BCLA CLEAR Presbyopia: Management with corneal techniques.

Corneal techniques for enhancing near and intermediate vision to correct presbyopia include surgical and contact lens treatment modalities. Broad approaches used independently or in combination include correcting one eye for distant and the other for near or intermediate vision, (termed monovision or mini-monovision depending on the degree of anisometropia) and/or extending the eye's depth of focus [1]. This report provides an overview of the evidence for the treatment profile, safety, and efficacy of the range of corneal techniques currently available for managing presbyopia. The visual needs and expectations of the patient, their ocular characteristics, and prior history of surgery are critical considerations for patient selection and preoperative evaluation. Contraindications to refractive surgery include unstable refraction, corneal abnormalities, inadequate corneal thickness for the proposed ablation depth, ocular and systemic co-morbidities, uncontrolled mental health issues and unrealistic patient expectations. Laser refractive options for monovision include surface/stromal ablation techniques and keratorefractive lenticule extraction. Alteration of spherical aberration and multifocal ablation profiles are the primary means for increasing ocular depth of focus, using surface and non-surface laser refractive techniques. Corneal inlays use either small aperture optics to increase depth of field or modify the anterior corneal curvature to induce corneal multifocality. Presbyopia correction by conductive keratoplasty involves application of radiofrequency energy to the mid-peripheral corneal stroma which leads to mid-peripheral corneal shrinkage, inducing central corneal steepening. Hyperopic orthokeratology lens fitting can induce spherical aberration and correct some level of presbyopia. Postoperative management, and consideration of potential complications, varies according to technique applied and the time to restore corneal stability, but a minimum of 3 months of follow-up is recommended after corneal refractive procedures. Ongoing follow-up is important in orthokeratology and longer-term follow-up may be required in the event of late complications following corneal inlay surgery.

Effects of Optical Zone Variation of High-Addition Multifocal Contact Lenses on the Global Flash Multifocal Electroretinography.

OBJECTIVES: To evaluate the retinal response to myopic defocus after the wear of soft multifocal contact lenses with high addition through electroretinography. METHODS: Twenty-seven participants meeting inclusion criteria were enrolled. Tropicamide 1% drops (2) were instilled. Participants were then fitted with three different contact lenses: a single-vision spherical lens (SE +3.00 D), L1, serving as a control, and two soft multifocal lens designs (SE +3.00 D/add +10 D), one with a central distance zone of 4.0 mm (L2) and one with a central distance zone of 7.0 mm (L3). A global flash multifocal electroretinography was performed. Direct component (DC) amplitude, DC peak time, induced component (IC) amplitude, and IC peak time were recorded. Waveforms were grouped into five concentric areas, covering from 0° to 24° of retinal eccentricity. Differences of L2/L3 versus L1 were analyzed with t tests. Finally, correlations were calculated between the percentage of defocus in the pupil area versus the electroretinography results. RESULTS: Results show that the DC amplitude, caused mainly by photoreceptors and bipolar cells, is not influenced by the design of the lenses. The IC amplitude, however, is significantly decreased when the lens with a smaller optical zone (L2) is worn. This significant difference only concerns the ring 5, which corresponds to a retinal eccentricity of 15.7° to 24.0°. CONCLUSION: Soft multifocal lens designs influence the peripheral retinal reaction to defocus. A larger treatment zone seems to significantly impact the retinal response to defocus between 15.7° and 24.0° of eccentricity from the macula.

Translation and validation of the contact lens dry eye questionnaire 8 (CLDEQ-8) in Canadian French.

PURPOSE: To present the process that led to the creation of the French Canadian translated version of the Contact Lens Dry Eye Questionnaire-8 (which allows for an assessment of symptoms while wearing soft contact lenses) as well as the validation data of the f-CLDEQ-8. METHODS: The CLDEQ-8 went through the process of reverse translation, which was then reviewed and improved by an experts' committee to create a first version of the French questionnaire. Cognitive interviews were conducted to pretest the tool and ensure content validity. After a review of the pretest, the f-CLDEQ-8 was created. A web-based version of this questionnaire was sent to contact lens wearers (CLW) recruited out of a clinical setting for completion at two different endpoints interspaced by 7 days. Internal consistency and test-reliability were calculated using Cronbach's alpha and Intra-class Correlation coefficient (ICC), respectively. Convergent validity between the f-CLDEQ-8 score and overall opinion of the contact lenses was evaluated with a correlation. RESULTS: 9 CLW with different socio-economic statuses and education levels went through a cognitive interview with the back-translated version of the f-CLDEQ-8 to improve the questionnaire wording and enhance its comprehension. 63 CLW (34.2 ± 10.1 years old and 2/3 of them women) completed the f-CLDEQ-8 twice. An average Cronbach alpha of 0.928 was found and an ICC of 0.944 (CI at 95 % 0.905;0.966). A moderately strong correlation of -0.714 (CI at 95 % -0.817;-0.566) was found between the overall opinion of the contact lenses and the total score to the f-CLDEQ-8. CONCLUSION: The French language version (f-CLDEQ-8) generated from the original CLDEQ -8 was shown to be easy to use, reliable and culturally adapted to French spoken in Canada.

Frequency Doubling Technology Visual Field Loss in Fabry Subjects Related to Retinal Ganglion Cell Function as Explored by ERG and OSOME.

Purpose: This study aims to evaluate potential causes of FDT visual field loss in a selected group of Fabry subjects. Patients and Methods: This is a pilot observational study. Subjects were assessed during 2 visits. The following tests were performed: visual acuity, tonometry, optical coherence tomography (OCT) optic nerve scan, frequency doubling time (FDT) and threshold (SAP) VF, ERG, and Online Spectro-reflectometry Oxygenation Measurement in the Eye (OSOME). Results are compared across visits and, when indicated, interpreted against those collected on non-Fabry population matched for age and sex. Results: The study population was composed of 3 males (34.3 ± 8.9 y.o.) and 5 females (46.4 ± 6.5 y.o). For all subjects, BCVA remained 6/6 OU throughout the study and OCT optic nerve scans were normal. FDT showed a defect in at least 1 quadrant for all participants, in contrast with SAP. FDT PSD value was found different vs SAP. For ERG, the i-wave (52.1 + 2.7 ms) and B-waves (31.6 ± 2.1 ms) peak times were significantly longer compared to a non-Fabry population (p < 0.05). Overall blood oxygenation varied from 61.3% ± 4% to 68.1% ± 4% at the second visit, suggesting a loss of capillary perfusion. Blood volume varied based on location (superior/inferior), eye tested (OD/OS) and time (visit 1/2). The range of values exceeds normal subjects findings (p < 0.05). Blood volume was correlated to FDT PSD value for the superior area of the optic nerve. Conclusion: The results suggest that Fabry subjects present FDT deficits and abnormal ERG patterns that may be explained by a retinal dysfunction affecting retinal ganglion cells (RGCs), second to vascular alterations.

CLEAR - Orthokeratology.

Orthokeratology (ortho-k) is the process of deliberately reshaping the anterior cornea by utilising specialty contact lenses to temporarily and reversibly reduce refractive error after lens removal. Modern ortho-k utilises reverse geometry lens designs, made with highly oxygen permeable rigid materials, worn overnight to reshape the anterior cornea and provide temporary correction of refractive error. More recently, ortho-k has been extensively used to slow the progression of myopia in children. This report reviews the practice of ortho-k, including its history, mechanisms of refractive and ocular changes, current use in the correction of myopia, astigmatism, hyperopia, and presbyopia, and standard of care. Suitable candidates for ortho-k are described, along with the fitting process, factors impacting success, and the potential options for using newer lens designs. Ocular changes associated with ortho-k, such as alterations in corneal thickness, development of microcysts, pigmented arcs, and fibrillary lines are reviewed. The safety of ortho-k is extensively reviewed, along with an overview of non-compliant behaviours and appropriate disinfection regimens. Finally, the role of ortho-k in myopia management for children is discussed in terms of efficacy, safety, and potential mechanisms of myopia control, including the impact of factors such as initial fitting age, baseline refractive error, the role of peripheral defocus, higher order aberrations, pupil size, and treatment zone size.

CLEAR - Scleral lenses.

Scleral lenses were the first type of contact lens, developed in the late nineteenth century to restore vision and protect the ocular surface. With the advent of rigid corneal lenses in the middle of the twentieth century and soft lenses in the 1970's, the use of scleral lenses diminished; in recent times there has been a resurgence in their use driven by advances in manufacturing and ocular imaging technology. Scleral lenses are often the only viable form of contact lens wear across a range of clinical indications and can potentially delay the need for corneal surgery. This report provides a brief historical review of scleral lenses and a detailed account of contemporary scleral lens practice including common indications and recommended terminology. Recent research on ocular surface shape is presented, in addition to a comprehensive account of modern scleral lens fitting and on-eye evaluation. A range of optical and physiological challenges associated with scleral lenses are presented, including options for the clinical management of a range of ocular conditions. Future applications which take advantage of the stability of scleral lenses are also discussed. In summary, this report presents evidence-based recommendations to optimise patient outcomes in modern scleral lens practice.

Bruch Membrane Opening Minimum Rim Width Changes During Scleral Lens Wear.

OBJECTIVE: The purpose of this study was to evaluate the change in Bruch membrane opening minimum rim width (BMO-MRW) during scleral lens (SL) wear. METHODS: Twenty young white subjects were enrolled (10 women and 10 men); preliminary evaluation consisted of serial measurements of intraocular pressure (IOP) using a dynamic noncontact tonometer (Corvis, Oculus), which also yielded a corneal biomechanical index and central corneal thickness, and BMO-MRW using optical coherence tomography imaging (OCT) imaging (Spectralis, Heidelberg) through 6 hrs to establish normative diurnal curves. The next day, participants were fitted with a 16-mm SL on one eye, and OCT measurements were repeated over the same time span. Statistical analysis was carried out with a two-way analysis of variance. Multiple linear regressions were used to identify significant associations. RESULTS: The average diurnal variation for BMO-MRW without lenses was -4.65 µm (95% confidence interval [CI], 0.52-8.77) after 6 hours, whereas it decreased by 8 µm (95% CI, 3.87-12.12; P<0.001) after 6 hours of SL wear. The difference between variations after 6 hours was then -3.35 µm (P=0.029). Variation of the BMO-MRW did not significantly correlate with corneal rigidity (CR), central corneal thickness (CCT), and refractive error (r=-0.224, -0.054 and -0.085, respectively). CONCLUSION: Scleral lens wear induces a statistically significant decrease in BMO-MRW that could potentially be attributed to a change in IOP. The change in BMO-MRW was not affected by CR, CCT, or refractive error. Further studies are needed to better understand the significance of the observed changes at the optic nerve head during scleral lens wear.

The official guide to scleral lens terminology.

PURPOSE: In absence of scleral lens standards, this article aims to provide an official definition of terms related to scleral lens fitting and manufacturing, in order to make more uniform the use of appropriate terms when describing, writing or lecturing about scelral lenses. Adoption of a common terminology may also favor more fruitful exchanges between eyecare practitioners and manufacturers. METHODS: A committee of 12 advances scleral lens clinicians met and develop a list of terms related to scleral lens fit and manufacturing. Litterature review was made using PubMed database with the keywords "scleral lenses" and "terminology". Other related publications such as textbooks were also considered valid references. Validation of the terms selected and their suggested definition was made by consultation of other experts in the field, over 2 years. A final version was adopted by the Scleral Lens Education Society late in 2018. RESULTS: This article contains three main sections. Section I provides the definition of a scleral lens. Section II addresses the general terminology habitually applied to contact lens field but in the context of scleral lens usage. Finally, Section III suggests a decription of terms specifically used when fitting or manufacturing scleral lenses. At the end, recommendations are made to manufacturers about the essential elements to provide to eyecare practitioners in order to help them understanding the lens design and to customize their fit. CONCLUSION: A common language is key to advancing the science and clinical practice of scleral lens fitting. The current terminology will help standardize this field, helping eyecare practitioners, educators, speakers and manufacturers to talk with the same language.

Corneal Endothelial Blebs Induced in Scleral Lens Wearers.

SIGNIFICANCE: In the bleb phenomenon, some endothelial cells transiently lose their specular reflection. This has been reported during contact lens wear and goggle-induced hypoxia or hypercapnia. PURPOSE: The purposes of this study were to determine whether blebs appear after scleral lens wear and if their appearance is influenced by lens clearance and to compare bleb and cell sizes. METHODS: Twenty-one subjects were fitted with two similar scleral lenses with different targeted clearances of 200 and 400 µm (the SL200 and SL400, respectively). Each lens was worn unilaterally for 25 minutes, whereas the other eye served as a control. Before and after lens wear, the endothelium was photographed using specular microscopy. The number of blebs and measurements of the areas of cells and blebs were analyzed. Paired t tests compared differences in the areas of cells and blebs. Differences in median bleb number were evaluated using the Wilcoxon test. RESULTS: After wearing the SL200 and SL400 lenses, respectively, 9 and 14 subjects had at least one bleb. The median bleb number after wearing lenses was significantly different (SL200, 0.00; SL400, 1.00; P = .02). Bleb and cell areas were significantly different (blebs, 293 ± 28; cells, 370 ± 32 µm; P < .0001). CONCLUSIONS: After 25 minutes of wearing scleral lenses with each of the two targeted clearances, SL400 induced significantly more blebs than did SL200, suggesting evidence of reduced oxygen and/or increased carbon dioxide levels under scleral lenses fitted with excessive clearance. Blebs may occur more in smaller cells.

Longitudinal study on ocular manifestations in a cohort of patients with Fabry disease.

PURPOSE: This study aims to assess the evolution of ocular manifestations in a cohort of Fabry patients. METHODS: This is a prospective observational study conducted from 2013 to 2017 (5 consecutive exams). All subjects underwent a comprehensive ocular examination including oriented case history, refraction, corneal topography, biomechanical corneal properties and pachometry assessments, aberrometry, anterior segment evaluation, double-frequency visual field (FDT), intra-ocular pressure, and ocular fundus. At baseline, 41 subjects enrolled but 9 dropped-out and 4 files were not kept for analysis (missing data). Remaining 28 subjects were classified into: Group 1 -hemizygotes (HMZ), all on enzyme replacement therapy (ERT) (N = 10); Group 2 -heterozygotes (HTZ) actively ERT-treated (N = 8), and Group 3 -HTZ not treated (N = 10). RESULTS: There is a high intra and inter-subjects variability. At baseline, prevalence of the ocular manifestations found is similar to published data: cornea verticillata (89.2%), conjunctival vessels tortuosity (85.7%), corneal haze (67.8%), retinal vessels tortuosity (64.2%), anterior cataract (39.2%) and posterior cataract (28.5%). Prevalence for new elements are found: upper lid vessels toricity (96.4%) and micro-aneurysms (42.8%). At the end, micro-aneurysms (+82%), posterior cataract (+75%) corneal haze (+21%) anterior cataract (+17%) and retinal vessels tortuosities (+4%) evolved in prevalence and severity despite the fact that 68% of the patients were on ERT. Treated heterozygotes evolved more than other groups (p>0.05). CONCLUSION: ERT does not seem to halt the clinical evolution of several ocular manifestations. Longer observational time and objective grading systems may be required to fully confirm these findings.

IMI - Clinical Management Guidelines Report.

Best practice clinical guidelines for myopia control involve an understanding of the epidemiology of myopia, risk factors, visual environment interventions, and optical and pharmacologic treatments, as well as skills to translate the risks and benefits of a given myopia control treatment into lay language for both the patient and their parent or caregiver. This report details evidence-based best practice management of the pre-, stable, and the progressing myope, including risk factor identification, examination, selection of treatment strategies, and guidelines for ongoing management. Practitioner considerations such as informed consent, prescribing off-label treatment, and guides for patient and parent communication are detailed. The future research directions of myopia interventions and treatments are discussed, along with the provision of clinical references, resources, and recommendations for continuing professional education in this growing area of clinical practice.

Intra-ocular pressure variation associated with the wear of scleral lenses of different diameters.

PURPOSE: To evaluate the variation of intra-ocular pressure during scleral lens wear, and the influence of the lens diameter on the results. METHODS: This is a prospective, randomized study performed on Caucasian subjects (16 F; 5 M), aged 24.7 + 4.1 y.o. A diurnal variation pattern (IOPg) was established, then, transpalpebral IOP (IOPt) was taken before and during SL wear. One eye, randomly fitted with a 15.8 diameter SL (L1), was compared to the fellow eye, fitted with an 18 mm SL of the same design, thickness and material (L2). Anterior segment tomography was taken pre-and after lens removal. RESULTS: Baseline IOPg (L1:15.2 + 3.1 mm HG; L2: 15.1 +/- 2.8 mm) did not reveal significant diurnal variations. Wearing L1, IOPt rose from 10.1 + 1.9 mm HG to 14.4 + 5.5 mm HG after 4.5 + 0.3 hrs, while with L2, it rose from 9.2 + 2.1 mm HG to 14.4 + 4.8 mm Hg. This difference is statistically significant based on time but not on lenses. Anterior segment parameters did not vary except for the anterior chamber volume (L1: -1.53 + 7.61 mm3; L2: -3.47 + 6.4 mm3), and for the corneal thickness (+2.1% with L1 and L2). CONCLUSION: These results suggest that, as evaluated with a non-standard transpalpebral methodology, IOP during scleral lens wear may be increased in average by 5 mm Hg, regardless of the lens diameter. More work is needed to confirm if practitioners should be warned when using SL on populations at risk for glaucoma.

Effects of Scleral-lens Tear Clearance on Corneal Edema and Post-lens Tear Dynamics: A Pilot Study.

SIGNIFICANCE: The present study with small-diameter scleral lenses (SLs) revealed that post-lens tear thickness (PoLTT) was significantly associated with post-lens tear mixing, but not with central corneal edema, after short-term SL wear. PURPOSE: The aim of this study was to investigate the influence of SL tear clearance (PoLTT) on central corneal thickness and post-lens tear dynamics during 5-hour lens wear. METHODS: Neophytes with no active ocular disease were fitted bilaterally with SLs (hofocon A; 15.6-mm diameter; ~438-µm thickness; 97 Dk; 1.44 refractive index) with various initial PoLTT values ranging from 74 to 543 µm. Central corneal thickness and PoLTT were measured using optical coherence tomography during lens wear. Tear mixing was assessed using fluorogram and "out-in" method. RESULTS: The mean central corneal edema after 5-hour lens wear was 1.51% (95% confidence interval, 1.26 to 1.76%; P < .001), reached its peak at 2-hour post-lens insertion (1.65% [95% confidence interval, 1.45 to 1.85%]), and was independent of PoLTT. The fastest fluorescence decay of the post-lens tear film was observed superiorly. The fluorescence decay rate increased from center to periphery in all quadrants except superiorly. An inverse relationship was found between PoLTT and fluorescence decay rate at both 20-minute and 5-hour wear after lens insertion (P < .05). Excluding observations with out-in time exceeding 5 minutes, we found a direct relationship between PoLTT at 20 minutes after lens insertion and out-in time (P = .047). The % change in the PoLTT after 5-hour wear was greater with a thinner initial tear clearance than those with a thicker one (P = .034). CONCLUSIONS: Within our study parameters, a thinner PoLTT under a small-diameter SL was associated with faster PoLTT mixing. However, there was no relationship between PoLTT and central corneal thickness during 5-hour SL wear.

Analysis of Two Orthokeratology Lens Designs and Comparison of Their Optical Effects on the Cornea.

PURPOSE: This study aims to analyze two commercial orthokeratology lens designs and compare their optical effects at the corneal level. METHODS: This is a retrospective study on subjects seeking an orthokeratology fitting for myopia management at the Université de Montréal clinic between January 2013 and August 2015. Group A included the first 64 subjects fitted with a 4-curve lens design (Paragon CRT; Paragon) who met the inclusion criteria, whereas group B included the same number of subjects fitted with a 5-curve lens design (Dreamlens; Polymer Technology, Rochester, NY). Topographic tangential maps were collected at baseline and 3 months after fitting. The differential map was generated for each patient and analyzed, which involved determining the radius of the central distance zone (CDZ) and the power and width of the high convex zone (HCZ). Results were compared between the two groups, taking baseline refraction into account. Finally, a correlation was estimated between topographic data and corneal parameters (flat and steep K, the corneal eccentricity of each principal meridian). RESULTS: The CDZ for group A is significantly larger than the one generated for group B both horizontally (t(126)=12.12, P<0.01) and vertically (t(126)=15.690, P<0.01). However, there was no significant difference regarding the HCZ power generated. The only correlations found were a strong positive association between CDZ radius and HCZ power generated by lens A nasally (r=0.450; P=0.000) and temporally (r=0.558; P=0.000), and a weaker association between the baseline refractive error, along with the nasal (r=0.237; P=0.033) and temporal (r=0.288; P=0.028) HCZ power for lens B. CONCLUSION: The four- and five-curve orthokeratology lens designs generate significantly different optical modifications on the cornea. This can affect reports on orthokeratology efficacy for myopia management as well as the lens selection when used for myopia correction.

Clinical Evaluation of Large Diameter Rigid-Gas Permeable Versus Soft Toric Contact Lenses for the Correction of Refractive Astigmatism. A MultiCenter Study.

PURPOSE: This study aims to address the clinical performance of a large diameter rigid gas permeable lens (LRGP) in a group of subjects with low-to-moderate (0.75-2.75 D) refractive astigmatism. An additional goal was to determine whether soft toric or LRGP contact lenses performed better objectively in the correction of astigmatism and to determine which modality is preferred by subjects. METHODS: This was a multisite prospective cross-over clinical study. Ten asymptomatic contact lens wearers per site (four university clinics) were recruited and randomly assigned to group A or group B. Group A was assigned to start wearing Comfilcon A soft toric lens first, for two weeks, and then crossed over to LRGP lenses (Boston XO, 14.3 mm diameter miniscleral lens). Group B initially wore LRGP lenses and then crossed over to soft toric lenses. For each type of lens worn, low-contrast and high-contrast visual acuity (VA) were evaluated at distance. At the conclusion of the study, after two months, all subjects completed a questionnaire in which they were asked to indicate their preference for one type of lens (soft toric or LRGP) and to rate the quality of vision in day-to-day activities. RESULTS: Thirty-six of 38 (94.7%) subjects completed the study with 75% preferring the vision of the LRGP lens as compared to the soft toric lenses worn in the study. 52.7% expressed a preference to continue with this modality despite only 38.8% reporting that these LRGP lenses are easy or very easy to handle. Wear time, subjective comfort, and subjective vision ratings exhibited no significant difference between the two groups. CONCLUSIONS: In a population of asymptomatic contact lens wearers, LRGP lenses can be considered as a good alternative to soft toric lenses for the correction of refractive astigmatism.

Variation of clearance considering viscosity of the solution used in the reservoir and following scleral lens wear over time.

PURPOSE: This study aims to evaluate the settling of a scleral lens and if this process is influenced by the nature of the fluid layer. METHODS: A prospective, non-randomized control study was performed using an 18mm scleral lens. They were fitted with a central clearance of 400 um at insertion. One eye was randomly assigned to be fitted with a non-preserved gel solution of carboxymethylcellulose, while the other was inserted with non-preserved saline. Measurements of clearance in 3 locations were taken (OCT) at baseline, every 30min up to 1h30 post insertion and every 2h thereafter up to 6h00 of wear. A two-way repeated measure analysis of variance (liquids×times) was used to test central, nasal and temporal fluid thickness. RESULTS: Following 6h of wear, the 18mm lens had a mean central settling of 70.0±9.8µm, 36.7±9.8µm of which occurred within the first 30min of wear. There was no significant difference between lenses filled with non-preserved saline to those with non-preserved gel. However, a paired comparison concluded to a significant difference between mean nasal settling (41.4µm) and temporal settling (20.4µm). CONCLUSION: With respect to the lens studied, current results suggest that practitioners can evaluate the lens 30min post insertion and can estimate the amount of fluid that will remain after lens stabilization by doubling the value obtained initially. The use of non-preserved saline or non-preserved more viscous solution to fill the lens does not influence its settling.

Oxygen Tension Beneath Scleral Lenses of Different Clearances.

PURPOSE: To evaluate the relative partial pressure in oxygen (pO2) at the corneal surface under Boston XO2 scleral lenses (SL) fitted with targeted clearances of 200 and 400 µm (SL200 and SL400). METHODS: During this prospective study, the right eyes of eight normal subjects were fitted with SL200 and SL400. Clearance, validated after 5 minutes of wear with an optical coherence tomograph, was used with lens thicknesses to calculate transmissibility and estimate pO2. Corneal pO2s were measured with an oxygen electrode after 5 minutes of (1) corneal exposure to calibrating gases with various pO2 or of (2) SL wear. Decays in pO2 were modeled to an exponential. Linear regression between exponent k of these decays and calibrating gas pO2s allowed for the calculation of corneal pO2 under SL. Differences between pO2s beneath SL200 and SL400 were tested with a mixed ANOVA. RESULTS: The estimated transmissibility based on thicknesses and clearances (239.7 ± 34.7; 434.5 ± 33.2 µm) predicted a corneal pO2 of 8.52 ± 0.51 and 6.37 ± 0.28% for SL200 and SL400. These values were close to measured pO2: 9.07 ± 0.86 and 6.19 ± 0.87% (mean ± SEM) (P < .05) for SL200 and SL400, respectively. Both pO2 measurements fall short of the theoretical values needed to prevent hypoxia during lens wear (9.9% and above). CONCLUSIONS: As shown in vivo for the first time, an 18-mm scleral lens fitted with a 400-µm clearance reduces the oxygen tension available to the cornea by 30% compared to a similar lens fitted with a 200-µm clearance after 5 minutes of wear.

Comparing two different daily disposable lenses for improving discomfort related to contact lens wear.

PURPOSE: This study aimed to compare two daily disposable lenses to reduce lens-induced discomfort (CLD) among different populations of symptomatic wearers. METHODS: This was a multicenter, crossover, study. Subjects were contact lens wearers reporting CLD. Subjects (76) were randomly assigned to wear Nelfilcon A (NF) then Delefilcon A (DF)- group A- or vice-versa (group B). Tear break-up time (TBUT), corneal (CS) and conjunctival staining (CJS) were graded at every visit. Subjects'symptoms were evaluated with Contact Lens Dry Eye Questionnaire (CLDEQ-8) and a research questionnaire (Université de Montréal). RESULTS: Compared to baseline (BL), TBUT did not vary (BL) 6.7+2.1s vs. 6.7+1.8s (NF) vs. 6.4+1.9 (DF) (F=1.69; p=0.201) NF wearers were more at risk of developing moderate CJS (odds ratio 14.324; 95% CI 3.103-66.126) and more likely to show increased CS (odds ratio 8.754; 95% CI 2.181-35.146). Comfortable hours of wear reported at BL (7.6+2.3h) did not improve significantly with NF lenses (8.5+ 2.6h; F=1.095; p=0.394) but increased by 22% with DF lenses (10.7+3.0h; F=2.434; p=0.031). The total CLDEQ-8 score was improved with DF lenses (BL 17.2 vs. NF 16.1, p=0.397; vs. DF 8.3, p<0.001), especially on more symptomatic subjects. In the end, 92% of patients preferred to switch over DD lenses, 78% selecting DF material for the future. CONCLUSION: Outcome from switching CLD wearers to DD lenses is material related. It seems that initial severity of the symptoms could be also a factor to consider.

Prevalence of asymptomatic ocular conditions in subjects with refractive-based symptoms.

BACKGROUND: This study aims to determine the overall prevalence of ocular conditions in a population from 19 to 64 years old, presenting with refractive-based symptoms only. Results could impact clinical standard of eye care on a similar population. METHODS: This is a retrospective study on patients seen for an eye examination at the Clinique Universitaire de la Vision (CUV), between January 2007 and 2009. Files of individuals who presented with refractive symptoms were only selected and classified by file number. Then, every third file from the beginning was kept and reviewed by a reader. A second reader did the same with every third file from the end. Both readers were trained to use the same analysis grid to classify the diagnosed ocular conditions. In the case of multiple findings, the most severe condition was considered. The overall prevalence of ocular conditions was determined by calculating their occurrence divided by the number of files analyzed. RESULTS: A total of 860 charts were analyzed. In 26.1% of the cases an ocular condition was diagnosed. This work establishes a higher prevalence of ocular conditions compared to another study conducted in Canada in the past. This difference can be explained by a different analytical methodology and by the fact that all examinations, in this study, were made under pupillary dilation. CONCLUSION: The presence of ocular conditions in 26% of asymptomatic patients supports the need to assess ocular health under pupil dilation as part of any eye examination. However, further cost-to-benefit analysis is required before establishing such a recommendation.