Adaptive wavefront sensor for accurate characterization and evaluation of circular optical elements

Lower- and higher-order wave-front aberrations of soft contact lenses were accurately measured with a Shack-Hartmann wave-front sensor. The soft contact lenses were placed in a wet cell filled with lens solution to prevent surface deformation and desiccation during measurements. Aberration measurements of conventional toric and multifocal soft contact lenses and a customized soft contact lens have proved that this method is reliable. A Shack-Hartmann wave-front sensor can be used to assess optical quality of both conventional and customized soft contact lenses and to assist in enhancing lens quality control.

Background: Rigid gas permeable (RGP) and silicone hydrogel (SH) contact lenses with specific designs are currently being used to improve visual function in patients with keratoconus. However, there are minimal data available comparing the effects of these lenses on visual function in patients with keratoconus. The objectives of this study were to compare visual acuity and contrast sensitivity using spectacles, RGP lenses, and SH lenses, and to evaluate the effects of RGP and SH lenses on higher-order aberrations and visual quality in eyes with keratoconus. The relationship between visual outcomes, aberration, and visual quality were also examined. Methods: This was a pilot study involving 13 eyes from nine subjects with keratoconus. Subjects were fitted with RGP and SH contact lenses. Visual acuity and contrast sensitivity were measured using Snellen and Pelli-Robson charts, respectively. Ocular aberrations and visual quality were measured using an OPD-Scan II device. All measurements were conducted before and after contact lens wear. Results: Significantly better visual acuity was obtained with RGP lenses than with spectacles or SH lenses ( P <0.001). No significant difference in contrast sensitivity values was detected between RGP and SH lenses ( P =0.06). Both SH and RGP lenses significantly reduced total ocular and higher-order aberrations ( P <0.001) when compared with spectacles, but RGP lenses reduced trefoil, coma, and spherical aberrations more than SH lenses. No significant difference in astigmatic aberrations was found between RGP and SH lenses ( P =0.12). Negative correlations were found between visual acuity and coma aberration and contrast sensitivity with higher-order aberrations and coma, trefoil, and astigmatic aberrations. Regarding visual quality, no significant difference was found between RGP and SH lenses, but RGP significantly improved visual quality when compared with spectacles ( P =0.04). Conclusion: RGP lenses provided better visual acuity and greater reduction of aberrations than spectacles or SH lenses in patients with keratoconus. However, more data are needed to confirm these findings. Keywords: visual acuity, contrast sensitivity, aberration, visual quality, keratoconus

To understand soft contact lens (SCL) and gas-permeable (GP) lens wearers' behaviors and knowledge regarding exposure of lenses to water. The Contact Lens Risk Survey (CLRS) and health behavior questions were completed online by a convenience sample of 1056 SCL and 85 GP lens wearers aged 20 to 76 years. Participants were asked about exposing their lenses to water and their understanding of risks associated with these behaviors. Chi-square analyses examined relationships between patient behaviors and perceptions. GP lens wearers were more likely than SCL wearers to ever rinse or store lenses in water (rinsing: 91% GP, 31% SCL, P < 0.001; storing: 33% GP, 15% SCL P < 0.001). Among SCL wearers, men were more likely to store (24% vs. 13%, P = 0.003) or rinse (41% vs. 29%, P = 0.012) their lenses in water. Showering while wearing lenses was more common in SCL wearers (86%) than GP lens wearers (67%) (P < 0.0001). Swimming while wearing lenses was reported by 62% of SCL wearers and 48% of GP lens wearers (P = 0.027). Wearers who rinsed (SCL; P < 0.0001, GP; P = 0.11) or stored lenses in water (SCL; P < 0.0001, GP P = 0.007) reported that this behavior had little or no effect on their infection risk, compared with those who did not. Both SCL (P < 0.0001) and GP lens wearers (P < 0.0001) perceived that distilled water was safer than tap water for storing or rinsing lenses. Despite previously published evidence of Acanthamoeba keratitis' association with water exposure, most SCL, and nearly all GP lens wearers, regularly expose their lenses to water, with many unaware of the risk.

BACKGROUND: An increase in corneal infiltrates and ulcers, especially among young contact lens users was noticed in our out-patient service over the last years. This prompted us to examine contact lens related corneal infiltrates and ulcers. PATIENTS AND METHODS: Retrospective study of 119 consecutive patients (134 eyes) who did wear contact lenses. 15 had problems in both eyes. We evaluated age of the patients, proportion of soft and hard contact lenses, number and location of infiltrates, the type of bacteria and the permanent corneal damage caused by scarring. RESULTS: Out of the 134 eyes evaluated 127 (94.8%) used soft contact lenses and 7 (5.2%) had used hard contact lenses for refractive correction. Mean age of patients was 28.4 years ± 12.9a. 80.6% (108 eyes) had central solitary infiltrates, 14.9% (20 eyes) had multiple peripheral infiltrates, and 4.5% (6 eyes) developed corneal ulcers. In 25.4% (34 eyes) we were able to isolate bacteria. Most of the bacteria were found in eyes with soft lenses (33 out of 34 eyes, 97%), in only one (3%) case a hard contact lens was used. Gram-negative bacteria such as serratia spp. (7 eyes), pseudomonas spp. (6 eyes), stenotrophomonas maltophilia (6 eyes) and klebsiella oxytoca (5 eyes) were predominantly isolated. 26 of 127 eyes (20.5%) with soft contact lens related keratitis healed with a corneal scar, resulting in permanent visual damage. CONCLUSION: The majority of keratitis was caused by wearing soft contact lenses. One fifth of these comparatively young patients retained a corneal scar. These findings should influence the information given to a patient concerning the choice of refractive correction.

This study investigated the clinical astigmatism threshold at which toric soft contact lenses (CLs) provide superior visual acuity (VA) compared with spherical CLs, and how pupil size affects this. A novel pupil-controlled vision testing system (PUCS) was developed to assess VA across different pupil sizes by dynamically adjusting lighting conditions. A randomised, crossover, partially participant-masked clinical study was conducted with 53 habitual soft CL wearers (84 eyes; ages 20-40). Eyes were categorised into seven astigmatism groups (0.00 to -1.50 DC in 0.25 DC steps). Each eye was tested with three corrections: spherical soft CLs, custom toric soft CLs, and full-correction spectacles. VA was assessed using PUCS at five pupil diameters (2.5 mm, 4.0 mm, 5.5 mm, maximum, and minimum). The primary outcome was the between-correction difference in PUCS logMAR visual acuity, assessed at each pupil diameter. Secondary measures included conventional VA, subjective ratings, and lens preference. PUCS VA decreased significantly with increasing pupil diameter across all corrections (p< 0.0001). Toric CLs provided significantly better PUCS VA than spherical CLs for astigmatism of -0.75 DC and greater, regardless of pupil diameter (p< 0.001). The mean toric-spherical difference was approximately 0.06 logMAR (≈3 letters) at -0.75 DC and 0.12 logMAR (≈6 letters) at -1.50 DC. Toric CL performance was comparable to spectacle correction across all cylinder groups. Participants favoured toric CLs over spherical lenses from -0.75 DC upwards, with no participants preferring spherical CLs at -1.25 DC or greater (p< 0.001). Toric CLs demonstrated excellent rotational stability. The PUCS system provided robust evidence that toric CLs offer significant visual benefits at -0.75 DC or greater (within the tested range up to -1.50 DC), irrespective of pupil diameter. These findings support routine soft toric CL prescribing for astigmatism correction at or above this threshold to optimise visual performance and patient satisfaction. This study was registered at ClinicalTrials.gov (Identifier: NCT04613882).

An innovative experimental method for studying the influence of supersonic flow on laser beam transmitting has been proposed. The wavefront phase properties and the dynamic wavefront change of laser beam traversing supersonic flow can be detected by Hartmann-Shack (H-S) wavefront sensor. Beam aberrations are constructed by adopting Zernike mode-reconstruction theory. The centroid change of laser beam and the far-field properties can be obtained by further analyzing the experimental data. In the paper, the experimental principle is presented, and wavefront aberrations with several different flow parameters are given. Some beam-quality criteria such as Zernike aberration coefficient, PV and RMS value, circle energy, Strehl ratio, and centroid change of beam, are also calculated. Experimental results show that the stage of flow establishing, stabilizing and ending can be detected by using H-S wavefront sensor. By comparing the result of no flow with that of a given-parameter flow, defocus and astigmatism aberration increase obviously. At the same time, the Strehl ratio is reduced and the beam quality is degraded. The same conclusion can be obtained by comparing no test-model with the given-structural test-mode in same flow. Moreover, the wavefront aberration of laser beam in the condition of different flow parameters can also be measured and compared accurately by using the test method.

The ageing population will become one of the biggest issues affecting Singapore in the near future. Ophthalmic practitioners will need to be ready to deal with an increased prevalence of glaucoma, cataract, age related maculopathy and even presbyopia. As presbyopes lose their ability to accommodate at near vision, visual aids such as progressive lenses, bifocal lenses, reading glasses, monovision contact lenses and multifocal contact lenses are prescribed to help them with reading difficulties and improve their daily lives. Interestingly, an international survey in 2011 revealed zero percent soft multifocal contact lenses was prescribed in Singapore for presbyopia correction. Although there are improvements in multifocal lens design and material, no new research being conducted to investigate the presbyopic lens fitting status in Singapore. Nonetheless, recent studies have shown an increased in multifocal contact lenses prescribing trends, perhaps reflecting not just the availability of newer multifocal contact lenses, but also improvement in practitioners’ confidence and knowledge in multifocal contact lenses. However, in spite of the available guides on choosing multifocal contact lenses, there is no comprehensive way to help the practitioner in selecting the best option for an individual. As such, an examination of the simplest way of predicting the most suitable multifocal lens for a patient will only enhance and add to the current evidence available. A survey was conducted to understand the Singaporean practitioners’ attitude towards soft multifocal lenses and its prescribing trend. In this survey, an increase in the rate of soft multifocal contact lens fitting was observed, the perception of the unavailability of an ‘ideal’ multifocal contact lens, and increased chair time in fitting soft multifocal contact lenses were identified as significant barriers. However, enablers such as the increased in practitioners’ motivation, confidence and proactiveness in fitting soft multifocal contact lenses were gathered. Additionally, this study aimed to compare the relative performance of three daily-replacement soft contact lenses for presbyopic correction in an optometric practice population in Singapore. The three daily-disposable multifocal contact lenses included in this study were 1-day Acuvue® Moist Brand Multifocal Contact Lenses for Presbyopia (Johnson &amp; Johnson Vision Care, Jacksonville, FL), Clariti 1-day Mulitfocal (Cooper Vision, NY) and Dailies AquaComfort Plus Multifocal (Alcon, Fort worth, TX). In this crossover study design, 35 presbyopic participants with myopia were fitted in a random order with three different types of multifocal contact lens. After 1 month, visual performance was quantified by high contrast distance, intermediate and near visual acuity, defocus curve under photopic and mesopic conditions, reading speed, Near Activity Visual Questionnaire rating and Photographic questionnaire for Photic Phenomena. The results showed comparable levels of binocular distance, intermediate and near visual acuity achieved with the three different types of multifocal contact lens at 1-month follow up. However, a better distance acuity at distance under mesopic condition for AquaComfortPlus. In terms of subjective participant lens preference, nine participants (26%) preferred Moist multifocal, 16 participants (46%) preferred Clariti multifocal and 10 participants (28%) preferred AquaComfortPlus multifocal. However, lens preference was not related to demographic factors relating to age, gender, refractive error and the magnitude of reading addition or physiological characteristic such as pupil size. In terms of the performance of participants with their preferred lens when observing the defocus curve under mesopic condition, it emerged that there was an interaction between lens types and acuity at different levels of defocus. From this, it seems that lens preference may perhaps be driven by a change in visual experience that only manifested in low illumination conditions, suggesting it may be important to conduct objective measure such as visual acuity under mesopic condition when fitting modern-day multifocal contact lenses. It remains a hope for the future that new clinical tests or more diverse lens designs would be valuable to help the practitioner to improve the chances of first time success when fitting a multifocal contact lens for presbyopic correction.

PurposeIntroduced around the turn of the 21st century, silicone hydrogel contact lenses alleviated hypoxic anterior eye complications due to their high oxygen transmissibility. The purpose of this work is to update earlier surveys by describing international trends in silicone hydrogel daily wear contact lens fitting between 2000 and 2023. MethodAn annual contact lens prescribing survey was sent to eye care practitioners in up to 71 countries between 2000 and 2023. Data relating to 260,144 daily wear soft contact lens fits undertaken in 20 countries returning reliable longitudinal data were analysed in respect of silicone hydrogel daily wear contact lens fitting. ResultsThere has been a dramatic increase in silicone hydrogel daily wear lens fits (p < 0.0001), increasing from 2.8 % of all daily wear soft lens fits in 2000 to 73.7 % in 2023. Of all daily wear soft contact lenses prescribed to males, 44.6 % were silicone hydrogel lenses, compared with 43.5 % for females (p = 0.0146). The mean age of those wearing silicone hydrogel daily wear lenses was 32.0 ± 14.5 years, compared to 30.4 ± 13.6 years for those wearing daily wear hydrogel lenses (p < 0.0001). Between 2019–2023, the average percentage of fits was – (a) material type: silicone hydrogel – 73 %; mid-water content hydrogels – 13 %; high water content hydrogels – 9 %; and low water content hydrogels – 5 %, and (b) lens design: spherical – 44 %, toric – 32 %, multifocal – 17 %, monovision – 4 %, and ‘other’ – 3 %. ConclusionThe dramatic increase in silicone hydrogel contact lens prescribing for daily wear has been commensurate with the introduction of multiple lens brands and an ongoing expansion of lens designs, parameters and replacement frequency options. The balance between silicone hydrogel and hydrogel lens prescribing is perhaps starting to approach an equilibrium.

High average power operation of the Mercury Laser induces dynamic aberrations to the laser beam wavefront. Analysis of recent data indicates that up to 4 waves of low order aberration (mainly focus error or power, with spatial resolution < 0.5 cm{sup -1}) could be expected at each pass. Because of the magnitude of the wavefront error, the logical position is to place a deformable mirror (DM) at the M11 position, where the DM will correct the beam between passes 1 & 2 and 3 & 4. Currently, there are only two established commercial vendors offering complete adaptive optic (AO) systems that can accommodate the Mercury beam size (45 x 75 mm) which are compatible with high damage threshold coatings. Xinetics (MA, USA) offers a complete AO system along with a Shack-Hartmann wavefront sensor. The Xinetics DM is based on lead magnesium niobate (PMN) technology. A number of US aerospace firms as well as NIF use Xinetics PMN technology for their DMs. Phasics (Paris, France) offers a complete AO solution with its proprietary SID-4, a four-way shearing interferometric wavefront sensor capable of high resolution (over 100 x 100 sampling points). The Phasics system includes a bimorph deformable mirror from Night-n-Opt (Moscow, Russia) that uses lead zirconate titanate (PZT) technology. Various high power laser laboratories around the world such as LULI (France), HELEN (UK), and GEKKO (Japan) are using the PZT-based bimorph DM in their system. While both DM technologies are equivalent and have been deployed in high-energy laser systems, the PZT based bimorph DM offers two distinct features that makes it more attractive for high average power laser systems. The bimorph DM uses two layers of PZT actuators with the outer layer acting as power correctors, capable of correcting up to 20 waves of power. The Xinetics DM offers a maximum stroke of 4 waves. In addition, Night-N-Opt has also designed a water-cooled DM with a silicon based substrate (as opposed to a glass substrate) specifically for high average power laser systems--an option that is currently not available for PMN based DMs.

Letters to the Editor

Short and ultrashort antimicrobial peptides anchored onto soft commercial contact lenses inhibit bacterial adhesion

An instability of the visual correction is sometimes associated with soft hydrophilic contact lenses. However, this problem does not seem to have detracted from the commercial success of this form of refractive aid. To facilitate the quantification of visual performance during soft lens wear, a televised test system was developed and has been fully described elsewhere. Results are now presented of a clinical study using this television (TV) system. Visual performance scores, in conjunction with response latency and blink activity data, were obtained from the eyes of 27 experimentally naive subjects during the first month of adaptation to soft contact lens wear. The results suggest that the soft contact lens wearer has recourse to a strategy whereby he can optimize his level of visual performance when necessary.

To characterise the impact of monofocal soft contact lens (SCL) and bifocal SCLs on refractive error, depth of focus (DoF) and orientation of blur in the peripheral visual field. Monofocal and two bifocal SCLs, Acuvue Bifocal (AVB, Johnson & Johnson) and Misight Dual Focus (DF, CooperVision) with +2.0D add power were modelled using a ray tracing program (ZEMAX) based on their power maps. These SCLs were placed onto the anterior corneal surface of the simulated Atchison myopic eye model to correct for -3.0D spherical refractive error at the fovea. To quantify through-focus retinal image quality, defocus from -3.5D to 1.5D in 0.5D steps was induced at each horizontal eccentricity from 0 to 40° in 10° steps. Wavefront aberrations were computed for each visual eccentricity and defocus. The retinal images were simulated using a custom software program developed in Matlab (The MathWorks) by convolving the point spread function calculated from the aberration with a reference image. The convolved images were spatially filtered to match the spatial resolution limit of each peripheral eccentricity. Retinal image quality was then quantified by the 2-D cross-correlation between the filtered convolved retinal images and the reference image. Peripheral defocus, DoF and orientation of blur were also estimated. In comparison with the monofocal SCL, the bifocal SCLs degraded retinal image quality while DoF was increased at fovea. From 10 to 20°, a relatively small amount of myopic shift (less than 0.3D) was induced by bifocal SCLs compared with monofocal. DoF was also increased with bifocal SCLs at peripheral vision of 10 and 20°. The trend of myopic shift became less consistent at larger eccentricity, where at 30° DF showed a 0.75D myopic shift while AVB showed a 0.2D hyperopic shift and both AVB and DF exhibited large relative hyperopic defocus at 40°. The anisotropy in orientation of blur was found to increase and change its direction through focus beyond central vision. This trend was found to be less dominant with bifocal SCLs compared to monofocal SCL. Bifocal SCLs have a relatively small impact on myopic shift in peripheral refractive error while DoF is increased significantly. We hypothetically suggest that a mechanism underlying myopia control with these bifocal or multifocal contact lenses is an increase in DoF and a decrease in anisotropy of peripheral optical blur.

A table top instrument has been designed, constructed and tested to characterize all of the primary optical and physical properties of contact lenses. Measured optical properties include base power, cylinder power, cylindrical axis, prism, refractive index and wavefront aberrations. Measured physical properties include center thickness, lens diameter and lens sagittal depth. The instrument combines a Shack-Hartmann wavefront sensor (SHWS), a machine vision sensor, and a low coherence light interferometer (LCI) all coaxially aligned into a single tabletop unit. The unit includes a cuvette, mounted in a translatable sample chamber for holding the contact lens under test, and it can be configured to measure wet or dry contact lenses. During operation, the vision sensor measures the diameter of the lens, and locates the center of the lens. The lens is then aligned for other measurements. The vision sensor can also measure various alignment marks on the lens, as well as identify any alpha numerical features, which can be used to associate the lens orientation with the measured aberrations. The LCI measures the center thickness, sagittal depth and index of refraction of the contact lens. The base radius of curvature is then calculated using these measured parameters. The SHWS measures the lenses prescription power, including spherical, cylinder, prism, and higher order wavefront aberrations. NIST traceable calibration artifacts are used to calibrate the SHWS, machine vision and LCI modalities. Repeatability measurements on a contact lens in a saline solution are presented.

Factors influencing the 8-item contact lens dry eye questionnaire score and comparison of translations in Japanese soft contact lens wearers