatment | unchanged | 1.6 mm in front of the retina |
| Laser setting A | slightly flatter | 0.2 mm in front of the retina |
| Laser setting B | much flatter | 0.8 mm behind the retina |
Identify the person's eye defect. Explain which laser setting should be chosen to give the better correction, including how changing the shape of the cornea changes the position of the focus.
135 exam-style questions on OCR GCSE Biology 3.1 Coordination and control – the nervous system, covering 3.1.1 Structure of the nervous system, 3.1.2 Coordinated response, 3.1.3 The reflex arc, 3.1.4 Structure of the eye, 3.1.5 Defects of the eye, 3.1.6 Structure and function of the brain, 3.1.7 Difficulties of investigating brain function, and 3.1.8 Limitations in treating nervous system damage. Each one has a worked solution and a mark scheme showing where the marks go.