Final answer:
The description of a 'curtain being drawn over the eye' is symptomatic of retinal detachment, an eye condition that requires immediate medical attention to prevent permanent vision loss.
Step-by-step explanation:
The phrase “classically described as a curtain being drawn over the eye from the top to the bottom” refers to a common symptom of retinal detachment, a serious eye condition. Retinal detachment occurs when the retina, which is the light-sensitive layer of tissue at the back of the eye, becomes separated from its underlying supportive tissue. When this happens, it can cause a shadow or curtain-like effect over the field of vision, as the retina can no longer efficiently convert images into neural signals for the brain. Immediate medical attention is crucial as retinal detachment is a medical emergency that can lead to permanent vision loss if not treated promptly.