Mesopic Illumination Research Articles

Degradation of Photopic and Mesopic Contrast Sensitivity Function in High Myopes With Partial Posterior Vitreous Detachment.

The purpose of this study was to evaluate the effects of posterior vitreous detachment (PVD) on visual quality in patients with high myopia, as well as investigate the associated factors of photopic and mesopic contrast sensitivity function (CSF) in high myopia. Visual quality was comprehensively assessed in patients with high myopia. Visual acuity, contrast sensitivity (CS) at four spatial frequencies (3, 6, 12, and 18 cycles per degree [c.p.d.]) under photopic and mesopic conditions, as well as the modulation transfer function cutoff value (MTFcutoff), the objective scatter index (OSI), the Strehl ratio (SR), and internal aberrations, were measured in this cross-sectional study. This study included 94 eyes from 47 subjects with bilateral high myopia, including 23 eyes with complete PVD (cPVD), 21 eyes with partial PVD (pPVD), and 50 eyes without PVD (nPVD). There was no significant difference in visual quality between the cPVD group and the nPVD group. Whereas in eyes with pPVD, there was a degradation of overall photopic CSF (versus nPVD, P = 0.048), photopic CS at 3 c.p.d. (versus cPVD, P = 0.009 and versus nPVD, P = 0.032), photopic CS at 18 c.p.d. (versus nPVD, P = 0.033), overall mesopic CSF (versus nPVD, P = 0.033), and secondary astigmatism (versus cPVD, P = 0.044). Under photopic conditions, the factors affecting CSF were pPVD and SR, whereas the factors affecting mesopic CSF were pPVD, OSI, and ganglion cell-inner plexiform layer thickness. The pPVD impaired visual quality in patients with high myopia compared to nPVD or cPVD, and pPVD could be a factor explaining CSF at both photopic and mesopic illumination. Clinicians need to closely monitor patients with high myopia with pPVD due to the potential decline in visual quality and the development of vitreoretinal disorders.

Analysis of the effects of FineVision Micro F and AcySof IQ PanOptix intraocular lenses on visual quality under different lighting condition

Aims/Purpose: To analyse the effect of the design of FineVision Micro F and AcrySof IQ PanOptix trifocal intraocular lenses on the visual quality of patients under photopic and mesopic illumination conditions.Methods: Observational, prospective, cross‐sectional study. The study was conducted at the Hospital Universitario Sanitas la Moraleja in Madrid. The study followed the principles of the Declaration of Helsinki. The sample included 16 patients who underwent cataract or lensectomy surgery, with bilateral implantation of one of the two intraocular lenses (IOLs) under study: 20 eyes with FineVision Micro F implant and 12 eyes with AcrySof IQ PanOptix. After 30 days after surgery, an assessment of photopic and mesopic, monocular and binocular visual acuity (VA) was performed for three distances: far (4 m), intermediate (66 cm) and near (40 cm) with the ETDRS test. A p‐value <0.05 was considered a criterion for statistical significance.Results: Visual acuity analysis showed significant differences between FineVision Micro F and AcrySof IQ PanOptix lenses, under photopic conditions, for intermediate distance (p‐value 0.014) with means of 0.04 ± 0.05 and 0.11 ± 0.11, respectively and near distance (p‐value 0.001), with means of 0.05 ± 0.06 and 0.12 ± 0.06, respectively. On the other hand, in mesopic conditions, statistically significant differences (p‐value 0.032) were observed in close distance, with means of 0.43 ± 0.3 and 0.52 ± 0.2, respectively.Conclusions: Both FineVision Micro F and AcrySof IQ PanOptix IOL designs provide optimal VA at far distances in both photopic and mesopic illumination conditions. The FineVision Micro F IOL provides better intermediate and near VA in photopic conditions and near distance in mesopic conditions than the AcrySof IQ PanOptix IOL, and this difference is clinically significant.

Comparison of quality of life with two trifocal intraocular lenses under different lighting conditions

Aims/Purpose: To evaluate the effect of two types of trifocal intraocular lenses on the visual quality of patients undergoing cataract surgery by assessing contrast sensitivity, halo perception and subjective visual satisfaction under photopic and mesopic lighting conditions.Methods: Observational, prospective, cross‐sectional study. The study was conducted at the Hospital Universitario Sanitas la Moraleja in Madrid. The study followed the principles of the Declaration of Helsinki. The sample included 16 cataract or lensectomy patients with bilateral implantation of one of the two intraocular lenses (IOL) under study: 20 eyes implanted with FineVision and 12 eyes implanted with PanOptix. After 30 days after surgery, contrast sensitivity was measured with the CSV‐1000 test (2.5 metres) for four spatial frequencies (3, 6, 12 and 18 c/g), halo perception was assessed with the Halo.V.1 software and finally quality of life was assessed with the VF‐14 questionnaire. A p‐value < 0.05 was considered a criterion for statistical significance.Results: Analysis of contrast sensitivity under photopic conditions showed significant differences greater for the FineVision lens of 0.15 log units at 3 c/g and 12 c/g frequencies between the two lenses under photopic illumination conditions (p‐value 0.034). However, there were no statistically significant differences in mesopic illumination conditions. Furthermore, there was no statistically significant difference when purchasing the perception of halos, with a p‐value (0.149). On the other hand, patients' subjective perception of quality of life scored worse in night vision (p‐value 0.023) and near vision (p‐value 0.046) when comparing the PanOptix lens and the FineVision.Conclusions: The FineVision IOL lens provides better contrast sensitivity in photopic illumination conditions than the PanOptix. However, in mesopic conditions, both IOL designs provide similar contrast sensitivity values for the far distance. On the other hand, although the lenses did not show statistically significant differences in halo perception, the FineVision shows better vision satisfaction results during night driving than the PanOptix.

Effect of the spectral power distribution on visual performance of subjects implanted with intraocular lenses with or without a blue light-filter under night-driving conditions

In old subjects, the effect on visual performance of the interaction between the spectral power distribution of street lamps and the different types of intraocular lenses (IOLs) is unknown. Contrast threshold (CT) and reaction time (RT) were analysed in off-axis vision at mesopic illumination conditions provided by high-pressure sodium and metal-halide lamps, using a Maxwellian view optical system. Four groups of subjects participated: 10 young subjects, 20 elderly subjects with cataracts and the same subjects after cataract surgery were divided into two groups, 10 subjects implanted with a blue light-filtering and 10 subjects with a non-blue light-filtering IOL (NBIOL). Age-related cataract impairs detection and reaction capabilities; tasks that are nevertheless improved after surgery. The type of lamp does not affect both tasks in the case of the blue light-filtering IOL group, but it does in the NBIOL group. When comparing the two lenses, no detrimental effect of the blue light filter is observed in both tasks. In conclusion, at representative night-driving conditions, the spectral power distribution of the street lamp does not have a clinically relevant effect on visual tasks such as CT and visual RT in pseudophakic subjects, regardless of the type of IOL implanted.

Refractive changes and visual quality in patients with corneal edema after cataract surgery

BackgroundTo assess visual quality and stabilization of refractive changes in corneal edema patients after cataract surgery, using visual acuity (VA) and contrast sensitivity measurements.MethodsSixty-one eyes were analysed, twenty-three with and thirty-eight without corneal edema. Uncorrected and corrected distance VA (UDVA and CDVA) were determined with an EDTRS chart, the contrast sensitivity function (CSF) under photopic and mesopic illumination conditions with a CVS-1000e chart, clinical refraction, and corneal topography. Measurements were taken preoperatively, 1–2 days, 1 and 3-months after surgery. Clinical refraction was converted to vector notation (M, J0, J45) and SPSS v26.0 was used for data analysis.ResultsAn improvement of VA was observed through the postoperative period; changes between visits were significant for CDVA in both groups and for UDVA in the edema sample. Significant astigmatic changes (J0,J45) between visits were not observed, but M values showed a hyperopic tendency in the edema group and a myopic shift in the control group that did not change between visits, with statistically significant differences between groups. Controls had significantly better contrast sensitivity at high spatial frequencies. Under mesopic conditions, global contrast sensitivity losses were observed in the edema group, which improved between visits in the middle frequency range.ConclusionCorneal edema patients had a significant reduction of CDVA, and frequency-selective sensitivity losses that evidence a visual quality loss. Clinical refraction may improve visual quality, but in edema patients these losses are related to corneal changes, which did not change at three months after surgery.

Spectral dependency of the human pupillary light reflex. Influences of pre-adaptation and chronotype.

Non-visual photoreceptors (ipRGCs) and rods both exert a strong influence on the human pupil, yet pupil models regularly use cone-derived sensitivity as their basis. This inconsistency is further exacerbated by the fact that circadian effects can modulate the wavelength sensitivity. We assessed the pupillary reaction to narrowband light stimuli in the mesopic range. Pupil size for eighty-three healthy participants with normal color vision was measured in nine experimental protocols with varying series of continuous or discontinuous light stimuli under Ganzfeld conditions, presented after 90 seconds of dark adaptation. One hundred and fifty series of stimulation were conducted across three experiments, and were analyzed for wavelength-dependency on the normalized pupillary constriction (nPC), conditional on experimental settings and individual traits. Traits were surveyed by questionnaire; color vision was tested by Ishihara plates or the Lanthony D15 test. Data were analyzed with generalized additive mixed models (GAMM). The normalized pupillary constriction response is consistent with L+M-cone derived sensitivity when the series of light stimuli is continuous, i.e., is not interrupted by periods of darkness, but not otherwise. The results also show that a mesopic illuminance weighing led to an overall best prediction of pupillary constriction compared to other types of illuminance measures. IpRGC influence on nPC is not readily apparent from the results. When we explored the interaction of chronotype and time of day on the wavelength dependency, differences consistent with ipRGC influence became apparent. The models indicate that subjects of differing chronotype show a heightened or lowered sensitivity to short wavelengths, depending on their time of preference. IpRGC influence is also seen in the post-illumination pupil reflex if the prior light-stimulus duration is one second. However, shorter wavelengths than expected become more important if the light-stimulus duration is fifteen or thirty seconds. The influence of sex on nPC was present, but showed no interaction with wavelength. Our results help to define the conditions, under which the different wavelength sensitivities in the literature hold up for narrowband light settings. The chronotype effect might signify a mechanism for strengthening the individual´s chronotype. It could also be the result of the participant’s prior exposure to light (light history). Our explorative findings for this effect demand replication in a controlled study.

Design and validation of a chart-based measure of the limits of spatial contrast sensitivity.

Current chart-based tests of spatial contrast sensitivity (SCS) with fixed or narrow frequency ranges (≤18cycles/°) cannot characterise the limits of spatial contrast vision. Here we present the design and validation of a chart-based measure of the spatial contrast envelope. Following the principles of the standard visual acuity (Bailey-Lovie) and contrast sensitivity (Pelli-Robson) charts, a combined spatial-contrast and visual acuity chart was designed using a language-independent triangular symbol for a four-alternative forced-choice procedure plus chart rotation. Symbol frequencies ranged between 0.38 and 60cycles/° spaced along 10radial axes (0.55%-100% contrast). The chart was validated with reference to the Bailey-Lovie and Pelli-Robson charts; its reliability and sensitivity to changes in illumination, simulated cataract and blur was evaluated in healthy adults. The photopic SCS function could be measured in 5.5±0.5min; thresholding around the spatial contrast resolution limit reduced completion times to ~2min. There was good agreement with high-contrast visual acuity (difference=0.08±0.02logMAR) and contrast-sensitivity at 1.5 cycles/° (0.13±0.06logCS). Test-retest reliability was excellent at all spatial frequencies (ICC=0.99). Mesopic illumination or simulated cataract caused a generalised SCS loss; myopic blur reduced high-frequency sensitivity. Spatial contrast sensitivity was independent of radial axis orientation (cardinal or oblique). The chart provides a time-efficient, reliable and inexpensive measure of SCS with applications in research and clinic for detecting subtle deficits in early stages of ocular and neurological conditions that often manifest at higher frequencies. It is sensitive to vision changes occurring in dim lighting and with simulated cataract and blur. The chart is available open-access for self-printing; contrast variation in print can be controlled through user calibration and/or establishing normative SCS functions using the theoretical values.

Dynamic Biometric Indicators of the Anterior Segment Structure of the Eye in Primary Angle-Closure Glaucoma

Introduction. Primary angle-closure glaucoma (PACG) remains one of the leading causes of irreversible blindness. Up to date, a significant amount of data has been accumulated concerning the biometric parameters of the eye in PACG, however, there is a lack of information on the dynamic characteristics of these parameters.Objective: to evaluate the dynamic biometric characteristics of the structures of the anterior segment of the eye in PACG.Patients and methods. The results of optical coherence tomography were analyzed in 40 patients with PACG and in 40 patients without signs of hydrodynamic disorder. The studies were carried out under photopic and mesopic illumination conditions. The scanned images were obtained using an RTVue-100-2 optical coherence tomograph device (Optovue, USA). Biometric measurements were performed using standard tomograph software; volumetric studies were carried out based on the Pappus-Guldinus theorem with additional constructions. When analyzing the obtained images, 13 different linear and volumetric parameters were evaluated.Results. A decrease in the parameters reflecting the features of the configuration of the anterior chamber of the eye was noted in the presence of PACG (width of the ACA, depth and volume of the anterior chamber). From the point of view of the possible influence on the state of the anterior chamber angle, it is necessary to highlight changes in such indicators as the area, volume and thickness of the iris. Regardless of the conditions of the examination, these indicators, on average, were significantly higher in the PACG and practically did not change with a decrease in the level of illumination. At the same time, in the absence of disturbances in hydrodynamics under mesopic conditions, despite an increase in the thickness of the iris, a significant decrease in its area and volume was noted.Conclusion. Biometric changes in the structures of the anterior segment of the eye in the case of PACG relate not only to linear, but also to volumetric indicators. As a certain component of hydrodynamic disorders in the case of PACG, the revealed preservation of the iris volume during pupil dilation under mesopic illumination conditions should be considered, while in the absence of hydrodynamic disorders, this indicator decreased. Therefore, not only static changes in the biometric characteristics of the structures of the anterior segment of the eye, but also their dynamic fluctuations, should be considered as a risk factor for clinical manifestations of PACG, which determines the practical significance of dynamic biometric studies in the examination of patients with suspected PACG.

Effect of Correlated Color Temperature and S/P-ratio of LED Light Sources on Reaction Time in Off-axis Vision and Mesopic Lighting Levels

ABSTRACT The increasing replacement of traditional lamps by LED technology opens the door to research into visual performance under their multiple possible spectral power distributions. The correlated color temperature and S/P-ratio are considered parameters characterizing the spectrum of a light source. The lack of firm conclusions motivates the analysis in this work of the influence of LED spectrum, which is defined by the correlated color temperature and S/P-ratio, on a representative night-driving task, visual reaction time. A two-channel and four primaries photostimulator was used as set-up for measuring reaction time in off-axis vision, at mesopic illumination conditions and for a range of stimulus contrasts. The experimental conditions included a wide range of correlated color temperatures, ranging from 1870 to 6350 K, and different S/P-ratios for the same temperature. A total of 16 young subjects participated in the experiments. The results show significant shorter reaction times for those conditions in which the spectrum has greater short-wavelength content. This is corroborated by the greater stimulation of rods and S-cones obtained in the calculation of their excitation level. However, the definition of the spectrum using the correlated color temperature and S/P-ratio does not equally define the results obtained. For the same temperature, a higher S/P-ratio provides lower reaction time values, but for the same S/P ratio reaction time is independent of the temperature. LED light sources with high short-wavelength content provide faster response on the basis of a greater excitation of rods and S-cones. The S/P-ratio is the best parameter to justify the effect of spectrum on reaction time, as considers the spectral sensitivity of the visual system in its calculation.

Effects of varying illumination on ocular aberrations and aberration compensation before and after small incision Lenticule extraction: a prospective cohort study

BackgroundThere are few reports regarding the influence of varying illumination on the compensation effect before and after corneal refractive surgery. We aimed to evaluate the changes in refraction, higher-order aberrations, and aberration compensation between mesopic and photopic illumination before and after small incision lenticule extraction.MethodsIn this prospective cohort study, only the right eyes of patients who underwent small incision lenticule extraction for the correction of myopia and myopic astigmatism at the Tianjin Eye Hospital were included. Wavefront refraction and higher-order aberrations were measured preoperatively and 3 months postoperatively under mesopic and photopic illumination. Compensation factors were calculated as 1 − (aberration of the whole eye/aberration of the anterior corneal surface).ResultsForty patients undergoing small incision lenticule extraction were enrolled. All surgeries were completed without postoperative complications. Preoperatively, the eyes only had a statistically significantly higher (t = − 4.589, p < .001) spherical refractive error under mesopic vs. photopic illumination (median [interquartile range], − 6.146 [2.356] vs. − 6.030 [2.619] diopters [D]), whereas postoperatively, the eyes also exhibited statistically significantly higher (t = − 3.013, p = .005) astigmatism (− 0.608 [0.414] vs. − 0.382 [0.319] D). Differences in spherical refraction between the two illuminations were the highest in postoperative eyes (Δ > 0.5 D). Only postoperative eyes exhibited statistically significant elevations (t ≥ 4.081, p < .001) in higher-order aberrations under mesopic illumination, and only preoperative eyes exhibited statistically significantly enhanced (χ2 = 6.373, p = .01 for fourth-order and χ2 = 11.850, p = .001 for primary spherical aberrations) and decreased (χ2 = 13.653, p = .001 for horizontal trefoil) compensation factors under mesopic illumination.ConclusionsExaggerations in higher-order aberrations and myopic shift after small incision lenticule extraction became apparent under mesopic illumination. Slight undercorrection may have an enhanced effect under low illumination and may reduce night vision. The specific changes in compensation effects in preoperative eyes may improve optical quality under mesopic illumination. Postoperative eyes have reduced compensation ability, specifically for spherical aberrations, under mesopic illumination, which may diminish night vision. Further studies that include the measurement of subjective night vision parameters should be conducted.

The pupillary dynamics of patients with physiological anisocoria.

To evaluate static pupillometric measurements and making inter-ocular comparative analysis in healthy subjects for demonstrating the prevalance of physiological anisocoria in various lighting conditions and to compare the variations of the dynamic pupillometric measurements of the patients with physiological anisocoria. Automatic quantitative pupillometry system was used to measure pupillary diameters in low mesopic (0.1 cd/m2), high mesopic (1 cd/m2), low photopic (10 cd/m2) and high photopic (100 cd/m2) conditions. After inter-ocular comparison of these data, the prevalance of physiological anisocoria was detected in four different lighting conditions. The inter-ocular dynamic pupillometric parameters (amplitude, latency, duration and velocity of pupil contraction; latency, duration and velocity of pupil dilation) of these patients were further analysed. After inter-ocular comparison of pupillary diameters of 195 participants [96 females (49.2%) and 99 males (50.8%)] with a mean age of 38.4 ± 18.9 years (range 7-78 years), six (3.1%) participants under high photopic; 11 (5.6%) participants under low photopic; 25 (12.8%) participants under high mesopic, and 34 (17.4%) participants under low mesopic illumination levels exhibited physiological anisocoria. The mean relative amplitude of anisocoric small pupils' contraction was lower than the mean relative amplitudes of pupil contraction of both isocoric and anisocoric large pupils (p = 0.021, p = 0.035, respectively). The mean velocity of anisocoric small pupils' contraction was lower than the mean velocity of anisocoric large pupils' contraction (p = 0.013). The mean contraction amplitude and contraction velocity of smaller pupils was lower when compared to fellow larger pupils of anisocoric patients.

Predictive value of pupillography on intraoperative floppy iris syndrome in preoperative period.

To present the frequency of intraoperative floppy iris syndrome (IFIS) in cataract patients who taking alpha 1-a receptor antagonist (ARA) drugs, and evaluate the predictive value of pupil diameter (PD) changes in IFIS patients. Male cataract patients who are under treatment with alpha-1a-ARAs (alfuzosin, tamsulosin) intraoperatively were evaluated and were grouped as with/without IFIS. The preoperative PD values were compared with controls. Also, the intraoperative manipulations and early/late complications were recorded. A total of 77 patients (77 eyes) of 94 benign prostate hyperplasia (BPH) patients have been defined as IFIS (81.91%) and 40 patients (40 eyes) were taking tamsulosin and 37 patients (37 eyes) were taking alfuzosin. During the cataract surgery, the rate of posterior capsular rupture (P=0.754), vitreous loss (P=0.585), iris tears (P=0.004), and iris catching (P=0.000) were higher in IFIS group, but the difference was significant only in the iris catching. At the postoperative first-month visit, persistent IOP rise and iris stromal tears were more frequent in IFIS group, but the difference was not significant (P=0.311, P=0.146; respectively). In contrast, Descemet membrane detachment was insignificantly more frequent in controls (P=0.311). In IFIS and control patients, PDs were 9.54±1.78 and 9.72±1.57 mm (P=0.255) under scotopic illumination, 8.54±1.43 and 8.74±1.25 mm (P=0.289) under mesopic illumination, 6.99±1.35 and 7.27±1.39 mm (P=0.662) under photopic illumination, respectively. However PDs were lower in IFIS under all illumination degrees, no significant difference was detected between groups. IFIS is a significant clinical syndrome with an increased intraoperative/postoperative complication ratio. The prediction of this syndrome is important because of prevention required precautions against possible complications. There is no association between IFIS and preoperative PD.

Threshold versus intensity functions in two-colour automated perimetry.

Two-colour computerised perimetry is a technique developed for assessing cone- and rod-function at fixed background luminances in retinal disease. However, the state of adaptation during testing is unknown but crucial in the interpretation of results. We therefore aimed to determine the adaptational state of rod- and cone-mechanisms in two-colour perimetry. Sensitivity to 480nm (blue) and 640nm (red) Goldmann size V targets was determined for 10 normal subjects aged 16 to 46years at 17 locations in the central 60 degrees of the visual field under scotopic conditions and then from -1.5 log cd m-2 to 2 log cd m-2 (white background) in 0.5 log unit steps. Data were fitted with threshold versus intensity (tvi) functions of the form logT=logT0 + log ((A+A0 )/A0 )n . No clear rod-cone break was observed for 640nm stimuli. For 480nm stimuli, transition from rod-detection to cone-detection occurred at mesopic illumination levels, where rod adaptation approached Weber behaviour. Cone detection mechanisms did not display Weber-like adaptation until the background luminance approached 1 log cd.m-2 . Diseases resulting in a "filter effect" - including disorders of the photoreceptors - are therefore predicted to affect sensitivity when rod function is probed with short-wavelength targets under scotopic conditions, but less so under mesopic conditions. Filter effects are similarly anticipated to affect cone function measured using long-wavelength targets under mesopic conditions (e.g., during microperimetry), but less so under photopic conditions. Asymmetries in adaptation in automated two-colour perimetry are predicted to artefactually favour the detection of losses in rod sensitivity under scotopic conditions and cones under mesopic conditions.

Elevated Melatonin Levels Found in Young Myopic Adults Are Not Attributable to a Shift in Circadian Phase

PurposeTo evaluate the relationship between refractive error, circadian phase, and melatonin with consideration of prior light exposure, physical activity, and sleep.MethodsHealthy young myopic (spherical equivalent refraction [SER] ≤−0.50DS) and emmetropic adults underwent noncycloplegic autorefraction and axial length (AL) measures. Objective measurements of light exposure, physical activity, and sleep were captured across 7 days by wrist-worn Actiwatch-2 devices. Questionnaires assessed sleep quality and chronotype. Hourly evening saliva sampling during a dim-light melatonin onset (DLMO) protocol evaluated circadian phase, and both morning serum and saliva samples were collected. Liquid chromatography/mass spectrometry quantified melatonin.ResultsSubjects (n = 51) were aged 21.4 (interquartile range, 20.1−24.0) years. Melatonin was significantly higher in the myopic group at every evening time point and with both morning serum and saliva sampling (P ≤ 0.001 for all). DLMO-derived circadian phase did not differ between groups (P = 0.98). Multiple linear regression analysis demonstrated significant associations between serum melatonin and SER (B = –.34, β = –.42, P = 0.001), moderate activity (B = .009, β = .32, P = 0.01), and mesopic illumination (B = –.007, β = –.29, P = 0.02), F(3, 46) = 7.23, P < 0.001, R2 = 0.32, R2adjusted = .28. Myopes spent significantly more time exposed to “indoor” photopic illumination (3 to ≤1000 lux; P = 0.05), but “indoor” photopic illumination was not associated with SER, AL, or melatonin, and neither sleep, physical activity, nor any other light exposure metric differed significantly between groups (P > 0.05 for all).ConclusionsWhile circadian phase is aligned in adult myopes and emmetropes, myopia is associated with both elevated serum and salivary melatonin levels. Prospective studies are required to ascertain whether elevated melatonin levels occur before, during, or after myopia development.

Effect of Different Spectral Power Distributions on Mesopic Visual Performance with Blue Light-filtering Intraocular Lens

ABSTRACT The purpose of this work is to analyze the interaction between the spectral transmittance of old-aged subjects, before and after cataract surgery and blue light-filtering intraocular lens implantation, and the spectral power distribution of common street lamps, under conditions typical of nighttime driving. We analyzed contrast threshold and visual reaction time in off-axis vision at different mesopic illumination conditions provided by high-pressure sodium and metal halide lamps. Three groups of subjects with different spectral transmittances participated: young subjects as control group, old-aged subjects with senile cataracts and the same subjects after cataract surgery and blue light-filtering IOL implantation. A clear interaction appears between the spectral power distribution and the spectral transmittance, depending on the visual task. Transparent ocular media allow benefiting from the greater short-wavelength content of the halide lamp. However, cataracts increase contrast threshold and visual reaction time values and also affects how the spectral power distribution influences these visual tasks. After surgery and intraocular lens implantation, visual performance improves for both lamps and the blue light-filter seems to influence spectral transmittance, which affects visual performance under light provided by greater short-wavelength content lamps. Cataract surgery is responsible for an improvement in contrast threshold and visual reaction time tasks, though blue light-filtering of the intraocular lens seems to prevent the visual system from benefiting from lamps with greater emission at short wavelengths.

Rhodopsin and melanopsin contributions to human brightness estimation.

We examined the contributions of rhodopsin and melanopsin to human brightness estimation under dim lighting. Absolute brightness magnitudes were estimated for full-field, rhodopsin-, or melanopsin-equated narrowband lights (${\lambda _{\rm max}}:\;{462}$λmax:462, 499, 525 nm). Our data show that in scotopic illumination ($ - {5.1}$-5.1 to $ - {3.9}\;{\log}\;\unicode{x00B5} {\rm Watts}\cdot{\rm cm}^{ - 2}$-3.9logµWatts⋅cm-2), the perceptual brightness estimates of rhodopic irradiance-equated conditions are independent of their corresponding melanopic irradiance, whereas brightness estimates with melanopic irradiance-equated conditions increase with increasing rhodopic irradiance. In mesopic illumination ($ - {3.4}$-3.4 to $ - {1.9}\;{\log}\;\unicode{x00B5} {\rm Watts}\cdot{\rm cm}^{ - 2}$-1.9logµWatts⋅cm-2), the brightness estimates with both lighting conditions increase with increasing rhodopic or melanopic irradiances. Rhodopsin activation therefore entirely signals scotopic brightness perception and plateaus in mesopic illumination where intrinsic melanopsin contributions become first evident. We infer that all photoreceptor signals are transmitted to higher visual centers for representing scene brightness in scotopic and mesopic illumination through both conventional and melanopsin ganglion cell pathways.

Visual acuity and contrast sensitivity outcomes based on photoreceptor layer after retinal reattachment surgery

Aims: To evaluate correlation between photoreceptor layer thickness with visual acuity and contrast sensitivity in primary retinal reattachment after vitrectomy. Methods: Twenty seven eyes of 27 patients (mean age 45.6±12.7 years) with successfully retinal reattached were analyzed. Snellen chart visual acuity (VA) to evaluate best-corrected visual acuity (BCVA) converted to the logarithm of the minimum angle of resolution scale (logMAR) and contrast sensitivity in photopic and mesopic illumination using Lea Symbol Flip Chart, funduscopy examination and High Definition Optical Coherence Tomography (HD-OCT) were used to measure retinal condition and photoreceptor layer thickness. Results: Nineteen (70.4%) cases of total 27 cases were reported with macularon RRD. The thickness of the photoreceptor layer was 43.8±10.8 µm which was significantly correlated with BCVA (logMAR 0.3-2.4, mean 1.0) with p is less 0.005 and also with contrast sensitivity in mesopic with p 0.033 (p ≤ 0.05). Contrast sensitivity in photopic was better than in mesopic. Foveal anatomic abnormalities were detected in six eyes (22.2%), that was disruption of inner segment (IS)/outer segment (OS) junction and also disruption of external limiting membrane (ELM). Duration of detachment also significantly correlated with BCVA with mean 36±29 days. The macular status before surgery determines the quality of vision, whereas the macular-on rhegmatogen retinal detachment gives visual acuity, contrast sensitivity, that is better in both photopic and mesopic, than macular-off. Conclusion: Photoreceptor layer thickness significantly correlated with visual acuity and contrast sensitivity in mesopic illumination, whereas thicker the photoreceptor, better the visual acuity and mesopic contrast sensitivity.

Contrast adaptation appears independent of the longitudinal chromatic aberration of the human eye.

As ocular chromatic aberration was suspected to cue contrast adaptation in human vision, the purpose of this study was to investigate contrast adaptation under monochromatic light conditions. Single and complex frequency adaptation stimuli were used, and monochromatic conditions were achieved using band pass filters with short (470±2 nm), medium (530±2 nm), and long (630±2 nm) transmission wavelengths. Post-adaptational contrast sensitivity was shown to be significantly decreased for all wavelength conditions for the single frequency stimulus. A significant difference of contrast adaptation between short and long wavelengths was found. Consistently, adaptation led to a significant decrease in contrast sensitivity for the complex frequency stimulus. To conclude, contrast adaptation under mesopic illumination occurs independently of the longitudinal chromatic aberration of the eye; it can be inferred that this mechanism can be used to distinguish between the sign of optical defocus in poly- and monochromatic light conditions.

Extrinsic cone-mediated post-receptoral noise inhibits the rod temporal impulse response function.

We determined how extrinsic white noise correlating with cone inputs to the three primary visual pathways affects both rod-pathway temporal contrast sensitivity and the impulse response function. A four-primary photostimulator provided independent control of rod and cone photoreceptor excitations under mesopic illumination (20 photopic Td). We show that rod-pathway temporal contrast sensitivity uniformly decreases across all temporal frequencies in the presence of cone noise correlating with the inferred magnocellular, parvocellular, or koniocellular pathways. The rod-pathway temporal impulse response functions derived using the Stork-Falk procedure (with a minimum phase assumption) had lower amplitudes in the pathway-specific cone noise. Therefore, cone noise impairs rod-pathway temporal contrast sensitivity without delaying rod-pathway signal transmission.

Correlated and Uncorrelated Invisible Temporal White Noise Alters Mesopic Rod Signaling

We determined how rod signaling at mesopic light levels is altered by extrinsic temporal white noise that is correlated or uncorrelated with the activity of one (magnocellular, parvocellular, or koniocellular) postreceptoral pathway. Rod and cone photoreceptor excitations were independently controlled using a four-primary photostimulator. Psychometric (Weibull) functions were measured for incremental rod pulses (50 to 250 ms) in the presence (or absence; control) of perceptually invisible subthreshold extrinsic noise. Uncorrelated (rod) noise facilitates rod detection. Correlated postreceptoral pathway noise produces differential changes in rod detection thresholds and decreases the slope of the psychometric functions. We demonstrate that invisible extrinsic noise changes rod-signaling characteristics within the three retinogeniculate pathways at mesopic illumination depending on the temporal profile of the rod stimulus and the extrinsic noise type.