Control of myopia using orthokeratology lenses in Scandinavian children aged 6 to 12 years. Eighteen-month data from the Danish Randomized Study: Clinical study Of Near-sightedness; TReatment with Orthokeratology Lenses (CONTROL study).

PURPOSE: To investigate the efficacy of myopia control defined by axial elongation and safety of orthokeratology lenses (OKL) in a Scandinavian (Danish) population. METHODS: Sixty Danish children aged 6-12 years with myopia ranging from 0.5 to 4.75 dioptres (D) spherical component and refractive astigmatism ≤2.5 D in both eyes were randomly assigned to either OKL or single-vision spectacles (SVS). Study duration was 18 months. Outcome measures were axial length (AL) measured with Lenstar LS900 (Haag-Streit, Koeniz, Switzerland) and adverse events graded with Efron Grading Scale for Contact Lens Complications. RESULTS: Nineteen participants completed the 18-month follow-up in the OKL group and 28 in the SVS group. The average AL elongation in the OKL group was 0.24 mm smaller as compared to the SVS group (95% confidence interval 0.12-0.36, mixed model adjusted for baseline sex, age and AL). There were no fast progressors (>0.75 D/year) in the OKL group during the follow-up period in contrast to 22% in the SVS group. No treatment-requiring or vision-threatening adverse events were observed. CONCLUSION: Orthokeratology lenses reduced AL elongation in myopic Scandinavian children by 59%, with no treatment-requiring or vision-threatening adverse events. The results align with outcomes of previous clinical trials.

Contact Lens Technology: From Fundamentals to Applications.

Contact lenses are ocular prosthetic devices used by over 150 million people worldwide. Primary applications of contact lenses include vision correction, therapeutics, and cosmetics. Contact lens materials have significantly evolved over time to minimize adverse effects associated with contact lens wearing, to maintain a regular corneal metabolism, and to preserve tear film stability. This article encompasses contact lens technology, including materials, chemical and physical properties, manufacturing processes, microbial contamination, and ocular complications. The function and the composition of the tear fluid are discussed to assess its potential as a diagnostic media. The regulatory standards of contact lens devices with regard to biocompatibility and contact lens market are presented. Future prospects in contact lens technology are evaluated, with particular interest given to theranostic applications for in situ continuous monitoring the ocular physiology.

Extended depth of focus contact lenses vs. two commercial multifocals: Part 1. Optical performance evaluation via computed through-focus retinal image quality metrics / Lentes de contacto de profundidad de foco extendido vs. dos lentes multifocales comerciales: Parte 1. Evaluación del rendimiento óptico del enfoque computarizado mediante métricas de calidad de imagen retinianas

Purpose: To compare the computed optical performance of prototype lenses designed using deliberate manipulation of higher-order spherical aberrations to extend depth-of-focus (EDOF) with two commercial multifocals. Methods: Emmetropic, presbyopic, schematic eyes were coupled with prototype EDOF and commercial multifocal lenses (Acuvue Oasys for presbyopia, AOP, Johnson & Johnson & Air Optix Aqua multifocal, AOMF, Alcon). For each test configuration, the through-focus retinal image quality (TFRIQ) values were computed over 21 vergences, ranging from -0.50 to 2.00 D, in 0.125 D steps. Analysis was performed considering eyes with three different inherent aberration profiles: five different pupils and five different lens decentration levels. Results: Except the LOW design, the AOP lenses offered ‘bifocal’ like TFRIQ performance. Lens performance was relatively independent to pupil and aberrations but not centration. Contrastingly, AOMF demonstrated distance centric performance, most dominant in LOW followed by MED and HIGH designs. AOMF lenses were the most sensitive to pupil, aberrations and centration. The prototypes demonstrated a ‘lift-off’ in the TFRIQ performance, particularly at intermediate and near, without trading performance at distance. When compared with AOP and AOMF, EDOF lenses demonstrated reduced sensitivity to pupil, aberrations and centration. Conclusion: With the through focus retinal image quality as the gauge of optical performance, we demonstrated that the prototype EDOF designs were less susceptible to variations in pupil, inherent ocular aberrations and decentration, compared to the commercial designs. To ascertain whether these incremental improvements translate to a clinically palpable outcome requires investigation through human trials (AU)

Objetivo: Comparar el rendimiento óptico computado de los prototipos de lentes de contacto diseñadas mediante manipulación deliberada de aberraciones esféricas de alto orden para conseguir la profundidad de foco extendida (EDOF) con dos lentes multifocales comerciales. Métodos: Se adaptaron lentes de contacto con prototipo EDOF, y lentes multifocales comerciales a ojos esquemáticos présbitas emétropes (Acuvue Oasys para presbicia, AOP, Johnson & Johnson & Air Optix Aqua multifocal, AOMF, Alcon). Para cada configuración de la prueba se obtuvieron los valores de la calidad de imagen de la retina a través del foco (TFRIQ) en 21 vergencias, que oscilaron entre -0,5 y 2D, en pasos de 0,125D. Se llevó a cabo el análisis considerando los ojos con tres perfiles de aberración diferentes: cinco pupilas diferentes y cinco niveles de descentramiento de lentes distintos. Resultados: Exceptuando el diseño LOW, las lentes AOP aportaron un rendimiento TFRIQ de tipo ‘bifocal’. El desempeño de las lentes fue relativamente independiente de la pupila y aberraciones, pero no del descentramiento. Por contra, AOMF demostró un rendimiento céntrico en visión lejana, más dominante en el diseño LOW, seguido de los diseños MED y HIGH. Las lentes AOMF fueron más sensibles a la pupila, aberraciones y centrado. Los prototipos demostraron un efecto de mejora en el rendimiento TFRIQ, particularmente en visión intermedia y próxima, sin pérdida de rendimiento en visión lejana. Al compararlas con las lentes AOP y AOMF, las lentes EDOF demostraron una reducción de la sensibilidad al factor pupila, las aberraciones y el centrado. Conclusión: Con la calidad de imagen de la retina a través del foco, como medida del rendimiento óptico, demostramos que los diseños del prototipo EDOF fueron menos susceptibles a las variaciones de la pupila, las aberraciones oculares inherentes, y al descentramiento, en comparación a los diseños comerciales. Se precisa más investigación futura, mediante ensayos en humanos, para verificar si estas mejoras incrementales se trasladan a resultados clínicamente evaluables (AU)

Extended depth of focus contact lenses vs. two commercial multifocals: Part 2. Visual performance after 1 week of lens wear / Lentes de contacto de profundidad de foco extendido vs. dos lentes multifocales comerciales: Parte 2. Rendimiento visual tras una semana de uso

Purpose: To compare the visual performance of prototype contact lenses designed via deliberate manipulation of higher-order spherical aberrations to extend-depth-of-focus with two commercial multifocals, after 1 week of lens wear. Methods: In a prospective, participant-masked, cross-over, randomized, 1-week dispensing clinical-trial, 43 presbyopes [age: 42-63 years] each wore AIROPTIX Aqua multifocal (AOMF), ACUVUE OASYS for presbyopia (AOP) and extended-depth-of-focus prototypes (EDOF) appropriate to their add requirements. Measurements comprised high-contrast-visual-acuity (HCVA) at 6 m, 70 cm, 50 cm and 40 cm; low-contrast-visual-acuity (LCVA) and contrast-sensitivity (CS) at 6 m and stereopsis at 40 cm. A self-administered questionnaire on a numeric-rating-scale (1-10) assessed subjective visual performance comprising clarity-of-vision and lack-of-ghosting at various distances during day/night-viewing conditions and overall-vision-satisfaction. Results: EDOF was significantly better than AOMF and AOP for HCVA averaged across distances (p ≤ 0.038); significantly worse than AOMF for LCVA (p = 0.021) and significantly worse than AOMF for CS in medium and high add-groups (p = 0.006). None of these differences were clinically significant (≤2 letters). EDOF was significantly better than AOMF and AOP for mean stereoacuity (36 and 13 seconds-of-arc, respectively: p ≤ 0.05). For clarity-of-vision, EDOF was significantly better than AOP at all distances and AOMF at intermediate and near (p ≤ 0.028). For lackof-ghosting averaged across distances, EDOF was significantly better than AOP (p < 0.001) but not AOMF (p = 0.186). EDOF was significantly better than AOMF and AOP for overall-vision satisfaction (p ≤ 0.024). Conclusions: EDOF provides better intermediate and near vision performance than either AOMF or AOP with no difference for distance vision after 1 week of lens wear (AU)

Objetivo: Comparar el rendimiento visual de un prototipo de lentes de contacto diseñadas mediante manipulación deliberada de aberraciones esféricas de alto orden, para ampliar la profundidad de campo con dos lentes multifocales comerciales, tras una semana de uso. Métodos: En un ensayo clínico prospectivo, ciego para los participantes, transversal, aleatorizado, con uso de lentes durante una semana, 43 présbitas [Edad: 42-63 años] utilizaron lentes AIROPTIX Aqua multifocal (AOMF), ACUVUE OASYS para presbicia (AOP) y de profundidad de foco extendido (EDOF) adecuados a sus requisitos de adición. Las mediciones incluyeron agudeza visual de alto contraste (HCVA) a 6 m, 70 cm, 50 cm y 40 cm, agudeza visual de bajo contraste (LCVA), sensibilidad de contraste (CS) a 6 m, y estereopsis a 40 cm. Un cuestionario auto-administrado sobre una escala de evaluación numérica (1-10) valoró el rendimiento visual subjetivo incluyendo la nitidez de visión y la ausencia de imágenes fantasma a diversas distancias en condiciones de visión diurna/nocturna, así como la satisfacción sobre la visión general. Resultados: EDOF fue considerablemente mejor que AOMF y AOP para la media de las distancias HCVA (p ≤ 0,038); considerablemente peor que AOMF para LCVA (p = 0,021) y considerablemente peor que AOMF para CS en los grupos de adición media y elevada (p = 0,006). Ninguna de estas diferencias fueron clínicamente significativas (≤ 2 letras). EDOF fue considerablemente mejor que AOMF y AOP para la estereoagudeza media (36 y 13 segundos de arco, respectivamente: p ≤ 0,05). Para la claridad de visión, EDOF fue considerablemente mejor que AOP en todas las distancias, y AOMF para las distancias intermedia y cercana (p ≤ 0,028). Para la falta de imágenes fantasma promediada a las diferentes distancias, EDOF fue considerablemente mejor que AOP (p < 0,001) pero no así AOMF (p = 0,186). EDOF fue considerablemente mejor que AOMF y AOP en cuanto a satisfacción sobre la visión general (p ≤ 0,024). Conclusiones: EDOF aporta un mejor desempeño de visión intermedia y cercana que AOMF o AOP, sin diferencia de visión lejana tras una semana de uso de lentes de contacto multifocales (AU)

Ocular surface and tear film status among contact lens wearers and non-wearers who use VDT at work: comparing three different lens types.

PURPOSE: To analyze differences in the ocular surface appearance and tear film status of contact lens wearers and non-wearers in a group of visual display terminals (VDT) workers and additionally to assess differences between lens materials. METHODS: Cross-sectional study of 236 office workers, of whom 92 were contact lens wearers. Workers provided information on their contact lenses (conventional hydrogel, silicone hydrogel or rigid gas permeable lenses) and exposure to VDT at work. Ocular surface and tear film status were determined by the presence of bulbar, limbal and lid redness, lid roughness and corneal staining type, and by Schirmer's and tear break-up time tests (TBUT). A generalized linear model was used to calculate the crude (cRR) and age- and sex-adjusted (aRR) relative risk to measure the association between ocular surface and tear film abnormalities and contact lens use and type. RESULTS: The aRR of ocular surface abnormalities was higher in contact lens wearers compared to non-wearers: bulbar redness (aRR 1.69; 95% CI 1.25-2.30), limbal redness (aRR 2.87; 1.88-4.37), lid redness (aRR 2.53; 1.35-4.73) and lid roughness (aRR 7.03; 1.31-37.82). VDT exposure > 4 h/day increased wearers' risk of limbal and lid redness. Conventional hydrogel wearers had the highest risk of ocular surface abnormalities, followed by silicone hydrogel wearers. Both contact and non-contact lens wearers had a high prevalence of altered TBUT (77.3 and 75.7% respectively) and Schirmer (51.8 and 41.3%). CONCLUSIONS: Regular contact lens use during VDT exposure at work increases risk of bulbar, limbal and lid redness, and lid roughness, especially in soft contact lens wearers. The high prevalence of altered TBUT and Schirmer's results in all participants suggests that VDT use greatly affects tear film characteristics.

Analysis of the power profile of a new soft contact lens for myopia progression / Análisis del perfil de potencia de las nuevas lentes de contacto blandas para miopía progresiva

No disponible

The measurement of intraocular pressure over positive soft contact lenses by rebound tonometry / Medición de la presión intraocular sobre lentes de contacto blandas positivas, mediante tonometría de rebote

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 (AU)

Objetivo: Investigar si la precisión de las mediciones de la presión intraocular (PIO), utilizando la tonometría de rebote sobre las lentes de contacto (LC) desechables de hidrogel (etafilcon A), se ve afectada por la potencia positiva de dichas lentes. Métodos: El grupo experimental incluyó a 26 sujetos, (8 varones, 18 mujeres). Se realizó la medición de la PIO en los ojos derechos de los sujetos, de modo aleatorio, utilizando un Tonómetro de Rebote (ICare). Las LC tenían potencias de +2,00D y +6,00D. Se realizaron mediciones con cada lente de contacto, y también antes y después a su uso. Resultados: El valor de la PIO obtenido con ambas LC fue considerablemente menor al valor sin LC (t del test; p<0,001), aunque no se halló una diferencia significativa entre las dos potencias de las lentes. Conclusiones: La tonometría de rebote sobre las LC positivas de hidrogel origina un cierto grado de subestimación del PIO. Este resultado no sufrió variación entre las dos lentes positivas utilizadas en el experimento, a pesar de la gran diferencia de potencia, y por tanto del espesor de las lentes. Los optometristas deberían de tener en cuenta estos resultados en a la hora de medir el PIO con un tonómetro de rebote, con lentes de contacto de mayor potencia (AU)

Risk Factors for Contact Lens-Related Microbial Keratitis: A Case-Control Multicenter Study.

PURPOSE: The most feared complication of contact lens (CL) wear is microbial keratitis (MK), even though its incidence remains low. This study aimed to identify the risk factors of CL-related MK in a large, prospective, multicenter case-control study. METHODS: A multicenter case-control study was designed. The CL-related MK subpopulation (Case) was compared with healthy CL wearers (Control) using a 52-item anonymous questionnaire designed to determine subject demographics and lens wear history. Univariate and multivariate logistic regression analyses were performed to compare both groups. RESULTS: The study enrolled 499 cases and 508 controls. The risk factors associated with the greatest increased odds of CL-related MK were as follows: using disinfecting solution more than 3 months (odds ratio [OR]=1.94), cosmetic CL wear and use of multipurpose disinfection solution (1.37 each), overnight wear, and soft lens use (OR=1.24 each). The protective factors associated with the greatest reduction in OR were fitting by an ophthalmologist (OR=0.73) and hyperopia versus myopia (OR=0.75). CONCLUSIONS: The infectious determinants were linked to the type of lenses, hygiene routine, CL handling, disinfecting solution, and storage case. This study aimed to highlight the increasingly CL-related MK, which likely occurs because of lack of patient information regarding basic rules of hygiene and CL care and handling.

Comparison of Occurrence of Free Volumes for Rigid Gas Permeable and Soft Contact Lenses.

BACKGROUND: The polymeric materials: hydrogel, silicone--hydrogel and methacrylic acid are used in ophthalmology for the manufacture of contact lenses. It is important to research the structure of these materials, mainly the prevalence of free volumes. OBJECTIVES: The study has been conducted in order to comparison the presence of free volume gaps in the structure of the polymer soft contact lenses: Etafilcon A (hydrogel), Narafilcon A (silicone-hydrogel) and the polymer rigid gas permeable (RGP) contact lens (Fluor-Silicon-Methacrylat-Copolymer). In addition, to demonstrate differences in the occurrence of free volumes between types of represented contact lenses. MATERIAL AND METHODS: Three types of polymer contact lenses were used as materials: Etafilcon A, Narafilcon A and Fluor-Silicon-Methacrylat-Copolymer. The study was done by means of positron annihilation lifetime spectroscopy (PALS). RESULTS: As a result of the performed measurements, a graphical curve resulted which describes the relationship between the number of the annihilation acts in the time function. Significant changes were observed in the ortho-positronium long life component τ3 and their intensities between the examined polymer contact lenses. CONCLUSIONS: The conducted study using the Tao-Eldrup model indicates the presence of free volume holes in all research materials. There is a clear difference in the free volume sizes and their fractions between measured contact lenses are connected with oxygen permeability in these lenses. The results lead to the following connection: contact lenses of higher oxygen permeability coefficients and a water content of less, have more and larger free volumes than contact lenses of less oxygen permeability coefficient.

Optical power distribution of refractive and aspheric multifocal contact lenses: Effect of pupil size.

PURPOSE: To evaluate the power profile within the optic zone of different designs of multifocal contact lenses (CLs) and to analyze how the effect of pupil size could impact on their optical performance. METHODS: The optical power distribution within the optic zones of multifocal CLs was measured by the Nimo TR1504 (LAMBDA-X, Belgium). The multifocal CLs under study were the Acuvue Bifocal, the Acuvue Oasys for Presbyopia, the PureVision Multifocal and the PureVision 2 for Presbyopia. Each design was considered in all their available addition powers. All lenses had a nominal power of -3.0D. At the same time, three lenses of each model were considered and five consecutive readings of each lens were performed. RESULTS: The results show that the PureVision Multifocal and the PureVision 2 for Presbyopia have aspheric power profiles. Both designs showed aspheric center-near designs with a smoother progression of the optical power in the PureVision 2 for Presbyopia. The Acuvue Bifocal and the Acuvue Oasys for Presbyopia are shown to have concentric alternating near and far zones. Apart from the refractive rings, the Acuvue Oasys for Presbyopia showed an increase in negative (or less positive) values toward the periphery of the lens. CONCLUSIONS: Besides the refraction, the knowledge of the power profiles of multifocal CLs and the effect of pupil size on the optical distribution of these lenses could be crucial to understand the performance of these designs when they are fitted.

Tear exchange and contact lenses: a review / Intercambio de lágrima y lentes de contacto: revisión

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 (AU)

El intercambio de lágrima bajo las lentes de contacto facilita la reposición continua de fluido entre la superficie ocular y las lentes. Dicho intercambio es considerablemente menor con el uso de lentes blandas en lugar de rígidas. Como resultado, se incrementa la acumulación de desechos de la película de lágrimas y los sub-productos metabólicos entre la córnea y las lentes de contacto blandas, lo que conlleva complicaciones potenciales. Se han propuesto innovaciones en el diseño de las lentes, pero no se ha reportado ninguna mejora sustancial en lo referente al intercambio de lágrima con las lentes de contacto blandas. Los investigadores han determinado el intercambio de lágrimas tras el uso de lentes utilizando diversos métodos, principalmente la fluorofotometría. Sin embargo, debido a las limitaciones técnicas, se conoce poco acerca de la hidrodinámica relacionada con las lentes y, hasta la fecha, no se ha mostrado un intercambio de lágrima substancial con lentes de contacto. El conocimiento adicional sobre el intercambio de lágrima podría resultar esencial para ayudar a diseñar lentes de contacto mejoradas, con la perspectiva de aliviar ciertas respuestas oculares adversas. Este artículo revisa la literatura hasta la fecha acerca de la importancia, implicaciones y medición del intercambio de lágrima con lentes de contacto (AU)

Quantitative optical inspection of contact lenses immersed in wet cell using swept source OCT.

We demonstrate swept source optical coherence tomography (OCT) imaging of contact lenses (CLs) in a wet cell and comprehensive quantitative characterization of CLs from volumetric OCT datasets. The approach is based on a technique developed for lens autopositioning and autoleveling enabled by lateral capillary interactions between the wet cell wall and the lens floating on the liquid surface. The demonstrated OCT imaging has enhanced contrast due to the application of a scattering medium and it improves visualization of both CL interfaces and edges. We also present precise and accurate three-dimensional metrology of soft and rigid CLs based on the OCT data. The accuracy and precision of the extracted lens parameters are compared with the manufacturer's specifications. The presented methodology facilitates industrial inspection methods of the CLs.

Modern scleral contact lenses: A review.

Scleral contact lenses (ScCL) have gained renewed interest during the last decade. Originally, they were primarily used for severely compromised eyes. Corneal ectasia and exposure conditions were the primary indications. However, the indication range of ScCL in contact lens practices seems to be expanding, and it now increasingly includes less severe and even non-compromised eyes, too. All lenses that partly or entirely rest on the sclera are included under the name ScCL in this paper; although the Scleral Lens Education Society recommends further classification. When a lens partly rests on the cornea (centrally or peripherally) and partly on the sclera, it is called a corneo-scleral lens. A lens that rests entirely on the sclera is classified as a scleral lens (up to 25 mm in diameter maximum). When there is full bearing on the sclera, further distinctions of the scleral lens group include mini-scleral and large-scleral lenses. This manuscript presents a review of the current applications of different ScCL (all types), their fitting methods, and their clinical outcomes including potential adverse events. Adverse events with these lenses are rare, but the clinician needs to be aware of them to avoid further damage in eyes that often are already compromised. The use of scleral lenses for non-pathological eyes is discussed in this paper.

In vitro power profiles of multifocal simultaneous vision contact lenses.

PURPOSE: To evaluate the power profile of multifocal contact lenses (CLs) using a new technology based on quantitative deflectometry. METHODS: The Nimo TR1504 was used to analyze the power distribution of multifocal CLs. The CLs under study were: Air Optix Aqua Multifocal Low, Medium and High Addition and Focus Progressives. Three lenses of each model were considered. RESULTS: All multifocal CLs showed a power profile characterized by a change toward more positive power values when aperture sizes become smaller. The near refractive addition of the lenses under study was +2.61 D, +1.44 D, +1.30 D and +0.30 D for the Focus Progressives, the Air Optix Aqua Multifocal High, Medium Add and Low Add, respectively. The refractive power of the Focus Progressives did not reach the value of the nominal distance power until a radial distance of 0.9 mm from the center of the lens. For the Air Optix Aqua Multifocal Low Add the distance nominal power was reached at a radial distance of 1.5mm from the center of the lens, whereas this occurred at a distance of 1.8mm for the Air Optix Aqua Multifocal Medium and High Add. CONCLUSION: The relation between the pupil diameter of the patients and the power profile of these CLs has a crucial implication on the final distance correction and near addition that these lenses provide to patients. Practitioners should know the power profile of these CLs and measure the pupil diameter of each patient in different situations in order to carry out a customized fitting.

Contact lens in keratoconus.

Contact lenses are required for the visual improvement in patients with keratoconus. Various contact lens options, such as rigid gas permeable (RGP) lenses, soft and soft toric lenses, piggy back contact lenses (PBCL), hybrid lenses and scleral lenses are availble. This article discusses about selection of a lens depending on the type of keratoconus and the fitting philosophies of various contact lenses including the starting trial lens. A Medline search was carried out for articles in the English language with the keywords keratoconus and various contact lenses such as Rose k lens, RGP lens, hybrid lens, scleral lens and PBCL.

In vitro power profiles of daily disposable contact lenses.

PURPOSE: To evaluate and compare the distribution of refractive power within the optic zone of different soft contact lenses and to investigate the effect of lens decentration on the power profiles. METHODS: The Nimo TR1504 instrument was used to measure the optical power across different aperture diameters (from 1.5mm to 5.5mm in steps of 0.5mm) of four daily disposable contact lenses: DAILIES TOTAL1, Proclear 1-Day, SofLens daily disposable and 1-DAY ACUVUE MOIST. Measurements were performed using a wet cell. Power data were evaluated when contact lenses were in its centered position and after inducing different amounts of lens decentration (from 0.2mm to 1.0mm in steps of 0.2mm). RESULTS: All contact lenses showed an increase - more negative - in lens power with distance from the lens center. The amount of change varied depending on the lens. It was about 10% of lens power for DAILIES TOTAL1 (-0.29diopters (D)), SofLens daily disposable (-0.36D), and Proclear 1-Day (-0.32D) whereas 1-DAY ACUVUE MOIST showed a percentage variation of 3.3% (-0.10D). After inducing a lens decentration up to 1mm, the power curves were shifted in the negative direction. However, the change obtained in lens power compared with well-centered position was always lower than a quarter of diopter both for all the lenses and aperture diameters. CONCLUSIONS: Our results showed a variation of the refractive power from the lens center, becoming more negative toward the periphery, with a negligible effect of the decentration for all disposable contact lenses studied.

Lens parameter changes under in vitro and ex vivo conditions and their effect on the conjunctiva.

PURPOSE: To quantify changes in contact lens parameters induced by lens wear and determine whether these changes are associated with contact lens-induced conjunctival staining (CLICS). METHODS: In vitro: Lens diameter, sag, edge shape, base curve of six contact lens brands (balafilcon, comfilcon, etafilcon, lotrafilcon B, omafilcon and senofilcon) measured at 21°C and 35°C (eye temperature). Ex vivo: Diameter of lenses collected from a prospective, randomised, contra-lateral, cross-over clinical trial from 36 subjects wearing all lens types for 1 week daily wear, measured in 35°C PBS after removal. Ocular surface was examined for lens-induced conjunctival staining by masked examiner. RESULTS: In vitro: Changes in diameter and base curve outside ISO tolerance were found with etafilcon A and omafilcon A. Ex vivo: Comfilcon A and etafilcon A had greatest shrinkage in diameter (0.18mm) and base curve (0.11mm steeper) with temperature increase from 21°C to 35°C. Senofilcon A, lotrafilcon B and balafilcon A maintained most stable parameters between 21°C and 35°C. Changes in diameter and base curve from lens wear were not correlated with CLICS (p>0.49). Multivariate analysis showed significantly greater levels of lens induced staining were associated with lens modulus (p<0.001) and knife (p<0.001) and chisel (p<0.001) edge shapes. CONCLUSIONS: Parameter changes induced by lens wear were associated with increasing temperature, but these changes in lens diameter and base curve did not induce CLICS. Modulus and edge shape were associated with increased CLICS. The susceptibility of etafilcon A and omafilcon A lenses to parameter changes might be related to their high water content.