- Lenses in the 9th century
Corrective lenses were said to be used by Abbas Ibn Firnas in the 9th century,  who had devised a way to produce very clear glass. These glasses could be shaped and polished into round rocks used for viewing and were known as reading stones.
Abbas Ibn Firnas(1) (810 – 887 A.D.),also known as Abbas Qasim Ibn Firnas, Was a muslim Berber polymath: an inventor, engineer, aviator, physician,Arabic poet,and Andalusian musician. He was born in Izn-Rand Onda, Al-Andalus (today’s Ronda,Spain),and lived in the Emirate of Cordoba.He is known for an early attempt at aviation.  
Ibn Firnas designed a water clock called Al-Maqata,devised a means of manufacturing colorless glass, he invented various glass planispheres, Made corrective lenses(“reading stones”) , developed a chain of rings that could be used to simulate the motions of the planets and stars, and developed a process for cutting rock crystal that allowed Spain to cease exporting quartz to Egypt to be cut.  
Figure 8: Abbas Ibn Firnas, reading stone.
-Lenses in the 10th century
Ibn Sahl used what is now known as Snell’s law to calculate the shape of lenses.  Ibn Sahl (c.940-1000) (1)was a Muslim Persian mathematician
, Physicist and optics engineer of the Islamic Golden Age associated with The Abbasid court of Baghdad.Ibn Sahl’s 984 treatise On Burning Mirror and Lenses sets out his understanding of how curved mirrors and lenses bend and focus light. Ibn Sahl is credited with first discovering the law of refraction, usually called Snell’s Law.   He used the law of refraction to derive lens shapes that focus light with no geometric aberration , known as anaclastic lenses.
Figure 9: Ibn Sahl (Snell,s low). Figure10: Ibn Sahl,s work on
refraction and optics