An evaluation of silicone‐hydrogel lenses worn on a daily wear basis

Efficacy of bandage contact lens for the management of dry eye disease after cataract surgery

Purpose

We aimed to evaluate the efficacy of bandage contact lens (BCL) for the management of dry eye disease (DED) after cataract surgery.

Methods

A total of 120 patients (140 eyes) with age-related cataract and DED were enrolled in this study. Patients underwent standard micro-incision phacoemulsification surgeries and were divided into control or BCL groups. Slit-lamp biomicroscopic examination, Ocular Surface Disease Index, keratograph analysis and Schirmer I test were executed, and the levels of tear inflammatory molecules were detected.

Results

In the control group, the NIAvg-BUT and Schirmer I test scores were significantly decreased at 1 week post-operation compared with baseline levels (P = 0.035 and P = 0.009, respectively). In the BCL group, the NIF-BUT and Schemer I test scores were significantly improved at 1 month after operation compared with the control group (P = 0.012 and P < 0.001, respectively). Levels of IL-6, IL-8 and ICAM-1 were significantly increased in the control group at 1 month after the operation (P = 0.005, P = 0.038 and P = 0.022, respectively), while there was no difference in the BCL group. The increase in the IL-6 level in the control group was significantly higher compared with that in the BCL group (P = 0.047). In DED patients, there were significant correlations between ocular surface parameters and inflammatory molecules.

Conclusions

Cataract surgery could lead to the development or worsening of DED. The application of BCLs after cataract surgery could stabilize the ocular surface and tear film, improve the corneal healing and reduce the inflammation. Collectively, our findings suggested that proper use of BCLs after cataract surgery played an effective role in the management of DED.

Trial registration

ClinicalTrials, NCT04100031. Registered 18 September 2019—retrospectively registered

Conjunctival Vascular Adaptation Related to Ocular Comfort in Habitual Contact Lens Wearers

PURPOSE

We sought to investigate the bulbar conjunctival vascular responses in habitual contact lens (HCL) and non-contact lens (NCL) wearers after short-term lens wear and their relationships with ocular comfort.

DESIGN

A prospective, comparative before-and-after study.

METHODS

Twenty-seven subjects (13 HCL and 14 NCL wearers) were enrolled. Microvasculature and microcirculation on the temporal bulbar conjunctiva were imaged at baseline and 0.5 and 6 hours after wearing contact lenses (1-Day Acuvue TruEye; base curve, 8.5 mm; power, -0.50 diopters) on both eyes. The measurements included vessel diameter (D), axial (VA), and cross-sectional (VS) blood flow velocities, blood flow volume (Q), and vessel density (Dbox) and complexity (D0). A Contact Lens User Experience (CLUE) questionnaire was used to assess ocular comfort.

RESULTS

No significant change (P > .05) was observed in D, VA, VS, Q, Dbox, and D0 in the HCL wearers after contact lens wear. By contrast, VA, VS, Q, Dbox, and D0 increased significantly after lens wear (after 0.5 and 6 hours) in NCL wearers compared with baseline (P < .05). Moreover, the changes from the baseline to 0.5 hours (VA, VS, and Dbox) and 6 hours (VA, VS, Q, Dbox, and D0) after contact lens wear in NCL wearers were significantly greater than that in HCL wearers (P < .05). The CLUE score 6 hours after lens wear was higher in HCL wearers than in NCL wearers (P < .05). It was also significantly correlated with VA, VS, and D0 after 6-hour lens wear in HCL wearers (P < .05).

CONCLUSIONS

This is the first study to reveal the relationship between ocular comfort and conjunctival vascular responses in habitual contact lens wearers.

Silicone hydrogel daily disposable benefits: The evidence

Daily disposable (DD) contact lenses first came to the market approximately 25 years ago and eye care professionals (ECPs) started prescribing silicone hydrogel (SiH) contact lenses, primarily for extended or continuous wear, approximately 20 years ago. It has now been over ten years since SiH DD contact lenses have been available, and while SiH materials are routinely prescribed by ECPs for reusable daily wear, hydrogel materials are still frequently selected for the DD modality of contact lens wear. This article reviews the evidence to support the benefits of both a DD modality and SiH materials and how patients' needs may be met with SiH DD contact lenses, with respect to clinical performance, health outcomes, satisfaction, compliance and convenience. Factors which may enable or constrain ECPs from prescribing SiH DD contact lenses, as opposed to hydrogel DD and reusable contact lenses, for more of their patients are discussed with the objective of providing ECPs with a greater understanding of the advantages that can be afforded by prescribing SiH DD contact lenses to both their new and existing contact lens wearers.

The impact of contact lens wear on ocular surface mucins using a novel clinical fluorescence imaging system

PURPOSE

Fluorescein-labelled wheat germ agglutinin (F-WGA) acts as a marker for ocular surface mucins. This clinical study sought to investigate whether the degree of F-WGA fluorescence observed at the ocular surface differed between symptomatic contact lens wearers, asymptomatic contact lens wearers and non-contact lens wearers, using a novel imaging system.

METHODS

Twenty-five participants (10 symptomatic contact lens wearers, 10 asymptomatic contact lens wearers and 5 non-contact lens wearers) attended a single study visit. Photographs of the cornea, bulbar and tarsal conjunctiva were captured following application of F-WGA solution.

RESULTS

The imaging system captured high-resolution images of F-WGA fluorescence at the ocular surface. The degree of fluorescence differed between the ocular surface regions (p < 0.001). A significant difference in fluorescence was observed between participant groups for the cornea (p = 0.01), with both the symptomatic and asymptomatic contact lens wearers showing lower fluorescence than the non-lens wearers. F-WGA associated fluorescence appeared diminished in the lid wiper region of the symptomatic lens wearers, compared to the asymptomatic group (p = 0.025).

CONCLUSION

The use of F-WGA as a clinical marker for ocular surface mucins allows an improved understanding of their distribution across the ocular surface. Contact lens wear appears to negatively impact mucin density across the ocular surface, with the most marked effect on the cornea. F-WGA fluorescence appeared diminished in the lid wiper region for the symptomatic contact lens wearing group, indicating that mechanical interaction in this region may play a role in the aetiology of contact lens discomfort. Given the ability of F-WGA to disclose mucin distribution across the ocular surface it is likely to be a key clinical tool in furthering our understanding of (i) the aetiology of contact lens related discomfort, (ii) contact lens designs/materials to minimise interaction with the ocular surface and (iii) dry eye disease and other ocular surface diseases.

The short-term physiological impact of switching reusable silicone hydrogel wearers into a hydrogel daily disposable multifocal

Purpose: To evaluate ocular physiological responses to etafilcon A multifocal (etMF) daily disposable (DD) lenses after 4 weeks of wear, when switching from habitual silicone hydrogel (SiHy) daily wear.

Method: A single-arm, open-label, bilateral dispensing study was conducted in 39 habitual spherical SiHy wearers (14 hyperopes; 25 myopes). Clinical visits occurred with habitual SiHy (control) at baseline and after 4 weeks of etMF DD open-eye lens wear at exit. Objective limbal/bulbar hyperemia using the Oculus K5M (0–4) and subjective grading of lid wiper epitheliopathy (LWE) (0–4) were tested for non-inferiority (NI), using a margin of 1 grade. Corneal thickness along a 10 mm cord was measured using the Visante OCT and tested for NI using a 30 μm margin. Corneal staining area was graded (0–100%).

Results: The least-square mean differences (LSMD) and 95% confidence interval (95% CI) between etMF DD and habitual SiHy in central and peripheral corneal thickness (μm) were 3.64 (−2.0, 9.29) and 3.0 (−7.72, 13.72) in hyperopic, and 3.56 (−0.66, 7.78) and 6.40 (−1.62, 14.42) in myopic subjects. The LSMD (95% CI) for bulbar and limbal hyperemia were −0.08 (−0.19, 0.02) and −0.01 (−0.12, 0.09) in hyperopes, and 0.04 (−0.03, 0.12) and 0.04 (−0.04, 0.11) in myopes. The LSMD (95% CI) for LWE were 0.11 (−0.39, 0.60) and 0.30 (−0.07, 0.67) for hyperopes and myopes, respectively.

Conclusions: No clinically significant differences in a variety of physiological responses were found when habitual reusable SiHy daily wear subjects were refitted into hydrogel etMF, when the subjects were followed for 4 weeks.

Effect of multipurpose solutions on in vivo surface wettability of a silicone hydrogel lens

PURPOSE

To compare the in vivo surface wettability of silicone hydrogel (SiHy) contact lenses pre-soaked overnight in different multipurpose solutions (MPS) and normal saline.

METHODS

In this double-blinded, randomized and self-controlled study, 36 subjects were fitted with three pairs of contact lenses (senofilcon A) pre-soaked overnight in five different MPS and saline in a randomized order. Each pair of lenses (pre-soaked in two different solutions the night before) were worn for 15min before assessment of pre-lens non-invasive tear break-up time (PL-NITBUT) using the Medmont corneal topographer (video recording). Corneal integrity was assessed using a slit lamp and a resting interval of 20min was allowed between each pair of lenses to ensure post-lens wear corneal integrity.

RESULTS

Thirty subjects completed the study. The median PL-NITBUT ranged from 2.84s to 3.08s with lenses pre-soaked in different MPS, compared to 2.78s with lenses pre-soaked in saline. No significant differences in PL-NITBUT were found among lenses pre-soaked in different solutions (p=0.647).

CONCLUSION

In vivo surface wettability, in terms of PL-NITBUT after 15min of lens wear, of senofilcon A contact lenses pre-soaked overnight in different MPS were not significantly different from those pre-soaked in saline.

Are silicone hydrogel contact lenses more comfortable than hydrogel contact lenses?

The current literature review was intended to investigate whether the use of silicone hydrogel contact lenses has resulted in improved comfort compared with that of hydrogel contact lenses when both are used for daily wear. The conclusion reached is that silicone hydrogel contact lenses, which were initially developed to eliminate hypoxia during overnight wear, have not significantly improved comfort compared with the comfort achieved with hydrogel contact lenses when worn on a daily wear basis, even though a body of the published literature would suggest to the contrary. A careful review and consideration of the literature demonstrates that the relative comfort achieved with the two types of contact lenses is in fact highly dependent on the study methodology: Although refitting studies have concluded enhanced comfort with silicone hydrogels, the more robust study designs involving concurrent controls and masking were not able to show a difference, and some even concluded an inferior performance. Evidence-based review has however clearly demonstrated that comfort cannot be considered in isolation but is contact lens specific and depends on the material surface and bulk properties, lens design characteristics, and modality of use of the contact lens, and may also be significantly influenced by the replacement frequency and interaction with any lens care system that may be used.

The effects of 2 week senofilcon-A silicone hydrogel contact lens daily wear on tear functions and ocular surface health status

PURPOSE

To prospectively investigate the effects of 2 week senofilcon A contact lens (CL) daily wear on the functional visual acuity (VA), ocular surface and tear film.

METHODS

Seventeen right eyes of 17 senofilcon A CL wearers without any ocular or systemic diseases were examined before and 2 weeks after lens wear. Visual acuity measurements, tear evaporation rate, ELISA for tear cytokines, strip meniscometry, tear lipid layer interferometry, tear film break-up time (BUT), in vivo confocal microscopy, corneal sensitivity, ocular surface vital staining, Schirmer I test and brush cytology for MUC5AC mRNA expression were performed before and after CL wear.

RESULTS

The best corrected Landolt VA, functional VA parameters, the mean lipid layer interferometry grades, tear evaporation rates, Schirmer test values, vital staining scores and in vivo confocal microscopy parameters did not show any significant differences after 2 weeks of CL wear. The tear film BUT showed a significant decrease together with a significant down regulation of MUC5 AC mRNA expression after CL wear. A statistically significant elevation in the mean tear interleukin (IL)-6 concentration was also observed after 2 weeks of CL wear.

CONCLUSIONS

Two week senofilcon A daily CL wear seems to be associated with tear instability, a decrease in MUC5AC expression, and elevation of IL-6 in tears without significant alterations in epithelial damage scores or in the morphology or density of in vivo keratoconjunctival cells and nerves. Alterations associated with long term wear and patients with dry eye disease need to be studied in future trials.

Comfort and vision with silicone hydrogel lenses: effect of compliance

PURPOSE

Silicone hydrogel (SH) lenses are usually replaced after 2 weeks (2W) or 1 month (1M); however, many patients do not comply with the manufacturers' recommended replacement frequency (MRRF). The purpose of this analysis was to investigate the effect of compliance with MRRF on comfort and vision in SH wearers.

METHODS

As a part of a larger study investigating compliance with MRRF, patients were asked to rate their subjective comfort and vision from 0 (very poor) to 10 (excellent) in the morning, at the end of the day (EVE), when lenses were new, and needed replacing (NR).

RESULTS

One thousand three hundred forty-four patients wore 2W replacement modality (2WR) (n = 717) or 1M replacement modality (1MR) (n = 617) SH lenses. Comfort and vision in the morning and when lenses are new were significantly higher than for EVE and NR (p < 0.001). Twenty-nine percent (95% confidence interval 25.3-32.4) of 1MR and 59% (95% confidence interval 55.5-62.7) of 2WR wearers were non-compliant with the MRRF. Compliance had a significant effect on EVE (p = 0.002, p = 0.008) and NR (p < 0.001, p < 0.001) comfort and vision. After accounting for compliance, EVE and NR comfort and EVE vision were higher for 1MR than 2WR (p = 0.015, p = 0.044, p = 0.019).

CONCLUSIONS

Compliant patients had better EVE and NR comfort and vision than non-compliant patients, regardless of replacement modality. Optimal subjective performance with SH lenses seems to be facilitated by replacing lenses as recommended.

Dynamic Contact Angle Analysis of Silicone Hydrogel Contact Lenses

Contact angle measurements are used to infer the clinical wetting characteristics of contact lenses. Such characterization has become more commonplace since the introduction of silicone hydrogel contact lens materials, which have been associated with reduced in vivo wetting due to the inclusion of siloxane-containing components. Using consistent methodology and a single investigator, advancing and receding contact angles were measured for 11 commercially available silicone hydrogel contact lens types with a dynamic captive bubble technique employing customized, fully automated image analysis. Advancing contact angles were found to range between 20° and 72° with the lenses falling into six statistically discrete groupings. Receding contact angles fell within a narrower range, between 17° and 22°, with the lenses segregated into three groups. The relationship between these laboratory measurements and the clinical performance of the lenses requires further investigation.

Measurement errors related to contact angle analysis of hydrogel and silicone hydrogel contact lenses

This work sought to undertake a comprehensive investigation of the measurement errors associated with contact angle assessment of curved hydrogel contact lens surfaces. The contact angle coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intralens COR, and interlens COR) was determined by measuring the contact angles (using both sessile drop and captive bubble methods) for three silicone hydrogel lenses (senofilcon A, balafilcon A, lotrafilcon A) and one conventional hydrogel lens (etafilcon A). Image analysis COR values were about 2 degrees , whereas intralens COR values (95% confidence intervals) ranged from 4.0 degrees (3.3 degrees , 4.7 degrees ) (lotrafilcon A, captive bubble) to 10.2 degrees (8.4 degrees , 12.1 degrees ) (senofilcon A, sessile drop). Interlens COR values ranged from 4.5 degrees (3.7 degrees , 5.2 degrees ) (lotrafilcon A, captive bubble) to 16.5 degrees (13.6 degrees , 19.4 degrees ) (senofilcon A, sessile drop). Measurement error associated with image analysis was shown to be small as an absolute measure, although proportionally more significant for lenses with low contact angle. Sessile drop contact angles were typically less repeatable than captive bubble contact angles. For sessile drop measures, repeatability was poorer with the silicone hydrogel lenses when compared with the conventional hydrogel lens; this phenomenon was not observed for the captive bubble method, suggesting that methodological factors related to the sessile drop technique (such as surface dehydration and blotting) may play a role in the increased variability of contact angle measurements observed with silicone hydrogel contact lenses.

Corneal shape changes induced by first and second generation silicone hydrogel contact lenses in daily wear

PURPOSE

To compare the corneal topographical changes induced by two first and second generation silicone-hydrogel (SiH) contact lenses after 3 months of daily wear (DW).

METHODS

Prospective, consecutive case-series in which patients wore one of 3 different contact lenses (either the first generation SiH Focus Night & Day, the second generation SiH Acuvue Oasys or the monthly disposable Soflens 38 hydrogel lens as control group) on a DW basis for 3 months. Over-refraction, visual acuity, mean keratometry, corneal astigmatism, corneal eccentricity, superficial regularity and superficial asymmetry indices were monitored over the 3-month period.

RESULTS

Nineteen eyes of 10 patients completed the study. Seven Focus Night & Day, 7 Acuvue Oasys and 5 Soflens 38 contact lenses were fitted. There were no significant changes between any of the parameters measured at the 3-month visit in any of the SiH groups (non-parametric Wilcoxon test, p>0.05). However, the control group (Soflens 38) showed statistically significant changes regarding mean keratometry, corneal astigmatism and corneal eccentricity (p<0.05). Three patients wearing the first generation SiH showed adverse events of different degree related to their high modulus of elasticity.

CONCLUSIONS

After 3 months of DW, wearers of first and second generation SiH lenses showed greater corneal stability than hydrogel monthly disposable contact lenses users regarding commonly used topographic corneal shape indices. However, complications related to the mechanical properties of first generation SiH were seen in three patients in the follow-up time.

The Stability of Dryness Symptoms After Refitting With Silicone Hydrogel Contact Lenses Over 3 Years

PURPOSE

To assess the stability of dryness symptoms after refitting patients wearing low-Dk/t hydrogel contact lenses with high-Dk/t silicone hydrogel contact lenses and to determine whether early dryness symptoms were predictive of discontinuation in the 3-year study.

METHODS

Two hundred seventy-eight hydrogel lens wearers were refitted with lotrafilcon A silicone hydrogel contact lenses for continuous wear of up to 30 nights. Self-administered questionnaires at baseline, 1 week, and 3 years captured the frequency and intensity of dryness symptoms during the day and at the end of the day. One-week and 3-year responses were compared to baseline by a Bowker test of symmetry and median change in response with Wilcoxon signed rank test.

RESULTS

Frequency of during-the-day and end-of-day dryness decreased from baseline to 1 week and 3 years (during the day, frequency > or = "sometimes" 57.1% vs. 33.1% after 1 week and 58.5% vs. 28.8% after 3 years; end of day, 61.1% vs. 41.0% after 1 week and 64.0% vs. 35.9% after 3 years [P<0.0001 for all comparisons]). After refitting, the proportion of subjects with dryness symptoms was stable. After 1 week, the presence of frequency of at least "sometimes" and severity of at least "moderate" during-the-day and end-of-day dryness were significantly associated with study discontinuation (during-the-day frequency [P=0.007] and severity [P=0.017]; end-of-day frequency [P=0.002] and severity [P=0.003]).

CONCLUSIONS

Dryness symptoms improved after 1 week of refitting with lotrafilcon A and remained stable through 3 years. The presence of dryness after 1 week was associated with discontinuation from contact lens wear. Refitting with silicone hydrogel lenses reduced the frequency and severity of dryness symptoms seen with hydrogel lens wear for many subjects.

Contact lens-induced changes in the anterior eye as observed in vivo with the confocal microscope

The availability of the confocal microscope over the past decade has allowed clinicians and researchers to refine their understanding of the physiological and pathological basis of the ocular response to contact lens wear, and to discover previously unknown phenomena. Mucin balls, which form in the tear layer in patients wearing silicone hydrogel lenses, can penetrate the full thickness of the epithelium, leading to activation of keratocytes in the underlying anterior stroma. Epithelial cell size increases in response to all forms of lens wear, with lenses of higher oxygen transmissibility (Dk/t) interfering least with the normal process of epithelial desquamation. A higher density of Langerhans' cells is observed in the layer of the sub-basal nerve plexus among contact lens wearers, suggesting that contact lens wear may be altering the immune status of the cornea. Dark lines and folds are observed in the oedematous cornea in response to contact lens wear. Mechanical stimulation of the corneal surface, due to the physical presence of a contact lens, and the consequent release of inflammatory mediators, is the likely cause of reduced keratocyte density associated with lens wear. Highly reflective stromal 'microdot deposits' are observed throughout the entire stroma in higher numbers in lens wearers. 'Blebs' in the endothelium have a bright centre surrounded by a dark annular shadow; this appearance is explained with the aid of an optical model. The confocal microscope has considerable clinical utility in diagnosing Acanthamoeba and fungal keratitis. At the limbus, contact lenses can induce structural changes such as increases in basal epithelial cell size. An increased number of rolling leucocytes is observed in limbal vessels in response to low Dk/t lenses. It is concluded that the confocal microscope has considerable utility in contact lens research and practice.

A 12-month prospective clinical trial of comfilcon A silicone-hydrogel contact lenses worn on a 30-day continuous wear basis

PURPOSE

To evaluate the clinical performance of comfilcon A (Biofinity) during 12 months of continuous wear compared to other silicone-hydrogel lenses.

METHOD

Forty-five subjects were fitted in one eye with the comfilcon A (test) lens. For 22 subjects, the other eye was fitted with lotrafilcon A (group A) and for the remaining 23 subjects the other eye was fitted with balafilcon A (group B). Twelve-month data are presented on 48 measured variables.

RESULTS

There were no serious adverse events during the course of the study. A total of 33 subjects completed the study, with only 4 discontinuations for lens-related reasons, spread proportionately between the lenses. On preference scales, the test lens was superior to both control lenses for comfort (p<0.05) and overall preference (p<0.05) and in group A for vision (p<0.05). On grading scales, the test lens scored better than both control lenses for overall comfort (p<0.1 for group A, p<0.05 for group B), comfort during the day (p<0.05), end-of-day comfort (p<0.05) and overall preference (p<0.05), and better in group A for general vision quality (p<0.01), night vision quality (p<0.01) and handling (p<0.05). All lenses performed to a comparable degree on the basis of microcysts and corneal staining. There were significant differences between lenses in producing limbal redness (p<0.05), bulbar conjunctival hyperemia (p<0.1) and conjunctival NaFl staining (p<0.01) with the control lens in group A showing the greatest effect and the control lens in group B the least.

CONCLUSION

Comfilcon A offers performance advantages over first generation silicone-hydrogel materials for continuous wear.

Incomplete blinking: Exposure keratopathy, lid wiper epitheliopathy, dry eye, refractive surgery, and dry contact lenses

Exposure keratopathy, including that which occurs following laser assisted keratomileusis, appears to be associated with incomplete blinking. Incomplete blinking may contribute to the signs and symptoms of lid wiper epitheliopathy. In addition, precipitation of contact lens surface deposits and other contact lens surface drying phenomena, appear to be accelerated by incomplete blinking. For the inferior cornea or contact lens surface an incomplete blink approximately doubles the interblink interval and tear evaporation time, becoming even longer as blink rates reduce for computer and reading tasks. Inadequate aqueous, mucous and lipid distribution, as well as tear thinning over the exposed ocular or contact lens surface, may further increase the rate and significance of tear break-up and evaporation following an incomplete blink. Increased tear osmolarity that is associated with accelerated tear evaporation may also contribute to tissue changes and symptoms. Behaviour modification and habit reversal methods can be employed in the provision of blink efficiency exercises that are used to overcome incomplete blinking habits, with the potential to improve lipid, mucous and aqueous distribution so that exposure keratopathy, lid wiper epitheliopathy, and any associated symptoms are alleviated and/or prevented. Similarly, improved blink efficiency may help maintain lens surface condition and alleviate dryness symptoms for contact lens wearers. Lubricant drop instillation that is combined with blink efficiency exercises may increase the therapeutic benefit to corneal, conjunctival and lid wiper epithelium, as well as improving contact lens performance. Conditions of drop instillation, that reduce reflex blinking and tearing, may increase drop contact time and therapeutic benefit.

In vitro water wettability of silicone hydrogel contact lenses determined using the sessile drop and captive bubble techniques

This study investigated the water contact angles of five commercially available silicone hydrogel contact lenses (Acuvue Advance, Acuvue Oasys, Focus Night & Day, O2 Optix, and PureVision) using sessile drop and captive bubble techniques. The only lens type that showed a significant difference in water contact angle when measured by sessile drop direct from the blister compared with after 48 h of soaking/washing in saline was the Acuvue Advance lens (from 66 degrees to 96 degrees, respectively) (p=0.0002), presumably because of surface active agents within the blister solution. The water contact angle data split the lenses into two distinct groups (p<or=0.002). The Acuvue Advance, Acuvue Oasys, and PureVision lenses demonstrated relatively high sessile drop measures and relatively low captive bubble values (thereby displaying significant hysteresis) whereas the Focus Night & Day and O2 Optix lenses showed relatively low sessile drop measures and relatively high captive bubble values (with little hysteresis). Contact angle analysis of hydrogel lens surfaces is highly methodologically dependent and may be able to predict the clinical performance of contact lenses in vivo.