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.     

Intraepithelial corneal haemorrhage in a rigid contact lens wearer

Intracorneal haemorrhage is a rare complication of modern contact lens wear. While a limited number of reports have described intracorneal haemorrhages (typically stromal) associated with the extended wear of soft contact lenses with limited oxygen permeability for the correction of aphakia, this case report documents the management and resolution of a significant intraepithelial corneal haemorrhage associated with long-term rigid contact lens wear for keratoconus and high myopia.     

Investigation of posterior corneal curvature in CL-induced corneal swelling

Purpose

To evaluate Orbscan II measurements without contact lens (CL) removal to monitor in vivo posterior corneal curvature in CL (hypoxia)-induced corneal swelling during extended wear (EW).

Methods

Orbscan II corneal topographer was used to measure posterior corneal curvature 1 week before CL wearing and during 1 week of EW. Central corneal thickness (CCT) was also measured during the 2-week study with OCT to determine the corneal swelling percentage. High Dk (lotrafilcon A) and low Dk (etafilcon A) soft CL were randomly fitted in EW in the right and left eyes of 20 subjects with normal ocular health. Orbscan and OCT were also performed without CL removal after 3 and 7 days of wear.

Results

Low Dk lenses induced significantly higher corneal swelling (2.41 ± 2.65%), as compared to the high Dk lenses (0.17 ± 2.28%; P < 0.05 repeated measures ANOVA (Re-ANOVA and paired t-test) measures with OCT. The low Dk lens induced a significantly posterior corneal flattening compared to the high Dk lens (0.036 ± 0.06 mm versus 0.006 ± 0.04 mm; P < 0.05 Re-ANOVA and paired t-test). High repeatability for Orbscan-measured posterior best fit sphere (BFS) radii with (r² = 0.15, 95% limits of agreement (LoA) = 0.10 to −0.06) and without (r² = 0.00, 95% LoA = 0.08 to −0.08) CL removal was also observed and suggest that posterior corneal changes was not due to Orbscan variability.

Conclusions

Orbscan is a non-invasive and reproducible technique to evaluate and monitoring posterior corneal curvature in vivo in CL (hypoxia)-induced corneal swelling during EW.     

Soft contact lens fitting after intrastromal corneal ring segment implantation to treat keratoconus

PurposeTo assess the feasibility of fitting a lathed soft toric contact lens (STCL) after the implant of intrastromal corneal ring segments (ICRSs) to treat keratoconus.MethodsSix months after ICRS implantation, 47 eyes of 47 patients (18–45 years) were fitted with a STCL. In each eye, we determined refractive error, uncorrected (UDVA) and corrected distance visual acuity (CDVA), and keratometry and asphericity measures. The outcome of STCL fitting was defined according to CDVA as successful (≤0.2 logMAR) or unsuccessful (>0.2 logMAR). Patients in the unsuccessful group were refitted with a piggy-back (PB) system. The above variables and the change in CDVA observed after STCL and PB lens fitting from spectacle CDVA were compared in the two groups.ResultsSTCL fitting was successful in 75%, 66.66% and 0% of the ICRS implanted eyes with stages I–III keratoconus, respectively. Spectacle-CDVA was 1.5 lines better and mean corneal power was 3.62D lower in the successful STCL group. In this group, the difference in cylinder axis between spectacles and STCL was 24.25° lower. PB refitting achieved a PB-CDVA ≤0.2 logMAR in all cases. A similar difference in the CDVA change achieved by contact lenses versus spectacles was observed in the successful STCL and PB refitted groups.ConclusionSTCL fitting is a feasible option in a large proportion of patients implanted with ICRS. When these lenses are unsatisfactory, a PB system is a good alternative.     

The 75th anniversary of the Tuohy corneal contact lens: A review

The aim of this review is to mark the 75th anniversary of the introduction of the original corneal contact lens of Tuohy in 1948.American documents in the public domain, such as census records and draft registration cards, were consulted in order to provide a more comprehensive biography of Kevin M Tuohy, inventor of the corneal contact lens, than those previously published.Perhaps due to a failure to consult original sources concerning the Tuohy corneal lens, some historical accounts have provided incomplete or incorrect information about its design and dimensions. The back surface specification of the bi-curve Tuohy lens in its standard diameter of 11.50 mm has been tabulated and edge lift and edge clearance values calculated. A colour photograph illustrates the fluorescein pattern of a Tuohy lens.Patients wearing Tuohy lenses were able to achieve a much longer wearing time compared to those wearing sealed scleral lenses since they eliminated corneal epithelial oedema, a frequent problem which necessitated removal of lenses after a few hours of wear due to cloudy vision. Only some of Tuohy lens wearers exhibited an adverse corneal response such as fluorescein staining after 12, or more, hours of wear.The clinical success of the Tuohy lens and the fact that its fitting procedure was simpler and quicker than that for scleral lenses encouraged optometrists to commence contact lens practice and to implement improvements in the design of the corneal lens.     

Proteomic profiling of human corneal stroma from long-term contact lens wearers reveals activation of inflammatory responses

PurposeTo investigate the association between proteomic changes and potential pathogenesis in the human cornea with respect to the duration of wearing soft contact lenses (SCLs).MethodsA total of 96 corneal stroma samples, obtained via small incision lenticule extraction (SMILE), were equally grouped according to the duration of wearing SCL: 0Y, did not wear SCL; 5Y, wore SCL for<5 years; 5–10Y, wore SCL for 5–10 years; O10Y, wore SCL for>10 years. Liquid chromatography–tandem mass spectrometry was used to identify and quantify protein profiles in the corneal stroma. Expression levels of CO1A1, CO4A1, NFKB1, and IL6RB were determined using western blot and immunohistochemistry analysis.ResultsThis study quantified a total of 5,668 proteins across samples and identified 2,379 differentially expressed proteins (DEPs) with significantly increased abundance in the three SCL-wearing groups compared with that in the non-SCL-wearing group. Compared with those in the 0Y group, the molecular functions of DEPs in the 5Y, 5–10Y, and O10Y groups were mainly related to translation regulator activity, antigen binding, peptidase inhibitor activity, participation in extracellular matrix (ECM) production, complement activation, and inflammatory responses. Pathway enrichment analysis of DEPs showed that the sphingolipid, phosphatidylinositol 3-kinase-protein kinase B, and hypoxia-inducible factor-1 signaling pathways were activated in the human corneal stroma after long-term SCL use.ConclusionsInflammation-related proteomic components in human corneal stroma increased after long-term use of SCL and may act as an essential factor in the molecular pathogenesis of corneal stroma damage.     

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.     

Treatment of corneal dellen with a large diameter soft contact lens

A 58-year-old man presented with corneal dellen twelve days after pterygium removal on his left eye. Initial treatment with lubrication and artificial tears was unsuccessful. The fitting of a conventional contact lens was not possible because of conjuctival chemosis. Additionally the patient denied eye patching due to professional reasons. As an alternative treatment a large diameter bandage soft contact lens approved for extended wear was applied ((David Thomas Contact Lens T74/85 Extended Wear/Bandage of 18 mm diameter). The next day corneal dellen had already began to retreat and four days later the contact lens was removed since there was no sign of dellen in the slit lamp examination. In conclusion, the use of a large diameter soft contact lens was an effective alternative solution for the treatment of corneal dellen in our patient.     

Comparing sagittal heights calculated using corneal parameters and those measured with profilometry

PurposeTo compare the sagittal height of the anterior eye (OC-SAG) calculated using corneal parameters with the OC-SAG measured by profilometry.MethodSeventy right eyes of soft contact lens wearers measured with the ESP (Eaglet Eye, The Netherlands) after lens removal were retrospectively analyzed for this study. The OC-SAG of the eyes was calculated using mean k-values, eccentricity and the inner (corneal) radius obtained with the ESP for an 11-mm cord diameter. It was then extrapolated to chord diameters of 14, 14.5 and 15 mm. These values were compared with OC-SAG values obtained with the ESP for the same chord diameters. Additionally, the OC-SAG was calculated through the formula used by a lab that manufactures custom soft lenses (mark’ennovy, Madrid, Spain) and compared again with the values obtained using the ESP.ResultsDifferences between calculated OC-SAG obviating the shape factor were 121 ± 44, 155 ± 105, 172 ± 117 and 189 ± 129 µm for chord diameters of 11, 14, 14.5 and 15 mm, respectively (p < 0.001). When the shape factor was included in the calculation, differences were 28 ± 48, 62 ± 102, 79 ± 113 and 96 ± 123 µm (p < 0.001). When the inner best fit sphere was used to estimate OC-SAG, differences were 34 ± 11, 0 ± 72, 17 ± 86 and 34 ± 99, respectively, with no significant differences for the 14 and 14.5 mm-chord diameters (p = 0.99 and 0.11, respectively). Correlation coefficients between OC-SAG calculated and measured OC-SAG ranged from 0.53 to 0.90 depending on the chord diameter used. When the mark’ennovy formula was used to calculate the OC-SAG as the lens diameter proposed by the formula, the difference was −47 ± 147 µm (p < 0.01).ConclusionsDifferences between the OC-SAG calculated using corneal parameters and that measured with a profilometer are statistically and clinically significant, especially for large chord diameters. The impact of this on contact lens fitting should be addressed in future studies.     

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.     

Clinical comparison of optimum and large diameter soft contact lenses

Purpose

To compare the clinical performance of large diameter lenses with optimally fit lenses in the same material and monocurve back surface design.

Corneal stability after discontinued soft contact lens wear

PURPOSE: To determine the time needed to reach corneal stability after discontinued daily wear of soft contact lenses and to identify corneal topographic and pachymetric changes during this period. METHODS: We prospectively studied the eyes of 21 consecutive soft contact lens wearers evaluated for keratorefractive surgery. Each eye was examined once immediately after lens removal, 3 and 7 days later, and weekly thereafter. At each visit, manifest refraction, keratometry, corneal topography (EyeSys Corneal Analysis system, EyeSys Laboratories, Houston, TX) and pachymetry were performed. Incidence of associated corneal warpage and changes in corneal curvature and thickness during corneal stability time were determined. RESULTS: Of the 42 eyes examined, 26 corneas showed no significant change after the initial evaluation (stable group). The minimum stability time was 3 days in the remaining 16 eyes (unstable group), 7 of which had significant evidence of abnormal topography. Statistical analysis showed no significant differences between two groups regarding age, sex, duration of contact lens wear, and refractive and topographic measures. The mean central corneal thickness on the final visit was significantly different between two groups (P<0.05). CONCLUSION: Contact lens induced corneal warpage may occur in a considerable proportion of soft contact lens wearers. A 2-week contact lens free period seems to be adequate for the cornea to stabilize; however, one cannot predict the minimum time needed for each individual patient. Repeating examinations to document corneal stability before refractive surgery may be a safer alternative.     

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.     

Randomised controlled trial of corneal vs. scleral rigid gas permeable contact lenses for keratoconus and other ectatic corneal disorders

PurposeTo compare the comfort and visual performance of corneal rigid gas permeable contact lenses (CoL) and scleral rigid gas permeable contact lenses (SL) in participants with corneal ectasia, successfully wearing “habitual” CoL.MethodsIn a randomised controlled trial (RCT) with a 2 × 2 crossover, 34 participants were recruited and randomised into two groups. Group 1 (sequence AB), were fitted in period 1, with new CoL and after a 4-week washout period, in which habitual CoL were worn, were fitted with and crossed-over to SL, period 2. Group 2 (sequence BA), were first fitted with SL in period 1 and after a washout period of 4 weeks, crossed-over to new CoL, period 2. The median lengths in weeks of Periods 1 and 2 were: 17.5 (IQR 12.4) and 14.5 (IQR 6.2) respectively. The outcome measures for visual performance were best corrected visual acuity and the contrast sensitivity function. Vision related quality of life (Qol) was assessed using the National Eye Institute Visual Function Questioannaire-25 and reported subjective perception of vision (SPV) and reported subjective perception of comfort (SPC) scores, recorded on a scale from 1–10. The final outcome measure was the selection of the preferred lens type at the completion of the RCT.ResultsFor the 30 who completed the trial, significantly higher SPC scores were found for SL compared to CoL (p = 0.002). Significantly higher SPC scores for CoL were found in participants who selected CoL as their preferred lens for future use, compared to those who selected SL (p = 0.009). All other outcomes exhibited no significant difference between the experimental lenses. There was no significant difference (p=0.86) in the proportion preferring CoL (53%) and SL (47%).ConclusionSignificantly better comfort was reported for SL compared with CoL. Significantly higher comfort in CoL was found in those who preferred CoL, than those who preferred SL. Successful CoL wearers whose SPC in CoL is <7 are likely to achieve better comfort with SL. On average, successful CoL wearers found SL more comfortable and there are unlikely to be any significant visual or visual Qol advantage or disadvantage in refitting successful CoL wearers with keratoconus and other corneal ectasia disorders, with SL and vice versa.     

Effects of corneoscleral topography on soft contact lens performance: A pilot study

To quantify corneoscleral junction (CSJ) topography in soft contact lens (SCL) wearers, and assess the association between the CSJ and SCL performance and subjective comfort, forty-four adapted SCL wearers (16 Asians, 16 Caucasians, 12 Latinos) were recruited for the present study. Corneal topography was taken with a Medmont E300 (Medmont International, Pty Ltd.). CSJ images were taken with a commercial OCT (Bioptigen, Inc.). Our published CSJ image analysis technique was used to describe the geometric properties of the CSJ using the sum of squared orthogonalized residuals (SSRo). Multivariable mixed effects models were employed to examine associations between SSRo and subject demographics, ocular characteristics, SCL fit and performance, and comfort. The SSRo was significantly related to quadrant (p?<?0.001), ethnicity (p?=?0.014), and horizontal corneal shape factor (p?=?0.044). The nasal quadrant had the largest SSRo, indicating the steepest CSJ profile and/or the most irregular CSJ surface, followed by the inferior quadrant. The superior and temporal quadrants had the smallest SSRo, indicating relatively flat and even CSJ topography. Caucasians had the steepest and/or most irregular CSJ compared with Latinos and Asians. Less inferior-superior heterogeneity in the SSRo was associated with greater comfort after 6?h of lens wear. The SSRo was proved to be a useful tool to quantify CSJ geometry in SCL wearers. Significant differences in the SSRo were found among quadrants and ethnic groups. Better subjective comfort after 6?h of SCL wear was associated with a smaller difference in the SSRo between the superior and inferior quadrants.     

Patterns of fitting cosmetically tinted contact lenses

Cosmetically tinted soft contact lenses are an attractive option for contact lens wearers. Data that we have gathered from annual contact lens fitting surveys demonstrate that those wearing tinted lenses are more likely to be female (4.6% of all soft lenses fitted vs. 1.6% for males; p < 0.0001) and younger (27 ± 11 years vs. 33 ± 13 years for those wearing non-tinted lenses; p < 0.0001). Tinted lenses tend to be worn more on a part-time basis and are replaced less frequently than non-tinted lenses. The decline in fitting tinted lenses over the past 12 years may be due to (a) the current limited availability of tinted lenses in silicone hydrogel materials and daily disposable replacement frequencies, which together represent a significant majority (78%) of new soft lenses fits today, (b) growing concerns among lens wearers and practitioners relating to the risks of complications associated with the wearing of tinted lenses, and (c) reduced promotion of such lenses by the contact lens industry.     

Factors influencing the 8-item contact lens dry eye questionnaire score and comparison of translations in Japanese soft contact lens wearers

PurposeTo determine (1) the factors associated with a high degree of self-reported symptoms with Japanese translations of the 8-Item Contact Lens Dry Eye Questionnaire (J-CLDEQ-8) in a cross-section of soft contact lens (SCL) wearers in Japan and (2) whether the difference in translation of the CLDEQ-8 affects the scores between validated and non-validated versions of the Japanese translation.MethodsHabitual SCL wearers completed the validated J-CLDEQ-8 and a previous non-validated version. Demographics and SCL history questions were queried when they presented for routine eye care in nine geographically distinct clinics across Japan. The following risk factors for high J-CLDEQ-8 scores (≥11) were tested: sex, age, SCL replacement (daily disposable vs. bi-weekly and monthly reusable), years of SCL wear, and self-reported use of rewetting drops. The scores of the validated and non-validated questionnaires were compared.ResultsSignificant patient-related risk factors for high J-CLDEQ-8 scores were female sex, use of reusable SCLs, longer years of SCL wear, and use of rewetting drops. Scores for six out of eight questions in the validated J-CLDEQ-8 were significantly higher than those of the non-validated version, resulting in a significant difference in the average total score between the two questionnaires (validated J-CLDEQ-8: 10.5 ± 5.9 vs non-validated J-CLDEQ-8: 9.5 ± 5.8, P < 0.001).ConclusionsFemale sex, use of reusable SCLs, longer years of SCL wear, and use of rewetting drops were significant risk factors for high J-CLDEQ-8 scores in a cross-sectional clinical population of Japanese SCL wearers. Symptoms with SCL are not predicted by age and must therefore be queried at follow-up visits for all SCL wearers. Differences in the two translations affected the ability of the questionnaire to identify individuals with high symptoms associated with SCL wear.     

Theoretical fitting characteristics of typical soft contact lens designs

Purose

To calculate theoretical fitting success rates (SR) for a range of typical soft contact lens (SCL) designs using a mathematical model.

Visual quality with corneo-scleral contact lenses for keratoconus management

Purpose

To assess the visual quality achieved by fitting corneo-scleral contact lenses (CScL) for keratoconus management.

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.