discussion about Aspheric lens, fitting, indication,advantage and Disadvantages with traditional aspheric lens,need of Asphericity,Aspheric Lens Design, identification, troubleshooting

1. Aspheric Lenses
-ANURAG SHUKLA
FELLOW OPTOM.
SHROFF CHARITY EYE HOSPITAL ,DELHI

2. What we expect from spectacle
lens?
 Good Optics
 Cosmesis- Natural Appearance
 Light in weight
 Thin
 Natural vision

3. Disadvantages with traditional
lens designs
 Lens become thicker when improving
optics
 Optics hampered when reducing thickness
 Wearers eyes appear bulgy in high plus
powers
 Difficult to fit into frames

4. Why do we need Asphericity?
 Offers slimmer profile
 Superior Optics
 Natural Appearance
 Lighter weight

5. Whom should I suggest?
 Prescriptions more than +/- 3.00 DS
(Need your input)
 Unsatisfied spectacle wearer
 Person requiring good peripheral vision
 Person expecting natural appearance with
their spectacles.
 Persons who like to use high end products

6. Video - Spherical Vs. Aspherical

7. Something which we must
know
 Spectacle lenses inherently produce following
aberrations which can be taken care by applying
asphericity
◦ Oblique astigmatism(only with aspherics)
◦ Spherical Aberration (with aspherics as well as
hi index)
◦ Distortion (with aspherics as well as hi index)

8. Oblique Astigmatism
 Lens faces oblique astigmatism when
viewing obliquely through lens

9. Distortion

10. Aspheric Lens Design
 Change in radius of curvature from center to
periphery
 Symmetric axially or rotationally
 Atoric surface - Different asphericity applied in
two different meridians

11. Various options available
 Materials available: Cr39, Trivex,
Polyurethane
 Index available: 1.498, 1.53, 1.67, 1.74
 Available in: Single vision and
Progressives, not very common in bifocals
 Tints: Available in clear and photo
chromatic tints
 For available power range: Need to refer
to individual company catalogue

12. Challenges for us
 How to recommend?
 How do we fit?
 How do we identify aspheric?

13. How to recommend?
 Identify the consumers for whom it will be
really beneficial

14. Before suggesting a product
 Check
◦ Patients expectations
◦ Type of lens he is already wearing
◦ Base curve of the previous lens
◦ Previous lens power
◦ Is there a change in the prescription?
◦ Availability as per prescription

15. Be Prepared for these FAQ’s?
 How much thinner it will be?
 How much lighter it will be?
 Does it come in all lens materials?
 Is it available in bifocals?
 Do I need to select any special frame?

16. How to fit Aspheric
 Pentascopic tilt
Monoc
ular
PD
Monoc
ular
PD
3229
61
Take monocular PD’s
Rule of thumb for pantoscopic tilt
Lower Optical Centre by 1 mm
for 2 degrees of pantoscopic tilt
Avoid decentration, if prescribed,
prisms should be ground in

17. Importance of accurate fitting
 Optical axis should pass through the
center of rotation
 Increased off axis errors due to tilt or de-
centration
 Errors due to improper fitting will be
larger, may be twice as compared to
spherical surfaces

18. Counseling is important
 Adaptation: especially for hi-power
 Change in magnification properties
 Amount and location of reflected images
 (for higher Rx ARC is preferred).

19. Difficulties
 Difficult to assess optical performance
 Lens gauge can not measure amount of
asphericity
 Difficult to assess parameters of previous
lens
 Back surface may touch eyelids

20. Identification
 Geneva Lens Measure

21. Identification
 Lensometer

22. Identification

23. Troubleshooting
 Listen to the patient’s complaints carefully
 Check the following parameters of
spectacles
◦ Lens power
◦ PD and Optical Centration Distance
◦ Pantoscopic tilt
◦ Base curve

24. Troubleshooting
 Check the following on patient
◦ Check Monocular PD
◦ Adjust the pantoscopic tilt, if not proper
◦ Adjust the nose pads and reduce the vertex
distance
◦ Counsel the wearer for adaptation
 Still the problem persist recheck the
refraction.

25. THANK YOU