Conjunctival prolapse during open eye scleral lens wear

PurposeTo investigate the incidence and peak elevation of conjunctival prolapse during short-term open eye scleral lens wear and its association with lens fitting characteristics.MethodsTen young, healthy adults (mean age ± SD, 30 ± 4 years) wore a high Dk sealed scleral lens for 90 min with an initial central post-lens fluid reservoir thickness defined as low (144 ± 23 μm), medium (487 ± 63 μm), and high (726 ± 55 μm). Optical coherence tomography was used to quantify limbal clearance, lens settling, and changes in conjunctival thickness.ResultsThe incidence of conjunctival prolapse was 37% across all fluid reservoir thickness conditions, with 80% of participants exhibiting conjunctival prolapse at least once. Prolapse was observed more frequently nasally (73%) than temporally (27%) (p < 0.01). The peak prolapse elevation did not vary with fluid reservoir thickness condition or anatomical location (both p > 0.05). For the low fluid reservoir thickness condition, eyes with conjunctival prolapse had greater initial limbal clearance (97 ± 38 μm compared to 43 ± 34 μm, p = 0.01) and more settling after 90 min of lens wear (−85 ± 30 μm compared to −34 ± 29 μm, p < 0.01). Greater limbal settling was associated with a higher peak elevation of the conjunctival prolapse (r = 0.48, p = 0.02), but not with landing zone tissue compression (r = 0.22, p = 0.33) or the initial or final limbal fluid reservoir thickness asymmetry (r ≤ 0.07, p > 0.05).ConclusionConjunctival prolapse was commonly observed during short-term sealed scleral lens wear in healthy eyes. The peak elevation of the conjunctival prolapse was associated with the extent of limbal settling, but not landing zone tissue compression or fluid reservoir thickness asymmetry.     

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.     

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.     

Anterior eye surface changes following miniscleral contact lens wear

PurposeTo quantify the effect of short-term miniscleral contact lens wear on the anterior eye surface of healthy eyes, including cornea, corneo-scleral junction and sclero-conjuctival area.MethodsTwelve healthy subjects (29.9 ± 5.7 years) wore a highly gas-permeable miniscleral contact lens of 16.5 mm diameter during a 5-hour period. Corneo-scleral height profilometry was captured before, immediately following lens removal and 3 h after lens removal. Topography based corneo-scleral limbal radius estimates were derived from height measurements. In addition, elevation differences in corneal and scleral region were calculated with custom-written software. Sclero-conjuctival flattening within different sectors was analysed.ResultsShort-term miniscleral lens wear significantly modifies the anterior eye surface. Significant limbal radius increment (mean ± standard deviation) of 146 ± 80 μm, (p = 0.004) and flattening of −122 ± 90 μm in the sclero-conjuctival area, (p << 0.001) were observed immediately following lens removal. These changes did not recede to baseline levels 3 h after lens removal. The greatest anterior eye surface flattening was observed in the superior sector. No statistically significant corneal shape change was observed immediately following lens removal or during the recovery period.ConclusionsShort-term miniscleral contact lens wear in healthy eyes does not produce significant corneal shape changes measured with profilometry but alters sclero-conjuctival topography. In addition, sclero-conjuctival flattening was not uniformly distributed across the anterior eye.     

A one-year prospective study on scleral lens wear success

PurposeTo report the success rate of scleral lens wear and the lens handling learning curve from the wearers perspective.MethodsNinety-five participants were consecutively screened for enrollment in a prospective study. Participants were divided into two groups: ICGroup (71 participants with irregular corneas) and RCGroup (24 participants with regular corneas). Participants attended several visits: Baseline, Lens Dispense Visit (LDV), 1-month, 3-month, 6-month and 12-month follow-ups. The number and causes of scleral lens discontinuation and the time to correctly apply the lens for the first time at the LDV were evaluated. During follow-ups, participants answered a questionnaire regarding scleral lens wear (mean number of hours/day and days/week of lens wear, methods used for handling, number of attempts to correctly apply and remove the lenses).ResultsSixty-nine participants (73 %) successfully completed the 12-month period. Twenty-six participants (27 %) discontinued scleral lens wear. None of the discontinuations were due to adverse events. The success rate (number of participants that wore the lenses for the 12 months) was 77 % in ICGroup and 58 % in RCGroup. The main reasons for scleral lens discontinuation were handling issues (35 %) and discomfort (19 %). 36 % of participants required <15 min to correctly apply the lens at the LDV, however 13 % required >60 min (participants that wore spectacles, soft lenses or had no correction method at Baseline). The mean wearing time (hours/day and days/week) increased significantly from 1-month to 12-month appointments: from 9.8–11.1 h and 5.1–5.6 days in new scleral lens wearers, while the number of attempts to correctly apply and remove the lenses decreased significantly.ConclusionsThe success rate was 73 % during this prospective 12-month follow-up study. The main reasons for drop-out were handling issues and discomfort. Participants who continued scleral lens demonstrated increased handling skills.     

Relationship of placido corneal topography data with scleral lens fitting parameters

PurposeTo analyze the relationship between corneal sagittal height and asymmetry parameters derived from Placido-videokeratoscopy with the parameters of fitted scleral lenses (ScCLs).MethodsCorneal topographies were measured with MedmontE300 in a total of 126 eyes with irregular and regular corneas before ScCL fitting were analyzed. Measurements of sagittal height (OC-SAG) at steep and flat corneal meridians were obtained for 10 mm and 12 mm chords. Estimated Height (EHChord) parameters were taken for a chord equal to the diameter of the lens that each subject was wearing at different semi-meridians. Corneal asymmetry (difference in OC-SAG between steep and flat corneal meridians) was also assessed. These outcomes were correlated to ScCL parameters that subjects were wearing after 1 month.ResultsThe mean ScCL-SAG was 4696 ± 240 μm, and the mean OC-SAG ranged from 1891 μm (10 mm), 2914 μm (12 mm), and between 4162 μm and 4251 μm for EH0-180º and EH30-210º. Stronger correlations (p < 0.001) between OC-SAG and ScCL-SAG were determined for EH0-180º (r = 0.595) and EH30-210º (r = 0.618). The mean differences between OC-SAG and ScCL-SAG were between 447 ± 290 μm (EH0-180º) and 389 ± 360 μm (EH30-210º). There was no relationship between corneal asymmetry and the need to fit a ScCL with toric haptic design in irregular corneas. Orientation of flat corneal and scleral meridians were similar only in corneas with high regular astigmatism.ConclusionsEHChord attributes were the parameters that best correlated with the ScCL-SAG. The corneal asymmetry was shown to be a poor predictor for the need to fit a ScCL with toricity at landing zone in irregular corneas, but could have some predictive power in regular corneas.     

Corneal surface wettability and tear film stability before and after scleral lens wear

PurposeThe aim of this study was to evaluate the anterior surface of scleral contact lens and ocular surface wettability before and after one-month of scleral lens wear in patients with keratoconus.MethodsForty-nine patients with keratoconus (36.26 ± 9.03 years) were recruited. The sample was divided into two groups: patients with intrastromal corneal ring (KCICRS group) and patients without ICRS (KC group). TFSQ, Schirmer I test, Ocular Surface Disease Index (OSDI questionnaire), tear break-up time (TBUT) and corneal staining were evaluated in two different visits: Baseline (before lens wear) and one-month visit (10 min after lens removal). Visual Analog Scale (VAS questionnaire) was filled in just after inserting the lenses and just before removing them. TFSQ mean and inferior were evaluated over the contact lens surface at the moment of inserting the lens (baseline visit) and after 8 h of lens wear (one-month visit).ResultsAnterior corneal surface TFSQ values increased in all groups after scleral lens wear (p < 0.05). However, there were no statistical differences found at the moment of inserting or after 8 h of lens wear on previous contact lens surface TFSQ (p > 0.05). No changes were found in tear volume for total and in KC and KCICRS groups (p > 0.05). For all groups, there was a statistical decrease of TBUT (p < 0.05). In addition, OSDI score, corneal staining and VAS score improved after scleral lens wear from baseline in total and in both KC and KCICRS groups (p < 0.05).ConclusionThe scleral contact lens surface keeps its wettability after one-month of wear. However, the wettability of the ocular surface is worse after contact lens wearing.     

Scleral contact lens thickness profiles: The relationship between average and centre lens thickness

PurposeTo develop a methodology to reliably determine the thickness profile of scleral contact lenses and examine the relationship between the centre and average lens thickness for a range of lens designs and back vertex powers.MethodsHigh-resolution images of 37 scleral trial lenses (Epicon LC, Rose K2 XL and ICD 16.5) were captured using an optical coherence tomographer, and their thickness profiles were generated after correcting for known measurement artefacts. Centre lens thickness values were compared with manual lens gauge measurements, and repeatability was assessed by comparing average thickness values derived from orthogonal meridians of each lens.ResultsThe imaging technique displayed a high level of agreement with a manual lens gauge for centre thickness measurements; mean difference 5 ± 9 μm (95% LoA −14 to +23 μm), and a very high level of repeatability; mean difference between orthogonal meridians 1 ± 3 μm (95% LoA −6 to +8 μm). Lens thickness profiles varied between lens designs, with distance from the lens centre, and with back vertex power. Increasing back vertex powers resulted in a significant over or underestimation (up to 33% for high minus powers) of the average lens thickness based on the centre lens thickness.ConclusionsThe thickness of scleral contact lenses varies with distance from the lens centre and the back vertex power. The average lens thickness value derived from the entire lens provides a more appropriate representation of the true lens thickness and should be used in the calculation of scleral lens oxygen transmissibility.     

Case series: Extended wear of rigid gas permeable scleral contact lenses for the treatment of persistent corneal epithelial defects

ObjectivesTo report the successful treatment of persistent corneal epithelial defects that failed to respond to alternative treatment methods using extended wear of three different rigid gas-permeable scleral lenses.MethodsEight eyes of eight patients with persistent corneal epithelial defects were treated with Blanchard Onefit 2.0 Scleral lens, BostonSight Scleral lens, and BostonSight PROSE device and were observed for defect resolution and improvement in best-corrected visual acuity over the duration of treatment.ResultsAll eyes observed complete re-epithelialization with a mean time of 11.1 ± 5.5 days. At the conclusion of the treatment, visual acuity improved in all but one patient. No complications were observed during treatment.ConclusionsScleral lenses provide the corneal epithelium with hydration, oxygen permeation, and protection from mechanical forces; thereby facilitating healing of persistent corneal epithelial defects. This case series demonstrates the successful use of continuous wear scleral lenses in a number of patients for the treatment of persistent epithelial defects refractory to other interventions.     

Scleral lens wear: Measuring inflammation in the fluid reservoir

PurposeTo measure inflammatory mediators in the scleral lens fluid reservoir (FR) in healthy eyes and to compare them to basal tear samples after 8-hs (8h) and 4-days (4d) of scleral lens (SL) wear.MethodsFifteen normal, habitual soft contact lens wearers were fitted with 14.8- or 15.4-mm SLs (Zenlens, Alden Optical, USA). Basal ocular surface tears and FR samples were collected after 8h and 4d of daily SL wear. Levels of interleukin (IL) -4 and -8, matrix metalloproteinase (MMP)-7, -9, and -10, and tissue inhibitor of MMPs (TIMPs) 1–4 were measured in all samples using Luminex assays. Visual acuity, corneal and conjunctival staining, and comfort assessments were completed at the baseline, 8h and 4d time points.ResultsMMP-9 and MMP-10 were greater in FR than basal ocular surface tears. After 8h of SL wear, the median concentration of MMP-9 in the FR and basal tears were 62.7 and 15.2 ng/mL, respectively (p = 0.047). Likewise, MMP-10 was significantly greater in FR compared to basal tears, after 8h (25.8 ng/mL vs 2.8 ng/mL, p < 0.001) and 4d (2.1 ng/mL vs17.2 ng/mL, p = 0.047). IL-4 and IL-8 levels were greater in FR but not significantly at 8h (2.2 vs 3.1 ng/mL; and 0.1 vs 0.4 ng/mL, respectively) or 4d (0.9 vs 3.5 ng/mL; 0.0 vs 0.2 ng/mL). MMP-7 was not affected by SL wear after 8h (46.0 basal vs 54.4 ng/mL FR) or 4d (34.2 vs 87.5 ng/mL). Visual acuity, corneal and conjunctival staining did not change; comfort was reduced in SL compared to soft contact lens wear.ConclusionsThis is the first study to compare the FR with the basal ocular surface tears. MMP-9 and MMP-10 were elevated in the FR after several hours of SL wear, suggesting potential clinical implications of SL wear and deserves further investigation.     

Transient corneal epithelial bullae associated with large diameter scleral lens wear: A case series

With the increased fitting of scleral lenses by eye care practitioners, complications with lens wear need to be considered. Several prior studies have addressed complications specific to scleral lens wear and the incidence of hypoxia with extended wear, but few report the presence of epithelial bullae. This case series investigates three patients with differing ocular surface diseases, yet all developed transient epithelial bullae with concurrent large diameter scleral lens wear. These bullae appear to form due to weakened connections in the corneal epithelium at the level of basement membrane and Bowman’s layer and flatten within minutes of lens removal. These bullae need to be further studied, as they can increase the patient’s risk of epithelial defects, infections, and other complications in already compromised corneas.     

Anatomical and physiological considerations in scleral lens wear: Conjunctiva and sclera

While scleral lenses have been fitted using diagnostic lenses or impression moulding techniques for over a century, recent advances in anterior segment imaging such as optical coherence tomography and corneo-scleral profilometry have significantly improved the current understanding of the anatomy of the anterior eye including the morphometry of the conjunctiva, sclera, and corneo-scleral junction, as well as the ocular surface shape and elevation. These technological advances in ocular imaging along with continual improvements and innovations in scleral lens design and manufacturing have led to a global increase in scleral lens prescribing. This review provides a comprehensive overview of the conjunctiva and sclera in the context of modern scleral lens practice, including anatomical variations in healthy and diseased eyes, the physiological impact of scleral lens wear, potential fitting challenges, and current approaches to lens modifications in order to minimise lens-induced complications and adverse ocular effects. Specific topics requiring further research are also discussed.     

Anatomical and physiological considerations in scleral lens wear: Intraocular pressure

Intraocular pressure (IOP) is maintained through complex and interrelated systems which control aqueous production and drainage, and it has been suggested that scleral lens (SL) wear may disrupt these vital homeostatic processes. This review provides an overview of anatomical and physiological processes that control IOP, identifies potential effects of SLs on these regulatory mechanisms, and examines studies that have attempted to quantify the effect of SLs on IOP. Lack of access to the cornea during SL wear makes accurate assessment of IOP challenging; therefore, a range of different assessment techniques and instruments have been employed to quantify IOP during and following SL wear. Some studies have evaluated IOP using standard techniques prior to lens application and following lens removal, or through a large central fenestration. Other studies have utilised instruments that facilitate assessment of IOP on the peripheral cornea or conjunctiva overlying the sclera (e.g. Schiotz, transpalpebral, and pneumatonometry). Two studies have recently evaluated changes in optic nerve structure during SL wear. Conflicting results have been reported on this topic, much of which examines changes in IOP in healthy subjects over limited periods of time. Currently, only a few studies have reported on long-term effects of SL wear on IOP in habitual SL wearers (after lens removal). Future research in this area must not only consider the fact that ocular conditions treated with SLs may potentially alter corneal biomechanical properties which can influence IOP, but also that these properties may be further altered by SL wear. Monitoring other risk factors for glaucoma (permanent alterations in optic nerve physiology, visual field defects) could provide a more comprehensive assessment of potentially increased risk of glaucomatous optic neuropathy due to SL wear. Ongoing clinical assessment of optic nerve structure and function is advisable in patients at risk for glaucoma who require SLs.     

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 impact of short-term fenestrated scleral lens wear on intraocular pressure

PurposeTo examine the influence of short-term fenestrated scleral lens wear on intraocular pressure (IOP) in healthy eyes.MethodsIOP was measured before, during, and after a brief period (1–2 min) of fenestrated, scleral lens wear, using a rebound tonometer, in fifty, young healthy adults (mean age 23 ± 4 years) with normal corneas.ResultsImmediately following lens insertion, 48 of the 50 (96 %) of participants displayed an increase in IOP (mean ± SD increase in these participants of 3.8 ± 2.0 mmHg). Immediately following lens removal, 50 % of participants displayed a reduction in IOP, equal to or lower than, the pre-insertion IOP (-1.0 ± 0.8 mmHg lower than baseline). The remaining 50 % of participants displayed an IOP slightly greater than the pre-insertion IOP (1.6 ± 1.0 mmHg greater) after lens removal.ConclusionsShort-term fenestrated scleral lens wear resulted in a small, but statistically significant, increase in IOP in 96 % of young healthy participants (< 4 mmHg on average), which decreased to a level similar to pre-lens insertion IOP levels immediately following lens removal. Further research is required to determine if this measured change in IOP during scleral lens wear is artefactual, or an elevation in the true IOP.     

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.     

Central-to-peripheral corneal edema during wear of embedded-component contact lenses

PurposeWith active investigation underway for embedded-circuit contact lenses, safe oxygen supply of these novel lenses remains a question. Central-to-peripheral corneal edema for healthy eyes during wear of soft contact (SCL) and scleral lenses (SL) with embedding components is assessed.MethodsVarious 2-dimensional (2D) designs of SL and SCL with embedded components are constructed on Comsol Multiphysics 5.5. Local corneal swelling associated with the designed lenses is determined by a recently developed 2D metabolic-swelling model. Settled central post-lens tear-film thicknesses (PoLTFs) are set at 400 μm and 3 μm for SL and SCL designs, respectively. Each lens design has an axisymmetric central and an axisymmetric peripheral embedment. Oxygen permeability (Dk) of the lens and the embedments ranges from 0 to 200 Barrer. Dimensions and location of the embedments are varied to assess optimal-design configurations to minimize central-to-peripheral corneal edema.ResultsBy adjusting oxygen Dk of the central embedment, the peripheral embedment, or the lens matrix polymer, corneal swelling is reduced by up to 2.5 %, 1.5 %, or 1.4 % of the baseline corneal thickness, respectively, while keeping all other parameters constant. A decrease in PoLTF thickness from 400 μm to 3 μm decreases corneal edema by up to 1.8 % of the baseline corneal thickness. Shifting the peripheral embedment farther out towards the periphery and towards the anterior lens surface reduces peak edema by up to 1.3 % and 0.6 % of the baseline corneal thickness, respectively.ConclusionsTo minimize central-to-peripheral corneal edema, embedments should be placed anteriorly and far into the periphery to allow maximal limbal metabolic support and oxygen transport in the polar direction (i.e., the θ-direction in spherical coordinates). High-oxygen transmissibility for all components and thinner PoLTF thickness are recommended to minimize corneal edema. Depending on design specifications, less than 1 % swelling over the entire cornea is achievable even with oxygen-impermeable embedments.