Sight savers : first operation to remove cataracts 10th century

first operation to remove cataractsDid you know the first operation to remove cataracts was carried out as early as the 10th century in Iraq. Muslims also established the first apothecary shops and dispensaries, founded the first medieval school of pharmacy, and wrote great treatises on pharmacology.
Muslim inherited two explanations of vision. Ptolemy and Euclid both believed that vision was produced by the emission of light from the eyes, but their theory did not provide a reasonable explanation of perspective, the effect whereby the apparent size of an object depends upon its distance from the observer. Aristotle, Gallen and their followers stood for the so called `intromission,’ something entering the eyes representative of the object, but again did not provide proper empirical explanation.
Al-Kindi was the first to question Euclid’s theory of emission and to put some alternative suggestions, for example, asserting that a visual cone is not formed of discrete rays as Euclid has stated, but appears as a volume of continuous radiations. Rays are three dimensional and form a continuous radiant cone, a critique which prepared the way for Ibn al-Haytham’s distinction between light rays and the straight lines along which they are propagated. He also explained how the light rays come in a straight line. His two works on geometrical and physiological optics were used by the English Roger Bacon (1214-1292) and the German physicist Witelo.
The proper scientific explanation had to wait until the arrival of Ibn al-Haitham (965-1039 CE), known in the West as Al-Hazen, who once and for all explained how we see, through light reflecting off an object and entering the eye. He backed this up with many rigorous experiments, establishing the scientific foundations for modern optics, combining the `mathematical’ approach of Euclid and Ptolemy with the `physical’ principle favoured by the natural philosophers.
During his light and vision experiments, Ibn Al-Hayhtam discovered the camera obscura phenomenon. He went to explain that we see objects upright and not upside down, as the camera does, because of the connection of the optic nerve with the brain which analyses and defines the image.