Soft Lenses Research Articles

Blinking Patterns and Corneal Staining

To investigate the blinking patterns of healthy subjects and soft contact lens wearers and determine whether these blinking characteristics were associated with corneal fluorescein staining. Fifteen young soft contact lens wearers and 11 young, healthy subjects participated in the study. The subjects were selected to have no significant eyelid disease. High-speed filming (100 frames per second) was used to capture the natural blinking patterns of the subjects for approximately 3 minutes. Custom written software was used to measure the vertical palpebral aperture at the start and the end of the downward motion of the upper eyelid. The vertical gap between the lids at the lowest point of the upper lid movement during each blink was measured (closed palpebral aperture). Corneal fluorescein staining was quantified on a 0-to-4 scale for each subject. Closed palpebral apertures in the healthy and soft contact lens-wearing subjects showed a wide distribution, with 22% of blinks being incomplete (<2/3 open aperture) in both groups of subjects. In soft contact lens wearers, there was a significant correlation (r = 0.40, P<0.05) between the mean closed palpebral aperture and the grade of corneal staining (primarily located inferiorly). The healthy subjects did not show the same degree of correlation (r = 0.16, P>0.1). However, the distribution of closed palpebral apertures was significantly different between those subjects with corneal staining compared to those without corneal staining (Kolmogorov-Smirnov two-sample test, healthy subjects with P=0.002 and soft lens wearers with P<0.001). The distribution of closed palpebral apertures of healthy and soft contact lens-wearing subjects showed no clear distinction between complete and incomplete blinks. Both groups of subjects show evidence of an association between the mean closed palpebral aperture size (degree of incomplete blinking) and the grade of corneal fluorescein staining, but the association is stronger in soft contact lens wearers.

The Pathogenesis of Contact Lens-Related Keratitis

Bacterial infection of the cornea is a rare, but sight-threatening, complication of contact lens wear that was first reported shortly after soft lenses were introduced onto the market in the 1970s. During the past 3 decades, various attempts to solve the problem with new lens types and lens care products have failed to make a significant impact on its incidence. Eliminating contact lens-related infections will likely require a better understanding of the ocular defense system, microbial virulence strategies, how they affect one another, and the effects of contact lens wear on both. Each of these topics is complex. Although research in this area is therefore challenging and necessitates a multidisciplinary approach, what we are learning along the way has significance beyond contact lens-related infection and could ultimately lead to the development of new strategies to prevent this and a range of other sight- and life-threatening diseases.

Prevalence of Ocular Surface Symptoms, Signs, and Uncomfortable Hours of Wear in Contact Lens Wearers: The Effect of Refitting with Daily-Wear Silicone Hydrogel Lenses (Senofilcon A)

Many soft contact lens wearers have symptoms or signs that compromise successful lens wear. This study estimated the prevalence of problems in current wearers of soft contact lenses and tested the effect of refitting patients with senofilcon A silicone hydrogel lenses (ACUVUE Oasys). Prevalence was estimated from 1,092 current lens wearers for frequent or constant discomfort or dryness, at least 2 hours of uncomfortable wear, at least grade 2 limbal or bulbar hyperemia (0-4), or at least grade 3 corneal staining (0-15). In the second part of the study, 112 of the 564 wearers classified as problem patients were refitted with senofilcon A lenses and reassessed 2 weeks later. Fifty-two percent (564 of 1,092) had some qualifying criteria, with dryness reported by 23%, discomfort by 13%, and at least 2 hours of uncomfortable wear by 27%. Six percent of subjects had qualifying limbal hyperemia; 10% had bulbar hyperemia; and 12% had corneal staining. After refitting 112 problem patients, 75% had less dryness; 88% had better comfort (P<0.0001 each); and 76% had fewer uncomfortable hours of wear (P=0.004). Although the average wearing time was unchanged, comfortable wearing time increased significantly (10.4 to 11.6 hours) (P=0.004). All (35 of 35) eyes with qualifying limbal hyperemia before the refit also improved (P<0.0001), as did 80% (40 of 50) of those with bulbar hyperemia (P<0.0001) and 76% (26 of 34) of those with corneal staining (P=0.005). Most soft lens wearers encounter clinically significant signs or symptoms with their current contact lenses. Refitting with new-generation silicone hydrogel lenses (senofilcon A) can alleviate some of these common problems.

Calculated tear oxygen tension under contact lenses offering resistance in series: Piggyback and scleral lenses

Background Models of oxygen delivery to the cornea with contact lens wear have considered the customary situation of one lens being worn on the cornea. However, two lenses, such as a rigid lens piggybacked on a soft lens, may be worn by patients with special ocular and visual needs. This paper extends existing single lens models to circumstances where two lenses offer resistance to oxygen in series. Methods Theoretical oxygen tensions are calculated for tear layers trapped beneath piggyback contact lens systems (and scleral lenses) and the anterior corneal surface with a simple single chamber corneal model using a personal computer software spreadsheet. Results Acceptable values are anticipated for contact lens materials of modern oxygen permeability values of approximately 60–100 Fatt Dk units under open eye conditions. Conclusions The results of this spreadsheet model of oxygen supply to the anterior corneal surface offer a useful guide to clinicians concerned about providing their patients with physiologically acceptable piggyback lens systems.

Objective and Subjective Responses in Patients Refitted to Daily-Wear Silicone Hydrogel Contact Lenses

Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. Eighty-seven successful soft lens wearers (8.4+/-4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were "masked" as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p<0.001), particularly for those subjects with greater baseline hyperemia (p<0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p<0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort.

Visual Performance of Subjects Wearing Presbyopic Contact Lenses

The purpose of this study is to assess the visual performance of subjects wearing gas-permeable (GP) multifocal contact lenses, soft bifocal contact lenses, GP monovision lenses and spectacles. The study included 32 subjects between the ages of 42 and 65 years wearing GP monovision, the Acuvue Bifocal (Vistakon), the Essentials GP Multifocal (Blanchard), and progressive addition lenses (PAL; spectacles group). There were eight subjects in each of these groups who were already wearing these modalities. Binocular low (18%) and high (95%) contrast acuities were recorded using the Bailey-Lovie chart; binocular contrast sensitivity from 1.5 to 18 cycles per degree (cpd) measured with the Vistech VCTS 6500 system, and monocular glare sensitivity at three luminance settings (400, 100, and 12 foot lamberts) was measured using the brightness acuity tester (BAT). Binocular near visual task performance (a modified version of letter counting method used in previous presbyopic studies) was also assessed. For the contact lens-wearing groups, subjects wearing GP multifocals provided the best binocular high and low contrast acuity followed by soft bifocal wearers. There was relative parity between the binocular high and low contrast acuity with PAL and GP multifocal wearers. Monovision acuity, measured binocularly, was determined to be lower than the other three groups with this difference being most significant with high contrast acuity. Among contact lens-wearing groups, it was observed that GP multifocal lens wearers experienced the lowest amount of monocular disability glare followed by soft bifocal wearers and monovision wearers. Subjects wearing soft bifocal lenses and monovision demonstrated slightly reduced binocular contrast sensitivity at all spatial frequencies. In the contact lens groups, GP multifocal lens wearers had the highest binocular contrast sensitivity at all spatial frequencies, on parity with PAL wearers, except at the highest spatial frequency (18 cpd) at which PAL wearers had better vision. Error scores for the binocular near visual task performance between the four groups revealed subjects with GP multifocal lenses and PAL wearers to have the least errors, followed by monovision users and then soft bifocal wearers with the most errors. Subjects wearing GP multifocals, soft bifocals, monovision, and PAL spectacles have good binocular contrast sensitivity, satisfactory binocular low and high contrast acuity, and increased sensitivity to glare. Presbyopic subjects requiring the use of contact lenses under dim light levels could benefit from GP multifocal lenses. Contrast and glare sensitivity evaluations provide significant information regarding the visual performance of the presbyopic contact lenses and should be included in regular presbyopic contact lens fitting.

Clinical evaluation of a new multi-purpose disinfecting solution in symptomatic contact lens wearers

Purpose To evaluate the safety and efficacy of a new multi-purpose disinfecting solution (MPDS) in symptomatic soft contact lens wearers using Group IV soft lenses and compare its performance with that of a marketed MPS. Methods This was a 4-week, randomized, concurrently controlled, double-masked, multi-site study involving 362 subjects at 19 investigational sites in the US. Existing Group IV lens wearers, pre-screened to be symptomatic for contact lens-related ocular discomfort, were fitted with a new pair of lenses that matched their pre-study lens brand then randomly assigned to one of two treatment regimens: Regimen 1 (OPTI-FREE ® RepleniSH™ MPDS, Alcon Laboratories Inc.) or Regimen 2 (ReNu ® MultiPlus ® MPS No Rub Formula, Bausch and Lomb Inc.). At Day 0 (baseline), Days 14 and 28 subjects recorded comfort and ocular symptoms, wearing time, rewetting drop and lens removal frequency, and investigators assessed slit-lamp findings, lens deposits and wettability, and visual acuity. Results Total corneal staining mean score was significantly lower for the Regimen 1 group at Day 14 ( P ≤ 0.02). Comfort and dryness mean scores were significantly better for Regimen 1 compared to Regimen 2 at Day 28 ( P ≤ 0.02; P ≤ 0.007) and mean scores for scratchiness and burning were significantly lower at Day 14 ( P ≤ 0.04; P ≤ 0.01). Significant differences were noted in favor of Regimen 1 on 12 of the 12 Likert questionnaire statements ( P < 0.05). Average lens wearing time was significantly greater for the Regimen 1 group compared to the Regimen 2 group at Day 14 ( P < 0.05). Lens deposits were significantly lower with Regimen 1 than with Regimen 2 ( P ≤ 0.02). Conclusion This study shows that the new formulation is safe and efficacious when used by symptomatic Group IV lens wearers. Comfort, ocular signs and symptoms and wearing times in patients experiencing problems with their contact lenses can be influenced by the choice of MPS. Selecting an appropriate lens care product enhances patients’ wearing experience, maintains optimal lens performance and may help to prevent drop-out.

Soft Contact Lenses for Keratoconus: Case Report

Contact lenses have assisted the refractive correction of keratoconus since the 19th century. In these case reports, the authors describe their experience with a new soft contact lens design. The Soft K is a new soft lens comprising a thick fenestrated design to fit in patients with mild to moderate corneal distortion and fitting problems or physical intolerance to rigid gas-permeable (RGP) contact lenses. Three eyes with mild keratoconus from two 25-year-old patients (one man and one woman) were fitted with the Soft K contact lens. Both patients had previously worn other contact lens types. Improvements in comfort and quality of vision compared with previously worn RGP or soft toric contact lenses were the most remarkable advantages objectively observed and subjectively described by both patients. For one patient, a professional soccer player, the benefits were also important in terms of compatibility with the dynamic environment of his activity, satisfying the need for stable correction and constant full field-of-view demand without spectacles. No physiologic complications such as edema or neovascularization were observed during the follow-up period. This new soft lens design for irregular corneas is especially indicated for those with intolerance to RGP or other contact lenses and for patients for whom RGP lenses do not satisfy the dynamic environment inherent to some professional or leisure activities, particularly sport activity. This is a good option to consider in patients with mild to moderate keratoconus and good correction of slight or moderate irregular corneal astigmatism with good tolerance. Aftercare implications are also discussed.

A decade of contact lens prescribing trends in the United Kingdom (1996–2005)

Purpose To document contact lens prescribing trends in the United Kingdom over the past decade (between 1996 and 2005). Methods An annual survey of contact lens prescribing trends was conducted each year by asking a random selection of optometrists and dispensing opticians to provide information relating to 10 consecutive contact lens fits between January and March. Results Over the 10-year survey period, 1251 practitioners returned survey forms representing a total of 12,050 contact lens fits. The mean (±standard deviation) age of lens wearers was 33 ± 13 years of which 64% were female. Over the survey period, rigid lens new fits decreased from 22% to 4%. Low water content lenses reduced from 20% to 2% of new soft lens fits. Soft toric lenses gradually increased to the point where they accounted for the expected proportion of patients with astigmatism ≥1.00DC (i.e. >20% of soft lens fits). Monthly and daily disposable lenses accounted for >90% of all soft lens fits between 2003 and 2005. The proportion of new soft fits and refits prescribed as extended wear has gradually increased, stabilizing at about 5% of new fits and 12% of refits. Multi-purpose lens care solutions increased from 60% of all care systems in 1997 to 91% in 2005. Rigid lenses and monthly replacement soft lenses are predominantly worn on a full time basis, whereas daily disposable soft lenses are mainly worn part time. Conclusions This survey indicates that technological advancements such as the development of new lens materials, manufacturing methods and lens designs have had a significant impact on the contact lens market over a relatively short period of time.

The Clinical Performance of a Silicone Hydrogel Lens for Daily Wear in an Asian Population

To evaluate slitlamp findings, frequency and severity of symptoms, and wearing time with a silicone hydrogel contact lens when used for daily wear by patients of Asian ethnicity. This was a five-site, 88-patient, prospective, open-label study involving 1 month of daily wear of lotrafilcon A lenses (Focus NIGHT & DAY, CIBA Vision, Duluth, GA) among adapted soft lens wearers previously wearing etafilcon A (ACUVUE 2, Johnson & Johnson Vision Care, Jacksonville, FL) or polymacon (Optima FW, Bausch & Lomb, Rochester, NY) lenses. Statistically significant improvements in conjunctival redness, limbal redness, and corneal neovascularization were reported after 1 week and 1 month of wear. Patients reported statistically significant improvements in subjective symptoms of redness, dryness during the day, and dryness at the end of the day. More patients reported increased than reduced average daily wear time and average daily comfortable wear time with the silicone hydrogel lens. Significant improvements in clinical signs and subjective symptoms may occur when some patients of Asian ethnicity wearing conventional hydrogel lenses for daily wear are refitted with silicone hydrogel lenses for daily wear.

Contact lens fitting post‐refractive surgery

Purpose: A number of patients who had undergone refractive surgery still required contact lens fitting. Indications for fitting included the correction of residual ametropia, anisometropia, and regular and irregular astigmatism. In some cases, a post‐treatment therapeutic bandage soft contact lens was used to protect the treated eye and to promote regular epithelial healing. Lens fitting was reviewed to give recommendations for problem solving and fitting this category of patient.Methods: Before lens fitting, a full history and symptoms and refraction were obtained. The practitioner explained the results of the refractive surgery, advised on advantages and limitations of lens wear and described the choices available. The fitting procedure involved anterior segment assessment and measurement of ocular parameters. Several steps were often required to achieve a successful lens fit and tolerance.Three main categories of refractive surgery were outlined: (1) Internal procedure, e.g. implantation of an intra‐ocular lens or a special soft lens draped over the crystalline lens. (2) Corneal incision, e.g. penetrating and lamellar keratoplasty, radial keratotomy (RK), transverse incision for astigmatism reduction, and stromal lens insertion. (3) Laser techniques, e.g. PRK, LASIK, LASEK, Holmium laser and thermo‐keratoplasty.Results: Contact lenses were fitted aiming to cause least disturbance to the cornea which had already been compromised by previous surgery. Good oxygen transmission, surface wettability and lens design were important features. A rigid gas permeable (RGP) lens could support and protect the cornea, provide a corrective tear lens between the lens and the new corneal contour, and help to stabilise visual acuity. Often a RGP lens of large diameter was required to bridge over the contours of the central cornea region and assist lens centration. Good visual acuity was usually achieved unless residual stromal haze prohibited this. A soft lens draped over the cornea gave good comfort and lens centration. However, it was less effective on irregular astigmatism and led to variable visual acuity on RK or over wide laser ablation zones.Conclusion: Fitting the post‐refractive surgery cornea was challenging. Extra time and assessment were recommended as the new corneal topography could lead to problems with contact lens centration and stability of visual acuity. Waiting 3 months post‐treatment to allow the corneal topography to stabilise before commencing fitting is particularly recommended for RK and PRK. Lens aftercare included management of the patients’ high expectations.

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.

Postoperative Endophthalmitis: Caution is the Watchword

Postoperative endophthalmitis is the most feared complication following cataract surgery. It can be caused by infection entering the eye during surgery or by inadequately cleaned instruments. Sterile phaco handpieces might retain remnants of soft lens matter or visco-elastic which might later contaminate other patients, causing inflammation in their eyes. The costs of an endophthalmitis outbreak are heavy, including poor patient outcomes, temporary theatre closure, rising waiting lists and damage to a hospital's reputation. This article raises awareness of endophthalmitis and provides useful recommendations for ophthalmic theatre personnel.

Hydro-chop technique for soft lenses

Chopping techniques were initially developed to expend the least amount of phacoemulsification power inside the eye to remove a lens and to improve efficiency. Soft nuclei are not generally conducive to traditional chopping techniques and have required alternate, energy-consuming techniques, such as sculpting, to be removed. We describe a modified chopping technique that can be used to mechanically cleave soft nuclei into distinct fragments before phaco power is required, reducing total power and energy expended in the eye.

The Incidence of Microbial Keratitis among Wearers of a 30-Day Silicone Hydrogel Extended-Wear Contact Lens

To estimate the incidence of presumed microbial keratitis with and without loss of visual acuity among wearers of a silicone hydrogel contact lens (Lotrafilcon A, Night & Day, CIBA Vision, Inc., Duluth, GA), recently approved for up to 30 days of continuous wear. Prospective cohort postmarket surveillance study. Contact lens wearers (recruited from 131 practices) who had been prescribed the lens for intended continuous wear of as many as 30 nights. The occurrence of a corneal infiltrate was ascertained through a combination of center report and direct contact with participants at 3 and 12 months. Whenever a corneal infiltrate was suspected, study and treatment medical records were systematically reviewed by an Endpoints Committee using a predetermined classification scheme for corneal infiltration. Cases of presumed microbial keratitis were determined based on the constellation of presenting signs and symptoms and clinical course. The incidence of presumed microbial keratitis with and without loss of visual acuity. A total of 6245 participants were recruited between August 13, 2002 and July 2, 2003. Of these, 4999 subjects (80%) completed 12 months of follow-up, and these participants contributed a total of 5561 person years of lens wearing experience. Approximately 80% of participants routinely wore their lenses continuously for 3 or more weeks. The overall annual rate of presumed microbial keratitis was 18 per 10,000 (95% confidence interval (CI): 8.5-33.1). There were 2 cases of presumed microbial keratitis with loss of visual acuity, an annual rate of 3.6 per 10,000 (95% CI: 0.4-12.9), and an additional 8 cases without loss of visual acuity, an annual rate of 14.4 per 10000 (95% CI: 6.1-28.4). The rate of presumed microbial keratitis was lower for users reporting typical wear of 3 or more weeks than for those wearing the lens for less than a 3-week continuous period (P = 0.02). The incidence of loss of visual acuity due to microbial keratitis among users of the silicone hydrogel contact lens was low. The overall rate of presumed microbial keratitis with the wearing schedule of as many as 30 nights was similar to that previously reported for conventional extended-wear soft lenses worn for fewer consecutive nights.

Overnight Corneal Reshaping versus Soft Disposable Contact Lenses: Vision-Related Quality-of-Life Differences From a Randomized Clinical Trial

The purpose of this article is to evaluate patients' visual acuity, symptoms, and perceptions of vision-related quality of life in a randomized crossover clinical trial of overnight corneal reshaping (OCR) and daily wear soft lenses (SCL). Qualified subjects were randomly assigned to wear one mode of contact lens for 8 weeks and then, after a washout period, they wore the alternate mode for 8 weeks. On concluding each contact lens wear mode, subjects completed the NEI-RQL42 questionnaire. During the SCL mode, subjects wore lenses during their waking hours. During the OCR mode, subjects wore lenses only while sleeping. Soft lenses were Biomedics 55 2-week disposable lenses. OCR lenses were CRT lenses by Paragon. (Three subjects were fit with custom-designed OCR lenses in Boston XO material, manufactured by Art Optical.) LogMAR acuity was measured and slit lamp evaluation was performed at specified intervals during follow up. After completing both phases of the study, patients chose which mode they preferred. Of 81 enrolled patients, 65 completed both phases and 16 dropped out during the study. Significant differences (p<0.01) favoring SCL wear included better visual acuity and less trouble with glare. Significant differences (p<0.01) favoring OCR wear included less activity limitations, less trouble with symptoms, and less dependence on refractive correction. Of 65 completing both phases, 44 preferred the OCR lenses and 21 preferred the soft lenses. Subjects who preferred the OCR lenses were less myopic and had steeper K readings at baseline, and showed less difference between visual acuity during OCR wear and visual acuity with SCL. In subjects with mild myopia who experienced both SCL and OCR, better visual acuity and less glare resulted from SCL wear, whereas activity limitations, symptoms, and dependence on refractive correction were less troublesome with OCR wear. When the study was completed, 67.7% chose OCR lenses worn only while sleeping, whereas 32.3% preferred 2-week disposable soft lenses worn during the day as their preferred correction.

Absorptive and tinted contact lens for reduction of glare

PurposeReport four cases of fitness of absorptive and tinted contact lenses as an aid for glare reduction, in subjects with retinal dystrophy, when the use of filter in glasses is not possible or enough. MethodsAbsorptive and tinted contact lenses were fitted in four subjects; two with rod monochromacy and the others with cone dystrophy, with complaints of severe photophobia indoors and outdoors. They were fit with soft absorptive lens, Optolens, polymer polymacon DK 10, 46% water, refraction index of 1.428, dark brown with a amber pupil of 3 mm, in both eyes. ResultsThe subjects immediately reported a positive effect on comfort in seeing, indoors and outdoors. The visual acuity remained unaffected. The color vision and contrast sensitivity showed discreet alterations. ConclusionIn spite of the limited cases, the findings suggest the use of absorptive and tinted contact lenses as an important aid to reduce disability glare for patients with retinal dystrophy.

Changes in water content of high plus hydrogel lenses worn on an extended wear basis in a geriatric aphakic population

Purpose: To investigate the water content of hydrogel lenses of relatively high plus power hydrogel lenses after 3 months extended wear and compare values with unused lenses. Method: Geriatric aphakic extended wear soft lens patients were fitted with one of four different brands of hydrogel lenses (A) Incanto 78 (Cantor and Nissel, UK), (B) PSL72 (Prospect lenses, UK), (C) ES70 (Ocular Sciences), (D) Proclear (Coopervision). After 3 months continuous wear the lens was removed and water content (WC) was determined at both lens surfaces using an Abbé refractometer. The water content was also measured for 40 unused lenses (+10 to +20 D, 10 lenses per brand). Results: One hundred and thirty-two lenses were checked after 3 months extended wear. Mean (±S.D.) WC values for front (f) and back (b) surfaces of worn and unworn lenses were, respectively, (A) Worn ( n = 45): f 73.2(4.13) b 73.8(4.33); unworn f 80.5(0.68) b 81.1 (0.80). (B) Worn ( n = 37); f 70.5(4.49) b 70.9 (3.89); unworn f 72.5(0.94) b 72.3 (0.89). (C) Worn ( n = 34); f 68.3(3.18) b 68.4(3.63); unworn f 70.6 (0.48) b 71.1 (0.55). (D) Worn ( n = 16); f 63.4(3.68) b 63.3(3.19); unworn f 60.9 (1.56) b 61.5 (1.92). There was a significant correlation between WC measured from front and back surfaces ( p < 0.01). In worn A–C lenses, front surface WC tended to be lower than back surface WC. For lenses A and C at both surfaces the WC of worn lenses was significantly lower than unworn lenses ( p < 0.05). For lens D, mean WC of worn lenses was significantly higher than unworn lenses ( p < 0.05). In 80% of B lenses, surface WC of worn lenses were significantly lower than WC of unworn lenses ( p < 0.05). There was no relationship between WC and lens power. Conclusion: On average, A and C lenses tended to desiccate but D lenses tended to swell as did 20% of B lenses. The front surface of worn lenses measured lower water content than the back surface suggesting the front surface is drier than the back. This apparent difference in water content between the surfaces could be an artefact emanating from differential rates of surface deposition.

Corneal Staining and Subjective Symptoms With Multipurpose Solutions as a Function of Time

Short-term changes in corneal staining and ocular symptoms were assessed at defined intervals to evaluate combinations of three soft lenses and four multipurpose solutions. A series of pilot studies were conducted over 11 months using a double-masked, randomized, crossover design. Asymptomatic, adapted, daily-wear soft lens users wore group II or IV soft hydrophilic or silicone hydrogel lenses for a maximum period each day. Before wear, new lenses were soaked overnight in one of four multipurpose solutions: Alcon OPTI-FREE Express MPDS, Bausch & Lomb ReNu MultiPlus Multipurpose Solution, CIBA Vision SOLO-Care PLUS Multipurpose Solution, or AMO Complete MoisturePLUS. Subjects rated comfort and ocular symptoms. Corneal staining type and area were evaluated at baseline and after lens removal. Significantly increased extent of corneal staining, defined as the proportion of corneal zones showing staining of grade 1 or more severe, was observed at 1 and 2 hours when subjects wore group II lenses soaked in the polyhexamethylene biguanide-based systems. Significantly increased extent of staining was observed at 2 hours when subjects used silicone hydrogel lenses soaked in regimen 4. When subjects used regimen 1 and wore group II lenses, only a minimal staining response was observed at 1 and 2 hours of wear. Significant symptoms were not correlated with extent of staining. This study design is a promising tool that can discriminate between the performance of different soft lens and multipurpose solution combinations rapidly using small patient samples. With some lens-care product combinations, corneal appearance may vary according to the time of day the patient is examined.

Comparative Clinical Performance of Rigid versus Soft Hyper Dk Contact Lenses Used for Continuous Wear

The purpose of this study is to investigate the comparative clinical performance of two hyper Dk contact lenses: a silicone hydrogel lens (Focus Night & Day, Ciba Vision) and a rigid lens (Z-alpha, Menicon Co. Ltd.) when worn for up to 30 days of continuous wear (CW). The rigid lens was worn on an unplanned replacement basis, whereas the soft lens was replaced monthly. One hundred subjects were recruited. Fifty neophyte subjects were randomly assigned into one of the lens types (25 subjects per lens type). Twenty-five existing daily wear (DW) rigid lens users wore the rigid study lens and 25 existing DW soft lens users wore the soft study lens. Visual acuity, lens fit, keratometry, refraction, lens surface assessment, physiological response, and subjective response were investigated at baseline and after 1 week of DW and 24 hours, 1 week, and 1, 3, 6, 9, and 12 months of CW. Analysis compared lens type (rigid vs. soft) and subject group (experienced vs. neophyte). Sixty-eight subjects completed the study. Visual acuity was similar for the two lens types and subject groups. Lens fit was judged to be adequate in all subjects. Corneal curvature of subjects in the rigid groups became flatter by 0.13 mm compared with 0.04 mm for subjects in the soft lens groups (F = 14.7, p = 0.0003); the refractive findings mirrored these corneal changes. The increasing rate of deposition on rigid lenses was consistent with the fact that these lenses were not replaced during the study. Conjunctival hyperemia and staining were similar for the two lens types but greater among experienced wearers at baseline (F = 13.8, p = 0.0005; F = 5.3, p = 0.02, respectively). Corneal staining was higher for the rigid lens wearers (F = 5.6, p = 0.02) but this was mainly the result of the initial higher scores in the rigid lens experienced group. The change in papillary conjunctivitis was greater for subjects in the soft lens groups than rigid lens groups (F = 4.6, p = 0.04). Comfort was initially lower for the rigid lens neophyte group (F = 4.2, p = 0.0001), but after the CW phase started, there were no differences between groups. Notwithstanding subtle differences in physiological responses, continuous wear hyper Dk rigid and soft silicone-containing contact lenses can be successfully worn by both those with previous contact lens experience and those with no history of contact lens wear.