What condition occurs when parallel rays of light focus at a point just in front of the retina in an unaccommodated eye?

The condition where parallel rays of light focus at a point just in front of the retina in an unaccommodated eye is known as myopia, commonly referred to as nearsightedness. Myopia occurs when the eyeball is too long or the cornea has too much curvature. As a result, light rays entering the eye converge to a focal point before they reach the retina, causing distant objects to appear blurry while nearby objects can be seen clearly.

In contrast, hyperopia occurs when light focuses behind the retina, leading to difficulty seeing close objects. Astigmatism is caused by an irregular curvature of the cornea or lens, resulting in distorted or blurred vision at all distances. Presbyopia is an age-related condition where the eye's lens loses elasticity, making it difficult to focus on close objects, typically affecting those over the age of 40. Understanding these conditions helps in recognizing how different refractive errors affect vision and the necessary corrective measures.