A prospective study of contact lens complications in a managed care setting

Development of corneal contact lens materials and current clinical application of contact lenses: A review

Unlike conventional glasses, corneal contact lenses (CLs) can directly contact the surface of the tear film through the application of biopolymer materials, to achieve therapeutic and cosmetic purposes. Since the advent of polymethylmethacrylate, a material that has gained widespread use and attention, statistically, there are now more than 150 × 106 people around the world who wear corneal contact lenses. However, the associated complications caused by the interaction of contact lenses with the ocular surface, tear film, endogenous and environmental microorganisms, and components of the solution affect nearly one-third of the wearer population. The application of corneal contact lenses in correcting vision and myopia control has been widely recognized. With the development of related materials, corneal contact lenses are applied to the treatment of ocular surface diseases, including corneal bandage lenses, drug-loaded corneal contact lenses, biosensors, and other new products, while minimizing the side effects associated with CL wear. This paper summarized the development history and material properties of CLs, focused on the current main clinical applications and mechanisms, as well as clarified the possible complications in wearing therapeutic contact lenses and the direction for improvement in the future.

CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia). However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation. In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.

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.

To rub or not to rub? - effective rigid contact lens cleaning

PURPOSE

To compare the efficacy of cleaning of rigid contact lenses using two care solutions with and without rubbing.

METHODS

A masked randomised trial was conducted. The cleaning efficacy of two solutions recommended for rigid contact lenses, a one-step hydrogen peroxide solution (HP) and a povidone iodine-based solution (PI), were evaluated on 64 unworn orthokeratology (ortho-k) lenses subsequent to cleaning with rubbing (R) with a surfactant cleaner or without rubbing (NR). Either mascara or hand cream was applied as a contaminant to the lenses to simulate stubborn and loosely bounded deposits, respectively. For each type of deposit, the lenses were randomly assigned to four cleaning treatments: R with HP, NR with HP, R with PI, and NR with PI (n = 8 for each group). Each lens surface was assessed on site by a masked examiner under a low-magnification slit-lamp and with photo-documentation. Lenses were graded according to the deposit coverage area using a pre-set five-point scale [0 (<20% coverage) - 4 (>80% coverage)].

RESULTS

For stubborn deposits (mascara), NR failed to remove deposits from 94% of lenses, whilst R removed more than 80% of deposits from 63% of the lenses. For oily deposits, 25% of NR lenses had >80% coverage, whilst only one R lens had 60-80% coverage, with 19% having 40-60% coverage, and 38% with either 20-40% or <20%. Rubbing improved lens cleanliness for both types of deposits, but only reached statistical significance for the stubborn deposit group. There were no significant differences between the solutions.

CONCLUSION

Not Rubbing and using either HP or PI solutions, is not effective in removing stubborn deposits from ortho-k lenses. It is essential to rub lenses when cleaning rigid lenses to ensure optimal lens hygiene for ocular health, especially as rigid gas permeable (RGP) lenses are intended to be reused for at least a year before replacement. Rubbing with a daily cleaner should be included in the instructions for use of the solutions tested for rigid lenses and practitioners should be encouraged to emphasise the importance of rubbing in lens care.

Critical Contact Lens Oxygen Transmissibility and Tear Lens Oxygen Tension to Preclude Corneal Neovascularization

OBJECTIVE

The purpose of this study is to determine the peripheral oxygen transmissibility (pDk/t) and respective central oxygen transmissibility (cDk/t) in soft contact lenses (SCLs) which might preclude SCL-driven corneal neovascularization (NV) in healthy myopic SCL users.

METHODS

Twenty subjectively successful SCL-wearing patients who presented with asymptomatic but active peripheral corneal NV (not ghost vessels) were recruited as study patients. Twenty-one patients who did not have NV were similarly recruited as controls. Demographic data were collected. Corneal NV was documented and photographed. Current habitual SCLs were collected and thicknesses measured to allow for the calculation of both pDk/t and cDk/t and estimation of local tear oxygen tensions.

RESULTS

No statistical differences between study and control groups in patient age, refraction, or the numbers of years, days per week, or hours per day patients reported SCL wear were identified. Statistically significant differences were found between the two groups for both pDk/t (P=0.006) and cDk/t (P=0.004): mean (±SD) pDk/t was 38.0±23.5 and 19.2±17.7 Fatt units for control and study corneas, respectively. Mean cDk/t were 80.0±54.4 and 36.8±33.1 Fatt units for control and study corneas, respectively. Peripheral tear oxygen tension that "protected" corneas from vascular filling was over 84 mm Hg.

CONCLUSION

Maintaining a pDk/t above 30 to 40 Fatt units with daily wear SCLs should protect most normal corneas from NV as a complication of SCL wear.

Clinical Performance of a Spherical Hybrid Lens Design in High Regular Astigmatism

OBJECTIVES

To evaluate safety, efficacy, and comfort of a spherical hybrid contact lens design in management of the regular astigmatic cornea.

METHODS

This prospective study included 18 eyes from 18 subjects with regular corneal astigmatism greater than -3.00 diopters. All patients were fitted with optimal hybrid contact lenses. Demographic data and fitting parameters were recorded. Patient refraction, visual outcomes, contrast sensitivity, and glare levels were measured 2 weeks, 3 months, and 6 months after the start of lens use. Duration of lens use, comfort grades, causes of lens discontinuation, and any noticed complications were recorded.

RESULTS

An average of 1.8 lenses (range 1-3) was required to achieve the optimal fit. Average logMAR visual acuity had improved significantly from 0.92±0.03 to 0.03±0.04 (P<0.001) at the last follow-up. Contrast sensitivity and glare tests were also significantly improved. Statistical analysis of the subjective responses indicated a strong acceptance of the lens by most of the patients. Mean wearing time of lenses was 10.1±3.2 hr/d. Causes of discontinuation were discomfort (2 patients), high lens price (2 patients), and handling problems (1 patient). Minimal complications were demonstrated in wearers of the lenses during follow-up visits.

CONCLUSION

Spherical hybrid contact lenses provide a good option for patients with regular astigmatic corneas. They provide optimal visual function with high comfort and patient satisfaction, especially when surgery is undesirable or contraindicated.

Prevalence of contact lens related complications in a tertiary eye centre in India

AIM

To determine the prevalence of contact lens related complications in a tertiary eye care centre in India.

METHODS

A retrospective review of the charts of 1255 patients who visited our contact lens clinic during 2001-2004 was conducted. The inclusion criteria included patients of at least 18 years of age, having refractive errors and keratoconus. Exclusion criteria included previous corneal surgeries and pediatric patients. 190 subjects with lens related complications were identified from among 923 patients who were using lenses.

RESULTS

The prevalence of contact lens complications was 20.58%. Females with complications were more common (59.47%). The complications were more common in students. The most common complications were contact lens induced papillary conjunctivitis (CLPC) (6.39%), corneal vascularisation (4%), and superficial punctate keratitis (SPK) (3.5%). The total complications were less prevalent in patients wearing rigid gas permeable (RGP) lenses as compared to soft contact lenses. Infectious keratitis was noted in 8 eyes. Pseudomonas aeuroginosa was the most common organism isolated. The average daily wear with RGP lenses was 11.04±3.7h and 10.96±3h with soft contact lens. The highest number of complications was noted in 47.89% patients who were wearing lenses for excess of 11h. The number of patients with complications arising due to sleeping with the lenses was 74 (38.95%).

CONCLUSION

Prevalence of contact lens complications was more in soft contact lens wearers compared to RGP wearers. CLPC was the most common complication followed by vascularisation and SPK.

Hyaluronic acid as an internal wetting agent in model DMAA/TRIS contact lenses

Model silicone hydrogel contact lenses, comprised of N,N-dimethylacrylamide and methacryloxypropyltris (trimethylsiloxy) silane, were fabricated and hyaluronic acid (HA) was incorporated as an internal wetting agent using a dendrimer-based method. HA and dendrimers were loaded into the silicone hydrogels and cross-linked using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide chemistry. The presence and location of HA in the hydrogels was confirmed using X-ray photoelectron spectroscopy and confocal laser scanning microscopy, respectively. The effects of the presence of HA on the silicone hydrogels on hydrophilicity, swelling behavior, transparency, and lysozyme sorption and denaturation were evaluated. The results showed that HA increased the hydrophilicity and the equilibrium water content of the hydrogels without affecting transparency. HA also significantly decreased the amount of lysozyme sorption ( p < 0.002). HA had no effect on lysozyme denaturation in hydrogels containing 0% and 1.7% methacrylic acid (MAA) (by weight) but when the amount of MAA was increased to 5%, the level of lysozyme denaturation was significantly lower compared to control materials. These results suggest that HA has great potential to be used as a wetting agent in silicone hydrogel contact lenses to improve wettability and to decrease lysozyme sorption and denaturation.

Patient compliance during contact lens wear: perceptions, awareness, and behavior

OBJECTIVES

Patient noncompliance with recommended hygienic practices in contact lens wear is often considered a significant risk factor for microbial keratitis and adverse contact lens-related events. Despite advancements in lens materials and care solutions, noncompliant behavior continues to hinder efforts to maximize contact lens safety. The objective of this pilot study was to assess the relationship between perceived and actual compliance with awareness of risk and behavior.

METHODS

One hundred sixty-two established contact lens wearers were sequentially evaluated after their routine contact lens examination at the Optometry Clinic at the University of Texas Southwestern Medical Center at Dallas, TX. Each patient was questioned by a single trained interviewer regarding his or her lens care practices and knowledge of risk factors associated with lens wear.

RESULTS

Eighty-six percent of patients believed they were compliant with lens wear and care practices; 14% identified themselves as noncompliant. Using a scoring model, 32% demonstrated good compliance, 44% exhibited average compliance, and 24% were noncompliant; age was a significant factor (P = 0.020). Only 34% of patients who perceived themselves as compliant exhibited a good level of compliance (P<0.001). Eighty percent of patients reported an awareness of risk factors, but awareness did not influence negative behavior. Replacing the lens case was the only behavior associated with a positive history for having experienced a prior contact lens-related complication (P = 0.002).

CONCLUSIONS

Perceived compliance is not an indicator for appropriate patient behavior. A large proportion of patients remain noncompliant despite awareness of risk. Education alone is not a sufficient strategy to improve behavior; newer approaches aimed at improving compliance with lens care practices are urgently needed.

SynergEyes lenses for keratoconus

PURPOSE

To discuss the initial results of fitting SynergEyes hybrid contact lenses (SynergEyes, Inc, Carlsbad, CA) for keratoconus (KC) and pellucid marginal degeneration (PMD).

METHODS

The charts of patients fit with SynergEyes lenses during the first 7 months the lens was available on the Cornea Service at Wills Eye Institute (August 3, 2006 to March 5, 2007) were retrospectively reviewed.

RESULTS

Sixty-one eyes (44 patients) with KC (58 eyes) or PMD (3 eyes) were fit with SynergEyes hybrid contacts. The mean age was 40 +/- 12.6 years; the mean follow-up period was 7.8 +/- 4.6 months. The most common indication for SynergEyes was rigid gas permeable (RGP) lens intolerance, 31 of 61 eyes (50.8%). Inability to fit with RGP was the indication in 8 eyes (13.1%), and 22 eyes (36%) were refit from SoftPerm (Ciba Vision, Corp, Duluth, GA). Twenty-two patients required refitting, including 17 base curve changes and 5 skirt changes. The success rate was 86.9% (53 of 61 eyes). Most failures (8 eyes of 6 patients) discontinued the lens within the first 1-2 months because of discomfort (5 eyes) or unsatisfactory vision (3 eyes).

CONCLUSION

SynergEyes lenses are a promising alternative for visual rehabilitation in patients with KC and PMD who are intolerant or unable to be fit in RGP lenses.

Silicone Hydrogel Contact Lenses and the Ocular Surface

For 30 years, contact lens research focused on the need for highly oxygen-permeable (Dk) soft lens materials. High Dk silicone hydrogel contact lenses, made available in 1999, met this need. The purpose of this review is to examine how silicone hydrogel lens wear affects the ocular surfaces and to highlight areas in which further research is needed to improve biocompatibility. Silicone hydrogel lenses have eliminated lens-induced hypoxia for the majority of wearers and have a less pronounced effect on corneal homeostasis compared to other lens types; however, mechanical interaction with ocular tissue and the effects on tear film structure and physiology are similar to that found with soft lens wear in general. Although the ocular health benefits of silicone hydrogel lenses have increased the length of time lenses can be worn overnight, the risk of infection is similar to that found with other soft lens types, and overnight wear remains a higher risk factor for infection than daily wear, regardless of lens material. Future contact lens research will focus on gaining a better understanding of the way in which contact lenses interact with the corneal surface, upper eyelid, and the tear film, and the lens-related factors contributing to infection and inflammatory responses.

Subjective Symptom of Eye Dryness and Lifestyle Factors With Corneal Neovascularization in Contact Lens Wearers

PURPOSE

To investigate effects of subjective symptom of eye dryness and lifestyle factors on corneal neovascularization (CNV).

METHODS

Subjects were 181 Japanese adults visiting an eye clinic for contact lens (CL) fitting. All completed a self-administered questionnaire related to sex, age, lens material (rigid gas-permeable or hydrogel lens), and subjective eye dryness. Hydrogel lens wearers were restricted to users of either Etafilcon A or Nelfilcon A. The lifestyle factors included weekly working hours on visual display terminal, smoking history, and duration of CL wear. CNV was graded on a 3-point ordinal scale using a slit-lamp and analyzed in logistic regression model: normal appearance (CNV 0), congestion and dilatation or vessel penetration < 1.0 mm (CNV 1), and vessel penetration > or = 1.0 mm (CNV 2).

RESULTS

The prevalence of CNV 2 was 26% (n = 47). Multivariate analysis showed that the following three factors were significantly associated with CNV through the stepwise regression model: a use of a hydrogel lens (odds ratio [OR], 2.55; confidence interval [CI], 1.04-6.25), subjective eye dryness (OR, 2.07; CI, 1.01-4.23), and weekly CL use (OR, 3.08; CI, 1.14-8.00). Additionally, a positive trend was found between the degree of weekly CL use and the severity of CNV (P for trend test = 0.002).

CONCLUSIONS

The prevalence of CNV in the setting of this study seemed to be higher than that in previous studies, indicating that a regular eye checkup is of paramount importance for eye care. Specifically, ocular symptomology of eye dryness with the information of CL use may be carefully explored in future research.

A 1-year prospective clinical trial of menicon Z (tisilfocon A) rigid gas-permeable contact lenses worn on a 30-day continuous wear schedule

PURPOSE

To establish the safety and efficacy of clinical performance of a novel hyper-O2-transmitting rigid gas-permeable (RGP) lens (tisilfocon A) worn continuously for 30 days (29 nights) equivalent to a conventional control hydrogel lens (etafilcon A) worn for 7 days (6 nights).

METHODS

The study was a prospective, open-label, 24-center, concurrent cohort-controlled clinical trial.

OUTCOME MEASURES

Outcome measures included rates of adverse events, slitlamp findings, length of wear achieved, lens-corrected visual acuity, corneal refractive changes, dryness, and lens deposits.

RESULTS

The RGP lens wear test was equivalent or superior to the hydrogel control performance in all categories. Two-thirds (66.5%) of patients wearing the RGP lens achieved continuous wear periods greater than 22 nights; and 60.4% achieved more than 28 nights of continuous use. There was a statistically significant lower rate of adverse events, considered definitely related to lens wear, for the RGP test lens versus the hydrogel control (none vs. 2.2%; P = 0.007, Fisher's exact two-sided test).

CONCLUSIONS

Continuous wear of the tisilfocon A (Menicon Z, Menicon Co., Ltd., Nagoya, Japan) RGP lens for up to 30 nights is a safe and equivalent alternative to 7-day (6-night) hydrogel wear.

Vascular response to extended wear of hydrogel lenses with high and low oxygen permeability

PURPOSE

The purpose of this study was to determine the impact of extended wear of high and low oxygen permeability (Dk) lenses on the development or resolution of limbal hyperemia and corneal neovascularization in a randomized prospective clinical trial.

METHODS

Adapted daily-wear contact lens wearers were randomly assigned to one of two groups. The low-Dk group (N = 23) wore etafilcon A lenses (Dk/t = 40) for up to 7 days and 6 nights, and the high-Dk group (N = 39) wore lotrafilcon A lenses (Dk/t = 175) for up to 30 days and nights. Limbal hyperemia and neovascularization were assessed and graded during 9 months of extended wear. A stratified analysis to determine how change in ocular redness depended on initial presentation was also conducted.

RESULTS

On a 0 to 100 scale, extended wear of low-Dk lenses resulted in a 16-point increase in limbal hyperemia (p < 0.0001); no significant change occurred with the high-Dk lenses. The difference was greatest for low-Dk participants who initially presented with lower levels of hyperemia (N = 18). There was a slight resolution of redness in participants who initially presented with higher levels of hyperemia (N = 10) after wearing the high-Dk lenses. Neovascularization increased by an average of 0.5 on a scale of 0 to 4 in low-Dk lens wearers (p < 0.0001) but remained unchanged in the high-Dk lens wearers. The increase was most marked for the low-Dk group with lower levels of neovascularization at baseline.

CONCLUSIONS

Subjects who wore lenses with higher oxygen permeability for 9 months of extended wear exhibited a lower vascular response of the ocular surface compared with subjects who wore lenses of lower oxygen permeability for the same period. This result was found both for the surface limbal vessels and in the deeper neovascular stromal vessels. Moderate neovascularization also developed after 3 months of extended wear of low-Dk hydrogels, whereas high-Dk lenses caused no neovascularization.

Comparative antimicrobial efficacy of multi-purpose hydrogel lens care solutions

Ten single-bottle multipurpose hydrogel lens care solutions commercially available in the European market were evaluated for antimicrobial efficacy using the International Organization for Standardization's (ISO) Stand-Alone Procedure. The results of this study indicate that ReNu Multi Plus ReNu Multi Purpose, Complete and DUA meet the ISO Stand-Alone primary acceptance criteria for stand-alone disinfectants against all challenge organisms: Staphylococcus aureus, Serratia marcescens, Pseudomonas aeruginosa, Candida albicans, and Fusarium solani. Solo-Care Soft, All-In-One Light, Optiplus, Opti Free Express, UniCare and Combi Comfort do not meet the ISO Stand-Alone primary acceptance criteria for one or more test organisms within their respective labelled minimum disinfection times. In addition, although not a requirement of the guidance document, only ReNu MultiPlus and ReNu Multi-Purpose exceeded the minimum ISO Stand Alone primary acceptance criteria within 25% (1 h) of their labelled minimum disinfection time for all test organisms. This evaluation provides a direct comparison of antimicrobial activity for commercially available multipurpose lens care solutions at their labelled minimum disinfection times. The results of this study should be considered when selecting appropriate lens care systems for patients.

On the relationship between soft contact lens oxygen transmissibility and induced limbal hyperaemia

The relationship between induced limbal hyperaemia and lens oxygen transmissibility was investigated in a series of clinical studies in which subjects wore a range of soft contact lenses for eight hours each. Data representing the degree of limbal hyperaemia induced in each case was extracted and subjected to non linear regression analysis with hyperaemia as dependent, and oxygen transmissibility as independent variables. Strong, statistically significant associations were found, particularly when oxygen transmissibility in a 12 mm diameter annular zone at the lens periphery was considered. Best fitting functions were of an inverse form for nasal (r2=0.86, P=0.008) and temporal (r2=0.81, P=0.014) quadrants and a logarithmic form for superior (r2=0.87, P=0.007) and inferior (r2=0. 97, P< 0.005) quadrants. These findings provide support for an hypoxic theory of soft contact lens induced limbal hyperaemia. Estimates based on the logarithmic model suggest a 95% confidence interval for the peripheral oxygen transmissibility required to avoid limbal hyperaemia of 56-274 x 10(-9) (cm s-1) (mlO2 ml-1 x mm Hg).