Optometry & Vision Science:
The Effect of Multifocal Soft Contact Lenses on Peripheral Refraction
Kang, Pauline*; Fan, Yvonne†; Oh, Kelly†; Trac, Kevin†; Zhang, Frank†; Swarbrick, Helen A.*
School of Optometry and Vision Science, The University of New South Wales, Sydney, New South Wales, Australia. e-mail: firstname.lastname@example.org
Purpose: To compare changes in peripheral refraction with single-vision (SV) and multifocal (MF) correction of distance central refraction with commercially available SV and MF soft contact lenses (SCLs) in young myopic adults.
Methods: Thirty-four myopic adult subjects were fitted with Proclear Sphere and Proclear Multifocal SCLs to correct their manifest central refractive error. Central and peripheral refraction were measured with no lens wear and subsequently with the two different types of SCL correction.
Results: At baseline, refraction was myopic at all locations along the horizontal meridian. Peripheral refraction was relatively hyperopic compared with center at 30 and 35 degrees in the temporal visual field (VF) in low myopes, and at 30 and 35 degrees in the temporal VF, and 10, 30, and 35 degrees in the nasal VF in moderate myopes. Single-vision and MF distance correction with Proclear Sphere and Proclear Multifocal SCLs, respectively, caused a hyperopic shift in refraction at all locations in the horizontal VF. Compared with SV correction, MF SCL correction caused a significant relative myopic shift at all locations in the nasal VF in both low and moderate myopes and also at 35 degrees in the temporal VF in moderate myopes.
Conclusions: Correction of central refractive error with SV and MF SCLs caused a hyperopic shift in both central and peripheral refraction at all positions in the horizontal meridian. Single-vision SCL correction caused the peripheral retina, which initially experienced absolute myopic defocus at baseline with no correction to experience an absolute hyperopic defocus. Multifocal SCL correction resulted in a relative myopic shift in peripheral refraction compared with SV SCL correction. This myopic shift may explain recent reports of reduced myopia progression rates with MF SCL correction.
Myopia is typically caused by the axial length of the eye exceeding the focal length formed by the ocular refractive components and is thus termed “axial myopia.” Elongation of the eye is usually caused by an increase in vitreous chamber depth.1,2 It has been approximated that a 0.35-mm increase in axial length will result in 1 diopter (D) of myopia progression.3,4 Excessive elongation evident in high myopes (greater than −6 D) increases the risk of development of numerous sight-threatening conditions, including glaucoma,5–7 cataract,8 maculopathies,9,10 as well as various pathological vitreal and retinal changes.7,11–13 With increase in myopia prevalence worldwide,14–18 and in particular in Asia,19–24 there is a demand for methods to potentially slow down or stop the progression of myopia.
Animal studies have provided a plethora of evidence on the influence of the environment or visual input on the development of refractive error. Animals have been found to respond to a range of lens-induced defocus with the response being locally mediated.25 Traditionally, studies have explored the effect of foveal defocus on refractive development. More recently, animal studies have investigated the effects of defocus on the peripheral retina and have revealed that the peripheral defocus seems to have an important influence on the emmetropization process, more than previously believed to be true.26–29 These findings have been supported by human studies that have suggested that relative peripheral hyperopia commonly seen in myopic individuals may be a myopiogenic factor.30,31 The eye experiences hyperopic defocus on the peripheral retina with conventional optical corrections, and it has been reported that the amount of relative peripheral hyperopia increases32,33 or remains unchanged34 with spectacle lens wear, whereas conflicting results have been reported with soft contact lens (SCL) wear. It has been proposed that the eye responds to this peripheral hyperopic stimulus by growing in axial length to bring the peripheral retina in coincidence with the image, despite the increase in foveal myopia.35,36 Imposing myopic defocus onto the peripheral retina could potentially slow or stop axial elongation and hence myopia progression.36
The effects of three commercially available spherical single-vision (SV) SCLs (Acuvue 2, Acuvue 1-day Moist; Johnson & Johnson Vision Care, USA; and Proclear Sphere; Coopervision, Fairport, NY) on peripheral refraction have been investigated. Shen et al.37 and Backhouse et al.34 found that Acuvue 2 and Acuvue 1-Day Moist SCLs, respectively, decreased the amount of relative peripheral hyperopia in myopes, whereas Kang et al.38 measured an increase in relative peripheral hyperopia in myopes fitted with Proclear Sphere SCLs. These differences may be caused by differences in SCL design and power profile.
Two multifocal (MF) SCLs with plus peripheral powers have recently been developed to induce myopic peripheral field curvatures as potential forms of myopia control. The Dual-Focus lens (MiSight; Coopervision) was developed and investigated by Anstice and Phillips39 in New Zealand and is currently available in Hong Kong, Singapore, Malaysia, and selected sites in Australia and New Zealand. This concentric design MF SCL has a central distance correction zone with two concentric +2.00 DS peripheral treatment zones. The Anti-Myopia Contact Lens (AMCL; Australia) is another novel MF SCL with a progressive power profile that was developed by the Brien Holden Vision Institute (Sydney, Australia). This lens is currently not commercially available. The AMCL is a silicone hydrogel SCL with a central 3-mm diameter distance zone surrounded by an annular treatment zone. There is a gradual increase in relative plus power to +2.00 D at the edge of the 9-mm-diameter treatment zone.40
In the current SCL market, there are two conventional MF SCLs, Proclear Multifocal and Proclear Biofinity Multifocal, originally designed for presbyopic correction, which are of a similar design to the described AMCL. Both the Proclear and Biofinity Multifocal SCLs have a central distance correction zone surrounded by a single peripheral plus power annulus. Another commercially available MF SCL with a similar design to the Dual-Focus lens is the Acuvue Bifocal (Johnson & Johnson Vision Care), which also has a concentric design with a central distance correction zone surrounded by alternating plus power and distance correction annular zones. However, this lens is not widely used because of improved silicone hydrogel MF SCL designs that have superseded the Acuvue Bifocal SCL. As the Proclear Biofinity MF SCL range was not available to us at the time of study measurements, the current study aimed to investigate the effects of Proclear Multifocal SCLs on peripheral refraction in young myopic adults.
Objective refraction measurements were taken along the horizontal meridian in the naked eye. Subjects were then fitted with SV SCLs in the right eye to correct their manifest central refraction and after a 5-minute washout period of no lens wear, subjects were refitted with an MF SCL with distance center and near add periphery design.
Objective central and peripheral refraction measurements were taken with each type of SCL correction. After a settling time of approximately 5 minutes, measurements with each lens type required about 5 minutes of SCL wear. Therefore, including the washout period, study measurements required approximately 25 minutes.
Thirty-four young-adult myopic subjects were enrolled (age range, 18 to 29 years; 20 women, 14 men). All subjects gave their informed written consent to study participation after being informed about the nature and possible consequences of participating in the study. This study followed the tenets of the Declaration of Helsinki, and approval was obtained from the institutional Human Research Ethics Advisory (HREA) panel before study commencement. Subjects were screened before enrollment and found to be in good general health and free from ocular disease.
Inclusion criteria required that subjects were nonrigid gas-permeable lens wearers, and SCL wearers were instructed to cease lens wear at least 24 hours before measurements. Central refraction ranged between −0.75 and −6.00 DS spherical equivalent or M, with −0.75 DC or less. Subjects were stratified into two groups depending on their M refraction. Central M between −0.75 and −2.00 DS inclusive was categorized as low myopia and subjects with central M between −2.25 and −6.00 DS inclusive were categorized as moderate myopes.
Subjects were initially fitted with Proclear Sphere SCLs (Coopervision) made from omafilcon A (62% water content) in the right eye. Proclear Sphere SCLs have a diameter of 14.2 mm and base curve of 8.6 mm. Subjects were subsequently fitted with Proclear Multifocal SCLs (Coopervision) in the right eye. Proclear Sphere and Multifocal SCL powers were chosen with the same vertex adjusted subjective distance central refractive error correction for each subject. Proclear Multifocal SCLs have a 2.3-mm central zone dedicated to central refractive error correction. This is surrounded by an aspheric annular zone with a progressive plus power profile designed to give a +2.00 DS peripheral addition, and this blended treatment zone has a diameter of 8.5 mm. Proclear Multifocal SCLs are also made from omafilcon A and have a total diameter of 14.4 mm and a base curve of 8.7 mm.
Centration, coverage, movement, and tightness of each lens were assessed to confirm clinically acceptable fits before any measurements were taken. Soft contact lenses showing centration that allowed complete corneal coverage, up to 1 mm movement on blink and 50 ± 15% lens tightness were considered clinically acceptable.
Subjective Central Refraction
Noncycloplegic central refraction was measured using the technique of maximum plus for best visual acuity to determine monocular subjective sphere end point41 while astigmatism power and axis were determined by the Jackson Cross Cylinder method.42 Subjective refraction allowed selection of appropriate SV and MF lenses to give full correction of manifest central distance spherical equivalent refractive error.
Noncycloplegic central and peripheral refraction measurements were taken using the Shin-Nippon NVision-K 5001 autorefractor (Tokyo, Japan). Refraction measurements were taken with no SCLs and subsequently with SV and MF SCLs at center and 10, 20, 30, and 35 degrees in the nasal and temporal VF across the horizontal meridian. Five measurements were taken at each location and averaged. Conventional sphero-cylindrical refractive error (S/C × θ) measured by the autorefractor was converted into power vectors M (spherical equivalent), J180 (90 to 180-degree astigmatic component) and J45 (45 to 135-degree astigmatic component) to allow for statistical analysis using the method derived by Thibos et al.43
Peripheral refraction measurements were taken using a fixation device that projected a green monochromatic laser spot target on a wall. The green monochromatic target was selected to ensure accurate fixation with minimal accommodative effect. The target was rotated along the horizontal meridian, and subjects were asked to rotate their eyes to follow the fixation spot for eccentric measurements. Eye rotation has been reported not to interfere with peripheral refraction measurements.44 Furthermore, although target vergence during measurements varied between 0.23 and 0.46 D in our clinical setting, it has been shown that up to 2 D of accommodation has very little effect on peripheral refraction for eccentric fixation angles up to 30 degrees.45
A pilot study, conducted on 17 young-adult subjects in our clinical setting, demonstrated high intersession repeatability of peripheral refraction measurements taken with the Shin-Nippon NVision-K 5001 autorefractor. Refraction measurements were taken at center and at ±10 and ±30 degrees in the nasal and temporal VF across two measurement sessions, approximately 1 week apart. Differences of 0.14 D or less for all refraction components were found for repeated measurements.
Repeated-measures ANOVA was used to analyze refraction across the horizontal meridian with no lens wear. Doubly MANOVA with planned contrasts or post hoc t tests protected by Bonferroni correction was used to assess for changes from baseline in peripheral refraction with each type of SCL correction and to also assess for differences in peripheral refraction profile between the different types of correction (SPSS v.18, Chicago, IL). Mauchly’s test was used to test for sphericity, and if significant, the Greenhouse-Geisser correction was applied. A value of p < 0.05 denoted statistical significance.
Mean objective central refraction at baseline and number of subjects are shown in Table 1 for both low and moderate myopes. Baseline relative peripheral refraction profiles in low and moderate myopes are illustrated in Fig. 1.
Spherical Equivalent, M
Changes in peripheral refraction with SV correction in both low and moderate myopes have been reported in detail elsewhere.38 In brief, SV correction of central M caused a significant hyperopic shift in raw peripheral refraction at all locations along the horizontal meridian in both low (p < 0.001) and moderate myopes (p < 0.001) as shown in Figs. 2A and 3A, respectively. Compared with no correction, SV SCLs caused an increase in relative peripheral hyperopia at 35, 30, and 20 degrees in the temporal VF (FT35 = 4.664, p = 0.046; FT30 = 6.732, p = 0.020; FT20 = 5.396, p = 0.034) and 30 and 35 degrees in the nasal VF (FN30 = 11.803, p = 0.003; FN35 = 5.776, p = 0.029) (Fig. 2B) in low myopes. Similarly, greater amounts of relative peripheral hyperopia were measured with full-correction SV SCLs compared with no correction at all positions in the temporal VF (FT35 = 17.467, p = 0.001; FT30 = 25.012, p < 0.001; FT20 = 9.961, p = 0.006; FT10 = 9.734, p = 0.007) and at 10, 30, and 35 degrees in the nasal VF (FN10 = 4.597, p = 0.048; FN30 = 11.620, p = 0.004; FN35 = 10.383, p = 0.005) in moderate myopes (Fig. 3B).
Multifocal correction also caused a hyperopic shift in peripheral refraction at all locations in low myopes as demonstrated in Fig. 2A. The relative peripheral refraction profile was similar between no correction and SV and MF corrections in the temporal VF (Fig. 2B). However, there was significant myopic shift in relative peripheral refraction in the nasal VF (FN10 = 9.217, p = 0.008; FN20 = 29.491, p < 0.001; FN30 = 45.328, p < 0.001; FN35 = 18.799, p = 0.001) with MF compared with SV correction (Fig. 2B). Multifocal correction also caused a hyperopic shift in peripheral refraction at all locations in moderate myopes (Fig. 3A). Moreover, overall differences in relative peripheral refraction profile between full SV and MF correction were found (F = 16.880, p < 0.001), which were confirmed by post hoc tests specifically at 35 degrees in the temporal VF (FT35 = 8.039, p = 0.012) and all locations in the nasal VF (FN10 = 0.909, p = 0.003; FN20 = 54.100, p < 0.001; FN30 = 71.018, p < 0.001; FN35 = 50.385, p < 0.001) as illustrated in Fig. 3B.
Peripheral Astigmatism (J180 and J45)
Single-vision and MF correction caused significant changes in the J180 profile (F = 3.514, p < 0.01) in low myopes. Compared with no correction, SV correction caused significant changes in the J180 profile (F = 4.220, p = 0.027) with post hoc t tests revealing a positive increase in J180 at 35 degrees in the temporal (p = 0.024) and nasal VF (p = 0.014). Multifocal lenses caused a significant negative increase at 10 (p < 0.001), 20 (p < 0.001), and 30 degrees (p = 0.002) in the nasal VF only compared with no correction. In addition, a significant difference in J180 was found between SV and MF correction in low myopes at 10 (p < 0.001), 20 (p < 0.001), 30 (p = 0.017), and 35 degrees (p = 0.033) in the nasal VF. There was a negative increase in J180 with MF lens wear compared with SV (Fig. 4A).
Similarly, compared with no correction, SV and MF correction caused a significant change in the J180 profile (F = 2.720, p = 0.003) in moderate myopes as shown in Fig. 4B. Single-vision SCL correction caused a positive increase in J180 at 30 degrees (p = 0.004) in the temporal VF and at 30 (p = 0.018) and 35 degrees (p = 0.003) in the nasal VF, as indicated by post hoc t tests. Furthermore, compared with no correction, MF SCLs caused a negative increase at 10 (p = 0.023) and 30 degrees (p = 0.021) in the nasal VF. In addition, compared with SV correction, MF correction caused a negative shift in J180 at 10 (p = 0.012), 20 (p = 0.014), 30 (p = 0.001), and 35 degrees (p = 0.001) in the nasal VF in moderate myopes.
Although doubly MANOVA indicated an overall significant change in J45 profile with SV correction, post hoc t tests revealed no statistically significant change from baseline at any specific point on the VF in low myopes. Multifocal SCL correction caused a significant positive increase in J45 at 35 (p = 0.020) and 30 degrees (p = 0.012) in the temporal VF compared with no correction. However, there was no significant difference in J45 profile between SV and MF correction in low myopes (Fig. 5A). Compared with no correction, in moderate myopes, there was a positive increase in J45 at 35 degrees (p = 0.002) in the temporal VF with SV correction. Similarly, a positive increase in J45 was measured with MF correction compared with no correction at 35 (p < 0.001) and 30 degrees (p = 0.034) in the temporal VF. Compared with SV correction, there was a negative increase in J45 at 20 degrees (p = 0.004) in the nasal VF with MF correction (Fig. 5B) in the moderate myope group.
Experimental animal studies investigating vision-dependent mechanisms that regulate refractive error development have demonstrated that, contrary to traditional belief, refractive error development seems to be influenced more by peripheral defocus than previously believed.27,28 Recently, Smith et al.26 imposed hyperopic peripheral defocus with unrestricted central vision in infant rhesus monkeys with intact and photoablated foveas. Imposing this hyperopic defocus in the periphery was found to promote the development of central axial myopia in the presence of both functioning and nonfunctional foveas. Liu and Wildsoet29 demonstrated in the chick eye model that a plano center and +5 D periphery concentric bifocal spectacle lens tended to produce central hyperopia coupled with apparent inhibition of axial length elongation. More recently, Ho et al.46 demonstrated differences in human retinal electrical response to defocus with the paracentral retina responding more strongly to defocus compared with the central retina, further supporting the theory that refractive error development is more influenced by peripheral visual signals. Consequently, it has been hypothesized that inducing a myopic defocus onto the peripheral retina of progressive myopes might potentially slow or stop the progression of central myopia.36 Therefore, optical means of manipulating peripheral vision have become of great interest and may provide a possible strategy for myopia control in humans.
Antimyopia MF SCLs with plus power in the periphery to induce myopic defocus onto the peripheral retina have been developed as a means of myopia control. However, there are commercially available MF SCLs, traditionally fitted for presbyopic correction, which have similar designs to these novel antimyopia SCLs. The purpose of this study was to determine the effects of Proclear Multifocals (Coopervision), a commercially available SCL that has a distance center correction and a plus add (+2.00 DS) periphery design, on peripheral refraction in young adult myopes compared with SV SCLs.
Myopic shifts in relative peripheral refraction profiles were found in both low and moderate myopes wearing MF compared with SV SCLs. Although an absolute myopic defocus was apparent at most eccentric locations in both low and moderate myopes, a full +2.00 D myopic shift in peripheral refraction was not measured. This is likely to be caused by the autorefractor averaging refraction across its 2.3-mm measurement ring rather than measuring refraction at a single defined point on the retina. The myopic shift was more apparent in the nasal compared with the temporal VF, and this is likely to be caused by temporal decentration of SCLs, an effect which has been previously noted.40,47 As animal studies have suggested that the effects of optical defocus on refractive error seem to be locally mediated,25 this asymmetric refractive shift induced by MF SCLs must be viewed with caution. Corresponding regional changes in ocular shape have been demonstrated with optical defocus induced over restricted retinal regions in primates,48,49 and thus, there is a possibility that MF SCLs may promote undesirable asymmetric ocular growth in human myopes. Future longitudinal studies on the effects of MF SCLs on ocular shape are indicated. Furthermore, eyes that demonstrate poor SCL centration may not be suitable to wear MF SCLs as a potential form of myopia control.
Lopes-Ferreira et al.47 also measured peripheral refraction changes with Proclear MF SCLs, focusing on changes in relative peripheral refraction. Twenty emmetropic subjects were fitted with plano center and plus add periphery Proclear MF SCLs. Exploring four different peripheral add values, they reported no significant difference in peripheral refraction profiles from baseline with a plano center and +1.00 D add power Proclear MF SCL. With a plano center and +2.00 D periphery add, they found an approximate 0.87 D shift in refraction across the horizontal VF, with no significant change in relative peripheral refraction profile. Proclear MF SCLs with a +3.00 D and +4.00 D periphery add were found to induce a significant myopic shift peripherally, causing relative peripheral refraction to become more myopic compared with baseline. A simultaneous myopic shift was measured centrally, which the authors believed was an artifact of the autorefractor measurement ring overlapping the central and peripheral correction zones. A similar central myopic shift was also demonstrated in the present study. M measured at the center of the VF was more myopic compared with SV SCLs despite selection of the same full-distance refraction correction in both lens designs. This is likely to be caused by the design of the Proclear Multifocal SCL and the size of the autorefractor measurement ring. The central 2.3-mm spherical zone of a Proclear Multifocal SCL is dedicated to the selected distance correction beyond which the peripheral add is introduced into the design of the contact lens. As central objective refraction measurements were taken in alignment with the entrance pupil and not the geometric center of the cornea, it is likely that the 2.3-mm measurement ring of the autorefractor measured the majority of the distance correction zone and included some of the peripheral add zone, resulting in an overall myopic central M value.
More recently, Ticak and Walline50 and Rosen et al.51 also measured peripheral optical changes with the same Proclear Multifocal lens design. Ticak and Walline50 compared peripheral refraction changes with those with orthokeratology lens wear and found that peripheral refraction with MF SCLs was relatively more hyperopic at all measured locations along the horizontal and vertical meridians except at 10 degrees in the temporal VF compared with orthokeratology. However, this study primarily considered the relative changes in peripheral refraction induced by orthokeratology and MF SCL wear. Rosen et al.51 used a more sophisticated methodology and measured peripheral optical changes with MF SCL wear using a Hartmann-Shack wavefront sensor but on a limited sample of four subjects. The modified Hartmann-Shack wavefront sensor can measure peripheral aberrations out to ±40 degrees along the horizontal VF meridian in 1-degree intervals, providing a more comprehensive analysis of peripheral optical changes. However, with MF SCL wear, image quality was found to be severely degraded beyond 30 degrees (because of the border of the optical zone of the MF SCL), which made measurements beyond 30 degrees inaccurate. Nevertheless, Rosen et al.51 found only around 0.5 D of induced relative peripheral myopia at 30 degrees in the nasal VF, similar to results of this study and that by Lopes-Ferreira et al.47
In our study, SV and MF SCL wear caused significant changes in the J180 and J45 profiles. However, these changes were 0.28 D or less, which could be considered clinically insignificant. Overall defocus and peripheral astigmatism contribute to peripheral blur, but the effect of this blur on refractive error development is unclear. Many reports, including the present study, discuss the role of peripheral myopia or hyperopia as defined by the spherical equivalent (M) of the measured peripheral refractive error. However, the human eye experiences oblique astigmatism, which becomes more apparent with greater visual field eccentricity. It has been proposed recently by Howland52 and discussed further by Charman53 that the tangential and sagittal focus planes rather than the spherical equivalent or circle of least confusion may be responsible for the peripheral retina detecting the direction of defocus and hence guiding emmetropization. It has been proposed that the eye may grow in axial length until the sagittal and tangential signals become similar in strength. However, there is limited research on this proposal, and further investigation is required.
As previously mentioned, Proclear Multifocal SCLs used in this study are of similar design to MF SCLs that have been specifically developed for potential myopia control. The AMCL is a silicone hydrogel SCL designed to induce myopia on to the peripheral retina. The design of this contact lens is described in detail elsewhere.40 Axial length increase after 12 months of AMCL wear in 43 children of Chinese ethnicity was 0.27 mm (95% confidence interval, 0.22 to 0.32 mm) and 0.40 mm for 39 spectacle lens wearers (95% confidence interval, 0.35 to 0.45 mm), equivalent to approximately 33% less myopia progression in the AMCL group. Compared with spectacle lens wearers, myopic shift in relative peripheral refraction was found in children wearing these novel SCLs at 20, 30, and 40 degrees in the nasal VF and at 30 and 40 degrees in the temporal VF.40 A more myopic relative peripheral refractive profile was found with the AMCL compared with baseline.
The Dual-Focus lens, commercially known as the MiSight lens (Coopervision), was developed and investigated by Anstice and Phillips39 who similarly demonstrated reduced myopia progression with these MF SCLs in a group of 40 myopic children aged between 11 and 14 years. Subjects were randomized to wear the Dual-Focus lens in one eye and an SV SCL in the contralateral eye for 10 months (period 1). Lens assignment was then swapped for the second 10 months (period 2). During period 1, axial length elongation of 0.11 ± 0.09 mm compared with 0.22 ± 0.09 mm was measured in the eyes wearing the Dual-Focus lens and SV SCL, respectively. After the crossover period, the eye now wearing the Dual-Focus lens was reported to show axial elongation of 0.03 ± 0.10 mm compared with the eye now wearing SV SCLs, which had axial elongation of 0.14 ± 0.09 mm. We are unaware of any published reports on peripheral refraction changes with the Dual-Focus lens.
Although the described antimyopia MF SCLs have been developed based on the hypothesis that peripheral hyperopia, present in a typical myope, may stimulate central myopia development, there have been studies contradicting this hypothesis. Sng et al.54 found that the development of myopia was associated with a change in peripheral refraction from relative myopia to relative hyperopia, indicating that peripheral refraction may be more a reflection of ocular shape change rather than being a myopiogenic factor. Furthermore, analysis of results from the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) study found no significant association between the amount of relative peripheral hyperopia and risk of onset of central myopia.55 However, it must be noted that peripheral refraction was measured in only one position (30-degree temporal gaze) in the entire VF. Very recently, Jaeken and Artal56 measured peripheral optical quality using a Hartmann-Shack wavefront sensor. Peripheral defocus and oblique astigmatism were found to be the main contributors to degradation of the peripheral image in both emmetropic and myopic eyes. Furthermore, they found the amount of peripheral blur to be similar between the two refractive groups and therefore argued against the hypothesis of retinal defocus influencing refractive error development. They proposed that if emmetropization is driven by peripheral blur, differences in peripheral blur would be expected between emmetropic and myopic eyes. However, this was not the case.
Despite conflicting reports and new perspectives on the theory of myopia control through manipulation of peripheral defocus, studies have shown that optical methods that reduce the amount of hyperopia induced onto the peripheral retina, in particular the antimyopia MF SCLs,39,40 seem to slow down the progression of myopia. In this study, refraction measured with the Proclear MF SCLs with center distance correction and +2.00 D add periphery was myopic at most locations along the horizontal VF meridian. According to the peripheral defocus hypothesis, this peripheral myopia may be antimyopiogenic. For clinicians who do not have access to the MiSight or Dual-Focus lenses, the results from this study suggest that the Proclear MF SCL can be used as an alternative for potential myopia control in progressive myopic children, although caution must be taken as induced peripheral refraction profiles with MF SCLs were found to be asymmetric in this study. Thus, myopic children with poor lens centration may not be suitable for myopia control with MF SCLs. However, studies of the long-term efficacy of MF SCL wear for myopia control in children are lacking, and further research is indicated.
School of Optometry and Vision Science
University of New South Wales
Sydney, New South Wales 2052
We thank Coopervision Australia for donation of lenses used in the study.
This research was funded through the Australian Research Council Linkage Project Grant scheme with support from industry partners Boston Products Group of Bausch & Lomb (USA), BE Enterprises Pty. Ltd., and Capricornia Contact Lens Pty. Ltd. (Australia).
Portions of this data were presented at the 16th Scientific Meeting of the International Society for Contact Lens Research (ISCLR), 2011, Napa Valley, CA.
Received September 3, 2012; accepted April 17, 2013.
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peripheral refraction; soft contact lenses; multifocal soft contact lenses; myopia; myopia progression
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