A silicone hydrogel contact lens produced less myopia progression than single vision spectacles in chinese children over a 6 month period

P. Lazon De La Jara, P. Sankaridurg, A. Ho, A. Martinez, L. Donovan, E.L. Smith, III, X.Chen, J.Ge, B. Holden, The Vision CRC Myopia Control Study Group.

INTRODUCTION

• Several myopia treatment options have been investigated to determine the effect of single vision spectacle lenses, progressive addition spectacle lenses, rigid gas permeable lenses and conventional soft contact lenses on myopia progression[1-5].
• No significant difference in myopia progression between single vision spectacle and single vision hydrogel contact lens wearers have been reported[4-5].
• However, a recent study reported less myopia progression with a silicone hydrogel contact lens when compared to low Dk/t hydrogel contact lenses[6]

PURPOSE

• To compare myopia progression in Chinese children after 12 months wear of single vision spectacles (SPL) and single-vision silicone hydrogel contact lens (SHCL).

MATERIALS AND METHODS

• Rates of progress of myopia over 12 months in myopic Chinese children aged 7 to 14 years (with baseline myopia between -0.75 to -3.50D of sphere and cylinder ≤1.00D) were measured at Zhongshan Ophthalmic Centre, Guangzhou, China for a group wearing single vision silicone hydrogel contact lens (SHCL Group, n=53, Lotrafilcon B, CIBA Vision, USA) and a group wearing normal sphero-cylindrical spectacles (SPL Group, n=41) from two myopia control studies.
• Cycloplegia was achieved with instillation of topical proparacaine hydrochloride 0.5% and Tropicamide1%, instilled 2 drops 5 minutes apart, with measurements 30 minutes after the second drop.
• Cycloplegic central refraction was measured with an open field autorefractor (Shin Nippon NVision K-5001, Japan) at baseline, 6 and 12 months.
• Axial length (AL) and corneal curvature was measured with an IOLMaster (Meditec Carl Zeiss, Germany) at baseline, 6 and 12 months.
• Peripheral refraction along the horizontal meridian (20°, 30° and 40° nasal and temporal fields) was measured with an open field autorefractor (Shin Nippon NVision K-5001, Japan) with and without correction at baseline.
• The relative peripheral refractive error (RPRE) was calculated evaluate the amount of peripheral refractive power with respect to central refraction at each field angle.
• The investigation was conducted in accordance with the tenets of the Declaration of Helsinki. Approval by local Human Research Ethics Committee was obtained and all subjects and/or guardians were required to sign a declaration of Informed Consent.
  

STATISTICAL ANALYSIS

• Participants' data from both eyes that satisfied the baseline sphere and cylinder criteria and completed the 12 month visit were included in the analysis dataset.
• The change in spherical equivalent (SE) and AL from baseline computed for each subject-eye and change in corneal curvature (from right eyes only) was compared between the two study groups at 6 and 12 months using a linear mixed model.
• Linear mixed model used in the analysis; adjusted for age, gender, parental myopia, baseline refractive error; and accounted for the within–subject correlated data.
• The difference in RPRE (dRPRE) with and without optical intervention was calculated and represents the amount of peripheral refraction change induced by the optical device. dRPRE (at each field angle, and across all field angles) was compared between groups using an Independent t-test.
• The level of statistical significance was set at 5% and data analysis was performed in SPSS (v17) and STATA (v10).
  

DEMOGRAPHICS

• No significant difference in age, gender and parental myopia distribution was found between the SPL Group and the SHCL Group (p>0.05).
  
• No significant difference in refractive error and AL was found between the SPL Group and the SHCL Group (SE -1.97±0.63D vs -2.24±0.74D, p=0.087 and AL 24.55±0.77mm vs 24.64±0.83mm, p=0.678 respectively).
  

MYOPIA PROGRESSION

• After adjusting for parental myopia, gender, age and refractive error at baseline, myopia progression was significantly less for the SHCL Group than the SPL Group at 6 months (p<0.001) and 12 months (p=0.012).
• AL increase was statistically significant less with the SHCL Group at the 6 month (p<0.001), however no difference was found at the 12 month visit (p=0.163).
• No change in corneal curvature was found at 6 and 12 month visits between groups (p> 0.05). Myopia progression was significantly affected by baseline age (p<0.05).
  

PERIPHERAL REFRACTION WITH AND WITHOUT CORRECTION

• Analysis of peripheral refraction results showed that SPL introduced greater amounts of peripheral hyperopic defocus than SHCL for 40° temporal, 20° and 30° nasal fields (p=0.015, p<0.001 and p<0.001, respectively) and averaged across all field angles (SPL Group=0.33±0.46D, SHCL Group=0.18±0.74D, =0.002).

CONCLUSIONS

• Myopia progression (as SE) was statistically significantly lower for the SHCL Group than for SPL Group after both 6 and 12 months.
  
• AL increase was statistically significantly lower for the SHCL Group than for SPL Group after 6 months. There was no difference in AL after 12 months between groups.
  
• The slower myopia progression rates observed with the SHCL cannot be explained by corneal curvature changes.
  
• The faster myopia progression observed for SPL may have been due to higher amounts of induced relative peripheral hyperopia with SPL than SHCL.
  

REFERENCES

1. Goss, D.A., Effect of bifocal lenses on the rate of childhood myopia progression. Am J Optom Physiol Opt, 1986. 63(2): p. 135-41.
   
2. Gwiazda, J., et al., A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. Invest Ophthalmol Vis Sci, 2003. 44(4): p. 1492-500.
   
3. Edwards, M.H., et al., The Hong Kong progressive lens myopia control study: study design and main findings. Invest Ophthalmol Vis Sci, 2002. 43(9): p. 2852-8.
   
4. Katz, J., et al., A randomized trial of rigid gas permeable contact lenses to reduce progression of children's myopia. Am J Ophthalmol, 2003. 136(1): p. 82-90.
   
5. Walline, J.J., et al., A randomized trial of the effect of soft contact lenses on myopia progression in children. Invest Ophthalmol Vis Sci, 2008. 49(11): p. 4702-6.
   
6. Blacker, A., et al., Myopia Progression During Three Years of Soft Contact Lens Wear. Optom Vis Sci, 2009.

ACKNOWLEDGEMENTS

The authors thank Thomas Naduvilath and Varghese Thomas for their support with statistical analysis and the clinical research team at Zhongshan Ophthalmic Centre, Guangzhou, China for data collection.

This research was funded by the Australian Government CRC Program, Institute for Eye Research (now Brien Holden Vision Institute) and CIBA Vision Grants.

Corresponding Author:
Percy Lazon de la Jara, PhD