Anisomyopia and orthokeratology for myopia control - Axial elongation and relative peripheral refraction.

PURPOSE: To investigate axial elongation (AE) and changes in relative peripheral refraction (RPR) in anisomyopic children undergoing orthokeratology (ortho-k). METHODS: Bilateral anisomyopic children, 7-12 years of age, were treated with ortho-k. Axial length (AL) and RPR, from 30° nasal (N30°) to 30° temporal (T30°), were measured at baseline and every 6 months over the study period. AE, changes in RPR and changes in the interocular AL difference were determined over time. RESULTS: Twenty-six of the 33 subjects completed the 2-year study. The AE of the higher myopic (HM) eyes (at least 1.50 D more myopia than the other eye) (0.26 ± 0.29 mm) was significantly smaller than for the less myopic (LM) eyes (0.50 ± 0.27 mm; p = 0.003), leading to a reduction in the interocular difference in AL (p = 0.001). Baseline RPR measurements in the HM eyes were relatively more hyperopic at T30°, N20° and N30° (p ≤ 0.02) and greater myopic shifts were observed at T20° (p < 0.001), T30° (p < 0.001), N20° (p = 0.02) and N30° (p = 0.01) after lens wear. After 2 years of ortho-k lens wear, temporal-nasal asymmetry increased significantly, being more myopic at the temporal locations in both eyes (p < 0.001), while AE was associated with the change in RPR at N20° (ß = 0.134, p = 0.01). The interocular difference in AE was also positively associated with the interocular difference in RPR change at N30° (ß = 0.111, p = 0.02). CONCLUSIONS: Ortho-k slowed AE in bilateral anisomyopia, with slower growth in the HM eyes leading to a reduction in interocular AL differences. After ortho-k, RPR changed from hyperopia to myopia, with greater changes induced in the HM eyes, and slower AE was associated with a more myopic shift in RPR, especially in the nasal field of both eyes.

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

PURPOSE: To 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. METHODS: Forty-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. RESULTS: After 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. CONCLUSIONS: Smaller 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.

Manual and software-based measurements of treatment zone parameters and characteristics in children with slow and fast axial elongation in orthokeratology.

PURPOSE: To compare the treatment zone (TZ) measurements obtained using manual and software-based methods in orthokeratology (ortho-k) subjects and explore the TZ characteristics of children with slow and fast axial elongation after ortho-k. METHODS: Data from 69 subjects (aged 7 to <13 years old), who participated in three 24-month longitudinal orthokeratology studies, showing fast (>0.27 mm, n = 38) and slow (<0.09 mm, n = 31) axial elongation, were retrieved. The TZ after ortho-k was defined as the central flattened area enclosed by points with no refractive power change. TZ parameters, including decentration, size, width of the peripheral steepened zone (PSZ), central and peripheral refractive power changes and peripheral rate of power change, were determined manually and using python-based software. TZ parameters were compared between measurement methods and between groups. RESULTS: Almost all TZ parameters measured manually and with the aid of software were significantly different (p < 0.05). Differences in decentration, size and the PSZ width were not clinically significant, but differences (0.45 to 0.92 D) in refractive power change in the PSZ were significant, although intraclass coefficients (0.95 to 0.98) indicated excellent agreement between methods. Significantly greater TZ decentration, smaller TZ size and greater inferior rate of power change (relative to the TZ centre) were observed in slow progressors using both methods, suggesting a potential role of TZ in regulating myopia progression in ortho-k. CONCLUSION: TZ measurements using manual and software-based methods differed significantly and cannot be used interchangeably. The combination of TZ decentration, TZ size and peripheral rate of power change may affect myopia control effect in ortho-k.

Comparison between estimated and measured myopia progression in Hong Kong children without myopia control intervention.

PURPOSE: To compare myopia progression estimated by the Brien Holden Vision Institute (BHVI) Myopia Calculator with cycloplegic measures in Hong Kong children wearing single-vision distance spectacles over a 1- and 2-year period. METHODS: Baseline age, spherical equivalent refraction (SER) and ethnicity of control participants from previous longitudinal myopia studies were input into the BHVI Myopia Calculator to generate an estimate of the SER at 1 and 2 years. Differences between the measured and estimated SER (116 and 100 participants with 1- and 2-year subjective refraction data, respectively, and 111 and 95 participants with 1- and 2-year objective refraction, respectively) were analysed, and the measured SER compared with the 95% confidence interval (CI) of the estimated SER. RESULTS: In children aged 7-13 years, 36% progressed within the 95% CI of the Myopia Calculator's estimate, whereas 33% became less myopic than predicted (range 0.31 to 1.92 D less at 2 years) and 31% became more myopic than predicted (range 0.25 to 2.33 D more myopic at 2 years). The average difference between the estimated and measured subjective or objective SER at 1 and 2 years of follow-up was not clinically significant (<0.25 D). CONCLUSIONS: On average, the BHVI Myopia Calculator estimated SER was in close agreement with measured cycloplegic SER after 1 and 2 years of follow-up (mean differences < 0.25 D). However, the measured myopia progression only fell within the 95% CI of the estimated SER for 32%-38% of children, suggesting that the BHVI 'without management' progression data should be interpreted with caution. The inclusion of additional data, modified to include axial elongation, from longitudinal studies of longer duration with larger sample sizes and a range of racial backgrounds may improve the Calculator's ability to predict future myopia progression for individual children.

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

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.

Corneal thickness changes in myopic children during and after short-term orthokeratology lens wear.

PURPOSE: To evaluate thickness changes in the central and mid-peripheral cornea (CCT and mPCT), corneal epithelium (CET and mPET) and stroma (CST and mPST) of myopic children during and after short-term orthokeratology (ortho-k) lens wear, with conventional (CCF, 0.75 D) and increased compression factors (ICF, 1.75 D). METHODS: This was a self-controlled case series study. Subjects wore a CCF lens in one eye and an ICF lens in the other. Anterior segment optical coherence tomography images were captured weekly for 1 month during lens wear and for 2 weeks after discontinuing lens wear. CCT and CET (central 3-mm cornea) and mPCT and mPET (within a 4-6 mm diameter annulus) were measured. Stromal thickness (ST) was determined by subtracting epithelium thickness (ET) from corneal thickness (CT). The repeatability of the analytical software was also investigated on age-matched spectacle-wearing subjects (n = 98). RESULTS: Excluding three outliers (>3 S.D.s), the coefficient of repeatability and intraclass correlation coefficients of 98 spectacle-wearing subjects ranged from 2.63 to 4.64 µm and from 0.90 to 0.99, respectively. For the weekly-change study, CCT and CET in both eyes were significantly thinner after lens wear (p < 0.001) and CET thinning in the ICF eyes were significantly higher (p < 0.02). CCT changes were mainly contributed by CET. CST, mPCT, mPET and mPST changes were not significant (p > 0.20) in either eye. CT (all sublayers) rebounded to baseline values 2 weeks after discontinuing lens wear (0.99 > p > 0.12). CONCLUSIONS: Significant reductions in CT and ET, but not ST, were observed within 1 month of ortho-k lens wear. Wearing ICF lenses resulted in a higher reduction in CET. Corneal thickness changes were reversible after discontinuing lens wear.

Microbial Contamination of Periorbital Tissues and Accessories of Children.

PURPOSE: To investigate normal flora of children with and without orthokeratology (ortho-k) treatment, and the associations between carriage of Staphylococcus aureus and Gram-negative rods with contamination of contact lenses and lens cases in ortho-k subjects and with spectacles of control subjects. METHODS: Twenty-three ortho-k subjects (treatment >12 months) and 20 control myopic subjects aged 7-14 years were recruited. Samples were collected from four sites surrounding the left eye (lower conjunctiva, upper and lower eyelids, and eyelashes) for all subjects, spectacles for control subjects and contact lens accessories for ortho-k subjects. Samples were cultured, total numbers enumerated, and isolates identified using chromogenic agars. RESULTS: Ortho-k subjects had significantly less total isolates in the conjunctiva than controls (p = 0.009). Otherwise, carriage rates in normal flora levels of the peri-orbital tissues were not significantly different between the two groups (p > 0.19). The total isolates and carriage rates of normal flora on spectacles, contact lenses, and lens cases were similar to those identified on the skin tissues. Small numbers of bacteria were identified from the multipurpose solution of two ortho-k subjects. Although the association between the carriage of S. aureus with contamination of accessories was statistically significant only in control subjects (p = 0.03), ortho-k subjects not yielding S. aureus and Gram-negative rods from samples of their peri-orbital tissues tended to be less likely to have these organisms in their accessories. No Pseudomonas was isolated from any of the sites sampled and no Acinetobacter was isolated from any of the accessories. CONCLUSIONS: Ortho-k may lower the total number of bacteria in conjunctiva due to the use of solution and lenses, but the physiologic effect of this treatment on the types of normal flora in children was minimal and should not increase the risk of microbial keratitis in children with good compliance.

Parents' knowledge and perspective of optical methods for myopia control in children.

PURPOSE: To solicit parents' knowledge on myopia control strategies available; to investigate their attitudes toward the use of orthokeratology (ortho-k), daily wear soft lenses, and spectacles for myopia control, assuming all three optical strategies were equally effective for myopia control; and to collect their opinion on the age at which children can commence contact lens wear for vision correction. METHODS: Telephone interviews were conducted on parents who responded to the advertisement for two myopia control studies, one on ortho-k and one on soft lenses. RESULTS: Most of the 196 respondents (ortho-k group, 56%; soft lens group, 44%) were mothers, aged 36 to 45 years. Ortho-k was the most commonly known myopia control strategy (86%). Parents in the ortho-k group selected ortho-k (49%) and spectacles (45%) (p < 0.001) as their preferred myopia control strategy, whereas parents in the soft lens group had no preference (p = 0.57). Decision was affected by prior knowledge of myopia control strategy. Major considerations were convenience and safety among parents selecting contact lenses and spectacles, respectively, as their preferred options. Overall, because of the lack of confidence in safety in contact lens wear, most parents (75%) were of the opinion that contact lenses for vision correction were only for children older than 14 years (53%) and not indicated for children younger than 8 years. CONCLUSIONS: Parents in Hong Kong were open to the use of contact lenses for myopia control in young children and they appeared to regard myopia control contact lenses as "treatment" and not as visual aids. They were more conservative in the use of contact lenses for vision correction in children. Parents' decision in selecting a myopia control strategy, assuming all three strategies to be equally effective, was affected by an individual's concerns of safety and additional benefits as well as influenced by positive evidence on myopia control effects.

A new look at the myopia control efficacy of orthokeratology.

PURPOSE: To evaluate the efficacy of orthokeratology contact lens wear in slowing the axial elongation of the eye in myopic children. METHODS: Data from three prospective studies, which evaluated the use of orthokeratology for slowing myopia progression in children in comparison to a parallel control group of distance, single-vision spectacle lens wearers over a 2-year period, were pooled together for analysis. RESULTS: Collectively, data from 125 orthokeratology and 118 control subjects were analyzed in this study. Of these, 101 (81 %) and 88 (75 %) orthokeratology and control subjects completed the 2-year follow-up period, respectively. Statistically significant differences in the change in axial length from baseline were found over time, between groups and for the time*group interaction (all p < 0.001), indicating that the rate of increase in axial length over time was significantly lower in the orthokeratology versus the control group. The lower axial elongation of the orthokeratology versus the control group was statistically significant at all time points (all p < 0.001), with significant differences being also present between each of the different pairs of time points (all p < 0.001). The interactions of group with age, gender, mean spherical refractive error and ethnicity at baseline were not significant (p > 0.05). The change in axial length at the 2-year visit in comparison to baseline for the orthokeratology and control groups were 0.41 ± 0.25 and 0.65 ± 0.30 mm, respectively, thus providing a treatment effect following 2-years of lens wear of 0.24 mm (95 % confidence intervals: 0.15 to 0.34 mm). About 40 % and 25 % of the orthokeratology subjects experienced remarkably low and high levels of myopia progression, respectively (2-years axial elongation: ≤0.30 mm and >0.59 mm, respectively). CONCLUSIONS: Orthokeratology lens wear slows the axial elongation of the eye in comparison to spectacle lens wear in myopic children. The use of these lenses for slowing myopia progression appears to be very effective and not effective at all in 40% and 25% of orthokeratology lens wearers, respectively.

The safety of orthokeratology contact lens wear in slowing the axial elongation of the eye in children.

PURPOSE: To evaluate the safety of orthokeratology contact lens wear in slowing the axial elongation of the eye in myopic children. METHODS: Safety data from three prospective studies, which evaluated the use of orthokeratology for slowing myopia progression in children in comparison to a parallel control group of single-vision spectacle lens wearers over a 2-year period, were pooled together for analysis. The primary and secondary safety endpoints are the comparisons of adverse events and slit-lamp findings grades ≥ 2 between orthokeratology and control groups, respectively. RESULTS: Collectively, data from 125 orthokeratology and 118 control subjects were analyzed in this study. Of these, 101 (81 %) and 88 (75 %) orthokeratology and control subjects completed the 2-year follow-up period, respectively. Nineteen orthokeratology subjects experienced 28 adverse events, of which 6 were significant, whereas just one adverse event was found in the control group; this difference was statistically significant (p < 0.001). Most adverse events found in the orthokeratology group were corneal in nature, primarily corneal abrasion/staining, accounting for around 40 % of all adverse events. Of the 28 adverse events, only 18 (3 significant) are likely to be contact lens-related, leading to incidence rates of total and device-related adverse events per 100 patient years of lens wear (95 % confidence intervals) of 13.1 (9.2-18.2) and 8.4 (5.4-10.7), respectively. No significant differences were found between groups in the total number of silt-lamps findings with grades ≥ 2 (p > 0.05). CONCLUSION: Around 13% of eyes wearing overnight orthokeratology contact lenses are likely to experience an adverse event over one year of lens wear, with this figure being lower when considering device-related adverse events alone. No serious adverse events were found, with most being non-significant. These results inform eye care practitioners on the safety of orthokeratology lenses when prescribed for slowing myopia progression to myopic children.

Ocular signs and symptoms of orthokeratology patients associated with povidone iodine-based disinfecting solution.

PURPOSE: To determine the frequency and severity of ocular symptoms and signs in new orthokeratology (ortho-k) subjects using a povidone iodine (PI) disinfecting system compared to those present before lens wear, and whether these were associated with cleaning regimes. METHODS: This study recruited 80 subjects from two myopia control studies, who used a PI disinfecting solution for routine use. Ocular symptoms and signs at baseline, one- and six-month after lens wear were reported via questionnaires and ocular examination, respectively. To determine if rates of occurrence were attributable to differences in cleaning regime, subjects were randomly assigned into four groups with respect to routine care procedures, which involved various combinations of rubbing and use of a daily and/or enzymatic cleaner. RESULTS: Sixty-eight subjects completed all aspects of the study. As there were no significant differences in incidence of signs and symptoms between the four groups before and after lens wear (Friedman tests, p > 0.07), data were combined for further analysis. Prior to lens wear, itchiness (69 %) and dryness (53 %) were the most commonly reported symptoms. The frequency and severity of all symptoms remained similar after lens wear (p > 0.10). Presence of follicles in the lower tarsal conjunctiva (22 %) and conjunctival injection (15 %) was frequently observed, but reduced significantly after lens wear (p < 0.01). Mild corneal staining, noted in 13 % of subjects at baseline, did not change significantly over time (p = 0.17). Ocular signs were not necessarily reflected in symptoms and vice versa. CONCLUSION: Use of a PI-based solution did not increase the frequency or severity of ocular signs and symptoms observed before lens wear. Absence of a difference in occurrence of ocular discomfort with respect to cleaning regimes indicated that the use of the PI-based solution may adequately clean the lenses over a 6-month period.

Optical changes and association with axial elongation in children wearing orthokeratology lenses of different back optic zone diameter.

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) ([Formula: see text], 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 ([Formula: see text] and secondary ([Formula: see text] 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 .

Toric orthokeratology for highly astigmatic children.

PURPOSE: To determine the efficacy of toric orthokeratology (ortho-k) in correcting myopia and astigmatism in myopic children with moderate to high astigmatism. METHODS: Asymptomatic subjects aged 6 to 12 years with myopia of 0.50 to 5.00 D and astigmatism of 1.25 to 3.50 D of axes 180 ± 20° were fitted with Menicon Z Night Toric Lens (NKL Contactlenzen B.V., Emmen, The Netherlands). Data collection was performed at baseline and 1 night, 1 week, and 1 month after the commencement of lens wear. The results from the right eye or the eye with higher astigmatism were reported. RESULTS: The first lens fit success rate was 95%. Two subjects had to be refitted due to lens decentration and inadequate central clearance after one overnight lens wear and were successfully fitted with a second pair of lenses. Toric ortho-k significantly reduced the manifest myopia from 2.53 ± 1.31 D to 0.41 ± 0.43 D and astigmatism from 1.91 ± 0.64 D to 0.40 ± 0.39 D (paired t-tests, p < 0.02) after 1 month of lens wear. The unaided visual acuity (logMAR) was 0.11 ± 0.13 after 1 month of lens wear. No significant lens binding, corneal staining, or other adverse events were observed during this period of lens wear. CONCLUSIONS: This toric lens design lens, with a first lens fit success rate of 95%, was effective in correcting low-moderate myopic children who had moderate-high astigmatism. It has the potential to be used in myopic control studies for myopic children who have high astigmatism.

Do fenestrations affect the performance of orthokeratology lenses?

PURPOSE: To investigate the effect of lens fenestrations on the performance of orthokeratology lenses. METHODS: Twenty-two subjects (aged 11 to 31 years) were fitted with identical reverse geometry orthokeratology lenses in the two eyes. One eye was randomly designated to wear a lens with three 0.20 mm fenestrations at 120° intervals placed at the junction of the reverse and alignment curves. The lens for the other eye was not fenestrated. Subjects were reviewed at 1 week, 1 month, 3 months, 6 months, and 1 year after fitting. Data were collected on refraction, visual performance, incidences and severity of corneal staining, lens binding, and corneal pigmented arc. RESULTS: Fifteen subjects achieved full correction in OU. There were no statistically significant differences in refractive and corneal changes, visual performance, incidences and severity of corneal staining and corneal pigmented arc formation between the two eyes. The incidence of lens binding was consistently higher in eyes wearing non-fenestrated lenses but was not statistically significant. Severity of lens binding, however, was statistically significant at the 1-, 3-, 6- and 12-month visits, with the non-fenestrated lenses causing more severe binding. CONCLUSIONS: The addition of fenestrations to orthokeratology lenses has no effect on the efficacy of the treatment or outcomes in low to moderate myopic subjects. However, the severity of lens binding is reduced. Fenestrating reverse geometry lenses may be of assistance in cases where lens binding is a problem.

Nidek ConfoScan 4 (z-ring) measurements over soft contact lenses.

OBJECTIVE: The aim was to compare the thickness of each corneal sublayer and the visualization of superficial epithelial cells measured with the ConfoScan 4 (CS4) z-ring with and without the use of a soft contact lens and to evaluate the recovery rate of corneal staining after measurement with the CS4 (z-ring) with and without the application of artificial tears (ATs). METHODS: Twenty-eight subjects aged 18 to 35 years were recruited to have measurements with the CS4 (z-ring) on 2 different days. The measurements were performed over soft contact lenses (hydrogel lens or silicone hydrogel lens) on the first day and on the naked cornea on the second day. The recovery rates of the corneal staining induced by the measurements at the second visit were monitored for 5 hrs after measurements, one eye with the application of ATs and one eye without. RESULTS: No significant differences were found in the thicknesses of the central cornea and the sublayers measured with or without soft contact lenses. The intensity of epithelial cell images was improved with measurement made over hydrogel lenses, and on average, grade 3 (coverage) staining was observed in the corneas immediately after measurements without contact lenses. The recovery rate of the corneal staining did not improve with the application of ATs. CONCLUSIONS: Thickness measurements with the CS4 (z-ring) were not affected if made over soft contact lenses. The use of a soft lens to buffer the cornea during measurements was effective in eliminating corneal dehydration, preventing staining induced by the z-ring without affecting the corneal thickness measurement. It also enhanced epithelial image brightness, which may improve the accuracy in pachymetry.

Repeatability and reproducibility of manual choroidal thickness measurement using Lenstar images in children before and after orthokeratology treatment.

PURPOSE: To investigate the repeatability and reproducibility of choroidal thickness measurements using Lenstar images in young myopic children before and after one-month orthokeratology (ortho-k) treatment. METHOD: Ocular biometry of 39 subjects were performed using the Lenstar 900. The first five measurements with maximum differences of 0.02 mm in axial length in the right eyes were saved and used for measurement of choroidal thickness. Subfoveal choroidal thickness were manually measured by identifying the signals from the retinal pigmented epithelium layer and chorioscleral interface. Repeatability was determined by comparing measurements of the same images made by the same observer on two separate occasions (four weeks apart), while reproducibility was calculated by comparing measurements of the same images made by two independent observers. Data was analysed using intra-class correlation coefficients (ICC) and non-parametric Bland and Altman plots. RESULTS: The choroidal peaks could not be identified in all five measurements in all subjects. On average, only 71% subjects had at least four definable images. Compared with the use of fewer than four images, reliability using an average of four definable images improved statistically, but remained clinically unacceptable (>10 µm), although pre- and post-ortho-k ICC values were good to excellent for repeatability (0.867 and 0.975, respectively) and excellent and good for reproducibility (0.959 and 0.868, respectively). Non-parametric pre- and post-ortho-k limits of agreement (2.5% and 97.5% percentiles) obtained were -45.8 to 79.3 µm and -30.3 to 9.5 µm, respectively for repeatability, and -29.0 to 33.5 µm and -21.8 to 70.0 µm, respectively for reproducibility. CONCLUSION: Choroidal thickness measurements using the Lenstar did not show good reliability, despite the high ICC values, non-parametric Bland and Altman plots demonstrated a wide variability of measurement errors. Any changes in subfoveal choroidal thickness, measured by Lenstar, of <80 µm may not represent real changes.

Corneal sublayer thickness measurements with the Nidek ConfoScan 4 (z Ring).

PURPOSE: To determine the repeatability of corneal sublayer thickness measurements using the Nidek ConfoScan 4 (CS4) with the z ring on a group of young adult subjects. METHODS: Thirty subjects aged 18 to 30 years were invited to have thickness measurements with the CS4 (z ring) on two different days, at similar time of the day to avoid diurnal variation. RESULTS: Only 22 subjects had valid measurements for analysis. The mean ± SD of central corneal thickness (CCT) was 534 ± 26 µm, epithelial thickness was 42 ± 8 µm, Bowman's layer thickness was 19 ± 7 µm, and stromal thickness (ST) was 472 ± 25 µm. There was no significant difference in the between-visit thickness measurements of each layer with the CS4 (z ring) (paired t-tests, p > 0.05). The limits of agreement of between-visit measurements were -41 (8%) to 37 µm (7%) for CCT, -21 (50%) to 19 µm (45%) for epithelial thickness, -13 (68%) to 17 µm (89%) for Bowman layer thickness, and -46 (10%) to 37 µm (8%) for ST. CONCLUSIONS: Measurements of CCT and ST with the CS4 (z ring) showed reasonably good repeatability (7 to 10%). However, the repeatability of measurements of the thinner corneal layers, such as epithelium and Bowman's layer, was poor.

Effect of povidone iodine contact lens disinfecting solution on orthokeratology lens and lens case contamination and organisms in the microbiome of the conjunctiva.

PURPOSE: To compare lens cleaning routines using a povidone iodine-based rigid lens disinfecting solution and its effect on conjunctival colonisation, and lens and lens case contamination. METHODS: Participants, aged 6-10 years, receiving orthokeratology treatment were randomised to four lens cleaning routines: with and without the use of daily and/or weekly cleaners, which were performed by their parents. Conjunctival colonisation was compared before lens wear and at 1-, 3-, and 6-month after commencement of lens wear. Contamination of lenses and lens cases was investigated at these times. Organisms were identified using MALDI-TOF mass spectrometry. RESULTS: Of the 76 participants who completed the study, conjunctival colonization was present in 24 (32 %) at baseline. Of the remaining 52 participants, 34 consistently yielded no growth. Participants positive at baseline were statistically more likely to be colonized after commencement of lens wear (p = 0.020). Overall, colonization rate was reduced to 15 % (11/72) after 6-month lens wear, which reached significance for initially colonized participants (p < 0.001). Few cultures yielded potential ocular pathogens, with notably no Pseudomonas aeruginosa. Contamination rates of both lenses and lens cases were also low, with few isolations of ocular pathogens. No significant differences were observed between cleaning regimes for conjunctival colonization or contamination of lenses or cases. CONCLUSIONS: Disinfection for rigid and ortho-k lens wearers may be effectively achieved with the use of povidone iodine-based solution, apparently regardless of cleaning routine adopted in the current study. The absence of pathogens in the conjunctiva, lenses, and lens cases in the great majority of samples indicates that it can improve the safety of overnight lens wear.

Investigation of effects of orthokeratology and povidone iodine disinfecting solution on the conjunctival microbiome using MALDI-TOF mass spectrometry.

Purpose: To determine organisms present in the conjunctiva of children before and after orthokeratology lens wear, using MALDI-TOF mass spectrometry. Methods: Conjunctival samples were collected from children aged 8-12 years (inclusive) at baseline and on three occasions over the first six months of orthokeratology treatment. All lenses were disinfected using the povidone iodine-based solution every day after use. Specimens were cultured and all isolated colonies were identified using MALDI-TOF mass spectrometry. Numbers of organisms and diversity were compared over the study period and the presence of any ocular pathogens noted and participants informed, where appropriate, to enhance their compliance with lens care routine. Results: Organisms isolated from 76 children were generally similar to other studies employing culture methods. However, MALDI-TOF results yielded a wider range of species of micrococci and corynebacteria, as well as a few less frequently reported organisms. Only one culture yielded fungi. Ocular pathogens were only isolated from 9 subjects (4 before lens wear and 5 after lens wear), each on one occasion only. Diversity and numbers of organisms fell slowly over the period of the study, but the changes were not significant. Conclusions: Lens wear did not affect the overall content of the ocular microbiome, but the diversity was somewhat reduced. The incidence of ocular pathogens was low, suggesting that risk of ocular infection was not substantially increased by orthokeratology treatment using a povidone-iodine disinfecting solution.