Linear fitting of biconic surfaces for corneal modeling.

This paper presents a method for reconstructing the corneal surface. The proposed method was tested in 56 healthy and 15 post-orthokeratology corneas. The Medmont E300 Corneal Topographer was used to measure the anterior corneal elevation, and custom MATLAB scripts were employed for data analysis, fitting, and other computational processes. The results obtained were compared with the fitting to an ellipsoid and to a biconic, using an alternative method, showing similarities among the different approaches. Additionally, the advantages of this method and the biconic's generality over the ellipsoid were also demonstrated. In conclusion, the method proposed offers an approach with potential applications in the field of visual and ophthalmic optics related with modeling of the cornea and other optical surfaces.

Optical characterization and through-focus performance of two advanced monofocal intraocular lenses.

PURPOSE: To compare the refractive power profile, subjective depth-of-field and objective optical quality of two advanced monofocal intraocular lenses (IOLs) designed to improve intermediate vision. METHODS: This prospective study evaluated forty-six eyes of twenty-three patients, aged 54-68 years, binocularly implanted with two monofocal enhanced intraocular lenses (IOLs), the Tecnis Eyhance and the Physiol Isopure. Subjective through-focus visual acuity curves were obtained by placing trial lenses in front of the eye while wearing its best spherical-cylindrical correction for distance. Objective optical quality was defined as the area under the modulation transfer function, calculated from the wavefront maps measured with a high-resolution aberrometer. The optical design of both lenses was compared based on their refractive power profiles measured with the lenses immersed in saline solution. RESULTS: Both lenses have progressive aspherical geometries, in which the sagittal power decreases rapidly from the center to the edge of the optical zone. Mean monocular through-focus curves show a best corrected distance visual acuity of - 0.02 logMAR with both lenses. Through-focus visual acuity was marginally higher for the Eyhance, with a difference of 1 letter at the defocus position of - 0.5D and 3 letters between - 1.0D and - 2.0D. Objective assessment of optical quality revealed only a difference of about 2 points in MTF area at distance. CONCLUSION: Both IOLs use a similar approach to improve intermediate vision. The Eyhance showed marginally better subjective performance than the Isopure at the target vergences between - 1.00D and - 2.00D, although these results did not reach statistical significance and were not replicated by the objective findings.

Prevalence of refractive error within a Portuguese sample of optometric records

Purpose: Considering the burden of refractive error, clinical-based research methods are often used as epidemiological tools. This study aimed to generate evidence on the prevalence and distribution of refractive error in Portugal. Methods A cross-sectional retrospective study was designed to review optometric records from Portuguese practices during July 2021. Results 348 optometric records were analysed. Subjects had a mean age of 44.2 ± 19.2 years (range 6–81) and 58.4% were female. The mean spherical equivalent was myopic, −0.65 ± 2.38 Diopters (D), varying from a minimum of −13.63 to a maximum of 6.25 D. According to sex, the mean spherical equivalent was −0.76 ± 2.29 D for female and −0.49 ± 2.49 D for male, with no significant difference between them (p = .307). The distribution of the spherical equivalent mean across the age groups, linearly varies from a myopic −1.62 ± 1.74 D in the age group of [6 – 29]; −1.58 ± 2.80 D in [30 – 44]; −0.09 ± 2.40 in [45 – 59] to a hyperopic 0.67 ± 1.61 D in the group of [60 – 81]. High myopia had a prevalence of 2.7% in the sample. Myopia was the most prevalent refractive error in the sample representing 41.3%. In the age group [6–29], myopia had a prevalence of 69.3%. Hyperopia had a prevalence in the sample of 29.7%. Conclusions Myopia represents the most prevalent refractive error within the sample and is the prevalence is higher in the younger age groups, demonstrating a shift towards an increase of myopia in the next years. (AU)

Prevalence of refractive error in Portugal – A systematic review and meta-analysis

Purpose The aim of this study was to systematically review and meta-analyse epidemiological data of refractive error prevalence in Portugal. Methods A structured search strategy and systematic literature review was applied to multiple databases, such as MEDLINE/PubMed, Web of Science, Scopus, Google Scholar, official organizations and academic repositorium's, to identify all relevant epidemiological studies in Portugal until February 2021. The outcome measure was the prevalence of refractive error among the Portuguese population. The events and sample size were entered as raw data and the effect size parameters were computed by Comprehensive Meta-Analysis Software. Results A total of 9 studies were pooled for the meta-analysis. The fixed effects model points to an estimated effect size of 43% (95% CI: 41.9–44.1%). However, the statistics of heterogeneity (Q-value p < 0.001; I-squared =99.344) showed very high heterogeneity among studies and recommends using a random-effects model. The random effects model points to an estimated effect size of 31.9% (95% CI: 19.8–47.0%) prevalence of refractive error in the Portuguese population. Conclusions A prevalence of refractive error in Portugal of 31.9% (95% CI: 20.0–47.0%) can be considered as a conservative approach to the real burden of this condition. However, it translates into at least 2 to 4.5 million Portuguese individuals with a refractive error. The high heterogeneity between studies, the wide estimate and the random effects involved demonstrate the need for more studies and consistent sources to obtain narrower estimates. (AU)

Analysis of Wavefront Data Obtained With a Pyramidal Sensor in Pseudophakic Eyes Implanted With Diffractive Intraocular Lenses.

PURPOSE: To investigate the clinical validity of using wavefront measurements obtained with a recently available pyramidal aberrometer to assess the optical quality of eyes implanted with diffractive intraocular lenses (IOLs). METHODS: Individual biometric data were used to create models of pseudophakic eyes implanted with two diffractive IOLs. Their synthetic wavefronts were calculated by ray-tracing with near infrared wavelength (0.85 µm). Comparisons of the through-focus visual acuity of 12 pseudophakic eyes were obtained with three different methods: clinical defocus curves; simulated defocus curves calculated from ray-tracing in the customized model eyes; and through-focus simulated defocus curves calculated from the wavefront data measured with a pyramidal aberrometer. RESULTS: Image quality calculated from wavefront data obtained by ray-tracing with 0.85 µm wavelength, without scaling the phase to 0.55 µm, resulted in a significantly different through-focus curve compared to the reference values. Even so, after scaling of the wavefront data to 0.55 µm, the defocus curves calculated from the wavefronts measured with the pyramidal aberrometer did not match the shape and the depth of field of the clinical defocus curves or the theoretical expected values. CONCLUSIONS: Correcting for the longitudinal chromatic aberration of the eye when measuring the wavefront of eyes implanted with diffractive IOLs under near infrared light only accounts for the best focus shift due to the longitudinal chromatic aberration, but not for the wavelength dependence of the diffractive element. The pyramidal sensor does not seem to properly sample the slopes of a wavefront measured from a pseudophakic eye implanted with a presbyopia-correcting diffractive IOL to a clinically acceptable level. [J Refract Surg. 2023;39(7):438-444.].

Neural binocular summation and the effect of defocus on the pattern electroretinogram and visual evoked potentials for different pupil sizes.

PURPOSE: To evaluate the influence of defocus and pupil size on subjective (visual acuity [VA]) and objective (electrophysiology) descriptors of human vision and their effect on binocular visual performance by means of neural binocular summation (BS). METHODS: Fifteen healthy young subjects were recruited in this crossover study. Pattern electroretinogram (PERG) and visual evoked potentials (VEP) were measured under two levels of positive (+1.5 and +3.0 D) spherical and astigmatic defocus (axis 90°). Pupil size was controlled to reduce the inter-individual variability factor. RESULTS: Low- and high-contrast VA showed poorer visual performance in the monocular versus the binocular condition. Positive BS (for VA) was higher with greater pupil size and higher levels of defocus. In the visual electrophysiology tests (i.e., VEP and PERG), peak time and amplitude were affected by pupil size and defocus. The increase in peak time was larger and the reduction in amplitude was more significant with greater levels of defocus and smaller pupil sizes. For the VEP, positive BS was found in all conditions, being stronger with larger amounts of defocus and pupil size (for the P100 amplitude). Significant negative correlations were observed between the P100 amplitude and VA BSs. CONCLUSION: Smaller pupil size and levels of defocus produced greater changes in cortical activity as evidenced by both the PERG and VEP. Considering these changes and the obtained positive BS, the mechanism could be initiated as early as the retinal processing stage, then being modulated and enhanced along the visual pathway and within the visual cortex.

Prevalence of refractive error within a Portuguese sample of optometric records.

PURPOSE: Considering the burden of refractive error, clinical-based research methods are often used as epidemiological tools. This study aimed to generate evidence on the prevalence and distribution of refractive error in Portugal. METHODS: A cross-sectional retrospective study was designed to review optometric records from Portuguese practices during July 2021. RESULTS: 348 optometric records were analysed. Subjects had a mean age of 44.2 ± 19.2 years (range 6-81) and 58.4% were female. The mean spherical equivalent was myopic, -0.65 ± 2.38 Diopters (D), varying from a minimum of -13.63 to a maximum of 6.25 D. According to sex, the mean spherical equivalent was -0.76 ± 2.29 D for female and -0.49 ± 2.49 D for male, with no significant difference between them (p = .307). The distribution of the spherical equivalent mean across the age groups, linearly varies from a myopic -1.62 ± 1.74 D in the age group of [6 - 29]; -1.58 ± 2.80 D in [30 - 44]; -0.09 ± 2.40 in [45 - 59] to a hyperopic 0.67 ± 1.61 D in the group of [60 - 81]. High myopia had a prevalence of 2.7% in the sample. Myopia was the most prevalent refractive error in the sample representing 41.3%. In the age group [6-29], myopia had a prevalence of 69.3%. Hyperopia had a prevalence in the sample of 29.7%. CONCLUSIONS: Myopia represents the most prevalent refractive error within the sample and is the prevalence is higher in the younger age groups, demonstrating a shift towards an increase of myopia in the next years.

Prevalence of refractive error in Portugal estimated from ophthalmic lens manufacturing data: Ten-years analysis.

PURPOSE: To investigate the prevalence, distribution and trends of refractive error from ophthalmic lens manufacturing data over a ten-year period. METHODS: Fully anonymized data from ophthalmic lenses, for the years between 2010 and 2020, provided by the leading ophthalmic lens manufacturer operating in Portugal were analysed (no human participants were involved in the research). Prescriptions delivered were divided in single vision prescriptions and progressive/multifocal prescriptions and categorized into 14 spherical equivalent ranges. Given the lack of absolute values, indirect estimates and a qualitative analysis of the current situation and trends on refractive error epidemiology was carried out. RESULTS: Dataset from manufacturer comprises percentage values of ophthalmic lenses dispensed in Portugal. The distribution of ophthalmic prescriptions for single vision prescriptions presents most of the observations in the range [-1.49, -0.50] diopters, in every year from 2010 to 2020. For the progressive prescription's lenses, most of the observations is in an interval of two ranges, [0.50, 1.49] and [1.50, 2.99] diopters. From 2010 to 2020 the proportion of single vision ophthalmic lens prescriptions for myopia increased from 38.13% to 46.21%; the proportion for high myopia increased from 2.76% to 4.45%; and the proportion for hyperopia decreased from 40.85% to 31.36%. CONCLUSIONS: Ophthalmic lens manufacturing data can be a valuable source for long-term analysis of refractive error prescription and trends over time. It was possible to observe a trend of increasing prevalence of myopia and high myopia from 40.89% in 2010 to 50.66% in 2020. That increase trend has important implications for public health and in the planning of services.

Changes in visual function and optical and tear film quality in computer users.

PURPOSE: To assess changes in visual function and optical and tear film quality in computer users. METHODS: Forty computer workers and 40 controls were evaluated at the beginning and end of a working day. Symptoms were assessed using the Quality of Vision questionnaire (QoV), 5-item Dry Eye Questionnaire (DEQ-5) and Symptom Assessment in Dry Eye version II (SANDE II). Tear film quality was evaluated using the Medmont E300 dynamic corneal topography tool to measure the tear film surface quality (TFSQ), TFSQ area and auto tear break-up time (TBUT). Optical quality was assessed by measuring high, low and total ocular aberrations with a Hartmann-Shack wavefront sensor. Visual performance was assessed by measuring photopic and mesopic visual acuity, photopic and mesopic contrast sensitivity and light disturbance. RESULTS: Poorer DEQ-5, QoV and SANDE II scores were obtained in computer workers at the end of the working day compared with controls (p ≤ 0.02). Computer workers exhibited a higher (worse) TFSQ and TFSQ area at visit 2 compared with visit 1 (p ≤ 0.04), while no significant differences in TBUT (p = 0.19) or ocular aberrations were observed (p ≥ 0.09). Additionally, both light disturbance (p ≤ 0.04) and mesopic and photopic contrast sensitivity worsened at several spatial frequencies (p ≤ 0.04) throughout the working day in computer workers, while visual acuity remained unchanged (p ≥ 0.07). In contrast, control subjects exhibited no decrease in any variable during the day. CONCLUSIONS: While visual acuity remained unchanged, several aspects of visual function and quality of vision decreased over a day of computer use. These changes were accompanied by greater dry eye symptoms and tear film changes, which are likely to have played a fundamental role. The present study provides insight into new metrics to assess digital eye strain.

Peripheral Refraction and Visual Function of Novel Perifocal Ophthalmic Lens for the Control of Myopia Progression.

This study aimed to evaluate the peripheral defocus induced with a novel perifocal ophthalmic lens for myopia progression control and the potential impact on visual function. This experimental, non-dispensing crossover study evaluated 17 myopic young adults. The peripheral refraction was measured using an open-field autorefractor, at 2.50 m from the target point, in two eccentric points, 25° temporal, 25° nasal, and central vision. Visual contrast sensitivity (VCS) was measured at 3.00 m with a Vistech system VCTS 6500 in low light conditions. Light disturbance (LD) was assessed with a light distortion analyzer 2.00 m away from the device. Peripheral refraction, VCS, and LD were assessed with a monofocal lens and perifocal lens (with an add power of +2.50 D on the temporal side of the lens, and +2.00 D on the nasal side). The results showed that the perifocal lenses induced an average myopic defocus of -0.42 ± 0.38 D (p-value < 0.001) in the nasal retina, at 25° The changes induced by the lower add power in the nasal part of the lens did not induce statistically significant changes in the refraction of the temporal retina. The VCS and LD showed no significant differences between the monofocal and perifocal lenses.

Assessment of meibomian gland drop-out and visibility through a new quantitative method in scleral lens wearers: A one-year follow-up study.

OBJECTIVES: To validate a previously developed algorithm based on the visibility of meibomian gland images obtained with Cobra fundus camera and to assess the changes in meibomian glands in scleral lens wearers over one year of lens wear. METHODS: Infrared meibography was obtained from the upper eyelid using the Cobra fundus camera in forty-three volunteers (34.2 ± 10.1 years). Meibographies were classified into 3 groups: Group 1 = good subjective gland visibility and gland drop-out < 1/3 of the total area; Group 2 = low visibility and gland drop-out < 1/3; and Group 3 = low visibility and gland drop-out > 1/3. Meibomian gland visibility metrics were then calculated using the developed algorithm from the pixel intensity values of meibographies. Repeatability of new metrics and their correlations with gland drop-out were assessed. Meibographies and ocular symptoms were also assessed after 1 year of scleral lens wear in 29 subjects. RESULTS: Gland drop-out percentage was not statistically different between groups 1 and 2 (p = 0.464). Nevertheless, group 1 showed higher grey pixel intensity values than the other groups. Statistically significant correlations were found between gland visibility metrics and gland drop-out percentage. Repeatability was acceptable for all metrics, coefficient of variation achieving values between 0.52 and 3.18. While ocular symptoms decreased with scleral lens wear (p < 0.001), no statistically significant differences were found in gland drop-out percentage (p = 0.157) and gland visibility metrics (p > 0.217). CONCLUSIONS: The proposed method can assess meibomian gland visibility in an objective and repeatable way. Scleral lens wear appears to not adversely affect meibomian gland drop-out and visibility while might improve dry eye symptoms after one year of lens wear. These preliminary results should be confirmed with a control group.

Pupil size effect on binocular summation for visual acuity and light disturbance.

PURPOSE: Smaller pupil size under binocular conditions could justify partially the improvement of visual performance when compared to monocular conditions. The purpose of this study was to assess the binocular summation for increasing levels of spherical and cylindrical defocus when the pupil size factor is ruled out as a confounding factor. METHODS: Fifteen young subjects were recruited in this crossover study. Light disturbance index (LDI) was evaluated with the light disturbance analyzer and low (LCDVA) and high (HCDVA) contrast visual acuity with the ETDRS test. Two positive spherical and cylindrical defocus levels (+ 1.5 and + 3.0 D) were used to induce a controlled degradation of the retinal image for two pupil sizes (3 and 5 mm). RESULTS: Our results showed poorer visual performance in monocular than the binocular condition. An increasing deterioration was observed with the level of spherical defocus. Positive binocular summation for visual acuity was found in all the parameters studied and was stronger under larger pupil size and for higher levels of spherical defocus. It was observed a positive binocular summation for the LDI under all the conditions studied. Strong and significant correlations were found between LDI and LCDVA and between LDI and HCDVA for all the conditions. Higher correlations were obtained between disturbance index and visual acuity for spherical defocus compared to cylindrical. CONCLUSION: Binocular summation was observed under different conditions of spherical and cylindrical optical degradation of the image quality when the pupil size was fully controlled. This suggests that a neural factor is involved.

Prevalence of refractive error in Portugal - A systematic review and meta-analysis.

PURPOSE: The aim of this study was to systematically review and meta-analyse epidemiological data of refractive error prevalence in Portugal. METHODS: A structured search strategy and systematic literature review was applied to multiple databases, such as MEDLINE/PubMed, Web of Science, Scopus, Google Scholar, official organizations and academic repositorium's, to identify all relevant epidemiological studies in Portugal until February 2021. The outcome measure was the prevalence of refractive error among the Portuguese population. The events and sample size were entered as raw data and the effect size parameters were computed by Comprehensive Meta-Analysis Software. RESULTS: A total of 9 studies were pooled for the meta-analysis. The fixed effects model points to an estimated effect size of 43% (95% CI: 41.9-44.1%). However, the statistics of heterogeneity (Q-value p < 0.001; I-squared =99.344) showed very high heterogeneity among studies and recommends using a random-effects model. The random effects model points to an estimated effect size of 31.9% (95% CI: 19.8-47.0%) prevalence of refractive error in the Portuguese population. CONCLUSIONS: A prevalence of refractive error in Portugal of 31.9% (95% CI: 20.0-47.0%) can be considered as a conservative approach to the real burden of this condition. However, it translates into at least 2 to 4.5 million Portuguese individuals with a refractive error. The high heterogeneity between studies, the wide estimate and the random effects involved demonstrate the need for more studies and consistent sources to obtain narrower estimates.

Changes in Light Disturbance Analyzer Evaluation in SMILE for High Myopia and Astigmatism.

PURPOSE: To study the objective change in light disturbance around a glare source using the Light Disturbance Analyzer (LDA) (Binarytarget Lda) and correlate this with the validated subjective quality of vision (QoV) questionnaire in small incision lenticule extraction (SMILE) for high compound myopic astigmatism. METHODS: This was a prospective study recruiting 114 patients undergoing SMILE with attempted spherical equivalent refraction (SEQ) correction from -9.00 to -13.00 diopters (D), and cylinder up to 5.00 D. The LDA was used before and 3 and 12 months after surgery to evaluate the Light Disturbance Area, Light Disturbance Index, Best Fit Circle Radius, and Best Fit Circle Irregularity. Patients completed the Rasch-validated QoV questionnaire before and 12 months after surgery. Correlation analysis was performed between the LDA parameters and the QoV frequency, severity, and bothersomeness for halos and starbursts. RESULTS: At 12 months, there was a non-statistically signifcant change of 11.9% for Light Disturbance Area and Light Disturbance Index and 6.5% for Best Fit Circle Radius. There was an increase of 81.9% for Best Fit Circle Irregularity (P = .017). Light Disturbance Area, Light Disturbance Index, and Best Fit Circle Radius correlated with bothersomeness for QoV halos, and with frequency, severity and bothersomeness for QoV star-bursts (P < .05), albeit with a low correlation coefficient (R2 < 0.13). There was no correlation between increase in Best Fit Circle Irregularity and the halo and starburst scores from the QoV questionnaire. CONCLUSIONS: LDA Best Fit Circle Irregularity was found to increase following high myopic SMILE. Other LDA parameters appeared to increase, but a much larger sample would be required to find statistical significance. The change in LDA parameters was only weakly correlated with QoV halo and starburst metrics, representing the wide variation in inter-subject perception. [J Refract Surg. 2022;38(11):725-732.].

Short-term tear film stability, optical quality and visual performance in two dual-focus contact lenses for myopia control with different optical designs.

PURPOSE: To assess and compare short-term visual and optical quality and tear film stability between two dual-focus (DF) prototype myopia control contact lenses (CLs) having different inner zone diameters. METHODS: Twenty-eight myopic subjects were included in this randomised, double-masked crossover study. Refraction, best-corrected visual acuity (VA) and tear film stability were measured at baseline (i.e., when uncorrected). Subjects were then binocularly fitted with the DF CLs, with only the sensorial dominant eye being assessed. Lenses were of the same material and had inner zone diameters of either 2.1 mm (S design) or 4.0 mm (M design). Visual and physical short-term lens comfort, over-refraction, best-corrected VA, stereopsis at 40 cm, best-corrected photopic and mesopic contrast sensitivity (CS), size and shape of light disturbance (LD), wavefront aberrations, subjective quality of vision (QoV Questionnaire) and tear film stability were measured for each lens. RESULTS: Both CL designs decreased tear film stability compared with baseline (p < 0.05). VA and photopic CS were within normal values for the subjects' age with each CL. When comparing lenses, the M design promoted better photopic CS for the 18 cycles per degree spatial frequency (p < 0.001) and better LD (p < 0.02). However, higher-order aberrations were improved with the S design (p = 0.02). No significant difference between the two CLs was found for QoV scores and tear film stability. CONCLUSIONS: Both DF CLs provided acceptable visual performance under photopic conditions. The 4.0 mm inner zone gave better contrast sensitivity at high frequencies and lower light disturbance, while the 2.1 mm central diameter induced fewer higher-order aberrations for a 5 mm pupil diameter. Both CLs produced the same subjective visual short-term lens comfort.

Increase in b-wave amplitude after light stimulation of the blind spot is positively correlated with the axial length of myopic individuals.

Altered retinal dopamine and ON-pathway activity may underlie myopia development. It has been shown that the stimulation of the blind spot with short-wavelength light increases the electroretinogram (ERG) b-wave amplitude of myopic eyes and may engage the retinal dopaminergic system. This study evaluated the impact of various durations of blind spot stimulation on the electrophysiological response of the myopic retina and their relationship to axial length. Six myopic individuals underwent three short-wavelength blue light blind spot stimulation protocols (10 s, 1 min, 10 min) using a virtual reality headset. As a control condition, no stimulation was shown for 1 min. The b-wave amplitude of the photopic full-field ERG was measured at baseline and 10, 20, 30, 40, 50, and 60 min after each condition. A significant increase in b-wave amplitude was observed for all stimulation protocols compared to the control. The peak b-wave amplitude was observed 20 min after the 1-min stimulation protocol and 60 min after the 10-min stimulation protocol. A significant positive correlation was found between axial length of the eye and percent change in b-wave amplitude for the 10-min stimulation protocol. A rapid and a delayed b-wave time course responses were observed following 1 min and 10 min of blind spot stimulation, respectively. Overall, these results indicate that light stimulation of the blind spot for various durations elevates ON-bipolar cell activity in the retina and as such is assumed to reduce the myopic response. These findings could have implications for future myopia treatment.

Tear film stability over a myopia control contact lens compared to a monofocal design.

Clinical relevance: Tear film assessment is essential in contact lens wearers and it can improve the success rates of the fitting.Background: To compare the short-term effect of two contact lenses on pre-lens tear film stability and comfort: dual-focus contact lens (MiSight) and a monofocal contact lens (Proclear 1-day).Methods: This randomised, double-masked, crossover study was performed in twenty-eight healthy, myopic volunteers aged between 18 and 32 years (23.5 ± 4.1 years). Only one randomly chosen eye was assessed. Distance vision and refraction were evaluated at baseline. Each contact lens type (monofocal and dual-focus) was randomly fitted, always in both eyes. A visual analogue scale between 0 and 10 was used to assess general comfort, physical comfort, and visual comfort. Tear Film Surface Quality (TFSQ) index, TFSQ_area and auto Tear Break-Up Time were obtained using Medmont E-300 at baseline (naked eye condition) and 25 minutes after each contact lens insertion.Results: Refractive sphere and cylinder were, respectively, -1.36 ± 1.04 D (ranging from -6.00 to -0.25 D) and -0.23 ± 0.30 D (ranging from -0.75 to 0.00 D). TFSQ and TFSQ area were lower (meaning more stable tear film) at baseline when compared with both contact lens types (p < 0.025). Higher pre-lens tear instability (larger TFSQ and_TFSQ area values) was found with the dual-focus than the monofocal lens. Auto Tear Break-Up Time was higher at baseline than with each of the contact lenses, without statistically significant differences between both contact lens types. Visual analogue scales revealed statistically significant better scores in the monofocal contact lens than in dual-focus contact lens for general (0.77 ± 1.14 vs 3.12 ± 2.79), physical (0.96 ± 1.46 vs 2.19 ± 2.45) and visual comfort (1.27 ± 1.66 vs 3.92 ± 2.04).Conclusion: A slight reduction in short-term pre-lens tear film stability was found in the dual-focus design in comparison with the monofocal lens, potentially contributing to the deterioration of visual performance and comfort during dual-focus contact lens wear.

Peripheral refraction of myopic eyes with spectacle lenses correction and lens free emmetropes during accommodation.

PURPOSE: To measure axial and off-axis refraction patterns in myopic eyes with spectacle lenses correction and lens free emmetropes in young healthy subjects at different target distances from 2.00 m (0.50 D) to 0.20 m (5.00 D) in terms of sphere, astigmatism, and spherical equivalent refraction. METHODS: Refraction was measured at the center, 20 and 40 degrees from the line of sight both nasally and temporally in 15 emmetropic and 25 myopic young healthy subjects with an open field, binocular, infrared autorefractor (Grand Seiko WAM-5500, Hiroshima, Japan). Fixation target was a Maltese cross set at 2.00, 0.50, 0.33 and 0.20 m from the corneal plane. Changes in off-axis refraction with accommodation level were normalized with respect to distance axial values and compared between myopic eyes with spectacle lenses correction and lens free emmetropes. RESULTS: Off-axis refraction in myopic eyes with spectacle lenses correction was significantly more myopic in the temporal retina compared to lens free emmetropes except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared to axial refraction particularly in the myopic group. This change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20 m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target. CONCLUSION: Accommodation to very near targets (up to 0.20 m) makes the off-axis refraction of myopes wearing their spectacle correction similar to that of lens free emmetropes. A significant reduction in off-axis astigmatism was also observed for the 0.20 m distance.

Blue light blind-spot stimulation upregulates b-wave and pattern ERG activity in myopes.

Upregulation of retinal dopaminergic activity may be a target treatment for myopia progression. This study aimed to explore the viability of inducing changes in retinal electrical activity with short-wavelength light targeting melanopsin-expressing retinal ganglion cells (ipRGCs) passing through the optic nerve head. Fifteen healthy non-myopic or myopic young adults were recruited and underwent stimulation with blue light using a virtual reality headset device. Amplitudes and implicit times from photopic 3.0 b-wave and pattern electroretinogram (PERG) were measured at baseline and 10 and 20 min after stimulation. Relative changes were compared between non-myopes and myopes. The ERG b-wave amplitude was significantly larger 20 min after blind-spot stimulation compared to baseline (p < 0.001) and 10 min (p < 0.001) post-stimulation. PERG amplitude P50-N95 also showed a significant main effect for 'Time after stimulation' (p < 0.050). Implicit times showed no differences following blind-spot stimulation. PERG and b-wave changes after blind-spot stimulation were stronger in myopes than non-myopes. It is possible to induce significant changes in retinal electrical activity by stimulating ipRGCs axons at the optic nerve head with blue light. The results suggest that the changes in retinal electrical activity are located at the inner plexiform layer and are likely to involve the dopaminergic system.

Comparison of short-term light disturbance, optical and visual performance outcomes between a myopia control contact lens and a single-vision contact lens.

PURPOSE: To compare the optical and visual performance of a dual-focus (DF) contact lens used for myopia control with a single-vision (SV) contact lens of the same material. METHODS: A randomised, double-masked crossover study. Twenty-eight healthy, myopic volunteers between 18 and 32 years of age (23.49 ± 4.07 years) participated in this study. The sensory dominant eye for distance vision was determined. Refraction, best-corrected visual acuity (VA) and aberrations for 3 mm and 5 mm pupil diameters were quantified without a contact lens in situ. Subjects were fitted with two contact lens designs: DF and SV, both made of omafilcon A material. The Quality of Vision (QoV) questionnaire, over-refraction, best-corrected VA, stereopsis at 40 cm, best-corrected photopic and mesopic contrast sensitivity, light disturbance and aberrations were assessed 25 min after contact lens insertion. RESULTS: There were no statistically significant differences in best-corrected VA and stereopsis between the baseline, DF and SV conditions. Photopic and mesopic contrast sensitivity were lower for the DF contact lens at all frequencies, with the exception of the mesopic contrast sensitivity at 18 cycles per degree (p = 0.23). Higher order aberrations and light disturbance size and irregularity were higher for the DF contact lens (p < 0.001). No differences were found in higher order aberrations between baseline and the SV contact lens condition for each pupil diameter. QoV scores also revealed lower frequency, severity and bothersome scores with the SV contact lens than with the DF contact lens (p < 0.001). CONCLUSIONS: The DF contact lens design decreased the psychophysical and psychometric visual quality scores in the short-term under dim-light conditions when compared with a single-vision contact lens design of the same material. VA and stereopsis were unaffected by the lens design.