https://www.youtube.com/watch?v=1VtaUgmldLI

1. Ananta poudel
B-optom. 3rd year / NAMS

2. Introduction
• Presbyopia is not error of refraction but a condition of physiological
insufficiency of accommodation due to reduce amp. Of
accommodation leading to progressive fall in near vision.
• Feinbloom is credited with patenting the first bifocal contact lens in
1938.
• Williamson 1951 bifocal CL with small central convex near portion on
the front surface.

3. Intro cont..
 The correction of presbyopia is more about selecting a lens
type/correction mode that will provide acceptable vision at both
distance and near and intermediate as well.
 Why presbyopic contact lenses?
**Bifocal spectacles/reading glasses:
--Head tilting to see near .
--Restricted field of view.
--Outward symbol of aging .
--Switching glasses for reading.
--Distorted optics of progressive bifocals .
--Weight of spectacles .
--Magnification.
--Image jump.

4. Contact Lens Options in presbyopia
• Bifocal
• Diffractive lenses
• Monovision
• Multifocal
• Simultaneous vision

5. Presbyopia fitting strategies
 Disposable lenses.
 Extended trial with more realistic & better feedback.
 Use trial lens close to power required.
 Follow manufacturer fitting suggestions.(manufacturer’s literature
includes suggestions)
 Using tinted lenses to assist handling.

6. Cont..
• The visual performance at distance, intermediate, and near should be
reconciled with the needs of the patient.

7. Considerations in Presbyopic Contact Lens
Correction
Visual requirements
Occupational environment
Binocularity & stereopsis
Near add(s) required
Motivation
Medication(s)
Status of tears/tear film
Lid tensions/positions
Sensitivity of cornea & lids
Contact lens materials
Availability of tints
Costs involved

8. Presbyopia CL options
Bifocal
Diffractive
lenses
Monovision
Multifocal
Simultaneous
vision

9. Bifocal contact lens
• Lens having two portion of different focal power.
• Bifocal CL are available in both rigid gas permeable and hydrogel
designs.
 Indication for Bifocal CLs
• Favorable:
--Eyelids in normal position.
--Average or smaller than average pupil size .
--Motivated Patient.

10. Unfavourable for bifocal
 Abnormal eyelid position (Very high/low)
 High lid laxity
 Large pupil
 Binocular imbalance
 High degree of corneal astigmatism
 Narrow palpebral fissure

11. Principle of fitting bifocal CL.
Bifocal CL
Simultaneous
/segmented
Alternating /
Translating

12. Simultaneous CL
 Simultaneous vision bifocals are contact lenses in which light from
both far, near, and all intermediate distances enter the eye
simultaneously.
 Simultaneous designs essentially provide distance and near vision
together and do not rely on lens movement.
 The brain will select or concentrate on one or other will be
ignored.( eg-like looking through the net across the window at a distance object.)
 D/N correction zones are both positioned in front of the pupil in
every direction of gaze

13. Simultaneous
CL
Concentric Aspheric Diffractive

14. Concentric
 Concentric segment lenses show a sharp demarcation between
distance and near powers.
 Two types Ie: Centre near (C-N) or centre distance (C-D)
 Zone location
 Front or back surface (mostly front)
 Any zone size within 3-4 mm.
 Dependency of these designs upon the pupil size.

15. Aspheric Simultaneous Vision
Bifocals
 Progressive addition type of lens formed with alteration in anterior
and posterior curvature of the lens.
 Use of either a front or back surface aspheric design
 Back surface aspheric - centre distance (C-D).
 Front surface aspheric - centre near (C-N)
• Power uniformly increases/ decreases.

16. Aspheric cont..
• not a true bifocal design (more like Progressive add lens), they
provide an increased depth of focus at the retina and
increased depth of field that increases the near range for the
wearer.
• option for a modified monovision fitting approach.

17. Diffractive CL
 Diffractive bifocal is made up of concentric rings, like a Fresnel prism.
 Consist of several zones of progressively increasing size arranged
concentrically.
 performs well in moderate presbyopia.
 Offers higher resolution and sharper images.
 Pupil size has little effect on performance.
 good optical quality.
 Simultaneous vision.
 Easy to fit.
Bifocal contact lens with diffraction design

18. Advantages of Simultaneous Vision Bifocals
 Available in RGP and SCL designs
 D & N corrections present within pupil simultaneously
 With larger pupils, better than alternating designs
 Not gaze dependent but light dependant
 More comfortable than segmented designs.
 Fitting characteristics are equal to single vision lenses
 Easier to fit

19. Disadvantages of Diffractive Bifocal Design
 Simultaneous vision.
 Poor VA in low illumination; i.e more light is required.
 Night driving more difficult.

20. Disadvantages of Simultaneous Vision Bifocals
 Decrease VA & contrast sensitivity especially in low luminance.
 Pupil size dependent.
 Accurate over-refraction is difficult
 Compromised intermediate vision.
 Ghosting (doubling) is sometimes a problem.
 Chromatic aberration.
 Not available in toric form.
 Difficult in Adaptation & may take time (weeks, months)
 Difficult to make (great precision required)
 Made in low Dk materials only.
 Must centre well.
 Relatively small ‘optic’ zone size (5 mm).

21. Alternating / Translating bifocal CL
• These are bifocal RGP or soft lenses that incorporate a reading or
near segment located eccentrically.
 The patient must look and alternate through two separate portions
to see either near or distant objects.
 Lens moves (translates) on the eye so that vision alternates between
D & N.

22. Cont. Alt/trans.bifocal
• when patient looks down gaze the lower lid lifts the near segment
up, towards the pupil where, patient can see clear for near.

23. parameters to consider when fitting. Alt/trans.bifocal
 Power of the near addition.
 Size and shape of the near segment.
 Height of the segment above the lower edge of the lens.
 Amount of prism ballast.
 Thickness of the lower lens edge.
 TD in the vertical meridian.
 Stability of the lens fit.

24. Advantages of Alternating/Translating Bifocal
 Those requiring higher add powers.
 Those who require good stereopsis at both D / N
 Those whose tolerance of blur is poor.
 Simultaneous vision lens failures.

25. Disadvantages of Alternating/Translating
Bifocal
 Head position/attitude/movement may need alteration.
 Lens must translate without significant rotation.
 Translation must be sufficient to relocate near zone over all or most of
the pupil
 Image jump.
 Translation and re-centration (recovery) must be rapid
 Non-ideal translation may ↓ VA (D &/or N)

26. Alternating/Translating Bifocals: Requirements
 Inferior centration on downgaze.
 Correct orientation.
 Rapid post-blink recovery (RGPs only).
 Acceptable anterior eye fitting relationship.
 Translation from D to N on down-gaze.
 Pupil coverage in either lens position.
Bifocal lens movement: (a) primary gaze; (b) downgaze (D, distance portion; N, near portion)

27. Contraindications of Alternating/Translating
Bifocal
 Large pupil size.
 Lower lid below the limbus.
 Lower lid too far above the limbus.
 Loose lids (reduced lid tonus).
 Poor blinker.
 High-riding lenses
 Ptosis
 Near-vision tasks at eye level (primary gaze)
 Intolerant of RGP lenses
 Poor motivation
 Low add needed

28. Fitting Alternating Vision RGP Bifocal Lenses
 Fit ‘on flattest K’ to ‘slightly flatter than K’ (<0.50D)
– align closely
 Large BOZD
 Select TD carefully– controls segment position
 Too steep– lens may swing nasally and not translate
 Too flat– lens may swing temporally and decanter
 Rule of thumb There must be sufficient movement to ensure that
approximately three-quarter of the pupil area is covered by the
correct section of the lens for both distance and near

29. Considerations
 vertical lens diameter
- small enough to enable lens translation.
 BOZR
- centration.
- movement.
- segment rotation.
 BVP
- use a trial lens BVP close to ocular refraction.

30. Achieving Rotational Stability
 To reduce the rotation lens during a blink,
 prism ballasting
 truncation
 ↑ prism needed as ADD ↑
 ↓ prism with high + Rxs
 ↑ prism with high – Rxs

31. Adjusting Segment Height Position
• • Too high
 ↑ prism (↑ lens weight inferiorly).
 Truncate superiorly to ↓ influence of upper lid.
 ↑ inferior truncation (to lower lens).
 Flatten BOZR (lens may sit lower).
 ↓ total diameter (to lower lens).
 ↓ BOZD (lens may sit lower).
 Thin upper edge (less lid attachment).

32. Too low
 decrease truncation or no truncation.
 steepen BOZR.
 ↑ total diameter.
 ↑ BOZD.
 new segment height (higher).

33. Pupil Size and Lens Selection
 Small pupil.
-simultaneous vision bifocal.
 Large pupil.
-choose translating lenses.

34. Introduction to Monovision
• Monovision is the technique in which one eye is corrected for
distance vision and the other eye for near vision.
• works on the principle that the visual system can suppress the
central focus image thus enable the object of interest to be seen
clearly.
• some disruption of binocularity in this fitting methodology.
One eye corrected for near,
other corrected for distance

35. Disapproval of Monovision
Not approved in patients who have;
• Conceptually ‘one-eyed’ (eg,amblyopia)
• Suppression is induced intentionally.
• Contrast sensitivity is ↓.
• Stereopsis is ↓.
• Vision quality is ↓.
• confusion and imbalance.
• No adaptations occurs.
• need good binocularity; good streopsis.

36. Difficulties in monovision
 Presence of strong ocular dominance
 Tasks requiring smooth gaze shift
 Blurred, small, bright stimuli against dark
 background difficult to ignore (eg; looking out of window net)
 Night driving (daylight driving is OK)
 Intermediate vision reduced if add is > 2 D
 Pupil size is a factor (larger is worse)

37. Case
Suppose the patient’s prescription is:
RE : –4.0 Dsph
LE : –4.0 Dsph
Near add +1.50 Dsph both eyes.
 fit the dominant eye with –4.0 Dsph (the distance power) and the
non-dominant eye with –2.50 Dsph (the near power).
 Do not attempt uniocular visual*

38. Monovision: Advantages
 Simple fitting process (Single Vision lenses)
 Well suited to many presbyopes; success rate averages 73%
 Less costly (similar to SV lenses).
 Usually less chair time (uncomplicated lenses).
 Can optimize for distance or near (any distance?).
 Fitting is simple.
 Usually, quick to accept or reject.
 Ideal for social/occasional users.
 fewer trial lenses required.

39. Monovision: Disadvantages
 Reduction in distance acuity. Most individuals see better when using
both eyes than when using just one eye.
 Decreased stereo acuity
 Decreased contrast sensitivity
 Loss of clear intermediate vision.
 Speed of visual tasks may be reduced
 Unsuitable for amblyopic (anisometropia induced by monovision)
 Unsuitable for use with some existing binocular vision anomalies
 Night vision/night driving problems
 Long-term use may induce a sustained change in refractive error

40. Monovision: Contraindications
 Binocular vision problems.
 Patients with amblyopia.
 Visual task requirements
–who need fine detail eg, jeweler, watch maker, lab technician
etc.
– who need good stereopsis
 Low lighting conditions.

41. Monovision: Fitting the Distance Eye
(guidelines)
 Identify ‘dominant’ eye.
 Rx for maximum distance vision:
– correct astigmatism ≥ 0.75 D
 Use disposables lenses; they allow a low-cost trial.
 Reverse the roles of each eye if necessary.
 Discontinue if acceptance is poor.
 Least plus that provides clear N.
 Maximize range of clear vision:
–new presbyopes may have difficulty suppressing if power
difference between eyes is small.
–old presbyopes may have difficulty if add is too high.

42. Important Factors for Monovision Fitting and
Prescribing
1. Binocular vision testing should be performed to determine the effect
of monovision on stereopsis.
2. The proper eye for near vision should be selected.
3. The indicated add power should be demonstrated to the patient.
4.. Do not compare eyes.
5. Educate visual improvement over time.
5. No night driving
6. Although most individuals adapt within 2 wk, patients should be
instructed that it could take up to 6 wk to fully adapt to monovision.

43. Modified Monovision
• This is a technique where one eye is fitted with distance correction
and the other eye is a bifocal lens.
• This improves the binocularity and stereoacuity which may be
reduced in Monovision.
• This technique is also tried in patients who are sensitive to distance
vision.

45. Fitting tips &SUMMARY
 R I S O N S
Refract
Initial trial lenses based on refraction and fitting guides.
Setting time of at lease 15-20 minutes.
Overrefraction (if required)
Near assesment.
Send away with a trial.
 Assess binocular vision (same, better, worse than with spectacles)
 Follow fitting recommendations (like in SCL / rigid type).
 Extended trial wear period.

46. Cont..
 Establish optimal balance between distance and near.
 Allow the patient to adapt (longer for RGP lenses) before assessing
the visual performance.
 Careful patient screening
-successful single vision lens wearers.
- try bifocal lenses first.
 Use monovision as second option.
 poor suppression or spatial localization monovision wear likely to be
problematic.

47. Cont..
 Ensure the patient’s expectations are realistic before embarking on a
trial fitting.
 CL fitting for presbyopia is: both satisfying & challenging.
 Bifocal success rates improving progressively ; monovision will
always be the same.
 Success depends on:
– understanding patients’ needs.
– using a wide range of fitting options/trial sets.
– listening to patient feedback.
– practitioner enthusiasm.

48. Refrences
• IACLE module 8
• Contact lens primer.
• Clinical manual of CL 4th edition
• CL practice (nathan efron )
• CL in ophthalmic practice
• The CL manule ; fitting guide
• Internet sources