Soft Contact Lens Fitting Research Articles

Is it possible to calculate the sagittal height for soft contact lens fitting? Validation of a theoretical calculator: Sagitador

Is it possible to calculate the sagittal height for soft contact lens fitting? Validation of a theoretical calculator: Sagitador

A Corneal Biomechanical Study Measured with a Scheimpflug Dynamic Analyser in Soft Contact Lens Wearers.

The aim of this study was to evaluate the biomechanical changes in the cornea after wearing soft contact lenses (CLs) in healthy myopic patients measured with a Corvis ST® (CST, Oculus Optikgeräte GmbH, Wetzlar, Germany) analyser. This prospective, cross-sectional, single-centre study was performed on twenty-two Caucasian patients aged between 19 and 24 years (20.64 ± 1.21 years) range. Five device-specific biomechanical parameters, the central corneal thickness (CCT), and biomechanically corrected intraocular pressure (bIOP) were measured prior to fitting and one month after CL wear. Differences between the means of the deflection amplitude ratio (DA Ratio) and the standard deviation of the DA Ratio (SD DA Ratio) pre- and post-CL wear were found to be significant (p value = 0.002 in both cases). Significant differences were found between pre- and post-CL wear values in CCT (p value = 0.013). For all other biomechanical measures, no significant differences were observed before and after treatment. A significant association was found between changes in bIOP and classification according to changes in Int. Radius (p value = 0.047) and SSI (p value = 0.026) standard deviations. The corneal biomechanical indices provided by CST demonstrate that the fitting of soft CLs is a safe optical compensation method for the stability of corneal stiffness. No significant differences were found pre- and post-CL wear in the assessment of bIOP.

Retracted: Effects of Medium-Term Soft Contact Lens Fitting on Dry Eye: Analyses Using Ultra-High Resolution Optical Coherence Tomography and Digital Slit-Lamp Biomicroscopy.

[This retracts the article DOI: 10.1155/2022/7220706.].

Guide and tools for comprehensive toric soft contact lens fitting

Contact lens options for astigmatic patients include commercially available toric soft contact lenses, custom soft contact lenses, rigid corneal and scleral contact lenses. Wide range of parameters and modalities of modern soft toric lenses covers more than 90 % of patients with astigmatism. It makes toric soft contact lenses most available and convenient option for eyecare specialists.Purpose of this publication is to review main steps of toric lens fitting and remind ECP about useful tools and services designed to reduce chair time.

MICROBIAL BIOBURDEN OF ORTHOKERATOLOGY AND HYDROGEL CONTACT LENSES AND STORAGE CASES USING A HYDROGEN-PEROXIDE DISINFECTING SYSTEM

Background and objective: The fitting of orthokeratology (ortho-k) and multifocal soft contact lenses (SCL) is becoming increasingly popular worldwide for reducing the rate of myopia progression. However, overnight wear use of lenses and microbial contamination of contact lenses and storage vials has been shown to increase the risk of corneal inflammatory and infiltrative events (CIEs). Therefore, we conducted a pilot study to compare the rate, level, and type of microbial contamination of contact lenses and storage vialswhen participants wear ortho-k and SCL in combination with a hydrogen-peroxide disinfecting system.
 Material and Methods: A prospective, single-centre, randomized, crossover study was conducted to evalu-ate the rate and level of contact lens and storage vials contamination during the use of ortho-k and SCL along with a hydrogen-peroxide disinfecting solution over two 10 day wearing periods. Ocular signs and symptoms were assessed during lens wear at baseline and after each wearing period. In addition, contact lens and storage vials were collected, and the type and amount of microbial contamination were evaluated using viable culture and standard identification methods.Results: Twenty-five adults were enrolled, and 21 completed the study. One (5%) ortho-k lens, five (24%) ortho-k storage vials, one (5%) SCL and one (5%) SCL storage vial were contaminated (P > 0.05), predominantly with Gram-positive bacteria. None of the participants had contamination with both ortho-k and SCL. No significant differences were found between the ocular signs, including conjunctival redness and roughness, or conjunctival or corneal staining (all P > 0.05), irrespective of using ortho-k or SCL.
 Conclusion: This study provides the first data that directly compares microbial contamination of ortho-K versus SCL in patients using a hydrogen-peroxide disinfection system. However, the overall microbial contamination rate of contact lens storage vials was much lower (30%) than the previously reported study with ortho-k lens wear. The results support conducting a larger clinical trial designed to understand differences in microbial contamination with different lens materials and modalities.

A Study on the Relationship between Corneal-Related Value and Ocular Sagittal Height

Purpose : To investigate the effect of corneal related values on the ocular sagittal height and which factors have the greatest influence on the ocular sagittal height. Methods : For 240 healthy eyes in their 20, 30, 40, and 50s, the anterior chamber depth and axial length were measured with IOLMaster 700. The corneal curvature radius and corneal eccentricity were measured with Keratograph 4, and spherical equivalent power was measured using KR-800. The corneal sagittal height was calculated using the formula. Results : The most influential factor in the corneal sagittal height was the corneal diameter, followed by the corneal eccentricity. And the corneal curvature radius had the least effect. A change in corneal saggital height of about 0.10mm corresponds to a change in corneal diameter of 0.20mm, and corneal eccentricity of 0.05 to 0.10 Conclusion : If soft contact lens fitting is greatly affected by the relationship between the sagittal depth of the contact lens and the sagittal height of the cornea, measurements of corneal diameter and corneal eccentricity are considered appropriate methods for selecting parameters of contact lenses. In addition, the numerical relationship between corneal sagittal height, corneal diameter and corneal eccentricity could be used as additional information for soft contact lens fitting.

“OKVision OKV-SL” customizable soft contact lenses fitting guide

The purpose of this guide is to introduce ophthalmologists and optometrists to the basics of fitting of customizable soft contact lenses, which is an important knowledge that enhances practitioners’ skills and helps provide a high visual acuity for many patients.Material and methods. This guide sets forth the principles of calculation of contact lens parameters, defines parameters specific to customizable lenses as well as assessment of the fit and the rules of lens handling and care.Conclusions. Following the fitting guide ensures a successful vision correction with customizable soft contact lenses for both doctor and the patient.

Corneoscleral Topography Measured with Fourier-based Profilometry and Scheimpflug Imaging.

Precise measurement of corneoscleral topography makes a valuable contribution to the understanding of anterior eye anatomy and supports the fitting process of contact lenses. Sagittal height data, determined by newer noninvasive techniques, are particularly useful for initial scleral lens selection. The purpose of this study was to investigate the agreement and repeatability of Fourier-based profilometry and Scheimpflug imaging, in the measurement of sagittal height and toricity of the corneoscleral region. Minimal (Minsag), maximal (Maxsag) sagittal height, toricity (Maxsag - Minsag), and the maximum possible measurement zone diameter of 38 subjects were compared using the Eye Surface Profiler (ESP; Eagle Eye, Houten, the Netherlands) and the corneoscleral profile module of the Pentacam (Oculus, Wetzlar, Germany) at two different sessions. Correlations between the instruments were analyzed using the Pearson coefficient. Differences between sessions and instruments were analyzed using Bland-Altman and paired t tests. For an equal chord length, the measurement with Pentacam was significantly greater for Minsag (344 μm; 95% confidence interval [CI], 322 to 364 μm; P < .001) and significantly greater for Maxsag (280 μm; 95% CI, 256 to 305 μm; P < .001), but significantly smaller for toricity (-63 μm; 95% CI, -95 to -31 μm; P < .001). Maximum possible measurement zone diameter with ESP (16.4 ± 1.3 mm) was significantly greater than with Pentacam (14.8 ± 1.1 mm) (P < .001). Repeated measurements from session 1 and session 2 were not significantly different for Pentacam and ESP (P = .74 and P = .64, respectively). The 95% CIs around differences indicate good repeatability for Pentacam (mean difference, -0.9 μm; 95% CI, -6.7 to 4.8 μm) and ESP (4.6 μm; -22.4 to 31.6). Although both instruments deliver useful data especially for the fitting of scleral and soft contact lenses, the sagittal height and the toricity measurements cannot be considered as interchangeable.

Essential contact lens practice 8: Soft toric contact lens fitting

In the eighth article in our major series about modern contact lens practice edited by Dr Rachel Hiscox, Dr Katharine Evans discusses the correction of astigmatism with soft toric contact lenses.

Essential contact lens practice 7 – Soft contact lens fitting

In the seventh article in our major series about modern contact lens practice edited by Dr Rachel Hiscox, Dr Byki Huntjens offers a practical overview of the key aspects and principles associated with spherical soft contact lens fitting.

Hybrid contact lenses for the correction of primary and induced ametropias

The review presents the data on the use of hybrid contact lenses (HCL), a modern method of contact correction of ametropias of diverse origins. A HCL has a central rigid optical zone made of highly gas-permeable material and a flexible peripheral part made of hydrophilic material. These lenses combine the optical effect of gas-permeable corneal lens with the comfort and stable fitting of soft contact lenses. Compared with the corneal (RGP) lenses, HCLs are more comfortable, often are better centrated and more stably fit on the eye. HCLs are successfully used in various refractive disorders: ametropias (with regular cornea), irregular astigmatism, presbyopia, including that combined with astigmatism. This type of lens is a good option of contact correction for patients who have high requirements to the quality of vision.

각공막 측면부가 소프트 콘택트렌즈 피팅에 미치는 영향에 관한 연구

각공막 측면부가 소프트 콘택트렌즈 피팅에 미치는 영향에 관한 연구

소프트 콘택트렌즈 처방에서 베이스커브, 직경 등의 변화에 대한 유효성 평가

소프트 콘택트렌즈 처방에서 베이스커브, 직경 등의 변화에 대한 유효성 평가

Corneal morphology and visual outcomes in LASIK patients after orthokeratology: A pilot study.

For the first time, this study shows that corneas that previous undergone orthokeratology treatment do not respond differently to LASIK compared with previous soft contact lens wear experience. To evaluate and compare the corneal morphology and visual outcomes of long-term soft and orthokeratology (OK) contact lens fitting in wearers undergoing corneal refractive surgery (LASIK) for myopia correction. Sixteen (16) myopic patients wearing hydrophilic soft contact lens (SCL, n = 8 subjects, control group) and OK (n = 8 subjects, OK group) lenses who undergone LASIK were retrospectively evaluated. Preoperative fitting of contact lenses and one year postoperative were studied using Pentacam (Oculus, Inc. GmbH, Wetzlar, Germany). Corneal pachymetry and volume, corneal topography, anterior and posterior surface elevation data and the anterior surface aberrometry of the cornea were recorded and used for fitting. Age, refractive error and topographic parameters before LASIK did not showed statistically significant differences between the two study groups. LASIK post-treatment results showed identical changes in both control and OK groups and did not show significant differences in all the parameters evaluated. The changes on corneal parameters and HOA due to refractive surgery intervention were not different between Control and OK group (p > 0.050). Corneal changes due to OK treatment are reversible after its discontinuation. The present study gives an overview of how OK does not impair future LASIK surgery for the correction of myopia and does not influence the success/results of such intervention. These findings suggest that OK CL wear does not change corneal biomechanics and does not compromise a possible LASIK refractive surgery. Although this is a pilot study and there is a need of evaluate this results/changes in future studies.

Effects of corneoscleral topography on soft contact lens performance: A pilot study

To quantify corneoscleral junction (CSJ) topography in soft contact lens (SCL) wearers, and assess the association between the CSJ and SCL performance and subjective comfort, forty-four adapted SCL wearers (16 Asians, 16 Caucasians, 12 Latinos) were recruited for the present study. Corneal topography was taken with a Medmont E300 (Medmont International, Pty Ltd.). CSJ images were taken with a commercial OCT (Bioptigen, Inc.). Our published CSJ image analysis technique was used to describe the geometric properties of the CSJ using the sum of squared orthogonalized residuals (SSRo). Multivariable mixed effects models were employed to examine associations between SSRo and subject demographics, ocular characteristics, SCL fit and performance, and comfort. The SSRo was significantly related to quadrant (p < 0.001), ethnicity (p = 0.014), and horizontal corneal shape factor (p = 0.044). The nasal quadrant had the largest SSRo, indicating the steepest CSJ profile and/or the most irregular CSJ surface, followed by the inferior quadrant. The superior and temporal quadrants had the smallest SSRo, indicating relatively flat and even CSJ topography. Caucasians had the steepest and/or most irregular CSJ compared with Latinos and Asians. Less inferior-superior heterogeneity in the SSRo was associated with greater comfort after 6 h of lens wear. The SSRo was proved to be a useful tool to quantify CSJ geometry in SCL wearers. Significant differences in the SSRo were found among quadrants and ethnic groups. Better subjective comfort after 6 h of SCL wear was associated with a smaller difference in the SSRo between the superior and inferior quadrants.

What constitutes an adequate initial soft contact lens fit?

Purpose: Recent research has defined the key clinical metrics that full describe soft lens fit more efficiently. However, lens fit is known to change with time after lens insertion so the stability of these metrics over the course of the day is needed to determine the adequacy of an initial fit for prescribing the lens for a trial.

Inter-observer agreement of soft contact lens fit assessment

Purpose: Soft contact lens fit assessment and recording varies among clinicians. The aim of this study is to compare the inter-student variation in contact lens grading using two scales, a traditional scale (using mm or % estimation) and a three point grading scale. Methods: Forty-four second year optometry students with 10 weeks of contact lens experience participated in this study evaluating 6 different lens fits of daily and reusable commercially available soft contact lenses. Students evaluated up-gaze blink, push-up (displacement) and horizontal lag and were randomly assigned to use the traditional or three point grading scale. Students were briefed prior to the study to ensure scale interpretation consistency. The study was time-controlled and after a 3-minute slit-lamp set-up, students received 1-minute for the measurement of each aspect of the fit. Results: Inter-observer agreement was assessed using: a) concordance and 95% confidence intervals of paired observations and b) intra-class correlation (ICC) statistic. The three-point scale showed a higher concordance than the traditional scale for all but the horizontal lag measurement (up-gaze blink 32% vs 11%, push-up 43% vs 11% and horizontal lag 36% vs 43%). The 95% confidence intervals for the traditional scale were narrower than that of the three-point scale (up-gaze blink 0.4mm vs 1.8, push-up 43% vs 1.8 and horizontal lag 0.3mm vs 1.9). The ICC was higher for the traditional scale (horizontal lag 0.42 vs 0.28 and push-up 0.49 vs 0.20) but slightly lower than the three-point scale for the blink in up-gaze (0.77 vs 0.88). Conclusions: Overall, the three point scale showed higher concordance indicating higher agreement between randomly paired student observations. However, the 95% confidence interval was wider as compared to the traditional scale reducing the ability to detect clinical change. Thus, our results suggest that the traditional scale is preferable during Optometrist’s training.

Key moments in soft toric contact lens fitting

Elizabeth Lumb offers a refresher for toric contact lens fitting, emphasising the key points to consider during the process.

Putting the skill back into soft lens fitting

Has the one-size-fits-all philosophy led to an over-simplification of soft contact lens fitting? As it celebrates its 20th anniversary, mark'ennovy convened a European roundtable meeting in Madrid to find some answers.

Inter-relationship of Soft Contact Lens Diameter, Base Curve Radius, and Fit.

To evaluate the inter-relationship of soft contact lens base curve radius (BC), diameter, and lens fit using a mathematical model. A spreadsheet mathematical model was used to evaluate theoretical fitting characteristics for various combinations of soft lens BC and diameter. The designs were evaluated using ocular topography data collected from 163 UK subjects. The model evaluated lens tightness (edge strain) and on-eye diameter (horizontal corneal overlap) and assumed that acceptable values fell within the range 0 to 6% and 0.2 to 1.2 mm, respectively. Analyses were undertaken of various trends relating to soft lens fit, including (1) the effect of BC and diameter on fitting success; (2) the effect of lens asphericity, BC, and sag on lens diameter on the eye; and (3) the effect of lens diameter on lens tightness. The highest overall success rate (90.2%) was achieved with an 8.60/14.2 mm (BC/diameter) design. Using this design on the sample population, the median edge strain value was 3.2% (IQR: 2.1%) whereas median corneal overlap was 0.62 mm (IQR: 0.35). There was a positive correlation (r = 0.37, P < .0001) between edge strain and corneal overlap. Edge strain showed significant correlations with each of the ocular topography variables, most notably corneal asphericity (-0.62, P < .0001). Corneal overlap showed significant correlations with corneal asphericity (r = -0.42, P < .0001) and corneal diameter (r = 0.92, P < .0001). For a 0.4 mm change in BC, it is necessary to change diameter by 0.2 mm to maintain similar on-eye diameter (arclength). When changing lens diameter, a change in BC of 0.2 mm is required to maintain similar tightness of fit. Mathematical modeling is a useful technique for large-scale evaluation of the interactions of soft contact lens design and fit. The study has given useful insights into the general performance of soft lens designs.