A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear

Ran, Ziying; Moore, Joshua L.; Jiang, Fan; Guo, Hongmei; Eliasy, Ashkan; Lopes, Bernardo; Bao, Fangjun; Jiang, Jun; Abass, Ahmed; Elsheikh, Ahmed

doi:10.1098/rsos.211108

Cited by 7 publications

(5 citation statements)

References 40 publications

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“…The RPC in Ortho-K, believed to be achieved by epithelial thinning in the central cornea and thickening towards the periphery, has associated biological and mechanical risks. Clinically, there is a risk of reducing resistance to microbial infection by weakening the central epithelial barrier [9,10,[66][67][68][69]. From the mechanical point of view, lens-eye interactions can result in variable visual results due to residual refractive error [70].…”

Section: Discussionmentioning

confidence: 99%

FEA-Based Stress–Strain Barometers as Forecasters for Corneal Refractive Power Change in Orthokeratology

Wu,

Lin,

et al. 2024

Bioengineering

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Purpose: To improve the effectivity of patient-specific finite element analysis (FEA) to predict refractive power change (RPC) in rigid Ortho-K contact lens fitting. Novel eyelid boundary detection is introduced to the FEA model to better model the effects of the lid on lens performance, and stress and strain outcomes are investigated to identify the most effective FEA components to use in modelling. Methods: The current study utilises fully anonymised records of 249 eyes, 132 right eyes, and 117 left eyes from subjects aged 14.1 ± 4.0 years on average (range 9 to 38 years), which were selected for secondary analysis processing. A set of custom-built MATLAB codes was built to automate the process from reading Medmont E300 height and distance files to processing and displaying FEA stress and strain outcomes. Measurements from before and after contact lens wear were handled to obtain the corneal surface change in shape and power. Tangential refractive power maps were constructed from which changes in refractive power pre- and post-Ortho-K wear were determined as the refractive power change (RPC). A total of 249 patient-specific FEA with innovative eyelid boundary detection and 3D construction analyses were automatically built and run for every anterior eye and lens combination while the lens was located in its clinically detected position. Maps of four stress components: contact pressure, Mises stress, pressure, and maximum principal stress were created in addition to maximum principal logarithmic strain maps. Stress and strain components were compared to the clinical RPC maps using the two-dimensional (2D) normalised cross-correlation and structural similarity (SSIM) index measure. Results: On the one hand, the maximum principal logarithmic strain recorded the highest moderate 2D cross-correlation area of 8.6 ± 10.3%, and contact pressure recorded the lowest area of 6.6 ± 9%. Mises stress recorded the second highest moderate 2D cross-correlation area with 8.3 ± 10.4%. On the other hand, when the SSIM index was used to compare the areas that were most similar to the clinical RPC, maximum principal stress was the most similar, with an average strong similarity percentage area of 26.5 ± 3.3%, and contact pressure was the least strong similarity area of 10.3 ± 7.3%. Regarding the moderate similarity areas, all components were recorded at around 34.4% similarity area except the contact pressure, which was down to 32.7 ± 5.8%. Conclusions: FEA is an increasingly effective tool in being able to predict the refractive outcome of Ortho-K treatment. Its accuracy depends on identifying which clinical and modelling metrics contribute to the most accurate prediction of RPC with minimal ocular complications. In terms of clinical metrics, age, Intra-ocular pressure (IOP), central corneal thickness (CCT), surface topography, lens decentration and the 3D eyelid effect are all important for effective modelling. In terms of FEA components, maximum principal stress was found to be the best FEA barometer that can be used to predict the performance of Ortho-K lenses. In contrast, contact pressure provided the worst stress performance. In terms of strain, the maximum principal logarithmic strain was an effective strain barometer.

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Section: Discussionmentioning

confidence: 99%

FEA-Based Stress–Strain Barometers as Forecasters for Corneal Refractive Power Change in Orthokeratology

Wu,

Lin,

et al. 2024

Bioengineering

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“…Increased min-max has been reported by some studies [ 180 , 184 ], particularly in OK lens users for more than two weeks [ 184 ]. Although some studies reported a significant increase in the corneal stromal thickness after OK lenses [ 91 , 181 ], there was no significant change in stromal posterior surface radii of curvature [ 181 ], and the refractive changes after OK were caused mainly by changes in CET and anterior stromal curvature and not correlated with stromal thickness alteration [ 91 , 181 ].…”

Section: Contact Lens Usementioning

confidence: 99%

“…Alterations in the ETM profle associated with OK lenses in treating low-to-moderate myopia (<5 diopters) and <1.5 diopters of astigmatism have been investigated. In the central 2 mm zone, almost all studies have reported decreased central CET after the use of OK lenses for myopic eyes [6,29,91,148,[180][181][182][183][184][185]. Regarding the paracentral region (2-5 mm), results are less consistent; diferent fndings from diferent studies suggest no signifcant change [180], signifcant decreases in thickness in temporal [6,181,184], nasal [181], and inferior sectors [184], nonsignifcant increase in CET along the vertical meridian [181], and signifcant thinning in the paracentral zone with more prominence in temporal and inferior sectors [91].…”

Section: Orthokeratology (Ok)mentioning

confidence: 99%

“…In the central 2 mm zone, almost all studies have reported decreased central CET after the use of OK lenses for myopic eyes [6,29,91,148,[180][181][182][183][184][185]. Regarding the paracentral region (2-5 mm), results are less consistent; diferent fndings from diferent studies suggest no signifcant change [180], signifcant decreases in thickness in temporal [6,181,184], nasal [181], and inferior sectors [184], nonsignifcant increase in CET along the vertical meridian [181], and signifcant thinning in the paracentral zone with more prominence in temporal and inferior sectors [91]. Concerning the midperipheral region (5-6 mm), fndings from a handful of studies include no signifcant change [180] and superior and inferior [6,184] thickening [183] with prominence in the nasal sector than temporal [91,185].…”

Section: Orthokeratology (Ok)mentioning

confidence: 99%

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Corneal Epithelial Thickness Mapping: A Major Review

Abtahi,

Beheshtnejad,

Latifi

et al. 2024

Journal of Ophthalmology

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The corneal epithelium (CE) is the outermost layer of the cornea with constant turnover, relative stability, remarkable plasticity, and compensatory properties to mask alterations in the underlying stroma. The advent of quantitative imaging modalities capable of producing epithelial thickness mapping (ETM) has made it possible to characterize better the different patterns of epithelial remodeling. In this comprehensive synthesis, we reviewed all available data on ETM with different methods, including very high-frequency ultrasound (VHF-US) and spectral-domain optical coherence tomography (SD-OCT) in normal individuals, corneal or systemic diseases, and corneal surgical scenarios. We excluded OCT studies that manually measured the corneal epithelial thickness (CET) (e.g., by digital calipers) or the CE (e.g., by confocal scanning or handheld pachymeters). A comparison of different CET measuring technologies and devices capable of producing thickness maps is provided. Normative data on CET and the possible effects of gender, aging, diurnal changes, refraction, and intraocular pressure are discussed. We also reviewed ETM data in several corneal disorders, including keratoconus, corneal dystrophies, recurrent epithelial erosion, herpes keratitis, keratoplasty, bullous keratopathy, carcinoma in situ, pterygium, and limbal stem cell deficiency. The available data on the potential role of ETM in indicating refractive surgeries, planning the procedure, and assessing postoperative changes are reviewed. Alterations in ETM in systemic and ocular conditions such as eyelid abnormalities and dry eye disease and the effects of contact lenses, topical medications, and cataract surgery on the ETM profile are discussed.

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“…13,14 Changes in stromal thickness after wearing the ortho-k lenses were inconsistent in different studies, 15–17 and the anterior and posterior stromal curvature radii did not change significantly. 18 Therefore, the shape of the epithelium after ortho-k treatment is important for evaluating the efficacy of lenses.…”

mentioning

confidence: 99%

Short-term Changes in Epithelial and Optical Redistribution Induced by Different Orthokeratology Designs

Meng,

Chen,

Zhe

et al. 2023

Eye &Amp; Contact Lens: Science &Amp; Clinical Practice

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Objectives: This study aimed to investigate corneal epithelial and topographic changes caused by two commercial myopia orthokeratology (ortho-k) designs. Methods: Twenty-six subjects fitted with vision shape treatment (VST) lenses and 30 subjects fitted with corneal reshaping therapy (CRT) lenses were reviewed 1 day, 1 week, and 1 month after lens initiation. A spectral-domain optical coherence tomography system was used to create epithelial maps that were in turn used to determine the average epithelial thickness of each zone and the diameter of treatment zone. By measuring the topographic tangential differential map, the treatment zone diameter and the power and width of the high convex zone (HCZ) were obtained. All epithelial thicknesses and topographic corneal variations recorded were analyzed. Results: At the central zone, the epithelial thickness changes (△ET) decreased significantly after 1 day of ortho-k in two groups. At 2- to 9-mm peripheral zone, ortho-k increased △ET until 1 week in the VST group, whereas it kept increasing in the CRT group after 1 week. At 1 month, the central △ET is −9.51±2.38 mm in the VST group, which was comparable to −8.72±3.43 mm in the CRT group. The nasal HCZ power and the △ET of nasal and inferior nasal were significantly larger in the CRT group. A positive correlation was found between the HCZ power and △ET generated by VST-type lenses inferiorly and temporally. For the CRT group, a positive correlation was found between inferior HCZ power and △ET. Conclusions: At the early stage of ortho-k, epithelial thickness and topography change quickly and simultaneously. Epithelial changes were in line with corneal topography reshaping. Epithelial and optical remodelling were affected by different lens types.

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A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear

Cited by 7 publications

References 40 publications

FEA-Based Stress–Strain Barometers as Forecasters for Corneal Refractive Power Change in Orthokeratology

FEA-Based Stress–Strain Barometers as Forecasters for Corneal Refractive Power Change in Orthokeratology

Corneal Epithelial Thickness Mapping: A Major Review

Short-term Changes in Epithelial and Optical Redistribution Induced by Different Orthokeratology Designs

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