Volume 30, Issue 1, Pages 23-28 (March 2007)

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ABSTRACT

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Initial comfort of lotrafilcon A silicone hydrogel contact lenses versus etafilcon A contact lenses for extended wear☆

published online 22 December 2006.

Abstract

Purpose

To compare the initial comfort afforded by silicone hydrogel lenses (lotrafilcon A) versus the comfort afforded by conventional hydrogel lenses (etafilcon A) in extended wear (EW).

Design

Prospective, double-masked and randomized controlled trial.

Methods

Lotrafilcon A and etafilcon A contact lenses were eye randomly fitted on an EW basis for 7 days and nights in 20 subjects. A forced-choice subject preference questionnaire was made. Subjects were comfort, dryness, red eye and visual quality after night wear and at the end of the day. Subjective scored satisfaction (scale: 1–5) and lens preference were assessed.

Results

Lotrafilcon A proved more comfortable after night wear (60%, CI95% 38–82%) and at the end of the day (70%, CI95% 49–90%) than etafilcon A after night wear (10%, CI95% 0–23%, P<0.05) and at the end of the day (20%, CI95% 2–38%, P<0.05). The feeling of dryness was more marked with etafilcon A after night wear (50%, CI95% 27–72%) and at the end of the day (50%, CI95% 27–72%) than it was with lotrafilcon A (15%, CI95% 0%–31%) after night wear (P>0.05) and at the end of the day (25%, CI95% 5%–44%, P<0.05). General satisfaction with the lotrafilcon A lens was 3.65 points (CI95% 3–4.2) and with etafilcon A 2.95 points (CI95% 2.5–3.3, P<0.05). Eighty percent (CI95% 62%–98%) of subjects preferred lotrafilcon A (P<0.05) for EW.

Conclusions

In EW, lotrafilcon A contact lenses were more comfortable and led to less dryness after night wear and at the end of the day than etafilcon A contact lenses.

Keywords: Silicone/hydrogel soft lens, Extended wear, Subject satisfaction

Article Outline

• Abstract

• 1. Introduction

• 2. Materials and methods

• 2.1. Subjects

• 2.2. Lenses

• 2.3. Questionnaire

• 2.4. Procedures

• 2.5. Data analysis

• 3. Results

• 3.1. Forced-choice contact-lens preference

• 3.2. Subjective scored satisfaction analysis

• 3.3. Answer validation

• 3.3.1. Comfort questions

• 3.3.2. Dryness questions

• 3.3.3. Red eye questions

• 3.3.4. Vision quality questions

• 3.3.5. General score questions

• 3.3.6. Dry-environment questions

• 4. Discussion

• 4.1. Study design

• 4.2. Dryness

• 4.3. Comfort

• 4.4. Red eye

• 4.5. Vision quality

• 4.6. Questionnaire validation

• Conflict of interest

• Acknowledgment

• References

• Copyright

1. Introduction

Extended wear (EW) with low-Dk soft contact lenses provides a good level of clinical performance in vision and comfort [1], [2]. But these lenses can compromise corneal physiology and induce severe adverse reactions. A considerable risk to vision exists [3], [4], [5], [6], [7], [8]. The high oxygen transmissibility of silicone hydrogel materials has been shown to effectively eliminate the short-term impact of EW on the physiology of the cornea [1]. The silicone hydrogel materials also provide a better physiological environment than a typical hydrogel material during EW [1], [9]. But like other HEMA-based hydrogel lenses, silicone hydrogel lenses show bacterial contamination during asymptomatic wear [10].

The physical properties of silicone hydrogel (increased elasticity modulus, plasma surface treatments, water content and edge design) and other complications (such as papillary conjunctivitis, corneal infiltrates, superior epithelial arcuate lesions [SEALs], front surface deposits, poor lens wettability and number of mucin balls) can cause poor tolerance, red eye, deposits and discomfort, as some wearers of silicone hydrogel contact lenses have complained [1], [11], [12], [13], [14], [15]. Subjects reported initial discomfort or dryness with some types of these lenses. Surveys of former contact-lens wearers have shown that dryness and discomfort were the primary reasons why many ceased wearing lenses [16]. The feeling of dryness is related to a variety of factors and (with or without contact lenses) there is no clear relationship between symptoms and clinical signs [17]. Various questionnaires have been used to determine the opinion of patients who wear contact lenses and the patients’ reasons for continuing to use them [16], [18]. The purpose of this paper is to present the results of a prospective, double-masked, randomized and controlled study of the initial comfort of contact lenses made of lotrafilcon A (a silicone hydrogel material) and etafilcon A. The results of the test indicate the overall lens preference for EW.

2. Materials and methods

The study was a prospective, double-masked and randomized, controlled trial.

2.1. Subjects

Twenty subjects, all 18 years or older and with vision correctable to 20/20 in each eye, were enrolled in the study. Subjects with an active ocular surface were excluded (Table 1). Eleven subjects were wearers of contact lenses (two RGP and nine soft contact lenses). Informed consent was received from all subjects. The study was approved by the Human Sciences Ethical Committee of the University of Valladolid in Spain. All subjects were treated in accordance with the Declaration of Helsinki.

Table 1.

Summary of exclusion criteria

	Significant dry eye
	Papillary conjunctivitis
	Corneal opacities
	Current medication that could affect ocular physiology
	Astigmatism (>2.00D)
	Previous EW history

2.2. Lenses

Subjects were randomly assigned to EW with a lotrafilcon A (Focus Night & Day, CIBA Vision) lens on one eye and the etafilcon A (Acuvue 2, Johnson & Johnson Vision Care) lens on the contralateral eye for 7 days. The parameters of the lenses used in this study are listed in Table 2.

Table 2.

Nominal contact-lenses parameters


Lens type	Base curve (mm)	Lens diameter (mm)	Central thicknessa (mm)	Water content (%)	Dk	Power (DP)
Lotrafilcon A	8.60	13.80	0.080	24	175	+2.00 to −4.75
Etafilcon A	8.40–8.80	14.00	0.084	58	33	+2.00 to −4.75

Central thickness: −3.00DP.

2.3. Questionnaire

A forced-choice questionnaire asked the subjects to analyze their preferences regarding contact lenses. The questionnaire contained seven questions. One was about the previous use of contact lenses. Five were forced-choice questions about comfort, dryness, red eye and visual quality after night wear and at the end of the day. There were four choices: right eye, left eye, both eyes or neither eye. The last question was about the lens of choice (right or left eye). Subjects could choose one item only. Finally, there were two subjective scored satisfactions (general satisfaction and dry environment) for each eye. The subjective satisfaction scale ran from 1 (very dissatisfied) to 5 (very satisfied). A masked investigator gave the forced-choice questionnaire to each subject on the seventh day of lens wear. Another masked investigator analyzed the answers.

2.4. Procedures

Each subject in the study wore both lenses simultaneously. An independent investigator made the lenses’ randomization. Another independent investigator fitted the contact lenses with a 48-h washout period (no wearing of contact lenses). Contact lenses were fitted with the flatter base curve in both eyes. The fit of each lens was checked, and the postlens tear film was examined to ensure that no debris was present. No subjects were able to remove their lenses temporarily. No solution or artificial tears were used in the study.

Lenses and ocular health were evaluated on the first, third and seventh day by another independent investigator.

2.5. Data analysis

Statistical analysis was performed using the SPSS 13.0 statistical package for Windows. An exact chi-square goodness-of-fit test was calculated to verify the homogeneity proportions of subjects who indicated a preference for each lens type in a forced-choice questionnaire. A paired Wilcoxon signed-rank test analyzed subjective scored satisfaction (general and dry environment). A Kruskal–Wallis ANOVA nonparametric test was calculated to compare independent data. We analyzed the validity of the answer with the contingency table's contact-lens preference to EW with the answer to the forced-choice preference questionnaire, and we compared their lens preference with score satisfaction (Kruskal–Wallis ANOVA nonparametric test). We represent P-value in the test, tables and figures. We take as statistically significant differences in the P-value of less than 0.05.

3. Results

Twenty subjects (14 women, 6 men) were enrolled in the study. The ages of the subjects ranged from 18 to 25 years (mean [S.D.]=20.25 [2.2] years) with a spherical equivalent refractive error ranging from +2.00 to −4.75D (mean [S.D.]=−1.60 [1.75]D). No biomicroscopic signs (grade>1; Efron grading scales) of contact lens complications (corneal staining, limbal injection or other) were found. Two subjects were disqualified. One had front surface deposits (lotrafilcon A lens); the other forgot a contact lens (etafilcon A).

3.1. Forced-choice contact-lens preference

Fig. 1 shows the forced-choice subject preference questionnaire about comfort, dryness, red eye and visual quality after overnight wear and at the end of the day. Table 3 shows the frequency of choice between lotrafilcon A and etafilcon A contact lenses. Most subjects (80%, CI95% 62–98%) preferred lotrafilcon A (P=0.007) for EW.

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Fig. 1. Frequency distribution of the forced-choice subject preference questionnaire results (P-value, exact chi-square between lotrafilcon A, etafilcon A, both lenses and no preference).

Table 3.

Forced-choice subject preference questionnaire with relation between contact-lens preference (P-value, exact chi-square between lotrafilcon A and etafilcon A preference)


	Lotrafilcon A	Etafilcon A	P-value
Comfort (% [CI95%])
After overnight wear	60 (39–84%)	10 (0–24%)	0.00
End of the day	70 (48–92%)	20 (1–39%)	0.01

Dryness (% [CI95%])
After overnight wear	15 (0–32%)	50 (26–74%)	0.05
End of the day	25 (4–46%)	50 (26–74%)	0.31

Red eye (% [CI95%])
After overnight wear	20 (1–39%)	20 (1%–39%)	1.00
End of the day	25 (4–46%)	5 (0–15%)	0.10

Visual quality (% [CI95%])
After overnight wear	42 (18–67%)	5 (0–16%)	0.02
End of the day	42 (18–67%)	16 (0–34%)	0.12

3.2. Subjective scored satisfaction analysis

Mean general satisfaction with lotrafilcon A lens was 3.65 points (CI95% 3.04–4.26). With etafilcon A, mean general satisfaction was 2.95 points (CI95% 2.53–3.37; P=0.035). Forty-five percent of subjects were satisfied and 25% were very satisfied with the lotrafilcon A lens. Only 25% were satisfied and no one was very satisfied with the etafilcon A lens.

Mean satisfaction in a dry environment with the lotrafilcon A lens was 3.06 points (CI95% 2.42–3.70). With the etafilcon A, mean satisfaction in a dry environment was 2.65 points (CI95% 2.17–3.13; P=0.133). Thirty-five percent of subjects were satisfied and 5% were very satisfied with the lotrafilcon A lens. Only 10% were satisfied and no one was very satisfied with the etafilcon A lens.

3.3. Answer validation

The answers to the questionnaires were validated. Using contingency tables, we analyzed contact-lens choice for EW with forced-choice preference answers about comfort, dryness, red eye and visual quality after night wear and at the end of the day. Also, we compared lens preference with subjective scored satisfaction (general and dry environment).

3.3.1. Comfort questions

After overnight wear, most (75%) of the subjects who chose the lotrafilcon A contact lenses for EW preferred those lenses, and no one preferred the etafilcon A. However, half the subjects who chose the etafilcon A for EW preferred those lenses, and no one preferred the lotrafilcon A (P=0.00).

At the end of the day, most (87.5%) of the subjects who chose the lotrafilcon A contact lenses for EW preferred the lotrafilcon A, and no one preferred the etafilcon A. All subjects who chose the etafilcon A for EW preferred those lenses, and no one preferred the lotrafilcon A (P=0.00).

3.3.2. Dryness questions

After overnight wear, most (62.5%) of the subjects who chose the lotrafilcon A contact lenses for EW reported more dryness with the etafilcon A. Only a few (6.3%) reported more dryness with the lotrafilcon A. Half the subjects who chose the etafilcon A for EW reported more dryness with the lotrafilcon A. No one reported dryness with the etafilcon A lenses (P=0.05).

At the end of the day, most (62.5%) of the subjects who chose the lotrafilcon A contact lenses for EW reported more dryness with the etafilcon A. Only 12.5% reported more dryness with the lotrafilcon A. All subjects who chose the etafilcon A for EW reported more dryness with the lotrafilcon A (P=0.00).

3.3.3. Red eye questions

After overnight wear, 43.8% of the subjects who chose the lotrafilcon A contact lenses for EW said that neither eye was red; 18.8% said the lotrafilcon A; 25% said the etafilcon A; and 12.5% said that both eyes were red. Most (75%) of the subjects who chose the etafilcon A for EW answered that neither eye was red, and 25% answered the lotrafilcon A. No one reported red eye with the etafilcon A lenses (P=0.53).

At the end of the day, 56.3% of the subjects who chose the lotrafilcon A contact lenses for EW said that neither eye was red; 18.8% said the lotrafilcon A; 6.3% said the etafilcon A; and 18.8% said that both eyes were red. Half the subjects who chose the etafilcon A for EW said that neither eye was red. The other half said the lotrafilcon A. No one reported red eye with the etafilcon A lenses (P=0.51).

3.3.4. Vision quality questions

After overnight wear, 53.3% of the subjects who chose the lotrafilcon A contact lenses for EW reported the same quality of vision with both lenses, and 46.7% reported the best quality of vision with the lotrafilcon A. Half the subjects who chose the etafilcon A for EW reported the same quality of vision with both lenses, 25% reported the lotrafilcon A and another 25% reported the etafilcon A lenses (P=0.12).

At the end of the day, subjects who chose the lotrafilcon A contact lenses for EW answered the same as they had answered after overnight wear. Most (75%) of the subjects who chose the etafilcon A for EW reported better quality of vision with the etafilcon A. Only 25% reported the lotrafilcon A (P=0.00).

3.3.5. General score questions

The general score of the lotrafilcon A was 4.00±1.03 for subjects who preferred the lotrafilcon A and 2.25±1.50 for subjects who chose the etafilcon A (P=0.02). The etafilcon A general score was 2.75±0.85 for subjects who chose the lotrafilcon A and 3.75±0.50 for subjects who chose the etafilcon A (P=0.02).

3.3.6. Dry-environment questions

The lotrafilcon A dry-environment score was 3.38±1.12 for subjects who chose the lotrafilcon A and 2.00±1.15 for subjects who chose the etafilcon A (P=0.04). The dry-environment score for the etafilcon A was 2.69±0.94 for subjects who chose the lotrafilcon A and 2.50±1.00 for subjects who chose the etafilcon A (P=0.75).

No statistically significant relationship was found between contact-lens preference and age, sex, refraction and previous contact-lens wear.

4. Discussion

4.1. Study design

The study design guarantees a double mask with different investigators to randomize, fit the lenses, evaluate ocular health and accomplishment and analyze the forced-choice questionnaire (investigator mask) and a follow-up of 7 days to limit subject manipulation (subject mask). Therefore, the design we have used is adequate for evaluating most aspects of the comparative clinical performance of the two lens types. The contralateral design provides for control of inherent subject factors, allowing for a more sensitive comparison between the two lens types and a subject's preferences [2].

4.2. Dryness

A major reason (9–42%) for discontinuing the use of contact lenses was related to dryness symptoms [13], [18]. In a 1-year follow-up, non-masked clinical trial, Brennan et al. found that silicone hydrogel (balafilcon A) caused less dryness than etafilcon A lenses [2]. But other authors have found that balafilcon A and lotrafilcon A cause similar dryness in EW [15], [19]. We found that lotrafilcon A caused less dryness (overnight and at the end of the day) than etafilcon A. Fonn and Dumbleton did not find differences in dryness between silicone (lotrafilcon A) and three conventional hydrogels: nelfilcon A (CIBA Vision), etafilcon A (Johnson & Johnson Vision Care) and omafilcon A (CooperVision) in symptomatic and asymptomatic subjects during 7h of wear [20]. Dryness results were similar to those of previous studies, which found more pronounced eye dryness with high-water contact lenses [21] and under identical environmental conditions [22]. Lotrafilcon A has lower water content (24%) than etafilcon A (58%).

4.3. Comfort

Initial comfort can affect the subject's perception of his contact lenses [23]. We found that lotrafilcon A was more comfortable after overnight wear and at the end of the day than etafilcon A. These results disagree with those obtained by Fonn and Dumbleton, who did not find differences between silicone and conventional hydrogels. Silicone hydrogel has higher modulus of rigidity than conventional hydrogels [15]. It is possible, therefore, that differences in comfort were associated with dehydration (adequate plasma surface treatment and low water content) or corneal swelling (high oxygen transmissibility) and that it was not related to the physical impact of the lens on the ocular surface. Other authors did not find comfort differences between lotrafilcon A and balafilcon A silicone lenses [15], [19].

4.4. Red eye

Silicone hydrogels reduced limbal and conjunctival redness [15], [24]. Maldonado-Codina et al. found more limbal redness (with Efron grading scales) with etafilcon A than lotrafilcon A for 2 and 4 weeks of daily wear [25]. In our series, subjects reported that none of these eyes was red after overnight wear or at the end of the day. This is not necessarily a contradiction, because our study was of short-term (1 week) lens wear, and we represented the opinion of the subject. Maldonado et al. used biomicroscopic Efron grading scales. Other authors found less red eye after 1 year of EW in an unmasked study with balafilcon A versus etafilcon A [2].

4.5. Vision quality

No Snellen visual acuity differences were found. However, subjects reported higher vision quality with lotrafilcon A than etafilcon A with significant differences after overnight wear. The difference could be because high oxygen transmissibility can reduce overnight corneal swelling and the cornea was more transparent after overnight wear [19], [26].

4.6. Questionnaire validation

We found an elevated correlation between the lens choice answer and the forced-choice preference questionnaire. Therefore, the questionnaire is an effective tool with which to find out the subjects’ preference and satisfaction with different contact lenses, as are other questionnaires that evaluate clinical symptoms [27]. Dryness, foreign-body sensation, discomfort and red eyes are the primary reasons for the discontinuation of contact-lens wear [16]. We found that dryness and comfort were the clinical symptoms with the most influence on contact-lens selection. Therefore, the opinion of the subject can affect contact-lens selection, number of hours per days of wear or the definitive ceasing of contact-lens wear. It is possible that fewer users of contact lenses would cease using them if the lenses did not cause dryness or discomfort in the short and long term.

In conclusion, in short-term EW, lotrafilcon A contact lenses were more comfortable, causing less of a feeling of dryness, after overnight wear and at the end of the day than etafilcon A contact lenses.

Conflict of interest

None of the authors has a financial or proprietary interest in any material or method mentioned.

Acknowledgments

Itziar Fernandez (BS) of the IOBA Eye Institute at the University of Valladolid provided statistical consultation on this study. Begoña Coco (BA) of the IOBA at the University of Valladolid checked the English of the manuscript.

References

[1]. [1]Fonn D, MacDonald K, Richer D, Pritchard N. The ocular response to extended wear of a high Dk silicone hydrogel contact lens. Clin Exp Optom. 2002;85:176–182. MEDLINE | CrossRef

[2]. [2]Brennan NA, Chantal ML, Comstock T, Levy B. A 1-year prospective clinical trial of balafilcon A (PureVision) silicone-hydrogel contact lenses used on a 30-day continuous wear schedule. Ophthalmology. 2002;109:1172–1177. Abstract | Full Text | Full-Text PDF (80 KB) | CrossRef

[3]. [3]Holden BA, Mertz GW, McNally JJ. Corneal swelling response to contact lenses worn under extended wear conditions. Invest Ophthalmol Vis Sci. 1983;24:218–226. MEDLINE

[4]. [4]Nilsson SE, Montan PG. The annualized incidence of contact lens induced keratitis in Sweden and its relation to lens type and wear schedule: results of a 3-month prospective study. CLAO J. 1994;20:225–230. MEDLINE

[5]. [5]Grant T, Chong MS, Vajdic C, et al. Contact lens induced peripheral ulcers during hydrogel contact lens wear. CLAO J. 1998;24:145–151. MEDLINE

[6]. [6]Sankaridurg PR, Sweeney DF, Sharma S, et al. Adverse events with extended wear of disposable hydrogels: results for the first 13 months of lens wear. Ophthalmology. 1999;106:1671–1680. Abstract | Full Text | Full-Text PDF (460 KB) | CrossRef

[7]. [7]Cheng KH, Leung SL, Hoekman HW, et al. A. Incidence of contact-lens-associated microbial keratitis and its related morbidity. Lancet. 1999;354:181–185. CrossRef

[8]. [8]Efron N, Morgan P, Hill E, Raynor M, Tullo A. Incidence and morbidity of hospital-presenting corneal infiltrative events associated with contact lens wear. Clin Exp Optom. 2005;88:232–239. MEDLINE | CrossRef

[9]. [9]Fonn D, MacDonald K, Richter D, Pritchard N. The ocular response to extended wear of a high Dk silicone hydrogel contact lens. Clin Exp Optom. 2002;85:176–182. MEDLINE | CrossRef

[10]. [10]Willcox M, Harmis N, Holden B. Bacterial populations on high-Dk silicone hydrogel contact lenses: effect of length of wear in asymptomatic patients. Clin Exp Optom. 2002;85:172–175. MEDLINE | CrossRef

[11]. [11]Holden BA, Sankaridurg PR, Jalbert I. Adverse events and infections: which ones and how many?. In: Sweeney DF editors. Silicone hydrogels: the rebirth of continuous wear contact lenses. Oxford: Butterworth-Heinemann; 2000;p. 150–213.

[12]. [12]Holden BA, Stephenson A, Stretton S, et al. Superior epithelial arcuate lesions with soft contact lens wear. Optom Vis Sci. 2001;78:9–12. MEDLINE | CrossRef

[13]. [13]Pritchard N, Jones L, Dumbleton K, Fonn D. Epithelial inclusions in association with mucin ball development in high-oxygen permeability hydrogel lenses. Optom Vis Sci. 2000;77:68–72. MEDLINE | CrossRef

[14]. [14]Stern J, Wong R, Naduvilath TJ, et al. Comparison of the performance of 6- or 30-night extended wear schedules with silicone hydrogel lenses over 3 years. Optom Vis Sci. 2004;81:398–406. MEDLINE | CrossRef

[15]. [15]Morgan P, Efron N. Comparative clinical performance of two silicone hydrogel contact lenses for continuous wear. Clin Exp Optom. 2002;85:183–192. MEDLINE | CrossRef

[16]. [16]Pritchard N, Fonn D, Brazeau D. Discontinuation of contact lens wear: a survey. ICLC. 1999;26:157–161.

[17]. [17]Begley C, Chalmers R, Abeto L, et al. The relationship between habitual patient-reported symptoms and clinical signs among patients with dry eye of varying severity. Invest Ophthalmol Vis Sci. 2003;44:4753–4761. MEDLINE | CrossRef

[18]. [18]Chalmers RL, Begley CG. Dryness symptoms among an unselected clinical population with and without contact lens wear. Cont Lens Ant Eye. 2006;29:25–30.

[19]. [19]Santodomingo-Rubido J, Wolffsohn J, Gilmartin B. Changes in ocular physiology, tear film characteristics, and symptomatology with 18 months silicone hydrogel contact lens wear. Optom Vis Sci. 2006;83:73–81. MEDLINE | CrossRef

[20]. [20]Fonn D, Dumbleton K. Dryness and discomfort with silicone hydrogel contact lenses. Eye Contact Lens. 2003;29:101–104.

[21]. [21]Nichols JJ, Sinnott LT. Tear film, contact lens, and patient-related factors associated with contact lens-related dry eye. Invest Ophthalmol Vis Sci. 2006;474:1319–1328.

[22]. [22]Maruyama K, Yokoi N, Takamata A, Kinoshita S. Effect of environmental conditions on tear dynamics in soft contact lens wearers. Invest Ophthalmol Vis Sci. 2004;45:2563–2568. MEDLINE | CrossRef

[23]. [23]Dumbleton K, Chalmers R, Mcnally J, et al. Effect of lens base curve on subjective comfort and assessment of fit with silicone hydrogel continuous wear contact lenses. Optom Vis Sci. 2002;79:633–637. MEDLINE | CrossRef

[24]. [24]Malet F, Pagot R, Peyre C, et al. Clinical results comparing high-oxygen and low-oxygen permeable soft contact lenses in France. Eye Contact Lens. 2003;29:50–54. MEDLINE | CrossRef

[25]. [25]Maldonado-Codina C, Morgan PB, Schnider CM, Efron N. Short-term physiologic response in neophyte subjects fitted with hydrogel and silicone hydrogel contact lenses. Optom Vis Sci. 2004;81:911–921. MEDLINE

[26]. [26]Fonn D, Toit R, Simpson TL, et al. Sympathetic swelling response of the control eye to soft lenses in the other eye. Invest Ophthalmol Vis Sci. 1999;40:3116–3121. MEDLINE

[27]. [27]Riley C, Chalmers R, Pence N. The impact of lens choice in the relief of contact lens related symptoms and ocular surface findings. Contact Lens Ant Eye. 2005;28:13–19.

a IOBA Eye Institute and School of Optometry, Department of Physics TAO, University of Valladolid, C/Ramón y Cajal, 7 E-47005 Valladolid, Spain

b IOBA Eye Institute, University of Valladolid, Valladolid, Spain

Corresponding author. Tel.: +34 983 423 559; fax: +34 983 423 274.

☆ The preliminary results of this manuscript has been presented in “XIX International Meeting of Optics, Optometry and Contact Lenses” in Madrid, Spain, March 10, 2006.

PII: S1367-0484(06)00157-3

doi:10.1016/j.clae.2006.11.002

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