The frequency of ocular symptoms during spectacle and daily soft and rigid contact lens wear.

PURPOSE: Ocular discomfort is the primary reason for discontinuation of contact lens wear. The purpose of the study was to quantify and compare the frequency of ocular symptoms experienced by spectacle wearers and wearers of soft and rigid daily contact lenses. METHODS: We analyzed the results of an ocular symptom survey of prospective volunteers for contact lens clinical trials during the period 1989 to 1995. Questions pertaining to lens-wear experience and ocular symptoms were answered by 883 untrained individuals without active ocular disease. The sample included 664 spectacle wearers, 171 soft contact lens (SCL) wearers, and 48 rigid gas-permeable (RGP) lens wearers. The frequencies of 10 ocular symptoms were compared for each group. Spearman's Rank Correlation was used to test for correlations between symptoms. The chi2 test was used to determine differences between subject groups, adjusted for multiple comparisons. RESULTS: There were no significant differences in the frequency of ocular symptoms between the soft contact lens (SCL) and RGP wearers. The most common symptom was ocular tiredness (27%). None of the symptoms were highly correlated, indicating that they are somewhat different "sensations." Despite ocular discomfort being the primary reason for discontinuation of lens wear, contact lens wearers experienced the same type and severity of symptoms as spectacle wearers. Thus (in order of frequency of occurrence), tiredness, itchiness, watering, pain, aching, excessive blinking, and burning had similar rates of occurrence for all three groups. The two major distinguishing symptoms were dryness and redness, which were reported far more frequently and with greater severity in both contact lens groups (p < 0.001). Grittiness was also reported more with RGP wearers than with spectacle wearers (p < 0.001). CONCLUSIONS: Contact lenses disturb the ocular environment, as evidenced by responses of increased ocular dryness, redness, and grittiness. Despite fundamental differences in SCL's and RGP contact lenses, both groups of contact lens wearers surveyed experienced a similar type and frequency of ocular symptoms.     

Visual acuity in contact lens wearers.

PURPOSE: The difference between high- and low-contrast visual acuity provides a sensitive indicator of vision loss in ocular disease; however, the effect of refractive error correction on this difference is still debated. METHODS: High- and low-contrast visual acuity was measured in 116 rigid gas permeable contact lens wearers, 51 spectacle wearers, and 50 soft contact lens wearers with habitual and best correction. Twenty-nine of the soft contact lens wearers reported that they wore disposable contact lenses (discarded on a monthly or more frequent basis), whereas the other 21 soft contact lens wearers wore traditional soft contact lenses. RESULTS: Rigid gas permeable contact lens wearers had statistically worse high-contrast habitual visual acuity than spectacle wearers (Tukey-Kramer, p = 0.0075). Traditional soft contact lens wearers had significantly worse low-contrast visual acuity compared with all other groups (Tukey-Kramer, p < 0.02 for each comparison). Traditional soft contact lens wearers had a significantly larger difference between high- and low-contrast visual acuity with best correction compared with rigid gas permeable wearers (Tukey-Kramer, p = 0.0099). CONCLUSIONS: Rigid gas permeable contact lens wearers had statistically worse habitual high-contrast visual acuity compared with spectacle wearers, but no difference was present under best-corrected conditions. We hypothesize that rigid gas permeable contact lens wearers were not wearing their optimal correction habitually. Traditional soft contact lens wearers had significantly worse low-contrast visual acuity. They also had a larger difference between their best-corrected high- and low-contrast visual acuity scores compared with rigid gas permeable contact lens wearers.     

Keratocyte density in keratoconus. A confocal microscopy study(a)

PURPOSE: To estimate keratocyte density in human corneas with keratoconus by confocal microscopy. DESIGN: Prospective, observational cohort study. METHODS: Twenty-nine unscarred corneas of 19 patients with keratoconus and 29 corneas of 19 controls matched for age (+/-3 years) and contact lens wear were examined by using confocal microscopy. Images were recorded from the full-thickness central cornea. A masked observer manually counted bright objects (keratocyte nuclei) in images without motion blur. Cell densities in anteroposterior stromal layers of keratoconus corneas were compared with densities in corresponding layers of control corneas. RESULTS: In keratoconus patients, age 40 +/- 15 years (mean +/- standard deviation), keratocyte density was 19% lower in those who wore contact lenses (16,894 +/- 4032 cell/mm(3), n = 12) than in those who did not wear contact lenses (20,827 +/- 4934 cell/mm(3), n = 17, P =.03). In control patients, age 39 +/- 16 years, there was no difference in keratocyte density between those who wore contact lenses (n = 12) and those who did not wear contact lenses (n = 17, P =.80). Among contact lens wearers, keratocyte density was 25% lower in keratoconus corneas (16,894 +/- 4, 032 cell/mm(3), n = 12 [9 = rigid gas-permeable lenses, 3 = soft lenses]) than in control corneas (22,579 +/- 2, 387 cell/mm(3), n = 12 [3 = rigid gas-permeable lenses, 9 = soft lenses], P =.002), the result of cell density being lower in the most anterior keratocyte layer (P =.001) and the layers between 0% to 10% (P <.001), 67% to 90% (P <.001), and 91% to 100% (P <.001) of stromal thickness. Among noncontact lens wearers, there was no difference in cell density between keratoconus and controls (P =.41). CONCLUSION: Keratocyte density is decreased in the anterior and posterior stroma of keratoconus patients who wear contact lenses.     

Visual acuity,spectacle blur and slit-lamp biomicroscopy on asymptomatic contact-lens-wearing recruits

Refraction data of 644 Dutch Army and Air Force recruits wearing contact lenses or spectacles were statistically compiled and correlated with the type of lenses worn. Visual acuity with contact lenses was far from optimal because the power of the lenses was incorrect or the optical quality poor. This applied particularly to soft contact lenses. On the other hand, spectacle blur was rare with soft lenses and less evident with gas-permeable hard lenses compared with conventional hard lenses. Less corneal staining occurred with gas-permeable hard lenses compared with conventional hard lenses (P=0.02). Corneal neovascularization, conjunctival hyperaemia, papillary changes in the tarsal conjunctiva, corneal opacifications and ghost vessels were seen more often in wearers of soft rather than hard lenses. In this study, in which we examined objective parameters of contact lens efficiency, the gas-permeable hard lenses appeared most favourable.     

Fitting contact lenses after myopic keratomileusis

PURPOSE: To evaluate the long-term efficacy and results of contact lens fitting following myopic keratomileusis (MKM). SETTING: Department of Ophthalmology, Manhattan Eye, Ear, and Throat Hospital, and Swinger Vision Center, New York, New York, USA. METHODS: Postoperative fitting of contact lenses was studied as part of a prospective evaluation of myopic keratomileusis. In this series, 27 eyes of 20 patients had residual postoperative refractive errors that were corrected with contact lenses. Patients were fit at a mean of 9.4 months after surgery by the trial-lens method. Preoperative keratometry readings and refractions, as well as postoperative keratometry readings, refractions, and contact lens specifications, were recorded and used for fitting. RESULTS: Twenty-six eyes (96%) were fit successfully: 24 (89%) with rigid gas-permeable lenses and 2 (7%) with daily-wear soft lenses. The mean diameter of the rigid lenses was 10.00 mm (range 9.4 to 11.0 mm) and the mean base curve, 8.52 mm (range 7.9 to 9.2 mm). The 2 soft lenses had base curves of 8.6 and 8.9 mm. The mean lens power was -5.24 diopters (D) (range -0.37 to -14.75 D), which was, on average, 4.06 D more myopic than the postoperative spectacle refraction. Postoperative keratometry provided a good starting point for the trial lens. Lenses were tolerated for up to 16 years. One eye, fit with a soft lens, developed significant myopia during the fifth year. CONCLUSION: After lamellar refractive surgery, the topography of the cornea is significantly altered. Although the postoperative keratometry readings are steeper than the actual curvature, they are reasonably reliable for determining the base curve of the initial trial lens, validating the use of conventional methods of fitting rigid contact lenses in patients who have had MKM.     

A comparison of spectacle and contact lens wearing times in the ACHIEVE study

Purpose: The aim was to compare vision correction wearing time between myopic children and teenagers in a clinical trial of contact lenses and spectacles. Methods: Parents of subjects in the Adolescent and Child Health Initiative for Vision Empowerment (ACHIEVE) study provided wearing times for spectacle and contact lens wear. Hours wearing primary correction and total correction were compared between the two treatment groups. Other factors hypothesised to be associated with wearing time were analysed. Results: The average wearing time of the primary correction differed significantly with the wearing time for the spectacles group being 91.5 hours per week compared to 80.3 hours per week for the contact lens wearers (p < 0.0001). Total correction time was slightly higher for the contact lens wearers, 97.5 hours per week, after accounting for time wearing spectacles. Higher refractive error was strongly related to longer wearing times (p < 0.0002). Age and treatment group were associated with wearing time (p = 0.005). Young contact lens wearers wore their lenses less than young spectacle wearers and older contact lens wearers. Low scores on an appearance quality‐of‐life scale were associated with longer wearing time in spectacle wearers compared to the low‐ and high‐scoring contact lens wearers. Gender, spectacle satisfaction and activities were not related to wearing time. Conclusions: While contact lens wearers, on average, wear their contact lenses less than spectacle wearers, they spend roughly the same amount of time wearing a refractive correction. Higher refractive error resulted in longer wearing times for both spectacle and contact lens wearers. Younger contact lens wearers wore their contact lenses for shorter periods than the spectacle wearers, but still wore them, on average, 74.4 hours per week (about 10 hours per day), suggesting that contact lenses are a viable alternative mode of correction for children.     

Quality of life after wearing multifocal contact lenses for myopia control for 2 weeks in the BLINK Study

Purpose

To validate Pediatric Refractive Error Profile 2 (PREP2) subscales that can be used to evaluate contact lens wearers and compare vision-specific quality of life measurements between children wearing multifocal and single vision contact lenses for 2 weeks.

Methods

Two hundred and ninety-four myopic children aged 7–11 years (inclusive) were enrolled in the 3-year, double-masked Bifocal Lenses In Nearsighted Kids (BLINK) Study. Participants completed the PREP2 survey after having worn contact lenses for 2 weeks. The Vision, Symptoms, Activities and Overall PREP2 subscales were used to compare participants' subjective assessment while wearing +1.50 or +2.50 D add multifocal or single vision contact lenses. Rasch analysis was used to validate each subscale and to compare participants' subjective assessment of contact lens wear.

Results

Item fit to the Rasch model was good for all scales, with no individual items having infit mean square statistics outside the recommended range (0.7–1.3). Response category function was acceptable for all subscales, with ordered category thresholds. Measurement precision, assessed by the Rasch person reliability statistic, was less than ideal (≥0.8) for three of the subscales, but met the minimum acceptable standard of 0.5. Scores for the Vision subscale differed by treatment assignment (p = 0.03), indicating that participants with the highest add power reported statistically worse quality of vision, although the difference was only 3.9 units on a scale of 1–100. Girls reported fewer symptoms than boys (p = 0.006), but there were no other differences between boys and girls.

Conclusions

Rasch analysis demonstrates that the PREP2 survey is a valid instrument for assessing refractive error-specific quality of life. These results suggest that vision-related quality of life is not meaningfully affected by 2 weeks of soft multifocal contact lens wear for myopia control.     

A summary of the findings from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. CLEK Study Group.

BACKGROUND: This summary of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study includes the study design and results to date. METHODS: The CLEK Study is a longitudinal, observational study of 1,209 patients with keratoconus. The study's main outcome measures are corneal scarring, visual acuity, corneal curvature, and quality of life. RESULTS: These patients' mean age at baseline was 39.3 +/- 10.9 years, and they had moderate to severe keratoconus. Ninety-five percent of the patients had steep keratometric readings of at least 45 D, and 78% had best-corrected visual acuity of 20/40 or better in both eyes. Sixty-five percent of the patients wore rigid gas-permeable contact lenses in both eyes, and most of those (73%) reported that their lenses were comfortable. Most rigid gas-permeable contact lens wearers were fitted with apical touch (88%). Fifty-three percent had corneal scarring in one or both eyes, and corneal scarring was associated with corneal staining, contact lens wear, age, the presence of a Fleischer's ring, and a steeper cornea. Corneal scarring was associated with decreased high- and low-contrast visual acuity. CONCLUSIONS: These results characterize keratoconus patients as rigid gas-permeable contact lens wearers with moderately steep corneas. Corneal scarring is associated with decreased vision in keratoconus.     

On-eye evaluation of optical performance of rigid and soft contact lenses.

A Shack-Hartmann aberrometer was used to assess the optical performances of eyes corrected with rigid or soft contact lenses compared with spectacles. Metrics of optical quality derived from the measured wave aberrations were consistent with the subjective rating of visual clarity by subjects. Optical aberration analysis illustrated the differences in aberration structures of eyes wearing different optical corrections. For our subjects, correction with a rigid gas-permeable lens yielded significantly better optical quality than did the soft contact lens or spectacle lens. This was due to a reduction in the eye's asymmetric (odd-order) aberrations and a reduction in the amount of the eye's positive spherical aberration. These observations can be explained by theoretical calculations of the aberrations of the eye plus lens optical system. We conclude that aberrometry provides a better understanding of the optical effects of contact lenses in situ and could be useful for optimizing future designs of contact lenses.     

Glare and halo with refractive correction

Background: The aim of this investigation was to compare glare and halo with various methods of refractive correction. Methods: Ninety‐eight eyes of healthy pre‐presbyopes were analysed for the presence of glare and halo using computer‐generated stimuli. Subjects were divided into three groups: emmetropes without correction, single vision plastic lens spectacle wearers (with clean and dirty lenses) or single‐vision soft contact lens wearers. Results: No significant difference in glare was found among groups. Significant differences were noted in halos between emmetropes and both contact lens (p < 0.001) and uncleaned spectacle groups (p < 0.05) but not with cleaned spectacles. The reduction in halo size after cleaning the lenses was significant (p < 0.0187). Conclusions: Contact lens and unclean spectacle wearers both have significantly larger halos than emmetropes and those wearing cleaned spectacle lenses. Unclean spectacles may affect the accuracy of results in psychophysical and clinical testing.     

Adverse events and discontinuations with rigid and soft hyper Dk contact lenses used for continuous wear.

PURPOSE: The purpose of this study was to assess the relative clinical success of hypertransmissible rigid and soft contact lenses in terms of the rates of adverse events and clinical discontinuations. METHODS: One hundred subjects (50 experienced wearers and 50 neophytes) were fitted with either the Z-alpha lens (Menicon) or the Focus Night & Day lens (CIBA Vision), which were worn on a 30-day continuous wear basis. The rates of adverse events and clinical discontinuations were monitored over 12 months. RESULTS: There were 20 adverse events that were categorized as being serious or significant--four with rigid lenses and 16 with soft lenses (p = 0.003). There was no significant difference between the experienced (10) and the neophyte (10) groups (p = 1.00). There were 23 clinical discontinuations--13 with rigid lenses and 10 with soft lenses (p = 0.46). Fewer experienced wearers (five) discontinued than neophytes (18) (p = 0.002). CONCLUSIONS: Practitioners should anticipate fewer adverse events with rigid versus soft lenses prescribed for continuous wear. Experienced wearers are less likely to discontinue compared with neophytes.     

Preoperative screening of contact lens wearers before refractive surgery.

PURPOSE: To evaluate corneal stability, measured by computerized videokeratography (CVK) after discontinuation of contact lens wear in preoperative refractive surgery candidates. SETTING: Baylor College of Medicine, Cullen Eye Institute, Houston, Texas, USA. METHODS: Topographic differences were analyzed in 136 noncontact lens wearers (NCLW) and 76 contact lens wearers (CLW) (18 rigid gas-permeable contact lenses [RGPCL], 58 soft contact lenses [SCL]) using EyeSys CVK after discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks. RESULTS: There were no differences in CVK patterns between the NCLW and the CLW groups. There were no statistically significant differences between the 2 groups in topographic symmetry, asphericity, corneal uniformity index, predicted corneal acuity, and irregular astigmatism. The dioptric range for the axial and the profile difference maps in the CLW group was slightly lower than in the NCLW group. CONCLUSIONS: For patients whose manifest refraction and CVK maps were within 0.5 diopters of earlier values, discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks was adequate for the cornea to return to its baseline topographic state.     

The contact lens and myopia progression (CLAMP) study: design and baseline data.

BACKGROUND: Although previous contact lens myopia control studies indicate that rigid contact lenses slow the progression of myopia in children, they have all suffered from limitations that challenge the significance of their results. The Contact Lens and Myopia Progression (CLAMP) Study addresses the limitations of previous studies and attempts to correct them by implementing alternative Study designs. The CLAMP study also measures all the ocular components to examine the potential mechanism of treatment effect. METHODS: Eligible children were fitted with rigid gas-permeable contact lenses and enrolled in a run-in period to determine whether they were able to adapt to rigid contact lens wear. Subjects who successfully completed the run-in period were randomly assigned to wear rigid contact lenses or soft contact lenses for the remainder of the 3-year study. The primary outcome measure will be the 3-year change in cycloplegic autorefraction; the secondary outcome measures will include the 3-year change in axial length, peripheral autorefraction, crystalline lens curvatures, corneal curvature and thickness, accommodation, and intraocular pressure, which are being measured annually. RESULTS: We examined 148 eligible subjects who participated in the run-in period. Of the 148 eligible subjects, 116 (78.4%) were able to adapt to rigid contact lens wear and were enrolled in the CLAMP Study. The mean age of the participants at the baseline visit was 10.5 years, and 59.5% were girls. At the randomization visit, the mean (+/-SD) spherical equivalent refractive error in the right eye was -2.09 +/- 0.89 D, the mean central curvature of the right cornea by videokeratography was 44.5 +/- 1.3 D, and the mean axial length of the right eye was 24.13 +/- 0.71 mm. CONCLUSIONS: Four of five children aged 8- to 11-years-old were able to adapt to rigid gas-permeable contact lens wear. The CLAMP Study aims to further clarify the effect of rigid gas-permeable contact lenses on myopia progression in children.     

Comparison of tear-film osmolarity in different types of contact lenses.

PURPOSE: To investigate the tear-film osmolarity of contact lens wearers for different types of contact lenses. METHODS: Fifty six eyes of 56 cases were evaluated in four different groups according to the type of contact lens worn, with 14 eyes in each group. Groups 1 and 2 consisted of subjects who wore frequent-replacement daily wear soft contact lenses; group 1 lenses had 55% water content, and lenses in group 2 had 38% water content. Groups 3 and 4 consisted of subjects who wore rigid gas-permeable contact lenses, with a Dk value of 90 in group 3 and a Dk value of 52 in group 4. Tear-film osmolarity values in milliosmole (mosm) units were determined by auto-osmometer (Orstat 6030, Daiichi Kagacu, Kyoto, Japan) before and after contact lens wear for each group, and the results were compared statistically by ANOVA test. RESULTS: Before the period of contact lens wear, the tear-film osmolarity values of group 1, 2, 3, and 4 were 283.61+/-12.83 mosm, 285.23+/-8.94 mosm, 285.57+/-11.39 mosm, and 280.15+/-12.07 mosm, respectively. After the period of contact lens wear, these values were measured at 312.15+/-16.03 mosm in group 1, 316.54+/-12.14 mosm in group 2, 313.14+/-9.66 mosm in group 3, and 316.38+/-11.60 mosm in group 4. Although the difference between the values before and after the period of contact lens wear was statistically significant for each group (F=291.45; P=0.0005), there was no statistically significant difference among the groups. CONCLUSIONS: When a contact lens is placed in the eye, the lens alters the normal structure of the tear film and affects its rate of evaporation; therefore tear-film osmolarity may increase. In our study, all contact lenses produced a similar effect on tear-film osmolarity.     

Effect of soft contact lenses on the measurements of intraocular pressure with non-contact pneumotonometry

PURPOSE: To evaluate the effect of soft contact lenses with different lens power on the measured value of the intraocular pressure with non-contact pneumotonometry. METHODS: 120 eyes (80 healthy volunteers: 50 women, 30 men, aged 22 to 61 years) were included in this study. Intraocular pressure was measured with a pneumotonometer Canon X-10 before and after insertion of the Ciba Vision Focus Night&Day soft contact lens. We used contact lenses with different lens power of + 0.25 D, + 1.00 D, + 4.00 D, - 1.00 D, and - 4.00 D. The averages of three measurements were taken as representative IOP values that were statistically evaluated. RESULTS: IOP measured over myopic lenses of - 1.00 and - 4.00 D showed lower values within the mean range of 1 mm Hg. The difference between the measurements over the myopic lenses was mostly smaller than +/- 2 mm Hg (78% when using - 1.00 D and 90% when using - 4.00 D contact lens). All the differences using + 0.25 D contact lens were smaller than +/- 2 mm Hg. The difference was considerably higher in measurements over + 1.00 and + 4.00 hyperopic contact lenses and showed strong increase with the lens power. CONCLUSIONS: In our study we showed that intraocular pressure can be reliably measured with non-contact pneumotonometry over myopic lenses or hypermetropic lenses with small lens power. This suggests that non-contact pneumotonometry is a useful method in patients wearing therapeutic contact lenses and contact lens wearers who, when measuring the eye pressure, would not need to remove the contact lenses before the examination.     

Oxygen transmissibility of piggyback systems with conventional soft and silicone hydrogel contact lenses

PURPOSE: To investigate the apparent oxygen transmissibility of various piggyback systems using conventional and silicone hydrogel soft contact lenses of different water content and permeability, rigid poly(methyl methacrylate), and rigid gas-permeable lenses of medium, high, and ultrahigh oxygen permeability. The aim of the study was to establish which material (rigid or hydrogel) is more representative of the resulting oxygen performance of piggyback systems. METHODS: The apparent oxygen transmissibility of 66 piggyback systems was measured with an electrochemical method. Eighteen of these combinations involved the use of silicone hydrogel contact lenses currently available. One hyperpermeable rigid gas-permeable contact lens (tisilfocon A) was also included in the study. RESULTS: Measured apparent transmissibility correlates with rigid lens permeability (r = 0.403; SE = +/-3.03 barrer/cm; P < 0.001) and hydrogel lens permeability (r = 0.334; SE = +/-3.2 barrer/cm; P < 0.001). As expected, a linear model comprising permeability values from both rigid and soft materials gave a more precise estimation of the piggyback transmissibility (r = 0.736; SE = +/-2.02 barrer/cm; P < 0.001). The highest values of apparent oxygen transmissibility were found for the combination of tisilfocon A rigid material with any of the 3 silicone hydrogel lenses. Tisilfocon A material significantly improved the transmissibility of all piggyback systems even when conventional hydrogels are involved. CONCLUSION: The combination of hypertransmissible rigid gas permeable lenses with silicone hydrogel soft materials should result in normal corneal function under daily wear conditions. When fitting piggyback systems, clinicians must be aware of material selection to optimize oxygen performance. This is of particular importance in already compromised corneas.     

The performance of the refractive status and vision profile survey in a contact lens clinical trial

OBJECTIVE: To evaluate the Refractive Status and Vision Profile (RSVP) questionnaire in a contact lens clinical trial and to assess the feasibility of its use in future trials. DESIGN: Randomized, crossover clinical trial and survey. PARTICIPANTS: The RSVP was administered to 50 contact lens-wearing participants recruited from a large contact lens clinic. METHODS: RSVP scores were calculated for subjects at three outcome visits: (1) baseline, (2) after wearing daily disposable contact lenses, and (3) after wearing disposable extended wear contact lenses. One-sample t tests were used to compare baseline survey scores with those previously reported for the instrument. The relation of survey scores within and between subjects was assessed with repeated measures analysis of variance. Statistical power and sample size calculations were performed to determine the number of subjects required in future studies to detect differences in RSVP subscale scores. MAIN OUTCOME MEASURES: Eight subscale scores (concern, driving, expectations, glare, optical problems, physical and social functioning, problems with corrective lenses, and symptoms) and the overall RSVP score were calculated on the basis of guidelines reported for scoring of the instrument. RESULTS: Five of eight mean subscale scores (concern, expectations, driving, optical problems, and problems with corrective lenses) and the overall score were significantly lower than those previously reported. No differences were found in the following subscales after contact lens treatment: concern, expectations, physical and social functioning, driving, optical problems, problems with corrective lenses, or the overall RSVP score. Significant differences were found on the symptoms (P = 0.03) and glare (P = 0.05) subscales; post hoc testing revealed that the significant differences in these scores occurred between baseline and daily disposable lens wear and not between treatment modalities (daily disposable and disposable extended wear). A sample size of 420 would be required to find clinically relevant significant differences (25%) for all subscales in a similar one-sample clinical trial. A more restrictive difference (10%) would require more than 1100 subjects for four of the nine subscales. CONCLUSIONS: The RSVP questionnaire may not be the appropriate quality-of-life instrument for use in a contact lens clinical trial. The instrument seems to lack sensitivity and discriminative validity in evaluating contact lens treatments.     

In vivo confocal microscopy: increased conjunctival or episcleral leukocyte adhesion in patients who wear contact lenses with lower oxygen permeability (Dk) values

PURPOSE: Contact lens wear is known to threaten the health of the ocular surface. In vivo confocal microscopy (IVCM) to visualize leukocyte rolling and extravasation in inflammation was recently described. We tested the hypothesis that contact lens wear is associated with measurable inflammation in superficial vessels. METHODS: Leukocyte rolling and sticking (hallmarks of the inflammatory process) were recorded by IVCM. IVCM was performed on conjunctival or episcleral blood vessels bilaterally on 55 contact lens wearers (15 male, 40 female) and 22 non-contact lens wearers (8 male, 14 female). Data were analyzed in 2 ways. Considering each vessel as an independent variable resulted in 132 analyzable vessel segments (13 daily disposable contact lenses, 67 traditional contact lenses, 14 rigid gas-permeable lenses, and 38 controls). Considering each subject as an independent variable resulted in analyzable data for 47 subjects (5 daily disposable contact lens wearers, 22 traditional contact lens wearers, 5 rigid contact lens wearers, and 15 control patients). Free-flowing, sticking, and rolling cells were counted in the vessels. Multiple parameters including mean flow velocity, shear rate, rolling cells/mm/min, and sticking cells/mm were calculated. RESULTS: We found no significant difference in leukocyte adhesion between control patients and patients wearing daily disposable, traditional disposable, or rigid gas-permeable lenses in both types of statistical analyses. However, the data regarding vessel segments as an independent variable show that there were more rolling cells in patients who wore contact lenses with oxygen permeability values (Dk) less than 10 as compared to those who wore contact lenses with oxygen permeability values greater than 16 (P < 0.01) or compared to controls (P < 0.01). CONCLUSION: IVCM is a novel, powerful technique to recognize a critical but subclinical component of inflammation. Although our data indicate that contact lens wear does not markedly increase rolling and sticking of leukocytes in conjunctival or episcleral vessels, there may be subclinical inflammation in association with lenses with the lowest oxygen permeability.