Flicker Thresholds Research Articles

The use of colour and rapid flicker sensitivity tests for early detection and monitoring of vision changes in diabetes

Aims/Purpose: There is increasing evidence of impaired visual function prior to the presence of diabetic retinopathy (DR), yet current diagnostic criteria and treatment onset rely mostly on retinal vascular changes. In this study we measured changes in chromatic and rapid flicker sensitivity in subjects with prediabetes and diabetes to establish the value of such tests as a potential biomarker in the detecting early diabetes.Methods: Three groups of subjects were recruited: 1) normal controls, 2) subjects with prediabetes (HbA1c between 42‐47 mmol/mol), and 3) diabetics (with or without DR). Monocular cone‐ and rod‐enhanced flicker modulation thresholds (FMTs) were measured at the point of regard and in four parafoveal (5°) locations using the Flicker‐Plus test. Monocular red/green (RG) and yellow/blue (YB) colour thresholds were also measured at the fovea using the Colour Assessment and Diagnosis (CAD) test.Results: Both the RG and YB thresholds, as well as rod‐ and cone‐mediated flicker thresholds were significantly higher in both diabetic and prediabetic groups (when compared with healthy controls). When examined individually, ~50% and ~ 63% of the prediabetics and ~ 58% and ~ 70% of the diabetics revealed abnormal RG and YB thresholds, respectively (when compared with the upper normal limits for the corresponding age). HBA1c levels also revealed a positive trend with increasing RG and YB thresholds in the prediabetic group.Conclusions: In agreement with previous findings, both colour and FMTs are affected in patients diagnosed with diabetes. Unexpectedly, those deemed prediabetic that do not meet the clinical criteria for diabetes exhibit considerable loss of both colour and flicker sensitivity. The results suggest that colour and rapid flicker tests can provide useful information when screening for diabetes.

New methods for detection of early loss of rapid flicker, spatial vision, and chromatic sensitivity in glaucoma

Purpose: To examine whether ocular hypertension and early glaucoma cause measurable changes in spatial vision, rapid flicker sensitivity and red/green and yellow/blue colour vision.Methods: We examined subjects aged 40 to 78 years with ocular hypertension (OHT), primary open angle glaucoma (POAG), normal tension glaucoma (NTG), and age matched controls. Monocular best corrected visual acuity (BCVA) was tested using EDTRS charts.VA and Functional Contrast Sensitivity (FCS) with Landolt ring stimuli of both positive and negative contrast were also measured monocularly with the Acuity‐Plus test. Red/green (RG) and yellow/blue (YB) colour thresholds were measured with the Colour Assessment and Diagnostics (CAD) test. Photopic (cone‐enhanced) and mesopic (rod‐enhanced) rapid flicker thresholds were measured at the fovea (0°) and at an eccentricity of 5° in each of the four quadrants using the Flicker‐Plus test. All subjects had their visual fields measured using the Humphrey visual field analyser (24–2 SITA standard protocol). Peripapillary retinal nerve fibre layer thickness (pRNFLT) and macular retinal layer thicknesses were measured using the Heidelberg Spectralis OCT.Results: The mean, logMAR BCVA for OHT patients was 0.00 and for POAG and NTG patients was −0.10 and 0.10, respectively. For control participants, mean logMAR BCVA was 0.00. Mean pRNFL thickness was significantly reduced for glaucoma patients (59.5 ± 7.7 μm) as compared to control subjects (94.6 ± 5.13 μm) and OHT patients (115.5 ± 3.5 μm). POAG and NTG patients showed significantly higher colour thresholds (mean red/green threshold 4.97, blue/yellow 5.28 CAD units) compared to control subjects (mean red/green threshold 2.07, blue/yellow 1.62 CAD units). One OHT patient showed acquired loss of blue/yellow colour vision (3.23 CAD units), with normal VA. The Acuity‐Plus test which employs briefly presented stimuli, also revealed significant loss of VA (3.78 and 3.64 min of arc) and FCS (141.32% and 100%) in an NTG patient, with results outside normal limits for both positive and negative contrast, respectively. Central FCS was higher and outside the normal age limits for POAG patients (73.41% and 89.27%) as compared to age matched controls (61.27% and 33.63%). OHT patients, on the other hand, produced FCS thresholds within normal limits. Flicker modulation thresholds were higher for both rod and cone enhanced stimulus conditions in glaucoma and OHT patients, when compared to control subjects.Conclusion: The results reveal non‐uniform, losses that can affect selectively each of the visual attributes examined in this study. These preliminary findings suggest that in addition to VA and FCS tests, colour vision and rapid flicker sensitivity should also be examined in patients with optic nerve pathologies like glaucoma.

Changes in visual function associated with hydroxychloroquine retinal toxicity

AbstractIntroduction: Non‐infectious inflammatory diseases, such as systemic lupus erythematosus, rheumatoid arthritis, dermatomyositis, antiphospholipid antibody syndrome and others cause significant morbidity and are treated with immunosuppression. Hydroxychloroquine (HCQ) sulfate is used as a second line immunosuppressant and has many advantages over other agents. These include increased life expectancy, reduced risk of neoplasia, reduced risk of diabetes and hypercholesterolaemia. HCQ is safe in pregnancy. After more than 5 years of treatment, HCQ can cause a degenerative maculopathy characterized by loss of parafoveal photoreceptors and RPE cells, leading to a ring‐like visual field defect. Current detection of early retinal toxicity relies on central visual field testing, optical coherence tomography (OCT) scan and fundus autofluorescence. The reason for the parafoveal predilection for retinopathy is not understood. HCQ is concentrated in melanin‐containing cells, and there is increased melanin concentration in the macular RPE cells. A hypothesis is that HCQ concentrated in the macular RPE cells leads to toxicity, with macular pigment protecting the fovea but leaving a ring of potentially vulnerable tissue in the parafoveal region. We were interested to investigate parafoveal function in patients with mild HCQ maculopathy and report the results of detailed macular function assessment of red/green (RG) and yellow / blue (YB) colour vision and rod‐ and cone‐mediated rapid flicker sensitivity.Methods: Two patients with confirmed early hydroxychloroquine maculopathy participated in the study. RG and YB colour thresholds were measured with the Colour Assessment and Diagnosis (CAD) test. Cone and rod‐mediated rapid flicker sensitivity was also measured in both central and paracentral vision using the Flicker‐Plus test. Both patients had taken HCQ for more than 15 years and had paracentral scotomas on 10–2 field test and loss of the parafoveal outer nuclear layer and ellipsoid layer, confirming the presence of maculopathy. To test the hypothesis of parafoveal toxicity risk, 20 short wavelength (BAF) and infrared wavelength (IRAF) autofluorescence images were reviewed. The BAF images are surrogate markers of the macular pigment and the IRAF the melanin concentration. Normalized maps of the difference between BAF and IRAF were calculated to investigate the possibility of a ring of vulnerable tissue.Results: Both patients had normal RG, but abnormal YB colour thresholds. One subject had normal cone flicker thresholds, but the rod flicker thresholds were raised in all quadrants in both eyes. The second subject had significantly elevated rod thresholds and elevated cone flicker thresholds in both eyes. Of note is that the degree of retinopathy in the second patient was greater than in the first. The areas of greatest threshold elevation correlated with the areas of greatest field loss and anatomical disruption on OCT.Conclusion: These new findings show that hydroxychloroquine retinopathy affects preferentially both YB colour vision and rod‐mediated flicker sensitivity. The cone‐mediated flicker sensitivity is also affected in more advanced disease. A model for the anatomical location of the toxicity will be presented, based on the hypothesis outlined above.

The value of colour assessment in diagnostic dilemmas

AbstractBackground: When the goal of clinical assessment is to segment, divide, and classify cases into neat discrete boxes it can often be frustrating to encounter cases which do not fit standard diagnosis algorithms. However, such diagnostic dilemmas often provide a valuable insight into the boundaries of current clinical procedures and the potential value psychophysical assessment can provide when used in conjunction with standard diagnosis algorithms. We present such a case involving localized retinal dysfunction that is not fully consistent with signs of either autoimmune retinopathy or occult maculopathy.Methods: Specific visual function loss was investigated in a health 32‐year‐old male with suspected localized retinal dysfunction, affecting the central retina. Blood tests and electro‐diagnostics were carried out after the patient presented with acute onset ‘foggy’ central vision. The working diagnosis from this initial visit was autoimmune retinopathy and oral steroids were prescribed. Following no change in symptoms a year after initially presenting, the patient was referred to City, University of London for bespoke assessments of specific visual functions. These included assessments of central and peripheral red / green (RG) and yellow / blue (YB) colour vision, mesopic visual acuity (VA), functional contrast sensitivity (FCS), rod‐ and cone‐mediated flicker sensitivity, and pupil responses measured using both rod‐ and cone‐enhanced stimuli.Results: The loss of vision affected primarily the central 20° with a mean VA of 6/36 in each eye. Fundus images, fluorescein angiography, and full field electroretinograms (ERGs) were normal, but pattern and focal ERGs were undetectable indicating localized dysfunction in central vision with OCT images showing a disrupted ellipsoid zone in each eye. The patient's mean corpuscular volume was 69 femtoliters, with red cell indices suggestive of thalassemia. Testing at City, University of London confirmed a loss of VA and FCS in the central 10° field, although both VA and FCS depended strongly on light level and were less affected with negative contrast stimuli. A loss of RG and YB colour vision was also measured centrally. Outside the central 10° field EA had almost normal colour and spatial vision. Rod‐ and cone‐mediated, flicker thresholds were elevated, with cone thresholds 10‐fold higher than normal. Pre‐stimulus pupil size, constriction amplitudes and latencies were normal with both centrally presented and peripheral stimuli.Conclusions: Psychophysical measurements in a patient with presumed autoimmune maculopathy showed atypical macular dysfunction that appears to preferentially affect negative contrast stimuli. Despite damage to the retinal mechanisms involved in spatial vision and light adaptation pupil responses remained unaffected. This unusual case highlights the importance of detailed phenotyping in understanding unknown aetiology.

Impact of symptomatic vitreous degeneration on photopic and mesopic contrast thresholds

ABSTRACT Clinical relevance Contrast thresholds under photopic and mesopic luminance conditions are compromised in subjects with vitreous degeneration. A plausible explanation is needed for the visual discomfort expressed by patients suffering from symptomatic vitreous degeneration. Background The current study investigates the effect of symptomatic vitreous degeneration on photopic and mesopic contrast at high spatial frequencies. Methods An age-matched sample of 115 subjects, comprising 30 subjects with symptomatic vitreous floaters (cases) and 85 healthy subjects (controls), was included in this study. Visual acuity and flicker thresholds were measured for all participants. Photopic and mesopic functional contrast thresholds at 10 cycles per degree were measured for all participants to assess the effect of floaters on contrast. Further, to determine the effect of posterior vitreous detachment on contrast, the sample was divided into three groups: cases with posterior vitreous detachment (n = 12); cases without posterior vitreous detachment (n = 18); and controls (n = 85), and their contrast thresholds were compared. Results Photopic and mesopic contrast thresholds were lower by 37.4% and 27.5%, respectively, when the cases were compared with the controls (p = 0.028 and p < 0.001 for photopic and mesopic contrast thresholds, respectively). Photopic contrast was lower by 64.0% in cases with posterior vitreous detachment compared with controls (p = 0.001). Compared with controls, mesopic contrast was lower in cases with posterior vitreous detachment and in cases without posterior vitreous detachment by 30.3% and 25.6%, respectively (p = 0.014 and p = 0.017 for cases with and without posterior vitreous detachment, respectively). Conclusion : Subjects with vitreous degeneration have diminished photopic and mesopic contrast thresholds compared with controls. This finding highlights the negative impact of vitreous degeneration on the quality of vision.

Chromatic and flicker threshold changes in age-related macular degeneration following anti-VEGF treatment

ABSTRACT Clinical relevance Red-green chromatic sensitivity and photopic (cone-mediated) flicker sensitivity showed marked improvement after anti-VEGF treatment. The use of flicker and chromatic sensitivities as potential functional tests to monitor treatment outcomes in age-related macular degeneration highlights the clinical importance. Background High-contrast visual acuity (VA) is not a sensitive clinical marker in the management of age-related macular degeneration (AMD). Therefore, flicker and chromatic sensitivity changes were assessed following anti-VEGF treatment in subjects with neovascular AMD. Methods Subjects diagnosed with neovascular AMD were recruited. VA was measured using a COMPlog chart. Flicker (in central 5°) and chromatic thresholds (red-green and yellow-blue) were measured using Flicker-plus test and Colour Assessment and Diagnosis (CAD) tests, respectively. Baseline thresholds and foveal thickness were measured on the same day, just before anti-VEGF injection delivery and 5 weeks ± 5 days later. Results Thirteen subjects (8 males, 5 females) with a mean age of 67.5 ± 8.2 years completed the study. Median VA was not significantly different post-treatment (0.57 logMAR [~6/22: Snellen equivalent], IQR: 0.33) compared to baseline (0.56 logMAR, IQR: 0.33), Wilcoxon matched-pair test, p = 0.55). Median Red-Green thresholds improved significantly post-treatment (22.15 CAD units, IQR: 26.06, n = 9), compared to baseline (24.24 CAD units, IQR: 26.21, p = 0.02). Median photopic and mesopic FMT did not show significant change post treatment compared to baseline (p > 0.01, statistical significance of p-value corrected for multiple comparisons was set to 0.01). Similarly, the foveal thickness was not significantly different at post-treatment visit than baseline (p = 0.53). Conclusion Red/green sensitivity recovered better than yellow/blue sensitivity, thus, providing insight into recovery mechanisms in AMD and usefulness of these tests as clinical markers in the management of AMD.

Flicker fusion thresholds as a clinical identifier of a magnocellular-deficit dyslexic subgroup

The magnocellular-dorsal system is well isolated by high temporal frequency. However, temporal processing thresholds have seldom been explored in developmental dyslexia nor its subtypes. Hence, performances on two, four-alternative forced-choice achromatic flicker fusion threshold tasks modulated at low (5%) and high (75%) temporal contrast were compared in dyslexic and neurotypical children individually matched for age and intelligence (8–12 years, n = 54 per group). As expected, the higher modulation resulted in higher flicker fusion thresholds in both groups. Compared to neurotypicals, the dyslexic group displayed significantly lower ability to detect flicker at high temporal frequencies, both at low and high temporal contrast. Yet, discriminant analysis did not adequately distinguish the dyslexics from neurotypicals, on the basis of flicker thresholds alone. Rather, two distinct dyslexic subgroups were identified by cluster analysis – one characterised by significantly lower temporal frequency thresholds than neurotypicals (referred to as ‘Magnocellular-Deficit’ dyslexics; 53.7%), while the other group (‘Magnocellular-Typical’ dyslexics; 46.3%) had comparable thresholds to neurotypicals. The two dyslexic subgroups were not differentially associated with phonological or naming speed subtypes and showed comparable mean reading rate impairments. However, correlations between low modulation flicker fusion threshold and reading rate for the two subgroups were significantly different (p = .0009). Flicker fusion threshold performances also showed strong classification accuracy (79.3%) in dissociating the Magnocellular-Deficit dyslexics and neurotypicals. We propose that temporal visual processing impairments characterize a previously unidentified subgroup of dyslexia and suggest that measurement of flicker fusion thresholds could be used clinically to assist early diagnosis and appropriate treatment recommendations for dyslexia.

Age-related change in flicker thresholds with rod- and cone-enhanced stimuli.

PurposeRod and cone photoreceptor-specific tests can be time-consuming. A new non-invasive test is described. The test is based on the measurement of flicker modulation thresholds with rod- and cone-enhanced visual stimuli, which requires only minimum adaptation time. Here, we investigated how the rod-and cone-mediated flicker thresholds vary with age.MethodsMonocular thresholds with rod and cone–enhanced stimuli were measured in 140 healthy adults, (age range: 18–75 years), foveally (0°) and at four parafoveal locations, at an eccentricity of 5° in each of the four quadrants using five, adaptive, interleaved staircases. Temporal frequencies, stimulus sizes, background luminance and spectral composition, were adjusted appropriately to achieve approximately 1 log unit separation in sensitivity between the rod- and cone-enhanced stimuli. Spectrally calibrated, ‘neutral density’ filters were used to enable adequate control of display luminance for rod enhanced stimuli.ResultsThe magnitude of central and parafoveal rod thresholds was significantly higher than the central and parafoveal cone thresholds, respectively (p < 0.001) in both the age groups. However, the rate of increase in central rod thresholds (y = 0.45x—12.79; linear regression equation) was not significantly steeper than the rate of increase in central (y = 0.29x—8.53) cone thresholds (p = 0.15). Centrally, cone thresholds showed a better correlation with rod central thresholds for the age > 45 years (Spearman correlation, ρ = 0.74, p < 0.001) compared to age ≤ 45 years (ρ = 0.41, p < 0.001).ConclusionsThresholds with rod- and cone-enhanced stimuli are largely invariant below 45 years of age and increase rapidly above this age. This age-wise normative database can be used as an effective functional-marker to assess photoreceptor sensitivities in retinal diseases.

Age‐related changes in flicker sensitivity with rod‐ and cone‐enhanced stimuli

AbstractPurposeCone and rod photoreceptors are usually isolated using high light levels for cone vision and full dark‐adaptation, when only rods respond to light. Such methods are not ideal for clinical use. A new rod/cone flicker test has been designed to isolate and measure rod‐ and cone‐mediated signals in the absence of colour signals with one minute adaptation.Methods118 healthy adults (Mean age ± standard deviation: 40 ± 15 years), were investigated. None of the participants had a history of or exhibited signs of ocular disease. Rod and cone thresholds were measured monocularly in central vision and in each of the four quadrants (superonasal, superotemporal, inferonasal and inferotemporal) at an eccentricity of 5°. Temporal frequencies, stimulus sizes, background luminances and spectral composition were adjusted appropriately to achieve approximately equal thresholds with ~ 10‐fold separation in sensitivity between the rod‐ and cone‐enhanced stimuli. Flicker thresholds were measured using five adaptive (two‐down, one‐up), interleaved staircases. Spectrally calibrated, ‘neutral density’ glasses were used to enable adequate control of display luminance at low levels.ResultsThe superotemporal quadrant had the lowest mean rod and cone thresholds compared to other tested quadrants. For participants, above 50 years of age, the central rod thresholds increased 0.53% per year, whereas cone thresholds increased 0.29% per year and this decline was faster than other respective quadrants. Overall, among the locations tested, the central rod (ρ = 0.547; p &lt; 0.005) and cone (ρ = 0.504, p &lt; 0.005) thresholds demonstrated the strongest correlation with age.ConclusionsThe new test isolates rod and cone signals sufficiently well to detect selective loss of photoreceptor function in normal ageing. The potential use of rod‐ and cone‐enhanced tests in patients with selective loss of photoreceptors and other retinal diseases (e.g., AMD, glaucoma, diabetes) remains to be explored.

Development and validation of a new glaucoma screening test using temporally modulated flicker.

Describing the psychometric characteristics and diagnostic accuracy of the Accelerator 4-Alternative Forced-Choice Flicker Test prototype (A4FTp) for detecting chronic open angle glaucoma (COAG). A4FTp measures temporally-modulated flicker thresholds in regions of the visual field with high susceptibility to glaucomatous loss. We initially evaluated its psychometric properties on 20 normals (aged 33.8±8.5years) who were tested multiple times over a period of 3months. All subjects underwent four repetitions for shorter (T8) and longer (T12) staircase termination criteria, to determine the most suitable threshold criterion. Four randomly selected subjects underwent a total of 10 repetitions to study test-retest repeatability and learning effects. To determine its diagnostic accuracy, one eye of 40 participants with COAG and 38 normal controls were tested with the A4FTp in comparison with the Frequency Doubling Technology (FDT; C20-5 programme) and iVue Spectral Domain Optical Coherence Tomography (SD-OCT). Tests were conducted in a random order with results masked to the clinician conducting the reference ophthalmic examination. The accuracy of each test was determined by analysis of the area under the receiver operator characteristic curve (AUROC). A4FTp flicker thresholds were stable, with standard deviations of only 0.52decilog (dL) for T8, increasing to 1.32dL for T12, and no significant flicker sensitivity threshold improvement over the 10 repeat runs. T8 was superior to T12 on several other measures, so it was used for the remaining comparisons. In terms of diagnostic accuracy, the mean AUROC for the three tests were A4FTp [T8 criterion; 0.82, 95% confidence interval (0.73-0.92)]; SD-OCT [any RNFL parameter p<1% level; 0.90 (0.83-0.97)]; and FDT [one or more locations missed at p<5% level; 0.91 (0.82-0.96)]. There was no statistical difference in AUROC between A4FTp and SD-OCT (p=0.18) or FDT (p=0.12). The A4FTp test duration averaged just over 2min per eye, taking approximately one-third of the time for completion of the HFA SITA 24-2 algorithm (conducted as part of the reference examination) and twice the time for the suprathreshold FDT. Test accuracy for the A4FTp was comparable to those of the FDT and SD-OCT for the detection of COAG. Time taken to complete the A4FTp was relatively short and initial results are promising. With further refinement, the A4FTp could have a future role in glaucoma detection.

Human Flicker Fusion Correlates With Physiological Measures of Magnocellular Neural Efficiency.

The rapidity with which the visual system can recover from stimulation in order to respond again has important implications for efficiently processing environmental stimuli in real time. To date, there has been little integration of the human psychophysical and physiological research underlying the neural mechanisms contributing to temporal limits on human visual perception. Hence, we investigated the relationship between achromatic flicker fusion frequency and temporal analysis of the magnocellular (M) and parvocellular (P) contributions to the achromatic non-linear multifocal Visual Evoked Potential (mfVEP) responses recorded from occipital scalp (Oz). It was hypothesized, on the basis of higher temporal cut-off frequencies reported for primate M vs. P neurons, that sinusoidal flicker fusion frequencies would negatively correlate with the amplitude of M- but not P-generated non-linearities of the mfVEP. This hypothesis was borne out in 72 typically developing young adults using a four-way forced choice sinusoidal flicker fusion task: amplitudes of all non-linearities that demonstrated a clear M-generated component correlated negatively with flicker thresholds. The strongest of these correlations were demonstrated by the main M non-linearity component (K2.1N70−P100) for both high contrast (r = −0.415, n = 64, p < 0.0005) and low contrast (r = −0.345 n = 63, p < 0.002) conditions, indicating that higher achromatic flicker fusion threshold is linked to a more efficient (smaller second order kernels) M system. None of the peaks related to P activity showed significant correlations. These results establish flicker thresholds as a functional correlate of M-pathway function as can be observed in the non-linear analysis of mfVEP.

Seeing is believing: a demonstration of critical fusion frequency and its multidimensional nature.

critical fusion frequency (CFF), or the flicker fusion threshold, is defined as the critical frequency above which a flickering light source appears steady to the observer (see [Fig. 1][1]). It is known to depend on a number of parameters, namely, intensity of the light source ([5][2], [15][3]),

Flicker Sensitivity in Normal Aging--Monocular Tests of Retinal Function at Photopic and Mesopic Light Levels.

Aging can affect many aspects of visual performance. In general, the effects become more significant in those older than 40 to 50 years, with increased intersubject variability and stronger dependence on ambient illumination. This study aimed to establish how healthy aging of the retina affects the detection of 15-Hz flicker under photopic and mesopic lighting. We investigated 71 participants aged 20 to 75 years. Thresholds were measured for detection of 15-Hz flicker at the fovea (0°) and at an eccentricity of 4° in each of the four quadrants. The background luminance ranged from 0.6 to 60 cd/m(2) and pupil size was measured continuously. Participants were excluded if they had signs/history of ocular disease, substantial interocular differences in flicker thresholds, or were unable to detect 100% flicker modulation in the high mesopic range. Mesopic and photopic flicker thresholds were used to calculate an index, the health of the retina index, to determine the limits of flicker sensitivity in healthy aging. Log flicker thresholds changed bilinearly with age; they remained stable until 40 to 50 years, with a linear decline with increasing age. This bilinear pattern of the change in flicker thresholds with age is consistent across photopic and mesopic light levels. The health of the retina index captures the lowest threshold, usually obtained under photopic conditions, as well as the loss of flicker sensitivity with decreasing light level. The established limits of healthy aging may benefit from future studies in patients with ocular hypertension and/or glaucoma that are known to experience loss of flicker sensitivity.

Nanosecond‐laser application in intermediate AMD: 12‐month results of fundus appearance and macular function

A novel, ultra-low energy nanosecond laser (retinal rejuvenation therapy) has been developed with the aim to slow progression of early age-related macular degeneration (AMD). The safety, changes in fundus characteristics and macular function in a cohort of participants with bilateral intermediate AMD are reported. Prospective non-randomised, pilot intervention study. Subjects with bilateral intermediate AMD (n = 50, aged 50-75 years). Ultra-low energy laser pulses applied in 12 spots around the macula of one eye (0.15-0.45 mJ), using 400 μm diameter spot, 3 nanosecond pulse length, 532 nm wavelength and energy titrated to each patient. Best corrected visual acuity, drusen area and macular sensitivity (flicker perimetry) at baseline and at 3, 6 and 12 months post-laser. Treatment was painless with no clinically visible lesions. No participant developed choroidal neovascularization, while two with thin central retinal thickness at baseline developed atrophy at 12-month follow up. Drusen area was reduced in 44% of treated eyes and 22% of untreated fellow eyes, with changes in drusen and function not being coincident. Improvement in flicker threshold within the central 3° was observed in both the treated and untreated fellow eyes at 3 months post-laser. Of the 11 eyes at greatest risk of progression (flicker defect >15 dB), seven improved sufficiently to be taken out of this high-risk category. A single unilateral application of nanosecond laser to the macula produced bilateral improvements in macula appearance and function. The nanosecond retinal rejuvenation therapy laser warrants ongoing evaluation as an early intervention for AMD.

Macular pigment in ophthalmic practice; a survey

Macular pigment (MP) might provide some protection against age-related eye disease, and it is now being measured in ophthalmic practice. The purpose of the survey described here was to determine the distribution of MP in a random population of patients in a typical UK ophthalmic practice. Macular pigment optical density (MPOD) was measured in 56 patients aged 11 to 87 years, mean 52 ± 19, over a 3-month period. Typically, the test requires setting flicker thresholds for a centrally and peripherally viewed blue/green alternating target. Here we describe the results when an age-based estimate of the peripheral value is used, thus avoiding the peripheral setting. In 32 observers, a comparison was made between this and values obtained with the centre and periphery method. Information on smoking habits, iris colour, diabetic status, and ethnicity were recorded. The overall average MPOD for the population obtained with the centre-only approach for 56 individuals was 0.400 ± 0.165. The centre-only technique was an accurate predictor of values based on centre and peripheral measures, with 95% limits of agreement of 0.137 OD units. Pearson's correlation coefficient showed a high correlation between right and left eyes (r = 0.7 (p < 0.001)). There was a small difference between males and females that did not reach statistical significance (r = -0.22). There was a non-statistically significant age-related decline in MPOD in this particular population (r = -0.17). Dark irides were significantly associated with high MPOD (r = 0.28, p < 0.05). MPOD in Type II diabetic patients was 27% lower than that in non-diabetics (r = 0.29, p < 0.05). The technique provides similar values of MP optical density to previous reports. As with other HFP-based methods, in a small percentage of older patients, more than one measurement is required before satisfactory results are obtained.

Examination of colour vision deficiency in different types retinitis pigmentosa

AbstractPurpose Investigation of the colour vision deficiency in different typees of retinitis pigmentosa (RP): autosomal dominant, autosomal recessive, X‐linked recessive, and isolated cases.Methods Colour vision investigation was conducted on 42 patients (18 women, 24 men) with RP using the Farnsworth 28 HUE‐test, anomaloscope –IF‐2 Tomay, flicker threshold test, standard pseudoisochromatic table and Tritan Lantonie album. The age of the patients varied from 5 to 68 years (mean 39 ± 17, SD),Results In 73,3 % of patients with RP we established acquired colour vision deficiency (dyschromatopsy) . Among the patients with aquired colour vision deficiency we found out using the above‐mentioned tests that 67,8% were with tritanopy, 19,3% were with manifested deuteranomaly and 12,9 % were with protanomaly. The type of dyschromatopsy does not show any relation to the age and visual aquity of patients. When no foveal lesion was apparent in patients with visual acuity better than 20/40, patients with autosomal dominant disease showed superior performance on color vision testing when compared to autosomal recessive, X‐linked recessive, and isolated cases. The Farnsworth 28 HUE test was more sensitive in detecting poor color vision performance than the anomaloscope –IF‐2 Tomay.Conclusion We established a great percentile of patients with RP suffer from colour vision deficiency. Our study reveals that colour vision investigation has an important role in PR diagnosis.

Luminance and Colour Flicker Fusion in High and Low Autistic Traits

Event Abstract Back to Event Luminance and Colour Flicker Fusion in High and Low Autistic Traits Alyse Brown1*, David P. Crewther1, Julia Thompson1, Georgette Karvelas1, Catherine Guarnaccia1, Charlotte Hartwell1 and Claire Peck1 1 Swinburne University, Australia Background Neurophysiological mechanisms underlying altered visual perception in autistic tendencies are currently poorly defined. Differences in magnocellular processing have been implicated in the impaired motion sensitivity and different global/local integration style associated with autistic tendency. Method Flicker fusion tasks were utilised to examine temporal processing differences in a non-clinical population displaying high and low autistic tendencies as measured by Baron-Cohen’s Autism spectrum Quotient (AQ). Isoluminant red/green flicker was used to measure temporal processing capacity of the parvocellular system (2AFC) and similarly, isoluminant blue/yellow flicker used to measure koniocellular pathway function (2AFC). The temporal processing capacity of the magnocellular system was measured as a function of contrast with critical luminance flicker thresholds measured at 5 different temporal contrast levels (5%, 25%, 50%, 75%, 100%) using a 4AFC method. Calibrated LEDs were viewed through 5mm diameter optic fibers, amplitude, DC level and frequencies were modulated using VPixx software via a DataPIXX interface system. Results Data obtained supports previous findings showing critical flicker thresholds improve with increasing contrast levels, from 32Hz at 5% contrast to 47Hz at 100% temporal contrast (correlation R2 =.47, significant to .001). Blue/yellow flicker had a marginally higher mean colour fusion rate (18.3Hz) than the red/green fusion task (16.8 Hz). Between groups analysis shows for all flicker tasks that individuals with high AQ have lower luminance flicker fusion rates then those with low AQ. Discussion The finding that those with higher AQ scores are less able to perceive flicker – especially for luminance modulation at the limits of high frequency, is suggestive of impaired magnocellular function, despite previous reports of insignificant differences in flicker contrast sensitivity. Keywords: temporal processing, autistic traits, Flicker Fusion, Magnocellular, Parvocellular Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Sensation and Perception Citation: Brown A, Crewther DP, Thompson J, Karvelas G, Guarnaccia C, Hartwell C and Peck C (2013). Luminance and Colour Flicker Fusion in High and Low Autistic Traits. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00091 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Sep 2013; Published Online: 25 Nov 2013. * Correspondence: Ms. Alyse Brown, Swinburne University, Melbourne, Australia, amailboxx@hotmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Alyse Brown David P Crewther Julia Thompson Georgette Karvelas Catherine Guarnaccia Charlotte Hartwell Claire Peck Google Alyse Brown David P Crewther Julia Thompson Georgette Karvelas Catherine Guarnaccia Charlotte Hartwell Claire Peck Google Scholar Alyse Brown David P Crewther Julia Thompson Georgette Karvelas Catherine Guarnaccia Charlotte Hartwell Claire Peck PubMed Alyse Brown David P Crewther Julia Thompson Georgette Karvelas Catherine Guarnaccia Charlotte Hartwell Claire Peck Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Visual Function Tests as Potential Biomarkers in Age-Related Macular Degeneration

To evaluate the potential of psychophysical assessments of retinal function to provide diagnostic biomarkers of early age-related macular degeneration (AMD). Unilateral visual function was assessed in 221 participants (72.86 ± 9.94 years; 67% women) with early AMD (visual acuity better than 20/60) and 109 controls (73.07 ± 10.32 years; 65% women). Psychophysical assessment included steady state thresholds (4- and 14-Hz flicker and red and blue color) and dynamic tests (photostress recovery [PSR] and dark adaptation [DA]). All test parameters were compared in terms of their diagnostic capacity (sensitivity and specificity), reproducibility, and clinical applicability (test duration and participant's perception of test difficulty). AMD status was determined by digital photography, according to the International Classification and Grading System. All functional measurements were significantly worse, on average, in the AMD group than in the control group (P < 0.001). Static and dynamic parameters showed weak correlations (range, 0.003-0.225). Rod recovery in DA and cone recovery in PSR had the best diagnostic capacity (area under curve [AUC], receiver operating characteristic [ROC] analysis, 0.93 ± 0.016 and 0.85 ± 0.021, respectively). Considering diagnostic capacity together with test reproducibility and clinical applicability, the 14-Hz flicker gave the best outcome, followed by PSR. Combination of these two tests detected 71% of abnormal early AMD cases. All the visual function tests had good diagnostic capacity. Combination of the 14-Hz flicker thresholds and dynamics of the PSR test provided optimal quantitative assessment of retinal function in early AMD, suggesting that this set is a potentially useful clinical tool for following progression of early AMD and assessing the efficacy of interventions.

Central Retinal Function as Measured by the Multifocal Electroretinogram and Flicker Perimetry in Early Age-Related Macular Degeneration

To determine the retinal function in early age-related macular degeneration (AMD) assessed by the multifocal electroretinogram (mfERG) and flicker perimetry and to seek a relationship between local objective mfERG parameters and subjective flicker perimetry thresholds. mfERG and flicker perimetry were performed in 15 patients (15 eyes) with early AMD and 14 controls (14 eyes) of similar age. The mfERG P1 response amplitude density (nV/deg²) and P1 implicit time of the first-order kernel and the flicker thresholds of each concentric ring were analyzed. The relationship between individual mfERG responses and the corresponding individual flicker sensitivity outcomes was determined. The mfERG response amplitude of the central ring (ring 1) was significantly reduced in early AMD eyes compared with the controls (P = 0.009). No significant difference in mfERG amplitude between early AMD and control eyes was detected in the other rings. The mfERG implicit time was significantly increased in the early AMD eyes but only within the central four rings of 12°. A significant reduction in flicker sensitivity was also detected in early AMD eyes but only within the central 6°. There was a significant, moderate correlation (r = -0.477; P < 0.001) between local mfERG latency and flicker sensitivity from the same tested locations within the central 6°. There was a weak correlation (r = 0.200; P = 0.014) between mfERG amplitude and flicker sensitivity. Both mfERG and flicker perimetry show abnormal retinal function, but only in the very central macula, in early AMD. A novel relationship between mfERG and flicker sensitivity should enhance the clinical monitoring of disease progression.

An evaluation of a novel instrument for measuring macular pigment optical density: the MPS 9000

Of the antioxidants found in the human retina, only the macular carotenoid quantities can be estimated noninvasively (albeit in a collective fashion), thus facilitating study of their role in that tissue. The aim of this study was to evaluate concordance between macular pigment optical density (MPOD) values recorded on a commercially available instrument, the MPS 9000, with those of an already validated heterochromatic flicker photometry instrument. Also, we assessed and compared test-retest variability for each instrument. Macular pigment optical density at 0.5 retinal eccentricity was measured using two different heterochromatic flicker photometers, the MPS 9000 and the Macular Densitometer(TM), in 39 healthy subjects. Test-retest variability was evaluated separately for each instrument by taking three readings over a 1-week period in 25 subjects. There was a moderate positive correlation for MPOD at 0.5° of retinal eccentricity between the MPS 9000 and the Macular Densitometer described by the linear equation y = 0.763x + 0.172 (r = 0.68, p < 0.001, r(2) = 0.46); however, a paired-samples t-test showed a significant difference in terms of mean values, with a bias of lower MPOD values being yielded by the MPS 9000 (t = -4.103, p < 0.001). Bland-Altman analysis indicated only moderate agreement between the two instruments, reflected in 95% limits of agreement of 0.1 ± 0.27. Inter-sessional repeatability, expressed as a coefficient of repeatability, ranged from 0.18 to 0.21 [mean (±SD): 0.19 (0.02)] for the MPS 9000 and from 0.11 to 0.12 [mean (±SD): 0.12 (0.01)] for the Macular Densitometer. The results demonstrate that the MPS 9000 consistently yields MPOD readings, which are lower than that found with the Macular Densitometer, and exhibits substantial test-retest variability.