The three common refractive defects of vision mentioned are (i) myopia or near-sightedness, (ii) hypermetropia or farsightedness, and (iii) presbyopia.

When the eye gradually loses its power of accommodation, a person cannot see objects distinctly and comfortably, leading to blurred vision. This is due to refractive defects of the eye.

Cataract is a condition where the crystalline lens becomes milky and cloudy, causing partial or complete loss of vision. Vision can be restored through cataract surgery, a medical procedure that replaces the cloudy lens with an artificial one.

For a young adult with normal vision, the near point is about 25 cm. To see an object comfortably and distinctly, it should be held at approximately 25 cm from the eyes.

The minimum distance at which objects can be seen most distinctly without strain is called the least distance of distinct vision, also known as the near point of the eye.