Microscopes were created in the late 15th century as people started to experiment with telescopes. The way that a telescope makes distant items closer is a lot like how a microscope works. Both provide gentle suction on the eye's pupil and distort the eye so the image that would normally appear on the center back of the eye is spread around almost the entire inside surface of the eyeball.
This distortion of the eye quickly reverses once the user pulls back from the microscope but does mean that the user of a microscope has to align their eye just right above the aperture of the microscope to see anything. The distortion factor is listed on the microscope and misaligning your eye can cause irritation of the eye and the weird dark or blackout of the image being viewed.
The brighter the image the more distortion occurs. Thus looking at the sun through a telescope is discouraged. The intensity of the sun's rays can cause the eye to bulge out of its socket and be permanently damaged.