Assessing a modified fitting approach for improved multifocal contact lens fitting

Purpose: To compare the effectiveness of a modified and previous fitting guide for multifocal (MF) contact lenses that share a common optical design, lotrafilcon B, nelfilcon A, and delefilcon A, in current soft contact lens (CL) wearers needing presbyopia correction.Methods: This international multicenter, prospective, randomized, subject-masked study assessed the superiority of the modified guide relative to the previous guide as determined by the number of MF CLs needed to successfully fit each eye at the screening/fitting visit.Results: A total of 183 presbyopic subjects were randomized to fitting using the modified (n = 99) and previous (n = 84) MF CL fitting guides. The mean ± SD numbers of lenses required to fit each eye at the screening/fitting visit using the modified and previous fitting guides were 1.2 ± 0.5 and 1.4 ± 0.5, respectively. The least-squares mean difference (0.2) met predetermined criteria for superiority of the modified fitting guide. At the screening/fitting visit, 82.8% (164/108) and 65.1% (105/166) of presbyopic eyes were fit with one pair of MF lenses using the modified and previous guides, respectively, and 98.0% (194/198) of eyes were fit with 1–2 pairs of MF lenses using the modified guide. A higher percentage of eye care practitioners gave the highest ratings for ease of fit for the modified than for the previous fitting guide (63.6% [7/11] vs 33.3% [3/9]).Conclusions: The modified fitting guide was superior at reducing the number of MF lenses required to successfully fit each presbyopic patient.     

International survey of contact lens fitting for myopia control in children

PurposeTo determine the extent of contact lens fitting for myopia control (MC) in children (defined as ≤ 17 years of age) worldwide and to characterize the associated demographics and fitting patterns.MethodsSurvey forms were sent to contact lens fitters in 66 countries between January and March every year for eight consecutive years (2011–2018, inclusive). Practitioners were asked to record data relating to the first 10 contact lens fits performed after receiving the survey form. Data were analysed for those countries reporting ≥ 100 contact lens fits to children.ResultsData were analysed for 535 MC fits and 23,295 other (non-MC) lens fits undertaken in 31 countries reporting ≥ 100 contact lens fits to children, with 52.1% of MC fits and 12.0% of non-MC fits being with rigid lenses (p < 0.0001). Overall, MC lenses represented 2.3% of all contact lens fits to children, with significant differences between nations (p < 0.0001), ranging from no MC fits recorded in the Czech Republic, Greece, Japan, South Korea and Puerto Rico, to 24.9% in Austria. There has been an increase in contact lens fitting for MC over the survey period (p < 0.0001). MC contact lenses were fitted to younger children compared to non-MC lenses (MC, median 13 years vs. non-MC, median 15 years) (p < 0.0001). There was no sex bias in the fitting of MC lenses (p = 0.89).ConclusionsMC lenses are currently being prescribed for younger children in equal measure in terms of soft vs. rigid lenses and males vs. females. The extent of MC fitting is low and varies between nations. The gradual increase in MC fitting throughout the survey period perhaps reflects growing concerns among practitioners over the myopia epidemic.     

Topical anaesthetic use prior to rigid gas permeable contact lens fitting

Purpose

To investigate effect of topical anaesthetic (TA) during gas permeable (GP) contact lens (CL) fitting on subjective and objective measures of patient anxiety.

Performance and predictability of a new large diameter contact lens design in keratoconic corneae

ObjectivesTo evaluate the clinical performance and predictability using corneal topography in the fitting of a new large-diameter rigid gas permeable (RGP) contact lens design in eyes with keratoconus (KCN).MethodsThis study presents a review of eyes fitted with Alexa ES lenses for nonsurgical optimisation of visual correction. Anterior steep simulated keratometry (sim-K steep), corneal diameter (HVID), the Curvature at the apex in diopters (Cc), and distance from the corneal apex to the centre of the cornea (Lc) in millimetres derived from the Cone Location and Magnitude Index (CLMI) were recorded. Visual acuity, mean wearing time, final sagittal depth and adverse events were also recorded. Correlations between topographic indices and base curve were evaluated using the Pearson correlation coefficient.ResultsForty-six eyes from 26 patients (19 males/ 7 females) were included. Mean visual acuity improved from 0.49 ± 0.32 with glasses, to -0.02 ± 0.10 with the contact lens. The mean daily wear time was 12.19 ± 1.96 hours. No complications were detected in 95.65% of the eyes [95% CI (83.9%-99.2%)] but two episodes of non-infectious keratitis. The average sagittal depth of the lenses fitted was 0.425 ± 0.15 mm, and it was positively correlated with the Cc value (r² = 0.66, p< 0.0001, n=46) derived from the CLMI index of the pre-fitting topography.ConclusionsCorneoscleral RGP contact lenses are a safe, and effective alternative for managing KCN patients to corneal lenses. Also, clinical data derived from the corneal topography could be used to help to decide the first diagnostic lens to be assessed, easing the overall fitting process.     

Overnight orthokeratology

Overnight orthokeratology lenses are approved in countries all over the world for the temporary reduction in myopia, and recently, one lens design has received regulatory approval for myopia control in Europe. The modern orthokeratology lens has a substantial history from its origins of attempting to flatten the corneal curvature with a spherical rigid contact lens to sophisticated gas permeable lenses, designed to reshape the cornea. These lenses are predominantly prescribed for children to slow myopia progression and limit axial elongation of the eye. This article reviews the peer-reviewed literature on the efficacy of orthokeratology for myopia control, sustainability after treatment is discontinued, and the safety concerns of overnight contact lens wear. Future avenues of research are discussed.     

Fitting an MSD (Mini Scleral Design) rigid contact lens in advanced keratoconus with INTACS

Keratoconus is a bilateral degenerative disease characterized by a non-inflammatory, progressive central corneal ectasia (typically asymmetric) and decreased vision. In its early stages it may be managed with spectacles and soft contact lenses but more commonly it is managed with rigid contact lenses. In advanced stages, when contact lenses can no longer be fit, have become intolerable, or corneal damage is severe, a penetrating keratoplasty is commonly performed. Alternative surgical techniques, such as the use of intra-stromal corneal ring segments (INTACS) have been developed to try and improve the fit of rigid contact lenses in keratoconic patients and avoid penetrating keratoplasties. This case report follows through the fitting of rigid contact lenses in an advanced keratoconic cornea after an INTACS procedure and discusses clinical findings, treatment options, and the use of mini-scleral and scleral lens designs as they relate to the challenges encountered in managing such a patient. Mini-scleral and scleral lenses are relatively easy to fit, and can be of benefit to many patients, including advanced keratoconic patients, post-INTAC patients and post-penetrating keratoplasty patients.     

Near binocular visual function in young adult orthokeratology versus soft contact lens wearers

Purpose

To compare near point binocular vision function of young adult myopes wearing orthokeratology (OK) lenses to matched single vision soft disposable contact lens (SCL) wearers.

Exploring contact lens opportunities for patients above the age of 40 years

PurposeContact lenses offer a good option for patients with presbyopia, especially with improved optical designs available in modern multifocal contact lenses. Due to the ageing population there is good opportunity to increase contact lens penetration by managing these patients better. However, multifocal contact lenses achieve low penetration in the market.MethodsA questionnaire was administered to people aged above 40 years, to investigate their perceptions of contact lenses for presbyopia. Only people, with presbyopia, who were existing contact lens wearers or willing to try contact lenses were included. Participants were recruited from United Kingdom (UK), United States of America (USA), Netherlands, Germany, France, Spain and Italy.ResultsData from 1540 participants above the age of 40 years was collected, 57.9% were females and 42.1% males. Overall, 50.8% of the participants wore contact lenses, but contact lens wear was less common amongst older participants. Some data supported earlier studies, such as 6.1% wore gas permeable lenses. However, only 25% of the contact lens wearers used multifocal contact lenses. The reasons the participants wanted to wear contact lenses were similar to younger patient such as sports or cosmesis reasons. Reasons why participants had dropped out of contact lenses included discomfort and dry eye related issues. Poor visual performance with contact lenses was a reason to dropout of contact lenses for the older participants.ConclusionsThe study highlights some failings by eye care practitioners in the management of patients with presbyopia. It seems that patients of this age group are seeking suggestions and recommendations from their eye care practitioner including upgrading contact lenses and dual wear options. The day-to-day problems encountered by the contact lens wearers in this study seem to be, in the main, things that could be easily tackled by additional counselling and instruction from the eye care practitioners.     

Corneal topography for pancorneal toric edge rigid gas-permeable contact lens fitting in patients with keratoconus,and differences in age and gender

PurposeTo determine whether pancorneal rigid gas-permeable toric edge contact lenses (pancorneal RGP-CL) fitting could be improved by using non-central corneal shape predictors, and to compare these parameters with respect to age and gender in patients with keratoconus.MethodsThe current study was a retrospective study including patients with clinically evident keratoconus (on videokeratography) from three medical centres located in the Netherlands. Medical history, visual acuity, refraction, and contact lens characteristics were documented. All participants underwent ophthalmic examination including measurement of K-values (steepest, flattest, mean, as a non-central parameter the minimum radius [K-minimum], and all combined) using corneal topography. Fitting of contact lenses was based on the fluorescence pattern as seen during slitlamp examination.ResultsA total of 378 eyes of 218 patients with keratoconus were included. Of these, 257 (68%) were fitted with a pancorneal RGP-CL. The central K-values, K-steep and K-flat, performed well in predicting the base curve radius, though, for pancorneal RGP-CL the non-central K-minimum added most (35.5%) to the total explained variance in base curve radius. Regarding age and gender, women tended to have larger K-values than men. No differences in K-values were found with respect to age.DiscussionWe found that including the K-minimum as a non-central parameter may improve prediction of the best base curve radius for pancorneal RGP-CL and may reduce the number of trial contact lenses. In line with other studies, suggestive evidence was found for a difference in pattern of progression of keratoconus with gender, but not with age.     

Driving performance and road sign identification by multifocal contact lens wearers in a driving simulator

PurposeThe purpose of this study was to compare sign identification distances and driving performance metrics in presbyopic participants while wearing multifocal contact lenses (MFCL) and while wearing progressive addition lens (PAL) spectacles.Methods19 presbyopic participants completed PAL spectacle assessments and contact lens fitting and follow up visits before driving assessments began. These assessments occurred in a simulator equipped with a full-sized sedan on a motion platform and a 260 degree screen. Participants completed the driving task with PAL and with MFCL. Participants followed a lead car and identified signs at various distances from the road. For the two wearing conditions, comparisons of the distance along the road at which signs were identified were made using repeated measures ANOVA. Paired t-tests were used to compare driving performance for the two conditions.ResultsThere was no statistical difference in sign identification distance between PAL and MFLC for signs 32.0 m from the road side of the road (182 ± 46 m for MFCL; 205 ± 45 m for PAL; P = 0.07) or 51.4 m from the side of the road (204 ± 43 m for MFCL; 216 ± 36 m for PAL; P = 0.3). Only signs 70.2 m from the roadside showed a significant difference (207 ± 42 m with MFCL; 232 ± 39 m with PAL; P = 0.01), All distances were greater than those required to safely stop a vehicle. There were no significant differences in the driving performance metrics between the refractive corrections.ConclusionDriving performance metrics were similar for MFCL and PAL spectacles. Sign identification distances with both eyewear types were well within the distances required for safe vehicle stopping.     

Factors in the success of new contact lens wearers

Purpose

To determine the first-year retention rate for patients fitted with contact lenses (CLs) and identify factors associated with retention and dropout.

Chromatic dispersion of soft contact lens materials

PurposeTo investigate and evaluate the chromatic dispersion of various hydrogel and silicon hydrogel contact lens materials.MethodsEighteen different soft contact lens materials with high and low water content in lens power of −1.00 DS were measured by one operator at temperature of 20 °C ± 0.5° soaked in ISO standard phosphate-buffered saline (PBS) and in their respective packaging solutions (PS). An analogue Abbe refractometer (Model Zuzi 320, AUXILAB, S.L., Navarra, Spain) was used for refractive index (RI) measurements at 5 different wavelengths. All contact lenses were presented in a random and masked order to the operator. The Bland-Altman method with 95 % limits of agreement (LoA) and coefficient of repeatability (CoR) was used to characterise the repeatability of refractive index measurements. The Abbe numbers for each material were calculated by entering the measured and interpolated refractive indices into the Abbe number equation. One-way ANOVA analysis was used to test if there were significant differences between the 5 different wavelengths (470 nm–680 nm) within each material. An unpaired t-test was used to determine if there were differences in refractive index or dispersion between packaging solution and PBS results.ResultsNelfilcon A (Dailies Aqua Comfort Plus) soaked in PS showed the best repeatability of all 18 examined soft contact lenses across all wavelengths with an average refractive index of 1.3848 for all 6 contact lenses with a standard deviation of 0.00064. The 95 % limits of agreement were between 1.3835 and 1.3860. The mean coefficient of repeatability for nelfilcon A was 0.00125. For contact lenses soaked in ISO Standard PBS comfilcon A (Biofinity) had the best repeatability. The average refractive index of all 6 contact lenses was 1.4041 with a standard deviation of 0.00031 and a coefficient of repeatability of 0.00060. The 95 % limits of agreement were between 1.4035 and 1.4047. The analysis with One-way ANOVA with multiple comparisons involving Holm-Sidak post-hoc, showed that there are significant differences (p < 0.001, F_ratio = 376.2 between wavelengths and F_ratio = 1559 between different refractive indices) in the refractive index of most common lens materials across the visible wavelength range. Based on unpaired t-test, there is no significant difference (p > 0.05) in the Abbe numbers of the tested lens materials whether they have been placed in the packaging solution or in standard PBS (p > 0.05, 95 % CI = −4.8070 to 5.8680, t = 0.2054). The Abbe numbers for the calculated contact lenses soaked in PS ranged between 43.7 and 89.9. For contact lenses stored in PBS the range was between 46.3 and 81.6.ConclusionThere is a good repeatability between repeated RI measurements taken from the same lens and from the same material. The significant differences between the refractive indices across the 5 different wavelengths showed the presence of chromatic dispersion in the 18 evaluated soft contact lens materials. Furthermore, it could be shown that there is no significant difference in dispersion whether the contact lenses are soaked in standard PBS or in their respective packaging solutions. With no other published data available as a reference, absolute accuracy of the calculated Abbe numbers remains to be confirmed, however, this study did confirm that significant chromatic dispersion exists in soft contact lens materials.     

Theoretical fitting characteristics of typical soft contact lens designs

Purose

To calculate theoretical fitting success rates (SR) for a range of typical soft contact lens (SCL) designs using a mathematical model.

Microbial adherence to cosmetic contact lenses

AimTo investigate whether cosmetic contact lenses (CCL) with surface pigments affect microbial adherence.MethodFifteen brands of CCL were purchased from optical, non-optical retail outlets, and via the Internet. A standardized rub-off test was performed on each CCL (five lenses per brand) to confirm the location of the pigments. The rub-off test comprised gentle rubbing on the surfaces of each CCL with wetted cotton buds for a maximum of 20 rubs per surface. A new set of CCL (five lenses per brand) were incubated in Pseudomonas aeruginosa overnight. Viable counts of adhered bacteria were determined by the number of colony-forming units (CFU) on agar media on each lens. The adherence of P. aeruginosa as well as Staphylococcus aureus and Serratia marcescens to three brands of CCL (A–C) (five lenses per brand) were also compared to their adherences on their clear counterparts.ResultsOnly two of the 15 brands of CCL tested (brands B and C) had pigments that did not detach with the rub-off test. The remaining 13 brands of CCL all failed the rub-off test and these lenses showed higher P. aeruginosa adherence (8.7 × 10⁵–1.9 × 10⁶ CFU/lens). Brands B and C lenses showed at least six times less bacterial adhesion than the other 13 brands. Compared to their clear counterparts, bacterial adherence to brands B and C lenses did not differ significantly, whereas brand A lenses showed significantly higher adherence.ConclusionSurface pigments on CCL resulted in significantly higher bacterial adherence.     

Corneo-scleral limbal changes following short-term soft contact lens wear

Purpose

To assess whether short-term soft contact lens wear alters the anterior eye surface.

Accuracy,inter-observer and intra-observer reliability in topography assessment of multifocal contact lens centration

PurposeTo evaluate the accuracy and reliability (inter and intra-observer) of a method to assess multifocal contact lenses (MCLs) centration using a corneal topography unit.MethodDaily-disposable MCLs (Fusion 1 day Presbyo) were fitted on both eyes of the subjects. For each lens fit a slit lamp digital picture and videokeratograph image were taken in a rapid but randomised sequence. Photo-editing software was used to assess the position of the MCL centre with respect to pupil centre as taken from the slit lamp photograph. The position of the MCL centre was automatically detected as the point of maximum curvature from the videokeratography. Three further manual and qualitative procedures to detect MCL centre, comparing a template of CLs optic zones to the videokeratographic image were performed by 4 practitioners using 3 different algorithms to represent the topographic map. Each manual reading was repeated 3 times.ResultsTwenty-two subjects (11 males) aged 22.8 ± 1.9 years (range 20.8–27.0 years) were recruited. The accuracy of the 4 topographic assessments in determining the centre coordinates of the MCL with respect to SL assessment was good: no differences were found in the left eyes and although in the right eyes a more temporal and superior position of MCLs was determined (paired t-test, p < 0.05) the difference was clinically negligible (0.16 ± 0.36 mm horizontally, 0.23 ± 0.48 vertically). Amongst the 4 practitioners one-way Anova for repeated measures showed no differences for any of the 3 manual assessments. Intra-class correlation coefficient was calculated among the 3 readings for each manual procedure and was very good (between 0.75 and 0.98) in 3 practitioners and moderate (between 0.49 and 0.92) in the fourth.ConclusionsThe assessment of MCL centration by performing corneal topography over the MCL is an accurate method. Furthermore, inter and intra-practitioner reliability showed by manual procedures appeared very good.     

Quantification of contact lens wettability after prolonged visual device use under low humidity conditions

Purpose: Discomfort of silicone hydrogel (SiHy) contact lenses (CL) is associated with longer wearing time, demanding visual tasks, and dry environments. This study investigated the impact of challenging environmental conditions on thewettability of four daily disposable SiHy CL. Methods: Habitual wearers of delefilcon A (n=32) and somofilcon A (n=32) were tested with their habitual lenses and with stenfilcon A and narafilcon A lenses. Digital videos were captured using non-invasive Tearscope illumination after 3 hrs of conventional wear and 3 hrs of computer use at 20% relative humidity (RH). Masked investigators analysed non-invasive break up time (NIBUT), minimum protected area (MPA) ofthe lens surface by the tear film, and dehydration speed (DS) over the interblink period after exposure to 20% RH.Results: For habitual delefilcon A wearers, mean NIBUT was longer with delefilcon A (9.2 sec) than stenfilcon A (6.3 sec, p = 0.052) and narafilcon A (5.1 sec, p = 0.006); mean MPA was significantly higher with delefilcon A (95.4%)than stenfilcon A (84.4%, p = 0.002) and narafilcon A (82.9%, p = 0.006); mean DS was lower with delefilcon A (0.28 mm2/sec) than stenfilcon A (0.81 mm2/sec, p = 0.002) and narafilcon A (0.60 mm2/sec, p = 0.056). For habitual somofilcon A wearers, mean MPA was lower for narafilcon A (76.2%) than for somofilcon A (89.0%, p < 0.001) but not stenfilcon A (88.4%, p = 0.748) and mean DS was higher for narafilcon A (0.96 mm2/sec) than somofilcon A (0.60mm2/sec, p = 0.029) but not stenfilcon A (0.51 mm2/sec, p = 0.701). Conclusions: Delefilcon A CL performed betterthan stenfilcon A and narafilcon A after 6 hrs of wear including 3 hrs intensive visual tasks under challenging environmental conditions. Delefilcon A CL may be preferable for CL wearers with intensive computers and/or digital devices usage.     

Atomic force microscopy analysis of the effect of plasma treatment on gas permeable contact lens surface topography

PurposeUsing atomic force microscopy (AFM) to investigate anterior surface topography (AST) in worn and unworn, plasma surface-treated (PST) and untreated (UT) gas permeable (GP) lenses, and influence of surface topography on in vivo comfort.MethodsGP lens AST evaluated with AFM in tapping mode, using an uncoated, 40 nm symmetric tip (sampling frequency: 300 kHz), at five randomised locations, over a 100μm² area, to produce mean average roughness (Ra) and root mean square (RMS) values for each sample. Four unworn lenses (two PST, two UT) were examined (Quasar/Boston EO material). Twenty worn lenses (ten PST, ten UT) of same design and material as unworn lenses collected after 3 months lens wear. General wearing comfort reported by visual analogue scale (VAS) at 3 months visit. For sample preparation, two worn UT GP lenses were divided into four segments; each segment underwent a different lens rinse and drying method.ResultsUnworn: UT lenses had significantly higher mean RMS and Ra values compared to PST (Mann-Whitney, p < 0.05). Worn: UT Median RMS values were significantly higher than PST (Mann-Whitney, p < 0.05). Comfort: no correlation found between general comfort and RMS or Ra scores. Sample preparation: Method 4 (purified, distilled water rinse/nitrogen gas dry) produced optimum median RMS and Ra values.ConclusionsUnworn PST GP lenses had lower Ra and RMS values compared with unworn UT GP lenses. After 3 months wear, PST lenses had smoother surface topographies than UT lenses. No relationship was found between surface topography and lens wear comfort. Sample preparation protocol directly impacts AFM results.