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To compare the value of pre-treatment axial elongation (AE) and changes in refractive sphere (M change) for predicting the success in orthokeratology (ortho-k), in order to better identify suitable candidates for myopia control. This study further analysed the data of 66 subjects receiving 7-month ortho-k treatment, following a 7-month observation period, during which single-vision spectacles were worn. Rate of myopia progression was determined by AE and M change and subjects categorised as slow, moderate, or rapid progressors based on these changes. Outcomes of myopia control, based on the AE reduction after ortho-k, were classified as 'ineffectual', 'clinically insignificant', or 'beneficial'. Of the 20 subjects, initially categorised as slow by AE and, of whom 95% were similarly categorised by M change, none benefitted from ortho-k. In contrast, of the 22 subjects with moderate AE, 77% and 23% displaying slow and moderate M change, respectively, the majority (73%) benefitted from ortho-k lens wear. The 24 subjects with rapid AE were poorly identified by M change, with only 21% correctly categorised. The vast majority of rapid progressors showed significant benefit after ortho-k. Progression of AE is a good indicator of subsequent success of ortho-k treatment. Delaying commencement of therapy is prudent for children with slow progression as results indicate that they would be unlikely to benefit from this intervention. As change in refractive error frequently underestimates rapid progression of AE, its value for identifying appropriate candidates for myopia control is poor.

This retrospective longitudinal analysis aimed to investigate the association between ocular higher-order aberrations (HOAs) and axial eye growth in Hong Kong children. Measures of axial length and ocular HOAs under cycloplegia were obtained annually over a two-year period from 137 subjects aged 8.8 ± 1.4 years with mean spherical equivalent refraction of −2.04 ± 2.38 D. A significant negative association was observed between the RMS of total HOAs and axial eye growth ( P  = 0.03), after adjusting for other significant predictors of axial length including age, sex and refractive error. Similar negative associations with axial elongation were found for the RMS of spherical aberrations ( Z 4 0 and Z 6 0 combined) ( P  = 0.037). Another linear mixed model also showed that greater levels of vertical trefoil ( Z 3 − 3 ) , primary spherical aberration ( Z 4 0 ) and negative oblique trefoil ( Z 3 3 ) were associated with slower axial elongation and longer axial length (all P  < 0.05). These findings support the potential role of HOAs, image quality and a vision-dependent mechanism in childhood eye growth.

Purpose To compare changes in ocular aberrations in children wearing orthokeratology (ortho-k) lenses with a back optic zone diameter (BOZD) of 6 mm (6-MM group) or 5 mm (5-MM group) and their associations with axial elongation (AE) over two years. Methods Seventy Chinese children, aged 6 to < 11 years, with myopia between − 4.00 to − 0.75 D, were randomly allocated to 5-MM and 6-MM groups. Ocular aberrations were measured, rescaled to a 4-mm pupil, and fitted with a 6th order Zernike expansion. Measurements, including axial length, were taken prior to commencing ortho-k treatment and then every six months over two years. Results After two years, the 5-MM group displayed a smaller horizontal treatment zone (TZ) diameter (by 1.14 ± 0.11 mm, P  < 0.001) and less AE (by 0.22 ± 0.07 mm, P  = 0.002) compared with the 6-MM group. A greater increase in total root mean square (RMS) of higher-order aberrations (HOAs), primary spherical aberration (SA) ( C 4 0 ) , and coma were also observed in the 5-MM group at all follow-up visits. The horizontal TZ diameter was significantly associated with changes in RMS HOAs, SA (RMS, primary and secondary SA), and RMS coma. After controlling for baseline parameters, RMS HOAs, RMS SA, RMS coma, and primary ( C 4 0 ) and secondary ( C 6 0 ) SA were significantly associated with AE. Conclusions Ortho-k lenses with a smaller BOZD created a smaller horizontal TZ diameter and a significant increase in total HOAs, total SA, total coma, and primary SA and a decrease in secondary SA. Of these ocular aberrations, total HOAs, total SA, and primary SA were negatively correlated with AE over two years. Trial registration : ClinicalTrial.gov, NCT03191942. Registered 19 June 2017, https://clinicaltrials.gov/ct2/show/NCT03191942 .

Purpose To explore the associations between myopia defocus dosage (MDD), aberration coefficients (primary spherical aberration and coma), and axial elongation in children undergoing orthokeratology (ortho-k) with back optic zone diameters (BOZD) of 5 mm and 6 mm over 2 years. Methods Data from 80 participants from two ortho-k studies were analyzed: 22 and 58 children wore lenses with 5-mm and 6-mm BOZD, respectively. Four MDD metrics were calculated from corneal topography data over a 5-mm pupil for the 1-month and 24-month visits: the circumferential, flat, steep, and volumetric MDD. Corneal primary spherical aberration and comatic aberrations were also extracted from topography data over a 5-mm pupil. Linear mixed modelling was performed to explore the associations between the MDD, corneal aberrations, and axial elongation over 2 years, while controlling for confounding factors (e.g., baseline age and sex). Results Participants in the 5-mm BOZD group displayed less axial elongation than the 6-mm BOZD group over 2 years (0.15 ± 0.21 mm vs. 0.35 ± 0.21 mm, P  < 0.001). A greater volumetric MDD was observed in the 5-mm BOZD group compared with the 6-mm BOZD group at the 1- and 24-month visits (both P  < 0.001). No significant differences were observed between the two groups for the other MDD metrics or corneal aberration coefficients (all P  > 0.05). Less axial elongation was associated with a greater volumetric MDD at the 1- and 24-month visits (both β = –0.01, P  < 0.001 and P  = 0.001), but not with any other MDD metrics or corneal aberrations (all P  > 0.05). Conclusions The volumetric MDD over a 5-mm pupil after 1 month of ortho-k lens wear was associated with axial elongation after 24 months, and may be a useful predictor of future axial elongation in children undergoing ortho-k.

Background To analyze the fluid reservoir thickness over the whole cornea during scleral lens settling using wide-angle optical coherence tomography (OCT) images and customized computer software. Methods A total of 75 participants were recruited – 29 (myopes) with regular corneas and 46 with irregular corneas (35 with keratoconus, and 11 post-keratoplasty). All participants were fitted with customized scleral lenses and anterior segment OCT (Tomey Casia 2) images were taken 0, 30, 60, 120, and 240 min after lens application at the dispensing visit. Customized software was used to automatically segment the anterior cornea and the posterior surface of the scleral lens and determine the fluid reservoir thickness at 17 corneal regions across a 12 mm diameter. Results Fluid reservoir thickness decreased over time ( P  < 0.001) following an exponential decay, with no differences observed over time between the three groups ( P  = 0.97). The reduction in fluid reservoir thickness over four hours varied slightly between the central (149 ± 9 μm), mid-peripheral (139 ± 11 μm), and peripheral regions (131 ± 15 μm), P  = 0.046. The fluid reservoir was thinnest in the superior mid-periphery for both the myopia and post-keratoplasty groups, and centrally for the keratoconus group. The fluid reservoir was thickest inferiorly for all groups, with the greatest level of asymmetry observed along the vertical meridian. Conclusions Fluid reservoir thickness decreased most rapidly during the first two hours of lens wear and followed an exponential decay for both regular and irregular corneas across all corneal locations. Fluid reservoir asymmetry was greatest along the vertical meridian with a thicker reservoir observed in the inferior corneal regions.

Purpose To investigate the 2-year myopia control efficacy of Lenslet-ARray-Integrated (LARI) lenses with positive (PLARI) and negative (NLARI) power lenslets and the effect of switching lens designs. Methods A total of 218 children, who were randomly assigned to wear PLARI, NLARI, or single-vision (SV) lenses in Phase 1 continued in this randomized, double-masked extended trial for an additional year (Phase 2). Participants were randomly assigned to one of six groups: SV to PLARI, SV to NLARI, PLARI to PLARI (P-PLARI), PLARI to NLARI (P-NLARI), NLARI to PLARI (N-PLARI), and NLARI to NLARI (N-NLARI). In year 2, the change in spherical equivalent refraction (SER) and axial elongation (AE) from the SV group were extrapolated based on published data [the extrapolated single vision (ESV) group]. Linear models were used to determine differences in SER changes and AE among groups in 2 years and in Phase 2 only. Results After 2 years, the SER changes (− 0.87 ± 0.68 D, − 0.64 ± 0.86 D, − 0.68 ± 0.54 D, and − 0.75 ± 0.62 D, respectively) and AE (0.44 ± 0.33 mm, 0.33 ± 0.32 mm, 0.36 ± 0.23 mm, and 0.39 ± 0.25 mm, respectively) of P-PLARI, P-NLARI, N-PLARI, and N-NLARI were significantly smaller than those in the ESV group (SER: − 1.24 ± 0.77 D, all P  < 0.05; AE: 0.63 ± 0.33 mm, all P  < 0.001). In Phase 2, there was no significant difference in SER changes among the four LARI groups and ESV group ( P  = 0.58). In Phase 2, AE of the P-NLARI and N-PLARI groups was significantly smaller than the ESV group ( P  < 0.001 and P  = 0.001), and AE of the P-PLARI and N-NLARI groups were slightly smaller than that of ESV group ( P  = 0.054 and P  = 0.10), but there were no significant differences in AE among the four LARI groups (all P  > 0.05). Conclusions Wearing LARI lenses for 2 years effectively slowed myopia progression and AE. Switching to another LARI design after 1 year improved myopia control efficacy, in terms of AE, during the second year, but not SER progression. Trial registration Chinese Clinical Trial Registry, ChiCTR2200057210. Registered 03 March 2022, https://www.chictr.org.cn/bin/project/edit?pid=152900 .

It has been previously reported that the improper prescribing of antibiotic eye drops is common among orthokeratology (ortho-k) practitioners. Guidelines have since been developed and disseminated to improve their understanding and implementation of antibiotic prescriptions. This study aimed to investigate the influence of these guidelines on the knowledge, attitude, and prescribing habits of ortho-k practitioners by means of a questionnaire, which was administered nationwide via an official online account to eye care practitioners (ECPs) involved in ortho-k lens fitting, 548 of whom completed the survey. Differences in characteristics before and after the dissemination of the guidelines and between the groups were explored using χ2 tests. The relationship between prescribing habits and demographics was analyzed using stepwise logistic regression models. The implementation of the guidelines significantly improved the overall prescribing habits of ECPs (p < 0.001), especially for prophylactic antibiotic use before and after ortho-k lens wear (p < 0.001). Most ECPs who prescribed antibiotics properly displayed significantly better knowledge of correct antibiotic use, which in turn affected the compliance in their ortho-k patients (p < 0.001). The ECPs’ occupations (professionals other than ophthalmologists and optometrists, including nurses and opticians), clinical setting (distributor fitting centers), and age (younger than 25 years) were risk factors for the misuse of antibiotics. Although the implementation of the antibiotic guidelines significantly improved overall prescribing habits, some practitioners’ prescribing behavior still needs improvement. A limitation of this study was that all questions were mandatory, requiring ECPs to recall information, and therefore was subjected to selection and recall bias.

ObjectiveTo present the study design and the baseline data of a prospective cohort study investigating the safety, refractive correction and effectiveness of myopia control in subjects fitted with orthokeratology (ortho-k) lenses of different compression factors.Methods and analysisThis study is a 2-year longitudinal, double-masked, partially randomised study. Myopic children aged between 6 and 10 years are recruited and they may choose to participate in either the ortho-k or spectacle-wearing group. Subjects in the ortho-k group are randomly assigned to wear ortho-k lenses of either conventional compression factor (CCF, 0.75 D) or increased compression factor (ICF, 1.75 D). For the ortho-k subjects, the time and between-group effects within the first month of lens wear were analysed.ResultsSixty-nine ortho-k subjects (CCF: 34; ICF: 35) and 30 control subjects were recruited. There were no significant differences in baseline demographic data among the three groups of subjects (p>0.19). At the 1-month visit, the first fit success rates were 97% and 100% in the CCF and ICF ortho-k group, respectively. A higher percentage of ICF subjects could achieve full correction (CCF: 88.2%; ICF: 94.3%). The change in axial length was significantly higher in the ICF group (CCF, 0.003 mm; ICF, −0.031 mm) (p<0.05). No significant between-group differences in daytime vision or in the coverage and depth of corneal staining between the two ortho-k groups (p>0.05) were observed at any visit.ConclusionICF did not compromise the corneal integrity and the lens centration within the first month of lens wear. The preliminary performance of ortho-k lenses with ICF of 1.00D shows that it was safe to be used in the longer term for the investigation of myopia control.Trial registration number NCT02643342.

Background The retinal image quality derived from lower-order (LOA) and higher-order aberrations (HOA) for fixed 3-mm and photopic pupil diameters, in children undergoing combined 0.01% atropine and orthokeratology (AOK) versus those receiving orthokeratology alone (OK) over two years was evaluated. Methods The visual Strehl ratio based on the optical transfer function (VSOTF), derived from 2nd- to 4th-order terms (LOA and HOA combined), 2nd-order terms (LOA only), and 3rd- to 4th-order terms (HOA only) for fixed 3-mm and natural photopic pupil diameters, was compared between the two treatment groups. The individual Zernike coefficients for a fixed 3-mm pupil size of 2nd- to 4th-orders, root mean square (RMS) of LOA ( Z 2 0 , Z 2 - 2 , and Z 2 2 combined), HOA (3rd to 4th orders inclusive), and Coma ( Z 3 - 1 and Z 3 1 combined) were also compared between the two groups. Results Right eye data of 33 AOK and 35 OK participants were analysed. Under photopic conditions, significantly lower VSOTF based on HOA only was observed in the AOK group compared with that in the OK group at all post-treatment visits (all P  < 0.05); however, interactions between HOA and LOA resulted in comparable overall retinal image quality (i.e., VSOTF based on LOA and HOA combined) between the two groups at all visits (all P  > 0.05). For a fixed 3-mm pupil size, the VSOTF based on HOA only, LOA only, or HOA and LOA combined, were not different between the two groups (all P  > 0.05). AOK participants had slower axial elongation (mean ± SD, 0.17 ± 0.19 mm vs. 0.35 ± 0.20 mm, P  < 0.001), a larger photopic pupil size (4.05 ± 0.61 mm vs. 3.43 ± 0.41 mm, P  < 0.001) than OK participants, over two years. Conclusions HOA profile related to an enlarged pupil size may provide visual signal influencing eye growth in the AOK group.

The purpose of this study was to investigate the prevalence of antiseptic-resistance (QAC) genes in staphylococci colonizing periorbital tissues and accessories of orthokeratology (ortho-k) lens wearers over a 6-month period and determine the effect of their presence on minimum inhibitory (MIC) and bactericidal concentrations (MBC) of disinfectants and log reduction of multipurpose contact lens solutions (MPS). Staphylococci were isolated from periorbital tissues and accessories of patients before commencing ortho-k therapy and at two subsequent visits. Presence of QAC genes in 116 S. aureus and 67 CNS isolates was determined by PCR and association with period of ortho-k use determined. MICs and MBCs of staphylococci gene-positive were compared with gene-negative strains and the effectiveness of four MPS for rigid contact lenses investigated. S. aureus carriage rates in the conjunctiva decreased significantly from 41.2 % (baseline) to 11.8 % (3-months), and 13.3 % (6-months) ( p trend 0.03), while CNS increased from 58.8 %(baseline) to 94.1 % (3-months), and 93.3 % (6-months) ( p trend 0.02). Prevalence of qac A/B increased considerably over time ( S. aureus: 4.4 % to 15.4 %, CNS: 6.7 % to 25 %), but frequency of smr was relatively stable. Only five CNS isolates harboured qac H. MICs and MBCs of gene-positive isolates were significantly increased and three MPS did not achieve a 3-log reduction of many QAC-positive strains. Ortho-k lens wear contributed to changes of staphylococcal carriage rates in the conjunctival sac. Use of MPS containing quaternary ammonium compounds may select for the carriage of organisms harbouring QAC genes, as the low concentration of disinfecting agents is not adequate for killing gene-positive strains.