Lifetime corneal edema load model

Purpose: To highlight the potential benefits for long-term use of silicone hydrogels daily disposable (DD) contact lenses, particularly with patients who are noncompliant, sleeping or napping while wearing their lenses, or those who have higher oxygen demands and wear this modality for decades. Methods: Published data for corneal swelling with lenses and no lens wear were used to develop a nonlinear least squares model. The edema load experienced with a range of oxygen transmissibilities (Dk/t) and wear compliance (sleep and napping) was determined. A mixed-effects linear regression model was used to compare the edema load for high and average corneal swellers. Results: The edema load generated demonstrates that a high Dk/t silicone hydrogel lens results in edema levels close to that with no lens wear. In comparison, hydrogels with a Dk/t of 27 (×10−9 [cm mL{O2}][s mLmmHg]), worn on a daily wear schedule will result in 1.5 times more edema and up to two times more if the patient is noncompliant over each decade of wear. High swellers after four decades of wear will have an edema load 10 to 17 times greater than average swellers depending on Dk/t and their degree of noncompliance with the daily wear modality. Conclusions: Prescribing silicone hydrogelDDlenses, particularly with higher DK/t,may help to maintain the long-term ocular health of patients, when they wear their lenses fulltime for many decades. Translational Relevance: Illustrates the importance of Dk/t for any CL wear modality where patients nap or sleep in lenses or have high oxygen needs

Observance des cédules de remplacement des lentilles jetables et des silicone hydrogels par les patients et les praticiens au Canada

Objet : Évaluer la fréquence de remplacement (FR) des silicone hydrogels (SH) et des lentilles cornéennes journalières jetables (JJ) au Canada recommandée actuellement par les optométristes, déterminer les taux de non-conformité aux recommandations par les optométristes et les patients, et analyser les raisons de la non-conformité. Méthodes : Des trousses de questionnaires ont été envoyées aux optométristes au Canada qui avaient accepté de participer à l’enquête. Les patients ont répondu à des questions d’ordre démographique et à d’autres sur leurs habitudes de port de lentilles cornéennes, notamment la FR recommandée et effectivement suivie. Les optométristes devaient fournir des renseignements sur les lentilles et la FR qu’ils recommandaient. Cinquante-huit optométristes ont renvoyé 654 questionnaires, dont 578 ont pu être analysés. Résultats : Soixante-dix pour cent des patients étaient des femmes présentant un âge médian de 32 ans. La répartition par type de lentille s’établissait comme suit : 18 % JJ, 35 % SH de deux semaines et 47 % SH d'un mois. Six pour cent des lentilles étaient à port prolongé. Les patients ont indiqué porter leurs lentilles pendant une période médiane de 12 heures par jour; dans le cas des JJ, la médiane était de cinq jours/semaine, tandis qu’elle a été de sept jours/semaine pour les SH (deux semaines et un mois). La FR recommandée par les optométristes a été différente de celle des fabricants dans 6 % des JJ, 35 % des SH de deux semaines et 2 % des SH d'un mois. Parmi les patients qui n’ont suivi ni les recommandations du fabricant ni celles de l’optométriste, 12 % portaient des JJ, 43 %, des SH de deux semaines et 31 %, des SH d'un mois. Les patients qui ne respectaient pas les recommandations avaient pour la plupart oublié quel jour ils devaient remplacer leurs lentilles. Cinquante-six pour cent des patients ont précisé qu’un système de rappel les aiderait à se conformer à la FR. Un pourcentage plus élevé de patients ont respecté la FR parce qu’ils avaient confiance dans leur optométriste. Conclusions : En général, les optométristes ont adopté la fréquence de remplacement recommandée par les fabricants dans le cas des lentilles JJ et des SH d'un mois, mais ils ont souvent recommandé des intervalles plus longs pour les SH de deux semaines. Ce sont les porteurs de lentilles JJ qui ont le plus suivi les recommandations, mais ce sont les porteurs de SH de deux semaines qui se sont le moins conformés aux recommandations. La conformité s’accroîtrait sans doute s’il y avait un système de rappel ou si l’optométriste insistait sur les risques susceptibles de découler de la non-observation des règles

Inhibition of Defocus-Induced Myopia in Chickens

Woods, J., Guthrie, S. E., Keir, N., Dillehay, S., Tyson, M., Griffin, R., … Irving, E. (2013). Inhibition of Defocus-Induced Myopia in Chickens. Investigative Opthalmology & Visual Science, 54(4), 2662. https://doi.org/10.1167/iovs.12-10742Purpose.: To determine the effect of wearing a lens with a unique peripheral optical design on the development and progression of defocus-induced myopia in newly hatched chickens.Methods.: Eighty-five newly hatched chickens underwent bilateral retinoscopy and A-scan ultrasound to determine their refractive error and axial length. They were randomly divided into Control and two Test groups, in which each chicken was fitted with a goggle-lens over the right eye, with the left eye remaining untreated. The Control group wore a lens of power −10.00 diopters (D) of standard spherical optical design. The two Test lenses both had a central optical power −10.00 D, but used different peripheral myopia progression control (MPC) designs. For all groups, retinoscopy was repeated on days 3, 7, 10, and 14; ultrasound was repeated on day 14. Results.: On day 0 there was no statistical difference in refractive error (mean +6.92 D) or axial length (mean 8.06 mm) between Test and Control groups or treated and untreated eyes (all P > 0.05). At day 14, 37 (43.5%) of 85 chickens had not experienced goggle detachment and were included in the final analyses. In this cohort there was a significant refractive difference between the treated eyes of the Control group (n = 17) and those of Test 1 (n = 14) and Test 2 (n = 6) groups (both P < 0.01): Control −4.65 ± 2.11 D, Test 1 +4.57 ± 3.11 D, Test 2 +1.08 ± 1.24 D (mean ± SEM). There was also a significant axial length difference (both P < 0.01): Control 10.55 ± 0.36 mm, Test 1 9.99 ± 0.14 mm, Test 2 10.17 ± 0.18 mm. Conclusions.: Use of these unique MPC lens designs over 14 days caused a significant reduction in the development of defocus-induced myopia in chickens; the degree of reduction appeared to be design specific

Dehydration, lens movement and dryness ratings of hydrogel contact lenses

Previous studies have shown that soft lenses dehydrate during lens wear. The purpose of this study was to determine the dehydration time course of 38% water content non-ionic Medalist, 58% ionic Acuvue and 74% non-ionic Permaflex lenses, and the relationship between dehydration and in vivo diameter, movement and symptoms of dryness. Nineteen subjects randomly wore three pairs of lenses, each for 7 h. Lens movement and diameter were measured in vivo and hydration after lens removal at 1, 3 and 7 h. Dryness was rated by the subjects using a visual analogue scale. A separate experiment was conducted to measure hydration changes after 7 continuous hours of lens wear. The water content of all three lens types decreased significantly over 7 h with Acuvue decreasing more than the Permaflex and Medalist lenses in the interrupted and continuous experiments (ANOVA P < 0.05). Dehydration of Acuvue was significantly greater in the 7 h continuous experiment (9.0 +/- 2.6% H2O, ANOVA P = 0.0062) compared to the interrupted experiment. Hydration levels measured for Acuvue lenses on subjects for control purposes at 0, 1, 3 and 7 h showed no difference over time (ANOVA P = 0.0711). Movement of Permaflex lenses decreased 0.60 +/- 0.57 mm (ANOVA P = 0.0005) over 7 h and the in vivo diameter of Acuvue lenses decreased by 0.12 +/- 0.16 mm (ANOVA P = 0.0569). Dryness ratings increased significantly and equally for all three lenses over 7 h (ANOVA P = 0.9833).(ABSTRACT TRUNCATED AT 250 WORDS

Patient preferences and comparative ocular responses to rigid and soft contact lenses

Patient preferences and ocular responses were compared between rigid and soft contact lenses by randomly fitting 32 neophyte subjects with a rigid lens in 1 eye and a soft lens in the contralateral eye. Twenty-seven of 32 subjects completed the 3-month study and 16 subjects were willing to continue for an additional 3-month extension. Subjects preferred the comfort and handling of the soft lens but preferred the vision provided by the rigid lens and initially its ease of maintenance. There was also a marked preference for the soft lens when all aspects of lens wear were compared. Objectively, the rigid lenses were responsible for more ocular changes than the soft lenses. Palpebral aperture sizes of the rigid gas permeable (RGP) wearing eyes decreased significantly (0.5 mm; p < 0.05) compared to the soft lens wearing eyes. The incidence of corneal staining was significantly greater in the rigid lens wearing eye (50% RGP vs. 22% soft) but limbal injection was greater in the soft lens wearing eye (18% soft vs. 6% RGP). Refractive sphere, cylinder, and corneal astigmatism decreased in the rigid lens wearing eye after 3 months. This daily wear clinical trial has shown a marked subjective preference for wearing soft lenses with fewer short-term ocular effects

An investigation of the efficacy of a novel ocular lubricant

Objective: To investigate the efficacy of a novel ocular lubricant compared with a commercially marketed ocular lubricant in a group of noncontact lens wearers currently using over-the-counter products for the management of symptoms of moderate to severe dry eye. Methods: This was a prospective, double-masked study that randomized 110 subjects in a ratio of 1:1 to receive a novel ocular lubricant (test group) or a marketed ocular lubricant (control group). Subjects were instructed to instill the lubricant eye drops at least three times daily. After enrollment, subjects were evaluated at baseline and at 7 and 30 days. They were also required to complete a series of home-based subjective questionnaires after 15 days. Main outcomes were subjective symptoms and objective clinical assessment at 7 and 30 days. Results: The test group had higher overall comfort ratings than the control group (P = 0.012). Seventy-one percent of the test group and 57% of the control group said the drops used &ldquo;somewhat&rdquo; or &ldquo;definitely&rdquo; improved ocular comfort; 62% of the test group had greater end-of-day comfort compared with 45% of the control group (P = 0.015). There were no between-group differences in visual acuity, tear quality or quantity, corneal staining, conjunctival staining, or bulbar and limbal conjunctival hyperemia.Conclusions: The novel ocular lubricant offers equivalent or superior comfort compared with a marketed lubricant eye drop. Objective clinical outcomes were not statistically significantly different between the two groups.<br /

Managing the emerging presbyopic contact lens wearer

The article deals with a study that examined the performance of a new silicone hydrogel multifocal contact lens for emerging presbyopes compared to other forms of correction. Study participants were asked to wear a different lens design for a week at a time. They were divided into the asymptomatic group and the symptomatic group. Results of the study showed that 24 participants had no difficulties with near vision tasks. It also found similar ghosting between the multifocal and habitual corrections for the near tasks under low illumination

Ocular and subjective responses to frequent replacement of daily wear soft contact lenses

PURPOSE: A significant number of soft contact lens wearers develop complications as a result of lens contamination. We conducted a single-blind 2 year clinical trial to determine if scheduled frequent replacement of lenses decreases complications.----- METHODS: One hundred nineteen non-contact lens wearers were fit with soft contact lenses and randomly assigned to 1 or 3 month replacement schedules or a non-replacement (control) group. All subjects were fit with 0.04 mm thick HEMA (water content: 38%) lenses to be worn on a daily wear basis only. A single multipurpose solution was prescribed for cleaning and disinfection.----- RESULTS: The 2-year results showed a significantly greater number of subjects in the non-replacement group exhibited microcysts, infiltrates, clinically significant corneal staining, and limbal and bulbar injection. As a result of lens deposition and damage, approximately twice the number of unscheduled lens replacements per subject were necessary in the non-replacement group compared with the 1 and 3 month replacement groups. Overall subject satisfaction with lens wear decreased in the non-replacement group and increased in the 1 and 3 month replacement groups over the 2-year period.----- CONCLUSIONS: Frequent replacement of soft lenses for daily wear as compared to non-replacement daily wear: 1) is less likely to cause contact lens induced complications; 2) reduces the number of unscheduled lens replacements; and 3) improves satisfaction with lens wear