CET Contact Lens Monthly

or many practitioners orthokeratology still remains a mystery and is considered to be a Beginner’s guide specialist contact lens procedure. The aim of this Farticle is to provide practitioners with an understanding of the process and to orthokeratology ultimately the ability to implement orthokeratology into everyday practice. Shelly Bansal offers some valuable information for those thinking of We will cover the following areas: branching into corneal reshaping with contact lenses. Module C19930, ● A background and the theory behind orthokeratology one CL point for CLOs, one general point for optometrists and CLOs ● Preparing yourself and your practice ● Patient selection ● Lens selection ● Follow-up and problem-solving. It has to be stressed that this is purely an introduction. Any practitioner wishing to start fitting orthokeratology would be well advised to attend manufacturers’ workshops, read up on the topic, experiment with topographers and speak to fellow practitioners for more detailed advice. Next year Optician Figure 1 The will be publishing some follow-up reverse curve articles for those wanting to develop in situ and in their orthokeratology skills further. cross-section

What is orthokeratology? Since the advent of rigid contact lenses, corneal reshaping has always been an unwanted and uncontrollable by-product of wearing rigid lenses and was commonly referred to as ‘spectacle blur’. At the 1962 International Society of Contact Lens Specialists conference in Chicago, George Jessen described how he fitted lenses flatter than the flattest keratometry reading (Kf) to Figure 2 achieve a temporary reduction in Reverse myopia on lens removal. At the same geometry RGP conference Newton Wesley named the lens applied to process as ‘orthokeratology’. In 1976, a cornea, Kerns defined orthokeratology as ‘the leading to reduction, modification or elimination epithelial of refractive error by the programmed redistribution application of contact lenses’. At this juncture orthokeratology had correction-free vision. Consequently, throughout all waking hours. The basic a limited appeal because the procedure the only patients who benefited were principles are the same, in that a flatter was unpredictable and was only those who needed to achieve specific than Kf base curve is used to flatten the suitable for low myopes – generally standards of vision for their work or corneal shape and correct the myopia. less than 2D of refractive error. The sports. A current spectacle prescription and flat fitting nature of the lenses also The advent of computer numerical accurate measurements for corneal meant that they would easily decentre, controlled (CNC) high precision lathes, shape and diameter, which have been leading to a displaced treatment zone reverse geometry contact lens designs, taken with a corneal topographer, and ultimately visual distortion. corneal topographers and super high are used to determine the necessary Patients would also have to undergo Dk rigid gas-permeable lenses has base curve. A simplistic view of this several lens fittings with the lenses totally revolutionised and revitalised is that if you know the exact shape being made progressively flatter with this area of contact lens practice. of the cornea and the exact spectacle each refit. Successful patients would Today, with accelerated correction required, you can calculate then wear lenses during the day and orthokeratology, high Dk reverse exactly how much flatter the cornea remove them to get clear vision for a geometry RGP lenses are worn needs to be to give perfect unaided few hours in the evening. All in all overnight and then removed on vision. This, after all, is exactly what patients would have to pay for several awakening, giving the patient happens with corrective surgery. The lens fittings to achieve a few hours of uninterrupted and clear vision reverse curve of the contact lens links

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the mid-peripheral curve to the base Table 1 curve of the lens and also provides Some of the more widely used lens suppliers an area of redistribution for the cells from the central corneal epithelium. Lab No 7 Scotlens DLT Menicon Northern Lenses i-Go Optical The reverse curve also allows the Product name EyeDream Nocturnal MeniconZ Z Wave i-Go mid-peripheral curve to be aligned to Night the corneal surface. The mid-peripheral curve is similar to that of a traditional Workshops Yes Yes No No No RGP lens and enables better centration Accreditation Yes Yes Yes No Yes and therefore gives a better end result. Finally, the edge curve – as with Fitting Yes – all Yes – all Yes – all Some Some standard RGP lenses – assists tear software topographers topographers exchange and ease of removal. Figure Online Yes Yes No Yes Email 1 shows this both in diagrammatic ordering form and also in situ. Figure 2 shows a reverse geometry Online Yes Yes No Email Email RGP lens being applied to a myopic support cornea. The lens is then worn Tele-support Yes Yes Yes Yes Yes overnight. The shear forces applied by the lens on the tear film make the cells Marketing Yes Yes Yes Yes Extensive of the cornea move from the centre to – extensive the mid-periphery. On lens removal the central corneal epithelium is now flatter – giving full refractive correction – and benefit from a full washout period elongating and therefore stabilises the mid-periphery is steeper – making from their current lenses (4-6 weeks) myopia. it more myopic. to ensure good baseline refraction and Having selected the right patient and topography readings. It goes without taken all the correct measurements you Practice essentials saying that patients with systemic are now ready to order lenses for your Successful orthokeratology contact lens diseases affecting the eyes, ocular patient. Table 1 lists some of the more fitting relies on the same fundamentals pathology, and irregular sleep patterns widely used lens suppliers and some of as all other forms of contact lens or post-refractive surgery patients are their key benefits. Most suppliers will practice, namely an accurate and not good candidates. need spectacle Rx, K readings, HVID up-to-date refraction and full history Orthokeratology is ideal for patients and pupil diameter (normal light) and symptoms. Corneal topography is with low grade dry eyes, as no lenses measurements as a minimum, in order essential as it is used to order the initial will be used during waking hours. For to supply you with lenses. lenses and it is only through comparing the same reasons orthokeratology is also On receipt of the lenses it is important topography maps that practitioners a perfect recommendation for patients to ensure that they have been correctly can understand if the procedure is who are actively involved in sports or calculated. Checking the lenses in situ working or what modifications may those who might be contemplating will verify that they are suitable. The be required. corrective surgery. The big advantage lenses should be well centred in all Again, patient selection is an essential of orthokeratology is that it is a totally directions of gaze. There should be no factor in maximising success in practice. reversible procedure and leaves the more than 1mm to 1.5mm movement. The procedure is ideally suited for low door open for patients when new Fluorescein patterns should show a to moderate myopes ranging from advances are made available. It has also central area of touch, about 4mm in -1.00DS to -4.50DS with no more been shown that orthokeratology lenses diameter, which is evenly surrounded than -1.25DC of with-the-rule corneal may slow down the development of by an annulus of tear reservoir astigmatism. Patients with more than myopia. A consequence of flattening corresponding to the reverse curve. -0.75DC of against-the-rule corneal the central cornea is that the peripheral The peripheral curve should be 1.5mm astigmatism are not suitable candidates. cornea becomes steeper and therefore wide and with corneal alignment. Caution should also be applied to more myopia giving peripheral defocus Finally, there should be an even edge patients with lenticular astigmatism, for distance vision. It is thought that band all around the lens (Figure 3). The as the re-shaping process has no this defocused peripheral image shell patient’s best-corrected visual acuity effect on this. With higher degrees of falls short of the peripheral retina and should be achieved with lenses in situ astigmatism the lens is more likely to this stops the peripheral retina from and there may be a residual positive be displaced and therefore produce a over-refraction. Assuming that this is all decentred treatment zone, resulting in order, the patient should be coached in a reduction in visual performance. in lens application and removal. Astigmatic and high myopia designs are Traditional RGP care systems can be currently available, but it is the author’s used for lens maintenance, although recommendation that any practitioner peroxide systems with neutralising who is new to orthokeratology should tablets are also highly efficient. gain confidence by fitting the relatively easier patients first. Ideal candidates Follow-up can be of any age and with and without The first follow-up appointment should previous contact lens wear. Again be immediately after the first night of caution has to be applied with existing lens wear and as early as possible in the RGP lens wearers, as they would Figure 3 There should be an even edge band around the lens morning. The patient should present opticianonline.net 07.09.12 Optician | 17 CET Contact Lens Monthly

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Case Study (RE Only) An 11-year-old patient is new to contact lenses (03-03-2012). His mother is very myopic and is concerned her son is following in her footsteps LR has healthy eyes and there is no contraindication to orthokeratology RX RE - 4.00/ -0.25 x 70 6/6. Figures 4-9 show the corneal reshaping as the orthokeratology proceeds: Figure 4 (03-03-2012) Baseline topography Figure 5 Topography after one night of wear. Central flattening achieved with mid-peripheral steepening Figure 6 (24-03-2012) Difference map after first night of lens wear shows that central flattening achieved. V 6/9 -0.75 6.6+ Figure 7 (31-03-12) Difference maps show that the treatment zone has become more central and larger. V 6/4.8 +0.75 6/4.8 Figure 8 (21-04-12) Difference topography map shows consistency with last reading. V 6/6++ +0.25 6/6++ Figure 9 (07-07-12) Difference map still shows consistency. V 6/6++ +0.50 6/6++ In this case study, no changes were made to the lens parameters, and 4.5D of corneal flattening was achieved wearing the contact lenses. Again the steep reverse curve zone of the lens. at least a 70 per cent reduction in their lens fitting should be verified and an Topography maps should then be taken refractive error after the first night of over-refraction conducted with the and the difference from baseline noted. lens wear. Assuming that everything lenses in situ. Special attention should Irregular and decentred treatment is satisfactory, the patient should be be paid to any signs of excessive lens zones are not uncommon at this stage of seen again within a week, and should binding. A full slit-lamp examination the treatment and practitioners should present having taken the lenses out. should be conducted after lens avoid making changes to the lenses – For higher prescriptions the patient removal. It is quite common to see unless there is an obvious reason to do could be issued with a variety of daily signs of dimple veil in and around the so. In most cases the patient can expect disposable lenses to improve vision in

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the short term. Again, a full slit-lamp examination and corneal topography Multiple-choice questions – take part at opticianonline.net should be conducted. The treatment zone should now be more uniform Which of the following best defines What is the recommended upper limit in appearance and should also be well 1orthokeratology? 4for with-the-rule astigmatism when centred. Full correction of the refractive A The use of planned replacement lenses to considering a patient for orthokeratology? error should now have been achieved slow the progression of ametropia A No astigmatism and there may be a residual hyperopic B The reduction, modification or elimination B -0.75DC over-refraction. This occurs because of refractive error by the programmed C -1.25DC most lenses for orthokeratology are application of contact lenses D -1.75DC designed to over-correct by 0.50D to C The flattening of the cornea by use of a flat 0.75D to compensate for any regression contact lens Which of the following is the maximum of the effect, which might happen D The use of ‘overminused’ lenses to reduce 5movement of the lens to ensure a regular throughout the day. The patient should myopic progression defined treatment zone? then be seen a few weeks later and the A No movement is acceptable same routine followed. You should From the centre to the periphery, which B 0.5 mm now have consistent results showing 2of the following is the sequence of C 1-1.5 mm good correction and well-centred curves for an orthokeratology lens? D 2-3mm treatment zones. The patient can now A Reverse curve, base curve, mid-peripheral be placed on a six-monthly planned curve, edge curve What is the ideal diameter of the area of lens replacement programme and the B Base curve, mid-peripheral curve, reverse 6central touch? next follow-up appointment should curve, edge curve A 1mm be three months later. At this visit the C Base curve, reverse curve, mid-peripheral B 2mm same protocol should be followed and curve, edge curve C 3mm the patient seen three months later D Base curve, mid-peripheral curve, edge curve, D 4mm if all is satisfactory. The patient can reverse curve then be seen at six-monthly intervals when new lenses can be supplied. It is What is the recommended upper limit for Successful participation in this module counts as one important to check the patient’s vision 3myopia when considering a patient for credit towards the GOC CET scheme administered with the lenses in situ at least once a orthokeratology? by Vantage and one towards the Association of year, as this will highlight any changes A -1.00DS Optometrists Ireland’s scheme. in refraction. The case study on page B -2.00DS The deadline for responses is October 4 2012 18 shows the changes in correction and C -3.00DS topography maps for a patient over a D -4.50DS three-month period.

Fees motivated, forgiving, committed to the Exactly the same happens to the cornea Most practitioners who fit follow-up schedule and be prepared with orthokeratology. orthokeratology contact lenses offer to pay for the treatment. On the Studies continue to be conducted either an annual or six-monthly occasions that the first pair of lenses on the safety of overnight RGP replacement programme, which is paid doesn’t work, the main complaint is of lens wear, but anecdotal results by monthly direct debit and covers the poor vision at night, flare and haloes. from the Netherlands indicate that cost of the contact lenses, solutions These symptoms generally indicate orthokeratology is as safe as daily wear and on-going aftercare. The norm is that the treatment zone is not centred hydrogel lenses. The fact that the lenses to charge patients an initial assessment well. Adjustments to the lens diameter are removed and cleaned every morning fee of between £200 to £400 to cover and peripheral curves can generally must be a contributing factor. the trial of lenses over the first month resolve this. Most lens manufacturers A topographer is essential for and then to pay a monthly fee of and suppliers are only too happy to orthokeratology and in my view essential between £30 to £50 depending on how assist in improving the performance of for all contact lens practice. Practitioners frequently the lenses are replaced, and the lenses. The general rule of thumb need to have a good understanding of whether solutions are included. is that if you have had three attempts topography maps to ensure that they Some practitioners, however, choose at improving the performance of the have the best outcomes. to charge per pair of lenses, where the lenses and are not satisfied, it is time to Orthokeratology is ideally suited overall cost includes professional care try a different approach. for low to moderate myopes and fits and the contact lenses. Patients replace with the demands of the 21st century their lenses as and when they want to Summary lifestyle. It is proven to be effective and can easily spend £700 per pair of Orthokeratology is a life-changing at controlling the development of lenses. therapy that gives your patients total myopia. Orthokeratology lenses are freedom with the safety of total only worn at night and used in the Troubleshooting reversibility. The process naturally home environment. These two factors Almost all lens suppliers will say that occurs in parts of the body. Wearing alone make the procedure a must for they achieve a success rate of between a ring leaves an imprint of the ring our younger patients. Orthokeratology 60 per cent to 80 per cent with the first on the finger. This is cell movement is a practice builder. ● pair of lenses, and in my experience caused by hydrostatic forces under the this is true. The caveat is that you select ring. If you leave the ring off for a few ● Shelly Bansal is a contact lens your patients carefully. They should weeks then the imprint disappears and practitioner practising in north London and meet the exclusion criteria, be highly the finger returns to its original shape. a former president of the BCLA

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