Overview of basics and considerations for fitting Contact Lenses Overview of basics and considerations for fitting

Outline Solutions Soft Lenses RGP Lenses Contacts and the presbyope When to use RGP Lenses Contacts and the presbyope Other

Contact lens solutions Soft lens solutions Rigid gas permeable lens solutions Compliance always an issue

CL history is key How many years How many days/week What brand Do you use EW Do you swim How do you clean Are you having any problems?

Types of soft lenses Spherical Toric truncated Aphakic Extended wear prism ballast thin ballast Aphakic Extended wear Bifocal Bandage lenses High dK/l Colored/cosmetic Colored/prosthetic Different polymers Ionic high water Ionic low water Non-ionic high water Non-ionic low water Newer silicone

Types of soft lenses Conventional (sphere/toric) Keep for a year Bifocals Higher powers/cyl Disposable (sphere/toric/bifocals) Quarterly Monthly Weekly or Two week Daily

Why/Why not soft lenses? Advantages Comfortable Available Easy to fit Good for social use Better for internal cyl Disadvantages More risk of infection Dry out Prone to rotation (toric) Get dirty quickly Noncompliance Poor Oxygenation GPC

Fitting the spherical pt Use soft spheres if cyl is < .75D Get good MR, switch to minus cyl form Find the SE Vertex Keratometry: is K flat or steep Select material Select BC/diameter

Fitting the Soft Sphere Place lens on eye, best to wait 15 to 20 min to assess fit VA (D) and sometimes VA (N) Over refract to check your power Assess fit/movement loose (flat fit) Tight (steep fit) Centration Coverage (at least .5mm all around) Stability (.5mm in primary, .75mm in upward) Is pt comfortable?

Soft CL problem- sphere Patient’s Rx is -5.00 -1.00 x 090 all cyl is corneal K’s 44.50/45.50 Patient cannot afford toric lenses- what do you prescribe?

Fitting the astigmat with soft lenses Indications Cyl >.75D, but if too large may not be successful d/t rotation effects (blinking dynamics) K plus lenticular cyl, esp ATR NOT good for pts with irregular corneas Becherer Twist Test 20deg rot OK=90% 15 deg rot OK=90% with 2 lenses 10 deg rot OK=70% with 3 lenses 5 deg rot OK=pt must accept variable vision with soft toric

Fitting the astigmat with soft toric lenses Methods for lens stabilization Prism ballast with prism or truncation Thin zones u/l

Fitting method Best to use trial lenses! Select BC first Then axis (+/- 20) Cyl power (lower better) Sph power (least minus) Wait 15-20 min.

Fitting considerations for the astigmat Assess fit/movement loose (flat fit) - will rotate Tight (steep fit)- reduce rotation but harmful Centration- same as sphere Coverage (at least .5mm all around but sometimes bigger is more stable) Stability (.5mm in primary, .75mm in upward) Rotation in primary gaze should not exceed 15 degrees

Fitting the astigmat with soft lenses To determine final cl power Sphero cyl OR then place trial cl power and OR power in lensometer. LARS (each clock hour is 30 degrees If lens base rotates to your Left X degrees, Add X to spectacle cyl If lens base rotates to your right X degrees, subtract X from spectacle cyl

Summary Even when optimally fitted, vision will be worse than with glasses Consider first lens will be a trial, rarely one lens is sufficient Failure rate is about 10%

Toric Soft CL problem Patient’s Rx: -6.50+2.00x045 K readings: 45.00/46.00@135 -What power CL? - What bc? (choice is 8.7 or 8.2) - Say CL OR is -1.00 – 0.50 x 040 what do you do? -What if OR is -1.00 -0.75 x 090? - What if lens is rotating 20 degrees nasal?

Outline Optics of contacts Soft Lenses RGP Lenses Bifocal Lenses Fitting procedures

Types of RGP’s Spherical Aspheric Toric Bifocal Aphakic Back surface toric Front surface toric Bitoric SPE CPE Bifocal Segmented Aspheric and segmented Aphakic Reverse geometry Intralimbal Mini-scleral Scleral

Anatomy of RGP CL Bc/power/diameter/optic zone/peripheral curves/ CT/material/color

RGP why/why not? Disadvantages Advantages Adaptation Chair time More Oxygen Cheaper Less surface area Better for dry eye Masks corneal cyl Compliance Rare sleeping Rare infection Superior optics K neo recedes Less abuse Disadvantages Adaptation Chair time Misconception Learning to fit

Fitting Philosophies Lid Attachment Interpalpebral Fit is under the lid Moves with blink More comfortable Less GPC Interpalpebral Wide eyes Must have good recovery Torics

RGP spherical fits High myopia FT contact lens wear Corneal cyl up to 2.50D (if more, then the lens doesn’t fit well) Not great for lenticular cyl

RGP sphere fit method Refraction- minus power form, SE, vertex dist corrected as for soft lenses Keratometry VERY IMPORTANT!!!!!!!!!!!!!!! Select design- try on if possible Std v aspheric Material (high dK means flexure, may need to increase CT .03mm) Consider pupil size for OZ Thin flex (intentional flexure) 1D k cyl WTR or ATR residual cyl

Fluorescein Patterns too flat wtr alignment too steep                                                                                                                                                            Alignment pattern Even pattern centrally with slightly greater clearance peripherally Spherical BC on 3D WTR astigmatic cornea Horizontal bearing and excessive vertical pooling is observed                                                                                                                                                            Alignment pattern Even pattern centrally with slightly greater clearance peripherally Spherical BC on 3D WTR astigmatic cornea Horizontal bearing and excessive vertical pooling is observed                                                                                                                                                            Alignment pattern Even pattern centrally with slightly greater clearance peripherally Spherical BC on 3D WTR astigmatic cornea Horizontal bearing and excessive vertical pooling is observed       Next  >> More Fluorescein Patterns:     1     2     3 Making Lens Design Changes Fitting Pearls       Next  >> More Fluorescein Patterns:     1     2     3 Making Lens Design Changes Fitting Pearls                                                                                                                                                            2D flatter than "K" Excessive apical bearing, excessive inferior edge standoff 2D steeper than "K" Excessive peripheral sealoff 1D flatter than "K" Excessive apical bearing, excessive inferior edge standoff 1D steeper than "K" Mild peripheral sealoff Alignment pattern Even pattern centrally with slightly greater clearance peripherally Spherical BC on 3D WTR astigmatic cornea Horizontal bearing and excessive vertical pooling is observed                                                                                                                                                            2D flatter than "K" Excessive apical bearing, excessive inferior edge standoff 2D steeper than "K" Excessive peripheral sealoff 1D flatter than "K" Excessive apical bearing, excessive inferior edge standoff 1D steeper than "K" Mild peripheral sealoff Alignment pattern Even pattern centrally with slightly greater clearance peripherally Spherical BC on 3D WTR astigmatic cornea Horizontal bearing and excessive vertical pooling is observed Fluorescein Patterns too flat wtr too steep alignment

     Observe apical clearance and insufficient peripheral clearance On K 95/84 More alignmet with greater Peripheral clearance On K 95/76 Good edge, bit narrow Bicurve design with a 10.0mm PCR; .5mm wide An increase in edge clearance can be observed Bicurve design with a 10.0mm PCR; 1.0mm wide Insufficient edge clearance can be observed Bicurve design with a 9.0mm PCR; .8mm wide Observe greater clearance 12mm PCR, .8mm wide

Lacrimal Lens A rgp interacts with the tears This is why keratometry becomes important As long as rgp maintains it’s bc, the interface between the lens and the tears is spherical (elimiates astigmatism) Rgp does not affect internal astigmatism!!

Lacrimal Lens Steeper contact creates a + power LL Flatter contact creates a – power LL For every BC change, and equal and opposite change of power is needed .05mm=0.25D

Lacrimal Lens Problem CL parameters: 7.50/-6.00/95 Need to steepen BC .5D what is new power? Need to flatten BC by .75D what is new power?

Flexure RGPs Flex to the steepest meridian Wtr cornea, lens steepens in the vertical and slightly flattens in the horizontal. Measured as toricity with over-K’s Calculated effect is to lessen the minus power of the LL in the steepest meridian

RGP Problem Rx: -8.50DS K: 44.50/46.00@78 What power? What BC?

How to manipulate fit To center the lens steepen bc decrease diameter To make lens LA fit flatter bc increased diameter Pay attention to the periphery (tear meniscus) Too tight Too loose Insufficient edge clearance can be observed Bicurve design with a 9.0mm PCR; .8mm wide Observe greater clearance 12mm PCR, .8mm wide

Astigmatism and RGPs Back surface toric Toricity on back, sphere on front use with lots of k cyl (2D or more) will provide a better fit to produce alignment LL is altered, filled with plastic Higher (n) so greater refractive effect

Back surface toric Determine BC first (need accurate K’s) .25D flatter than flat K Steep K determined by making toricity ¾ of K cyl (flat BC + ¾ change in BC) Power is toric and specified for each meridian LL in flat meridian, leave power for steep meridian unspecified Make toric peripheral curves to create a round OZ

Back surface toric Assess fit- should look aligned Dot flat meridian to assess rotation- should align with flat meridian and not rotate. Perform spherocyl OR

Bitoric SPE (spherical power effect) bitoric has both front and back toric surfaces. Fits like a toric, but has the optics of a sphere when combined with the LL Indications: K cyl >2D Refractive astig w/in .75D of K cyl Good vision with sphere but poor fit Lens can rotate around w/o affecting vision

Bitoric CPE (cylinder power effect) Use for eyes with significant K (1.5D) and internal cyl (>.75D). Back surface corrects the K cyl, the front surface corrects the internal cyl. The toricity of BC and power are different, so must be stabilized Lens can’t rotate Prism.

Front surface toric Signficant internal astigmatism with a relatively spherical cornea (less than 1.5D) Fits like spherical lens on back, but toric surface on the front. Front power is the cyl that is left over on the OR Has to be stabilized with prism

RGP Problem Rx: -3.00 + 6.00 X 090 K: 42.50/47.75@180 What bc (spe)? What power?

Therapeutic fits Irregular corneas KC Pellucid K lacs Refractive induced keratoectasia Post grafts

Therapeutic RGP fits Use topography and SLE to assess K Where are scars What is steep/flat etc. Goal is to fill in irregular part with tears Pick steepest K as starting point Just fit the lens and then OR to get power

Therapeutic fits Irregular corneas may require larger diameter lenses with multiple peripheral curves Intralimbal Miniscleral Scleral

Therapeutic fits Pt expectations critical Vision improves BUT Lenses take time to get used to Careful f/u is necessary Lenses are usually NOT covered by insurance

Aphakia Soft lenses Rigid lenses

CLS and the presbyope Monovision is the easiest/cheapest Best for those under 40 Without stereo vision needs Not too picky OK with part time glasses

Monovision fit 48 yo female, OD dominant RX: -5.00 +1.00 x 180 ADD +1.50 -4.25 DS ADD +1.50 What would you prescribe? Same for lasik/refractive pts

Bifocals – soft lenses modified monovision D Simultaneous vision D N N aspheric

Bifocal RGP n aspheric aspheric d

Bifocal RGP fitting Many different brands Proprietary Fitting is specific to brand/ type Many potential changes Set realistic expectations Acknowlegde time investment $350 fit/$300 lenses- self pay

CRT Use of high dK,RGP cl at nighttime Reverse geometry design Advances in topography Nothing is worn during the day Moulds the cornea much like braces retainer

crt rgp

CRT

THE BASICS Details of previous cl wear What are the problems? When/how do you wear them? Careful refraction (vertex over +/-4D) Keratometry or topography Examination of the cornea, lids, lashes Dryness…..? MUST FIX. Pupil size (dim/light) Palpebral Apeture/ characteristics –tight/loose etc. Iris Diamter

CL fitting Fit the lens Follow up in 2-4 weeks Tell pts which solutions to use Refit if needed

The Basics Technicians are key to profitability Insertion/removal training Lens hygiene teaching Patient follow up- phone calls FOLLOW UP IS IMPERATIVE…