Silicone hydrogel daily disposable benefits: The evidence

Daily disposable (DD) contact lenses first came to the market approximately 25 years ago and eye care professionals (ECPs) started prescribing silicone hydrogel (SiH) contact lenses, primarily for extended or continuous wear, approximately 20 years ago. It has now been over ten years since SiH DD contact lenses have been available, and while SiH materials are routinely prescribed by ECPs for reusable daily wear, hydrogel materials are still frequently selected for the DD modality of contact lens wear. This article reviews the evidence to support the benefits of both a DD modality and SiH materials and how patients' needs may be met with SiH DD contact lenses, with respect to clinical performance, health outcomes, satisfaction, compliance and convenience. Factors which may enable or constrain ECPs from prescribing SiH DD contact lenses, as opposed to hydrogel DD and reusable contact lenses, for more of their patients are discussed with the objective of providing ECPs with a greater understanding of the advantages that can be afforded by prescribing SiH DD contact lenses to both their new and existing contact lens wearers.

Evaluation of the influence of social, demographic, environmental, work-related factors and/or lifestyle habits on Raynaud's phenomenon: a case-control study

Raynaud's phenomenon (RP) is a clinical disorder characterized by recurrent, reversible episodes of digital vasospasm. RP can be classified as primary (pRP) or secondary, depending on whether it occurs as a benign condition (not disease-associated) or is associated with other diseases, mainly of the connective tissues. In both cases, it can be triggered by environmental factors, as indicated by the increased incidence of pRP episodes following exposure to cold, vibration injury or chemicals. The purpose of this prospective case-control study was to assess, in an Italian cohort of 132 pRP patients, the association of the phenomenon with demographic, lifestyle habits, environmental and work-related factors. Compared to healthy controls, pRP was found to be inversely associated with the use of contact lenses (OR = 0.4; p = 0.004) and of chlorous-based disinfectants (OR = 0.3; p < 0.001) and directly associated with the presence of prosthesis implants (OR = 5.3; p = 0.001) and the use of hydrogen peroxide-based compounds (OR = 2.6; p = 0.002), suggesting that the latter should be avoided in RP affected patients. Multivariate and multivariable analysis confirmed the associations. Further investigations are needed to understand the mechanism(s) underlying these findings.

Peripheral refraction and spherical aberration profiles with single vision, bifocal and multifocal soft contact lenses

PURPOSE

To compare the peripheral refraction and spherical aberration profiles along three visual field meridians of 16 commercial single vision (SV), bifocal (BF) and multifocal (MF) test contact lenses with a single vision control.

METHOD

Forty-four participants [24.2±2.4 years, SE: -0.50 to -4.50D] were randomly fitted, contra-laterally, with 6 SV's [Air Optix Aqua (control), Acuvue Oasys, Biofinity, Clariti, Night & Day and Proclear], 3 BF's [Acuvue Bifocal low and high add, MiSight] and 8 MF's [Proclear D & N in 1.5 and 2.5D adds; AirOptix, PureVision low & high adds]. Peripheral refraction was performed across horizontal, oblique and vertical meridians, with lenses on eye using the BHVI-EyeMapper. The power vectors M, J₀, J₄₅ and the spherical aberration coefficient were analysed. The peripheral refraction and aberration profiles of the test lenses were compared with the profiles of the control lens using curvature and slope coefficients.

RESULTS

Compared to the control, a relative peripheral hyperopic shift (M), a less negative J₀ curvature coefficient along the horizontal meridian, a less positive J₀ curvature coefficient along the vertical meridian, a less negative J₄₅ curvature coefficient along the oblique meridian and a more positive spherical aberration curvature coefficient along most meridians was seen with the Acuvue Bifocal and all center-near multifocal lenses. For the center-distance multifocal lenses the direction of the curvature coefficients of the same refraction and aberration components was opposite to that of the center-near lenses. The greatest differences in the slope coefficients when compared to the control were found for the Acuvue Bifocal lenses and all multifocal contact lenses for the refractive component M and the spherical aberration coefficient along the horizontal visual field meridian, with the Acuvue Bifocal and the center-near multifocal lenses having more positive coefficients and the center-distance lenses having more negative coefficients.

CONCLUSION

When worn on eye, different commercially available lens types produce differences in the direction and magnitude of the peripheral refraction and spherical aberration profiles along different visual field meridians. This information may be relevant to refractive development and myopia control.

Stability of peripheral refraction changes in orthokeratology for myopia

PURPOSE

Orthokeratology (OK) is known to alter relative peripheral refraction (RPR) with this presumed to be its key myopia control mechanism. A prospective, longitudinal study was performed to examine stability of OK-induced RPR changes in myopic children and young adults.

METHODS

RPR of twelve children (C)(8-16 years) and eight adults (A)(18-29 years) with spherical equivalent refraction of -0.75 to -5.00D were measured unaided and while wearing single vision soft contact lenses (SCL). Measurements were repeated after 1, 6 and 12 months of OK wear. RPR was measured using an open-field Shin Nippon SRW-5000 autorefractor at 10, 20 and 30 degrees nasally (N) and temporally (T), converted into power vectors M, J0 and J45. On-axis refractions and axial lengths (IOL Master) were also measured.

RESULTS

Compared to the unaided state, 1-month of OK wear shifted the RPR in the myopic direction at 30 T (C: p = 0.023; A:, p = 0.002) and 30 N (C&A, p = 0.003) and was stable thereafter, with similar changes compared to SCL wear. J0 showed a myopic shift in comparison to both unaided and SCL correction in children but not adults, and J45 did not change in either group. The on-axis OK correction was predictive of the RPR shift in both children and adults at 30 T (C: r=-0.58, p = 0.029; A: r=-0.92, p < 0.001) and 30 N (C: r=-0.60, p = 0.024; A: r=-0.74, p = 0.013) with symmetry of RPR shifts (C: r = 0.67, p = 0.008; A: r = 0.85, p = 0.004). No relationships between changes in RPR and axial length were found after twelve months of OK wear; level of myopia was stable in both groups.

CONCLUSION

Relative to both unaided and single vision SCL correction, OK shifted the RPR in the myopic direction; the RPR was stable from 1 to 12 months. The RPR shift in OK wear varied with the degree of myopia but was not correlated with myopia progression.

Childhood and lifetime risk comparison of myopia control with contact lenses

PURPOSE

The relative risks of ocular pathology with increasing myopia have been described; the absolute lifetime risk of vision impairment from myopia is yet to be compared to the childhood and lifetime risks of contact lens wear for myopia control.

METHODS

Using peer-reviewed data, the absolute risks of microbial keratitis (MK) in daily disposable soft, reusable soft and orthokeratology contact lens (CL) wear were calculated over both a childhood (age 8-18) and a lifetime (age 8-65) of CL wear. This was compared to the previously published cumulative risk of vision impairment by age 75 based on increasing myopia and axial length. Data were converted utilizing the Council of International Organizations of Medical Sciences (CIOMS) classification system for frequency of adverse events, with 95 % confidence intervals included.

RESULTS

The lifetime risk of vision impairment in axial lengths over 26 mm and more than 6D of myopia is greater than the lifetime risk of MK in any CL modality, except for adult SCL extended wear. If axial length is below 26 mm and myopia lower than 3D, a lifetime of CL wear is more risky in comparison, except in the case of daily disposable wear. Ten years of childhood CL wear of any modality presents lower likelihood of MK than any comparable risk of vision impairment.

CONCLUSION

The comparative lifetime risks of contact lens wear commenced at age 8 for myopia control are less than the lifetime risks of vision impairment with myopia more than 6D or axial length more than 26 mm. When only childhood CL wear is considered, the risk comparison is clearly skewed towards the positive impact of CL wear, especially in daily disposable wear. Clinicians should be confident to proactively recommend myopia control CL wear to younger children, as both the safety profile and potential preventative ocular health benefits are evident.

Zeta potential of tear samples: A tool to explore the effects of wear of contact lenses

PURPOSE

The aim was to develop a method to assess the electrostatic properties of human tear samples, and to evaluate their modifications induced by the wear of contact lenses (CLs).

METHOD

The barrier method was developed for the measurement of the isoelectric point (IEP) on relatively small quantities. The method was applied to compare three groups: tears (T_NW) of non-wearers, tears (T_{W_etaf}) of regular wearers of etafilcon A CLs, and tears (T_{W_omaf}) of regular wearers of omafilcon A CLs. Zeta potential (ζ) as a function of pH was measured by a Zetasizer Nano ZS90 (Malvern Instruments) on 40%-diluted samples, obtained by mixing 57 μL of tears of different subjects of the same group with 85 μL of HCl aqueous solution. IEP was deduced as the pH at which ζ is zero, i.e. the net electric charge on tear constituents being neutralized.

RESULTS

Within an error of about 0.05, IEPs were found to be 2.90 (T_NW), 2.80 (T_{W_omaf}), and 3.16 (T_{W_etaf}). On average, a lower H⁺ concentration is needed to neutralize the surface charge of the tear components of etafilcon A wearers, compared to both T_NW and T_{W_omaf}.

CONCLUSION

IEP measurements on tear samples of wearers of different types of CLs are proposed in order to enhance the knowledge on the modifications of the profile of charged species in tears. The T_{W_etaf} results, compared to those of the other groups, are compatible with an increase, due to the wear of etafilcon A CLs, of the relative concentration of high-IEP proteins.

Presbyopia and the aging eye: Existing refractive approaches and their potential impact on dry eye signs and symptoms

Every part of the human body is subject to aging, including the eye. An increased prevalence of dry eye disease with age is widely acknowledged. Aging threatens ocular surface homeostasis, altering the normal functioning of the lacrimal functional unit and potentially leading to signs and symptoms of dry eye. Additional age-related processes take place within the crystalline lens, leading to presbyopia and cataractogenesis. Correction strategies for presbyopia and cataracts may directly or indirectly challenge the ocular surface. Contact lenses disturb the normal structure of the tear film and can interact negatively with the ocular surface, further deteriorating an already unbalanced tear film in presbyopes, however, newer contact lens designs can overcome some of these issues. Moreover, cataract and corneal refractive surgeries sever corneal nerves and disrupt the corneal epithelium and ocular surface, which can influence surgical outcomes and aggravate dryness symptoms in older age groups. This review summarises the current understanding of how the invasive nature of contact lens wear and cataract and refractive surgery influence signs and symptoms of ocular dryness in an aging population.

Contact lenses as drug-delivery systems: a promising therapeutic tool

The ocular administration of drugs using traditional pharmaceutical forms, including eye drops or ointments, results in low bioavailability, as well as requiring multiple administrations per day, with the consequent danger of therapeutic non-compliance. Although, through the use of pharmaceutical technology, attempts have been made to use various solutions in order to increase bioavailability in the most common pharmaceutical forms, it has not been entirely satisfactory. In this context, contact lenses are presented as drug delivery systems that largely remedy these two major problems and offer other additional advantages. Therefore, the use of contact lenses as drug carrying systems has been increasingly investigated in recent years, as they can increase the bioavailability of these drugs, leading to an increase in therapeutic efficacy and compliance. The main techniques used to achieve this goal are included in this review, including immersion in drug solutions, use of vitamin E barriers, molecular printing, colloidal systems, etc. The most interesting results, depending on the different eye pathologies, are presented. Although the use of contact lenses as a vehicle for the release of active ingredients is a relatively novel strategy, there are already many studies and trials that support it. In any case, further research needs to be carried out to finally reach an effective, safe, and stable product that can be marketed.

The Epidemiology and Clinical Features of Blepharoptosis in Taiwanese Population

BACKGROUND

Blepharoptosis describes a condition of low-lying upper eyelid that may affect individuals of all ages under various etiologies. It may be of congenital or acquired form by the timing of onset or be divided into myogenic, neurogenic, aponeurotic, or mechanical types according to the mechanism. Our goal was to report the characteristics of age-specific blepharoptosis and to analyze the association between levator function (LF) and ptosis severity of each ptosis subtype.

MATERIALS AND METHODS

The retrospective, single-center, cross-sectional study consisted of patients diagnosed with blepharoptosis in the plastic surgery practice at a medical center between September 2009 and May 2017. We reported patients' age at presentation, sex, laterality of ptosis, etiology, classification, and evaluation of ptosis including levator function and ptosis severity.

RESULTS

During a nine-year span of study, a total of 1975 eyelids of 1164 Taiwanese patients aged between 2 and 88 years were enrolled in the research (mean = 57.73 ± 13.41 years). The female-to-male ratio was 2.72 (95% confidence interval [CI]: p < 0.0001). Acquired blepharoptosis and bilateral blepharoptosis were more frequently observed (55.85%, p < 0.0001 and 69.67%, p < 0.0001, respectively). In age-specific relative incidence of blepharoptosis, myogenic ptosis was the majority in patients younger than 40 years. Early onset of aponeurotic ptosis was observed in young contact lenses wearers. Aponeurotic blepharoptosis was the predominant type of ptosis in the senior population older than 40 years (p < 0.0001). Among the subtypes, mechanical ptosis had the most preserved LF (p < 0.0001). LF and MRD1 had statistically positive correlations in all subtypes of blepharoptosis, in which neurogenic ptosis demonstrated the severest levator dysfunction for each millimeter in MRD1 reduction.

CONCLUSIONS

Of the 1164 Taiwanese patients, blepharoptosis had a higher propensity for female gender and the age between the second to fourth decades. Bilateral involvement of blepharoptosis with acquired type was frequently diagnosed. Myogenic ptosis had a preponderance in age younger than 40 years, while aponeurotic ptosis usually affects senile population. Many mild degree myogenic ptosis was simultaneously recognized in young-aged adults seeking aesthetic double eyelid surgery. Early onset of acquired aponeurotic ptosis was also observed in contact lens wearers given the trend of decorative contact lens use. Levator dysfunction was implicated in the pathology of not only myogenic ptosis but aponeurotic, mechanical, and neurogenic ptosis. Moreover, levator function of neurogenic ptosis was most severely impacted in each MRD₁ reduction among all subtypes of blepharoptosis.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

International survey of contact lens fitting for myopia control in children

PURPOSE

To determine the extent of contact lens fitting for myopia control (MC) in children (defined as ≤ 17 years of age) worldwide and to characterize the associated demographics and fitting patterns.

METHODS

Survey forms were sent to contact lens fitters in 66 countries between January and March every year for eight consecutive years (2011-2018, inclusive). Practitioners were asked to record data relating to the first 10 contact lens fits performed after receiving the survey form. Data were analysed for those countries reporting ≥ 100 contact lens fits to children.

RESULTS

Data were analysed for 535 MC fits and 23,295 other (non-MC) lens fits undertaken in 31 countries reporting ≥ 100 contact lens fits to children, with 52.1% of MC fits and 12.0% of non-MC fits being with rigid lenses (p < 0.0001). Overall, MC lenses represented 2.3% of all contact lens fits to children, with significant differences between nations (p < 0.0001), ranging from no MC fits recorded in the Czech Republic, Greece, Japan, South Korea and Puerto Rico, to 24.9% in Austria. There has been an increase in contact lens fitting for MC over the survey period (p < 0.0001). MC contact lenses were fitted to younger children compared to non-MC lenses (MC, median 13 years vs. non-MC, median 15 years) (p < 0.0001). There was no sex bias in the fitting of MC lenses (p = 0.89).

CONCLUSIONS

MC lenses are currently being prescribed for younger children in equal measure in terms of soft vs. rigid lenses and males vs. females. The extent of MC fitting is low and varies between nations. The gradual increase in MC fitting throughout the survey period perhaps reflects growing concerns among practitioners over the myopia epidemic.

[Standardizing the clinical diagnosis and treatment of keratoconus in China]

Keratoconus, which can lead to blindness, is an eye disease characterized by thinning and protrusion of the cornea. Keratoconus often begins during teenage with an incidence rate of about 1∶2 000. As no consensus on the diagnosis and treatment of keratoconus has never been reached in China, many doctors have not acquired a systemic knowledge of the diagnosis and treatment methods, thus various misunderstandings and problems in the clinical diagnosis and treatment of keratoconus still need our attention. By explaining the necessity and principles in the diagnosis and treatment of keratoconus, this article points out that clinicians should make efforts to comprehensively master the methods of clinical diagnosis and treatment of keratoconus and then provide patients with the most suitable treatment according to their different conditions, which are of great importance for the patients to maintain better visual acuity and quality of life for a long period. (Chin J Ophthalmol, 2019, 55: 401-404).

[The changes in corneal transparency after orthokeratology with juvenile myopia]

Objective: To evaluate the changes of corneal transparency undergoing overnight orthokeratology treatment. Methods: Prospective cohort study. Right eyes of juvenile myopic patients fitted with Ortho-K CL at Qingdao Eye Hospital were enrolled. Corneal optical density values were measured by the Pentacam Scheimpflug system before orthokeratology and at 1 day, 1 week, and 1, 3, 6, and 12 months after wearing. Four concentric radial zones centered on the apex of the cornea (≤2 mm, >2 mm and ≤6 mm, >6 mm and ≤10 mm, and>10 mm and ≤12 mm diameter) were applied. Anterior layer (anterior 120 μm), central layer, and posterior layer (posterior 60 μm) were defined according to corneal depth. The data analysis were used One-Way Repeated Measures ANOVA and LSD test. Results: Forty patients (40 eyes) with myopia (24 male and 16 female, age 10.76±1.74 years) were in enrolled. Corneal optical density value was 13.18±0.23 before orthokeratology, then showed a decreasing trend at the early stage, but there was no statistical difference (within 3months: t=-1.594, -1.472, 0.064, 1.971; P>0.05). The value increased significantly and reached the peak (15.31±0.23, t=7.613, P<0.01) at 6-month, and was still maintained in a high value at 1-year (15.15±0.24, t=7.227, P<0.01). Anterior, central, and posterior layer of corneal optical density values had a downward trend at early stage, and increased significantly in 6-and 12-month (anterior layer t=7.143, 6.177, central layer t=7.508, 6.563, posterior layer t=6.722, 8.533;P<0.01). Only the values decreased significantly in posterior layer at 1-week (baseline 10.21±0.14 vs. 1-week 9.91±0.14, t=-2.348, P=0.024). The corneal optical density value of ≤2 mm diameter began to increase significantly at 1-month (baseline 12.88±0.14 vs. 1-month 13.31±0.19, t=2.158, P=0.037),>2 mm and ≤6 mm diameter at 3-month (baseline 11.71±0.13 vs. 3-month 12.50±0.19, t=3.213, P=0.003), and>6 mm and ≤10 mm diameter at 6-month (baseline 11.40±0.30 vs. 6-month 13.70±0.33, t=7.635, P=0.000). The high values lasted for 1 year at this three areas. However, >10 mm and ≤12 mm diameter had no obvious change in optical density (F=1.668, P>0.05). In addition, the significant reduction of optical density values at early stage were mainly concentrated in the posterior layer of the cornea and the>6 mm and ≤10 mm diameter. Conclusions: Orthokeratology transiently increases corneal transparency of the posterior layer and the>6 mm and ≤10 mm diameter at early stage. However, long-term wearing can cause a decrease of transparency within a 10 mm diameter range. The corneal transparency changes first at the center of the optical zone, then gradually expanding to the periphery, and the anterior, central and posterior layers of cornea are all affected. We speculate orthokeratology affect the corneal oxygen supply and compress cornea mechanically, that leads to corneal stromal remodeling. (Chin J Ophthalmol, 2019, 55:435-441).

A wearable device to monitor ocular comfort

PURPOSE

To develop and evaluate a wearable device (the lens awareness logger, LAL) to record subjective lens awareness during contact lens wear.

METHODS

The LAL is a compact electronic event-logging device incorporating a tactile switch and belt-clip. Forty contact lens wearers (20 symptomatic and 20 asymptomatic) took part in a clinical evaluation of the LAL device. Subjects were instructed to wear their habitual soft contact lenses for 2 days (>8 h wear) and use the LAL device. Subjects activated the LAL device immediately prior to lens application and deactivated it following lens removal. If a subject became aware of their contact lenses at any point throughout the wear period they were instructed to depress the button on the LAL device.

RESULTS

The mean number of lens awareness events per hour was 1.3, although there was substantial variation between subjects (standard deviation 1.4). The distribution of lens awareness events throughout the contact lens wearing period showed significantly elevated awareness following lens application and prior to lens removal (p < 0.0001). In addition, symptomatic subjects had a statistically higher percentage of LAL events in the second half of the lens-wearing day compared with asymptomatic subjects (p = 0.02). The LAL findings for each subject appear consistent across the two days (i.e. no fatigue or learning effect). The LAL device was well accepted by subjects with 38 of the 40 subjects reporting it was either 'very easy' or 'fairly easy' to use.

CONCLUSION

The LAL device was able to monitor ocular comfort throughout a period of contact lens wear and was well accepted by subjects. The ability of the LAL device to track ocular awareness events through the day, with high temporal resolution, means it is likely to be a key tool to further understanding of contact lens associated discomfort and dry eye disease.

Co-delivery of latanoprost and timolol from micelles-laden contact lenses for the treatment of glaucoma

Glaucoma is a group of irreversible ocular diseases which result in damage to the optic nerve and vision loss. The objective of the present work was to develop micelles-laden contact lenses (CLs-M) that could achieve the sustained release of timolol and latanoprost simultaneously for the treatment of glaucoma. CLs-M were obtained by free radical polymerization of HEMA monomer with timolol and latanoprost loaded mPEG-PLA micelles. The prepared CLs-M had a minimal impact on critical CLs properties, and could release timolol and latanoprost in simulated tear fluid for 144 h and 120 h individually, which is promising for extended drugs release applications. The in vivo PK study on rabbit eyes showed sustained timolol and latanoprost release for up to 120 h and 96 h in tear fluid, respectively. There was significant improvement of the mean residence time (79.6-fold and 122.2-fold) and bioavailability (2.2-fold and 7.3-fold) for both timolol and latanoprost delivered by CLs-M compared with eye drops. An in vivo PD study in a rabbit model with high IOP showed sustained reduction in the IOP for over 168 h. The relative pharmacological availability (PA) of CLs-M was 9.8 times as high as the eye drops. The protein adsorption, ocular irritation study and histological examination study indicated the safety of CLs-M. Therefore, this work has demonstrated the promising potential of micelles-laden CLs to co-deliver timolol and latanoprost for an extended period of time to treat glaucoma.

Soft and flexible material-based affinity sensors

Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field.

Effect of gold nanoparticles on timolol uptake and its release kinetics from contact lenses: In vitro and in vivo evaluation

Contact lenses are ideally suited for extended drug delivery to the ocular tissues, but incorporation of any particulate system affects the critical properties of the contact lens. Timolol loading by the conventional soaking method does not significantly alter the critical properties of the contact lens. However, there are challenges of low drug loading and high burst release. This research work aimed to investigate the effect of gold nanoparticles (GNPs) on loading and its release kinetics from the contact lens using the soaking method. In one approach, GNPs were loaded into the timolol soaking solution (GNPs-SS), and in another approach, GNPs were incorporated into the contact lenses (GNPs-CL) during fabrication. The contact lenses were soaked at two different concentrations of timolol (i.e., 2 mg/ml and 4 mg/ml). Swelling and optical transmittance were not significantly affected by the presence of GNPs in the contact lenses. A significant uptake/loading of timolol using the GNPs in both the approaches was observed. The in vitro flux data showed no significant improvement in the release rate profiles of timolol when using both approaches. However, the in vivo study in the rabbit tear fluid showed high timolol concentration with the GNPs-laden contact lens at all timepoints in comparison to the soaked contact lenses without GNPs. The in vivo pharmacodynamic study in rabbits showed a 2 mmHg average fall in intraocular pressure (72 h) using the GNPs-laden contact lenses, while the soaked contact lenses without GNPs and eye drops solution (0.5 %w/v) showed 2 mmHg. The drug distribution study in the ocular tissue showed a significant improvement in the drug deposition with the GNPs-laden contact lenses in the ciliary muscle and conjunctiva. This study successfully demonstrated the potential of GNPs to enhance the uptake of drug from the drug soaking solution to treat glaucoma without compromising the critical properties of contact lens. STATEMENT OF SIGNIFICANCE: In this study, we have overcome the limitation of the conventional soaking method of low drug loading and high burst release from the contact lenses. We have investigated the effect of gold nanoparticles (GNPs) on the timolol loading and its release kinetics from the contact lenses. The study revealed the potential of GNPs to enhance the uptake of timolol from the timolol soaking solution to treat glaucoma without compromising the critical lens properties.

Antimicrobial and physicomechanical natures of silver nanoparticles incorporated into silicone-hydrogel films

PURPOSE

The effects of silver nanoparticles (AgNPs) incorporated in silicone-hydrogel films on their physicochemical properties and microbial activity were investigated.

METHODS

Silicone-hydrogel composite films (SiHCFs) were prepared by in-situ chemical reduction of silver ions added in different concentrations (0, 10, 20, 30, 40, 60, and 80 ppm) followed by ultraviolet (UV) casting. The reduction of silver ions into AgNPs was confirmed by transmission electron microscopy (TEM) and absorption spectroscopy over ultraviolet and visible (UV-vis) wavelengths. Incorporation of AgNPs into SiHCFs was confirmed by UV-vis absorption spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopic mapping. The physico- mechanical properties of the SiHCFs were evaluated. Antimicrobial activity and biofilm formation of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were assessed.

RESULTS

TEM, UV-vis absorption, SEM, and EDX mapping showed that silver ions were reduced in the mixture of co-polymerizing monomers and incorporation of AgNPs into SiHCFs was achieved. Mechanical properties of the SiHCFs were enhanced with increasing AgNPs concentration without affecting their chemical and thermal properties. SiHCFs exhibited transmittance greater than 90% at a wavelength 600 nm. Bacterial growths in the solutions bathing the SiHCFs with increasing silver concentration were 95, 78, 4, 2, 0, 0, 0% respectively, for Escherichia coli; 95, 82, 4, 0.6, 0, 0, 0% for Pseudomonas aeruginosa; and 93, 79, 4, 0.5, 0, 0, 0% for Staphylococcus aureus.

CONCLUSIONS

Incorporation of AgNPs into SiHCFs demonstrated sufficient release of AgNPs to inhibit bacterial growth and reduce biofilm formation, with collateral enhancement of some mechanical properties of SiHCFs.

Emerging Therapeutics for Ocular Surface Disease

PURPOSE OF REVIEW

The purpose of this article is to review treatment advances in ocular allergy that include the treatment of the various signs and symptoms of the allergic inflammatory response of the ocular surface.

RECENT FINDINGS

Recent studies have demonstrated improved pharmacological effect of topical agents with artificial tears and cold compresses; brimonidine, a new ophthalmic decongestant which has demonstrated decreased rebound conjunctivitis; and potential use of contact lens and other novel delivery instruments to increase medication retention time. Currently, there have been limited advances in novel ophthalmic treatments. Non-pharmacological interventions have demonstrated in a randomized control study that artificial tears and the use cold compresses alone or in combination with ophthalmic antihistamines can enhance the effectiveness of a traditional pharmacological therapy. The primary advances have been the start of head-to-head studies comparing various agents actively being used in the treatment of ocular allergy. In addition, there has been increasing interest in the development of novel delivery systems to increase residence time of pharmacological agents in the ocular surface such as nanoparticles, microfilms; examining novel pathways of controlling the allergic inflammatory response of the ocular surface such as modulation of cytokines, transcription factors, and immunophilins.

The impact of vinegar on pathogenic Acanthamoeba astronyxis isolate

Acanthamoeba keratitis (AK) is a severe corneal disease that was reported by WHO as the second most common infectious cause of blindness after trachoma; contact lens wear is considered one of the main risk factors in its transmission. Thus, the treatment of AK is crucial but, the inability of medical agents to completely eradicate the resistant cyst, together with their toxic effects, suggest that new agents are needed. Vinegar has been known long ago as a simple and available disinfectant with antimicrobial effects, so the present study aimed to test the effect of different concentrations of vinegar solution on Acanthamoeba astronyxis isolate, along the period of 1 h in comparison to parasite and chlorhexidine controls. Post hoc test analysis revealed a highly significant difference between the vinegar-treated parasites and both controls, as regards the viable and non-viable mean cysts count. Vinegar concentration of 5% exhibited the highest mean of non-viable cysts along the time intervals, while the lowest was shown with 0.04% where also, no viable cysts were detected at 60 min. All tested concentrations behaved in a time-dependent manner. There was a positive correlation with a significant outcome between the different concentrations and the mean of the non-viable parasites along time. Transmission electron microscopy of treated cysts revealed corrugated altered cell wall with loss of ridges and detachment and shrinkage of content. Treated trophozoites showed flattening of the acanthopodia with thinned out plasma membrane and degenerated cytoplasmic content. The study highlighted the potential use of vinegar as an adjuvant in the prevention and treatment of AK.

[A machine learning model on orthokeratology lens fitting based on the data of optometry examination]

Objective: To get an orthokeratology lens fitting model according to the research of the optometry examination data, which can help to improve the work efficiency and increase the hitting rate of prescription. Methods: The relationship between the basic optometry examination data and the effective optometry prescription was evaluated. We got 1 467 sets of data, including 80%(1 173) for training and 20%(294) for testing. The trail results were used for the 20% testing sets, and 100% completed sets for verification. With the contrast of accuracy, we got the influencing variables and the fitting model. Logistic regression and linear regression analysis were applied to the training set for building a fitting model, and the receiver operating characteristic curve (ROC curve) was drawn to determine the optimal threshold of the logistic regression model (1.0).The trail results are used for the 20% testing sets, 100% completed sets for verification. With the contrast of accuracy (ACC), we get the influencing variables and the fitting model. Results: Kf-FK and Ks-SK were selected as dependent variables. Through analysis of Stepwise regression, we found the influencing variables of Kf-FK were Kf(P=0.01), E(mean) (P=0.027), and CYL(P<0.001), with FK=6.23+0.866kf-1.69 E(mean)+0.16CYL, and the precision rate was 81%(r(2)=0.95). The influencing variables of Ks-SK were Ks (P<0.001), CYL (P=0.00), and E(mean) (P<0.001), with SK=6.84+0.862ks-0.28E(mean)-1.3CYL, and the precision rate was 80%(r(2)=0.93). By selecting the logistic method and decision tree analysis for glasses design, the influencing variables were KS (P<0.001)and CYL (P<0.001). The logistic function was Design=-45.7+0.82Ks+6.027CYL, and the precision rate was 87%. Conclusions: The combination of AI and medical data can verify the expert experience and guide the optometrist to locate the prescription quickly and accurately. Try to break the traditional mode of fitting with wearing the orthokeratology lens shortly, and it is possible for us to position the prescription quickly through the calculation of a computer. (Chin J Ophthalmol, 2019, 55: 105-110).

[From evidence to clinical practice: myopia control among children in refraction clinics]

Over the past decade, breakthrough has been made on myopia progression control with a lot of evidence from clinical trials, but the effective clinical application of many of them remained immature. Though refraction clinics have been set up in many specialized hospitals offering spectacles to correct refractive error, there was few protocol or standard of treatment for reducing myopia progression. This commentary reviews the latest and essential publications and presents critical advice on applying the research findings to clinical practice. (Chin J Ophthalmol, 2019, 55: 89-92).

[Clinical study on microcirculation changes of bulbar conjunctiva after contact lens wear]

Objective: To explore the changes of microcirculation of the bulbar conjunctiva after wearing the contact lens and the relationship between contact lens discomfort and bulbar conjunctiva microcirculation. Methods: Prospective cohort study. The postgraduate students from School of Ophthalmology & Optometry and School of Biomedical Engineering of Wenzhou Medical University were included in this prospective cohort study. The subjects wore soft contact lenses, and the right eye was selected as the experimental eye. The ocular surface disease index (OSDI) questionnaire, Schirmer I and tear break-up time tests were completed before and after wearing the contact lens, and the conjunctival blood flow velocity and microvascular network density were also assessed by using functional slit lamp biomicroscopy. The changes of the indicators after wearing the contact lens were observed and the correlation between the subjective feelings of the wearers and the microcirculation parameters of the bulbar conjunctiva and the main factors affecting the subjective feelings of the wearers were analyzed. Results: Twenty-seven subjects were enrolled in the study, including 8 males and 19 females, aged (22.7±1.6) years. The OSDI score was 11.860± 7.783 before wearing the contact lens and 24.017±12.181 after wearing the contact lens. The comparison before and after wearing the contact lens was statistically significant (t=-4.356, P<0.001). The conjunctival blood flow velocity was (0.534±0.132) mm/s before wearing the contact lens and (0.587±0.134) mm/s after wearing the contact lens. The comparison was statistically significant before and after wearing the lens (t=-2.076, P=0.048). OSDI was positively correlated with blood flow velocity at 1 month after wearing the contact lens (correlation coefficient r=0.383, P=0.048). The test results of the independent variables in the generalized estimating equation model showed that time and blood flow velocity were statistically significant (P<0.05). Conclusions: The blood flow velocity of the bulbar conjunctiva was increased after wearing the contact lens, and the contact lens discomfort of the wearers was positively correlated with the blood flow velocity of the bulbar conjunctiva. (Chin J Ophthalmol, 2019, 55: 98-104).

Profile, knowledge, and attitude of contact lens users regarding contact lens wear in Ghana

BACKGROUND

Contact lenses are gaining popularity in developing countries as an alternative to spectacles for the correction of refractive errors. It is needful, therefore, to generate information to guide the mode of practice, and assist the industry in developing products for the increasing contact-lenses-user population. The purpose of this study was to identify the demographic profile, as well as the knowledge, attitude to wear and care regimen of wearers of contact lenses in Ghana.

METHODS

In a cross-sectional study, case folders of 87 users of contact lenses were selected from the database eye contact lenses practices. The folders were reviewed for the demographic profile, type, and purpose for which the contact lenses were prescribed. Forty-two (42) contact lenses users were then randomly surveyed, using a semi-structured questionnaire to collect information on their knowledge, lens wear regimen, and attitudes regarding lens hygiene. Chi-square test was used to test associations between demographics and lens wear variables.

RESULTS

Out of the 87 cases reviewed, 46 (52.9%) were females and 41 (47.1%) males. Their ages ranged from 15 to 68 years with a mean age of 28.62 ± 9.38 years. The majority- 65 (75%) - were youthful (≤ 40 years), with the highest proportion of them - 46 (53%) - being between 20-29 years. The majority - 60 (68.9%) - had a tertiary level of education. Soft contact lenses were commonly worn by 68 (78.2%) users while 19 (21.8%) wore rigid gas permeable lenses. The purpose for wearing contact lenses included for vision correction - 46 (52.9%), followed by for cosmesis - 23 (26.4%) - and therapeutic reasons -18 (20.7%). The commonest refractive error corrected was myopia - 38 (43.7%), followed by astigmatism -19 (21.8%) and hyperopia 6 (6.9%). Among the 42 users who responded to the questionnaire, by proportion, the majority -17 users (40.5%) - were introduced to contact lenses by optometrists. All respondents reported previous symptoms associated with the use of their contact lenses, but slightly more than half, 25 (57.1%) did yearly follow-up visits.

CONCLUSION

The majority of contact lenses used in Ghana are soft lenses, for the purpose of vision correction. The use of contact lenses was common among individuals in their early adulthood and those with tertiary education.

Differences between tears of contact lens wearers studied by photon correlation spectroscopy

PURPOSE

The purpose was to evaluate if there are differences between tears of contact lens (CL) wearers of different materials detectable by measuring the hydrodynamic diameter of tear components through photon correlation spectroscopy (PCS).

METHODS

Tears of 59 CL wearers and tears of 39 non-wearers were collected by glass capillary. Wearers were divided into groups depending on the CL material: (i) hydrogels of II FDA group (H-II, 15 subjects), (ii) hydrogels of IV FDA group (H-IV, 13 subjects), (iii) silicone hydrogels (SH, 31 subjects). PCS analyses were performed at 25 °C on samples diluted with deionized water with tear concentration (10 ± 2)% ^V/_W to obtain, for each subject, the average hydrodynamic diameter (d_H,avg) of tear components by analyzing intensity fluctuations in time of scattered light.

RESULTS

Means of d_H,avg calculated on each group were found, on increasing order, to be 256 nm (std dev 18 nm) for non-wearers, 297 nm (std dev 45 nm) for H-II, 360 nm (std dev 76 nm) for SH, and 391 nm (std dev 85 nm) for H-IV with statistical differences between each group of wearers compared to non-wearers and between groups of wearers except between SH and H-IV.

CONCLUSIONS

PCS reveals the differences between tears of CL wearers of different materials, not only between tears of wearers and non-wearers.

Prevalence, habits and outcomes of using contact lenses among medical students

Objectives:

To determine the prevalence, reasons of use, reported hygienic practices, and complications related to CLs’ usage, and to assess awareness of medical students about CLs’ hygienic behaviours, King Abdulaziz University (KAU), Jeddah, Saudi Arabia.

Methods:

A cross-sectional design was done. A multi-stage stratified random sampling was utilized to select 536 medical students. A validated, self-administered, anonymous questionnaire was used. Both descriptive and inferential statistics were applied.

Results:

The prevalence of current users of CLs was 40.5%. Females reported significantly much higher prevalence of usage compared to males (OR=8.38; 95% CI:5.2-13.3). Second-year students, and those living in university dormitory had the highest prevalence of CLs usage compared to others. The commonest reason for wearing CLs was cosmetic purpose. Improper CLs-hygienic practices were reported; as exceeding the period required for renewal (45.6%), sharing lenses (16.6%), and sleeping (29.9%), swimming (24.6%) or showering (29.0%) with CLs. Only 16.6% of the participants cleaned their lenses daily. At least one CLs’ related complications was reported by 30.4% of the users. Acute red eye (19.8%), conjunctivitis (18.9%), and corneal abrasion (8.3%) were the commonest CLs’ complications.

Conclusion:

A relatively high prevalence of CLs’ usage was found. Participants were aware about CLs-hygienic practices. However, unhygienic CLs-related practices and complications were also reported. Provision of educational messages and training on sound CLs’ hygienic practices are needed.