Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Randomized Controlled Trial
. 2021 Jul;41(4):702-714.
doi: 10.1111/opo.12834. Epub 2021 May 15.

One-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial

Biyue Guo  1 , Sin Wan Cheung  1 , Randy Kojima  2 , Pauline Cho  1
Affiliations
Randomized Controlled Trial

One-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: a prospective randomised clinical trial

Biyue Guo et al. Ophthalmic Physiol Opt. 2021 Jul.

Abstract

Purpose: To present the 1-year results of the Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study, which aims to investigate the myopia control effect of orthokeratology (ortho-k) lenses with different back optic zone diameters (BOZD).

Method: Children, aged 6 to <11 years, having myopia -4.00 D to -0.75 D, were randomly assigned to wear ortho-k lenses with 6 mm (6-MM group) or 5 mm (5-MM group) BOZD. Data collection included changes in refraction, vision, lens performance and binding, ocular health conditions, axial length and characteristics of the treatment zone (TZ) area.

Results: The 1-year results of 34 and 36 subjects (right eye only) in the 6-MM and 5-MM groups, respectively, are presented. No significant differences in baseline demographics were found between the groups (p > 0.05). The first-fit success rates, based on satisfactory centration at the 1-month visit, were 100% and 94% respectively. Horizontal TZ size was 0.92 mm and 0.72 mm smaller in the 5-MM group at the 6-month and 12-month visits, respectively (p < 0.05). At the 12-month visit, no significant between-group differences were found in the incidence of corneal staining (low grade only), lens binding and visual performance (all p > 0.05). Axial elongation was slower in the 5-MM group (0.04 ± 0.15 mm) than the 6-MM group (0.17 ± 0.13 mm) (p = 0.001). A significant positive correlation was observed between the horizontal TZ size and axial elongation (r = 0.36, p = 0.006).

Conclusion: Clinical performance of the two ortho-k lenses was similar, indicating that a smaller BOZD (5 mm) did not affect lens performance or ocular integrity. However, a smaller BOZD led to a reduced TZ, with retardation of axial elongation by 0.13 mm compared to conventional 6 mm BOZD ortho-k lenses after one year of lens wear.

Keywords: BOZD; myopia control; orthokeratology; treatment zone.

PubMed Disclaimer

Conflict of interest statement

All authors, except R Kojima, have no proprietary interest in any of the products mentioned. R Kojima is a Clinical Research and Development Director for Precision Technology Services (Vancouver, Canada), a partner in the KATT Design Group (Vancouver, Canada) and a clinical advisor to Medmont International Pty, (Nunawading, Australia).

Figures

Figure 1
Figure 1
Illustration of treatment zone determination with/without decentration. (a) no/mild decentration (b) inferior decentration (c) lateral decentration.
Figure 2
Figure 2
Flowchart showing subject recruitment and dropouts. (6‐MM, 5‐MM – wearing orthokeratology lenses of back optic zone diameter 6 and 5 mm, respectively.
Figure 3
Figure 3
Axial elongation from baseline over 12 months in the two groups of orthokeratology subjects. Error bars represents one standard deviation. (6‐MM, 5‐MM – wearing orthokeratology lenses of back optic zone diameter 6 and 5 mm, respectively).
See this image and copyright information in PMC

References

    1. Rudnicka AR, Kapetanakis VV, Wathern AK et al. Global variations and time trends in the prevalence of childhood myopia, a systematic review and quantitative meta‐analysis: implications for aetiology and early prevention. Br J Ophthalmol 2016; 100: 882–890. - PMC - PubMed
    1. Ding BY, Shih YF, Lin LL, Hsiao CK & Wang IJ. Myopia among schoolchildren in East Asia and Singapore. Surv Ophthalmol 2017; 62: 677–697. - PubMed
    1. Yotsukura E, Torii H, Inokuchi M et al. Current prevalence of myopia and association of myopia with environmental factors among schoolchildren in Japan. JAMA Ophthalmol 2019; 137: 1233–1239. - PMC - PubMed
    1. Tsai TH, Liu YL, Ma IH et al. Evolution of the prevalence of myopia among Taiwanese schoolchildren: a review of survey data from 1983 through 2017. Ophthalmology 2021; 128: 290–301. - PubMed
    1. Yam JC, Tang SM, Kam KW et al. High prevalence of myopia in children and their parents in Hong Kong Chinese Population: the Hong Kong Children Eye Study. Acta Ophthalmol 2020; 98: e639–e648. - PubMed

Publication types