Effect of Lens and Solution Choice on the Comfort of Contact Lens Wearers

Heart over head? A selective review of a career in research

This paper supports the award of the 2024 H. Barry Collin Research medal and gives an overview of my pathway through a research career. First, I recount my early clinical and research experiences in the United Kingdom. On moving to Australia, I was engaged in clinical studies aimed at developing silicone hydrogel contact lenses. A particular research interest in this regard was to determine the causes of contact lens-induced ocular redness and to investigate the reasons why silicone hydrogel lenses are able to solve this problem. This led me to develop more accurate objective methods for assessing ocular redness, where it became apparent that redness grading is predominantly a morphometric task, rather than a colourimetric one. Other research included resolving the apparent discrepancy between ocular redness induced by hypoxia created by a gas goggle versus a contact lens; understanding end-of-day contact lens discomfort; exploring alternative contact lens designs for correcting presbyopia; developing better methods for measuring visual performance using presbyopia-correcting contact lenses; and rethinking clinical criteria for assessing dry eye. In conclusion, my career has benefitted from interaction with colleagues in academia, industry and clinical practice, as well as with my fantastic students, both past and present.

Physical properties of soft contact lens multipurpose solutions commercially available in Ghana

Purpose

To investigate the physical properties of commercially available multipurpose soft contact lens solutions in Ghana.

Methods

pH (Kelilong ICL-099 pH meter, China), osmolality (OSMOMAT 3000, GONOTEC, Germany), surface tension (Sigma 700 Tensiometer, Sweden), and viscosity (CFOC-200 Viscometer, Cannon Company, USA) of various soft contact lens multipurpose solutions (MPS) were measured in triplicates at room temperature. Viscosity measurements were also taken at 34 °C ocular surface temperature. The solutions examined were Opti-Free Replenish (OFR), Trufresh (TF), Avizor (AV), Freshlook (FL), and Refresh (RF).

Results

Several solutions were largely hypo-osmotic in the range of 108-231 mOsm/kg, the exception being Avizor, which had osmolality values that were closer to human tears (301 ± 0.58 mOsm/kg). The range of pH values of the solutions (6.33-8.24, mean (SD) = 7.53 ± 0.18) fell within the reported tolerable range for the ocular surface (6.20-9.00). Surface tension values ranged from 35.86 to 42.27 mNm with a mean of 38.49 ± 2.32 mNm. The average viscosity of most solutions at room temperature (25 °C) was 1.44 ± 0.49 cP with a range of 1.04-2.15 cP. Significantly lower values ranging from 0.79 to 1.58 cP were obtained at ocular surface temperature (34 °C), p = 0.0001).

Conclusions

The physical properties of many of the solutions used as MPS in Ghana are markedly variable. Nevertheless, pH, surface tension, and viscosity fall within the acceptable limits of ocular physiological tolerance; except for osmolality, which majority were outside the reported tolerable range for the ocular surface. This information may partly explain the reason some patients exhibit strong preferences for certain care systems and should aid clinical decision-making when prescribing eye care systems to patients.

2023 Prentice Medal Award lecture: Ocular surface-related symptoms of discomfort and other stories

ABSTRACT

I have been fortunate to spend portions of my career in each of private practice, industry, and academia. At some times, these occupations have dictated the research direction, whereas, at others, curiosity has been allowed to dominate. This has resulted in multiple avenues of inquiry (some might say, too many), along which I have traveled with a rich and varied cast of collaborators, who have all taught me a great deal. The privilege of being awarded the Charles F. Prentice medal provides me an opportunity to summarize some of these activities. Beginning with an attempt to use contact lenses to solve a problem for those affected by albinism, the story shifts to addressing some of the wider deficiencies of contact lenses, in particular the consequences of their oxygen permeability and tendency to induce discomfort toward the end of the day. After briefly considering some aspects of meibomian gland function, the narrative concludes with the latest investigations of neurological links between the cornea and migraine.

Challenges to the new soft contact lens wearer and strategies for clinical management

Soft contact lens discontinuations have a dramatic impact on the overall success of this form of vision correction, and evidence suggests that the reasons for contact lens cessation are different for new wearers than for established lens users. In descending order, these relate to vision, discomfort, handling, inconvenience/loss of interest, ocular health and cost. This paper considers the background and underlying evidence for these causes of soft lens discontinuation in new wearers, and presents clinical management strategies to minimise this phenomenon. Such measures can reasonably be expected to significantly reduce the number of contact lens discontinuations leading to happier patients, increased satisfaction for eye care professionals (ECPs), and greater success for both individual practices and the contact lens industry more broadly.

Ocular surface microvascular response and its relation to contact lens fitting and ocular comfort: an update of recent research

This review examines vascular responses in the ocular surface to contact lens wear and its relation to lens fitting characteristics and contact lens-related discomfort. A search of PubMed was performed to find original research in English, within the past 10 years, that studied the ocular surface, including lid-wiper vascular responses to the lens. The interaction between the lens and ocular surface triggers vascular responses, impacting the lens fitting and contact lens-related discomfort. Contact lens-related discomfort is a multifactorial event, which is affected by lens characteristics. Overall, contact lenses with low modulus and a relatively tight fit produce significant ocular comfort. If an appropriate lens fit is achieved, lens fitting characteristics may not play a critical role in contact lens-related discomfort. On the other hand, the pathogenic and vascular changes of lid-wiper vascular responses appear to play an essential role in developing contact lens-related discomfort, in concert with reactions of the cornea (compression and staining) and conjunctiva (indentation and staining). Robust evaluation of lid-wiper changes at the cellular and microvascular level may hold the key to better understanding the mechanism of contact lens-related discomfort and reveal strategies for eliminating lid wiper epitheliopathy and improving ocular comfort in contact lens wearers.

CLEAR - Evidence-based contact lens practice

Evidence-based contact lens -->practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as -->minimising risks of lens wear through encouraging compliance) and an aftercare routine.

The association of comfort and vision in soft toric contact lens wear

PURPOSE

This work set out to investigate if there was an association between subjective comfort and both subjective and measured vision during the use of contemporary daily disposable soft toric contact lenses.

METHODS

Thirty-eight habitual soft contact lens wearers wore each of three daily disposable toric lenses for one week in a prospective, crossover, randomised, single-masked study. The following clinical measures were recorded at dispensing and follow-up visits: biomicroscopy scores, lens fitting (including rotation and rotational stability), high and low contrast visual acuity, subjective vision quality and subjective ocular surface comfort. Subjective scores were collected using 0-10 numerical grading scales. Comfort scores were analysed using a linear regression model with age, sex, visit, phase of crossover ('phase'), lens type, lens rotation, lens rotational stability, visual acuity, cylinder power and subjective vision quality as factors of interest and then refined using backward stepwise regression.

RESULTS

Thirty six participants (31.1 ± 13.5 years) completed the study. Comfort scores were found to be associated with subjective vision quality (F = 127.0 ; p < 0.0001), phase (F = 7.2; p = 0.001) and lens type (F = 4.9; p = 0.009). Greater comfort scores were observed with greater subjective vision quality scores. Visual acuity was not statistically significant in the model.

CONCLUSION

This work suggests that symptoms of ocular discomfort may be more intense if there is also perceived visual compromise in daily disposable soft toric lenses. There was a stronger positive correlation between comfort and subjective vision quality compared with comfort and measured visual acuity.

Visual Performance of Daily-disposable Multifocal Soft Contact Lenses: A Randomized, Double-blind Clinical Trial

SIGNIFICANCE

The present study highlights the differences between modern daily-disposable multifocal soft contact lenses to assist eye care practitioners in fitting presbyopic contact lens wearers.

PURPOSE

The purpose of this study was to compare visual performance of three daily-disposable multifocal contact lenses.

METHODS

Presbyopes (n = 72) wore 1-Day Acuvue Moist Multifocal, BioTrue ONEday for Presbyopia, and Dailies AquaComfort Plus Multifocal for 1 week in a prospective, randomized, double-blind, crossover clinical trial. After 1 week, high- and low-contrast visual acuities (HCVA, LCVA) were measured between 6 m and 40 cm and stereopsis at 40 cm. Subjective performance was assessed with 1- to 10-point rating scales for clarity, ghosting, driving vision, vision stability, ease of focusing, overall vision satisfaction, and ocular comfort. Willingness to purchase was reported with categorical responses. Linear mixed models and χ tests were used for analysis, and level of significance was set at 5%.

RESULTS

BioTrue provided better HCVA and LCVA at distance than did Acuvue Moist (P ≤ .03). Subjectively, Acuvue Moist was rated lowest for distance clarity, distance ghosting, and driving vision (P ≤ .05). Acuvue Moist provided better HCVA at 70 to 40 cm and LCVA at 1 m to 40 cm than did BioTrue (P ≤ .01) and better LCVA at 1 m to 50 cm than did AquaComfort Plus (P ≤ .02). AquaComfort Plus also provided better HCVA and LCVA at 50 and 40 cm than did BioTrue (P ≤ .03). Acuvue Moist provided better stereopsis than did BioTrue (P = .02). Subjectively, BioTrue was rated lowest for near clarity (P ≤ .007) and lower than Acuvue Moist for intermediate clarity and near ghosting (P ≤ .04). No other differences were found between lenses (P > .05).

CONCLUSIONS

BioTrue had better distance performance compared with near, whereas Acuvue Moist performed conversely. AquaComfort Plus performed reasonably overall.

Subjective Ratings and Satisfaction in Contact Lens Wear

SIGNIFICANCE

This study shows satisfaction in contact lens (CL) wear is influenced by both comfort and vision. Eighty-six percent of participants were willing to continue with trial CL wear if satisfied with both comfort and vision, dropping to 50% if either variable was unsatisfactory and 0% if both were unsatisfactory.

PURPOSE

The aim of this study was to understand the relationship between subjective ratings and satisfaction with CL wear.

METHODS

This was a retrospective analysis of two daily-disposable CL trials (delefilcon A, somofilcon A) on participants 40 years or younger followed over 3 months. Subjective ratings (numerical rating scale 1 to 10, 1-point step) collected at visits following baseline (2 weeks, 1 and 3 months) included comfort (insertion, during day, end of day), vision clarity, and binary response for satisfaction with comfort and vision (yes/no). Willingness to continue with trial CL was obtained at completion.

RESULTS

There was no significant association of comfort on insertion with comfort satisfaction (odds ratio [OR], 1.2; P = .30); however, comfort during day (OR, 2.1; P < .001) and end of day (OR, 3.4; P < .001) was associated with comfort satisfaction. For comfort during day ratings of at least 8/10 and end of day of at least 6/10, 90% of participants were considered satisfied. There was a 14% increase in participants satisfied with comfort for each unit increase on the numerical rating scale from ratings of 3 to 8 for comfort during day and a 20% increase from ratings of 3 to 7 for comfort end of day. The percentage of satisfied participants reached its maximum at a lower end of day rating (8/10) compared with during day (10/10). The percentage of participants satisfied with vision reached its maximum (100%) at a vision rating of 9/10.

CONCLUSIONS

Satisfaction in CL wear is influenced by both comfort and vision. A higher rating for comfort during the day compared with end of day is necessary for participants to attain satisfaction.

Discrimination of subjective responses between contact lenses with a novel questionnaire

PURPOSE

To describe a ranked symptoms scale (RSS) discriminating subjective responses in contact lens (CL) wear in various situations.

METHOD

Forty experienced clinical trial participants were interviewed for their perceptions of ocular comfort scales, resulting in a numerical RSS. For further evaluation, 20 CL wearers enrolled into a prospective, randomised, crossover trial. Two silicone-hydrogel CLs and a lens care solution (LCS) [Combinations A & B] were selected based on prior performance identifying best/worst combinations for end-of-day comfort. The RSS and a numerical rating scale (NRS) were administered at two time-points (insertion/removal) on alternating days for 6 days.

RESULTS

Both NRS and RSS showed acceptable internal consistency for comfort, vision and handling (Cronbach alpha=0.71 for both scales) and similar repeatability for comfort and handling (coefficients-of-repeatability within 0.1 and 0.2 units, respectively, for each scale). The NRS and RSS discriminated differences between combinations for comfort (p≤0.031) and vision (p≤0.026) at both time-points. Additionally, the RSS showed lens/edge awareness influenced discomfort the most, ranking higher at insertion (p=0.038) and higher for Combination-B at both time-points (p≤0.002). Symptoms of dryness and tired eyes increased for both combinations at removal (p<0.02). The RSS also showed haziness and blurred distance vision influenced vision dissatisfaction with Combination-B at lens removal (p≤0.038) while eye strain/headache increased for both combinations by time of removal (p≤0.013).

CONCLUSIONS

The RSS is able to discriminate subjective responses between combinations and time-of-day. The RSS's ability to rank symptoms may be a useful tool in understanding perceptions of discomfort or dissatisfaction with CL wear.

Impact of Spherical Aberration Terms on Multifocal Contact Lens Performance

PURPOSE

To investigate the impact of the primary (PSA) and secondary (SSA) spherical aberration terms on visual performance (VP) in presbyopes, as measured using multifocal (MFCL) soft contact lenses on eye.

METHODS

Seventeen presbyopes (age: 55.1 ± 6.9 years) wore seven commercial lenses (four center-near (MFCL N), one center-distance (MFCL D), one bifocal, and one single vision control). Unaided and with each lens on eye, the PSA and SSA terms were obtained with an aberrometer, the BHVI-EyeMapper (low illumination, natural and 4 mm pupil diameter). High- and low-contrast distance visual acuity, contrast sensitivity, high-contrast visual acuities at near, and range of clear vision were measured. In addition, subjective VP variables included clarity of vision at distance and near, ghosting, and overall vision satisfaction. Pearson's correlation was used to determine the association between the PSA and SSA terms and the VP variables.

RESULTS

PSA (natural pupil) was more negative (P < .05) with the MFCL N (mean PSA = -0.053 ± 0.080 μm) and bifocal (PSA = +0.005 ± 0.067 μm) lenses and more positive with the MFCL D lens (PSA = +0.208 ± 0.160 μm) than the control (+0.067 ± 0.072 μm). SSA (natural pupil) was significantly more positive for the MFCL N lenses (mean SSA = +0.025 ± 0.029 μm) compared to the control (SSA = -0.001 ± 0.017 μm). PSA and SSA terms were significantly (P < .05) correlated with 78% and 56% of VP variables, respectively, but the correlation coefficients were weak, ranging between |0.210| and |0.334|. Although distance variables showed improved VP with more positive PSA or negative SSA, most near variables showed improved VP with more negative PSA. Range of clear focus was greater for more negative PSA terms.

CONCLUSIONS

The amount and direction of PSA and SSA terms, as measured with different MFCLs on eye, can affect VP at different distances. Results of this study may provide useful information when designing new or optimize existing MFCLs for improved VP at specific distances.

Impact of Contact Lens Material, Design, and Fitting on Discomfort

OBJECTIVE

To review the effect of contact lens (CL) material, design, and fitting characteristics on CL discomfort.

METHODS

A PubMed search identified publications describing subjective comfort and CL material, fitting, and design parameters. The review included clinical signs associated with discomfort that may be a consequence of these parameters.

RESULTS

Reduced lens movement or more CL tightness were associated with improved comfort. Increased lens-induced paralimbal conjunctival staining and indentation, considered as quasi-indicators of CL fitting or edge design, were also associated with better comfort. No recent studies have evaluated varying CL design parameters and subjective comfort. Silicone hydrogel CLs are no different in comfort compared with hydrogel CLs. Lower equilibrium water content is associated with improved comfort in hydrogel CL wear. Coefficient of friction shows promise as a material factor potentially associated with comfort. Lid wiper epitheliopathy and lid-parallel conjunctival folds have been linked with comfort in established wearers.

CONCLUSIONS

Recent studies have confirmed the association between more mobile CLs and more discomfort, whereas closer conformity of the CL to the bulbar conjunctiva improved subjective comfort. There is no evidence to support the perceived comfort difference between silicone hydrogel and hydrogel CL. There has been limited progress in understanding the impact of varying specific CL design parameters. Although specific clinical signs may be predictive of discomfort, their role in the natural history of discomfort remains unclear. A better understanding of the relationship between coefficient of friction and comfort and strategies to improve lubricity may hold promise for limiting CL discomfort.

The TFOS International Workshop on Contact Lens Discomfort: report of the subcommittee on neurobiology

This report characterizes the neurobiology of the ocular surface and highlights relevant mechanisms that may underpin contact lens-related discomfort. While there is limited evidence for the mechanisms involved in contact lens-related discomfort, neurobiological mechanisms in dry eye disease, the inflammatory pathway, the effect of hyperosmolarity on ocular surface nociceptors, and subsequent sensory processing of ocular pain and discomfort have been at least partly elucidated and are presented herein to provide insight in this new arena. The stimulus to the ocular surface from a contact lens is likely to be complex and multifactorial, including components of osmolarity, solution effects, desiccation, thermal effects, inflammation, friction, and mechanical stimulation. Sensory input will arise from stimulation of the lid margin, palpebral and bulbar conjunctiva, and the cornea.