Visual performance of scleral lenses and their impact on quality of life in patients with irregular corneas / Desempenho visual das lentes esclerais e seu impacto na qualidade de vida de pacientes com córneas irregulares

ABSTRACT Purpose: We aimed to evaluate the visual quality performance of scleral contact lenses in patients with keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism, and their impact on quality of life. Methods: We included 40 patients (58 eyes) with keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism who were examined between October 2014 and June 2017 and fitted with scleral contact lenses in this study. Before fitting scleral contact lenses, we noted refraction, uncorrected distance visual acuity, spectacle-corrected distance visual acuity, uncorrected contrast sensitivity, and spectacle-corrected contrast sensitivity. We performed corneal topography on and applied a questionnaire that included the National Eye Institute Visual Functioning Questionnaire to all participants. We recorded corrected contrast sensitivity and corrected distance visual acuity on the third month after fitting scleral contact lenses and requested that subjects repeat the National Eye Institute Visual Functioning Questionnaire. Results: The mean age of patients was 28.12 ± 13.19 years. Mean logMAR uncorrected distance visual acuity, spectacle-corrected distance visual acuity, and corrected distance visual acuity with scleral contact lenses were 0.91 ± 0.21 (0.40-1.80), 0.57 ± 0.12 (0.10-1.80), and 0.16 ± 0.02 (0.00-1.30), respectively. We observed significantly higher corrected distance visual acuity with scleral contact lenses compared with uncorrected distance visual acuity and spectacle-corrected distance visual acuity (p<0.05). Mean uncorrected contrast sensitivity, spectacle-corrected contrast sensitivity and CCS with scleral contact lenses were 0.97 ± 0.12 (0.30-1.65), 1.16 ± 0.51 (0.30-1.80), and 1.51 ± 0.25 (0.90-1.80), respectively. Significantly higher contrast sensitivity levels were recorded with scleral contact lenses compared with those recorded with uncorrected contrast sensitivity and spectacle-corrected contrast sensitivity (p<0.05). We found the National Eye Institute Visual Functioning Questionnaire overall score for patients with scleral contact lens treatment to be significantly higher compared with that for patients with uncorrected sight (p<0.05). Conclusion: Scleral contact lenses are an effective alternative visual correction method for keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism. A significant increase in visual acuity and contrast sensitivity can be obtained with scleral contact lenses in patients with irregular corneas.

RESUMO Objetivo: Avaliar o desempenho da qualidade visual das lentes de contato esclerais em pacientes com ceratocone, degeneração marginal transparente e astigmatismo pós-ceratoplastia e seu impacto na qualidade de vida. Métodos: Foram incluídos 40 pacientes (58 olhos) com ceratocone, degeneração marginal transparente ou astigmatismo pós-ce­ratoplastia que foram examinados entre outubro de 2014 e junho de 2017 e adaptados com lentes de contato esclerais neste estudo. Antes de ajustar as lentes de contato esclerais, registrou-se refração, acuidade visual à distância não corrigida, acuidade visual à distância corrigida por óculos, sensibilidade ao contraste não corrigida e sensibilidade ao contraste corrigida por óculos. Rea­lizamos topografia da córnea e aplicamos um questionário que incluía o Questionário de Funcionamento Visual do National Eye Institute para todos os participantes. Registramos a sensibilidade ao contraste corrigida e corrigimos a acuidade visual à distância no terceiro mês após a adaptação das lentes de contato esclerais e solicitamos aos participantes que repetissem o Questionário de Funcionamento Visual do National Eye Institute. Resultados: A idade média dos pacientes foi de 28,12 ± 13,19 anos. A acuidade visual à distância não corrigida logMAR média, a acuidade visual à distância corrigida por óculos e a distância visual corrigida com as lentes de contato esclerais foram 0,91 ± 0,21 (0,40-1,80), 0,57 ± 0,12 (0,10-1,80), 0,16 ± 0,02 (0,00-1,30), respectivamente. Observamos uma acuidade visual à distância corrigida significativamente maior com lentes de contato esclerais em comparação à acuidade visual à distância não corrigida e à acuidade visual à distância corrigida por óculos (p<0,05). Sensibilidade ao contraste médio não corrigido, sensibilidade ao contraste corrigida por óculos e CCS com lentes de contato esclerais foram 0,97 ± 0,12 (0,30-1,65), 1,16 ± 0,51 (0,30-1,80), 1,51 ± 0,25 (0,90-1,80), respectivamente. Significativamente maiores níveis de sensibilidade ao contraste foram registrados com lentes de contato esclerais em comparação com aqueles registrados com sensibilidade ao contraste não corrigida e sensibilidade ao contraste corrigida por óculos (p<0,05). Descobrimos que a pontuação geral do Questionário de Funcionamento Visual do National Eye Institute para pacientes em tratamento com lentes de contato esclerais é significativamente maior em comparação com pacientes com visão não corrigia (p<0,05). Conclusão: As lentes de contato esclerais constituem um método alternativo eficaz de correção visual alternativa para o ceratocone, degeneração marginal transparente e o astigmatismo pós-ceratoplastia. Um aumento significativo na acuidade visual e sensibilidade ao contraste pode ser obtido com lentes de contato esclerais em pacientes com córneas irregulares.

Visual performance of scleral lenses and their impact on quality of life in patients with irregular corneas.

PURPOSE: We aimed to evaluate the visual quality performance of scleral contact lenses in patients with keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism, and their impact on quality of life. METHODS: We included 40 patients (58 eyes) with keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism who were examined between October 2014 and June 2017 and fitted with scleral contact lenses in this study. Before fitting scleral contact lenses, we noted refraction, uncorrected distance visual acuity, spectacle-corrected distance visual acuity, uncorrected contrast sensitivity, and spectacle-corrected contrast sensitivity. We performed corneal topography on and applied a questionnaire that included the National Eye Institute Visual Functioning Questionnaire to all participants. We recorded corrected contrast sensitivity and corrected distance visual acuity on the third month after fitting scleral contact lenses and requested that subjects repeat the National Eye Institute Visual Functioning Questionnaire. RESULTS: The mean age of patients was 28.12 ± 13.19 years. Mean logMAR uncorrected distance visual acuity, spectacle-corrected distance visual acuity, and corrected distance visual acuity with scleral contact lenses were 0.91 ± 0.21 (0.40-1.80), 0.57 ± 0.12 (0.10-1.80), and 0.16 ± 0.02 (0.00-1.30), respectively. We observed significantly higher corrected distance visual acuity with scleral contact lenses compared with uncorrected distance visual acuity and spectacle-corrected distance visual acuity (p<0.05). Mean uncorrected contrast sensitivity, spectacle-corrected contrast sensitivity and CCS with scleral contact lenses were 0.97 ± 0.12 (0.30-1.65), 1.16 ± 0.51 (0.30-1.80), and 1.51 ± 0.25 (0.90-1.80), respectively. Significantly higher contrast sensitivity levels were recorded with scleral contact lenses compared with those recorded with uncorrected contrast sensitivity and spectacle-corrected contrast sensitivity (p<0.05). We found the National Eye Institute Visual Functioning Questionnaire overall score for patients with scleral contact lens treatment to be significantly higher compared with that for patients with uncorrected sight (p<0.05). CONCLUSION: Scleral contact lenses are an effective alternative visual correction method for keratoconus, pellucid marginal degeneration, and post-keratoplasty astigmatism. A significant increase in visual acuity and contrast sensitivity can be obtained with scleral contact lenses in patients with irregular corneas.

In vitro optical quality of monofocal aspheric toric intraocular lenses: effect of cylindrical power.

PURPOSE: To assess the in vitro optical quality of monofocal aspheric toric intraocular lenses (IOLs) as a function of the cylindrical power. METHODS: The in vitro optical quality of the AcrySof IQ Toric IOLs SN6AT2, SN6AT3, SN6AT4, SN6AT5 and SN6AT6 (Alcon Laboratories Inc., Forth Worth, TX, USA) was assessed with an instrument conceived for measuring Zernike's coefficients at 3.0- and 5.0-mm apertures. As a reference, the aspheric monofocal lens AcrySof IQ Aspheric SN60WF (Alcon Laboratories Inc., Forth Worth, TX, USA) was also measured. The area of visibility and cut-off frequency were used to describe the modulation transfer function (MTF) of each lens; meanwhile, the light in the bucket and the diameter of a circular area centred on the point-spread function (PSF) peak that captures 50% of the light energy were used to describe the PSF of each lens. Finally, an image simulation was computed from the Zernike values with reference purposes. RESULTS: Small differences were found on the metrics used for describing the MTF and PSF of the lenses at both tested apertures, but these were not statistically significant (p > 0.05). Furthermore, the image simulation showed that these differences would not have clinical relevance at all. CONCLUSIONS: The optical performance of the AcrySof IQ toric IOLs in terms of MTF and PSF is good and seems to be independent of the cylindrical power and similar to a non-toric aspheric lens.

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.

Clinical Performance of a Spherical Hybrid Lens Design in High Regular Astigmatism.

OBJECTIVES: To evaluate safety, efficacy, and comfort of a spherical hybrid contact lens design in management of the regular astigmatic cornea. METHODS: This prospective study included 18 eyes from 18 subjects with regular corneal astigmatism greater than -3.00 diopters. All patients were fitted with optimal hybrid contact lenses. Demographic data and fitting parameters were recorded. Patient refraction, visual outcomes, contrast sensitivity, and glare levels were measured 2 weeks, 3 months, and 6 months after the start of lens use. Duration of lens use, comfort grades, causes of lens discontinuation, and any noticed complications were recorded. RESULTS: An average of 1.8 lenses (range 1-3) was required to achieve the optimal fit. Average logMAR visual acuity had improved significantly from 0.92±0.03 to 0.03±0.04 (P<0.001) at the last follow-up. Contrast sensitivity and glare tests were also significantly improved. Statistical analysis of the subjective responses indicated a strong acceptance of the lens by most of the patients. Mean wearing time of lenses was 10.1±3.2 hr/d. Causes of discontinuation were discomfort (2 patients), high lens price (2 patients), and handling problems (1 patient). Minimal complications were demonstrated in wearers of the lenses during follow-up visits. CONCLUSION: Spherical hybrid contact lenses provide a good option for patients with regular astigmatic corneas. They provide optimal visual function with high comfort and patient satisfaction, especially when surgery is undesirable or contraindicated.

[Toric add-on intraocular lenses for correction of high astigmatism after pseudophakic keratoplasty]. / Torische AddOn-Intraokularlinsen zur Korrektur hoher Astigmatismen nach pseudophaker Keratoplastik.

Perforating keratoplasty shows good morphological results with a clear cornea; however, a limiting factor is often the resulting astigmatism, which cannot be corrected with either glasses or contact lenses (CL) in up to 20% of the patients. We retrospectively investigated 15 patients after pseudophakic perforating keratoplasty, who received implantation of toric add-on intraocular lenses (IOL) to correct astigmatism. The mean preoperative astigmatism of 6.5 diopter (dpt) could be reduced to a mean postoperative value of 1.0 dpt. The mean visual acuity could be improved from a preoperative value of sc <0.05 (cc 0.6) to a postoperative value of sc 0.4 (cc 0.63). There were no complications except for one case of a lens extension tear. Based on our good experiences we now provide toric add-on IOL to all patients with pseudophakic perforating keratoplasty when this cannot be corrected or only insufficiently corrected by conservative methods.

Measurement of visual function among patients undergoing corneal transplantation using the VF-14 index in Morocco.

OBJECTIVE: To validate the Moroccan version of the VF-14 in candidates for keratoplasty and to assess their quality of life using this tool before and after transplantation. METHODS: This is a longitudinal prospective study that assessed 57 patients who underwent penetrating keratoplasty, recruited in the ophthalmology service in Marrakech over 5 years. The original VF-14 questionnaire was adapted into Moroccan dialect. The questionnaire was administered before and 2 years after transplantation. The VF-12 questionnaire was also used, deleting the last two items. Data analysis was performed using SPSS 16.0 software. Comparisons of VF-14 scores before and after transplantation used the Wilcoxon test for paired samples. RESULTS: In total, 57 patients participated in the study. The most frequent indication for surgery was keratoconus (44%). All patients underwent penetrating keratoplasty. Chronbach's alpha value was 0.989 for VF-14 and 0.990 for VF-12. The two scores were negatively correlated with logMAR visual acuity. The strongest correlation was found with VA in the fellow eye. The average best-corrected visual acuity of the eye scheduled for keratoplasty was 1.1±0.16 logMAR. The average of VF-14 was 53±3. After keratoplasty, the average best-corrected visual acuity of operated eye was 0.34±0.31. The average postoperative astigmatism was 3 D. After keratoplasty, an increase in VF-14 score was observed from 53.5 to 81.92 (P<0.001). In postoperative follow-up, graft rejection was noted in two patients and maculopathy in a single patient. DISCUSSION: Graft transparency, absence of complications, minimal astigmatism, and good visual acuity have long been indicators of a successful corneal transplant. However, this does not provide information on visual quality and its impact on everyday life. It is in this sense that the VF-14 was adapted into several languages, as reliable, valid and sensitive as the original Anglo-American version, to assess objectively and subjectively the quality of life of patients after keratoplasty. CONCLUSION: With advances in techniques and availability of better materials, surgical success in performing keratoplasty is increasing. At the same time, vision-related quality of life of corneal graft recipients deserves more attention from ophthalmologists.

Factors Influencing Intraocular Pressure Changes after Laser In Situ Keratomileusis with Flaps Created by Femtosecond Laser or Mechanical Microkeratome.

The aim of this study is to describe factors that influence the measured intraocular pressure (IOP) change and to develop a predictive model after myopic laser in situ keratomileusis (LASIK) with a femtosecond (FS) laser or a microkeratome (MK). We retrospectively reviewed preoperative, intraoperative, and 12-month postoperative medical records in 2485 eyes of 1309 patients who underwent LASIK with an FS laser or an MK for myopia and myopic astigmatism. Data were extracted, such as preoperative age, sex, IOP, manifest spherical equivalent (MSE), central corneal keratometry (CCK), central corneal thickness (CCT), and intended flap thickness and postoperative IOP (postIOP) at 1, 6 and 12 months. Linear mixed model (LMM) and multivariate linear regression (MLR) method were used for data analysis. In both models, the preoperative CCT and ablation depth had significant effects on predicting IOP changes in the FS and MK groups. The intended flap thickness was a significant predictor only in the FS laser group (P < .0001 in both models). In the FS group, LMM and MLR could respectively explain 47.00% and 18.91% of the variation of postoperative IOP underestimation (R2 = 0.47 and R(2) = 0.1891). In the MK group, LMM and MLR could explain 37.79% and 19.13% of the variation of IOP underestimation (R(2) = 0.3779 and 0.1913 respectively). The best-fit model for prediction of IOP changes was the LMM in LASIK with an FS laser.

Toric intraocular lens rotation to optimize refractive outcome despite appropriate intraoperative positioning.

UNLABELLED: We present 3 eyes of 2 patients who benefitted from toric intraocular lens (IOL) rotation despite appropriate intraoperative positioning. In each case, preoperative astigmatism measurements were obtained by manual keratometry, partial coherence interferometry, and corneal topography. In Case 1, a dramatic shift in corneal topography occurred after surgery, resulting in the need to rotate the toric IOL to maximize the refractive outcome. In Case 2 (both eyes), no significant change in topography occurred, but IOL rotation was required to maximize the refractive outcome despite appropriate IOL alignment based on preoperative measurements. Using an online toric IOL calculator, it was determined that rotation of the IOL would result in significantly improved astigmatic outcomes. At the final evaluation 2 months after IOL rotation, the residual manifest astigmatism was 0.50 diopter (D) in Case 1 and 0 D (right eye) and 0.75 D (left eye) in Case 2. Use of the toric IOL online calculator maximized the uncorrected visual and refractive outcomes. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.

Low toric soft contact lens acceptance study.

PURPOSE: The aim of the study was to evaluate the objective and subjective visual performance of custom toric contact lenses (TL) and their spherical off-the-shelf counterparts (SL) in subjects with low amounts of astigmatism. METHODS: Twenty-three habitual soft lens wearers (40 eyes, 25-35 years) manifesting 0.50-1.00DC and ≤±3.00DS were recruited. Air Optix Aqua (Lotrafilcon B) was fit using the spherical equivalent of the manifest refraction. Intelliwave toric in Efrofilcon A (Definitive) was fit using the manifest refraction and keratometric data. Comprehensive visual performance tests were done through manifest refraction in a trial frame; in SL; and in TL. A subjective evaluation of quality of vision was also obtained. RESULTS: ANOVA revealed that, at the morning visit (AM), high contrast logMAR distance visual acuity (HCDVA) was significantly better (p<0.01) in spectacles as compared to SL. A similar trend was noted at the afternoon visit (PM). In addition, at the PM visit, HCDVA was significantly better (p<0.01) for TL as compared to their SL. ANOVA revealed that, at the PM visit, low contrast distance visual acuity (LCDVA) was significantly better (p=0.05) in spectacles as compared to SL. None of these differences were clinically significant. In addition, no statistically significant difference (p>0.05) in subjective vision rating scores was noted between SL and TL. CONCLUSIONS: The present investigation found no clinically significant difference in visual performance between spherical and toric soft contact lenses in low astigmats.

Optimizing precision in toric lens selection by combining keratometry techniques.

PURPOSE: To increase precision in toric intraocular lens selection by reducing the frequency of outliers that arise from technology-dependent variability during the preoperative assessment for routine cataract surgery. METHODS: Mean preoperative values for absolute sphere, amount of astigmatism, and steepest cylindrical axis were obtained for 87 eyes (54 patients) each with a manual keratometer and four automated keratometers. The mean sphere, amount of astigmatism, and steepest cylindrical axis across five technologies for each eye were defined as the meld sphere, meld astigmatism, and meld axis, respectively. Each technology was evaluated against the meld by Bland­Altman analysis, Student's paired t test, and correlation coefficients. Further comparison between individual technologies and the meld quantified the number of outlier measurements each technology produced. RESULTS: The number of outliers between individual keratometers and the meld differed with specific measurement of sphere, axis, or amount of astigmatism. Although statistical analysis using Bland­Altman plots, correlation coefficients, and paired t tests suggested insignificant difference from meld measurements for each parameter, precision-guided analysis presented more clinically significant outliers. The number of outliers can be reduced for sphere (range: 2%-46% to 1%-6%), astigmatism (range: 6%-23% to 0%-2%), and axis outliers (range: 15%-27% to 3%-6%) by averaging measurements from automated and manual keratometers. CONCLUSIONS: Although multiple keratometry technologies produced similar, average measurements, the authors found a disturbing number of outliers that may be overlooked when employing a single technology. Measurement errors can be dramatically reduced by averaging measurements from manual keratometry with any automated technology to make toric lens selection more precise.

Wearing time as a measure of success of scleral lenses for patients with irregular astigmatism.

OBJECTIVES: To evaluate the visual correction and clinical performance with scleral contact lenses (CL) for the visual rehabilitation of irregular astigmatism and to report the effect of brief wearing breaks on the wearing time and success rate. METHODS: A retrospective review was performed on consecutive patients who were fitted with scleral CL because of irregular astigmatism following failure of other optical corrections. Visual acuity (VA) and wearing times were abstracted. RESULTS: The 97 consecutive identified patients (155 eyes) were divided according to the diagnosis: (1) keratoconus (105 eyes; 67.7%), (2) postpenetrating keratoplasty (PK) (28 eyes; 18.1%); (3) multiple diagnoses (22 eyes; 14.2%)-postradial keratotomy, keratoglobus, pellucid marginal degeneration, PK with aphakia, and iatrogenic ectasia. The mean follow-up was 34.9 ± 18.5 months (range, 2-71 months). There was a significant increase in best VA-scleral when compared with the previous best VA-prescleral (P<0.001). The best VA-scleral was similar in the 3 groups (P>0.5). Patients who took brief breaks every 4 to 5 continuous wearing hours had a significantly higher success rate (P<0.001) among all diagnosis groups. The success rate in wearing time in the keratoconus group was significantly higher than in the PK group (P<0.001). Twenty-six patients (27%) discontinued to wear scleral lenses. CONCLUSION: Scleral lenses can be used successfully for visual rehabilitation and management of irregular astigmatism from various causative factors. The daily wearing time was significantly improved by taking brief breaks for replenishing the CL.

Toric implantable collamer lens for keratoconus.

Keratoconus is a progressive non-inflammatory thinning of the cornea that induces myopia and irregular astigmatism and decreases the quality of vision due to monocular diplopia, halos, or ghost images. Keratoconus patients unfit for corneal procedures and intolerant to refractive correction by spectacles or contact lenses have been implanted toric posterior chamber phakic intraocular lenses (PC pIOLs) alone or combined with other surgical procedures to correct the refractive errors associated with keratoconus as an off label procedure with special informed consent from the patients. Several reports attest to the safety and efficacy of the procedure, though the associated corneal higher order aberrations would have an impact on the final visual quality.

Incidence of irregular astigmatism eligible for contact lens fitting after Descemet membrane endothelial keratoplasty.

PURPOSE: To evaluate the incidence and causes of anterior corneal surface irregularities after successful Descemet membrane endothelial keratoplasty (DMEK) and the efficacy of contact lens fitting in these cases. SETTING: Tertiary referral center. DESIGN: Retrospective study of prospectively collected data. METHODS: Eyes with a subnormal visual outcome or monocular diplopia after successful DMEK were fitted with a contact lens. These cases were evaluated with Pentacam rotating Scheimpflug camera imaging preoperatively and 6 months postoperatively, and outcomes were compared with those in a randomly selected DMEK control group. RESULTS: In a series of 262 surgeries, 23 eyes (21 patients) were fitted with contact lenses; the control group comprised 23 eyes. Indications for contact lens fitting included (1) obvious corneal surface irregularities due to preexisting corneal scarring, (2) surface irregularities associated with longstanding preoperative stromal edema, and (3) undetectable optical imperfections. The postoperative corrected distance visual acuity (CDVA) with spectacles improved after contact lens correction (P<.001). Preoperative and postoperative irregularity indices were significantly higher in the contact lens group than in the DMEK control group (P<.05). Positive correlations were found between the duration of preoperative stromal edema and postoperative Scheimpflug camera indices (P<.02). CONCLUSIONS: After successful DMEK, 23 of 262 eyes (9%) showed subnormal spectacle CDVA and/or monocular diplopia due to corneal scarring, surface irregularities, or undetectable optical imperfections that could be managed by contact lens fitting. Prolonged preoperative corneal edema for more than 12 months may be a risk factor for diffuse irregular astigmatism after DMEK. FINANCIAL DISCLOSURE: Dr. Melles is a consultant to DORC International BV/Dutch Ophthalmic USA. No author has a financial or proprietary interest in any material or method mentioned.

Contribution of soft lenses of various powers to the optics of a piggy-back system on regular corneas.

PURPOSE: This study aims to report on the measured in vivo contribution of soft lenses of various powers to the optics of a piggyback system (PBS). METHODS: This prospective, non-dispensing clinical study was conducted on regular wearers of contact lenses who showed regular corneal profiles. Subjects were masked to the products used. The study involved the use of a spherical soft lens of three different powers in a PBS, used as a carrier for a rigid gas permeable lens. Baseline data were collected and soft lenses were then fitted on both eyes of each subject. Both lenses were assessed for position and movement. Over-refraction was obtained. Soft lens power contribution to the optics (SLPC) of a PBS system was estimated by computing initial ametropia, lacrymal lens, rigid lens powers and over-refraction. A set of data on one eye was kept, for each subject, for statistical analysis. RESULTS: Thirty subjects (12 males, 18 females), aged 24.4 (±4.5) years, were enrolled. The use of plus powered soft lenses enhanced initial RGP lens centration. Once optimal fit was achieved, all lenses showed normal movement. SLPC represented 21.3% of the initial soft lens power when using a -6.00 carrier, and 20.6% for a +6.00. A +0.50 did not contribute to any power induced in the system. These results are generally in accordance with theoretical model developed in the past. CONCLUSION: On average, except for the low-powered carrier, the use of a spherical soft lens provided 20.9% of its marked power. To achieve better results, the use of a plus-powered carrier is recommended.

Clinical evaluation of fitting toric soft contact lenses to current non-users.

PURPOSE: To evaluate the ease with which astigmats from three groups of current non-wearers of toric contact lenses can be fitted with current toric soft lenses, and to determine toric lens-wearing success. METHODS: This was a 1-month, randomized, bilateral, open-label, daily wear study involving 200 subjects and 16 investigational sites in the UK. Three groups of astigmatic subjects aged from 16 to 60 and with a mean age of 36 years (67 spherical soft contact lens users, SW; 72 contact lens drop-outs, DO; and 61 neophytes, Neo) were fitted with one of two toric soft lens types: a daily disposable toric soft lens (1 Day Acuvue Moist for Astigmatism, Johnson & Johnson Vision Care) or a 2-weekly replacement, re-usable toric soft lens (Acuvue Oasys for Astigmatism, Johnson & Johnson Vision Care). Subjects were evaluated after 1 month of wear and success rates calculated according to pre-set criteria for acceptable fit, orientation stability, visual acuity, quality of vision, and overall comfort. RESULTS: Eighty-eight percent of lenses were fitted at the first attempt. Of 198 subjects dispensed with lenses, 182 (92%) completed the study. When analysed by subject group, the success rates according to the pre-set criteria were 80% (53/66), 74% (52/70), and 70% (39/56) for the SW, DO and Neo groups respectively. Comfort was the most common reason for failure with all three groups; however, visual problems were more common in the DO and Neo groups (13% vs 6%). VA with the study lenses was significantly better in the SW group compared to their habitual lenses. For the DO and Neo groups combined (i.e. spectacle wearers), visual acuity was comparable to their habitual spectacles. CONCLUSIONS: A high proportion of astigmats who are not using toric soft contact lenses can be fitted with current lenses. Previous contact lens drop-outs and neophyte wearers achieve visual acuity comparable to spectacles when fitted with toric soft lenses. Spherical contact lens wearing astigmats achieve superior visual acuity when refitted with toric soft lenses. These findings suggest that many astigmats who are not currently using toric soft contact lenses could do so successfully.

An international survey of toric contact lens prescribing.

OBJECTIVES: To characterize toric contact lens prescribing worldwide. METHODS: Up to 1,000 survey forms were sent to contact lens fitters in up to 39 countries between January and March every year for 5 consecutive years (2007-2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Only data for toric and spherical soft lens fits were analyzed. Survey data collected since 1996 were also analyzed for 7 nations to assess toric lens fitting trends since that time. RESULTS: Data were collected in relation to 21,150 toric fits (25%) and 62,150 spherical fits (75%). Toric prescribing ranged from 6% of lenses in Russia to 48% in Portugal. Compared with spherical fittings, toric fittings can be characterized as follows: older age (29.8 ± 11.4 years vs. 27.6 ± 10.8 years for spherical lenses); men are overrepresented (38% vs. 34%); greater proportion of new fits (39% vs. 32%); use of silicone hydrogel lenses (49% vs. 39%); and lower proportion of daily disposable lenses (14% vs. 28%). There has been a continuous increase in toric lens prescribing between 1996 and 2011. The proportion of toric lens fits was positively related to the gross domestic product at purchasing power parity per capita for year 2011 (r = 0.21; P=0.004). CONCLUSIONS: At the present time, in the majority of countries surveyed, toric soft contact lens prescribing falls short of that required to correct clinically significant astigmatism (≥ 0.75 diopters) in all lens wearers.