This document discusses rigid gas permeable (RGP) contact lenses. It notes that RGP lenses are made of oxygen permeable materials and are better than soft lenses for vision, durability, correcting astigmatism, eye health, and ease of care. RGP lenses are recommended for conditions like keratoconus or high refractive errors. The fitting process involves screening patients, measuring the eye, trial fittings, and dynamic and static assessments. Proper care and maintenance of RGP lenses is also discussed.

1. Tobin C Eapen
Msc Optometry
EMLC THIRUVALLA

3. What is RGP lens??
 RGP lenses are those lenses made up of materials which are
permeable to oxygen
 Due to their oxygen permeability they have become popular
by the name semisoft lenses

4. Are RGP lenses better than soft lens??
 Good vision
 Durability
 Able to correct astigmatism completely most of the cases
 Excellent eye health
 Less tendency of deposit formation
 Ease of care & maintenance
 Cost factor

5. Choice for RGP/ Indications
 Keratoconus
 High refractive error & high astigmatism
 Trauma or irregular astigmatism
 Post graft

6. Cont…
 Slow down myopia progression
 Corneal degenerations & dystrophies
 Applied in orthokeratology

7. Patient selection

8. Patient Selection
High Motivation
 A highly motivated patient is more likely to be successful
 Motivation is the key factor for the tolerance of initial
adaptation period

9. Moderate To High Prescription
 Patient with moderate to high prescription tend to be more
motivated than those with low power
 Best corrected vision is poor with spectacle power & soft
contact lens
Corneal toricity
 The quality of vision is superior to soft CL & spectacle
 Patient with significant against rule astigmatism or oblique
corneal toricity often have less success with spherical RGP

10. RGP FITTING
PATIENT SCREENING
PRELIMINARY EXAMINATION & MEASUREMENTS
TRIAL LENS FITTING
LENS DISPENSING
AFTER CARE

11. Patient Screening
 Establish why the patient wants CLs
 Is the patient suitable for RGP
 Obtaining baseline information
 Advise patient of their options

12. Preliminary measures
Corneal radius of curvature
 Corneal topography is essential for selecting the BOZR
 Measurement is usually made with keratometry
 Average k or flat k reading is taken as trial lens BOZR

13. Corneal Diameter
 Guide to the total lens diameter
 Measuring Horizontal Visible Iris Diameter (HVID) by using
millimeter ruler
 Total lens diameter will be 2.3 to 2.5 mm less than HVID
Pupil Size
 For the selection of BOZD ( Back Optic Zone Diameter)
 BOZD is about 1mm larger than the pupil diameter in dim
illumination

14. Lid Characteristics
 Position of upper & lower lid is important in determining the
lens total dia that is required
 Lid tonus can be assessed when the lid is everted for
examination
 Graded as loose, average & tight
Spectacle Refraction
 Do spectacle refraction before fitting RGP lenses
 Relationship b/w refraction, topography & visual acuity will
indicate the type of lens which will most suit the patient

15. Trial LENS SELECTION & FITTING
Range Of Designs Required
 For low & high minus: the recommended BVP (back vertex
power) is -3.00 D for low minus & -6.00 D for high minus
 For low & high plus: +2.00 D for low & +5.00 D for high plus
 Diameter: for each BVP, it is valuable to have two diameter, a
small dia of 9.20mm & large dia of 9.60mm
 BOZR: range of base curve is required from 7.00 mm to 8.40
mm (0.05 mm step)

16. Lens Application
Patient Instructions
 Counsel the patient on the sensation they will notice when the
lens is placed on the cornea
 Advise to keep eyes closed for few seconds after the lens
placed on the cornea
Setting time
 An adequate amount of time must be given
 Excessive tearing results in an inaccurate fitting assessment

17. Fitting Assessment
RGP FITTING
Dynamic fitting assessment
decentration
stability
Movement
Static fitting assessment
Lens to cornea
relationship

18. Dynamic Fitting Assessment
Centration
 Examine the lens location on the cornea
 High riding or low riding
 Excessive decentration may cause visual problems, lens
instability
LOW RIDING HIGH RIDING CENTERED

19. Stability
 Does the lens have consistent movement & position
of rest or decentration
 Assessed after adequate degree of adaptation has
been achieved

20. Movement
Amount of movement
 Assessed by post blink recentration of the lens
 The post blink movement may be as much as 1 to 1.5 mm
Type of movement
 Smooth vertical movement
 Apical rotation
 Rocky movement
 Two part movement
 lid attachment
Speed of movement
 Rate as slow , average or fast

21. Static Fitting Assessment
 Determine the relationship b/w the lens back surface & the
anterior surface of cornea
 Assessed with the patient instructed to looking in the primary
gaze position, lens should be centered on the cornea or its
natural resting position
 With the lens centered, the fluorescein pattern is assessed &
recorded

22. Static Fitting Techniques
Central zone
 Central Pooling – steep fit
 Alignment- ideal fit
 Central touch- flat fit

23. Mid peripheral zone
 Observing the presence of fluorescein at the mid periphery
 Contact zone , alignment & fluorescein band
Mid peripheral
contact zone
Alignment zone Mid peripheral band

24. Peripheral zone
 Observing the band of fluorescein at the perphery
 Classify the width & depth of the clearance
 Excessive edge clearance- flat fit, minimum or no clearance-
steep fit
Excessive edge lift Minimum edge lift Optimal edge lift

26. POSITION STEEP OPTIMUM FLAT
Central zone
Pooling Feathery touch Bearing
Mid peripheral
zone Bearing Slight pooling pooling
Peripheral edge
lift Very narrow
Edge lift/clearence
of 0.5 to 0.75mm
Excessive Pooling,
wide edge
lift/clearence

27. Optimal Dynamic Fitting Characteristics
 Centration: centred
 Stability : stable
 Movement: smooth vertical
average speed
1 to 1.5 mm
 Lid attachment : superior lid coverage

28. Optimal static fitting characteristics
 Central zone: minimal central clearance
 Mid peripheral zone: light mid peripheral contact zone
 Peripheral zone: optimal edge width
average edge clearance

29. Rule Of Thumb
 Flatten BC by 0.25 D or 0.05mm for every increase in diameter
of 0.5 mm
 Steepen BC by 0.25 D or 0.05mm for every decrease in overall
diameter of 0.5mm

30. Over Refraction
 Determining the over refraction allows the tear lens to be
calculated
 If the lens is fitted steep, +ve tear lens will result & the power
of the CL will require less plus or more minus
 If the lens is flat, the tear lens will be –ve & power of CL will
require less minus or more plus
 Final CL power is the sum of trial lens power & over refraction

31. Toric RGP Fitting
 When the amount of corneal astigmatism results in an
unsatisfactory fit from a spherical RGP lens, it is often
necessary to fit a back surface toric lens
 The ideal lens fit should show the same fluorescein pattern as
a spherical lens on a spherical cornea

32. Care & Maintenance
Purpose of care & maintenance
 Clean lens
 Good vision
 Good comfort
 Safe lens wear
Care & maintenance components
 Cleaning solution
 Rinsing solution
 Disinfecting solution
 Protein removers (weekly)
 Rewetting/ lubricating solutions
 Lens storage case

33. Lens storage & cases
 CL stored in a clean contact lens storage case
 Scrub with a toothbrush & detergent weekly
 Rinse with hot water
 Air dry

34. Always
 Wash, rinse & dry your hands before handiling your lenses
 Replace the lens at the interval specified by your practitioner
 Have a regular check up with your practitioner as
recommended
 Seek professional advice if you are having problems with your
CL
 Better to have a pair of spectacle for when you need to
remove your lenses

35. Common Rgp Lens Complication
 CLPC ( contact lens induced papillary conjunctivitis)
 3 & 9 o’ clock staining
 Corneal staining etc..

36. THANK YOU