Stokes lens

Stokes lens also known as variable power cross cylinder lens[1] is a lens used to diagnose a type of refractive error known as astigmatism.

Stokes lens
SynonymsStokes' lens
Test ofAstigmatism

Lens design

The Stokes lens also known as variable power cross cylinder lens, in its standard version, is a lens combination consisted of equal but opposite (one plano-convex and other plano-concave) power cylindrical lenses attached together in a way so that the lenses be rotated in opposite directions.[2][3] When the axes are parallel, the two powers cancel each other out to achieve the resulting power zero; When the axes are vertical, a sphero-cylindrical lens with maximum power is obtained.[3]

Uses

Stokes lens is a lens used to diagnose and measure astigmatism.[4][5]

Adaptations

American ophthalmologist Edward Jackson revised the Stokes lens concept and made a cross cylinder lens to refine power and axis of astigmatism.[2] This lens combination is known as Jackson cross cylinder.[2] Based on the Stokes lens, James P. Foley and Charles E. Campbell made a variable power astigmatic lens which is combination of two identical cylindrical powers instead of equal and opposite powers.[2][6]

History

In 1837, English mathematician and astronomer George Biddell Airy invented the cylindric lens and used it to correct astigmatism.[3] Irish English physicist and mathematician George Stokes invented Stokes lens in 1849.[3]

References
  1. Ferrer-Altabás, Sara; Micó, Vicente (10 April 2020). "Characterization of a compact low-cost Stokes lens for astigmatism compensation in optical instruments". Applied Optics. 59 (11): 3347–3352. Bibcode:2020ApOpt..59.3347F. doi:10.1364/AO.386247. ISSN 2155-3165. PMID 32400444. S2CID 216493169.
  2. Ferrer-Altabás, Sara; Thibos, Larry; Micó, Vicente (14 March 2022). "Astigmatic Stokes lens revisited". Optics Express. 30 (6): 8974–8990. Bibcode:2022OExpr..30.8974F. doi:10.1364/OE.450062. ISSN 1094-4087. PMID 35299337. S2CID 245785084.
  3. Wunsh, Stuart E. (10 July 2016). "The Cross Cylinder". Ento Key.
  4. "Stokes lens". TheFreeDictionary.com.
  5. Dennett, WS (1885). "The Stokes' Lens for Measuring Astigmatism". Transactions of the American Ophthalmological Society. 4: 106–10. PMC 1326669. PMID 25258975.
  6. Foley, James; Campbell, Charles (1999-10-01). "An Optical Device with Variable Astigmatic Power". Optometry and Vision Science. 76 (9): 664–7. doi:10.1097/00006324-199909000-00025. PMID 10498009.
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