BCLA CLEAR - Orthokeratology

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

BCLA CLEAR - Scleral lenses

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

BCLA CLEAR - Effect of contact lens materials and designs on the anatomy and physiology of the eye

This paper outlines changes to the ocular surface caused by contact lenses and their degree of clinical significance. Substantial research and development to improve oxygen permeability of rigid and soft contact lenses has meant that in many countries the issues caused by hypoxia to the ocular surface have largely been negated. The ability of contact lenses to change the axial growth characteristics of the globe is being utilised to help reduce the myopia pandemic and several studies and meta-analyses have shown that wearing orthokeratology lenses or soft multifocal contact lenses can reduce axial length growth (and hence myopia).However, effects on blinking, ptosis, the function of Meibomian glands, fluorescein and lissamine green staining of the conjunctiva and cornea, production of lid-parallel conjunctival folds and lid wiper epitheliopathy have received less research attention. Contact lens wear produces a subclinical inflammatory response manifested by increases in the number of dendritiform cells in the conjunctiva, cornea and limbus. Papillary conjunctivitis is also a complication of all types of contact lenses. Changes to wear schedule (daily disposable from overnight wear) or lens materials (hydrogel from SiHy) can reduce papillary conjunctivitis, but the effect of such changes on dendritic cell migration needs further study. These changes may be associated with decreased comfort but confirmatory studies are needed. Contact lenses can affect the sensitivity of the ocular surface to mechanical stimulation, but whether these changes affect comfort requires further investigation.In conclusion, there have been changes to lens materials, design and wear schedules over the past 20+ years that have improved their safety and seen the development of lenses that can reduce the myopia development. However, several changes to the ocular surface still occur and warrant further research effort in order to optimise the lens wearing experience.     

BCLA CLEAR – Contact lens technologies of the future

Contact lenses in the future will likely have functions other than correction of refractive error. Lenses designed to control the development of myopia are already commercially available. Contact lenses as drug delivery devices and powered through advancements in nanotechnology will open up further opportunities for unique uses of contact lenses.This review examines the use, or potential use, of contact lenses aside from their role to correct refractive error. Contact lenses can be used to detect systemic and ocular surface diseases, treat and manage various ocular conditions and as devices that can correct presbyopia, control the development of myopia or be used for augmented vision. There is also discussion of new developments in contact lens packaging and storage cases.The use of contact lenses as devices to detect systemic disease has mostly focussed on detecting changes to glucose levels in tears for monitoring diabetic control. Glucose can be detected using changes in colour, fluorescence or generation of electric signals by embedded sensors such as boronic acid, concanavalin A or glucose oxidase. Contact lenses that have gained regulatory approval can measure changes in intraocular pressure to monitor glaucoma by measuring small changes in corneal shape. Challenges include integrating sensors into contact lenses and detecting the signals generated. Various techniques are used to optimise uptake and release of the drugs to the ocular surface to treat diseases such as dry eye, glaucoma, infection and allergy. Contact lenses that either mechanically or electronically change their shape are being investigated for the management of presbyopia. Contact lenses that slow the development of myopia are based upon incorporating concentric rings of plus power, peripheral optical zone(s) with add power or non-monotonic variations in power. Various forms of these lenses have shown a reduction in myopia in clinical trials and are available in various markets.     

BCLA CLEAR - Evidence-based contact lens practice

Evidence-based contact lens practice involves finding, appraising and applying research findings as the basis for patient management decisions. These decisions should be informed by the strength of the research study designs that address the question, as well as by the experience of the practitioner and the preferences and environment of the patient. This reports reviews and summarises the published research evidence that is available to inform soft and rigid contact lens history and symptoms taking, anterior eye health examination (including the optimised use of ophthalmic dyes, grading scales, imaging techniques and lid eversion), considerations for contact lens selection (including the ocular surface measurements required to select the most appropriate lens parameter, lens modality and material selection), evaluation of lens fit, prescribing (teaching self-application and removal, adaptation, care regimen and cleaning instructions, as well as minimising risks of lens wear through encouraging compliance) and an aftercare routine.     

BCLA CLEAR - Anatomy and physiology of the anterior eye

A key element of contact lens practice involves clinical evaluation of anterior eye health, including the cornea and limbus, conjunctiva and sclera, eyelids and eyelashes, lacrimal system and tear film. This report reviews the fundamental anatomy and physiology of these structures, including the vascular supply, venous drainage, lymphatic drainage, sensory innervation, physiology and function. This is the foundation for considering the potential interactions with, and effects of, contact lens wear on the anterior eye. This information is not consistently published as academic research and this report provides a synthesis from all available sources. With respect to terminology, the report aims to promote the consistent use of nomenclature in the field, and generally adopts anatomical terms recommended by the Federative Committee for Anatomical Terminology. Techniques for the examination of the ocular surface are also discussed.     

Italian translation and validation of the Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8)

PurposeTo translate and validate an Italian version of the CLDEQ-8 (CLDEQ-8_IT).MethodsThe study was carried out in two phases. In the first phase, a cross-cultural adaptation of CLDEQ-8 to Italian was performed by forward and backward translation in sequence. In the second phase, a multi-centre study was conducted for the validation of the questionnaire. Validity CLDEQ-8_IT was evaluated against three gestalt questions: overall opinion of soft contact lenses (CLs), global self-assessments of eye sensitivity and eye dryness. Reliability was evaluated by test–retest assessment in a subgroup of subjects. Finally, the psychometric properties of CLDEQ-8_IT were explored by Rasch analysis.ResultsTwo hundred and forty soft CL wearers, fluent Italian speakers (73 males and 167 females), between 18 and 70 years of age were enrolled. A significant correlation was found between CLDEQ-8_IT and each of the three Gestalt questions. The cutoff score of 12 points demonstrated the best balance between sensitivity and specificity in differentiating wearers grading their CLs as “Excellent/Very good” from those reporting their overall opinion as “Good/Fair/Poor”. The Intraclass Correlation Coefficient between test and retest was 0.88 (95% CI: 0.81–0.92). Finally, infit and outfit statistics using Rasch analysis for the 8 items were in a good range, however Principal Components Analysis revealed a certain degree of multi-dimensionality of the instrument. Also, item 8 analysis could be computed after merging the last two response categories.ConclusionThe CLDEQ-8_IT showed very good validity and reliability in measuring symptoms of CL wearers, comparable to the original English language version. A cut-off of 12 was confirmed as yielding the best balance between sensitivity and specificity in detecting CL wearers who could benefit from clinical management of their CL-related symptoms. Collapsing of the response options 5 and 6 in the last item of questionnaire could optimise its functioning.     

The ability of the Contact Lens Dry Eye Questionnaire (CLDEQ)-8 to detect ocular surface alterations in contact lens wearers

PurposeTo study whether some ocular surface alterations could be associated with contact lens (CL) wearers suffering from CL discomfort (CLD) detected using the Contact Lens Dry Eye Questionnaire (CLDEQ)-8.MethodsForty-one soft CL wearers further classified into symptomatic CL wearers (SCLW) and asymptomatic CL wearers (ACLW) by the CLDEQ-8, and 20 non CL wearers (NCLW) were included. Tear osmolarity, slit-lamp biomicroscopy findings, tear film break-up time, corneal and conjunctival staining, and Schirmer test were performed 24 h after CL removal. Data were compared among groups using the analysis of variance and the Student t-test or the Kruskal-Wallis H and the Mann-Whitney U tests, applying the Bonferroni correction. Correlations between the CLDEQ-8 and the clinical signs were performed using the Spearman correlation coefficient.ResultsTwenty-four SCLW, 17 ACLW and 20 NCLW were recruited. There were significant differences among groups for tear osmolarity (p < 0.001), limbal hyperaemia (p = 0.014), and tarsal hyperaemia (p = 0.031). Pairwise comparisons revealed that SCLW and ACLW had higher tear osmolarity (p < 0.003, both comparisons) and limbal hyperaemia (p = 0.027 and p = 0.048, respectively) than NCLW. Moreover, SCLW had higher tarsal hyperaemia (p = 0.030) than NCLW. No significant correlations were found (p > 0.05).ConclusionThe CLDEQ-8 was ineffective to detect clinical alterations between SCLW and ACLW; therefore, the use of questionnaires alone remains being the best approach to detect CLD. The role of the tarsal conjunctiva in the development of CLD should be analyzed in future studies.     

Machine learning based strategy surpasses the traditional method for selecting the first trial Lens parameters for corneal refractive therapy in Chinese adolescents with myopia

PurposeReturn zone depth (RZD) and landing zone angle (LZA) are important parameters of corneal refractive therapy (CRT) lenses. A new machine learning algorithm is proposed for prescribing CRT lens parameters in Chinese adolescents with myopia.MethodsThis is a retrospective study. In total, 1037 Chinese adolescents with myopia (1037 right eyes) were enrolled. A calculation model based on corneal elevation maps was constructed to calculate RZD and LZA for the four quadrants. Furthermore, multiple linear regression and optimized machine learning models were established to predict RZD and LZA values for different combinations of age, sex, and ocular parameters. The four methods (sliding card, linear regression, calculation and optimized machine learning) were then compared to the parameters of the final ordered lens.ResultsThe optimized machine learning pipeline achieved the best performance. Age, sex, horizontal visible iris diameter (HVID), spherical equivalent refraction degree (SER), eccentricity (e), keratometric (K) readings, corneal astigmatism (CA), axial length (AL), AL/corneal curvature ratio (AL/MK), and anterior chamber depth (ACD) were significant to the machine learning model. The R values for the nasal, temporal, superior and inferior LZA based on machine learning were 0.843, 0.693, 0.866 and 0.762, respectively, and those for the RZD were 0.970, 0.964, 0.975 and 0.964, respectively.ConclusionsThe feasibility and efficiency of an optimized machine learning method to predict LZA and RZD parameters has been demonstrated. The advantage of the proposed method is that it is more accurate, easier to use and faster to implement than the traditional sliding card method.     

Uptake and release of polyhexamethylene biguanide (PHMB) from hydrogel and silicone hydrogel contact lenses using a radiolabel methodology

PurposeThe purpose of this study was to evaluate the uptake and release of radiolabelled polyhexamethylene biguanide (PHMB) on reusable daily wear contact lenses (CLs) over 7 days.MethodsThree silicone hydrogel (SH) contact lens materials (lotrafilcon B, balafilcon A, senofilcon A) and two conventional hydrogel (CH) materials (etafilcon A, omafilcon A) were examined. In experiment 1 (1-day study), CLs were soaked in 2 mL of phosphate buffered solution (PBS) containing radiolabelled ¹⁴C PHMB (1 µg/mL) for 8 h. The release kinetics of ¹⁴C PHMB from the CLs was measured at t = 0.25, 0.5, 1, 2, 4, 8, and 24 h in fresh 2 mL PBS. In experiment 2 (7-day study), the CLs were soaked in the ¹⁴C PHMB (1 µg/mL) solution for 8 h followed by a 16-hour release in 2 mL PBS. The lens cycle was repeated daily for 7 days. After both experiments, the residual amount of PHMB remaining within the lenses was extracted to determine the total uptake of PHMB.ResultsIn experiment 1, the total uptake of PHMB for etafilcon A was significantly greater than senofilcon A (p = 0.01). There were no significant differences in total uptake of PHMB between other lens materials (p > 0.05). Etafilcon A released more PHMB compared to all other lens types over a 24-hr period (p < 0.001). In experiment 2, all CL materials continued to sorb more PHMB over time (p < 0.001). By day 7, the amount of PHMB sorbed by etafilcon A was significantly greater than senofilcon A (p = 0.02). After day 2, the CH materials released significantly more PHMB than the SH materials (p < 0.01).ConclusionThe CL materials continued to sorb PHMB with no signs of saturation after 7 days. All lens materials released a consistent amount of PHMB each day. Radioactive labelling provides a sensitive method of assessing the uptake and release of PHMB from CL materials.     

Effect of large diameter and plasma coating on the initial adaptation of gas permeable contact lens fitting for neophytes

PurposeTo determine whether the adaption of neophytes to rigid gas permeable lenses (GPs) could be accelerated by changing their diameter or surface lubricity.MethodsThis was a 2 part prospective double-masked randomised wear study. An GP lens (Roflufocon D material, 9.6 mm diameter) with and without a Hydrapeg plasma coating surface was worn by 119 neophytes (21.1 ± 3.5 years; 77% female) on separate occasions. A further 114 neophytes (average age 20.1 ± 1.0 years; 72% female) wore the uncoated lens with a 9.6 mm diameter lens in one randomly allocated eye and 10.1 mm (n = 51) or 10.6 mm (n = 63) in the other with a basecurve compensation keeping the fit equivalent. Lens fit and corneal staining was assessed after 20 min, and comfort and bulbar redness were assessed at the time of lens application and after 5, 10, 15, and 20 min. Participants also reported their ease of application and removal on a 5 point scale.ResultsPlasma coated GP lenses or increasing diameter did not improve comfort (p = 0.673, p > 0.05) or bulbar redness (p = 0.805, p > 0.05) during a 20 min adaptation period in neophytes. In both cohorts, comfort improved and bulbar redness reduced with time (p < 0.001). Corneal staining, ease of insertion application and ease of removal did not differ with GP coating application or GP diameter (p > 0.05).ConclusionChanging GP diameter or surface lubricity is not beneficial to the adaption of healthy neophytes     

Validation and reliability of the Turkish version of Contact Lens Dry Eye Questionnaire-8 (CLDEQ-8)

PurposeContact lens dry eye questionnaire-8 (CLDEQ-8) quantifies the disturbing symptoms with the aim of assessing the satisfaction and overall opinion of contact lens wearers. The aim of this study was to develop Turkish version and to evaluate the validity and reliability of the questionnaire.MethodsCLDEQ-8 was translated into Turkish language, using the back translation methods. In a sample of 10 individuals, validation of translation was checked as pre-test evaluation. Turkish version of CLDEQ-8 questionnaire was conducted in 100 soft contact lens wearers. Validity was investigated using Rasch analysis and reliability by Cronbach’s alpha (α) and person separation index (PSI).ResultsThe participants were healthy other than refractive errors. Their mean age was 25.19 ± 7.03 years and male to female ratio was 14/86. All of them were silicone-hydrogel soft contact lens wearers. Their contact lens history was 3.13 ± 3.77 years and mean refraction error was -2.69 ± 1.64 diopters.The whole 8 items were consistent with the Rasch model (p > 0.05) and unidimensional (paired t test, p = 0.1). Both Cronbach’s alpha and PSI values were higher than 0.7 (α = 0.873, PSI = 0.867). There were not functional differences in questionnaire items regarding overall age groups (Andersen LR test, p = 0.518).ConclusionTurkish version of the CLDEQ-8 conforms to the Rasch model and provides the one dimensional assumption. The questionnaire has internal consistency, is valid and reliable in Turkish contact lens wearers.     

Ocular microbiota and lens contamination following Mel4 peptide-coated antimicrobial contact lens (MACL) extended wear

PurposeThe purpose of this study was to investigate the effect of Mel4 antimicrobial peptide-coated contact lenses (MACL) on the microbiota of the conjunctiva and lenses during three months of extended wear.MethodsOne hundred and seventy-six participants were recruited into a randomised, contralateral, double masked, biweekly extended wear MACL and uncoated control lens trial. At the one month and 3-month visit, the conjunctival microbiota was sampled using sterile cotton swabs and contact lenses were collected aseptically. Standard microbiological procedures were employed for culture of the swabs and contact lenses and identification of the isolated microorganisms.ResultsGram-positive bacteria (predominantly coagulase-negative staphylococci) were the most frequently isolated microbes from both contact lenses and conjunctiva. There was no difference in the frequency of isolation of most bacteria or fungi from the conjunctival swabs of eyes wearing either MACL or control lenses. The only exception was a higher frequency of eyes harbouring Staphylococcus arlettae when wearing control lenses (5%) versus MACL (<1%) (p = 0.002). There was no significant difference in the frequency of microbes isolated from MACL or control contact lenses. There were also no differences between lens types in the frequency of isolation of >1 microbial type per sampling occasion for either conjunctiva swabs or contact lenses.ConclusionMACL wear did not change the conjunctival microbiota during extended wear, and the types of microbes isolated from MACL were similar to those isolated from control lenses.     

食品接触硅橡胶制品中5 种高关注物质的分析

建立超声辅助溶剂萃取（ultrasound-assisted solvent extraction,UASE）-气相色谱-串联质谱（gas chromatography-tandem mass spectrometry,GC-MS/MS）法和固相微萃取（solid phase micro-extraction,SPME）-GC-MS/MS法对食品接触硅胶制品中N-甲基苯胺（N-methylaniline,NMA）、N,N-二甲基苯胺（N,N-dimethylphylamine,DMA）、壬醛、2,6-二叔丁基对甲苯酚（butylated hydroxytoluene,BHT）及苯并噻唑（benzothiazole,BTZ）5 种高关注物质（substances of very high concern,SVHC）的检测方法。优化并评价2 种方法,结果显示UASE-GC-MS/MS方法更加简单、高效,线性范围更宽,有良好的回收率和精密度,满足测定要求。利用UASE-GC-MS/MS法对29?种奶嘴和27?种模具中的5?种SVHC进行定量分析,结果显示奶嘴中壬醛含量最高,为1?439.85?ng/g;模具中BHT含量最高,为4?828.78?ng/g;NMA和DMA均被检出。通过对5?种物质在奶嘴和模具两类制品中的含量及差异性分析、毒性、来源、限量要求等对其在食品接触硅胶制品中的安全性进行评价。NMA和DMA在模具中的含量高于奶嘴,可能是由于模具中的有机染料等助剂所致,且根据法规要求,它们的检出对人体存在健康风险,应引起高度关注,有必要通过改进配方或工艺来控制苯胺类物质的生成。壬醛在奶嘴和模具中无显著性差异,尽管有较高的检出率,仍然可以认为食品接触硅胶制品中的壬醛含量在安全范围以内。BTZ和BHT有必要进行进一步的迁移实验研究和暴露评估。     

Allergenic responses of red kidney bean (Phaseolus vulgaris cv chitra) polypeptides in BALB/c mice recognized by bronchial asthma and allergic rhinitis patients

Allergenicity potential of red kidney beans (Phaseolus vulgaris cv chitra) was assessed and attempts were made to identify the responsible proteins by pepsin digestibility assay and IgE immunoblotting. To evaluate allergenic potential, BALB/c mice were sensitized with red kidney bean proteins and levels of specific immunoglobulin, histamine, mast cell protease-1, cytokines and CCL-2 were measured. To confirm our findings in BALB/c, the studies were also extended to human subjects. Human sera collected from control subjects and allergic patients after skin prick test were used for IgE immunoblotting, measuring the levels of total and specific IgE and determining cross reactivity of red kidney bean with other legumes. Red kidney bean allergenic potential was evident by significant increase in specific IgE, IgG1, histamine, mast cell protease-1 and Th2 cytokine levels in comparison to control. Enhanced level of eosinophils in jejunum, prominent anaphylactic symptoms, and eruptive histopathological changes give indication towards red kidney beans allergenicity. IgE immunoblotting detected five protein components with molecular weights of approximately 170, 100, 43, 34 and 20 kDa. Red kidney bean proteins showed cross reactivity with peanut, soybean, chickpea and black gram. Finally, this work demonstrated that red kidney beans may induce allergic response in mice similar to human subjects, with identification of five clinically relevant allergenic protein components.