Rigid Gas Permeable Research Articles

Kayser\u2013Fleischer ring with keratoconus: a coincidence? A case report

BackgroundIt is rare for hepatolenticular degeneration [Wilson’s disease (WD)] to occur along with keratoconus (KC). In our report, a teenager was diagnosed with WD because of the discovery of Kayser–Fleischer (KF) ring in the cornea, and concomitant KC was found.Case presentationA 19-year-old male was diagnosed with KC due to a rapid decline in visual acuity within a short period of time. Ocular examination revealed the presence of ring-shaped, dense, brown sediment at the Descemet membrane of the bilateral limbus cornea, exhibiting characteristics similar to those of KF ring. Then, the patient was referred to the Department of Neurology and diagnosed with asymptomatic WD. During the next 5 years of follow-up, the patient has worn RGP lenses, routinely taken drugs that inhibit copper absorption and promote copper excretion, and maintained a low-copper diet. He has never exhibited obvious systemic symptoms associated with WD, such as neurological, mental, or hepatic dysfunction, and the color of the KF ring has grown obviously lighter. Moreover, the morphology of the cornea has stabilized.ConclusionOnly one report of WD combined with KC was found in the literature. So far, there is no evidence of a correlation between the occurrence of the two diseases. However, a low-copper diet and active copper-reducing therapy may have played a role in stabilizing the patient’s condition in this case.

Multi-view deep learning for rigid gas permeable lens base curve fitting based on Pentacam images.

Many studies in the rigid gas permeable (RGP) lens fitting field have focused on providing the best fit for patients with irregular astigmatism, a challenging issue. Despite the ease and accuracy of fitting in the current fitting methods, no studies have provided a high-pace solution with the final best fit to assist experts. This work presents a deep learning solution for identifying features in Pentacam four refractive maps and RGP base curve identification. An authentic dataset of 247 samples of Pentacam four refractive maps was gathered, providing a multi-view image of the corneal structure. Scratch-based convolutional neural network (CNN) architectures and well-known CNN architectures such as AlexNet, GoogLeNet, and ResNet have been used to extract features and transfer learning. Features are aggregated through a fusion technique. Based on a comparison of means square error (MSE) of normalized labels, the multi-view scratch-based CNN provided R-squared of 0.849, 0.846, 0.835, and 0.834 followed by GoogLeNet, comparable with current methods. Transfer learning outperforms various scratch-based CNN models, through which proper specifications some scratch-based models were able to increase coefficient of determinations. CNNs on multi-view Pentacam images have enabled fast detection of the RGP lens base curve, higher patient satisfaction, and reduced chair time. Graphical abstract The Pentacam four refractive maps is learned by the proposed scratch-based and transfer learning-based CNN methodology. The deep network-based solutions enable identification of rigid gas permeable lens for patients with irregular astigmatism.

Myopia control in the 21st century: A review of optical methods (2000–2019)

Background: Without appropriate interventions, simple or low myopia can progressively get worse and lead to high myopia. Patients with high myopia are at a greater risk of developing retinal detachment, myopic macular degeneration, glaucoma and eventual blindness in some cases, and hence the reason for the global call for myopia control. Consequently, myopia in the 21st century is not only treated as a refractive error but an ocular disorder with potential negative consequences. Myopia control strategies include optical, pharmacological and behavioural methods. In this report, the effectiveness of optical methods of myopia control was reviewed. Aim: The aim of the review is to evaluate and summarise existing knowledge on myopia control and provide recommendations to guide future studies. Method: The review was conducted using online search engines including PubMed and Google Scholar. Articles published between 2000 and 2019 were included. Results: For the optical methods of myopia control, under-correction has been found to be largely ineffective. However, a recent study shows that myopic children without correction had slower myopia progression (−0.75 D) than fully corrected children (−1.04 D) indicating a 28% reduction. Evidence from various studies indicates that bifocals and progressive addition lenses are not as effective as soft dual focus contact lenses or extended depth of focus contact lenses. Clinical trials indicate that single vision rigid gas permeable lenses did not slow myopic progression. Peripheral defocus lenses and orthokeratology were found to be approximately 50% effective across studies reviewed. Conclusion: Peripheral defocus lenses and multifocal contact lens designs offer the most effective myopia control. Orthokeratology is equally effective but future designs should consider ways of minimising risks of complications with lens wear. More studies would be needed to better understand how under-corrected myopic eyes tend to progress faster, whereas myopic eyes without correction tend to progress slower. A holistic approach and combination of methods may offer the best form of myopia control in the 21st century considering the increase in near work activities and use of digital devices among the most vulnerable groups.

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.

Microbial Contamination of Rigid Gas Permeable (RGP) Trial Lenses and Lens Cases in China

ABSTRACTPurpose: This study aimed to evaluate the microbial contamination level and its influencing factors of rigid gas permeable (RGP) trial lenses and lens cases in China.Materials and Methods: A total of 107 RGP trial lenses and lens cases were collected from 7 main hospitals or optometric centers in China. Three sites including the lenses, case interiors and case screw tops were sampled for bacterial and fungal culture and identification. The contamination rates of these three sites and their relationship with lens care regimes were further analyzed.Results: The overall contamination rate was 73.8% for either lenses or cases, and 43.0% of lenses, 57.0% of case interiors and 65.4% of case screw tops respectively. The most frequently isolated microorganisms were Serratia spp., Burkholderia spp., Pandoraea spp., and Achromobacter spp. from all three sites. The contamination rate was positively related to the lens use frequency. Compared with dry-stored lenses, the contamination rate was significantly higher in wet-stored group (P < .001*). Inadequate disinfection and improper lens and case care regimes were also associated with higher contamination rates.Conclusions: Our study reported that the RGP trial lenses and cases used for fittings had a considerably high contamination rate. The safe use of RGP trial lenses and education of optometrists on the regular maintenance of trial lenses should be emphasized.

Correction of Irregular Astigmatism With New-Generation Hybrid Contact Lenses.

To evaluate the safety, efficacy, and on-eye performance of new-generation hybrid contact lenses (HCLs) in visual rehabilitation of eyes with irregular astigmatism and rigid gas-permeable (RGP) contact lens intolerance or failure. The charts of patients who had been fit with new-generation HCLs were retrospectively reviewed. The reason for HCL fit and previous method of correction were noted. After the initial on-eye evaluation, visual and refractive outcomes, slit-lamp biomicroscopy, and lens comfort were evaluated at the last follow-up examination. Forty-seven eyes of 33 patients could be fit successfully with EyeBrid silicone (LCS, Cane, France) or Airflex (SwissLens, Prilly, Switzerland) lenses. The mean number of trial lenses required for ideal fit was 1.4±0.6 (range; 1-3) lenses. The reason for fit was either centration problems with RGP lenses or RGP intolerance. Twenty-nine eyes of 20 patients (72.5%) continued wearing their lenses more than 10 hr a day and for more than 3 months. In these successful wearers, the visual acuity (VA) improved significantly compared with the baseline uncorrected and spectacle-corrected VA (P<0.01), and no serious adverse events were encountered during the mean follow-up period of 10.1±6.4 months. At the last follow-up examination, patients preferred the new-generation HCLs over their habitual correction in regard to both VA and quality (P<0.05). New-generation HCLs seem to provide a viable alternative for visual rehabilitation of irregular astigmatism in selected eyes with RGP intolerance or RGP failure. The ease of the fitting process similar to fitting soft toric lenses and high patient satisfaction seem to be major advantages of these designs.

An image processing approach for rigid gas-permeable lens base-curve identification

This research is aimed at accurate identification of base-curve in rigid gas-permeable (RGP) lens based on supervised image processing and classification of Pentacam four refractive maps in irregular astigmatism cases. Base-curve, is typically identified based on expert’s opinion of the corneal structure of the eye. Studies have applied time-consuming methods, focusing on manual and device-based techniques. For the identification of the base-curve of a lens, image analysis is proposed. As each map in the four refractive maps is of a singular view, multi-view learning is recommended to provide a single representation. To this end, an authentic dataset consisting of 247 labeled Pentacam four refractive maps was gathered in which labels were verified manually. We have proposed two novel feature extraction techniques in this domain: quantization-based radial–sectoral segmentation (QRSS) in image processing and deep convolutional neural networks. Feature fusion is applied and RGP base-curve is identified by the regression layer of a neural network. A combination of QRSS and multilayered perceptron delineates the best result, achieving a coefficient of determination of 0.9642 and satisfactory mean square error (0.0089) which is acceptable by the experts. The proposed multi-view model could improve base-curve detection accuracy, with less trial and error and patient visits in the lens fitting process.

Short-term changes in topometric indices after discontinuation of rigid gas permeable lens wear in keratoconic eyes.

Purpose:To estimate the time taken for topometric indices to stabilize in keratoconic corneas following cessation of habitual RGP contact lens wear.Methods:A total of 29 eyes of 20 patients, diagnosed with mild to severe keratoconus were included in this prospective observational study. All patients were experienced RGP contact lens wearers (either conventional RGP or Rose K2 lens) with each patient having used these lenses for at least a year. Corneal topography was performed immediately following discontinuation of habitual contact lens wear at baseline and each of four consecutive visits, 1-week apart.Results:An overall reduction in the keratometry and thickness values were noted on tomography immediately following cessation of contact lens wear and these indices increased significantly in the 1st week (P < 0.001). Consecutive visits following the first visit did not show any significant change in the topometric parameters (P > 0.05). Subgroup analysis revealed a similar trend in eyes with “severe” keratoconus and in eyes fitted with the “three-point touch” philosophy. However, eyes with “mild-moderate” keratoconus and those fitted with “apical clearance” fitting philosophy showed marginal differences even within the 1-week period of lens cessation.Conclusion:Maximum changes in keratometry and pachymetry values following discontinuation of RGP lens wear stabilize within the 1st week of cessation of rigid lens wear in a keratoconic cornea. These changes were more pronounced in patients with severe keratoconus and those with an apical bearing fit. This information would be useful for practitioners to assess the progression of keratoconus in RGP lens users before collagen cross-linking.

Profile and Performance of Rigid Gas Permeable and Scleral Lenses on Keratoconic Patients in the Developing Contact Lens Practice Settings

Purpose: To present the profile of keratoconic contact lens wearers, alongside with performance of corneal and scleral rigid gas permeable (RGP) at different stages of keratoconus based on limited diagnostic resources. Methods: 5-year Clinical records of keratoconic corneal and scleral RGP contact lens wearers were retrieved. Data on age, gender, visual acuity (VA), refraction (RE), stage of keratoconus and mode of correction among other variables were obtained for analysis. Information pertaining to the outcome in pre and post-fit at different severity was determined. Results: A total of 124 medical records were analyzed, with the age (20.86 ± 9.50 years), gender (58.9% male and 41.1% female), Laterality (57.3% bilateral, 26.6% right eye and left eye as 16.1%) and ethnicity (91.1% Africans and 8.9% Asians). There were no significant differences in effects of lenses (RGP and Scleral lenses) across three stages in visual acuity and in three stages of severity HRGP (2) = 1.05, p = 0.59; HScleral (1) = 2.24, p = 0.134. Similar non-significant effect was observed in refractive error correction HRGP (2) = 1.62, p = 0.44: HScleral (1) = 1.143, p = 0.285. Conclusion: The profile of KC contact lens wearer was comparable to other studies in developing setting. Keratoconic grading should be based on available resources. Corneal rigid gas permeable and scleral lenses were beneficial to keratoconic patients in respect of refractive error correction and visual improvement to keratoconic patient.

A new technique for fitting of tricurve rigid gas-permeable contact lens in penetrating keratoplasty eyes using Scheimpflug imaging.

Purpose:Rigid gas-permeable (RGP) contact lens fitting after penetrating keratoplasty (PK) is challenging due to significant irregular astigmatism. The aim of the study was to determine a guideline for selecting the initial base curve (BC) of the RGP contact lens fitting in post PK eyes.Methods:The data of patients who had tricurve RGP contact lens fitting post PK were collected retrospectively. The following data were collected: best-corrected visual acuity with glasses and contact lenses; contact lens parameters which included the BC and diameter; corneal topography parameters which included steep keratometry value (K), flat-K, and mean-K; and anterior best fit sphere (BFS) measured using Scheimpflug imaging.Results:The median age of the 40 subjects (46 eyes) who met the inclusion criteria was 37.5 years (IQR 26.7–45.5). The spherical equivalent was –3.00 diopter (D) (–8.31 to –1.56). The median steep-K, flat-K, and mean-K in them were 6.76 mm (6.28–7.07), 7.78 mm (7.37–8.14), and 7.26 mm (6.93–7.46), respectively. The median anterior BFS value of the transplanted cornea was 6.96 mm (6.6–7.37). The median BC of the final RGP lens was 7.0 mm (6.7–7.23) and the median diameter was 9.8 mm (9.4–10.4). Among all the Scheimpflug imaging parameters, the BFS correlated well with the final BC of the RGP contact lens dispensed (R 0.742, P < 0.0001).Conclusion:The anterior corneal surface BFS value can be used as a reference in selecting the initial BC of tricurve RGP contact lens to achieve the best fitting and reducing the chair time of patients after PK.

Modern options for non-surgical correction of keratoconus

The article reviews data on the so called non-surgical methods of keratoconus (KC) correction. The combined approach to KC treatment entails three main tasks: prevention of progression, optical correction of induced refractive disorders, and structural repair. Measures taken to accomplish the first two tasks should be regarded as symptomatic treatment, while addressing the last task requires pathogenetically oriented solutions. Corneal cross-linking and optical correction of refractive disorders with rigid gas permeable (RGP) scleral contact lenses should be regarded as the first choice for symptomatic non-surgical correction of keratoconus.

On the question of progressive hyperopia correction after radial keratotomy

Progressive hyperopia development in the long-term period after radial keratotomy (RC) is associated with not only surgical effects, but also individual biomechanical features of the fibrous tunic of the eye, its age-related changes, and hydrodynamic disturbances. When choosing a method of correction, one should take into account a number of features characteristic of this induced refractive disorder: instability and irregularity of refraction, coexisting presbyopia, and, in some cases, anisometropia. Correction of progressive hyperopia after RC can be achieved with eyeglasses, or contacts, or intraocular lenses depending on the subjective factor - the so-called patient adherence. The most effective in terms of functionality is contact correction with scleral rigid gas-permeable lenses, and in the presence of pronounced lens opacities - intraocular correction.

Fluoro-siloxanyl Styrene Rigid Gas Permeable Contact Lens Fabric characteristics and outcomes with extended use on animal model cornea

In this paper, we report the relation between fabric characteristics and animal model cornea modifications associated with extended use of fluoro-siloxanyl styrene rigid gas permeable contact lens. Siloxanyl styrene and fluoromethacrylate rigid gas permeable contact lens is a newly designed optical medical device used in orthokeratology with an FDA approval of continuous wear for up to 30 days. To assess the influence on the cornea an animal model was used and histological data were collected. Scanning electron microscopy (SEM) was performed on the used lenses. Our conclusions concedes that with respects of the material, doctor�s slit lamp lens observation on regular basis should be considered as surface debris and lens scratches can influence the cornea in extended wear.

Fluoro-siloxanyl Styrene Rigid Gas Permeable Contact Lens Fabric characteristics and outcomes with extended use on animal model cornea

In this paper, we report the relation between fabric characteristics and animal model cornea modifications associated with extended use of fluoro-siloxanyl styrene rigid gas permeable contact lens. Siloxanyl styrene and fluoromethacrylate rigid gas permeable contact lens is a newly designed optical medical device used in orthokeratology with an FDA approval of continuous wear for up to 30 days. To assess the influence on the cornea an animal model was used and histological data were collected. Scanning electron microscopy (SEM) was performed on the used lenses. Our conclusions concedes that with respects of the material, doctor’s slit lamp lens observation on regular basis should be considered as surface debris and lens scratches can influence the cornea in extended wear. Keywords: siloxanyl styrene and fluoromethacrylate, rigid gas permeable contact lens, surface debris, extended

Cytomorphological assessment of the lid margin in relation to symptoms, contact lens wear and lid wiper epitheliopathy

Purpose: Lid wiper epitheliopathy (LWE) is insufficiently understood from a cytological perspective. This study explored the relationship between lid margin cytomorphology, LWE, contact lens wear, and lens-related symptoms.Methods: Habitual, symptomatic (n = 20) and asymptomatic (n = 20) soft, rigid gas permeable (n = 18) and non-contact lens wearers (n = 19) were enrolled. LWE was graded using lissamine green and the Korb scale. Subjective symptoms were assessed using the Ocular Surface Disease Index and the Contact Lens Dryness Evaluation Questionnaire. Impression cytology samples obtained from the central upper and lower lid margins of both eyes stained histologically to highlight keratinization and imaged using high-resolution microscopy. A masked investigator digitally delimited and measured the average sagittal width of the lid wiper conjunctiva and mucocutaneous junction using ImageJ. Results:The upper lid wiper conjunctiva measured 424 ± 171 μm, 404 ± 75, 667 ± 219 and 266 ± 64 in asymptomatic soft, symptomatic soft, rigid and non-contact lens wearers, respectively. The corresponding lower lid wiper conjunctivae measured 141 ± 57 μm, 232 ± 150, 519 ± 212 and 225 ± 102, which was significantly narrower than that of the upper eyelid in most cases (p < 0.05). Symptoms were not associated with lid margin changes; however, rigid lens wear and clinical LWE were associated with histologically enlarged lid wiper conjunctival areas and increased keratinization.Conclusion: A novel, exploratory account of histological measures of LWE and cytomorphological change associated with contact lens wear suggests mechanical or frictional cellular insult is occurring at the lid wiper conjunctiva.

Anterior best fit sphere–Is it a better starting point to fit rigid gas permeable contact lens in penetrating keratoplasty eyes?–A clinical observation

Purpose: Rigid gas permeable (RGP) contact lens fitting after penetrating keratoplasty (PK) is challenging due to significant irregular astigmatism. The aim of the study was to identify a corneal topography parameter for predicting the initial base curve (BC) of RGP contact lens in post PK eyes.

To rub or not to rub? - effective rigid contact lens cleaning.

To compare the efficacy of cleaning of rigid contact lenses using two care solutions with and without rubbing. A masked randomised trial was conducted. The cleaning efficacy of two solutions recommended for rigid contact lenses, a one-step hydrogen peroxide solution (HP) and a povidone iodine-based solution (PI), were evaluated on 64 unworn orthokeratology (ortho-k) lenses subsequent to cleaning with rubbing (R) with a surfactant cleaneror without rubbing (NR). Either mascara or hand cream was applied as a contaminant to the lenses to simulate stubborn and loosely bounded deposits, respectively. For each type of deposit, the lenses were randomly assigned to four cleaning treatments: R with HP, NR with HP, R with PI, and NR with PI (n=8 for each group). Each lens surface was assessed on site by a masked examiner under a low-magnification slit-lamp and with photo-documentation. Lenses were graded according to the deposit coverage area using a pre-set five-point scale [0 (<20% coverage)-4 (>80% coverage)]. For stubborn deposits (mascara), NR failed to remove deposits from 94% of lenses, whilst R removed more than 80% of deposits from 63% of the lenses. For oily deposits, 25% of NR lenses had >80% coverage, whilst only one R lens had 60-80% coverage, with 19% having 40-60% coverage, and 38% with either 20-40% or <20%. Rubbing improved lens cleanliness for both types of deposits, but only reached statistical significance for the stubborn deposit group. There were no significant differences between the solutions. Not Rubbing and using either HP or PI solutions, is not effective in removing stubborn deposits from ortho-k lenses. It is essential to rub lenses when cleaning rigid lenses to ensure optimal lens hygiene for ocular health, especially as rigid gas permeable (RGP) lenses are intended to be reused for at least a year before replacement. Rubbing with a daily cleaner should be included in the instructions for use of the solutions tested for rigid lenses and practitioners should be encouraged to emphasise the importance of rubbing in lens care.

Experience in application of hybrid contact lenses for astigmatism correction

The review covers the issue of hybrid contact lenses application as one of the modern contact correction methods in patients with ametropias of various genesis. Hybrid contact lenses consist of a rigid central optical part made of highly gas-permeable material and a flexible peripheral part made of hydrophilic material. These lenses combine the optical correction qualities of gas-permeable corneal lenses with the comfort and stable fit usually provided by soft contact lenses. Compared to gas-permeable corneal lenses, hybrid lenses are more comfortable; often have better centration and more stable fit on the eye. Hybrid contact lenses successfully correct both types of astigmatism: regular and irregular. This type of lenses is a good alternative method of contact correction for patients who place heavy demands in terms of the quality of vision.

OKVision® Onefit™ Mini-Scleral Lenses Fitting Guide

Corneal topography has been widely used in medical practice over recent years and it has helped to detect keratectasias of various genesis more often and in the earlier stages. The emergence of the new polymer materials with high oxygen permeability made it possible to wear scleral contact lenses safely, that also resulted in their popularization. Scleral gas permeable lenses are an effective method of vision correction not only for various ectasias, but also for ametropia, presbyopia and other refractive pathologies. Scleral contact lenses do not directly touch the cornea and the limbus area, whereas tear firm under the lens physically smoothes out all of the existing defects and irregularities of the corneal surface, thus creating a ”cornea-tear-lens“ unified optical system. As a result, visual acuity increases significantly. In addition, scleral lenses ensure excellent comfort starting from the first minutes of wearing due to a larger diameter, no direct contact with the cornea and relatively low mobility. Scleral lenses ensure high visual functions and comfort owing to their specific self-supporting design, which is rested on the sclera. Selection and fitting of scleral contact lenses is simple and can be mastered by any ophthalmologist

Performance of Rigid Gas Permeable (RGP) Scleral Contact Lenses With a Passive Artificial Iris

Performance of Rigid Gas Permeable (RGP) Scleral Contact Lenses With a Passive Artificial Iris