Choroid layer of mammalian eye

Options

A. focuses the object
B. serves as refractive surface
C. is highly vascularised and pigmented
D. control the amount of light that falls on retina

Answer

### Step-by-Step Solution:

1. **Understanding the Choroid Layer**: The choroid is a layer of the eye located between the retina and the sclera. It is primarily responsible for providing nourishment to the outer layers of the retina through its extensive network of blood vessels.

2. **Evaluating the Options**:
- **Option 1**: "Focuses the object" - This option is incorrect. The focusing of objects is primarily done by the lens of the eye, not the choroid layer.
- **Option 2**: "Serves as refractive surface" - This option is also incorrect. The cornea is the main refractive surface of the eye, not the choroid.
- **Option 3**: "Highly vascularized and pigmented" - This option is correct. The choroid is indeed highly vascularized and contains pigment, which helps absorb excess light and prevent scattering.
- **Option 4**: "Controls the amount of light that falls on the retina" - This option is incorrect. The pupil, which is controlled by the iris, regulates the amount of light entering the eye, not the choroid.

3. **Conclusion**: Based on the evaluation of the options, the correct answer regarding the choroid layer of the mammalian eye is **Option 3: Highly vascularized and pigmented**.