Q. 74 B
What is night blindness? What causes night blindness?
Answer :
Night blindness is the inability to see properly at night or in poor light. In scientific terms, it is called as "nyctalopia".
The following factors cause night blindness:
1) The deficiency of Vitamin A (retinol) in the diet of a person for a considerable time can lead to the disease called night blindness.
2) The disorder in which the rod cells in the retina gradually lose their ability to respond to the light.
3) It can also happen due to cataract, or clouding of the eye’s lens.
4) Usher syndrome can also cause night blindness, which is a genetic condition that affects both hearing and vision.
5) Nearsightedness or blurred vision can also cause night blindness.
Rate this question :






















Write down the names of parts of the eye in the blank spaces shown in Fig. 16.10.
NCERT - Science Exemplar
Explain the process which enables us to perceive motion in a cartoon film.
NCERT - Science ExemplarWhich of the following statements is correct regarding rods and cones in the human eye?
NCERT - Science ExemplarIn the figure of the human eye (Fig.16.5), the cornea is represented by the letter
NCERT - Science Exemplar
Explain what happens to the size of the pupil of our eye in bright.
All in One - ScienceWhat happens to the size of the pupil of our eye in bright?
All in One - ScienceName the part of our eye that gives it as distinctive colour.
All in One - ScienceWhat are the functions of the following parts of the eye?
(a) Iris
(b) Eye-lens
(c) Ciliary muscles
(d) Retina
(e) Optic nerve
Lakhmir Singh & Manjit Kaur - ScienceDraw a labelled diagram of the human eye. Label the following parts on this diagram: Cornea, Iris, Pupil, Ciliary muscles, Eye-lens, Retina, Optic nerve, Blind spot.
Lakhmir Singh & Manjit Kaur - ScienceWhich of the following is not a part of the human eye?
Lakhmir Singh & Manjit Kaur - Science