Infectious keratitis associated with contact lens wear: REGINFECOR multicenter study

This 32-centre multicentre study addresses the lack of knowledge about the prevalence and significance of microbial keratitis (MK) associated with contact lens (CL) wear in Spain. A total of 304 cases recruited from 32 hospitals were studied and showed that infectious keratitis associated with contact lens wear mainly affects young women during the summer months. In this study, soft lenses with monthly replacement and single solution cleaning were most commonly used, purchased and fitted in opticians' shops. Common risk factors were identified among users, such as topping off solutions, prolonging the life of lenses, and frequently sleeping, swimming and showering with lenses. Overnight lens wear was significantly associated with a higher incidence of corneal opacities, and the presence of Pseudomonas aeruginosa in bacterial cultures was associated with more severe sequelae and a greater need for corneal transplantation. Although most cases were benign, the time taken to heal was long, which poses a problem for working patients. This study provides valuable epidemiological, microbiological and risk factor information and estimates the incidence of CL related MK in Spain to be approximately 1 case per 30,000 inhabitants per year.

Contact lenses and ocular dysbiosis, from the transitory to the pathological

Normal ocular microbiota is composed of different Gram-negative and positive bacterial communities that act as commensals on the ocular surface. An imbalance in the homeostasis of the native species or dysbiosis triggers functional alterations that can eventually lead to ocular conditions, indicating the use of contact lenses as the most relevant predisposing factor. Through a bibliographic review that added scientific articles published between 2018 and 2022, the relationship between healthy ocular microbiota and dysbiosis associated with the use of contact lenses that trigger ocular conditions was analyzed. The ocular microbiota in healthy individuals is mainly composed of bacteria from the phyla: Proteobacteria, Actinobacteria and Firmicutes. These bacterial communities associated with the use of contact lenses develop dysbiosis, observing an increase in certain genera such as Staphylococcus spp. and Pseudomonas spp., which under normal conditions are commensals of the ocular surface, but as their abundance is increased, they condition the appearance of various ocular conditions such as corneal infiltrative events, bacterial keratitis and corneal ulcer. These pathologies tend to evolve rapidly, which, added to late detection and treatment, can lead to a poor visual prognosis. It is suggested that professionals in the ophthalmology area learn about the composition of the communities of microorganisms that make up this ocular microbiota, in order to correctly distinguish and identify the causative agent, thereby providing a adequate and effective treatment to the user.

The effect of prolonged and nocturnal use of contact lenses on the cornea: about a case of corneal decompensation and decreased endothelial count

Corneal edema and decreased endothelial cell count are complications related to chronic low-grade hypoxia experienced by contact lens wearers, primarily due to prolonged and overnight wear. This case shows the example of a patient who has blurred vision problems in both eyes and who underwent a complete ophthalmologic examination that included photographs, corneal topography and endothelial cell count. Subsequently, the corneal metabolism, the etiopathogenesis and the complications derived from the use of contact lenses are reviewed.

A refined model on flow and oxygen consumption in the human cornea depending on the oxygen tension at the interface cornea/post lens tear film during contact lens wear

The study of oxygen consumption rate under" in vivo" human cornea during contact lens wear has been technically a challenge and several attempts have been made in the last 20 years to model the physiology of the human cornea during contact lens wear. Unfortunately, some of these models, based on a constant corneal oxygen consumption rate, produce areas on the cornea where the oxygen tension is negative, which has no physical sense. In order to avoid such inconsistency, different researchers have developed alternative models of oxygen consumption, which predict the likely oxygen metrics available at the interface cornea/post lens tear film by determination of oxygen flux, oxygen consumption, and oxygen tension through the different layers (endothelium, stroma, and epithelium). Although oxygen deficiency produces corneal edema, corneal swelling, hypoxia, acidosis, and other abnormalities, the estimation of the oxygen distribution below the impact of a contact lens wear is interesting to know which lens transmissibility was adequate to maintain the cornea and avoid epithelial and stromal anoxia. The estimation of minimum transmissibility for a lens for extended wear applications will be very useful for both clinicians and manufacturers. The aim of this work is to present a complete discussion based on Monod kinetics model that permits give an estimation of oxygen partial pressure distribution, the profile distribution of corneal flux and oxygen consumption rate, and finally the estimation of the relaxation mechanism of the cornea depending on the oxygen tension at the interface cornea/post lens tear film. Relaxation time in this context can quantify the capability of the corneal tissue to adapt to increasing concentrations of oxygen. It is proposed this parameter as a biological meaningful indicator of the interaction between contact lens polymers and living tissues such as the corneal cellular layer.

The effects of light scatter when using a photochromic vs. non-photochromic contact lens

PURPOSE

To assess the visual effects of wearing both an activated and an inactivated photochromic contact lens, with a direct comparison to a non-photochromic contact lens worn in the fellow eye. This study focused on the visual effects of scatter quantified as the minimum distance between two points of light, and the diameter of the halo and starbursts that surround a bright white point source.

METHODS

60 subjects (aged 18-65 years) were measured in a contralateral design where lens type was randomly assigned, one type to each eye. During activated testing, all visual measures of both study lenses were made while each eye was illuminated by a violet (λ_max=365, half bandwidth 20nm) activator, which caused steady-state activation of the photochromic lens during the period of testing. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light. Glare geometry was measured using an aperture (∼4mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread of halos (diffusion around the source) and visual spokes. The head was stabilized using an adjustable head-rest assembly and the eye was aligned and monitored with a bore camera.

RESULTS

Compared to the non-photochromic lens, and based on the stimulus conditions used in these measurements, the activated and inactivated photochromic lens reduced the light spread using the two-point threshold technique by 32% and 19% respectively; the diameter of the halos were reduced by 44% and 16% respectively; and the spokes were narrowed by 39% and 20% respectively. Based on 95% confidence interval testing, these effects were all statistically significant (p<0.05).

CONCLUSIONS

These results are consistent with previous data showing that soft contact lenses with a photochromic additive can improve many aspects of visual function, consistent with their level or activation. Our past data focused on visual function under bright light conditions (e.g., glare disability, discomfort, photostress recovery and chromatic contrast) with an activated photochromic. In this study, we found differences even in the inactivated state, using less intense stimuli (10cd/m² at the source). This suggests that the photochromic lens improves the effects of light scatter even at lower luminance.

Physicochemical stability of contact lenses materials for biomedical applications

PURPOSE

The physicochemical stability, thermal and water plasticizing effect on transport properties of contact lenses (CL) were analyzed to verify its capacity to maintain the original properties after being dehydrated and rehydrated.

METHODS

Two daily disposable (nesofilcon A and delefilcon A) and two monthly CL (comfilcon A and lotrafilcon B) were used. Measurements of refractive index (RI), water content (WC), chemical structure and thermal properties were taken: new (N), after dehydration (D) and rehydrated (R). RI and WC were accessed using a digital automated refractometer (CLR-12-70). Chemical structure was evaluated by a Fourier Transformed Infrared Spectroscopy (FTIR-ATR) and Differential Scanning Calorimetry (DSC) with a calorimeter (Mettler Toledo DSC-821).

RESULTS

The FTIR spectrum of N, D and R was quite similar for all CL, with higher differences observed in the transmission between 3500-3000cm^-1 due to the hydroxyl group (OH). After dehydration and rehydration, there were no significant changes in the chemical structure. RI and WC of the CL rehydrated did not vary significantly from the initial CL (p>0.05) and thermal properties also confirm that the behavior did not change. It was observed that the glass-transition temperature decrease with increased WC.

CONCLUSION

No significant alterations were observed in the physicochemical structure of the materials after dehydration and rehydration showing a good stability of their components. The strong water plasticizing effect in the silicone hydrogel lens materials improves flexibility and chain mobility and may should be considered for other biomedical applications.

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.

Endophthalmitis caused by Fusarium: An emerging problem in patients with corneal trauma. A case series

BACKGROUND

Although fortunately very rare in countries with a temperate climate, certain factors, such as clinical or pharmacological immunosuppression, may cause Fusarium-related fungal infections to become an emerging problem. Moreover, Fusarium is one of the most important etiological agents in exogenous endophthalmitis, which is often favored by the disruption of the epithelial barriers.

AIMS

The aim of this series of clinical cases is to identify characteristic clinical findings that may allow an early diagnosis and more efficient management of this ophthalmologic emergency.

METHODS

Three cases of endophthalmitis due to Fusarium solani and Fusarium oxysporum, diagnosed in 2009, 2010, and 2014 in patients from two different health regions belonging to the same health system and separated by around 43 miles, are presented. The Fusarium isolates were initially identified microscopically and the species subsequently confirmed by sequencing the elongation factor alpha (EFα) and internal transcribed spacers (ITS). Susceptibility to antifungal agents was determined using the EUCAST broth dilution method.

RESULTS

Evolution was poor as two of the three patients progressed to phthisis bulbi despite surgical measures and broad-spectrum antifungal antibiotic therapy.

CONCLUSIONS

It is essential to rapidly instigate multidisciplinary measures to combat suspected endophthalmitis due to Fusarium given the poor prognosis of this type of infection.

The measurement of intraocular pressure over positive soft contact lenses by rebound tonometry

PURPOSE

To investigate if the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) contact lenses (CL) is affected by the positive power of the CLs.

METHODS

The experimental group comprised 26 subjects, (8 male, 18 female). IOP measurements were undertaken on the subjects' right eyes in random order using a Rebound Tonometer (ICare). The CLs had powers of +2.00D and +6.00D. Measurements were taken over each contact lens and also before and after the CLs had been worn.

RESULTS

The IOP measure obtained with both CLs was significantly lower compared to the value without CLs (t test; p<0.001) but no significant difference was found between the two powers of CLs.

CONCLUSIONS

Rebound tonometry over positive hydrogel CLs leads to a certain degree of IOP underestimation. This result did not change for the two positive lenses used in the experiment, despite their large difference in power and therefore in lens thickness. Optometrists should bear this in mind when measuring IOP with the rebound tonometer over plus power contact lenses.

Reliability of power profiles measured on NIMO TR1504 (Lambda-X) and effects of lens decentration for single vision, bifocal and multifocal contact lenses

PURPOSE

To evaluate the repeatability of power profiles measured on NIMO TR1504 (Lambda-X, Belgium) and investigate the effects of lens decentration on the power profiles for single vision (SV), bifocal (BF) and multifocal (MF) contact lenses.

METHODS

Accuracy of the sphere power was evaluated using single vision BK-7 calibration glass lenses of six minus and six plus powers. Three SV and four BF/MF contact lenses - three lenses each, were measured five times to calculate the coefficients of repeatability (COR) of the instrument. The COR was computed for each chord position, lens design, prescription power and operator. One lens from each type was measured with a deliberate decentration up to ±0.5mm in 0.1mm steps.

RESULTS

For all lenses, the COR varied across different regions of the half-chord position. In general, SV lenses showed lower COR compared to the BF/MF group lenses. There were no noticeable trends of COR between prescription powers for SV and BF/MF lenses. The shape of the power profiles was not affected when lenses were deliberately decentered for all SV and PureVision MF lenses. However, for Acuvue BF lenses, the peak to trough amplitude of the power profiles flattened up to 1.00D.

CONCLUSION

The COR across the half-chord of the optic zone diameter was mostly within clinical relevance except for the central 0.5mm half-chord position. COR were dependent on the lens type, whereby BF/MF group produced higher COR than SV lenses. The effects of deliberate decentration on the shape of power profiles were pronounced for lenses where the profiles had sharp transitions of power.

Multidrug resistant Fusarium keratitis

CASE REPORT

We report a case of keratitis in a female contact lens wearer, who developed a deep corneal abscess. The culture of a corneal biopsy scraping was positive for multiresistant Fusarium solani. The patient has a complicated clinical course and failed to respond to local and systemic antifungal treatment, requiring eye enucleation.

CONCLUSION

Fusarium keratitis may progress to severe endophthalmitis. Clinical suspicion is paramount in order to start antifungal therapy without delay. Therapy is complex due to the high resistance of this organism to usual antifungal drugs.

Corneal Regeneration After Photorefractive Keratectomy: A Review

Photorefractive keratectomy (PRK) remodels corneal stroma to compensate refractive errors. The removal of epithelium and the ablation of stroma provoke the disruption of corneal nerves and a release of several peptides from tears, epithelium, stroma and nerves. A myriad of cytokines, growth factors, and matrix metalloproteases participate in the process of corneal wound healing. Their balance will determine if reepithelization and stromal remodeling are appropriate. The final aim is to achieve corneal transparency for restoring corneal function, and a proper visual quality. Therefore, wound-healing response is critical for a successful refractive surgery. Our goal is to provide an overview into how corneal wounding develops following PRK. We will also review the influence of intraoperative application of mitomycin C, bandage contact lenses, anti-inflammatory and other drugs in preventing corneal haze and post-PRK pain.

Tear exchange and contact lenses: a review

Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses. This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

Short-term corneal changes with gas-permeable contact lens wear in keratoconus subjects: a comparison of two fitting approaches

PURPOSE

To evaluate changes in anterior corneal topography and higher-order aberrations (HOA) after 14-days of rigid gas-permeable (RGP) contact lens (CL) wear in keratoconus subjects comparing two different fitting approaches.

METHODS

Thirty-one keratoconus subjects (50 eyes) without previous history of CL wear were recruited for the study. Subjects were randomly fitted to either an apical-touch or three-point-touch fitting approach. The lens' back optic zone radius (BOZR) was 0.4mm and 0.1mm flatter than the first definite apical clearance lens, respectively. Differences between the baseline and post-CL wear for steepest, flattest and average corneal power (ACP) readings, central corneal astigmatism (CCA), maximum tangential curvature (KTag), anterior corneal surface asphericity, anterior corneal surface HOA and thinnest corneal thickness measured with Pentacam were compared.

RESULTS

A statistically significant flattening was found over time on the flattest and steepest simulated keratometry and ACP in apical-touch group (all p<0.01). A statistically significant reduction in KTag was found in both groups after contact lens wear (all p<0.05). Significant reduction was found over time in CCA (p=0.001) and anterior corneal asphericity in both groups (p<0.001). Thickness at the thinnest corneal point increased significantly after CL wear (p<0.0001). Coma-like and total HOA root mean square (RMS) error were significantly reduced following CL wearing in both fitting approaches (all p<0.05).

CONCLUSION

Short-term rigid gas-permeable CL wear flattens the anterior cornea, increases the thinnest corneal thickness and reduces anterior surface HOA in keratoconus subjects. Apical-touch was associated with greater corneal flattening in comparison to three-point-touch lens wear.

Publication analysis of the contact lens field: what are the current topics of interest?

PURPOSE

To determine the main current research interests of scientists working in the contact lens field.

METHODS

All articles published in the 2011 issues of all journals included in the Journal Citation Reports subject category Ophthalmology were inspected to expose those papers related to the contact lens field. Information regarding source journal was obtained and authorship details were recorded to determine the top most prolific authors, institutions and countries. A comprehensive list of key words was compiled to generate a two-dimensional term map in which the frequency of occurrence of a particular term is defined by label size and the distance between two terms is an indication of the relatedness of these terms, based on their co-occurrences within groups of key words. Clusters of related terms were also identified.

RESULTS

Visual examination of all articles uncovered a total of 156 papers, published in 28 different journals. Contact Lens & Anterior Eye, Eye & Contact Lens and Optometry and Vision Science had 27 articles each. The most prolific authors and institutions revealed the predominance of countries with long research tradition in the contact lens field. Ten different word clusters or areas of interest were identified, including both traditional, yet unresolved issues (e.g., comfort or dry eye), and the latest research efforts (e.g., myopia control).

CONCLUSIONS

These findings, which revealed contact lenses to be a fertile area of research, may be of relevance to new researchers as well as to those interested in exploring the latest research trends in this scientific discipline.

Evaluation of safety and efficacy of a new multipurpose disinfecting solution on silicone hydrogel contact lenses

PURPOSE

To evaluate the safety and efficacy of a new multipurpose disinfecting solution (MPDS) with a formulation that includes aloe vera on its composition.

METHODS

This is a prospective, randomized, double-masked clinical trial with a crossover design that included seven examinations. Two different MPDSs, Avizor Alvera® (study solution) and All Clean Soft® (control solution), each were used for 1 month. Comfilcon A silicone hydrogel contact lenses were used during the trial. The main outcome variables were corneal staining and deposits on the surfaces of the contact lenses. Other parameters including ocular surface response, contact lens wettability, user satisfaction, and adverse events, were analyzed according to the International Organization for Standardization (ISO) 11980:2010 guidance for clinical investigation.

RESULTS

Twenty subjects (10 women, 10 men) (mean age, 27.7±5.6 years; range, 20-41) were included. No differences between both MPDSs were found in the percentage of subjects with corneal staining >0 at day 30 (study: 35%, control: 50%; p=0.46); neither in the percentage of subjects with deposits on the surface of the contact lens >0 at day 30 (study: 26.32%, control: 52.63%; p=0.18). The study MPDS received higher rates in comfort (study: 8.14±1.09, control: 7.94±0.92; p=0.56) and satisfaction at day 30 (study: 8.63±0.91, control: 8.29±0.80; p=0.19), however the scores were not significantly different with the control MPDS.

CONCLUSIONS

The clinical trial showed that the study MPDS is safe, efficient, and has acceptable physiologic tolerance, according to the ISO 11980:2010 guidance for clinical investigation.