Correct answer: vision
Explanation:
The human eye functions based on the principle of the sensation of vision, which involves the detection of light and its conversion into electrical signals by the retina. These signals are then interpreted by the brain to form images.
The eye is sensitive to visible light, and vision is made possible due to the focusing of light rays onto the retina through the cornea and lens.
Hence, the correct answer is: vision.
Tara's grandmother is 70 years old and has a passion for embroidery. She faces difficulty in threading the needle as the eye of the needle appears blurred. The ophthalmologist diagnosed it as an age-related disorder. 
(a) Name the eye disorder she is suffering from.
(b) How can the above defect be corrected?
(c) Where is the image formed in the above disorder?