The Influence of Overnight Orthokeratology on Ocular Surface and Meibomian Glands in Children and Adolescents

Comparison of trial lens and computer-aided fitting in orthokeratology: A multi-center, randomized, examiner-masked, controlled study

PURPOSE

To compare the efficacy and safety between traditional lens fitting and computer-aided fitting methods for orthokeratology (OrthoK) in the Chinese population.

METHODS

A multi-center, examiner-masked, randomized controlled study was conducted with a one-year follow-up period, enrolling 280 participants with spherical equivalent (SE) ranging from -0.5D to -4.0D. Participants were assigned to either the computer-aided orthokeratology fitting group (trial group) or the traditional lens fitting group (control group) using stratified randomization based on age (8 to 13 years, 13 to 18 years, and ≥ 18 years) to ensure a minimum of 30 cases in each sub-age group. Ocular examinations included visual acuity, objective and subjective refraction, corneal endothelial cell density, corneal topography, intraocular pressure, axial length, and ocular health assessment. Successful lens-correction was defined as the residual refraction with the OK lens, which should not exceed ± 0.5D, and/or an uncorrected visual acuity of no worse than 0.1 logMAR. Statistical analysis involves t-tests, analysis of variance, and Chi-squared tests.

RESULTS

215 subjects were included in the statistical analysis (109 in the trial group and 106 in the control group). In both groups, compared to baseline data, the uncorrected visual acuity (UCVA) improved significantly, with SE reduced and central corneal curvature flattened greatly after wearing OrthoK lens (P < 0.05 for all). Compared to the control group, the trial group exhibited a higher successful rate in correcting UCVA (93.6 % vs. 84.0 %, P = 0.03) and slightly better correction in refraction (77.1 % vs. 66.0 %, P = 0.07) at 1-month follow-up. However, no significant differences were observed in the axial length elongation, corneal changes, or the incidence of adverse events between the two groups.

CONCLUSION

These findings indicate the higher efficiency and slightly better performance in correcting myopia and improving UCVA of computer-aided lens fitting approach compared to the traditional one, but similar outcomes in controlling axial elongation.

Contact lens wear and follow-up and its association with signs and symptoms of meibomian gland dysfunction

INTRODUCTION

This study investigated the equivocal association between contact lens (CL) wear and meibomian gland dysfunction (MGD) by comparing the morphological, functional and subjective outcomes of CL wearers versus control, non-CL wearers. CL wearers were examined as two cohorts based on the annual attendance of follow-up visits (FLU-attended these visits, whereas non-FLU did not).

METHODS

Habitual logMAR visual acuity, invasive and non-invasive tear break-up time, Schirmer test, Efron grading scales, meibum quality score (MQS), meibum expressibility score (MES), meibomian gland (MG) loss, lid margin abnormalities and subjective dry eye (DE) symptoms were assessed.

RESULTS

Of the 128 participants, 31 were in the FLU cohort, 43 were in the non-FLU cohort and 54 were controls (mean ages: 22.2 ± 3.1, 23.0 ± 4.6 and 22.3 ± 3.5, respectively). Non-FLU CL wearers had more symptoms than controls (3.7 ± 2.4 vs. 2.3 ± 2.1, p < 0.01). Morphologically, FLU (16.9 ± 8.8%, p = 0.02) and non-FLU (18.6 ± 11.3%, p = 0.001) had more MG loss than controls (11.2 ± 6.8%). Functionally, FLU (0.6 ± 0.7, p = 0.01) and non-FLU (0.8 ± 0.9, p = 0.001) had worse MES than controls (0.2 ± 0.5). FLU and non-FLU were both associated with corneal staining (odds ratio [OR] = 3.42, 95% CI: 1.16-10.11, p = 0.03 and OR = 5.23, 95% CI: 1.89-14.48, p = 0.001, respectively) and MG loss (OR = 10.47, 95% CI: 1.14-96.29, p = 0.04 and OR = 16.63, 95% CI: 1.96-140.86, p = 0.01, respectively). Non-FLU CL wear was also associated with abnormal MQS (OR = 12.87, 95% CI: 1.12-148.41, p = 0.04), conjunctival staining (OR = 12.18, 95% CI: 3.66-40.51, p < 0.001) and lid margin telangiectasia (OR = 3.78, 95% CI: 1.55-9.21, p = 0.003). MGD was three times more prevalent in CL wearers (12%) than in controls (4%).

CONCLUSIONS

Both CL-wearing cohorts demonstrated significantly more MG abnormalities than controls though the difference was not clinically significant. Non-FLU CL wearers had more DE symptoms. Non-FLU CL wear is an independent predictor for more abnormalities than FLU CL wear, emphasising the importance of follow-ups.

Medmont Meridia™: Much More Than a Corneal Topographer

In recent years, advanced diagnostic instruments have become widely available in optometric practices, offering various functions that optimize clinical information gathering. This article focuses on the Medmont Meridia™, a state-of-the-art multipurpose diagnostic device with corneal topography and cutting-edge features. Corneal topography is pivotal in the early diagnosis of corneal disorders, determining baseline ocular surface assessment, helping in contact lens fitting, and monitoring ocular health over time. The Medmont Meridia boasts Placido-disc-based imaging with extensive corneal coverage. Furthermore, the Meridia accurately measures the horizontal visible iris diameter, pupil diameter, and palpebral fissure width, which assists in making contact lens parameter decisions. Additionally, it offers sagittal height data for scleral lens design and first lens selection, streamlining the fitting process. Beyond its topography capabilities, the Meridia excels as a comprehensive dry eye assessment tool. With features like tear meniscus height, tear film surface quality, and meibography capabilities, it aids in diagnosing dry eye and monitoring its progression. The device also provides customizable dry eye reports with integrated grading scales and questionnaires, making dry eye management, patient education, and compliance more accessible. In conclusion, the Medmont Meridia consolidates a multitude of examination tools in a single instrument, enhancing practice efficiency and elevating patient care and communication. Its versatility and accuracy make it an invaluable asset in optometric practices worldwide.

Changes of corneal biomechanics in children using orthokeratology and their roles in predicting axial length progression-A prospective 2-year study

PURPOSE

To determine how orthokeratology (ortho-k) affects corneal biomechanical properties in myopia control and whether corneal biomechanical parameters can predict clinical efficacy of ortho-k.

METHODS

A total of 125 children 7-15 years of age using ortho-k lenses were followed in this clinical practice and data of their right eyes were analysed. Corneal biomechanical parameters and most ocular biometry were measured at baseline, 1 week, and at 1, 3, 6, 12, 18 and 24 months. Axial length (AL) was collected every 6 months after baseline measurements.

RESULTS

During the 2-year follow up, nine corneal biomechanical parameters, including deformation amplitude maximum (DA), varied between baseline and 1 week (p < 0.05) and stabilized during the rest of wearing period (p > 0.05). The mean AL increased from 25.02 ± 0.84 mm to 25.38 ± 0.81 mm and baseline DA strongly correlated with AL progression (Pearson r = 0.37). In the multiple regression models, baseline age, AL and DA were the independent factors for AL progression (R2 : 0.7849, 0.2180 in low and moderate myopes). The area under the receiver operating characteristic curves using the three variables for predicting excessive AL progression (>0.35 mm during 2 years) in low and moderate myopes was 0.902 and 0.698.

CONCLUSIONS

Corneal biomechanics firstly fluctuated before becoming stable with long-term ortho-k use. Corneal biomechanics was associated with AL progression in children wearing ortho-k lenses. DA combined with age and AL at baseline could predict AL progression in low myopes using ortho-k.

The Effects of Spectacles or Orthokeratology on the Tear Film in Children and Adolescents

INTRODUCTION

Myopia prevalence among adolescents is increasing annually. While orthokeratology (OK) is effective for controlling myopia progression, it may also be detrimental. We investigated tear film parameters [including tear mucin 5AC (MUC5AC) concentration] in children and adolescents with myopia treated with spectacles or OK compared with those with emmetropia.

METHODS

This prospective case-control study enrolled children (aged 8-12 years; 29 and 39 with myopia treated with OK and spectacles, respectively, and 25 with emmetropia) and adolescents (aged 13-18 years; 38 and 30 with myopia treated with OK and spectacles, respectively, and 18 with emmetropia). We recorded the ocular surface disease index (OSDI), visual analog scale (VAS) score, tear meniscus height (TMH), noninvasive tear breakup time (NIBUT), meibomian gland score (meiboscore), ocular redness score, and tear MUC5AC concentration in the emmetropia, spectacle (after 12 months of spectacle wearing), and OK (baseline, and after 1-, 3-, 6-, and 12-month use) groups. We observed changes from baseline to 12 months in the OK group and compared parameters among the spectacle, 12-month OK, and emmetropia groups.

RESULTS

The 12-month OK group differed significantly from the spectacle and emmetropia groups in most indicators among children and adolescents (P < 0.05). Differences were not noticeable between the spectacle and emmetropia groups (only PVAS < 0.05 among the children). In the OK group, the 12-month NIBUT was significantly decreased (P < 0.05) in both age groups; the upper meiboscore was increased at 6 and 12 months (both P < 0.05) among children; ocular redness scores were higher at 12 months than at baseline (P = 0.007), 1 month (P < 0.001), and 3 months (P = 0.007) among children; and the MUC5AC concentration was decreased at 6 and 12 months among adolescents, but only at 12 months among children (all P < 0.05).

CONCLUSIONS

Long-term OK can negatively influence the tear film in children and adolescents. Moreover, changes are masked by spectacle wearing.

TRIAL REGISTRATION

This trial is registered with "ChiCTR2100049384."

Short-term application of diquafosol ophthalmic solution benefits children with dry eye wearing orthokeratology lens

Purpose

This aim of this study was to evaluate the effect of 3% Diquafosol Ophthalmic Solution (DQS) on children with dry eye from wearing overnight orthokeratology (OrthoK) lenses.

Methods

Myopic children aged 8-18 years with dry eye syndrome were enrolled in this prospective observational study, and they were grouped according to their OrthoK treatment history for at least 1 year. All participants received DQS 4 times per day for 1 month. The following indicators were measured at baseline 1 month after treatment: the Dry Eye Questionnaire-5 (DEQ-5), non-invasive tear meniscus height (TMH), non-invasive tear film break-up time (first and average, NIBUT-F and NIBUT-A), meibomian gland score (MG score), conjunctival hyperemia redness score (R-scan), and blink pattern analysis.

Results

A total of 104 participants (189 eyes) including 40 OrthoK wearers (72 eyes) and 64 Orthok candidates (117 eyes) completed the study. Of all, after DQS treatment for 1 month, DEQ-5 scores reduced from 5.54 ± 3.25 to 3.85 ± 2.98 (t = -3.36, p = 0.00). TMH increased from 0.20 ± 0.05 mm to 0.21 ± 0.05 mm (t = 2.59, p = 0.01), NIBUT-F and NIBUT-A were prolonged from 6.67 ± 4.71 s to 10.32 ± 6.19 s and from 8.86 ± 5.25 s to 13.30 ± 6.03 s (all p = 0.00), respectively. R-scan decreased from 0.69 ± 0.28 to 0.50 ± 0.25 (t = -9.01, p = 0.00). Upper MG scores decreased from 1.04 ± 0.32 to 0.97 ± 0.36 (t = -2.14, p = 0.03). Lower MG scores, partial blink rate, partial blinks, and total blinks did not change significantly. Both break-up time (BUT) and R-scan improved significantly after DQS treatment for 1 month (all p = 0.00) in OrthoK candidates and OrthoK wearers. Among the OrthoK wearers, TMH and dry eye symptoms increased significantly (all p = 0.00) but did not increase in OrthoK candidates (p > 0.05). There were no adverse events related to DQS.

Conclusion

Diquafosol Ophthalmic Solution was effective for children wearing overnight orthokeratology in relieving dry eye symptoms and improving ocular surface parameters, which may help improve children's OrthoK wearing tolerance and compliance.

Effects of orthokeratology lenses on tear film and tarsal glands and control of unilateral myopia in children

Introduction: To investigate the effects of an orthokeratology lens on the tear film and tarsal glands and myopia control in children with unilateral myopia using an intelligent analysis model. Methods: We retrospectively reviewed the medical records from November 2020 to November 2022 of 68 pediatric patients with unilateral myopia in Fujian Provincial Hospital who had been wearing an orthokeratology lens for more than 1 year. The 68 myopic eyes were included in the treatment group, while the 68 healthy, untreated contralateral eyes were included in the control group. Tear film break-up times (TBUTs) were compared between the two groups at various intervals, and an intelligent analysis model was used to compare the deformation coefficients of 10 meibomian glands in the central area and the different positions of the glands in the two groups after 12 months of treatment. Changes in axial length and equivalent spherical power were also compared between the groups before and after 12 months of treatment. Results: In the treatment group, TBUTs differed significantly between 1 and 12 months after treatment, although no significant differences from baseline were observed at 3 or 6 months. No significant differences in TBUTs were observed at any time point in the control group. After 12 months of treatment, significant between-group differences were observed for glands 2, 3, 4, 5, 6, 7, 8, and 10 (numbered from the temporal to nasal regions). The treatment group also exhibited significant differences in deformation coefficients at different detection positions in the central region, with glands 5 and 6 exhibiting the highest deformation coefficients. Increases in axial length and equivalent spherical power were significantly greater in the control group than in the treatment group after 12 months of treatment. Discussion: Wearing orthokeratology lenses at night can effectively control myopia progression in children with unilateral myopia. However, long-term use of these lenses may lead to meibomian gland deformation and impact tear film function, and the extent of deformation may vary at different positions in the central region.

The influence of overnight orthokeratology and soft contact lens on the meibomian gland evaluated using an artificial intelligence analytic system

PURPOSE

To test the changes of meibomian gland (MG) morphology using an artificial intelligence (AI) analytic system in asymptomatic children wearing overnight orthokeratology (OOK) and soft contact lens (SCL).

METHODS

A retrospective study was conducted including 89 participants treated with OOK and 70 participants with SCL. Tear meniscus height (TMH), noninvasive tear breakup time (NIBUT), and meibography were obtained using Keratograph 5 M. MG tortuosity, height, width, density, and vagueness value were measured using an artificial intelligence (AI) analytic system.

RESULTS

In an average of 20.80 ± 10.83 months follow-up, MG width of the upper eyelid significantly increased and MG vagueness value significantly decreased after OOK and SCL treatment (all P < 0.05). MG tortuosity of the upper eyelid significantly increased after OOK treatment (P < 0.05). TMH and NIBUT did not differ significantly pre- and post- OOK and SCL treatment (all P > 0.05). The results from the GEE model demonstrated that OOK treatment positively affected MG tortuosity of both upper and lower eyelids (P < 0.001; P = 0.041, respectively) and MG width of the upper eyelid (P = 0.038), while it negatively affected MG density of the upper eyelid (P = 0.036) and MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). SCL treatment positively affected MG width of both upper and lower eyelids (P < 0.001; P = 0.049, respectively) as well as MG height of the lower eyelid (P = 0.009) and tortuosity of the upper eyelid, (P = 0.034) while it negatively affected MG vagueness value of both upper and lower eyelids (P < 0.001; P < 0.001, respectively). However, no significant relationship was found between the treatment duration and TMH, NIBUT, MG morphological parameters in OOK group. SCL treatment duration negatively affected MG height of the lower eyelid (P = 0.002).

CONCLUSIONS

OOK and SCL treatment in asymptomatic children can influence MG morphology. The AI analytic system may be an effective method to facilitate the quantitative detection of MG morphological changes.

Influence of overnight orthokeratology on tear film and meibomian glands in myopic children: a prospective study

BACKGROUND

Orthokeratology lenses, which are worn overnight, are recommended for reducing myopia progression. They lie on the cornea and can influence the ocular surface by temporarily reshaping the corneal surface through a reverse geometry design. This study investigated the effect of overnight orthokeratology lenses on tear film stability and meibomian gland status in children aged 8-15 years.

METHODS

This prospective, self-controlled study included 33 children with monocular myopia who were prescribed orthokeratology lenses for at least one year. The experimental group (ortho-k group) comprised 33 myopic eyes. The control group comprised the emmetropic eyes of the same participants. Tear film stability and meibomian gland status were measured using a Keratograph 5M (Oculus, Wetzlar, Germany). Paired t-tests and Wilcoxon signed-rank tests were used to compare the data between the two groups.

RESULTS

At the one-year visit, the non-invasive first tear film break-up time (NIBUTf) values were 6.15 ± 2.56 s and 6.18 ± 2.61 s in the experimental and control groups, respectively. The lower tear meniscus height was 18.74 ± 0.05 μm and 18.65 ± 0.04 μm in these groups, respectively. No significant difference was observed in loss of meibomian glands or non-invasive average tear film break-up time between the experimental and control groups using Wilcoxon signed-rank tests.

CONCLUSIONS

The stability of the tear film and meibomian gland status were not significantly affected by wearing orthokeratology lenses overnight, indicating that continuous use of orthokeratology lenses for 12 months has a minimal effect on the ocular surface. This finding can help guide the clinical management of tear film quality with respect to the use of orthokeratology contact lenses.

Effect of overnight orthokeratology lenses on tear film stability in children

PURPOSE

To assess the tear film surface quality after orthokeratology using an automated Medmont E300 corneal topographer.

METHODS

Children who wore orthokeratology lenses for more than one year were selected in this retrospective study. Tear film disruption (TFD) and central tear film disruption (cTFD) were measured with Medmont E300 corneal topographer at initial and each follow-up visit after fitting with orthokeratology lenses, providing a nominal value from 0 (perfect) to 1 (poor). Tear film surface quality before and after ortho-k treatment was compared.

RESULTS

145 children using orthokeratology lenses were observed. TFD and cTFD significantly increased at 1-day follow up (TFD, t = -17.3, P < 0.001; cTFD, t = -10.4, P < 0.001). This change remained consistent through to 12-months visit (TFD, F = 51.1, P < 0.001; cTFD, F = 28.0, P < 0.001). A sub-group of n = 11 children were discontinued for 1-month before being refit with OrthoK lenses of a different design. Similarly, there was a significant increase in TFD compared to pre-orthoK scans (0.172 ± 0.161), but this returned to baseline levels after ceasing lens wear (0.084 ± 0.059). A sub-group of monocular OrthoK wearers (n = 23) found that TFD and cTFD values increased in eyes with monocular lens-wearing but remained stable in the lateral eyes.

CONCLUSIONS

Objective measurements of tear-film quality are reduced in children after fitting with orthokeratology lenses, but return to baseline after 1-month of lens cessation. It is of importance to ensure tear film surface quality is continuously monitored throughout use of orthoK lenses.

Long-term changes in the ocular surface during orthokeratology lens wear and their correlations with ocular discomfort symptoms

PURPOSE

To evaluate the changes in ocular surface parameters during orthokeratology lens wear and determine their correlations with ocular discomfort symptoms.

METHODS

Fifty individuals were enrolled in this prospective pilot study. Clinical evaluation of the ocular surface included the ocular surface disease index, slit-lamp examination, Keratograph 5M, optical quality analysis system, and corneal staining. After baseline examinations, clinical tests were performed at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months after orthokeratology lens wear. Correlations between ocular discomfort symptoms and signs of ocular discomfort were evaluated.

RESULTS

Overall ocular surface disease index score and two subscale scores (ocular symptoms and vision-related function) significantly increased at the 3-month visit (P < 0.05), and decreased to levels close to baseline at the12-month visit (P > 0.05). The basic objective scatter index and the mean tear film objective scatter index increased, peaking at 3-month visit (P < 0.05) and gradually decreased thereafter. The modulation transfer function cut-off significantly decreased at the 3-month visit (P < 0.05). During the 12-month study period, the overall ocular surface disease index score and vision-related function score were significantly and positively correlated with the basic objective scatter index and mean tear film objective scatter index (P < 0.05). After 1 week of lens wear, Grade 1 corneal staining increased to 16.4 %, mostly involving the central and inferior cornea.

CONCLUSIONS

Orthokeratology lens wear increased ocular discomfort symptoms and decreased the function of tear film, mainly within 3 months of lens wear. Tear-related visual function parameters were correlated with ocular discomfort. A new parameter, tear film objective scatter index, measured with the optical quality analysis system, was more sensitive in detecting the quality and stability of tear film than traditional indicators.

Topical review of the relationship between contact lens wear and meibomian gland dysfunction

Contact lens (CL) wearers often suffer from ocular discomfort, which leads to cessation of CL wear. About 30% to 50% of CL wearers complain of dry eye (DE) symptoms. Meibomian gland dysfunction (MGD) is considered the most common cause of evaporative DE. Numerous studies have investigated whether CL wear might affect the meibomian glands. This manuscript reviews studies examining the relationship between CL use and MGD. A PubMed database search was conducted for studies published between 1980-2021 with one or a combination of search terms related to "meibomian gland", "meibomian gland dysfunction", "contact lens", and/or "dry eye". Of the 115 papers reviewed, 22 articles were identified that examined the association between CL and MGD. Fifteen showed that CL wear affects the morphology and function of meibomian glands (MGs), while seven reported no significant impact of CL wear on MGs. This review provides an overview of these studies, emphasizing the diagnostic tests of MGD and conclusions. The review highlights the need for longitudinal prospective large cohort studies with control non- CL wearers to clarify the ambiguous relationship between MGD and CL wear, with special attention to varying CL material and wear times in order to identify the long-term impact of CLs on MG.

Application of orthokeratology on myopia control and its effect on ocular surface and meibomian gland function in Chinese myopic adolescents

Purpose

This study aimed to investigate the influence of orthokeratology (OK) on myopia control and ocular surface and meibomian gland function in myopic adolescents.

Methods

A prospective study was conducted over a 12-month period. The subjects were classified into two groups, namely, the OK lens group and the frame glasses control group. Axial length, corneal curvature, ocular surface, and meibomian gland parameters were measured at baseline, 1, 3, 6, and 12 months after wearing OK lenses.

Results

The axial length growth rate in the OK group was significantly slower than in the control group (P < 0.01). The naked eye vision and the ocular surface disease index (OSDI) scores recorded 1, 3, 6, and 12 months after wearing OK lenses were significantly higher than the scores recorded before wearing OK lenses. There was no significant difference in other ocular parameters at each follow-up time point compared with pre-wearing (P > 0.05). After using the OK lens for 6 months, the OSDI score and corneal fluorescein staining (CFS) score increased significantly (P < 0.001), but there were no significant differences in other parameters among the groups. No infectious keratitis occurred during the study.

Conclusion

These results provide evidence that the use of OK lenses can control the axial growth and progress rate of myopia compared with frame glasses. During the 12-month follow-up, although wearing OK lenses may have aggravated dry eye symptoms, each patient's ocular surface and meibomian gland function did not change significantly, indicating that the use of OK lenses is a relatively safe modality for the control of myopia in adolescents.

The impact of contact lenses on meibomian gland morphology

Despite years of experience with contact lenses, controversy remains as to whether contact lenses adversely impact the meibomian glands (MG). This review summarizes the present body of evidence, showing that contact lens wear is associated with alterations in MG morphology (up to 80% higher gland atrophy compared to non-wearers) and qualitative changes in MG secretion. Key factors such as duration of contact lens wear, contact lens type (e.g., soft vs. rigid), edge design, and material modulus of elasticity are discussed in relation to the extent of MG morphological changes, the quality of MG secretion and other ocular surface parameters. Longitudinal studies of sufficient statistical power are needed to better understand how contact lens wear affects the MG, risk factors, and the clinical sequelae of these changes.

Evaluation of the meibomian glands using the tear interferometer wearing orthokeratology lenses

Background

To investigate the impact of orthokeratology wear on meibomian glands in Korean pediatric population using the tear interferometer.

Methods

Fifty-three orthokeratology wearers and 79 non-lens wearers were evaluated using the LipiView® II ocular surface interferometer which shows incomplete blink rate, average lipid layer thickness, and meiboscores.

Results

No significant differences in the incomplete blink rate and meiboscores for upper eyelids, but the lipid layer thickness and meiboscores for lower eyelids were significantly higher in the Ortho-K group than in the control group (p = 0.024 and 0.007, respectively). Correlation analysis showed no significant correlation between the duration of orthokeratology wear and the parameters measured by LipiView® (p > 0.05 for all). Among subgroups based on average duration of lens wear, the longer duration (≥ 24 months) subgroup showed higher meiboscores of lower eyelids (p = 0.011), but no other significant differences.

Conclusions

Ortho-K wearers showed no significant differences in the incomplete blink rate and meiboscores of upper eyelids, but they were associated with increased LLT and higher meiboscores of lower eyelids. Thorough examination and close monitoring of orthokeratology wearers is necessary. Prospective and observational studies are needed to further elucidate the relationship between Orthokeratology and meibomian glands.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02365-3.

The effect of orthokeratology treatment zone decentration on myopia progression

Background

This study aimed to compare the changes in the axial length (AL) in myopic children that wear centered and decentered orthokeratology (Ortho-K).

Methods

This retrospective study included 217 subjects who were treated with an Ortho-K lens for >12 months. The subjects were divided into three groups based on the magnitude of the Ortho-K lens treatment zone decentration: mildly, moderately, and severely decentered groups. Distance and direction of treatment zone decentration were calculated using software that was developed in-house. The AL changes in different groups were compared.

Results

Based on the distance of the treatment zone decentration, 65 children (65 eyes) were included in the mildly decentered group, 114 children (114 eyes) in the moderately decentered group, and 38 children (38 eyes) in the severely decentered group. The mean decentration distance in the three groups was 0.35 ± 0.11 mm, 0.71 ± 0.13 mm, and 1.21 ± 0.22 mm, respectively. The mean AL increase in the three groups after 12 months of Ortho-K lens wear was 0.24 ± 0.21 mm, 0.23 ± 0.18 mm, and 0.19 ± 0.20 mm, respectively. There were no significant differences in AL changes among the three groups.

Conclusions

Ortho-K lens decentration is common in clinical practice. The AL change after Ortho-K lens wear was not significantly different in subjects with different magnitudes of Ortho-K lens decentration. Fitting the Ortho-K lens in the properly centered zone is recommended to ensure the safety of Ortho-K lens wear and to maintain visual quality.

Orthokeratology Lens Wear for 2 Years in Children Did Not Alter Tear Film Lipid Thickness by Non-Invasive Interferometry

Purpose

Previous studies suggest that overnight orthokeratology (OOK) may be detrimental to tear function. We aimed to investigate the effect of OOK on lipid layer thickness (LLT), blink pattern, and meibomian gland and elucidate the relationship of these variables.

Methods

Thirty-seven participants who wore OOK lenses every night for at least 2 years and twenty-four healthy non-contact lens wearers (controls) were enrolled in this retrospective study. LipiView interferometry, blink pattern analysis, the ocular surface status, and morphology and function of the meibomian gland were determined.

Results

The OOK group and healthy controls had similar LLT, blink patterns, ocular surface status, and the function of the meibomian gland. OOK participants demonstrated higher meiboscore in the lower eyelids (p < 0.05) but not in the upper eyelids. Within the OOK group, LLT was significantly impacted by the partial blink rate (p < 0.05) and the total score of the upper meibomian gland (p = 0.10).

Conclusions

Wearing OOK for 2 or more years increased lower eyelid meibomian gland dropout but did not have a reduction of LLT.

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

Does Orthokeratology Wearing Affect the Tear Quality of Children?

Orthokeratology is currently known as one of the most effective methods of myopia control in the process of rapid deterioration of the global myopia prevalence. As orthokeratology is widely used, it is necessary to evaluate its complications reasonably and accurately. Eye surface problems in children, such as dry eyes, have received increasing attention. At present, there is no conclusive evidence on how orthokeratology affects the ocular surface, especially the tears. To our knowledge, this is the first study to explore the relationship between orthokeratology lenses and tears through meta-analysis. However, it is still challenging to get a convincing conclusion and a higher level of evidence in this meta-analysis. Reasons for this include limitation of study design, lack of clarity on important confounding factors, lack of appropriate statistical tools, and other biases. This paper will analyze the dilemma existing in the current research from different perspectives to provide meaningful information for future studies in this field.

Tear Lipid Layer Thickness in Children after Short-Term Overnight Orthokeratology Contact Lens Wear

Meibomian gland lipid secretion is important to the stability of the tear film and ocular surface comfort. Changes in the tear film’s lipid layer thickness (LLT) after orthokeratology treatment may reflect underlying changes to the meibomian gland function. The purpose of this study was to investigate the features of the tear lipid layer in normal children and the effects of short-term orthokeratology treatment. Altogether, 163 myopic children (age: 10.7 ± 1.9 years, 8–15 years; 71 males) with no contact lens use history were enrolled in this study, of whom 56 were successfully fitted with orthokeratology lenses and completed the 1-month study. The tear film’s LLT (average, maximum, and minimum) and blinking pattern were measured by a LipiView® interferometer in 163 participants at baseline and in 56 orthokeratology participants at 1 week and 1 month after overnight lens wear. Results show that LLT (average) was 58.09 ± 21.66 nm in Chinese normal children. LLT was significantly correlated with rate of partial blinks at every follow-up (all $p<0.05$ ). Compared to baseline, the LLT (average and minimum) and partial blinks (number and rate) at 1 week and 1 month after orthokeratology treatment both significantly increased, and the increase of LLT was correlated with elevation of rate of partial blinks. In conclusion, LLT was shown to be elevated after short-term overnight orthokeratology treatment and was related to change in rate of partial blinks. Further studies are needed to clarify the long-term effect and the underlying mechanism.

Analysis of tear film spatial instability for pediatric myopia under treatment

In Taiwan, the prevalence of myopia in children between 6 and 18 years old is over 80%, and high myopia accounts for over 20%, which turned out to be in the leading place worldwide. Orthokeratology and low-dose atropine are proven treatments to reduce myopia progression, though the potential corneal disturbances remain an issue in young populations. The alteration of the tear film is widely discussed but there is no consensus to date, so we aim to investigate the tear film spatial instability in children with myopia control using atropine or orthokeratology. Thirty-eight treatment-naïve participants and 126 myopic children under treatments were enrolled. The ocular surface homeostasis, spatial distribution of tear break-up, and high-order aberrations (HOAs) of the corneal surface were assessed. We found out that myopic children treated with either atropine or orthokeratology showed ocular surface homeostasis similar to that in treatment-naïve children. Nevertheless, children treated with orthokeratology presented higher HOAs (p < 0.00001) and a tendency of the first tear break-up zone at the inner half of the cornea (p = 0.04). This unique spatial instability of the tear film associated with myopia treatment might provide a more focused way of monitoring the pediatric tear film instability.

The role of meibography in ocular surface diagnostics: A review

The meibomian glands are lipid-secreting glands located in the tarsal plates, whose secretory products cover the tear film, thereby reducing evaporation as well as ensuring lubrication of the ocular surface. The meibomian glands can be visualized at different levels of magnification by infrared meibography, laser confocal microscopy, and optical coherence tomography. These imaging modalities have been subject to much research and progress in clinical practice and have shaped our current understanding of meibomian glands in health and disease. In this review, we explore the evolution of meibography over the past decades, the major contributions of various meibographic modalities, and discuss their clinical significance.

Effect of orthokeratology on precision and agreement assessment of a new swept-source optical coherence tomography biometer

Background

To evaluate the effect of orthokeratology on precision of measurements in children using a new swept-source optical coherence tomography (SS-OCT) optical biometer (OA-2000), and agreement between its measurements and those provided by the commonly used IOLMaster based on partial coherence interferometry (PCI).

Methods

This study recruited fifty-one eyes of 51 normal children (8–16 years). An operator took measurements with the two biometers. Then, a second operator took measurements with the SS-OCT biometer. After orthokeratology was performed for one month, the same operators repeated the same procedures. Axial length (AL), mean keratometry (Km) at 2.5 mm and 3.0 mm diameters (Km_2.5 and Km_3.0), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and corneal diameter (CD) were analyzed.

Results

With the SS-OCT optical biometer, the test-retest repeatability of AL measurements was < 0.06 mm. For all parameters, the coefficients of variation were < 1.23% and the intraclass correlation coefficients were > 0.95. The 95% limits of agreement of difference between the two devices for CD parameter were up to 1.53 mm. After orthokeratology, the fluctuation ranges of difference for Km3.0 measurement was 1.11 times higher than before orthokeratology, while the absolute values of difference for AL, Km2.5, ACD and CD measurements were comparable.

Conclusions

Before and after orthokeratology, the SS-OCT biometer showed high repeatability and reproducibility for all measurements. Wearing orthokeratology contact lenses affected the agreement between SS-OCT and PCI biometers for Km3.0 measurements. The CD measurement showed poor agreement between the two devices.

Meibomian Gland Dropout, not Distortion, Can Distinguish Dry Eyes from Normal Eyes in Contact Lens Wearers

PURPOSE

To examine the effectiveness of using meibomian gland (MG) dropout and distortion for dry eye disease (DED) diagnosis in a young population with long-term contact lens (CL) wear.

METHODS

Seventy-three CL-wearers and 68 non-CL-wearers (20-28 years old) participated in the study. The diagnosis of DED was based on an ocular surface disease index ≥ 13, and a noninvasive breakup time < 10 seconds or positive corneal fluorescein staining. The MG dropout and distortion in each subject were quantified with non-invasive meibography. Receiver operating characteristic (ROC) curves were created to evaluate the effectiveness of using MG dropout and distortion to determine the presence of DED in CL-wearers and non-CL-wearers.

RESULTS

In non-CL-wearers, the MG distortion was significantly higher in DED subjects than in normal subjects (3.83 ± 1.81 versus 1.59 ± 1.04). In CL-wearers, MG distortion was not significantly different (5.12 ± 4.11 versus 5.51 ± 3.15 in normal and DED subjects respectively). The area under the ROC curve (AUC) for MG distortion was 0.783 in the non-CL-wearers, but 0.507 in CL-wearers. In non-CL-wearers, MG dropout was significantly higher in DED subjects than in normal subjects (0.22 ± 0.08 versus 0.15 ± 0.06). In CL-wearers, MG dropout was also significantly higher in DED subjects than in normal subjects (0.29 ± 0.11 versus 0.22 ± 0.08). The AUC for MG dropout used to classify DED was 0.740 in the non-CL-wearers and 0.715 in CL-wearers.

CONCLUSIONS

MG dropout was effective in distinguishing subjects with DED from normal subjects in both CL wearers and non-CL wearers. MG distortion can only distinguish DED subjects from normal ones in non-CL wearers, but not in CL wearers.

Influence of Overnight Orthokeratology Lens Treatment Zone Decentration on Myopia Progression

Purpose

To investigate the effect of OK lens treatment zone decentration on myopia control.

Methods

We retrospectively selected 30 OK lens wearers who met the following conditions in our hospital from more than 1300 cases: wearing lens in both eyes and only one eye was off-center while the other one was centric for more than 12 months. During the period of follow-up, the UCVA of each eye was better than 0.1 of logMAR and there were no obvious tropia, Kappa angle, and complications such as glare and diplopia.

Result

Among 30 cases, 15 are males and 15 are females, with an average age of 9.3 ± 1.51Y. There were no significant differences in equivalent spherical lens, astigmatism, e value, flat K, steep K, astigmatism, lens diameter, and toric between the two groups (p > 0.05). The average distance of decentration was 0.73 ± 0.25 mm. Axis growth per year in was 0.20 ± 0.24 mm the OK-lens-decentered group and 0.29 ± 0.20 mm in the OK-lens-centric group, which shows significant difference between them (p < 0.05). According to the direction of decentration, 30 decentered eyes were divided into temporal group (20 eyes) and other direction group (10 eyes). The efficiency of myopia control (the growth of AL per year in OK-lens-decentered eye/the growth of AL per year in the contralateral OK-lens-centric eye) was 0.69 ± 0.50 in the temporal decentration group and 0.75 ± 0.52 in the other direction group, showing no significant difference between them (p > 0.05). There was no significant correlation between the efficiency of myopia control and the degree of decentration among temporal decentration group (p > 0.05).

Conclusion

This self-control study without much interference factors shows that the decentration of OK lens can delay the development of myopia more effectively than being centric when uncorrected visual acuity was acceptable without obvious corneal complications, glare, or ghosting.

Tracking the Reflective Light Particles Spreading on the Cornea: An Emerging Assessment for Tear Film Homeostasis

Purpose

To implement an emerging noninvasive approach for assessing the dynamic tear film (TF) homeostasis.

Methods

The video records of dynamic TF from 12 healthy orthokeratology lens wearers were obtained by a clinically available TF analyzer and decomposed as image sequences. The trajectories of TF particles were analyzed by two tracking models, the full-span model (FSM) and the fixed-duration model (FDM). FSM tracked a particle for a complete opening blink cycle, while FDM tracked 1 second of the same cycle. A power-law fitting operation \begin{document}\newcommand{\bialpha}{\boldsymbol{\alpha}}\newcommand{\bibeta}{\boldsymbol{\beta}}\newcommand{\bigamma}{\boldsymbol{\gamma}}\newcommand{\bidelta}{\boldsymbol{\delta}}\newcommand{\bivarepsilon}{\boldsymbol{\varepsilon}}\newcommand{\bizeta}{\boldsymbol{\zeta}}\newcommand{\bieta}{\boldsymbol{\eta}}\newcommand{\bitheta}{\boldsymbol{\theta}}\newcommand{\biiota}{\boldsymbol{\iota}}\newcommand{\bikappa}{\boldsymbol{\kappa}}\newcommand{\bilambda}{\boldsymbol{\lambda}}\newcommand{\bimu}{\boldsymbol{\mu}}\newcommand{\binu}{\boldsymbol{\nu}}\newcommand{\bixi}{\boldsymbol{\xi}}\newcommand{\biomicron}{\boldsymbol{\micron}}\newcommand{\bipi}{\boldsymbol{\pi}}\newcommand{\birho}{\boldsymbol{\rho}}\newcommand{\bisigma}{\boldsymbol{\sigma}}\newcommand{\bitau}{\boldsymbol{\tau}}\newcommand{\biupsilon}{\boldsymbol{\upsilon}}\newcommand{\biphi}{\boldsymbol{\phi}}\newcommand{\bichi}{\boldsymbol{\chi}}\newcommand{\bipsi}{\boldsymbol{\psi}}\newcommand{\biomega}{\boldsymbol{\omega}}{\rm{MMS}}\left( t \right) = {\rm{\alpha }} \times {t^{ - {\rm{\beta }}}}\end{document} was used to extract homeostasis markers based on the tracking model for each subject.

Results

Comparing two tracking models (N = 6), only one subject had statistical difference in averaged momentary moving speed (MMS; P = 0.0488), while none had significant difference in averaged momentary moving direction (MMD). However, both models showed good correlations in average MMS (ρ = 0.94, P = 0.0048) and MMD (ρ = 1.00, P < 0.0001) and all extracted homeostasis markers [α, β, MMS(0.1), and MMS(2.0)]. Assessing interblink reliability in these markers under FDM tracking (N = 12), only one subject in the MMS (0.1) and another subject in the MMS (2.0) were outside 95% limits of agreement, respectively.

Conclusions

FDM is a good alternative to FSM and has tracking properties of higher efficiency and easier implementation. The homeostasis markers under FDM tracking showed a good interblink consistence; therefore this approach will be a promising method for analyzing dynamic TF homeostasis in future practice.

Translational Relevance

FDM analytical architecture can practice the past experimental platform on a TF analyzer to obtain homeostasis markers of TF.

Meibography: A Japanese Perspective

Meibography allows observation of meibomian glands in an objective and repeatable manner. Original meibography systems were invasive and not readily adopted by ophthalmology clinics. The development of noncontact infrared meibography allowed the rapid and noninvasive observation of meibomian glands, and such systems have now been widely adopted for standard examinations in dry eye clinics. Noncontact meibography has also spurred research into meibomian glands and has been applied to evaluation of their structure and status in various ocular surface diseases. Although the images obtained by meibography are objective and repeatable, the interpretation of these images is subjective, with the relationship between image features and actual gland structure and composition remaining unclear. Additional clinical and basic research with regard to the interpretation of meibography images is thus necessary. Future improvements to meibography will likely provide new insights into the pathophysiology of meibomian gland diseases as well as enhance its contribution to the diagnosis and evaluation of treatments for such diseases.

The Influence of Overnight Orthokeratology on Ocular Surface and Meibomian Gland Dysfunction in Teenagers with Myopia

Purpose

The aim of this study was to investigate the effect of overnight orthokeratology (OOK) on ocular surface and meibomian gland dysfunction in teenagers with myopia.

Methods

A total of 59 subjects were recruited in this prospective study. The following tests were performed before and after 1, 3, 6, 12, and 24 months of OOK lens wear, including ocular surface disease index (OSDI) questionnaire, slit-lamp examination, and Keratograph 5M.

Results

No infectious keratitis occurred during the study. OSDI scores increased gradually and reached the maximum at 6 months of OOK wear (P < 0.001). The meniscus height was significantly increased at 1 and 3 months after the initiation of OOK (P=0.006, P=0.035). The corneal fluorescein staining at 1, 3, 6, 12, and 24 months after wearing OOK were all increased than the prewearing level with significant difference (P=0.014, P=0.036, P < 0.001, P < 0.001, and P=0.008, respectively). The first and the average tear film NIKBUT were all higher than the prewearing level, but there was no significant difference between every follow-up time points (P > 0.05). The lid margin abnormalities were significantly increased (P=0.003, P=0.038, and P=0.015) at 6, 12, and 24 months after the initiation of OOK. There was no significant difference in the meibomian gland orifice scores at each follow-up time points compared to the prewearing level (P > 0.05). The meibomian gland lipid secretion scores after wearing OOK were higher than those of the prewearing level, however, without statistically significant difference (P > 0.05). No significant differences of the degree of difficulty of lipid excretions were detected after the initiation of OOK (P > 0.05). There was no significant difference in meibomian gland dropout scores between all follow-up time points and the prewearing level (P=1.000).

Conclusion

OOK increased the symptoms of dry eye and decreased the function of tear film by affecting the meniscus height and BUT. OOK did not affect the function of meibomian glands.Clinical Study registration number: ChiCTR18000185708.

Assessment of Tear Film and Bulbar Redness by Keratograph 5M in Pediatric Patients After Orthokeratology

OBJECTIVES

To assess the tear meniscus height (TMH), noninvasive tear breakup time (NITBUT), and bulbar redness in pediatric patients after orthokeratology (OK).

METHODS

Pediatric patients who underwent overnight OK between December 2014 and November 2017 were retrospectively investigated. According to the time of wearing, subjects were divided into three groups: 1-week, 1-month, and over 1-year. Age-matched subjects were recruited as a control group. Keratograph 5M was used to assess TMH, NITBUT-first, NITBUT-average, and bulbar redness score.

RESULTS

A total of 106 subjects aged from 7 to 15 years were included. Compared with control group, NITBUT-first was significantly lower in 1-week group (P=0.036) and NITBUT-average was significantly lower in 1-month group (P=0.019). Compared with over 1-year group, NITBUT-first was significantly lower in 1-week and 1-month groups (P=0.014, P=0.035, respectively), and NITBUT-average was significantly lower in 1-month group (P=0.022). Bulbar redness score was significantly lower in 1-month group than 1-week group (P=0.004). No significant difference in TMH was found between all groups. Significant correlation was found between NITBUT-first and NITBUT-average in all subjects (R=0.812, P<0.001). No other significant correlations were found between variables included TMH, NITBUT, bulbar redness score, or target correction.

CONCLUSIONS

As a noninvasive method, Keratograph 5M was easily to be applied on pediatric patients. The OK lens did not induce significant tear deficiency or bulbar redness, but might affect tear film stability in a short term after wearing.

Influence of overnight orthokeratology lens fitting decentration on corneal topography reshaping

Background

This retrospective study was designed to investigate the sole influence of orthokeratology (OK) lens fitting decentration on the Zernike coefficients of the reshaped anterior corneal surface.

Methods

This study comprised a review of 106 right eyes and measurements of corneal topography both before OK and at 1-month follow-up visit. A routine was designed to calculate local corneal surface astigmatism and assist the determination of OK lens fitting decentration from pupil center. The pupil-centered corneal Zernike coefficients of baseline (PCCB) and post-treatment (PCCP) were calculated. Meanwhile, the OK-lens-centered corneal Zernike coefficients of post-treatment (OCCP) were also calculated and considered as the presumptive ideal fitting group without decentration. Relationships between lens fitting decentration and the change of Zernike coefficients including (PCCP − PCCB) and (PCCP − OCCP) were analyzed.

Results

Patients with a mean age of 11 ± 2.36 years old had an average spherical equivalent refractive error of −3.52 ± 1.06 D before OK. One month after treatment, OK lens fitting decentration from pupil center was 0.68 ± 0.35 mm. RMS of 3rd-order (P < 0.05), RMS of 4th-order (P < 0.001) and RMS of total high order (P < 0.001) corneal Zernike coefficients were increased in PCCP by comparing with OCCP, which was solely caused by lens fitting decentration. Nevertheless, no significant difference was observed in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_2^0 $$\end{document}C20 (P > 0.05). For the high order corneal Zernike coefficients in (PCCP – OCCP), radial distance of decentration was correlated with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^{-1} $$\end{document}C3−1 (r = −0.296, P < 0.05), \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^1 $$\end{document}C31 (r = −0.396, P < 0.001), and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_4^0 $$\end{document}C40 (r = 0.449, P < 0.001), horizontal decentration was significantly correlated with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^1 $$\end{document}C31 (r = 0.901, P < 0.001) and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_5^1 $$\end{document}C51 (r = 0.340, P < 0.001), and vertical decentration was significantly correlated with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^{-1} $$\end{document}C3−1 (r = 0.904, P < 0.001).

Conclusions

OK lens fitting decentration within 1.5 mm hardly influenced the change of corneal spherical power for myopia correction, but significantly induced additional corneal high order Zernike coefficients including \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^{-1} $$\end{document}C3−1, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_3^1 $$\end{document}C31, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_4^0 $$\end{document}C40, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {C}_5^1 $$\end{document}C51.

Functional Morphology of the Lipid Layer of the Tear Film

Meibomian glands secrete the oily layer of the tear film, which prevents excessive evaporation of tear fluid. Dysfunction of meibomian glands is not only one of the causes of evaporative dry eye but also one of the main causes of entire dry eye. To understand the pathophysiology of meibomian gland dysfunction, it is important to evaluate both the morphology and function of the meibomian gland. We previously reported that meibography enabled visualization of the morphology of the meibomian gland. Meanwhile, tear interferometry was introduced as an evaluation method for the function of the meibomian gland. We combined observations of the oily layer and the aqueous layer of the tear film and found that a tear film compensatory system may work toward maintenance of tear film homeostasis. In this review, we describe both morphological evaluation systems for the meibomian gland, including noninvasive meibography, and functional evaluation systems, including tear interferometry. We further describe the morphological changes of the meibomian glands in various ocular surface diseases. Finally, we demonstrate the concept of a tear film compensatory system and propose a method for tear film component-oriented diagnosis.

New insights into the morphology and function of meibomian glands

Meibomian glands secrete meibum, which gives rise to the lipid layer of the tear film and thereby prevents excessive evaporation of tear fluid. Meibomian gland dysfunction (MGD) is a major causative condition of evaporative dry eye, which is more common than the aqueous-deficient type of dry eye. Noninvasive meibography relies on infrared light and an infrared-sensitive camera to reveal the morphology of meibomian glands in both the upper and lower eyelids, whereas tear interferometry allows both qualitative and quantitative evaluation of the lipid layer of the tear film. These two techniques not only provide valuable clinical information related to dry eye but also allow clinical evaluation of MGD. Tear interferometry also has the potential to distinguish the condition of the tear film between normal individuals and dry eye patients. Furthermore, combined evaluation of the noninvasive breakup time of the tear film and the interferometric fringe pattern as determined by tear interferometry allows classification of the subtype of dry eye disease.

Effect of overnight orthokeratology on conjunctival goblet cells

OBJECTIVE

To evaluate the differences between goblet cell density (GCD) and symptomatology after one month of orthokeratology lens wear.

METHODS

A pilot, short-term study was conducted. Twenty-two subjects (29.7±7.0 years old) participated voluntarily in the study. Subjects were divided into two groups: habitual silicone hydrogel contact lens wearers (SiHCLW) and new contact lens wearers (NCLW). Schirmer test, tear break up time (TBUT), Ocular Surface Disease Index (OSDI) questionnaire and conjunctival impression cytology. GCD, mucin cloud height (MCH) and cell layer thickness (CLT) were measured. All measurements were performed before orthokeratology fitting and one month after fitting to assess the evolution of the changes throughout this time.

RESULTS

No differences in tear volume and TBUT between groups were found (p>0.05). However, the OSDI score was statistically better after one month of orthokeratology lens wear than the baseline for the SiHCLW group (p=0.03). Regarding the goblet cell analysis, no differences were found in CLT and MCH from the baseline visit to the one month visit for the SiHCLW compared with NCLW groups (p>0.05). At baseline, the GCD in the SiHCLW group were statistically lower than NCLW group (p<0.001). There was a significant increase in GCD after orthokeratology fitting from 121±140cell/mm(2) to 254±130cell/mm(2) (p<0.001) in the SiHCLW group.

CONCLUSION

Orthokeratology improves the dry eye subject symptoms and GCD after one month of wearing in SiHCLW. These results suggest that orthokeratology could be considered a good alternative for silicone hydrogel contact lens discomfort and dryness.