CONTACT LENSES FOR KERATOCONUS & ALL IRREGULAR CORNEAS

Transcription

1 CONTACT LENSES FO KEATOCONUS & ALL IEGULA CONEAS Technical Fitting Guide HYDOGEL

2 KeraSoft IC Technical Fitting Guide Introduction The KeraSoft IC is a soft contact lens designed to fit all stages of keratoconus and other irregular cornea types e.g. PMD, post graft and post refractive surgery. This Award winning design is available in a choice of 2 materials; lathe cut Silicone Hydrogel (SiH) (74% water content) and high water content Hydrogel (77% water content). Overall Diameter 14.50mm Front Optic Zone 8mm Peripheral Curves Design The KeraSoft IC has a front surface toric design, with a front optic zone diameter of 8mm. The spherical back surface has tricurve geometry with a large back optic diameter of 12.50mm for the standard 14.50mm diameter lens. A wide range of base curves and diameters are available (see below). The periphery of the lens can be manipulated independently of the base curve. Additionally, if required, the periphery can be altered in one or two sectors only, the size and angles of which can be defined by the practitioner (Sector Management Control). Fitting Set Laser Mark (Broken line on left lens) Back Optic Zone 12.50mm Inversion Mark Each lens has a vertical laser mark at the 6 o clock position; a full line indicates the lens is for the right eye and a broken line indicates the left. Additionally, there is a dot (the inversion mark) located to the right of the laser mark (when looking at the lens from the front surface) and this allows the practitioner to ensure the lens is not inside out. Stabilisation is achieved using prism ballast with balanced overall thickness. All Fitting Lenses are prism ballasted to ensure that they fit in the same way as the final powered lens. The fitting set comprises 6 x lenses with a Standard periphery (STD), 1 x lens with a Flat periphery (FLT2) and 1 x lens with a Steep periphery (STP2) and is supplied in 77% high water content hydrogel. Fitting Set Parameters BCO DIA PEIPH Power STD Plano STD Plano STD Plano STD Plano STD Plano STD Plano FLT2 Plano STP2 Plano Parameter ange Base Curve Diameter Lens Design Periphery Options Sector Management Control Power ange 7.40mm to 9.40mm (0.20 steps) 14.00mm to 15.50mm (0.50 steps) Front surface Asphere or Aspheric Toric prism ballasted with balanced overall thickness Wavefront aberration control Standard, STEEP1, STEEP2*, STEEP3*, STEEP4* (*everse Geometry), FLAT1, FLAT2, FLAT3, FLAT4 Periphery can be invidividually customised to allow Steeper and Flatter sectors, with a continuous blend between the two sectors Sphere: DS to DS Cylinder: to DC (in 0.25 steps) Axis: 1 to 180 (in 1 steps) Lathe-cut SiH (Filcon V 3) UltraVision 77% (Filcon II 2) Water Content 74% 77% Dk 60 x (cm 2 /sec)[ml0 2 /(ml x mmhg)] 53 x (cm 2 /sec)[ml0 2 /(ml x mmhg)] Handling Tint Clear Clear Wear Modality 3 month, daily wear 12 month, daily wear Pack Size Single lens, 2-pack Single lens KeraSoft IC prescription lenses can be supplied in either lathe cut Silicone Hydrogel material or high water content Hydrogel. All Fitting Lenses are supplied in the high water content hydrogel material only. Lenses can be ordered in either material without the need to change parameters or power. 1

3 How to determine the First Choice Fitting Lens Fitting of the KeraSoft IC is based on the mid peripheral and peripheral corneal shape, not the central K readings, much like normal soft lenses. In this respect, fitting KeraSoft IC differs significantly from fitting corneal GP lenses as they use fitting rules related to the central corneal curvature. Although topography serves as a valuable tool for recognising corneal types, KeraSoft IC can be fitted, without the benefit of topography, using standard, lathe cut soft lens fitting techniques. Utilising the slit lamp, valuable information can be gained by assessing the overall corneal shape which can then guide the choice of the first Fitting Lens. Thereafter, assessment of the lens performance on eye will supply sufficient information for the fit to be refined. Corneal Shape To assist corneal shape assessment, it is helpful to look at the corneal profile as this can guide the choice of the first Fitting Lens. To observe the corneal profile, ensure the patient is looking straight ahead, move the eye piece and illumination unit of the slit lamp 90 degrees from the usual straight ahead position, separate the lids and observe the cornea from the side. For conditions that cause irregular cornea, the resultant shape of the cornea is partly determined by the original shape of the cornea before ectasia developed or surgery was performed. Below are some representations of corneal shapes as represented by topographical mapping. It should be noted that a normal cornea is fairly uniform in shape whereas an irregular cornea will demonstrate extremes of steepness and flattening within relatively small areas. Keratoconic and pellucid corneas can also (rarely) demonstrate steep areas other than in the inferior position. (1) Normal Cornea (2) Steep Central/ 3) Steep central or (4) Steep inferior/very (5) Flat central/normal Steep Periphery inferior/flat periphery Flat superior periphery to steep periphery Mild to Moderate Keratoconus with relatively normal corneal shape (Type (1) above) These corneas have reasonably normal characteristics in the mid periphery and can be fitted with lenses of base curves in the range STD in the same way as normal corneas. However, mild keratoconus can be deceptive if the peripheral cornea was relatively steep before ectasia developed and may need to be fitted as Type (2). Cornea with steep central/inferior area and steep mid-periphery/periphery (Type (2) above) This type of cornea demonstrates steep central K readings and a relatively steep mid peripheral and peripheral curvature, even compared to a normal cornea. The corneal profile appears to have steep sides and this corneal shape is best fitted with base curves between 7.80 and 8.00 STD from the Fitting Set and 7.60 base curves are available on request for more advanced cones. Cornea with steep central/inferior area and relatively flat mid-periphery/periphery (Type (3) above) The mid periphery in these corneal types tends to be even flatter than normal corneas and it is advised to start with Fitting Lenses in the range STD. For nipple cones, the difference between central and mid peripheral areas is even more extreme and suggested first choice Fitting Lens is 8.20/14.50/FLT2, which has a periphery equivalent to an 8.60 STD Fitting Lens. Low Cone/Pellucid Marginal Degeneration (Type (4) above) Both these corneal types present in a similar way, with relatively normal central K readings and against the rule astigmatism. Corneas tend to be very flat superiorly and are significantly curved in the inferior area. Lenses in the STD range are a good starting point. If all lenses tend to flute inferiorly, try the 8.60/14.50/STP2 Fitting Lens. If this improves the fit but causes fluctuating vision, an SMC lens with a steep periphery in the inferior portion only may be necessary. For more information, see the section on adjusting the periphery. everse Geometry Corneal Shapes (Type (5) above) These corneal types are usually post surgical: post graft and post refractive surgery It is useful to note that although topography machines may record the central area as blue (flat) and the periphery as red (steep), in fact the periphery may be quite normal, in terms of curvature. The mapping is simply indicating the relationship between the curvatures of the two areas. It is suggested that such corneas are fitted with the 8.60/14.50/STP2 lens from the Fitting Set, as this lens most closely matches the corneal shape. However, if the cornea had a relatively flat periphery before surgery, it may be best to begin with an STD periphery lens. 2

4 KeraSoft IC Fitting Procedures The fit of a KeraSoft IC lens is assessed utilising the following 5 characteristics: Movement, otation, Centration, Comfort and. All of these characteristics have equal importance when assessing fit. Even if 4 other fitting characteristics appear to be optimal, if is sub optimal, then the fit is not correct. Always assess fit within 5 minutes of insertion It is important to assess KeraSoft IC within 5 minutes of insertion, as the movement at this time equates to the movement after 8 hours wear. It should be noted that it is possible for lenses that are fitting flat to be very mobile after 5 minutes but become immobile after 30 minutes and this can erroneously be interpreted as being a tight fit. Dynamic Assessment outine Mo o C Co Optimal Lens Fit Characteristics Movement 1mm - 2mm Note: Up to 3mm post blink is acceptable, providing the patient is comfortable otation should be minimal with the laser mark as close to the 6 o clock position as possible Lens should be central Lens should be consistently comfortable Visual Acuity should be steady with little fluctuation MooCCo gives optimal The slit lamp routine below is designed to capture information on Movement otation and Centration and can be used to assess fit using the Fitting Procedure below. It is important to assess fit first in straight ahead gaze and then in upward gaze followed by lateral gaze movements. The resultant lens behaviour can be used to determine the fit as seen below. The laser mark and the visible FOZ can be utilised to assist in fit assessment (see pictograms). Assess fit in straight ahead and upwards gaze and assess lag on lateral gaze movements Straight ahead Gaze Movement: otation: Centration: Is it limited, optimal or excessive? Is the laser mark vertical or rotated? Is the otation relatively stable or erratic? Is the FOZ central or decentred? Movement otation Centration A G 0-1mm G Upward Gaze Movement: otation: Centration: Is it limited, optimal or excessive? Does the laser mark stay in same position as straight ahead? Is the otation relatively stable or erratic? Is FOZ central, dropping to limbus or below limbus? 1-3mm G A A A Does the lens move off the cornea? >3mm Lag on right/left Gaze Does the lens lag excessively? Does it remain reasonably central? Using the above routine and characteristics of tight and flat fits below, it is possible to refine the fit with the Traffic Light fitting system on the next page. As a useful aid, the following tables list typical characteristics of a Tight Fit and a Flat Fit when fitting KeraSoft IC: Characteristics of Tight Fit Characteristics of a Flat Fit Mo Little movement on straight ahead gaze. Lenses may move more on upward gaze. Mo Movement more than 3mm on straight ahead gaze and may flute at one position. o Stable rotation of degrees or more on straight ahead and upward gaze. 30 degrees rotation or more indicates a poor fit. o Unstable, erratic rotation of degrees or more on straight ahead gaze. Laser mark will swing on upward gaze. C Lens is usually central. C Lens decentres and FOZ drops to limbus or below on upward gaze. Co Tight lenses are comfortable but often become uncomfortable after a few hours, often in a particular position. Co Flat lenses are generally edgy and uncomfortable and this does NOT settle with time. A tight fit will give clearer vision after blink. A flat fit will give worse vision after blink. This does not settle with time. 3

5 KeraSoft IC Fitting Procedure The chart below utilises a traffic light system to indicate when the fit is optimal, requires re-assessment or is incorrect and should be removed immediately. As mentioned previously, it is best if the lens fit assessment begins within 5 minutes of lens insertion. It is not advisable to insert a lens and send the patient out for it to settle without first assessing the fit on a slit lamp, as a flat lens can become immobile after approximately 30 minutes and this can be mistaken for a tight fit. Presence of significant air bubbles that do not settle is an indication of a tight fit and obvious fluting is an indication of a flat fit. In both instances, the first lens choice should be reassessed. Procedure Select and insert a lens using the First Choice Fitting Lens Guide. If in doubt, begin with 8.20/14.50/STD. Assess lens fit within 5 minutes using the Dynamic Assessment outine outlined on the previous page. If fit is in ED zone, remove lens and then select next Fitting Lens 1-2 steps steeper or flatter. If fit is in GEEN or AMBE zone, begin over refraction whilst the lens settles further. If is in ED zone, remove and reconsider first lens choice, rechecking corneal profile and topography. If is in AMBE zone, determine whether fit is steep or flat, then adjust by 1 step. When an optimal GEEN fit is achieved, allow to settle for minutes then finalise over-refraction and take note of BVD. Optimal Fit (Green) e-assess Fit (Amber) Incorrect Fit (ed) Movement 1-3mm Vertical Post Blink Up to 3mm acceptable if patient is comfortable <1 or >3mm <1mm - try one step flatter >3mm - try one step steeper Too Mobile O Immobile Lens that Moves with Push-up If lens too flat - try 2 steps steeper If lens too tight - try 2 steps flatter otation Centration Laser Mark - Vertical Degrees >20 Degrees Up to 15 degrees stable rotation acceptable if fitting 1 lens steeper or flatter does not reduce the angle Central Minimal decentration acceptable if visual acuity is good Erratic swing on blink - Flat fit Limited swing on blink - Tight fit Decentres on Straight Ahead Gaze / FOZ Drops to Limbus on Upward Gaze Try lens 1 step steeper Erratic swing on blink - Flat fit Limited swing on blink - Tight fit FOZ Edge Drops Below Limbus on Upward Gaze Try lens at least 1 step steeper Comfort Good Comfort General Discomfort Very Uncomfortable Consistently good comfort Lens feels edgy - Flat fit Discomfort in one location - Tight fit Comfort does not improve with time No Fluctuation Fluctuation with Blink Very Poor Vision Visual acuity should not fluctuate on blink Worse after blink - Flat fit Clearer straight after blink - Tight fit Poor vision not improved by any over-refraction Hints and Tips Movement A lens that is fitting too flat, may initially be mobile and then can become immobile after approximately 20 minutes due to the lens decentring and aligning with flatter areas of the cornea. However, the lens will usually move easily with Push-Up test. This is why it is important to assess the fit within 5 minutes. Lenses that are fitting tightly and show little movement on straight ahead gaze, may appear to move well on upward gaze due to lid interaction with the lens edge. Be guided, in this instance, by the movement on straight ahead gaze. otation For an irregular cornea, a significantly rotated lens indicates that the fit is not correct. It is desirable for the laser mark to be as vertical as possible. A lens that is fitting tightly will produce a stable rotation; i.e. it will remain in approximately the same position when the patient looks straight ahead and then looks upward. 4

6 A lens that is fitting flat will demonstrate rotation that is unstable: i.e. it may change position over time and on upward gaze will swing back towards the vertical in an erratic fashion. For some corneas, there will always be some rotation, whichever lens is fitted, in which case the optimal fit must be determined solely by the other characteristics. Centration The FOZ of the KeraSoft IC lens can be used to judge centration and movement. A decentred lens that appears to be fitting well in all other respects will often induce ghosting and patients may report that they have improved acuity if they turn their head. This usually indicates the lens is fitting flat and visual symptoms are caused by the decentred optics. On upwards gaze, if a lens drops so that the FOZ rests on the limbus or falls below it, this indicates a lens is fitting too flat. If the FOZ falls below the limbus, then try a lens 2 steps steeper. If all Fitting Lenses tend to show that the FOZ decentres downwards towards the limbus, this implies marked inferior curvature of the cornea, in which case an SMC design might be the appropriate option to use. Significant lag on lateral gaze movements will confirm a lens is fitting too flat. If the lens moves significantly off the cornea, then try lens 2 steps steeper. For moderate lag, try 1 step steeper. Comfort This characteristic is very valuable in assessing fit. A lens that is fitting flat will feel generally edgy in the eye. Optimal and tight fits will both feel comfortable; however, a lens that is fitting tightly will gradually start to feel uncomfortable at the flattest point of the cornea and the patient will be able to indicate this area quite easily. If patients have become accustomed to contact lenses that are uncomfortable, they may feel that a KeraSoft IC Fitting Lens is comfortable, even if it is fitting too flat. However, they can still differentiate between lenses that are fitting steeper and flatter when given the option. Visual Acuity with a plano Fitting Lens, and an over refraction in place, is an excellent indicator of fit. This is why it is suggested that over refraction is started as soon as the fit is in the AMBE or GEEN zone. Always ask the patient whether vision is better or worse after the blink. If Visual Acuity is clearer after the blink straight away, reassess the fit on slit lamp as the lens may be too tight. Use other indicators, such as rotation and movement, to assess whether to flatten lens by 1 or 2 steps. If the Visual Acuity is worse after the blink, wait to see if this starts to improve with settling. If it does not, reassess the fit on slit lamp as the lens may be fitting too flat. Use other indicators, such as rotation and centration, to assess whether to flatten lens by 1 or 2 steps. Significant ghosting of letters can indicate that the lens is decentred or that the cyl element is over, or under, corrected. If retinoscopy is difficult, due to corneal distortion, auto-refraction or topography over the lens can be helpful in indicating amount of cyl and its axis. Manipulating the periphery Up to 80% of all Irregular Cornea cases can be fitted with the standard periphery lens. Due to its tricurve design, the STD periphery of the KeraSoft IC is flexible enough to accommodate most irregular corneal surfaces. However, in the cases where this is not sufficient to obtain optimal fit, the peripheral radius of curvature can be flattened or steepened independently of the base curve by up to 4 STEPS. A change in the peripheral curve of a lens by 1 STEP is equivalent to providing the periphery of a lens with a base curve 0.20 steeper or flatter. Certain corneal shapes (see below) nearly always benefit from a change in periphery and 2 lenses with non standard peripheries are included in the Fitting Set for this purpose; 8.20/14.50/FLT2 and 8.60/14.50/STP2 8.20/14.50/FLT2 This configuration is useful in cases of keratoconus where there is a steep cone that flattens off markedly towards the periphery, such as a Type 3 cornea (see above). For such corneas, standard periphery lenses will give a reasonable fit but fluctuating Visual Acuity and often significant, stable rotation will be present. The 8.20/14.50/FLT2 Fitting Lens will generally give better Visual Acuity. For more advanced cones, it is possible to order steeper base curve Fitting Lenses with a FLT2 periphery. 5

7 8.60/14.50/STP2 The STP2 lens is a useful first choice lens for Type 5 corneas (see above) such as post refractive surgery and post graft cases where topography clearly indicates the corneal periphery is significantly steeper than the centre. This design represents a reverse geometry shape, as all normal soft lens designs flatten slightly towards the periphery. The 8.60/14.50/STP2 Fitting Lens will generally give better Visual Acuity than standard periphery lenses. For corneas with significantly flat central areas, it is possible to order flatter base curve Fitting Lenses with a STP2 periphery. For irregular corneas, changing the diameter to try and improve fit can often result in unwanted changes such as air bubbles. Changing the periphery by one step can be used to improve the fit of a near optimal lens. Note that changing the periphery from the standard configuration results in a reduction in the Back Optic Zone Indications for using a FLAT periphery Indications Actions Comments If significant air bubbles are present near the periphery but flatter lenses are too mobile, decentre or cause discomfort The cornea is a Type 3 shape (see above) and there is generally very poor Visual Acuity with any Fitting Lens Try the 8.20/14.50/FLT2 Fitting Lens If Visual Acuity is improved with this lens but the lens is too mobile or rotates erratically, then Fitting Lenses with steeper base curves with a FLT2 periphery can be ordered. When fit is near optimal but is clearer after the blink and flatter Fitting Lenses are too mobile, decentre or cause discomfort Ordering a FLT1 periphery will improve Visual Acuity without destabilising the fit. This has a similar effect to changing to a diameter lens on a normal cornea. It is unusual to require the FLT3 and FLT4 peripheries, as in most cases, improvement to the fit can be obtained by flattening the base curve by 1 STEP whilst maintaining a FLT2 periphery. If this still does not improve fit, contact customer services for advice with topography mapping if available. Indications for using a STEEP periphery Indications Actions Comments Where there is obvious fluting in one position but steeper lenses which eliminate the fluting give fluctuating Visual Acuity (clearer after the blink) When fitting a Type 4 cornea (see above) and flatter Fitting Lenses decentre but steeper Fitting Lenses produce fluctuating vision, (clearer after the blink). Try the 8.60/14.50/STP2 Fitting Lens. If this improves the fit and Visual Acuity but either the lens is still too mobile or gives fluctuating vision, clearer after the blink, then steeper or flatter base curve Fitting Lenses with STP2 periphery can be ordered. When fit is near optimal but is worse after the blink and steeper Fitting Lenses have too little movement and give fluctuating vision, (clearer after the blink). Ordering a STP1 periphery will improve Visual Acuity without destabilising the fit. This has a similar effect to changing to a diameter lens on a normal cornea. STP 3 and STP 4 peripheries may be required for post refractive surgery cases where the eye was previously significantly myopic, due to a steep corneal shape, pre surgery. If topography indicates this is the case, then contact UltraVision s Customer Services to obtain specific Fitting Lenses. If manipulating the periphery results in a lens that is still fitting too tight or too flat in one particular location, then the Sector Management Control (SMC) design may be required. 6

8 Sector Management Control In the case of significantly irregular corneas, there may be a requirement to tighten or flatten a periphery in one location only. This type of adjustment is possible using Sector Management Control (SMC) and can be useful for PMD, low cones, advanced keratoconus, post graft, post refractive surgery, surgery related ectasias and even very high astigmatism on an otherwise normal cornea. An example of an SMC design for PMD would be to designate a STD periphery to an area between 30 and 150 and a STP2 periphery to an area between 220 and 320. The intermediate areas are automatically blended. If this lens was being ordered on an 8.60 base curve, the configuration would be: 8.60/14.50/STD/STP2 A1=30 A2=150 A3=220 A4 =320 The SMC can be completely customised to suit the particular cornea; for example, it could be flattened in the nasal area only or be steepened superiorly and inferiorly in cases of high astigmatism. Note: SMC is required in very few cases. This design is only used for the most unusual corneal shapes and it is recommended to contact Customer Services for advice on the SMC periphery design before ordering. It is also useful, in such cases, that topography maps of the cornea are supplied, in colour. Please note: Faxed monochrome maps cannot be correctly interpreted. Ordering To order a KeraSoft IC lens, please use the order forms available on the CD or in paper form from UltraVision. Alternatively, contact Customer Services with the following information: Parameters equired Over efraction Material equired Base Curve Diameter Periphery Power of Fitting Lens BVD of all lenses (including all cyl lenses) Laser mark rotation and direction SiH 74% Hydrogel 77% If you wish to order powered lenses directly, ensure all rotation and BVD (Back Vertex Distance) are accounted for. Note: A laser mark rotated more than 20 degrees may indicate that the fit is not optimal and we may ask you to look again at the fit before ordering. If the periphery is not specified in the order, it will be assumed that a STD periphery is required. Examples of typical orders would be: : K IC / 8.20/14.50/-6.00/-4.50 x 35 / STD / laser mark 10 CW / 77% Hydrogel (use notation CW Clockwise; ANTI anti-clockwise) L: K IC / 8.80/15.00/ Plano/-5.00 x 110 / STP3 / laser mark vertical / SiH From this information, a lens with fitting/exchange warranty can be issued. Exchanges If an exchange lens is required, perform a fitting assessment on the current lens, using the Dynamic Assessment outine. Note the MOOCCO characteristics: Movement, otation, Centration Comfort and Visual Acuity (after blink) on straight ahead and upward gaze. Also measure any over correction as accurately as possible and supply BVD. Contact UltraVision s Customer Services with this information and the original order number. ULTAVISION INTENATIONAL LIMITED, COMMECE WAY, LEIGHTON BUZZAD, BEDFODSHIE, LU7 4W, UNITED KINGDOM ecord No. 279 Issue I N N O V A T I O N I N P A C T I C E Tel: +44 (0) Fax: +44 (0) UK Order Line: (Freephone) orders@ultravision.co.uk Web: 7