Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study: A 2‐year randomised clinical trial

Abstract

PurposeTo compare axial elongation (AE) and treatment zone (TZ) characteristics in children wearing 6 mm or 5 mm back optic zone diameter (BOZD) orthokeratology (ortho‐k) lenses over 2 years.MethodsForty‐five (6 to <11 years of age) myopic (−4.00 to −0.75 D) children of Chinese ethnicity were randomly assigned to use the two different lens designs (23 and 22 wore the 6 and 5 mm lenses, respectively). Data collection was performed at baseline and every 6‐months after commencing lens wear.ResultsAfter 24 months, subjects wearing lenses with a 5 mm BOZD achieved smaller TZ diameter (horizontal: 2.69 ± 0.28 vs. 3.84 ± 0.39 mm; vertical: 2.65 ± 0.22 vs. 3.42 ± 0.34 mm, p < 0.001) and less AE (0.15 ± 0.21 vs. 0.35 ± 0.23, p = 0.005) compared to those using the 6 mm design, with no difference in choroidal thickness (ChT) changes (p = 0.93). A significant increase in ChT, using pooled data analysis, was noted at the 6‐month (11.8 ± 19.77 μm, p < 0.001) and 12‐month (12.0 ± 23.7 μm, p = 0.004) visits, compared to baseline, indicating a transient change in ChT. Significant associations were noted, using linear mixed models, between AE and the TZ diameters (p < 0.003) after adjusting for baseline data. A very weak association was found between ChT changes and AE, with the effect size close to zero.ConclusionsSmaller BOZD ortho‐k lenses resulted in a smaller TZ diameter, which was associated with less AE after 2 years of treatment. The changes in ChT played a very weak role, suggesting that other factors may contribute more to the reduced AE in subjects wearing lenses having a smaller BOZD.

The Montreal Experience: Impact of Different Orthokeratology Lens Designs on Corneal Treatment Zone Characteristics

“…OK 1 is associated with higher AL growth [14]. This finding is consistent with the results of different studies [20,22], reporting better control of axial elongation when a smaller treatment zone is present on the cornea. The width of the area producing this defocus is the second factor to consider.…”

“…The efficiency of axial length management seems to be influenced by this optical zone difference [21,22]. A larger back optical zone diameter (BOZD) results in a significantly larger treatment zone diameter molded on the cornea, which is associated with higher axial elongation after 2 years of treatment [22].…”

“…The efficiency of axial length management seems to be influenced by this optical zone difference [21,22]. A larger back optical zone diameter (BOZD) results in a significantly larger treatment zone diameter molded on the cornea, which is associated with higher axial elongation after 2 years of treatment [22]. This article aims to analyze the changes in the corneal profile before and after lens wear in the Montreal Experience orthokeratology cohort using four OK lens designs, in order to better understand the optical differences that led to this efficiency gap found in the Montreal Experience part 1 [14].…”

Myopia Control: Are We Ready for an Evidence Based Approach?

“…The effect of OK, as well as the effect of previously described myopia control SCL, seems to be stronger in individuals with large pupils, while a reduced effect of OK lenses was reported in the presence of astigmatism [192,193]. Three articles on RCTs were further identified and included in this review (Supplementary Table 5) [194][195][196]. Corneal staining is the most common complication in OK treatment, and the frequency and severity of staining are associated with overnight lens wear [197][198][199].…”