Posterior cornea and thickness changes after scleral lens wear in keratoconus patients

PurposeTo evaluate the changes in the corneal thickness, anterior chamber depth and posterior corneal curvature and aberrations after scleral lens wear in keratoconus patients with and without intrastromal corneal ring segments (ICRS).MethodsTwenty-six keratoconus subjects (36.95 ± 8.95 years) were evaluated after 8 h of scleral lens wear. The subjects were divided into two groups: those with ICRS (ICRS group) and without ICRS (KC group). The study variables evaluated before and immediately after scleral lens wear included corneal thickness evaluated in different quadrants, posterior corneal curvature at 2, 4, 6 and 8 mm of corneal diameter, posterior corneal aberrations for 4, 6 and 8 mm of pupil size and anterior chamber depth.ResultsThere was a statistically significant corneal thinning (p < 0.05) in the inferior region of the KC group and in the superior region of the ICRS group. No change (p > 0.05) in the anterior chamber depth was found. The KC group showed a steepening (p < 0.05) in the temporal quadrant and a flattening that mainly affected to the superior-nasal quadrant. The ICRS group showed a steepening (p < 0.05) that mainly affected to the superior-nasal quadrant. Regarding posterior corneal aberrations, only changes (p < 0.05) in Z4 for 8 mm and Z8 for 4 mm were found in the KC group.ConclusionsShort-term scleral lens wear showed a thinning of the cornea and changes in the posterior corneal curvature affects different regions in keratoconus patients with and without ICRS.     

Scleral shape and its correlation with corneal parameters in keratoconus

PurposeTo assess the correlation of the scleral shape and corneal tomographic parameters in keratoconus.MethodsTwenty eyes of 15 keratoconus patients with no previous specialty lens wear or ocular surgery were included in this study. Corneal imaging was obtained with the Pentacam HR and three-dimensional (3D) corneoscleral maps were acquired using the Eye Surface Profiler, ESP. Sagittal height was calculated at the central corneal level (annulus of 0–4 mm radius), peripheral cornea (annulus 4–6 mm radius) and sclera (annulus 6–8 mm radius) using ESP maps and Pentacam HR (exclusively for the central cornea). The flattest and steepest regions of each annulus and the circumferential scleral asymmetry were calculated based on custom-made software. The Pearson correlation coefficient (r) was used to evaluate the correlation between corneal parameters as measured by Pentacam HR and scleral asymmetry.ResultsAnterior corneal parameters, such as flattest and steepest keratometry, were found to be correlated with scleral asymmetry in keratoconus (all r>0.5, p < 0.05). In contrast, anterior astigmatism showed poor correlation with the level of scleral irregularity (r=-0.11; p = 0.32). Other disease-specific parameters pertaining to the posterior corneal curvature and corneal thickness were not correlated with scleral asymmetry. The steepest regions of the central cornea, peripheral cornea, and sclera tended to share a common angle (r = 0.92; p < 0.001 for central cornea compared to sclera).ConclusionAnterior corneal parameters measured by corneal imaging are associated with the level of scleral asymmetry and the orientation of the steepest area of the sclera in eyes with keratoconus.     

Correlation of central and peripheral corneal thickness in healthy corneas

Purpose

To study the thickness profile of the normal cornea in order to establish any correlation between central and peripheral points.

Methods

Sixty-seven eyes of 40 patients were subjected to central corneal thickness measurement (CCT) with an ultrasound pachymeter (UP) and corneal thickness mapping with the Oculus Pentacam. The corneal apex thickness (CAT), pupil centre thickness (recorded as CCT and corresponded to CCT of UP) and thickness at the thinnest location (CTL) were obtained and compared with each other. Corneal thickness data at 3 mm and 7 mm temporally, nasally, superiorly and inferiorly from the corneal apex were obtained. The mean corneal thickness values along the 2, 4, 6, 8 and 10 mm diameter concentric circles, with the CTL as the centre, were also obtained. The above data at different points were statistically correlated.

Results

There was no significant difference between CCT readings measured by UP and Pentacam (P = 0.721). There was high positive correlation between the CAT values and the thickness at 3 mm (R ≥ 0.845, P < 0.001) and at 7 mm points (R ≥ 0.654, P < 0.001). A gradual increase in thickness was noted from the centre to the periphery with a high positive correlation between the CTL values and the mean thickness at the circles of 2, 4, 6, 8 and 10 mm (R ≥ 0.635, P < 0.001).

Conclusion

The results suggest that central corneal thickness can serve as a good guide for predicting peripheral thickness. For surgical procedures specifically undertaken at mid-peripheral and peripheral zones, the actual measurements at the site of surgery may confer some advantage.     

Evaluation of anterior segment parameters during and after pregnancy

PurposeTo compare the anterior segment parameters during pregnancy and post-pregnancy.Materials and methodsFifty-four healthy pregnant women in their third trimester with ages ranging from 18 to 38 years were included in the study. All of the patients underwent comprehensive ophthalmologic examinations, including refraction, anterior segment, and fundus examinations, intraocular pressure, and axial length measurements. In addition, anterior chamber angle, anterior chamber depth, anterior chamber volume, corneal volume, central corneal thickness, and keratometry values were measured by Pentacam Scheimpflug camera. All measurements were measured again 3 months after delivery.ResultsThe mean intraocular pressure, anterior chamber angle, anterior chamber depth, anterior chamber volume, corneal volume, central corneal thickness, and keratometry measurements were significantly different during pregnancy and post-pregnancy (p < 0.05 for all); however, the mean spherical refraction, cylindrical refraction, and axial length were not statistically significantly different during pregnancy and post-pregnancy (p > 0.05 for all).ConclusionsWe found that there is an increase in the anterior chamber parameters, corneal volume, corneal thickness, and corneal curvature and a decrease in intraocular pressure in the third trimester.     

Changes in corneal thickness,corneal volume,and densitometry after long-term orthokeratology wear

PurposeTo investigate changes in the corneal volume, corneal densitometry and pachymetry of young myopes wearing over-night orthokeratology (OK) contact lenses.MethodsThe medical records of 28 right eyes of young myopes wearing OK between 2013 and 2018 were reviewed retrospectively. The baseline refractive error, best corrected visual acuities at baseline and uncorrected visual acuity at the most recent visit were recorded. Corneal volume of the central 10 mm cornea; densitometry at central, nasal and temporal cornea; and pachymetry along the horizontal and vertical meridians were collected from the Pentacam® HR at baseline, after one night of lens wear, and at the latest visit.ResultsThe mean age of subjects was 12.03 ± 3.80 years at the time of OK lens fitting and wore OK overnight for a mean duration of 666 days (range 206–1736 days). The baseline spherical equivalent refractive error was ?3.03 ± 1.56 D (range ?1.00 to ?6.00 D). The corneal volume increased significantly after OK wear (p = 0.001). Corneal densitometry increased after OK wear, but the change did not reach statistical significance (p = 0.113). Pachymetry in the central cornea did not change significantly across all visits (p > 0.05) but increased significantly in the mid-peripheral regions of the cornea. Baseline refractive error was not found to be correlated with the changes in corneal volume, corneal densitometry, or pachymetry.ConclusionThe increase in corneal volume and densitometry and no significant change in the central corneal thickness may indicate the presence of corneal oedema from long-term OK wear. The baseline refraction was not correlated with the changes in corneal volume, densitometry or pachymetry.     

Prospective two year study of changes in corneal density following transepithelial pulsed,epithelium-off continuous and epithelium-off pulsed,corneal crosslinking for keratoconus

PurposeTo compare the corneal densitometry changes after transepithelial pulsed (t-ACXL), epithelium-off continuous (c-ACXL) and epithelium-off pulsed (p-ACXL), accelerated corneal crosslinking for patients with progressive keratoconus.MethodsProspective, interventional case series at a university hospital tertiary referral center. Forty eyes received t-ACXL, 40 eyes received c-ACXL, and 40 eyes received p-ACXL. Corneal tomography, densitometry and visual acuity were evaluated preoperatively and at 1, 3, 6, 12 and 24 months postoperatively.ResultsTotal densitometry values of the total layer over the annular diameters 0–12 mm expressed in grayscale units (GSU) showed no significant change after t-ACXL and p-ACXL but increased significantly after c-ACXL at 1 month (16.76 ± 2.38, P value < 0.01) and 3 months (16.12 ± 2.22, P value 0.04), returning to baseline levels at month 6 (14.97 ± 2.13, P value 0.99) and remained stable until final follow-up. At 1 month, the mean change in total densitometry value of the t-ACXL group (-0.53 ± 2.08) was significantly lower than the p-ACXL (0.70 ± 1.96 P value 0.04) and c-ACXL (1.97 ± 2.65 P value < 0.01). There was no statistical difference in the mean change in total densitometry between the three groups from 6 to 24 months. In the c-ACXL group, a higher degree of CXL-induced corneal haze at 1 month was observed in patients with steeper preoperative keratometry readings and in individuals where a greater flattening effect was achieved at 24 months.ConclusionsContinuous epithelium-off accelerated cornea crosslinking appears to induce more corneal haze than pulsed epithelium-off and transepithelial pulsed cornea crosslinking in the early postoperative period. Differences resolve by six-months.     

The influence of soft contact lens wear and two weeks cessation of lens wear on corneal curvature

IntroductionAccurate corneal measurements are crucial in corneal refractive surgery (CRS) to ensure successful outcomes. Soft contact lens (SCL) wear may result in changes to corneal curvature and structure. United States Food and Drug Administration (FDA) pre-operative guidelines recommend that prior to CRS, SCL wearers cease SCL wear for “at least two weeks before examination and treatment” [1]. Corneal curvature changes induced by SCL wear may take longer than two weeks to resolve.PurposeTo examine the effect of SCL wear on corneal curvature before and following two weeks SCL wear cessation. To explore the possible impact of different SCL materials and years of SCL wear.MethodsRetrospective data analysis, between a group of SCL wearers (SCL: n = 45); and a non-contact lens control group (NCL: n = 45). Corneal curvature parameters were measured using the Pentacam (Oculus, Germany), before and following two weeks cessation of SCL wear.ResultsNo significant differences in keratometry or Sagittal radius of curvature between SCL and NCL groups prior to or following SCL cessation. Tangential radius of curvature showed significant inferior steepening for the SCL group prior to SCL cessation (SCL vs. NCL; 7.77 ± 0.30 mm vs. 7.90 ± 0.30 mm; p = 0.04). Following two weeks cessation of SCL wear this appeared to have resolved.ConclusionsTwo weeks cessation of SCL wear appears sufficient for resolution of corneal curvature changes with modern SCL materials and years of SCL wear. However, further studies with longer lens deprivation periods are required to ensure stability for all SCL wearing patients.     

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

PurposeTo 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.MethodsParticipants, 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.ResultsOf 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.ConclusionsDisinfection 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.     

The use of fluorescein in contact lens aftercare

This short communication reports on the responses of a cohort of more than 2000 contact lens practitioners across five European countries, who were surveyed on the routine use of flourescein in soft contact lens aftercare. Although corneal staining has received extensive interest amongst the academic community, most practitioners do not routinely use fluorescein at aftercare visits. The arguments for not using the agent seem to be somewhat flawed in modern contact lens practice and it is hoped by education and wider communications of the value of staining that more practitioners use it more often.     

Biometric factors and orthokeratology lens parameters can influence the treatment zone diameter on corneal topography in Corneal Refractive Therapy lens wearers

PurposeTo investigate the relationship between patients’ baseline biometric factors or lens parameters and the diameter of the treatment zone in young myopic children undergoing Corneal Refractive Therapy.MethodsThe data of patients undergoing Corneal Refractive Therapy lens treatment within two years were retrospectively reviewed. Baseline clinical data, including sex, age, refractive power, corneal topography readings, ocular optical biometric measurements, and Corneal Refractive Therapy lens parameters, were subjected to Pearson, Spearman, and partial correlation analyses to identify the potential factors that may influence treatment zone diameter on corneal topography. Logistic and linear regression analyses were used to predict the treatment zone size.ResultsThe Right eyes of 309 patients were included in this study. The spherical refraction, flat keratometric reading, Reverse Zone Depth 2, Landing Zone Angle 1, and lens diameter were independent factors of treatment zone diameter. In the multivariate analyses, Landing Zone Angle 1 was positively correlated, while Reverse Zone Depth 2 and lens diameter were negatively correlated with the size of the treatment area. The accuracy of logistic regression in predicting the treatment zone size was 71.5%.ConclusionAdjustments to Corneal Refractive Therapy lens parameters may influence the treatment zone diameter on corneal topography. A higher Reverse Zone Depth 2, smaller Landing Zone Angle 1, and larger lens diameter can lead to a smaller treatment zone for Corneal Refractive Therapy lens treatment.     

The temporal dynamics of miniscleral contact lenses: Central corneal clearance and centration

Purpose

To examine the time course of the reduction in central corneal clearance and horizontal and vertical lens translation (decentration) during miniscleral contact lens wear and the theoretical influence upon the optics of the post-lens tear layer.

Corneal epithelial thickness and corneal curvature changes during the day: The effects of daily disposable contact lens wear

PurposeTo evaluate the changes in corneal epithelial thickness and corneal anterior and posterior curvatures during the day, and the effect of wearing daily disposable soft contact lenses.MethodsThirty-two healthy volunteers were enrolled in a randomized crossover study. At the baseline visit, corneal and epithelial thickness maps (OCT; Optovue, Inc., Fremont, CA, USA) and keratometric measurements (Pentacam, Oculus, GmbH, Germany) were performed in the morning and in the afternoon (8 hours after). Then, each subject was fitted with the following brands of daily disposable contact lenses in random order: Dailies Total 1 (Delefilcon A), Dailies Aqua Comfort (Nelfilcon A), TruEye (Narafilcon A) and Biotrue Oneday (Nesofilcon A) on different days. All fitted lenses had a power of −3.00 diopters (D). Measurements were repeated before putting the contact lens on and after an-eight-hour contact lens wear.ResultsWith no lens wear, the anterior topographic indices showed significant steepening [Kflat: p < 0.0001; Ksteep: p < 0.0001 and maximum keratometry value (Kmax): p = 0.04] and the corneal thickness significantly decreased in the central and temporal portion of the cornea in the afternoon. There were no significant changes in the posterior topographical indices and corneal epithelial thickness. With contact lens wear, no significant change occurred in the corneal and epithelial thickness, and the anterior and posterior curvatures during the day (all p values >0.05). There was no statistically significant difference in the epithelial thickness among the groups wearing different contact lens types (p > 0.05).ConclusionsAnterior corneal topographic indices steepen depending on the natural diurnal variations. Daily wear of soft contact lenses appears to mask this steepening. The corneal epithelial thickness is not affected by daily disposable soft contact lenses.     

The efficacy of povidone-iodine,hydrogen peroxide and a chemical multipurpose contact lens care system against Pseudomonas aeruginosa on various lens case surfaces

PurposeTo determine the antimicrobial efficacy of a povidone-iodine system (PVP-I; cleadew, OPHTECS Corporation, Kobe, Japan), a peroxide system (AOSEPT Plus with HydraGlyde, Alcon, Fort Worth, TX), and a chemical multipurpose system (renu fresh, Bausch & Lomb, Rochester, NY) on contact lens case surfaces that are both in contact and not in contact with the solutions during lens disinfection.MethodsThe surfaces of the inner walls, underside of the lid, and lens holder (if applicable) of the cases were inoculated with P. aeruginosa ATCC 27853. The cases were disinfected with the solutions as per their manufacturer instructions. After disinfection, the inoculated surfaces were swabbed and the amount of surviving P. aeruginosa was determined. Following this experiment, separate cases were inoculated and disinfected as before. This time the cases were agitated after recommended disinfection time and the amount of P. aeruginosa in the disinfecting solution was quantified immediately, and again after resting for 7 days. Experiments were conducted in triplicate (n = 3).ResultsUnits are expressed in log CFU. All three solutions significantly reduced P. aeruginosa on direct-contact surfaces (all p < 0.039). On non-contact surfaces, the reduction of P. aeruginosa in the PVP-I system (pre-disinfection: 6.8 ± 0.5, post-disinfection: 1.0 ± 0.0; p < 0.001) was significant, but not for the hydrogen peroxide system (pre-disinfection: 6.3 ± 0.6, post: 5.5 ± 0.5; p = 0.194) and the chemical multipurpose system (pre-disinfection: 6.6 ± 0.1, post-disinfection: 5.6 ± 0.8; p = 0.336). After 7 days post-disinfection, no P. aeruginosa regrowth was observed in the PVP-I system (Day 1: 1.0 ± 0.0, Day 7: 1.0 ± 0.0; p = 1) and the chemical multipurpose system (Day 1: 4.2 ± 0.2, Day 7: 1.8 ± 0.9; p = 0.012), however regrowth was observed in the hydrogen peroxide system (Day 1: 3.4 ± 0.6, Day 7: 6.1 ± 0.4; p = 0.003).ConclusionThe PVP-I system was more effective against P. aeruginosa on non-contact surfaces than the hydrogen peroxide system or the chemical multipurpose system and is capable of inhibiting regrowth of P. aeruginosa for at least 7 days post-disinfection.     

Discontinuation of long term orthokeratology lens wear and subsequent refractive surgery outcome

Purpose

To report a case of lens discontinuation in a long term orthokeratology (OK) lens wearer and describe regression in refraction, corneal topography, and corneal thickness over 408 days after lens discontinuation. Furthermore, the outcome of subsequent LASIK treatment is also reported.

The significance of hand wash compliance on the transfer of dermal lipids in contact lens wear

Aim

The aim of this study was to assess the impact of hand washing regimes on lipid transference to contact lenses. The presence of lipids on contact lenses can affect visual acuity and enhance spoilation. Additionally, they may even mediate and foster microbial transfer and serve as a marker of potential dermal contamination.

Methods and materials

A social hand wash and the Royal College of Nursing (RCN) hand wash were investigated. A ‘no-wash regime’ was used as control. The transfer of lipids from the hand was assessed by Thin Layer Chromatography (TLC). Lipid transference to the contact lenses was studied through fluorescence spectroscopy (FS).

Results

Iodine staining, for presence of lipids, on TLC plates indicated the ‘no-wash regime’ score averaged at 3.4 ± 0.8, the social wash averaged at 2.2 ± 0.9 and the RCN averaged at 1.2 ± 0.3 on a scale of 1-4. The FS of lipids on contact lenses for ‘no washing’ presented an average of 28.47 ± 10.54 fluorescence units (FU), the social wash presented an average of 13.52 ± 11.12 FU and the RCN wash presented a much lower average 6.47 ± 4.26 FU.

Conclusions

This work demonstrates how the method used for washing the hands can affect the concentration of lipids, and the transfer of these lipids onto contact lenses. A regime of hand washing for contact lens users should be standardised to help reduce potentially transferable species present on the hands.     

On-eye breakage and recovery of mini-scleral contact lens without compromise for the ocular surface

Purpose

To report the on-eye breakage of a mini-scleral contact lens in a healthy cornea after being hit by a speeding object, without causing any severe corneal damage.

30 years of contact lens prescribing for keratoconic patients in Turkey

Purpose

To assess retrospectively the course, the rate of bilateralness, prognosis, visual acuity with contact lenses, and corneal changes of a cohort with keratoconus.

Methods

Patients applying to Istanbul Faculty of Medicine, Department of Ophthalmology, Contact Lens Division during the period 1975-2005 with the diagnosis of keratoconus were recruited. The follow-up time ranged from 1.5 years to 25 years. This cohort consisted of 273 male, 245 female patients. The patients’ ages ranged from 12 years to 54 years (mean age 34.8 ± 10.1 years). 518 cases’ 1004 eyes were divided into four groups according to their mean keratometry values. The changes in visual acuity, keratometry values and the measurements of the used contact lenses were compared with each other, and statistical significance was sought.

Results

By self-report, the mean starting age of keratoconus was found to be 22.5 ± 7.6 years (range 7-35 years). 59 (11.4%) of 518 patients had unilateral keratoconus occurrence. The acute hydrops rate was found to be 0.3% (5 patients). In patients with advanced keratoconus, new contact lenses were applied with steeper radius of curvature. Penetrating keratoplasty was applied to 15 eyes (1.5%). Visual acuity examination on the patients’ last visit, when compared to previous examinations, was found to have decreased by 2-3 Snellen lines due to advancing keratoconus.

Conclusion

Keratoconus has shown to be a self-limited disease and in our study, with the use of contact lenses, successful outcomes which delayed the need for surgery were achieved in 98.9% of eyes (989/1004 eyes).     

Osmolality and pH of commercially available contact lens care solutions and eye drops

PurposeThe physical properties of contact lens care solutions and Eye Drops (ED) may affect initial comfort and dry eye symptomatology in contact lens wearers, although these properties are not always provided by manufacturers. The present study aimed to measure and compare the osmolality and pH of commercially available contact lens care solutions and ED.MethodsForty-four solutions were tested (17 lens care solutions and 27 ED) and classified by the presence and/or combination of the viscosity/lubrication-enhancing ingredients. Solution osmolality was obtained with the Fiske 110 osmometer and pH was measured with a micro-pH 2000. Each measurement was taken ten times, following the manufacturer's instructions, while controlling for room temperature and humidity. Differences between the values of the physical properties of the solutions were analysed by type and viscosity/lubrication-enhancing agent subclassification.ResultsOsmolality ranged from 192.6 ± 2.17 to 364.6 ± 2.88 mOsm/Kg, while pH ranged from 6.35 [6.35–6.26] to 7.99 [7.99–8.00]. A significant difference in the osmolality and pH values of contact lens care solutions and ED was found when classified by type or viscosity/lubrication-enhancing agent (ANOVA and Kruskal-Wallis respectively, both p < 0.001).ConclusionsThe physical properties of some contact lens care solutions and ED are not readily available. The osmolality and pH values of various commercially available lens care solutions and ED vary significantly both by type and viscosity/lubrication-enhancing ingredients.     

Chemical performance of multi‐environment trials in lens (Lens culinaris M.)

BACKGROUND: Genotype–environment (GE) interaction has been a major effect to determine stable lens (Lens culinaris (Medik.) Merr.) cultivars for chemical composition in Turkey. Utilization of the lines depends on their agronomic traits and stability of the chemical composition in diverse environments. The objectives of this study were: (i) to evaluate the influence of year and location on the chemical composition of lens genotypes; and (ii) to determine which cultivar is the most stable. Genotypes were evaluated over 3 years (2005, 2006 and 2007) at four locations in Turkey. Effects of year had the largest impact on all protein contents. RESULTS: GE interaction was analyzed by using linear regression techniques. Stability was estimated using the Eberhart and Russell method. ‘K??l?k K?rm?z?51’ was the most stable cultivar for grain yield. The highest protein was obtained from ‘K??l?k K?rm?z?51’ (4.6%) across environments. According to stability analysis, ‘F?rat 87’ had the most stable chemical composition. This genotype had a regression coefficient (b_i = 1) around unity, and deviations from regression values (δ_ij = 0) around zero. CONCLUSION: Chemical composition was affected by year in this study. Temperature might have an effect on protein, oil, carbohydrate, fibre and ash. F?rat 87 could be recommended for favourable environments. Copyright © 2009 Society of Chemical Industry     

The time course and nature of corneal oedema during sealed miniscleral contact lens wear

PurposeTo examine the magnitude and time course of central epithelial, stromal and total corneal thickness changes during sealed miniscleral contact lens wear and the influence of initial central corneal clearance upon these thickness changes.MethodsHigh-resolution OCT images were captured over an 8 h period of miniscleral contact lens wear (using a rotationally symmetric 16.5 mm diameter lens) in 15 young, healthy participants with normal corneae. Corneal thickness data were derived from OCT images using semi-automated image processing techniques over the central 4 mm.ResultsChanges in stromal and total corneal thickness followed a similar pattern throughout lens wear with oedema first detected 15 min after lens insertion (0.47 ± 0.09% increase in stromal and total corneal thickness, both p < 0.01) which peaked after 90 min of lens wear (1.36 ± 0.24% increase in stromal and 1.18 ± 0.20% increase in total corneal thickness, both p < 0.01) and gradually decreased thereafter. Epithelial thickness increased slightly during the first 30 min of lens wear (0.56 ± 0.30% increase, p > 0.05), then rapidly decreased reaching a minimum thickness 480 min after lens insertion (2.38 ± 0.70% decrease, p < 0.05). The maximum total corneal oedema, maximum stromal oedema, and maximum epithelial thinning were not associated with the initial central corneal clearance or the extent of lens settling over the 8 h period (all p > 0.05). Greater initial central corneal clearance resulted in less oxygen concentration reaching the cornea (∼2% less) based on previously published data, which manifested as ∼0.5% more central corneal oedema.ConclusionsScleral lens induced corneal oedema is stromal in nature. On average, central stromal and total corneal thickness increased rapidly following lens insertion and peaked after 90 min, while central epithelial thickness gradually decreased throughout lens wear consistent with natural diurnal variation. A greater initial central corneal clearance resulted in reduced oxygen delivery to the cornea, which had minimal short-term impact upon healthy eyes, however, minimising central corneal clearance may be important in eyes with reduced endothelial cell function to minimise hypoxic stress.