Optics II Final Examination And Already
Passed Answers Graded A+.
History of lens development - Answer 1. flat lenses (1200-1800)
2. periscopic lenses (1800s)
3. six-base meniscus (1890-1960s)
4. corrected curve (early 1900s to now)
5. minus cyl form torics (1960s)*
6. aspherics (early to mid 20th century to now)
7. atorics (late 20th century to now)
Flat lenses - Answer 1200-1800
- biconvex or biconcave; poor vision through the periphery
History of periscopic lenses - Answer 1800s
- had a -1.25D concave back surface that improved peripheral vision
History of six-base meniscus lens - Answer 1890-1960s
- had a -6.00D base curve that improved peripheral vision even more than periscopic lenses
History of corrected curve - Answer Early 1900s to now
- large number of base curves, depending on power, chosen to minimize or correct off-axis
averrations
History of minus cylinder form torics - Answer 1960s
- switched single vision lenses from plus cylinder form (toric on front) to minus cylinder form
(toric on back***), since back surface torics were also being used for multifocals
History of aspheric lenses - Answer Early to mid 20th century to now
- initially were used only for high plus lenses (ex. post cataract), but now used for lower power
single vision, high index plastic
, History of ophthalmic lens shapes - Answer - generally made in meniscus form
- positive and negative meniscus***
- both lens sides have curvature
Meniscus form* - Answer Front surface is convex and back surface is concave
Positive meniscus* - Answer Convex surface has more curvature than the concave surface
- overall power is positive
Negative meniscus* - Answer Concave surface has more curvature than the convex surface
- overall power is negative
Lens blanks - Answer Before a lens has been edged (to fit into frame opening)
- can be finished or semi-finished
Finished stock lenses* (lens blank) - Answer Both surfaces are finished and polished
- AKA 'uncuts' since they have not been edged
- typically single vision lens blanks
Semi-finished lens blank - Answer One surface is finished and polished while the other surface
has been left unfinished to have the prescription ground onto it
Spherical lens definition - Answer There is one power in all meridians of the lens
- both convex (front) and concave (back) surfaces are spherical surfaces
Toric lens definition - Answer The power varies between a minimum and maximum in the two
principal meridians of the lens
Modern toric lenses - Answer The convex (front) surface is spherical and the concave (back)
surface is toric, varying gradually in concave power from minimum to maximum
Passed Answers Graded A+.
History of lens development - Answer 1. flat lenses (1200-1800)
2. periscopic lenses (1800s)
3. six-base meniscus (1890-1960s)
4. corrected curve (early 1900s to now)
5. minus cyl form torics (1960s)*
6. aspherics (early to mid 20th century to now)
7. atorics (late 20th century to now)
Flat lenses - Answer 1200-1800
- biconvex or biconcave; poor vision through the periphery
History of periscopic lenses - Answer 1800s
- had a -1.25D concave back surface that improved peripheral vision
History of six-base meniscus lens - Answer 1890-1960s
- had a -6.00D base curve that improved peripheral vision even more than periscopic lenses
History of corrected curve - Answer Early 1900s to now
- large number of base curves, depending on power, chosen to minimize or correct off-axis
averrations
History of minus cylinder form torics - Answer 1960s
- switched single vision lenses from plus cylinder form (toric on front) to minus cylinder form
(toric on back***), since back surface torics were also being used for multifocals
History of aspheric lenses - Answer Early to mid 20th century to now
- initially were used only for high plus lenses (ex. post cataract), but now used for lower power
single vision, high index plastic
, History of ophthalmic lens shapes - Answer - generally made in meniscus form
- positive and negative meniscus***
- both lens sides have curvature
Meniscus form* - Answer Front surface is convex and back surface is concave
Positive meniscus* - Answer Convex surface has more curvature than the concave surface
- overall power is positive
Negative meniscus* - Answer Concave surface has more curvature than the convex surface
- overall power is negative
Lens blanks - Answer Before a lens has been edged (to fit into frame opening)
- can be finished or semi-finished
Finished stock lenses* (lens blank) - Answer Both surfaces are finished and polished
- AKA 'uncuts' since they have not been edged
- typically single vision lens blanks
Semi-finished lens blank - Answer One surface is finished and polished while the other surface
has been left unfinished to have the prescription ground onto it
Spherical lens definition - Answer There is one power in all meridians of the lens
- both convex (front) and concave (back) surfaces are spherical surfaces
Toric lens definition - Answer The power varies between a minimum and maximum in the two
principal meridians of the lens
Modern toric lenses - Answer The convex (front) surface is spherical and the concave (back)
surface is toric, varying gradually in concave power from minimum to maximum
