Contact Lenses Overview of basics and considerations for

Contact Lenses Overview of basics and considerations for fitting

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

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

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

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

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

Why/Why not soft lenses? n Advantages – – – Comfortable Available Easy to fit Good for social use Better for internal cyl n 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 <. 75 D 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 n n 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. 5 mm all around) Stability (. 5 mm in primary, . 75 mm in upward) Is pt comfortable?

Soft CL problem- sphere Patient’s Rx is -5. 00 -1. 00 x 090 all cyl is corneal n K’s 44. 50/45. 50 n Patient cannot afford toric lenses- what do you prescribe?

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

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

Fitting the astigmat with soft lenses n 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 n If lens base rotates to your Left X degrees, Add X to spectacle cyl n 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 n Consider first lens will be a trial, rarely one lens is sufficient n Failure rate is about 10% n

Toric Soft CL problem n n Patient’s Rx: -6. 50+2. 00 x 045 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 n n n Optics of contacts Soft Lenses RGP Lenses Bifocal Lenses Fitting procedures

Types of RGP’s n n n Spherical Aspheric Toric – Back surface toric – Front surface toric – Bitoric n n n SPE CPE Bifocal – Aspheric – Segmented – Aspheric and segmented n n n 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? n Advantages – – – 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 n Disadvantages – – Adaptation Chair time Misconception Learning to fit

Fitting Philosophies n Lid Attachment – – n 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 n FT contact lens wear n Corneal cyl up to 2. 50 D (if more, then the lens doesn’t fit well) n Not great for lenticular cyl n

RGP sphere fit method n n n 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 d. K means flexure, may need to increase CT. 03 mm) – Consider pupil size for OZ – Thin flex (intentional flexure) – 1 D k cyl WTR or ATR residual cyl

r e F l u o r e s c e i n P a t t e r n s : 1 2 Fluorescein Patterns A S l p i h g e n r m i e c n a t l p B a C t t o e n r n 3 �D E v W e T n R p �

Observe apical clearance and insufficient peripheral clearance On K 95/84 Bicurve design with a 9. 0 mm PCR; . 8 mm wide Insufficient edge clearance can be observed More alignmet with greater Peripheral clearance On K 95/76 Bicurve design with a 10. 0 mm PCR; . 5 mm wide Bicurve design with a 10. 0 mm PCR; 1. 0 mm wide Good edge, bit narrow An increase in edge clearance can be observed 12 mm PCR, . 8 mm wide Observe greater clearance

Lacrimal Lens n n 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) n 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. 05 mm=0. 25 D

Lacrimal Lens Problem CL parameters: 7. 50/-6. 00/95 n Need to steepen BC. 5 D what is new power? Need to flatten BC by. 75 D what is new power?

Flexure RGPs n 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 n n Rx: -8. 50 DS 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 n n Pay attention to the periphery (tear meniscus) – Too tight – Too loose Bicurve design with a 9. 0 mm PCR; . 8 mm wide 12 mm PCR, . 8 mm wide Insufficient edge clearance Observe greater clearance can be observed

Astigmatism and RGPs Back surface toric n Toricity on back, sphere on front n use with lots of k cyl (2 D 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 n Determine BC first (need accurate K’s) n. 25 D flatter than flat K n Steep K determined by making toricity ¾ of K cyl (flat BC + ¾ change in BC) n Power is toric and specified for each meridian n LL in flat meridian, leave power for steep meridian unspecified n Make toric peripheral curves to create a round OZ

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

Bitoric n n n n 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 >2 D Refractive astig w/in. 75 D of K cyl Good vision with sphere but poor fit Lens can rotate around w/o affecting vision

Bitoric n n CPE (cylinder power effect) Use for eyes with significant K (1. 5 D) and internal cyl (>. 75 D). – Back surface corrects the K cyl, the front surface corrects the internal cyl. n 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. 5 D) n Fits like spherical lens on back, but toric surface on the front. Front power is the cyl that is left over on the OR n Has to be stabilized with prism n

RGP Problem Rx: -3. 00 + 6. 00 X 090 n K: 42. 50/47. 75@180 n What bc (spe)? n What power? n

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

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

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

Therapeutic fits n 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 n Rigid lenses n

CLS and the presbyope n 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 n RX: -5. 00 +1. 00 x 180 ADD +1. 50 n -4. 25 DS ADD +1. 50 n What would you prescribe? n Same for lasik/refractive pts n

Bifocals – soft lenses D Simultaneous vision N N D D I N aspheric

Bifocal RGP n d aspheric

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

CRT Use of high d. K, 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 n n n n n Details of previous cl wear What are the problems? When/how do you wear them? Careful refraction (vertex over +/-4 D) 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 n Follow up in 2 -4 weeks n Tell pts which solutions to use n Refit if needed n

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