D. Retinal detachment.
The instrument shown in the picture above represents Placido disc .
Keratoscope ,also known as Placido’s disc
- It is an ophthalmic instrument for detecting abnormal curvature of the the cornea of the eye.
- It consists of a black disc that is marked with concentric white rings at whose centre is a small lens through which the ophthalmologist can observe the patient’s cornea.
- When using this device the practitioner observes the reflections of the white rings in the patient’s cornea.
- In the case of a normally-shaped cornea, those reflections are also a set of concentric rings.
- If the patient is suffering from astigmatism or from a corneal dystrophy or Keratoconus, the rings will be distorted.