Final answer:
Hypertonic myopia occurs when the ciliary muscle contracts excessively, causing the lens to become thicker and resulting in blurred distance vision. Pseudomyopia is a temporary form of myopia that can be caused by prolonged near work or excessive accommodation.
Step-by-step explanation:
Myopia, also known as nearsightedness, is a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than on the retina. There are two types of myopia: hypertonic and pseudomyopia.
Hypertonic Myopia:
Hypertonic myopia occurs when the ciliary muscle, which controls the shape of the lens, contracts excessively. This excessive contraction causes the lens to become thicker, resulting in an increase in the refractive power of the eye. As a result, light rays from distant objects are overly bent and focused in front of the retina, leading to blurred distance vision.
Pseudomyopia:
Pseudomyopia is a temporary form of myopia that can occur due to factors such as prolonged near work or excessive accommodation. Accommodation is the ability of the eye to adjust its focus to see objects at different distances. Prolonged near work, such as reading or using electronic devices, can cause the ciliary muscle to remain in a contracted state for an extended period. This sustained contraction causes the lens to become thicker, leading to blurred distance vision. However, once the ciliary muscle relaxes, the lens regains its normal shape, and the myopia resolves.