Michel Guillon

Contact lens practice

Part 1 History: origin of the contact lens, Anthony Sabbell. Part 2 Material technology: chemical composition & properties, Miguel Refojo oxygen transport through contact lenses, William Benjamin mechanical properties, Ronald E. Stephenson. Part 3 Contact lens design technology: contact lens design, Michel Guillon and William Sammons soft contact lens kinetics, Yoshizo Kikkawa contact lens optics, Colin Fowler quality assurance and quality control for volume lens manufacturing, Stewart Gibson quality control of rigid lenses in clinical practice, Richard Pearson the verification of soft lenses in clinical practice, Michael Port manufacturing standards, Michael Sheridan. Part 4 Anatomical & physiological factors: microscopic anatomy and ultra structure of the cornea, conjunctiva and lids, Ramesh Tripathi, et al innervation of the anterior segment, Gordon Ruskell corenal physiology & biophysics, Stephen Kwok biochemical aspects of the cornea, Barry Masters. Part 5 Clinical techniques: keratometry & specialist optical instrumentation, Ronald Rabbetts photokeratoscopy & corneal topography, Arthur Ho and Michel Guillon biomicroscopy, Steve Zantos and Ian Cox pachometry - clinical & scientific applications, Tailoi Chan and David Pye aesthesiometry, Michel Millodot the role of tears in contact lens performance and its measurement, Jean-Pierre Guillon oxygen consumption & measurements, Richard Hill. Part 6 Practical routine: indications and contraindications for contact lens wear, Barry Weissman preliminary examination patient selection, Barry Weissman contact lens care systems and solutions used by the practitioner, Fiona Stapleton & Judith Stechler symptomology and aftercare, Joshua Joshephson, et al. Part 7 Fitting techniques: basic contact lens fitting, Michel Guillon fitting the astigmatic patient with rigid contact lenses, Theodore Grosvenor toric hydrogel contact lenses, Nigel Burnett Hodd and Joshua Josephson tinted hydrogel contact lenses, Richard Weisbarth the scleral regid lens - optical and therapeutic applications, Montague Ruben gas permeable scleral contact lenses, Oliver Schein, et al presyopia and influence of ageing on the prescription of contact lenses, William Benjamin and Irving Borish contact lenses for children, David Taylor and Judith Morris. Part 8 Abnormal and therapeutic fitting: correction of irregular astigmatism with contact lenses, Montague Ruben contact lens fitting post refractive surgery, Christine Astin orthokeratology, Leo Carney therapeutic soft contact lenses, Thomas John, et al. (Part contents.)

Association Between Contact Lens Discomfort and Pre-lens Tear Film Kinetics

Purpose The relationship between contact lens wettability and comfort has been extensively evaluated; however, a direct correlation between the characteristics of the pre-lens tear film and the symptoms associated with contact lens discomfort has yet to be established. In addition, there is relatively limited knowledge relating to the entire tear film kinetics during the inter-blink period in contact lens wearers. The purpose of this analysis was to identify the characteristics of the pre-lens tear film kinetics that may be associated with the symptoms of contact lens discomfort. Methods The study population comprised 202 soft (hydrogel and silicone hydrogel) contact lens wearers attending pre-screening visits at the OTG-i research clinic. All participants completed the Ocular Surface Disease Index (OSDI) questionnaire and the tear film was quantified via post hoc, masked analysis of high definition digital Tearscope videos recorded at the visit. The tear film kinetics of the least symptomatic wearers (OSDI lowest quintile scores, n = 45) were compared to the tear film kinetics of the most symptomatic wearers (OSDI highest quintile scores, n = 43). The hypothesis tested was that the tear film kinetics of asymptomatic wearers were better than tear film kinetics of symptomatic wearers. Results The distribution of lens types worn was as follows: Daily Disposable 46.5%, 1-Month Replacement 39.6%, and 2-Week Replacement 13.6%. 48.2% of lenses were silicone hydrogel and 51.8% hydrogel. Symptomatic wearers had a shorter break-up time (4.7 s vs. 6.0 s; p = 0.003), lesser surface coverage by the tear film during the interblink period (95.1% vs. 98.5%; p < 0.001) and greater surface exposure at the time of the blink (9.4% vs. 3.9%; p = 0.001). Conclusions The current study demonstrated that the tear film kinetics of asymptomatic and symptomatic contact lens wearers were different, the findings supporting the hypothesis of poorer tear film kinetics for symptomatic than asymptomatic wearers in a general contact lens wearing population.

The Effects of Age, Refractive Status, and Luminance on Pupil Size.

Purpose Pupil size is critical for optimal performance of presbyopic contact lenses. Although the effect of luminance is well known, little information is available regarding other contributing factors such as aging and refractive status. Methods The cohort population comprised 304 patients (127 male, 177 female) aged 18 to 78 years. Pupils were photographed at three controlled luminance levels 250, 50, and 2.5 cd/m2 using an infra-red macro video camera. Measurements of pupil diameter were conducted after transforming pixel values to linear values in millimeters. Results Luminance was the most influential factor with pupil diameter increasing with decreased luminance (p < 0.001, all comparisons). Age was also found to be a significant factor with a smaller diameter in the older groups, but overall the difference was only significant between the pre-presbyopes and the established presbyopes (p = 0.017). Pupil diameter decreased significantly with increasing age, the effect being most marked at low luminance (<0.001). The smallest pupil diameters were measured for hyperopes and the largest for myopes and although refractive error was not a significant factor alone, there was a significant interaction between luminance and refractive error with the greatest differences in pupil diameter between myopes and emmetropes at low luminance (p < 0.001). Pupil diameter changes modeled by multilinear regression (p < 0.001) identified age, luminance, best sphere refraction, and refractive error as significant factors accounting for just over 70% of the average variation in pupil diameter. Conclusions Both age and refractive status were found to affect pupil size with larger pupils measured for younger patients and myopes. Designs for multifocal contact lens corrections should take both age and refractive status into consideration; a faster progression from distance to near corrections across the optical zone of the lens is expected to be required for established presbyopes and hyperopes than it is for early presbyopes, myopes, and emmetropes.

Effect of lens care system on silicone hydrogel contact lens wettability.

PURPOSEnThe purpose was to compare the effect of the repeated usage of two care systems (one hydrogen peroxide cleaning and disinfecting system and one polyaminopropyl biguanide (PHMB) containing multi-purpose system) with silicone hydrogel contact lenses worn for three months on a daily wear modality. A specific aspect of interest was of the effect of the care systems on contact lens wettability.nnnMETHODSnSeventy-four symptomatic contact lens wearers, habitually wearing either ACUVUE(®) OASYS(®) (n=37) or PureVision™ (n=37), constituted the study population. The study was a two-arm prospective, investigator-masked, bilateral study of three-month duration to evaluate the effects of CLEAR CARE(®) compared with renu(®) fresh™. The subjects were randomized to one of the two lens care systems. Contact lens wettability and surface cleanliness were assessed with the Tearscope and reported in terms of pre-lens non-invasive break-up time (PL-NIBUT) and visible deposits. Baseline assessments at enrollment were with the subjects own contact lenses worn for at least 6h when using their habitual PHMB-preserved care system and at the dispensing visit with new contact lenses. At the follow-up visits, the contact lenses were worn for at least 6h, and were at least 11 days old for ACUVUE(®) OASYS(®) and 25 days old for PureVision™.nnnRESULTSnThe results obtained showed that: (i) with CLEAR CARE(®), a significant improvement in contact lens wettability was recorded compared with the habitual care system at the three-month follow-up visit (mean median PL-NIBUT 5.8 vs. 4.0 s, p<0.001). Further, with this same lens care system a significant increase in wettability was observed at the three-month follow-up visit compared with dispensing (mean median PL-NIBUT 5.8 vs. 4.5s, p=0.022). (ii) Whereas no difference in contact lens wettability was observed at dispensing between the two lens care groups (mean PL-NIBUT: 4.5 vs. 4.2s, p=0.518), a significantly more stable pre-lens tear film was observed with CLEAR CARE(®) than with renu(®) fresh™ at both the two-month (mean PL-NIBUT: 4.6 vs. 3.7s, p=0.005) and three-month (mean PL-NIBUT: 5.8 vs. 4.2 s, p=0.028) visits. iii. With renu(®) fresh™, no significant differences were observed at the end of three months of use compared with either the habitual care system or the new contact lens solution (mean PL-NIBUT: 3M 4.2 vs. Disp 4.2 s (p=0.420) vs. enrolment habitual care solution 5.1s (p=0.734)). iv. With CLEAR CARE(®) significant increases in the incidence of surfaces free of both mucus (3 month 95%. vs. habitual solution 82% enrolment; p=0.005) and lipid (3 month 87% vs. habitual solution 72% enrolment; p=0.009) were observed.nnnCONCLUSIONnSignificantly better contact lens wettability and surface cleanliness were achieved for ACUVUE(®) OASYS(®) and PureVision™ with CLEAR CARE(®) than with renu(®) fresh™ at the end of three months of use.

Diurnal Variation in Comfort in Contact Lens and Non-contact Lens Wearers.

Purpose The purpose of this investigation was to evaluate the diurnal variation in symptoms associated with ocular discomfort in contact lens (CL) wearers and non-CL wearers. Methods The study population comprised 604 individuals attending pre-screening visits at the OTG-i research clinic; 60% were current soft CL wearers (hydrogel and silicone hydrogel) and 40% were non-CL wearers. Symptomatology status was determined by the OSDI questionnaire (58% asymptomatic, 42% symptomatic). Participants were asked to grade their comfort, vision, and other symptoms during the day and in the evening (before lens removal for CL wearers) on 0 to 100 visual analogue scales. Results Diurnal decrease in comfort was significantly greater for CL wearers (−16.0 vs. −6.3, p < 0.001) and symptomatic participants (p = 0.015). Diurnal decrease in subjective vision was also significantly greater for CL wearers (−10.4 vs. −6.9, p = 0.005) and symptomatic participants (p = 0.001), and the interaction between these factors was also significant (p = 0.019). Dryness, grittiness, and irritation increased significantly more for CL wearers (p < 0.001, p = 0.012, and p = 0.004, respectively) and grittiness, irritation, and stinging for symptomatic participants (p = 0.016, p < 0.001, and p < 0.001, respectively). For the CL wearers, there was a significant interaction between dryness and age (p = 0.026) with the diurnal increase in dryness being greater in those under 40 (+15.6 vs. +10.0). Conclusions The diurnal decrease in comfort and subjective vision, and the diurnal increase in dryness, grittiness, and irritation, were significantly more marked for CL wearers than non-CL wearers. Diurnal changes in comfort, grittiness, stinging, irritation, and vision were influenced by the subject’s overall symptomatology as assessed by the OSDI questionnaire. For dryness symptoms, the diurnal decrease was most marked in young CL wearers. For the symptoms of stinging and vision, the diurnal changes were most pronounced in the symptomatic groups.

Ocular Dominance and Handedness in Golf Putting.

Purpose In golf, the impact of eye-hand dominance on putting performance has long been debated. Eye-hand dominance is thought to impact how golfers judge the alignment of the ball with the target and the club with the ball, as well as how golfers visualize the line of the putt when making decisions about the force needed to hit the ball. Previous studies have all measured ocular dominance in primary gaze only, despite golfers spending a significant amount of their time in a putting stance (bent at the hips, head tilted down). Thus, the purpose of this study was to assess ocular dominance in both primary gaze (aligning the ball with the target) and putting gaze (addressing the ball and aligning the club). Methods This study investigated measuring pointing ocular dominance in both primary and putting gaze positions on 31 golfers (14 amateur, 7 club professionals, and 10 top professionals). All players were right-handed golfers, although one reported having no hand dominance and one reported being strongly left hand dominant. Results The results showed that (1) primary and putting gaze ocular dominances are not equal, nor are they predictive of each other; (2) the magnitude of putting ocular dominance is significantly less than the magnitude of primary gaze ocular dominance; (3) ocular dominance is not correlated with handedness in either primary or putting gaze; and (4) eye-hand dominance is not associated with increased putting skill, although ocular dominance may be associated with increased putting success. Conclusions It is important that coaches assess golfers’ ocular dominance in both primary and putting gaze positions to ensure they have the most accurate information upon which to base their vision strategy decisions.

The influence of lens care systems on eyelid tissue changes during silicone hydrogel contact lens wear

PURPOSEnTo compare the effects of a hydrogen peroxide (H2O2)-based lens care solution and a polyhexamethylene biguanide (PHMB) multi-purpose solution on the eyelids when used with silicone hydrogel (SiHy) contact lenses.nnnMETHODSnA total of 74 symptomatic wearers of ACUVUE® OASYS® (senofilcon A; nu202f=u202f39) or PureVision® (balafilcon A; nu202f=u202f35) contact lenses were randomised 1:1 to either CLEAR CARE® Cleaning & Disinfecting Solution or renu® fresh™ multi-purpose solution (nu202f=u202f37 each). Assessments of hyperaemia, papillae and lid margin staining of eyelid tissue were evaluated subjectively by a masked investigator at enrolment (with the subjects habitual SiHy contact lenses and PHMB-preserved care systems), at dispensing visit (when no lenses were worn) and at 3-months follow-up.nnnRESULTSnThere were no differences in eyelid assessments between the two lens care groups at dispensing visit (pu202f=u202f0.086 to 0.947). After 3 months, the papillae response was significantly less marked with H2O2-based solution than with PHMB-based solution (pu202f=u202f0.017). Lid hyperaemia (pu202f<u202f0.001) and papillae (pu202f=u202f0.002) were also significantly reduced. Although lid hyperaemia was also reduced with PHMB-based solution (pu202f<u202f0.001), there was no concurrent decrease in papillae response (pu202f=u202f0.051). No improvements were found in eyelid margin staining either over time or between the two lens care groups.nnnCONCLUSIONnIn symptomatic contact lens wearers, a H2O2-based lens care solution used with senofilcon A and balafilcon A lenses was better tolerated by eyelid tissues than was a PHMB-based solution and led to a decrease in clinical markers of eyelid inflammation.

An Analysis of Penalty Kicks in Elite Football Post 1997

The penalty kick in football is a seemingly simplistic play; however, it has increased in complexity since 1997 when the rules changed allowing goalkeepers to move laterally along their goal line before the ball was kicked. Prior to 1997 goalkeepers were required to remain still until the ball was struck. The objective of this study was to determine the importance of the penalty kick in the modern game of football. A retrospective study of the 2002, 2006 and 2010 World Cup and the 2000, 2004 and 2008 European Championship tournaments was carried out, assessing the importance of the penalty kick in match play and shootouts and the effect of the time of the game on the shooters success rate. This study demonstrated the conversion rate of penalties was 73% in shootouts and 68% in match play. Significantly more penalties were awarded late in the game: twice as many penalties in the second half than the first and close to four times as many in the fourth quarter vs. the first. Teams awarded penalty kicks during match play won 52%, drew 30% and lost 18% of the time; chances of winning increased to 61% if the penalty was scored, but decreased to 29% if missed. Teams participating in either the World Cup or European Championship final match had roughly a 50% chance of being involved in a penalty shootout during the tournament. Penalty shots and their outcome significantly impact match results in post 1997 football.