Association between Contrast Sensitivity and Reading with Macular Pathology.

SIGNIFICANCE: Comparison between the role of spatial and temporal contrast sensitivities in the association with reading may provide insight into how visual tasks (such as reading) are related to primary optical or neural (or both) effects. More insight into primary visual factors influencing reading is important for understanding reading problems. PURPOSE: The aim of this study was to gain insight into the association between optical and neural components of contrast sensitivity (CS), operationalized as spatial CS (optical and neural) or temporal CS (solely neural), and reading speed in a clinical sample of participants with macular pathologies. The precision and agreement were also investigated. METHODS: The Mars test and temporal CS implementation of the C-Quant device were used to measure spatial CS and temporal CS, respectively. Tests were performed with 47 participants: mean age, 77 years (range, 52 to 92 years). Associations were investigated with correlations and linear regression models. Precision was defined by coefficients of repeatability. The 95% limits of agreement between spatial CS and temporal CS values were assessed. RESULTS: Reading speed correlated with both spatial CS (r = 0.35, P = .015) and temporal CS (r = 0.66, P < .001). After correction for visual acuity, central loss, and education level, the association between temporal CS and reading speed was not significant anymore. The coefficients of repeatability and reproducibility were 0.20 and 0.28 log unit (spatial CS) and 0.33 and 0.35 log unit (temporal CS), respectively. The values for temporal CS were 0.08 and 0.13 log unit higher than those for spatial CS. CONCLUSIONS: For spatial CS and temporal CS, moderate to strong correlations were found, respectively, with reading speed in patients with maculopathies. The stronger association between temporal CS and reading speed is suggested to reflect a high sensitivity for neural integrity of temporal CS. The differences in coefficients of repeatability and reproducibility could be explained by the psychometrical differences between methods.

Intraocular light scatter, reflections, fluorescence and absorption: what we see in the slit lamp.

PURPOSE: Much knowledge has been collected over the past 20 years about light scattering in the eye- in particular in the eye lens- and its visual effect, called straylight. It is the purpose of this review to discuss how these insights can be applied to understanding the slit lamp image. RESULTS: The slit lamp image mainly results from back scattering, whereas the effects on vision result mainly from forward scatter. Forward scatter originates from particles of about wavelength size distributed throughout the lens. Most of the slit lamp image originates from small particle scatter (Rayleigh scatter). For a population of middle aged lenses it will be shown that both these scatter components remove around 10% of the light from the direct beam. For slit lamp observation close to the reflection angles, zones of discontinuity (Wasserspalten) at anterior and posterior parts of the lens show up as rough surface reflections. All these light scatter effects increase with age, but the correlations with age, and also between the different components, are weak. For retro-illumination imaging it will be argued that the density or opacity seen in areas of cortical or posterior subcapsular cataract show up because of light scattering, not because of light loss. NOTES: (1) Light scatter must not be confused with aberrations. Light penetrating the eye is divided into two parts: a relatively small part is scattered, and removed from the direct beam. Most of the light is not scattered, but continues as the direct beam. This non-scattered part is the basis for functional imaging, but its quality is under the control of aberrations. Aberrations deflect light mainly over small angles (<1°), whereas light scatter is important because of the straylight effects over large angles (>1°), causing problems like glare and hazy vision. (2) The slit lamp image in older lenses and nuclear cataract is strongly influenced by absorption. However, this effect is greatly exaggerated by the light path lengths concerned. This obviates proper judgement of the functional importance of absorption, and hinders the appreciation of the Rayleigh nature of what is seen in the slit lamp image.

Effects of Corneal Scars and Their Treatment With Rigid Contact Lenses on Quality of Vision.

OBJECTIVES: To study the effects of corneal scars and the treatment of these scars with rigid gas-permeable (RGP) contact lenses on quality of vision including straylight. Visual effects were related to scar characteristics such as size and grade. METHODS: Straylight and best-corrected visual acuity were measured in 23 patients with corneal scars during and after RGP contact lens wear. Contralateral eyes were used as controls, and age-normal values in case of bilateral scars. Straylight measurements were performed using the compensation comparison method of the Oculus C-Quant instrument. RESULTS: Scarred eye straylight values were 1.53 log(s) without contact lens and 1.60 log(s) with contact lens (P=0.043). Healthy eyes without contact lens had a mean straylight value of 1.13 log(s), corresponding to age-normal values. Contact lens wear increased straylight in healthy eyes to 1.26 log(s) (P<0.001). Visual acuity improved from 0.66 logarithm of minimal angle of resolution (logMAR) to 0.19 logMAR with contact lens wear in eyes with a corneal scar (P<0.001). CONCLUSIONS: Corneal scars can have a strong effect on quality of vision by diminishing visual acuity and increasing straylight. The increase in straylight from corneal scars on its own can lead to a serious visual handicap. Contact lens treatment did not improve straylight, but showed a slight worsening. As the recovery of visual acuity with contact lens wear far exceeded straylight increase, contact lenses remain a clinically useful treatment option in most patients with corneal scars.

Ocular Straylight with Different Multifocal Contact Lenses.

PURPOSE: Multifocal contact lenses have been growing in popularity as a modality to correct presbyopic eyes, although visual side effects such as disability glare have been reported. The objective of this study was to investigate the effect of multifocal contact lenses on disability glare by means of ocular straylight. METHODS: A prospective randomized, comparative study was performed that included 16 subjects free of ocular pathology. Straylight was measured using a commercial straylight meter with the natural and dilated pupil. Participants were fitted with Proclear Multifocal (Distance/Near), ACUVUE Oasys for Presbyopia, and Air Optix Aqua Multifocal randomized to the left or right eye. Straylight measurements were repeated with the contact lens in situ after the pupil dilation. Results obtained with the dilated pupil without contact lens acted as a control. RESULTS: Diameter of the natural and dilated pupil was 2.87 ± 0.40 mm and 7.45 ± 0.86 mm, respectively (P < .001). After pupil dilation, straylight increased from 0.92 ± 0.13 log(s) to 1.04 ± 0.11 log(s) (P < .001). Of the four studied lenses, a significant difference was only found between Air Optix and the control group (P = .006). The latter showed also slightly increased light scatter. CONCLUSIONS: A difference in measured straylight was found between the studied multifocal lenses. The observed variability and the straylight-pupil size dependency should be taken into account to avoid elevated straylight in multifocal contact lens wearers. The reason for the observed differences in straylight must be the subject of future studies.

Associations Between Spatial and Temporal Contrast Sensitivity and Reading.

PURPOSE: To gain insight into the association between optical and neural components of contrast sensitivity (CS), operationalized as spatial CS (optical and neural) or temporal CS (solely neural), and reading speed in a clinical sample of healthy adults of various ages. Furthermore, precision and agreement of the two methods were assessed. METHODS: The Mars test and the temporal CS implementation of the C-Quant device were used to measure spatial CS and temporal CS, respectively. Tests were performed with 71 normally sighted adults: mean age 55 (range 18-86) years. Pearson's correlation analyses were performed between spatial CS or temporal CS, and reading speed and partial correlations controlled for age are presented. Precision of the measurement was defined by the coefficient of repeatability and repeated measures standard deviations. Differences between spatial CS and temporal CS values were determined with 95% limits of agreement. RESULTS: A correlation was found between reading speed and both spatial CS (r = 0.470; P < .001) and temporal CS (r = 0.258; P = .04); partial correlations controlled for age were r = 0.175 (P = .17) and r = 0.152 (P = .24), respectively. Coefficient of repeatability was 0.13 log units and 0.24 log units for spatial CS and temporal CS test, respectively. A proportional difference of 0.1 log units was found between spatial CS and temporal CS measurements. CONCLUSIONS: A significant correlation was found between both spatial CS and temporal CS and reading speed indicating that, besides optical components, neural aspects may be important in defining reading speed. The stronger correlation between spatial CS and reading speed is suggested to reflect a deterioration of both optical and neural factors with increasing age. The coefficients of repeatability for spatial CS and temporal CS found in the present study are in agreement with previous research, and the difference found between the two methods might be attributed to the psychometric differences between the methods.

The (lack of) relation between straylight and visual acuity. Two domains of the point-spread-function.

PURPOSE: The effect of cataract and other media opacities on functional vision is typically assessed clinically using visual acuity. In both clinical and basic research, straylight (the functional result of light scattering in the eye) is commonly measured. The purpose of the present study was to determine the link between these two measures: is visual acuity in cataract and other media opacities related to straylight? METHODS: Interdependence between acuity and straylight is addressed from three different points of view: (1) Methodological: can acuity differences affect the measurement value of straylight, and vice versa? (2) Basic optics: does the optical process of light scattering in the human eye affect both straylight and visual acuity? (3) Statistical: how strongly are acuity and straylight correlated in the practice of important clinical conditions? Experimental and theoretical aspects will be considered, with a focus on normal ageing and cataract formation. RESULTS: (1) Methodological: testing potential effects of acuity, artificially manipulated with positive trial lenses, showed no effect on measured straylight values. Since light scattering in the eye involves a low percentage of the light and has large angular spreading, contrast reduction due to straylight is limited, resulting in virtually absent acuity effects. (2) Basic optics: light scattering from the human donor eye lens is found to have virtually no effect in the centre of the point-spread-function, also for cataractous lenses, resulting in virtually absent acuity effects. (3) Statistical: literature data on straylight and visual acuity show a weak correlation for the important groups of normal ageing and cataract populations. CONCLUSIONS: The point-spread-function of the normal ageing and cataractous human eye is built upon two rather independent basic parts. Aberrations control the central peak. Light scattering controls the periphery from about 1° onwards. The way acuity and straylight are measured ensures no confounding between them. Statistically within the normal ageing and cataract populations, visual acuity and straylight vary quite independently from each other. Visual acuity losses with cataract and other media opacities are not due to straylight, but caused by aberrations and micro-aberrations. Straylight defines disability glare, and causes symptoms of glare, haloes, hazy vision etc. Overall, visual acuity and straylight are rather independent aspects of quality of vision.

Changes in straylight after cataract surgery.

PURPOSE: To investigate straylight in the immediate postoperative period after cataract surgery. SETTING: Amphia Hospital, Breda, the Netherlands. DESIGN: Prospective, comparative, single-arm, single-center, single-surgeon study. METHODS: Patients underwent cataract surgery on both eyes. 1 eye was randomly selected for implantation with a Clareon CNA0T0 intraocular lens (IOL); the fellow eye received a Vivinex XY1 IOL. Straylight was measured with the C-Quant straylight meter. RESULTS: 25 patients were included. Preoperatively, 1 day, 1 week, 1 month, and 3 months postoperatively, eyes with a CNA0T0 IOL had straylight levels (mean ± SD) of 1.48 ± 0.23, 1.26 ± 0.20, 1.06 ± 0.19, 1.11 ± 0.25, and 1.09 ± 0.20 log(s), respectively. For eyes with an XY1 IOL, these values were 1.48 ± 0.21, 1.41 ± 0.41, 1.10 ± 0.20, 1.13 ± 0.20, and 1.16 ± 0.20 log(s), respectively. From 1 week postoperatively, straylight values did not change (1 week vs 3 months: P = .40 and P = .14 and 1 month vs 3 months: P = .74 and P = .50 for CNA0T0 and XY1, respectively). The Pearson correlation coefficient for straylight values between the 2 eyes of individual subjects was 0.80 at 3 months. CONCLUSIONS: Straylight levels can be considered stable 1 week after cataract surgery. We believe it is safe to use straylight measurements 1 month postoperatively for clinical trials. Straylight is highly correlated between the 2 eyes of an individual postoperatively.

Characterizing glare effects associated with diffractive optics in presbyopia-correcting intraocular lenses.

PURPOSE: To objectively quantify glare of intraocular lenses (IOLs) using a diffractive principle to extend the visual range and to identify models with increased susceptibility to inducing glare. SETTING: David J Apple Laboratory, Heidelberg, Germany. DESIGN: Laboratory investigation. METHODS: Glare was assessed by means of a straylight parameter with a standard C-Quant intended for 7 degrees. In addition, 2 C-Quant modifications were used to test lower angles (ie, 2.5 degrees and 3.5 degrees). The following IOL models were assessed: PanOptix, AT Lisa Tri, Synergy, and Triumf, the latter 2 with chromatic aberration correction at distance. Straylight from trifocal IOLs was compared against a monofocal W-60R lens. The C-Quant test was performed through the studied IOLs by using additional optical components attached to their ocular. RESULTS: Straylight (deg 2 sr -1 ) of the control was <1 at all tested angles, with the trifocal models showing comparable straylight at 7 degrees. At 3.5 degrees, Triumf's straylight increased to 15.5 ± 0.6, followed by Synergy (6.2 ± 1.1), PanOptix (4.1 ± 0.3), and AT Lisa Tri (2.0 ± 0.8). The chromatic aberration-correcting models demonstrated correspondingly higher straylight (Synergy: 18.8 ± 1.3; Triumf: 17.3 ± 0.5) at 2.5 degrees compared with PanOptix (4.3 ± 0.4), AT Lisa Tri (2.1 ± 0.1), and monofocal IOLs yielding minimal or no increase. CONCLUSIONS: Trifocal IOLs induced increased straylight, but it was limited to lower angles, which may cause difficulties detecting these effects using a standard clinical approach. The latest IOL designs featuring chromatic aberration correction at far focus seem more susceptible than the established trifocal IOLs to inducing a glare phenomenon.

Posterior capsule opacification severity, assessed with straylight measurement, as main indicator of early visual function deterioration.

PURPOSE: To study the effect of posterior capsule opacification (PCO) morphology and severity on different aspects of visual function (VF): the small-angle domain (visual acuity [VA], contrast sensitivity [CS]) and large-angle domain (straylight; logarithm of the straylight parameter s [log{s}]). To evaluate whether straylight is a valuable additional indicator for appropriate posterior capsulotomy referral. DESIGN: Prospective, comparative study. PARTICIPANTS AND CONTROLS: For the study population, 240 pseudophakic eyes with PCO and a capsulotomy indication were selected. For the reference population, 99 pseudophakic eyes without PCO were selected. METHODS: The relation between PCO morphology and PCO severity and the precapsulotomy and postcapsulotomy logarithm of the minimum angle of resolution (logMAR), logarithm of CS (log[CS]), and log(s) values were determined. The PCO severity was assessed with retroillumination using evaluation of posterior capsule opacification (EPCO) software. Precapsulotomy logMAR and log(s) values were used to predict functionally significant logMAR and log(s) improvement after capsulotomy. MAIN OUTCOME MEASURES: The logMAR, log(CS), and log(s) improvements of ≥0.20 log units were considered functionally significant (i.e., treatment effect). Precapsulotomy logMAR and log(s) values, above which a treatment effect (improvement≥0.20 log units) can be expected with ≥50% probability, were determined and called cutoff values. RESULTS: Postcapsulotomy VF improvement was related to precapsulotomy VF values: Postcapsulotomy improvement was largest in cases with substantially impaired precapsulotomy VF parameters. Visual function deterioration was related to PCO severity rather than PCO morphology. The PCO severity (EPCO score) assessed with retroillumination has a progressive, linear relation with log(s) and a curvilinear relation with logMAR. Reflected light examination is expected to overestimate functional PCO severity. The precapsulotomy cutoff value was ≥1.44 for log(s) and ≥0.21 for logMAR. CONCLUSIONS: The linear relation between retroillumination PCO severity and log(s) indicates that log(s) is sensitive to low PCO severity, whereas the curvilinear relation between PCO severity and logMAR indicates that logMAR is unaffected by low PCO severity. Straylight is a sensitive, additional indicator for capsulotomy referral, especially in less severe cases of PCO. In ophthalmic practice, the precapsulotomy log(s) cutoff value of 1.44 can be used as an indicator for beneficial capsulotomy referral. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Iris color and visual functions.

BACKGROUND: The aim of this study was to evaluate if iris color is associated with differences in visual functions such as intraocular straylight (IOSL), contrast sensitivity (CS), or best-corrected visual acuity (BCVA). METHODS: In this retrospective cohort study, which is a subgroup analysis of a large prospective trial about visual impairments in European car drivers, we included 853 persons between 20 and 80 years of age and without a history of ocular surgery or any eye disease including cataract. Subjects participated in an ophthalmological examination, grading of lens opacity, and the measurement of visual functions such as IOSL, CS, and BCVA. Dependent on iris color, participants were divided into four groups: light-blue, blue-grey, green-hazel, and brown. RESULTS: Independent of age, IOSL was significantly (all p values < 0.0001, Fisher's LSD test) higher in participants with light-blue colored iris (1.14 log(IOSL) [95 % CI: 1.11-1.17]) compared to participants with blue-grey (1.07 log(IOSL) [95 % CI: 1.05-1.09]), green-hazel (1.06 log(IOSL) [95 % CI: 1.04-1.08]) or brown (1.06 log(IOSL) [95 % CI: 1.04-1.08]) iris color. CS was also lower in participants with light-blue pigmented irises (1.60 log(CS) [95 % CI: 1.58-1.62]) than in the other groups, but statistically significant (p = 0.013, Fisher's LSD test) only compared to brown iris color. For BCVA we could not found any difference between the four groups. CONCLUSIONS: We could show in this study that iris color has a significant impact on IOSL and to a lower degree on CS, but not on BCVA. Persons with light-blue iris color who showed significantly higher IOSL values therefore may experience disability glare in daily situations such as driving at night more often than others.

Diurnal Variation in Straylight in Patients With Fuchs Endothelial Corneal Dystrophy and Controls.

PURPOSE: The goal of this study was to investigate diurnal changes in intraocular straylight in relation to other corneal parameters and subjective complaints in patients with Fuchs endothelial dystrophy and healthy controls. METHODS: This is a prospective study conducted in 2 tertiary care hospitals in Germany and the Netherlands. Patients with Fuchs endothelial dystrophy (n = 71) and healthy controls (n = 34) were included. Patients with Fuchs dystrophy were grouped by the presence of subjective complaints and measured over multiple time points during the day. Measurements included intraocular straylight using the C-Quant and corneal thickness and backscatter using a Scheimpflug camera. A separate group of healthy controls was measured intensively with repeated straylight measurements directly after waking. An exponential decay model was used to model the diurnal change. RESULTS: Healthy controls showed an average straylight baseline of 1.17 log(s) with an increase in straylight after waking of 0.22 log(s). In the repeated measurements subgroup, the increase in morning straylight lasted for 22 minutes. Patients with Fuchs dystrophy showed a morning increase in straylight of 0.21 log(s) present up to 4 hours after waking before reaching an average baseline of 1.30 log(s). Straylight was positively correlated with anterior corneal backscatter, r = 0.21, P = 0.022, and corneal thickness, r = 0.46, P < 0.01. CONCLUSIONS: Healthy eyes experience a diurnal straylight increase similar to patients with Fuchs dystrophy in intensity. However, in Fuchs dystrophy, the resolution of increased straylight is prolonged over multiple hours compared with minutes in healthy eyes. This suggests pathological exacerbation of a physiological diurnal change. This mechanism can play a role in subjective complaints experienced by patients with Fuchs dystrophy.

Visual symptoms and retinal straylight after laser peripheral iridotomy: the Zhongshan Angle-Closure Prevention Trial.

OBJECTIVE: To assess the impact of laser peripheral iridotomy (LPI) on forward-scatter of light and subjective visual symptoms and to identify LPI parameters influencing these phenomena. DESIGN: Cohort study derived from a randomized trial, using an external control group. PARTICIPANTS: Chinese subjects initially aged 50 or older and 70 years or younger with bilateral narrow angles undergoing LPI in 1 eye selected at random, and age- and gender-matched controls. METHODS: Eighteen months after laser, LPI-treated subjects underwent digital iris photography and photogrammetry to characterize the size and location of the LPI, Lens Opacity Classification System III cataract grading, and measurement of retinal straylight (C-Quant; OCULUS, Wetzlar, Germany) in the treated and untreated eyes and completed a visual symptoms questionnaire. Controls answered the questionnaire and underwent straylight measurement and (in a random one-sixth sample) cataract grading. MAIN OUTCOME MEASURES: Retinal straylight levels and subjective visual symptoms. RESULTS: Among 230 LPI-treated subjects (121 [58.8%] with LPI totally covered by the lid, 43 [19.8%] with LPI partly covered by the lid, 53 [24.4%] with LPI uncovered by the lid), 217 (94.3%) completed all testing, as did 250 (93.3%) of 268 controls. Age, gender, and prevalence of visual symptoms did not differ between treated subjects and controls, although nuclear (P<0.01) and cortical (P = 0.03) cataract were less common among controls. Neither presenting visual acuity nor straylight score differed between the treated and untreated eyes among all treated persons, nor among those (n = 96) with LPI partially or totally uncovered. Prevalence of subjective glare did not differ significantly between participants with totally covered LPI (6.61%; 95% confidence interval [CI], 3.39%-12.5%), partially covered LPI (11.6%; 95% CI, 5.07%-24.5%), or totally uncovered LPI (9.43%; 95% CI, 4.10%-10.3%). In regression models, only worse cortical cataract grade (P = 0.01) was associated significantly with straylight score, and no predictors were associated with subjective glare. None of the LPI size or location parameters were associated with straylight or subjective symptoms. CONCLUSIONS: These results suggests that LPI is safe regarding measures of straylight and visual symptoms. This randomized design provides strong evidence that treatment programs for narrow angles would be unlikely to result in important medium-term visual disability.

In-vitro recording of forward light-scatter by human lens capsules and different types of posterior capsule opacification.

The purpose of the present study was to elucidate the effect of posterior capsule opacification (PCO) on the straylight domain of visual function. PCO is heterogeneous with regard to morphology and severity; both aspects contribute to its functional effect. The isolated impact of capsule areas with specific morphology and severity on straylight was studied in-vitro by recording forward light-scatter. Forward light-scatter by four different capsule types, i.c. anterior capsule (AC), clear posterior capsule (PC), fibrotic and regeneratory PCO, was recorded at several visual angles with a goniometer, using different wavelengths. Angular (θ(a)) and wavelength dependencies (λ(b)) were studied by determining exponents a and b. Recorded straylight values of isolated capsule areas varied between 10× below to 10× above the value normal for the human eye, depending on the capsule's condition (clear to opacified). The angular dependence of light scattered by clear PCs was weaker, whereas in the other capsule types it was stronger than in the normal eye. On average, the wavelength dependence of light scattered by different capsule types was similar, but the variation was considerable. At the smallest visual angles, increased angular and decreased wavelength dependence was found, especially in fibrotic and regeneratory PCO. It was concluded that the range of straylight values found in-vitro in lens capsules properly corresponded to that found previously in in-vivo pseudophakics. Surprisingly, the wavelength dependence of PCO indicated that small-particle light-scattering is important in PCO. Refractile effects were more important at small visual angles, as indicated by the combined stronger angular and weaker wavelength dependence.

Light scattering from a diffractive-refractive intraocular lens: a goniometer-based approach for individual zone assessment.

We proposed and tested a method to measure light scattering from the diffractive lens profile in an echelle element featuring 9 zones. Measurements were performed using a goniometer-based setup up to 7.5°. The proportion of scattered light was calculated to derive the loss of light. Material scattering was minimal (∼1 deg2/sr); however, each echelle zone acted as a scattering source. A nearly gradual straylight increase was found with the zone number showing peak intensity between 3° and 3.75°. An estimated 6.2% ± 0.1% was lost due to scattering, which ought to be considered when reporting an IOL's light loss.

Straylight values after refractive surgery: screening for ocular fitness in demanding professions.

PURPOSE: To study straylight testing as a screening method for ocular fitness after refractive surgery in demanding professions and to determine the distribution of elevations in straylight as a result of refractive surgery in a non-research setting in contrast with earlier reports in research settings. DESIGN: Cross-sectional study. PARTICIPANTS AND CONTROLS: The refractive surgery population consisted of 373 eyes in 198 subjects with a history of refractive surgery. The reference population consisted of 402 eyes in 214 young individuals without a history of refractive surgery. METHODS: Data were collected as part of routine testing at The Queen Astrid Military Hospital (Belgium), an independent military institution responsible for medical fitness examinations. Intraocular straylight was measured with the commercially available C-Quant instrument (Oculus Optikgeräte GmbH, Wetzlar, Germany), using the psychophysical compensation comparison (CC) method. Fellow eyes were compared to evaluate methodological aspects. The prevalence of impairment was evaluated for 2 age-independent cutoff criteria, a 2.0-fold and 3.2-fold increase, and an age-dependent cutoff criterion corresponding to an increase of 0.20 log units. MAIN OUTCOME MEASURES: Methodological aspects such as repeatability, systematic differences, and distance to impaired scores, and prevalence of impaired straylight values after refractive surgery using proposed cutoff criteria. RESULTS: The CC method exhibited good repeatability, and the chance of impaired scores due to variability in measurement was small. The prevalence of impaired straylight values was minimal in the reference population. In the refractive population, 9% (33/373) of values were above the factor 2.0 criterion, 2% (7/373) were above the factor 3.2 criterion, and 12% (45/373) were 0.20 log units above the age reference. CONCLUSIONS: Straylight testing is a viable screening method for ocular fitness after refractive surgery. Patients from the general population who have undergone refractive surgery have significant elevations more frequently than surgery populations from high-quality research centers.

Ocular straylight in albinism.

PURPOSE: Albinism is an inherited disorder that affects the melanin biosynthesis pathway, which results in reduced or absent pigment formation. This may lead to increased light transmission through the iris and more reflected light from the fundus. Both these effects contribute to the occurrence of ocular straylight. One aim of this study is to determine whether and how increased iris transmission and fundus reflection in subjects with albinism contributes to the occurrence of ocular straylight. The other aim is to determine the effect that an iris print-contact lens (CL) could have in terms of reducing the occurrence of ocular straylight. METHODS: Ocular straylight was quantified by means of the straylight parameter s and measured as a function of angle and wavelength in 17 subjects with different types of albinism, none of whom wore an iris print-CL. The measurements were then repeated with the subjects wearing an iris print-CL to reduce the iris transmission component and thus the occurrence of ocular straylight. The contributions of transmission and reflectance components were estimated for each individual. RESULT: Straylight level increase varied from normal (s ≈9) to severe (8x). In 15 cases, the reflectance component contributed s >3 to up to s = 17. In eight cases, the transmission component contributed s >3 to up to s = 101. A significant reduction in straylight was observed using an iris print-CL in six subjects with elevated straylight values. In the other 11 subjects with albinism, the iris print-CL had no significant effect on straylight because of the low values of the transmission component. CONCLUSIONS: This study gives insight into the effects of transmission and reflectance on the total measured straylight occurrence in subjects with albinism. Subjects experiencing increased ocular straylight values may benefit significantly from wearing iris print-CLs because transmission of light through the natural iris may cause a significant increase in straylight.

Straylight due to intraocular lens opacification in a patient with asteroid hyalosis.

PURPOSE: To report a rare case of intraocular lens (IOL) calcification in the presence of asteroid hyalosis with in-vivo measurements of straylight before and after treatment. OBSERVATIONS: A patient with asteroid hyalosis presented with complaints of disability glare due to calcifications on the posterior surface of the IOL. Straylight, measured with the C-Quant, was 8.2x elevated compared to normal (log(s) 2.08). Dissolution of the posterior face IOL deposits was performed with a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, resulting in a significant decrease in straylight (log(s) 1.76), congruent with the patient's subjective improvement. CONCLUSIONS AND IMPORTANCE: To the best of our knowledge, this is the first report describing a patient with an opacified IOL due to asteroid hyalosis with in-vivo measurements of straylight before and after treatment. It illustrates that awareness of glare complaints in patients with an opacified IOL is important, documentation with C-Quant measurements may be helpful in indicating treatment, evaluating the treatment, and following up the patient, and treatment with a Nd:YAG laser may dissolve the opacifications to a clinically satisfactory level.

Quality factor based correction for SD-OCT measurements in cataract patients.

PURPOSE: To correct peripapillary retinal nerve fibre layer (pRNFL) measurements performed with spectral domain optical coherence tomography (SD-OCT) for low image quality factor (QF) in patients with cataract, using measurements before and after cataract surgery. METHODS: SD-OCT (Topcon 3DOCT-2000) volume scans of the optic disc of 13 cataract patients were used. A set of three reflective filters with optical density ranging from 0.11 to 0.54 were used. The correlation was calculated between the change in thickness measurements and the change in image quality factor. Changes before and after cataract surgery were analysed. A correction for scans with a lower QF was calculated using an equation which was formulated based on the relationship between the change in thickness measurements and the change in image quality factor. RESULTS: Thirteen right eyes of thirteen cataract patients were included in this study. pRNFL thickness measurements before and after cataract differed significantly (96 versus 99 micron, p < 0.01). Preoperative linear regression lines showed a different slope than postoperative regression lines. Corrected pRNFL thickness measurements of before cataract surgery differed significantly with pRNFL thickness measurements after cataract surgery. CONCLUSIONS: The presence of cataract influences the QF-pRNFL relationship. The lower the image QF, the higher the pRNFL thickness underestimation. We found a rather curvilinear relationship between QF and pRNFL. Our corrected measurements of the pRNFL thickness in case of lower image QF due to cataract still differed significantly from the pRNFL thickness measurements after cataract surgery.

Straylight in the human eye: testing objectivity and optical character of the psychophysical measurement.

The point spread function or PSF of the human eye encompasses hugely different domains: a small-angle, high-intensity domain, called the 'PSF core', and a large-angle, low-intensity domain, usually referred to as 'straylight'. The first domain can be assessed by available double-pass or other optical techniques. For the second domain psychophysical techniques have been developed, in particular the Compensation Comparison or CC technique, recently made available for clinical application in the C-Quant instrument. We address the question of whether the psychophysical technique gives measures of straylight that are compatible with those made by optical methods. With a small adaptation the CC method can be used to assess straylight from physical light scattering samples, instead of straylight in the eye, using the same psychophysics, but without interference from the ocular straylight. The light scattered by each of seven light-scattering samples, encompassing the range of straylight values observed in human eyes, was measured by two optical methods and by the psychophysical technique. The results showed that the optical and psychophysical measurements for the seven samples were almost identical.

The Effect of a Spectral Filter on Visual Quality in Patients with an Extended-Depth-Of-Focus Intraocular Lens.

PURPOSE: Wavelength dependence of diffractive intraocular lenses (IOLs) was recognized in vitro but not yet assessed in vivo. By examining pseudophakic patients who had extended-depth-of-focus diffractive implants, this spectral effect on their vision was measured clinically and the lens was tested in vitro. DESIGN: Cross-sectional study with laboratory investigation. METHODS: Twelve pseudophakic patients (23 eyes) with a Symfony lens (Johnson & Johnson Vision) were measured monocularly under red and white light at far, intermediate, and near distances. Corrected distance visual acuity (CDVA), distance-corrected intermediate visual acuity (DCIVA), and distance corrected near visual acuity (DCNVA) were assessed. Contrast sensitivity was examined at several spatial frequencies. The in vitro lens modulation transfer function was measured under different spectral conditions by using an IOL metrology device. RESULTS: CDVA was comparable under red and white light. DCIVA and DCNVA were significantly better under white light by 0.06 and 0.09, respectively. Contrast sensitivity was slightly better with a red filter at far distance but was worse at intermediate distance, although differences were significant only at 1 frequency. Near contrast sensitivity was better under polychromatic than red light, which was significant at 3 frequencies. The in vitro analysis confirmed Symfony's wavelength dependence: performance was improved at far distance but was worse at intermediate and near distances. CONCLUSIONS: Symfony's spectral dependence was observed to affect visual acuity and contrast sensitivity. Although the red filter did not improve distance vision, it caused visual deterioration at near distance. One should take this effect into account when optimizing the reading performance of patients with diffractive IOLs.