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Essential Contact Lens Practice

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Essential Contact Lens Practice Contact Lens Monthly CET Essential contact lens practice Part 8 — Managing the presbyope Practitioners can expect a rise in presbyopic patients attending for contact lens fitting over the next few years. Jane Veys, John Meyler and Ian Davies continue their series by outlining the options and techniques available to correct presbyopia with contact lenses. C7603, three contact lens points suitable for optometrists, DOs and CLOs s the number of patients the same category as the presbyopic KEY POINTS wearing contact lenses emmetrope. The advantage of this around the world grows, technique is that the contact lens correc- ● The number of presbyopic patients so does the number requir- tion requires no modifications which, requiring contact lens correction is ing presbyopic correction. assuming that it is optimum at the time increasing and is predicted to continue AMany patients fitted with lenses are now of fitting, remains the case. to do so over the next five years ● In fitting the presbyope, the beginning to experience presbyopia and The obvious disadvantage is, of course, practitioner should have access to demand satisfactory correction without that the principal reason for contact lens a number of different lens designs recourse to spectacles. wear is being ignored. Contact lens and be aware of alternative fitting There is also the demand from presby- patients do not want to wear spectacles, approaches opic hyperopes who, on reaching presby- because, if they did, they would be doing ● The availability of single use opia, now need full-time correction for so already. Consequently pure contact disposable trial lenses allows distance and near and, with more active lens options should be explained first ease of trial for both patients and lifestyles and increased awareness of to the presbyopic contact lens wearers practitioners contact lenses, are asking for contact followed by spectacle correction option ● Lens power adjustments should lens correction. The number of presby- if appropriate. not be based on objective visual opic patients in Europe is on a steady acuity alone incline and is forecast to grow further Monovision ● Subjective visual performance over the next five years. Practitioners Monovision is the correction of one eye assessment is most effectively can therefore expect to see an increase with the distance prescription and the achieved by experiencing lens in the number of presbyopes attending contra-lateral eye with the near prescrip- wear in both the work and home for contact lens fittings over the next tion. It works on the principle that the environment few years. visual system can suppress the central ● There is a significant untapped As the size of the presbyopic market focus image and, thus, enable the object opportunity for contact lens correc- increases so to does the number of of interest to be seen clearly. Monovision tion of presbyopes options of correcting presbyopia with remains an effective means of correct- contact lenses. The history of contact lens ing presbyopia with contact lenses, and, correction of presbyopia has been one of products being launched onto the market with claims that have not always been Presbyopia and contact lenses realised in practice. This has led to scepti- cism by some practitioners and a reluc- Over-spectacles Bifocal CLs Monovision tance to fully embrace fitting presbyopes with multifocal contact lenses. Before RGP Soft looking at the techniques required to correct presbyopia with contact lenses, Alternating Simultaneous Simultaneous Alternating we should be aware of the available options as shown in Figure 1. eg Gelflex Triton Solid Fused Aspheric Multi-zone Aspheric Procornea Royal Spectacles Probably the most common method eg Acuvue Bifocal eg eg Frequency 55 of correcting the contact lens-wearing Centre distance Centre near Centre distance Tangent Streak Presbylite 2 Proclear Multifocal presbyope is with a pair of reading MagniVue spectacles worn over the distance contact lens correction. These may either eg eg be a full-frame single vision, multifocal Astrocom MF Focus Progressive or a half-eye depending on the needs Figure 1 Contact Quasar plus PureVision Multifocal Occasions of the individual. Such correction puts lens options for Aqualine MF 200 Biomedics 73 Menifocal Z Dailies Progressive the presbyopic contact lens wearer in presbyopes 24 | Optician | 05.10.07 opticianonline.net CET Contact Lens Monthly Relative success rate of monovision vs bifocal contact lenses 90% Monovision 80% Diractive Other 70% No dierence te ra 60% Figure 3 The principle of the translating bifocal contact lens ss cce 50% su (a) (b) of 40% tage en 30% rc Pe 20% 10% 0% Papas Back Harris Molinari Saunders Macalister et al1 et al2 et al3 Figure 2 Comparison of success rates of monovision with a variety of different Figure 4 (a) Triangle shape seg design (b) Triangle shape seg in primary position bifocal contact lenses of gaze as such, an understanding of its indica- In general, less compromised near lenses to stabilise the lens. tions and contraindications is essential to visual acuity performance in all illumi- the practitioner dealing with presbyopic nations provided by monovision is an Simultaneous vision designs patients. indication for consideration of this type Simultaneous vision bifocals rely on an Monovision clearly disrupts a patient’s of fitting option for presbyopes with optical system that places two images on stereopsis and, for some patients who strong near vision demands. Whereas the retina simultaneously and then relies have either little tolerance for visual when critical or sustained tasks requiring on the visual system to ‘select’ the clearer disruption or who are engaged in detailed good distance binocularity predominate, picture (versus monovision in which a visual tasks, this disruption might prove it is advisable to avoid monovision or to clear image is placed on each retina, the too great. While some investigators have consider supplementary correction. confusion occurring at a higher part of tried to develop predictive tests to assess the visual pathway). Early simultane- which patients might prove suitable Alternating bifocals ous vision bifocals had discrete zones of for monovision, these have not proved The alternating, or translating, bifocal distance and near vision (Figure 6). In to be as valuable as simply allowing was one of the first types of bifocal more recent designs, the power distri- the patient to try the lenses. An advan- contact lenses to be produced. The bution across the lens surface has been tage of monovision is that it allows the patient looks through the distance variable and lenses have been described practitioner to choose the most suitable portion of the optic zone in primary as multifocal, aspheric or progressive lens for the patient (such as the material gaze (Figure 3). On down gaze, the lens (Figure 7) and are available in both soft type and design) without having to add is held up against the lower eyelid, so and rigid materials. Other lens types the compromise that might exist with a the visual axis looks through the near use a ‘modified monovision’ approach particular bifocal design. portion. The advantage is that visual by using different bifocal designs in Whenever monovision has been quality will remain high as long as each eye. Alternatively lens designs can compared directly with current bifocal the visual axis is directed through the consist of a number of concentric zones or multifocal contact lens in controlled appropriate part of the lens. The disad- to control visual performance in varying clinical trials that have been published, vantage is that for this to occur signifi- illumination levels (Figure 8) or involve monovision has had a success rate equal cant eyelid/lens interaction needs to a combination of diffractive and refrac- to or above that of the bifocal in question occur, which can lead to decreased tive optics to achieve bifocal correction (Figure 2). However, since these studies patient comfort through increased (Figure 9). were carried out, many newer simulta- lens bulk and mobility. The majority There is potential for some confu- neous designs have been made available of alternating designs are available as sion in using the term multifocal or to practitioners. A more recent study rigid gas-permeable lenses. However, progressive because it implies a similar by Dutoit et al7 has shown that adapted more recently a number of soft alter- mechanism to a multifocal spectacle monovision wearers rated many aspects nating vision designs have become lens. In simultaneous vision contact of subjective vision performance higher available (Figure 4). The challenge lens systems, the basic principle of the with simultaneous vision bifocal contact is to produce a lens with a different- system remains the same irrespective of lenses. These included distance vision in powered near portion while maintain- whether the power varies in a discrete good and poor lighting, driving at night ing a smooth passage of the upper or progressive manner across the surface. and depth perception. Near vision in eyelid over the anterior surface. The Simultaneous vision contact lenses may poor lighting was rated higher during two distinct portions that make up an be further subdivided according to monovision wear. In addition, existing alternating lens may be either fused or whether the power distribution across successful monovision wearers when solid portions with a range of alterna- the surface is either centre-distance or refitted with simultaneous vision bifocal tive segment shapes (Figure 5). Prism, centre-near. contact lenses preferred the bifocal truncation or both controls lens stabil- The availability of single-use dispos- contact lens correction (68 per cent) ity, position and translation in rigid able soft trial lenses in newer designs, compared to monovison (25 per cent) designs. Soft lens designs use prism and daily disposable multifocals and silicone after a six-month trial.8 other design features used in soft toric hydrogel bifocals, as well as empiri- opticianonline.net 05.10.07 | Optician | 25 Contact Lens Monthly CET cally ordered aspheric RGP lenses, ope (up to +1.50D).
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