Practitioner’s Fitting Guide - ABBA Optical

1 The Rose K "System" is designed off a complex computer modelyielding the ultimate base curve geometry with appropriateperipheral curve structures. The back surface of the lens ismanufactured on computerized lathes in a series of spherical cuts. A special software program was written for the lathes to not only cutthe multiple curves but to blend them as well. Only a light polishneeds to be performed to finish the base of the lens by the lab. This means total reproducibility assurance for the fitter, lens after back surface is a series of spherical cuts that are well at the lens in a light source, it may appear to be aspheric but it is not. There are three standard peripheral systems offered in the Rose K lensdesign - standard, increased or decreased. You may require a changein the peripheral curve from standard to increased lift or decreased , if you modify a Rose K lens , you no longer have aRose K lens .

2 Further explanation is provided. The most frequentperipheral change is to increased lift where the peripheral curves areapproximately flatter than the standard lift. Flatter peripheralsystems can be generated , (standard increased lift), , , or flatter than the standard lift. Althoughnot usually necessary, they are available. These curve systems need tobe cut on the computerized lathes by the lab. Steeper peripheralsystems are available as well. The basic steep peripheral lift is approximately steeper thanthe standard lift. A steeper peripheral-system beyond this of also be generated. Again, these curves must be lathe cut by thelab. Patients exhibiting early keratoconus usually need flatter base curves, often steeper peripheral systems and larger peripheral systems other than the standard increased and standard decreased lifts are for rare cases.

3 The basic standardthree options for peripheral curve lifts should fit over 90% of yourkeratoconus patients. 9. Sagital ChangesChanging the peripheral system to steep or flat will change the sagital height of the lens and consequently the central fit. The lab willtherefore calculate a new base curve to keep the sag of the lens thesame, so that the Fitting relationship is identical to the diagnostic orthe previous prescription lens . The power will alter with the base curvechange as well to compensate for this change. Changing fromstandard peripheral lift to the standard increased lift, the lab willcompensate the base curve by steepening it and by adding - of power. Changing from a standard peripheral lift tothe standard decreased lift, the lab will compensate the base curveby flattening it and by adding + D Residual Astigmatism ( )A.

4 It is usual to leave low degrees of uncorrected. Suggested table below for the spherical - to - - to - to add is rare to see over this, when it is, toric lensesare usually needed assess if the needs to be considered put the uncorrectedcylinder in spectacles and assess whether it makes a significantdifference to the visual acuity. These patients often have some flare orglare especially for night driving. If prescribing the in spectaclesadd an A/R coating to the lenses to help eliminate this. Given thechoice between a front cylinder toric lens and a combination of aspherical contact lenses and a spectacle over correction, most patientsselect the spectacles. Each patient needs must be assessed for thebest front surface toric lens can be made if the fluoroscein patternlooks good with the spherical diagnostic lens .

5 Once base curve andperipheral system is determined, the lab can design the front surfacetoric lens . An truncation is used, so the toric lens will be larger than the diagnostic lens and then a lower truncation isadded. Normally 11/4prism ballast is used to start. Steeper bases andoblique cylinders tend to rotate more and are often more difficult When is present and the fluoroscein pattern indicates a toricbase is needed, a base toric or bitoric can be made. From the bestspherical base curve, add and subtract to get the proper baseseg: diagnostic lens , need base toric. Next select aspherical lens equal to the flattest base toric and over refract ie: a the example here. Adding this to the power of the diagnostic lenswill determine the required spherical AstigmatismA. TSP (Toric Periphery Only) - lens can also be made where the OZ isspherical but the last of the lens is toric.

6 The tight areas, usuallyat 3 & 9 o'clock, will be eliminated with a TSP Full Back Surface Toric - The Rose K lens can be made in either fullback surface toric or bitoric Front Surface Toric - The Rose K lens can be supplied as a frontsurface toric with a spherical base to correct residual Dimple VeilingOccasionally a patient will present with small bubbles trapped underthe lens . A combination of increasing the edge lift, flattening the basecurve and/or reducing the diameter should be tried first. If thebubbles persist, the lens can be fenestrated to relieve the fenestration will be at the juncture of the optic zone and thesecondary curve. Bubbling will not damage the cornea but willdecrease the visual Pooling at the Cone BaseWith excessive pooling at the cone base, reduce the diameter as thisreduces the and the cone is fitted closer and the pooling isreduced.

7 Flattening the Base Curve and or increasing the lift can alsohelp. Caution: don't go so small that vision is compromised with anoptic zone that is too Boston Logo is a registered trademark of polymer technology,a Bausch & Lomb sFitting GuidePrinted in Canada BCL220404 ACONTACT lens lens geometry, combined with the enhanced benefitsof Bostonmaterials, makes the Rose K lens the better fit for superiorpatient comfort and visual parameters make Fitting the Rose K lens easy,for reduced chair time and increased practice Rose K lens Features:Flexible peripheral systemsBase curves: - : - : anyThe Rose K Design Benefits: Fitting ease - our 26- lens diagnostic Fitting set makes it easyto find just the right fit for your patient. Better visual acuity - clinical results have consistently shownan improvement in patient vision.

8 Increased patient comfort - patients who have worn other Keratoconus RGP designschoose Rose K. It's simply more AOptimum fit immediately after blinkFig. BOptimum fit a few seconds after blink. Don t judge fit in this downward locationFig. CGood fit centrally - tight peripherallyFig. DGood fit centrally - loose peripherallyFig. EFlat centrally - good fit peripherallyFig. FSteep centrally - good fit peripherallyFig. GAstigmatic - requires back surface toric1. Diagnostic Fitting Procedures and TipsPlacing a series of diagnostic lenses on the eye can be arduous and uncomfortable for the patient. We suggest using a minimalamount of anaesthetic for maximum patient comfort and to minimizetear flow. We recommend this for all patients not just new contact lenswearers. Increased tear flow will cause the lens to sit low and giveabnormal fluorescein patterns.

9 Also instilling large amount offluoroscein can give false patterns, so be cautious about the amountplaced on the Fluoroscein EvaluationCritical to the success of a Rose K lens fit is careful fluoroscein patternevaluation. Look to achieve a light feather touch on the cone apex, asclose to alignment as possible across the cornea, with lift off over thelast to It is important that the lens is locating centrally tojudge accurately the fluoroscein pattern. If the lens lags down useupward the pressure on the lower lid to centralise the lens to judgethe fit. Some initial low riding lenses will position better after severaldays Apical StainingApical staining should not be permitted with the Rose K lens . If at anyafter care visit apical staining is obvious, refit the lens with a steeperbase Diameter The Rose K lens design is based on a complex mathematicalcomputer model that yields thousands of peripheral curvecombinations.

10 These vary by base curve, edge lift, power, anddiameter. One common request is to take a larger lens and cut it downwhen the larger diameter does not function optimally. This can not bedone because the peripheral system on an lens is drasticallydifferent from the peripheral system on an lens . The smallerlens must be for Considering Diameter amounts of astigmatism outside the cone can often befitted adequately with a spherical Rose K lens . If the lens is tighthorizontally and lifts vertically, especially at the base, reducing thediameter will minimize these and 9 o'clock staining can often be reduced by reducing thediameter by or more and/or increasing the edge low riding lenses may need to be made larger by atleast The upper edge of the lens should touch the tarsal plateof the upper lid.