Recent developments in perimetry: test stimuli and procedures

Standard automated perimetry for glaucoma and diseases of the retina and visual pathways: current and future perspectives

Static automated perimetry (SAP) remains a mainstay of functional assessment of the visual field in diseases of the visual pathway, such as glaucoma and age-related macular degeneration. The fundamental psychophysical task of responding to stimuli of different levels of contrast has remained minimally changed since its inception in the 1980s, and this is potentially the root of several unresolved issues involving the technique. Enduring issues include the optimisation of SAP parameters for maximising defect detection, the influence of subjective behaviour on the response, structure-function discordance, and ageing- and disease-related changes of the visual pathway. Addressing these issues has been a focus of our research program and is the subject of this manuscript. We will review some of the basic psychophysical principles and methods that have contributed to the development of SAP and their contributions to its output measurements. Parameters that are interrogated include stimulus size and background luminance and their modification to improve defect defection in glaucoma and age-related macular degeneration. We propose frameworks for optimising testing parameters and leveraging the results for changing clinical care. In our pursuit of optimising the structure-function relationship in the eye, several areas of research have been developed and explored, including: the reconciliation of subjective responses in perimetry; by minimising sources of biases, such as Method of Limits we have been able to equate static and kinetic perimetry outputs in relation to underlying structural loci. This also formed the basis for our clustering framework, which groups together statistically similar structural and functional test locations to maximise structure-function concordance. Throughout the manuscript, we review the scientific underpinnings of clinical measurements, framing application into real-world patients to improve clinical practice.

Visual Field Tests: A Narrative Review of Different Perimetric Methods

Visual field (VF) testing dates back to fifth century B.C. It plays a pivotal role in the diagnosis, management, and prognosis of retinal and neurological diseases. This review summarizes each of the different VF tests and perimetric methods, including the advantages and disadvantages and adherence to the desired standard diagnostic criteria. The review targets beginners and eye care professionals and includes history and evolution, qualitative and quantitative tests, and subjective and objective perimetric methods. VF testing methods have evolved in terms of technique, precision, user-friendliness, and accuracy. Consequently, some earlier perimetric techniques, often still effective, are not used or have been forgotten. Newer technologies may not always be advantageous because of higher costs, and they may not achieve the desired sensitivity and specificity. VF testing is most often used in glaucoma and neurological diseases, but new objective methods that also measure response latencies are emerging for the management of retinal diseases. Given the varied perimetric methods available, clinicians are advised to select appropriate methods to suit their needs and target disease and to decide on applying simple vs. complex tests or between using subjective and objective methods. Newer, rapid, non-contact, objective methods may provide improved patient satisfaction and allow for the testing of children and the infirm.

Kinetic Perimetry on Virtual Reality Headset

OBJECTIVE

We present a portable automatic kinetic perimeter based on a virtual reality (VR) headset device as an innovative and alternative solution for the screening of clinical visual fields. We compared the performances of our solution with a gold standard perimeter, validating the test on healthy subjects.

METHODS

The system is composed of an Oculus Quest 2 VR headset with a clicker for participant response feedback. An Android app was designed in Unity to generate moving stimuli along vectors, following a standard Goldmann kinetic perimetry approach. Sensitivity thresholds are obtained by moving centripetally three different targets (V/4e, IV/1e, III/1e) along 24 or 12 vectors from an area of non-seeing to an area of seeing and then transmitted wirelessly to a PC. A Python real-time algorithm processes the incoming kinetic results and displays the hill of vision in a two-dimensional map (isopter). We involved 21 subjects (5 males and 16 females, age range 22-73 years) for a total of 42 eyes tested with our proposed solution, and results were compared with a Humphrey visual field analyzer to test reproducibility and efficacy.

RESULTS

isopters generated with the Oculus headset were in good agreement with those acquired with a commercial device (Pearson's correlation values r > 0.83 for each target).

CONCLUSIONS

we demonstrate the feasibility of VR kinetic perimetry by comparing performances between our system and a clinically used perimeter in healthy subjects.

SIGNIFICANCE

proposed device leads the way for a portable and more accessible visual field test, overcoming challenges in current kinetic perimetry practices.

Should clinical automated perimetry be considered for routine functional assessment of early/intermediate age-related macular degeneration (AMD)? A systematic review of current literature

Purpose

There is growing interest in functional testing for early/intermediate age‐related macular degeneration (iAMD). However, systematic evaluation of existing clinical functional tests is lacking. This systematic review examines evidence for using clinical automated perimetry in routine assessment of early/iAMD.

Recent findings

PubMed, Web of Science Core Collection, and Embase were searched from inception to October 2020 to answer, is there evidence of visual field defects in early/iAMD, and if so, are early/iAMD visual field defects linked to real‐world patient outcomes? Articles using clinical automated perimetry (commercially accessible and non‐modified devices/protocols) were included. Microperimetry was excluded as this has yet to be incorporated into clinical guidelines. The primary outcome was global visual field indices including mean deviation (MD), pattern standard deviation (PSD), mean sensitivity (MS) and frequency of defects. The secondary outcome was any real‐world patient outcome including quality of life and/or activities of daily living indices. Twenty‐six studies were eligible for inclusion and all studies were observational. There was consistent evidence of worsened MD, PSD, MS and frequency of defects for early/iAMD compared to normal eyes under photopic, low‐photopic and scotopic conditions. Meta‐analysis of studies using standard automated perimetry (SAP) under photopic conditions revealed worsened MD (−1.52dB [−2.27, −0.78 dB]) and MS (−1.47dB [−2, −0.94 dB]) in early/iAMD compared to normal eyes, representing large statistical effect sizes but non‐clinically meaningful reductions. There was insufficient data for meta‐analyses regarding other clinical automated perimetry protocols. Only one study assessed a real‐world patient outcome (on‐road driving performance), with no significant link to visual field outcomes in early/iAMD.

Summary

Significant reduction of global visual field indices is present in early/iAMD, but not clinically meaningful using SAP under photopic conditions. Translational relevance of visual field outcomes to patient outcomes in early/iAMD remains unclear. Thus, SAP under photopic conditions is unlikely to be useful for routine assessment of early/iAMD.

Influence of ACPA-positive rheumatoid arthritis on visual field testing in patients with arterial hypertension: A comparative cross-sectional study

Purpose

To evaluate a possible influence of anti‐cyclic citrullinated peptide autoantibodies (ACPA) ‐ positive rheumatoid arthritis (RA) on visual field (VF) testing in patients with arterial hypertension (aHT).

Methods

We conducted an observational cross‐sectional study comparing patients with ACPA‐positive RA and aHT, patients with aHT and healthy subjects. Further inclusion criteria were visual acuity (VA) of 0.8 or better and age between 40 and 60 years. VF testing was performed with standard automated achromatic perimetry (SAP), short wavelength automated perimetry (SWAP) (Octopus 300^®) and flicker perimetry (Pulsar^®). Results were analysed for a possible correlation with blood pressure or RA‐activity.

Results

Twenty subjects with RA and aHT, 26 patients with aHT and 22 healthy participants were examined. Significant differences were found for mean sensitivity (MS) in SWAP comparing RA‐patients with healthy participants (ΔMS −3.06, p = 0.001) and with hypertensive patients (ΔMS −2.32, p = 0.007). In SAP we observed a significant difference between patients with RA and healthy subjects regarding loss variance (LV) (ΔLV = +9.77, p = 0.004). Flicker perimetry did not demonstrate significant differences between groups. A correlation of VF changes with blood pressure level or RA‐activity was not observed.

Conclusion

Patients with ACPA‐positive RA and aHT showed significant impairment of VF performance in SWAP compared to patients with aHT alone and healthy subjects. SAP also revealed a significant difference of LV between RA‐patients and healthy subjects. aHT does not seem to induce functional changes in VF testing alone.

Assessment of age‐related maculopathy using subjective vision tests

This paper reviews non-standard, clinical vision tests that may be used to detect the earliest visual loss in age-related maculopathy (ARM), before fundus changes are detected. We recommend a clinical test battery for all patients aged 60 years and older, comprising low luminance/low contrast (SKILL) VA or low contrast VA, desaturated D-15 colour vision assessment, flicker perimetry, glare recovery and dark adaptation if possible, together with conventional assessments of case history, ophthalmoscopy and high contrast visual acuity (VA) for the detection and diagnosis of ARM. Reading rate is also discussed as a potential indicator of early visual loss. For monitoring the progressive visual loss in age-related macular degeneration (AMD) and determining the requirements for optometric vision rehabilitation, we recommend more conventional clinical vision tests of distance and near visual acuity, reading rate, the effects of varying illumination and a functional central visual field assessment.

A Strategy for Seeding Point Error Assessment for Retesting (SPEAR) in Perimetry Applied to Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma

PURPOSE

We sought to determine the impact of seeding point errors (SPEs) as a source of low test reliability in perimetry and to develop a strategy to mitigate this error early in the test.

DESIGN

Cross-sectional study.

METHODS

Visual field test results from 1 eye of 364 patients (77 normal eyes, 178 glaucoma suspect eyes, and 109 glaucoma eyes) were used to develop models for identifying SPE. Two test cohorts (326 undertaking Swedish interactive thresholding algorithm [SITA]-Faster and 327 glaucoma eyes undertaking SITA-Standard) were used to prospectively evaluate the models for identifying SPEs. Global visual field metrics were compared among reliable and unreliable results. Regression models were used to identify factors distinguishing SPEs from non-SPEs. Models were evaluated using receiver operating characteristic (ROC) curves.

RESULTS

In the test cohorts, SITA-Faster produced a higher rate of unreliable visual field results (30%-49.7%) compared with SITA-Standard (10.8%-16.6%). SPEs contributed to most of the unreliable results in SITA-Faster (57.5%-64.9%) compared with gaze tracker deviations accounting for most of the unreliable results in SITA-Standard (40%-77.8%). In SITA-Faster, results with SPEs had worse global indices and more clusters of sensitivity reduction than reliable results. Our best model (using 9 test locations) can identify SPEs with an area under the ROC curve of 0.89.

CONCLUSION

SPEs contribute to a large proportion of unreliable visual field test results, particularly when using SITA-Faster. We propose a useful model for identifying SPEs early in the test that can then guide retesting using both SITA algorithms. We provide a simplified framework for the perimetrist to improve the overall fidelity of the test result.

<p>Retinal Sensitivity Thresholds Obtained Through Easyfield and Humphrey Perimeters in Eyes with Glaucoma: A Cross-Sectional Comparative Study</p>

Objective

To compare global retinal sensitivity thresholds obtained through the Easyfield perimeter (EF) and Humphrey visual field analyzer (HFA).

Design

Observational cross-sectional study.

Participants

Glaucomatous patients and glaucoma suspects enrolled between October 2018 and April 2019.

Materials and Methods

All participants underwent EF (SPARK Precision) and HFA perimetry (SITA-Standard). After inclusion, demographic and ocular data were collected, including measurements of retinal nerve fiber layer (RNFL) thickness obtained from spectral-domain optical coherence tomography (SD-OCT). Global indices (mean deviation, MD; pattern standard deviation, PSD) values were compared between perimeters, and their correlation and agreement were evaluated. We used regression analysis to investigate structure-functional correlations between SD-OCT measurements and MD index of each perimeter.

Results

We investigated 111 eyes from 69 patients. Mean MD (mean difference=1.49dB) and PSD values (mean difference=0.42dB) from the HFA were significantly larger than those from the EF perimeter (p<0.001). There were significant linear correlations between EF-MD and HFA-MD (r=0.56), and EF-PSD and HFA-PSD (r=0.38; p<0.001). We found significant non-linear associations between average RNFL thickness and MD values derived from both EF (R²=0.41) and HFA (R²=0.17) perimeters (p≤0.012). A difference <2dB between EF-MD and HFA-MD was found in 53% of the eyes, while 71% of them had a difference <1dB between EF-PSD and HFA-PSD.

Conclusion

While we found a moderate correlation and a small mean sensitivity difference between test results, EF’s correlation with structural measurements was at least comparable to that of the HFA. Our findings suggest that although these tests should not be used interchangeably, EF SPARK Precision could be used as an alternative for functional assessment in eyes with mild glaucoma.

Ocular findings and growth in 5-year-old preterm children born to mothers with preeclampsia

PURPOSE

To evaluate growth, blood pressure and ophthalmological status in preschool children born preterm to mothers with preeclampsia.

METHODS

In a prospective cohort study, 78 children (34 girls) born preterm without retinopathy of prematurity were examined regarding length/height, weight, head circumference and insulin-like growth factor I (IGF-I) at birth and at 5 years of age. At 5 years, IGF-binding protein 3 and blood pressure were also measured. A detailed ophthalmological examination including ocular dimensions, fundus morphology, visual fields, visual evoked potentials and perceptual visual dysfunction was performed. Children born to preeclamptic mothers (n = 24) were compared to children with non-preeclamptic mothers (n = 54).

RESULTS

Children exposed to preeclampsia had lower weight (p = 0.0002, mean difference -1.46, 95% CI -2.09; -0.83), length (p = 0.013, -1.10, 95% CI -1.92; -0.23) and IGF-I levels (p = 0.0002, -26.0, 95% CI -36.0; -16.1) at birth compared to non-exposed children. At 5 years of age, the preeclamptic group had larger optic cup areas (p = 0.0006, 0.32, 95% CI 0.15; 0.46, in right eye, p = 0.049, 0.18, 95% CI 0.001; 0.35, in left eye). There was no significant difference between the groups regarding other ophthalmological findings or blood pressure. Children with reduced eye motility had lower neonatal IGF-I levels (p = 0.033, 15.5, 95% CI 1.1; 30.3).

CONCLUSION

Preeclampsia was shown to affect growth and IGF-I levels, confirming previous studies. Children exposed to preeclampsia were shown to have larger optic cup areas. Furthermore, lower neonatal IGF-I levels were seen in preterm children with reduced eye motility at 5 years of age.

A novel Bayesian adaptive method for mapping the visual field

Measuring visual functions such as light and contrast sensitivity, visual acuity, reading speed, and crowding across retinal locations provides visual-field maps (VFMs) that are extremely valuable for detecting and managing eye diseases. Although mapping light sensitivity is a standard glaucoma test, the measurement is often noisy (Keltner et al., 2000). Mapping other visual functions is even more challenging. To improve the precision of light-sensitivity mapping and enable other VFM assessments, we developed a novel hybrid Bayesian adaptive testing framework, the qVFM method. The method combines a global module for preliminary assessment of the VFM's shape and a local module for assessing individual visual-field locations. This study validates the qVFM method in measuring light sensitivity across the visual field. In both simulation and psychophysics studies, we sampled 100 visual-field locations (60° × 60°) and compared the performance of qVFM with the qYN procedure (Lesmes et al., 2015) that measured light sensitivity at each location independently. In the simulations, a simulated observer was tested monocularly for 1,000 runs with 1,200 trials/run, to compare the accuracy and precision of the two methods. In the experiments, data were collected from 12 eyes (six left, six right) of six human subjects. Subjects were cued to report the presence or absence of a target stimulus, with the luminance and location of the target adaptively selected in each trial. Both simulations and a psychological experiment showed that the qVFM method can provide accurate, precise, and efficient mapping of light sensitivity. This method can be extended to map other visual functions, with potential clinical signals for monitoring vision loss, evaluating therapeutic interventions, and developing effective rehabilitation for low vision.

Clinical Evaluation of Swedish Interactive Thresholding Algorithm-Faster Compared With Swedish Interactive Thresholding Algorithm-Standard in Normal Subjects, Glaucoma Suspects, and Patients With Glaucoma

PURPOSE

To compare the visual fields results obtained using the Swedish interactive thresholding algorithm-Standard (SS) and the Swedish interactive thresholding algorithm-Faster (SFR) in normal subjects, glaucoma suspects, and patients with glaucoma and to quantify potential time-saving benefits of the SFR algorithm.

DESIGN

Prospective, cross-sectional study.

METHODS

One randomly selected eye from 364 patients (77 normal subjects, 178 glaucoma suspects, and 109 patients with glaucoma) seen in a single institution underwent testing using both SS and SFR on the Humphrey Field Analyzer. Cumulative test time using each algorithm was compared after accounting for different rates of test reliability. Pointwise and cluster analysis was performed to determine whether there were systematic differences between algorithms.

RESULTS

Using SFR had a greater rate of unreliable results (29.3%) compared with SS (7.7%, P < .0001). This was mainly because of high false positive rates and seeding point errors. However, modeled test times showed that using SFR could obtain a greater number of reliable results within a shorter period of time. SFR resulted in higher sensitivity values (on average 0.5 dB for patients with glaucoma) that was greater under conditions of field loss (<19 dB). Cluster analysis showed no systematic patterns of sensitivity differences between algorithms.

CONCLUSIONS

After accounting for different rates of test reliability, SFR can result in significant time savings compared with SS. Clinicians should be cognizant of false positive rates and seeding point errors as common sources of error for SFR. Results between algorithms are not directly interchangeable, especially if there is a visual field deficit <19 dB.

Spatial Distribution of Eye-Movements After Central Vision Loss is Consistent with an Optimal Visual Search Strategy

The problem of gaze allocation has previously been studied in the framework of eye-movement control models, which require prior knowledge of visibility maps (VMs). These encode the signal-to-noise ratio, at each point in the visual field, which can be used to define an optimal policy of gaze allocation. However, it is not always possible to estimate the VM, in a given experimental setting, as it depends on many factors, including the visual system of the individual observer. Hence, few eye-movement datasets include the corresponding VM estimates. This can be problematic for the analysis of certain clinical conditions, such as Age-related Macular Degeneration (AMD), which are associated with reduced sensitivity in the affected locations of the visual field. The corresponding VMs are highly idiosyncratic, and cannot be modeled by estimates obtained from healthy observers. We propose an algorithm for maximum likelihood VM estimation, working directly from eye-movement sequences. We apply this algorithm to two eye-tracking datasets, based on visual search tasks, obtained from AMD patients. We show that the inferred VMs are spatially consistent with the measured visual field sensitivities. We also show that simulations with the estimated VMs can account for the asymmetric distribution of saccade vectors, which is typical of AMD patients.

Retinal nerve fibre and ganglion cell inner plexiform layer analysis by optical coherence tomography in asymptomatic empty sella patients

Purpose: To investigate the clinical importance of the thicknesses of the retinal nerve fibre (RNFL) and ganglion cell and inner plexiform layer (GCL+) by spectral domain optic coherence tomography (SD-OCT) in asymptomatic empty sella (ES) patients.Materials and methods: In this cross-sectional, non-randomized prospective study, 44 ES patients and 74 age- and sex-matched healthy individuals were evaluated. All the patients and controls competed an automated 30-2 visual field (VF) test. The mean deviation (MD), pattern standard deviation (PSD), RNFL, and GCL + thickness values obtained with SD-OCT were compared statistically between the two groups.Results: No marked VF defects were found in either group, and there was no statistically significant between-group difference in MD or PSD values. In terms of RNFL thickness, the average and superior quadrant RNFL values of the ES patients were thinner than those of the controls, with statistical significance (p = 0.013 and p = 0.043, respectively). Although other measured RNFL quadrant thicknesses and foveal thickness (FT), macular volume (MV), and average macular thickness (AMT) values were reduced in the ES group, these differences were not statistically significant. The average GCL + value and GCL + values in six sectors in the patient group were significantly lower than those in the control group.Conclusions: Asymptomatic ES patients have a risk of primary ES syndrome and should be followed up using a multidisciplinary approach. Objective and quantitative RNFL and GCL + thickness measurements obtained with OCT can provide valuable data for monitoring these patients.

The Brentano Illusion Test (BRIT): An implicit task of perceptual processing for the assessment of visual field defects in neglect patients

In brain damaged patients with unilateral spatial neglect (USN), the differential diagnosis between the presence and absence of a unilateral visual half-field deficit (VHFD) is hampered by the similarity of their phenomenology. The absence of stimuli detection in the contralateral visual field, indeed, can be due to the co-occurrence of USN and VHFD or the sole presence of the USN. The disentangling of the two conditions is required to devise more specific rehabilitation programmes. Daini et al. [2002. Exploring the syndrome of spatial unilateral neglect through an illusion of length. Experimental Brain Research, 144(2), 224-237.] reported a difference in performance for the two conditions when the tasks required the bisection of Brentano illusory stimuli. Only when USN and VHFD co-occurred, the leftward illusory effect was disrupted. Based on previous findings, in this cross-sectional study, we developed the Brentano Illusion Test (BRIT), a clinical tool that helps the identification of VHFD in USN patients. The BRIT is a simple behavioural test of line bisection aimed at verifying the presence or absence of implicit processing in USN and thus helping the diagnosis of VHFD in USN patients; it also provides normative data for the line bisection task and the length effect.

Ocular dysfunctions and toxicities induced by antiepileptic medications: Types, pathogenic mechanisms, and treatment strategies

INTRODUCTION

Ocular dysfunctions and toxicities induced by antiepileptic drugs (AEDs) are rarely reviewed and not frequently received attention by treating physicians compared to other adverse effects (e.g. endocrinologic, cognitive and metabolic). However, some are frequent and progressive even in therapeutic concentrations or result in permanent blindness. Although some adverse effects are non-specific, others are related to the specific pharmacodynamics of the drug. Areas covered: This review was written after detailed search in PubMed, EMBASE, ISI web, SciELO, Scopus, and Cochrane Central Register databases (from 1970 to 2019). It summarized the reported ophthalmologic adverse effects of the currently available AEDs; their risks and possible pathogenic mechanisms. They include ocular motility dysfunctions, retinopathy, maculopathy, glaucoma, myopia, optic neuropathy, and impaired retinal vascular autoregulation. In general, ophthalmo-neuro- or retino-toxic adverse effects of AEDs are classified as type A (dose-dependent), type B (host-dependent or idiosyncratic) or type C which is due to the cumulative effect from long-term use. Expert opinion: Ocular adverse effects of AEDs are rarely reviewed although some are frequent or may result in permanent blindness. Increasing knowledge of their incidence and improving understanding of their risks and pathogenic mechanisms are crucial for monitoring, prevention, and management of patients' at risk.

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

PURPOSE

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).

METHODS

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 ± 8.5 years) who were tested multiple times over a period of 3 months. 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).

RESULTS

A4FTp flicker thresholds were stable, with standard deviations of only 0.52 decilog (dL) for T8, increasing to 1.32 dL 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 2 min 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.

CONCLUSION

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.

Critical Flicker Fusion Frequency: A Marker of Cerebral Arousal During Modified Gravitational Conditions Related to Parabolic Flights

In situ evaluation of human brain performance and arousal remains challenging during operational circumstances, hence the need for a rapid, reliable and reproducible tool. Here we hypothesized that the Critical flicker fusion frequency (CFFF) reflecting/requiring visual integration, visuo-motor skills and decision-taking process might be a powerful, fast and simple tool in modified gravity environments. Therefore 11 male healthy volunteers were assessed for higher cognitive functions with CFFF during parabolic flights. They were assessed at different time points: upon arrival to the base, 30 min after subcutaneous scopolamine administration, before parabolas, during hypergravity and microgravity at break time (between the 16th and the 17th parabola), on the return flight and on the ground after landing. First, a stable, and consistent measurement of CFFF could be obtained within 12 s. Second, under modified gravitational conditions, the perceptual ability of participants is significantly modified. Compared to the baseline, evolution is characterized by a significant increase of CFFF when in microgravity (0g: 106.9 ± 5.5%), and a significant decrease of CFFF while in hypergravity (2g: 94.5 ± 3.8%). Other time-points were not statistically different from the baseline value. Although the underlying mechanism is still debated, we suggest that the CFFF test is a global marker of cerebral arousal as the result of visuo-motor and decision taking testing based on a simple visual stimulus with an uncomplicated set up that could be used under various environmental conditions. The authors express an opinion that it would be advisable to introduce CFFF measurement during spaceflights as it allows individual longitudinal assessment of individual ability even under conditions of incomplete physiological compensation, as shown here during parabolic flights.

Reducing Spatial Uncertainty Through Attentional Cueing Improves Contrast Sensitivity in Regions of the Visual Field With Glaucomatous Defects

Purpose

Current clinical perimetric test paradigms present stimuli randomly to various locations across the visual field (VF), inherently introducing spatial uncertainty, which reduces contrast sensitivity. In the present study, we determined the extent to which spatial uncertainty affects contrast sensitivity in glaucoma patients by minimizing spatial uncertainty through attentional cueing.

Methods

Six patients with open-angle glaucoma and six healthy subjects underwent laboratory-based psychophysical testing to measure contrast sensitivity at preselected locations at two eccentricities (9.5° and 17.5°) with two stimulus sizes (Goldmann sizes III and V) under different cueing conditions: 1, 2, 4, or 8 points verbally cued. Method of Constant Stimuli and a single-interval forced-choice procedure were used to generate frequency of seeing (FOS) curves at locations with and without VF defects.

Results

At locations with VF defects, cueing minimizes spatial uncertainty and improves sensitivity under all conditions. The effect of cueing was maximal when one point was cued, and rapidly diminished when more points were cued (no change to baseline with 8 points cued). The slope of the FOS curve steepened with reduced spatial uncertainty. Locations with normal sensitivity in glaucomatous eyes had similar performance to that of healthy subjects. There was a systematic increase in uncertainty with the depth of VF loss.

Conclusions

Sensitivity measurements across the VF are negatively affected by spatial uncertainty, which increases with greater VF loss. Minimizing uncertainty can improve sensitivity at locations of deficit.

Translational Relevance

Current perimetric techniques introduce spatial uncertainty and may therefore underestimate sensitivity in regions of VF loss.

Visual field examination method using virtual reality glasses compared with the Humphrey perimeter

Purpose

To present a visual field examination method using virtual reality glasses and evaluate the reliability of the method by comparing the results with those of the Humphrey perimeter.

Materials and methods

Virtual reality glasses, a smartphone with a 6 inch display, and software that implements a fast-threshold 3 dB step staircase algorithm for the central 24° of visual field (52 points) were used to test 20 eyes of 10 patients, who were tested in a random and consecutive order as they appeared in our glaucoma department. The results were compared with those obtained from the same patients using the Humphrey perimeter.

Results

High correlation coefficient (r=0.808, P<0.0001) was found between the virtual reality visual field test and the Humphrey perimeter visual field.

Conclusion

Visual field examination results using virtual reality glasses have a high correlation with the Humphrey perimeter allowing the method to be suitable for probable clinical use.

The value of visual field testing in the era of advanced imaging: clinical and psychophysical perspectives

White‐on‐white standard automated perimetry (SAP) is widely used in clinical and research settings for assessment of contrast sensitivity using incremental light stimuli across the visual field. It is one of the main functional measures of the effect of disease upon the visual system. SAP has evolved over the last 40 years to become an indispensable tool for comprehensive assessment of visual function. In modern clinical practice, a range of objective measurements of ocular structure, such as optical coherence tomography, have also become invaluable additions to the arsenal of the ophthalmic examination. Although structure‐function correlation is a highly desirable determinant of an unambiguous clinical picture for a patient, in practice, clinicians are often faced with discordance of structural and functional results, which presents them with a challenge. The construction principles behind the development of SAP are used to discuss the interpretation of visual fields, as well as the problem of structure‐function discordance. Through illustrative clinical examples, we provide useful insights to assist clinicians in combining a range of clinical results obtained from SAP and from advanced imaging techniques into a coherent picture that can help direct clinical management.

Comparison of Compass and Humphrey Perimeters in Detecting Glaucomatous Defects

Purpose

To compare the performance of Compass fundus automated perimetry (FAP) and Humphrey Field Analyzer (HFA) in glaucoma patients.

Methods

A total of 120 patients with glaucoma underwent 1 FAP and 1 HFA perimetric test over the central 24° on one eye. The chosen eye and sequence were randomized and only reliable examinations were considered for analysis. Mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and the area of absolute scotoma were compared between perimeters. Glaucoma Staging System (GSS2) data were analyzed by means of k test.

Results

Mean sensitivity difference (FAP-HFA) was −1.0 ± 2.81 dB (p<0.001, 95% confidence interval [CI] −1.61, −0.60 dB), MD difference was +0.27 ± 2.84 dB (p = 0.36, 95% CI −5.30, 5.83 dB), PSD difference was +0.48 ± 1.95 dB (p = 0.0075, 95% CI −3.37, 4.33 dB), and VFI difference was +2.4% ± 8.4% (p = 0.003, 95% CI −14.0%, +18.8% dB). Weighted kappa for GSS2 was 0.87. Points with null sensitivities were 9.9 ± 10.2 with FAP and 8.2 ± 8.9 with HFA (difference: 1.7 ± 4.0 points, p = 0.013).

Conclusions

Mean sensitivity with FAP is 1 dB lower than HFA, a finding due to different threshold strategies. Differences of global indices for FAP and HFA are small, which makes the 2 perimeters equivalent in the clinical setting. However, FAP seems more severe in evaluating glaucomatous damage, with absolute scotoma areas larger than with HFA. We raise the hypothesis that such difference may be the result of the active compensation of eye movements available with FAP.

Combining Frequency Doubling Technology Perimetry and Scanning Laser Polarimetry for Glaucoma Detection

PURPOSE

To determine the ability of frequency doubling technology (FDT) and scanning laser polarimetry with variable corneal compensation (GDx-VCC) to detect glaucoma when used individually and in combination.

METHODS

One hundred ten normal and 114 glaucomatous subjects were tested with FDT C-20-5 screening protocol and the GDx-VCC. The discriminating ability was tested for each device individually and for both devices combined using GDx-NFI, GDx-TSNIT, number of missed points of FDT, and normal or abnormal FDT. Measures of discrimination included sensitivity, specificity, area under the curve (AUC), Akaike's information criterion (AIC), and prediction confidence interval lengths.

RESULTS

For detecting glaucoma regardless of severity, the multivariable model resulting from the combination of GDx-TSNIT, number of abnormal points on FDT (NAP-FDT), and the interaction GDx-TSNIT×NAP-FDT (AIC: 88.28, AUC: 0.959, sensitivity: 94.6%, specificity: 89.5%) outperformed the best single-variable model provided by GDx-NFI (AIC: 120.88, AUC: 0.914, sensitivity: 87.8%, specificity: 84.2%). The multivariable model combining GDx-TSNIT, NAP-FDT, and interaction GDx-TSNIT×NAP-FDT consistently provided better discriminating abilities for detecting early, moderate, and severe glaucoma than the best single-variable models.

CONCLUSIONS

The multivariable model including GDx-TSNIT, NAP-FDT, and the interaction GDx-TSNIT×NAP-FDT provides the best glaucoma prediction compared with all other multivariable and univariable models. Combining the FDT C-20-5 screening protocol and GDx-VCC improves glaucoma detection compared with using GDx or FDT alone.

Retinal nerve fiber bundle tracing and analysis in human eye by polarization sensitive OCT

We present a new semi-automatic processing method for retinal nerve fiber bundle tracing based on polarization sensitive optical coherence tomography (PS-OCT) data sets. The method for tracing is based on a nerve fiber orientation map that covers the fovea and optic nerve head (ONH) regions. In order to generate the orientation map, two types of information are used: optic axis orientation based on polarization data, and complementary information obtained from nerve fiber layer (NFL) local thickness variation to reveal fiber bundle structures around the fovea. The corresponding two orientation maps are fused into a combined fiber orientation map. En face maps of NFL retardation, thickness, and unit-depth-retardation (UDR, equivalent to birefringence) are transformed into "along-trace" maps by using the obtained traces of the nerve fiber bundles. The method is demonstrated in the eyes of healthy volunteers, and as an example of further analyses utilizing this method, maps illustrating the gradients of NFL retardation, thickness, and UDR are demonstrated.

A matter of time: improvement of visual temporal processing during training-induced restoration of light detection performance

The issue of how basic sensory and temporal processing are related is still unresolved. We studied temporal processing, as assessed by simple visual reaction times (RT) and double-pulse resolution (DPR), in patients with partial vision loss after visual pathway lesions and investigated whether vision restoration training (VRT), a training program designed to improve light detection performance, would also affect temporal processing. Perimetric and campimetric visual field tests as well as maps of DPR thresholds and RT were acquired before and after a 3 months training period with VRT. Patient performance was compared to that of age-matched healthy subjects. Intact visual field size increased during training. Averaged across the entire visual field, DPR remained constant while RT improved slightly. However, in transition zones between the blind and intact areas (areas of residual vision) where patients had shown between 20 and 80% of stimulus detection probability in pre-training visual field tests, both DPR and RT improved markedly. The magnitude of improvement depended on the defect depth (or degree of intactness) of the respective region at baseline. Inter-individual training outcome variability was very high, with some patients showing little change and others showing performance approaching that of healthy controls. Training-induced improvement of light detection in patients with visual field loss thus generalized to dynamic visual functions. The findings suggest that similar neural mechanisms may underlie the impairment and subsequent training-induced functional recovery of both light detection and temporal processing.

Testing of visual field with virtual reality goggles in manual and visual grasp modes

Automated perimetry is used for the assessment of visual function in a variety of ophthalmic and neurologic diseases. We report development and clinical testing of a compact, head-mounted, and eye-tracking perimeter (VirtualEye) that provides a more comfortable test environment than the standard instrumentation. VirtualEye performs the equivalent of a full threshold 24-2 visual field in two modes: (1) manual, with patient response registered with a mouse click, and (2) visual grasp, where the eye tracker senses change in gaze direction as evidence of target acquisition. 59 patients successfully completed the test in manual mode and 40 in visual grasp mode, with 59 undergoing the standard Humphrey field analyzer (HFA) testing. Large visual field defects were reliably detected by VirtualEye. Point-by-point comparison between the results obtained with the different modalities indicates: (1) minimal systematic differences between measurements taken in visual grasp and manual modes, (2) the average standard deviation of the difference distributions of about 5 dB, and (3) a systematic shift (of 4-6 dB) to lower sensitivities for VirtualEye device, observed mostly in high dB range. The usability survey suggested patients' acceptance of the head-mounted device. The study appears to validate the concepts of a head-mounted perimeter and the visual grasp mode.

Towards Patient-Tailored Perimetry: Automated Perimetry Can Be Improved by Seeding Procedures With Patient-Specific Structural Information

PURPOSE

To explore the performance of patient-specific prior information, for example, from structural imaging, in improving perimetric procedures.

METHODS

Computer simulation was used to determine the error distribution and presentation count for Structure-Zippy Estimation by Sequential Testing (ZEST), a Bayesian procedure with prior distribution centered on a threshold prediction from structure. Structure-ZEST (SZEST) was trialled for single locations with combinations of true and predicted thresholds between 1 to 35 dB, and compared with a standard procedure with variability similar to Swedish Interactive Thresholding Algorithm (SITA) (Full-Threshold, FT). Clinical tests of glaucomatous visual fields (n = 163, median mean deviation -1.8 dB, 90% range +2.1 to -22.6 dB) were also compared between techniques.

RESULTS

For single locations, SZEST typically outperformed FT when structural predictions were within ± 9 dB of true sensitivity, depending on response errors. In damaged locations, mean absolute error was 0.5 to 1.8 dB lower, SD of threshold estimates was 1.2 to 1.5 dB lower, and 2 to 4 (29%-41%) fewer presentations were made for SZEST. Gains were smaller across whole visual fields (SZEST, mean absolute error: 0.5 to 1.2 dB lower, threshold estimate SD: 0.3 to 0.8 dB lower, 1 [17%] fewer presentation). The 90% retest limits of SZEST were median 1 to 3 dB narrower and more consistent (interquartile range 2-8 dB narrower) across the dynamic range than those for FT.

CONCLUSION

Seeding Bayesian perimetric procedures with structural measurements can reduce test variability of perimetry in glaucoma, despite imprecise structural predictions of threshold.

TRANSLATIONAL RELEVANCE

Structural data can reduce the variability of current perimetric techniques. A strong structure-function relationship is not necessary, however, structure must predict function within ±9 dB for gains to be realized.

The Tölz Temporal Topography Study: mapping the visual field across the life span. Part I: the topography of light detection and temporal-information processing

Temporal performance parameters vary across the visual field. Their topographical distributions relative to each other and relative to basic visual performance measures and their relative change over the life span are unknown. Our goal was to characterize the topography and age-related change of temporal performance. We acquired visual field maps in 95 healthy participants (age: 10-90 years): perimetric thresholds, double-pulse resolution (DPR), reaction times (RTs), and letter contrast thresholds. DPR and perimetric thresholds increased with eccentricity and age; the periphery showed a more pronounced age-related increase than the center. RT increased only slightly and uniformly with eccentricity. It remained almost constant up to the age of 60, a marked change occurring only above 80. Overall, age was a poor predictor of functionality. Performance decline could be explained only in part by the aging of the retina and optic media. In Part II, we therefore examine higher visual and cognitive functions.

Peripheral vision and pattern recognition: a review

We summarize the various strands of research on peripheral vision and relate them to theories of form perception. After a historical overview, we describe quantifications of the cortical magnification hypothesis, including an extension of Schwartz's cortical mapping function. The merits of this concept are considered across a wide range of psychophysical tasks, followed by a discussion of its limitations and the need for non-spatial scaling. We also review the eccentricity dependence of other low-level functions including reaction time, temporal resolution, and spatial summation, as well as perimetric methods. A central topic is then the recognition of characters in peripheral vision, both at low and high levels of contrast, and the impact of surrounding contours known as crowding. We demonstrate how Bouma's law, specifying the critical distance for the onset of crowding, can be stated in terms of the retinocortical mapping. The recognition of more complex stimuli, like textures, faces, and scenes, reveals a substantial impact of mid-level vision and cognitive factors. We further consider eccentricity-dependent limitations of learning, both at the level of perceptual learning and pattern category learning. Generic limitations of extrafoveal vision are observed for the latter in categorization tasks involving multiple stimulus classes. Finally, models of peripheral form vision are discussed. We report that peripheral vision is limited with regard to pattern categorization by a distinctly lower representational complexity and processing speed. Taken together, the limitations of cognitive processing in peripheral vision appear to be as significant as those imposed on low-level functions and by way of crowding.

Rarebit perimetry: normative values and test-retest variability

BACKGROUND

We aim to establish normative values and evaluate test-retest variability for the central and foveal field tests of version 4 of rarebit perimetry.

DESIGN

This was a prospective study undertaken in collaboration between Tan Tock Seng Hospital, Singapore, and Singapore Polytechnic.

PARTICIPANTS

Fifty-four normal subjects were recruited and included in the study.

METHODS

Subjects underwent rarebit perimetry testing, studying the central and foveal fields. All subjects repeated the test within 1 month of the initial visit. The 'mean hit rates' of one eye of every subject were analysed.

MAIN OUTCOME MEASURES

Mean hit rates of subjects were analysed to establish normative values for the central and foveal fields. Test-retest variability was also analysed.

RESULTS

Overall normative mean hit rates were 86.3 ± 13.95% for the central field and 91.6 ± 6.35% for the foveal field. For every increasing year of age, we found a 0.47% decrease in the central mean hit rates (P < 0.001). Normative mean hit rate for central and foveal fields were 90.6 ± 12.3% and 98.2 ± 3.7% respectively, in 'young' subjects, and 81.9 ± 15.6% and 85.0 ± 9.0% respectively, in 'mature' subjects. We found no significant test-retest variability in the foveal field (P = 0.554). There was significant test-retest variability in the central field (P < 0.001), but the difference was a 3.5 unit mean hit rate increase, which may be clinically significant.

CONCLUSIONS

Rarebit perimetry is repeatable and reliable. We have established normative values for two age groups.

Time will tell: deficits of temporal information processing in patients with visual field loss

Visual field loss after brain lesions is commonly determined using perimetric tests of light detection (perimetry). Many patients with visual field defects complain about perceptual difficulties in areas that are perimetrically normal. To look at a potential cause for such difficulties, we topographically determined temporal characteristics of visual information processing in those patients and compared them to those of healthy subjects. In nine patients with visual field loss we measured thresholds of double-pulse resolution (DPR), i.e., the minimum perceivable duration of a temporal gap between two light pulses, at eccentricities up to 20°. Furthermore, high-resolution maps of visual reaction times (RT) were obtained in a computer-based campimetric test. Performance was compared to healthy controls from a cross-sectional study of temporal perception across the life span (Toelz Temporal Topography Study). Compared to healthy subjects, DPR thresholds and RTs in patients are elevated in the entire visual field, including areas that are perimetrically intact. Performance on temporal variables depends on the degree of intactness of the respective visual field position. DPR thresholds correlate considerably with RTs, and both parameters increase with eccentricity. However, whereas DPR thresholds are increased around blind regions relative to the intact field, this is not the case for RTs. Temporal processing in patients with cerebral vision loss is impaired to a certain extent independently from perimetric light detection performance. This may partly explain reported subjective perceptual problems. The findings may have important implications for visual rehabilitation, i.e., the potential generalization of light detection training to temporal processing performance.

The relationship between Rarebit perimetry and OCT-derived retinal nerve fibre layer thickness in glaucoma

PURPOSE

To examine the association between measures of neuroretinal matrix integrity as determined with Rarebit perimetry and optical coherence tomography (OCT)-derived retinal nerve fibre layer thickness.

METHODS

One randomly selected eye of 30 White primary open-angle glaucoma patients (age: 60.9 +/- 11.7 years; MD: -3.2 +/- 5.1 dB) and 16 healthy White individuals (age: 33.2 +/- 6.4 years; MD: -0.8 +/- 0.8 dB) were included in the study. Participants underwent Rarebit perimetry testing (central field, software version 4) and an OCT fast retinal nerve fibre layer (RNFL) scan. Correlation was investigated between hemifield Rarebit scores and the corresponding RNFL values, as well as between global Rarebit scores and the respective RNFL measures.

RESULTS

Statistically significant correlations of average hit rate (HR) < 90 and mean hit rate (MHR) were detected with Max-Min and average thickness (Pearson's r ranging from 0.393 to 0.474). Number HR < 90 showed a moderate correlation only with Max-Min (r = -0.396, P = 0.030). Regarding the association between hemifield hit rates and the corresponding OCT thickness parameters, only inferior maximum correlated moderately with HR superior (r = 0.385, P = 0.035). A tendency was detected for the relationship of superior maximum with HR inferior (r = 0.345, P = 0.062). For the control group, no significant correlation was found for any of the global or hemifield indices and the corresponding thickness values.

CONCLUSION

Although Rarebit perimetry is based on a physiological principle distinctly different from conventional perimetry, it provides global indicators of neuroretinal matrix integrity that correlate with some OCT-derived RNFL thickness measures.

A new visual field test in empty sella syndrome: rarebit perimetry

PURPOSE

Several visual field defects can be seen in empty sella syndrome (ESS). In this study, the authors aimed to evaluate the visual field defects in patients with ESS by rarebit perimetry and to compare the results with Humphrey perimetry.

METHODS

Left eyes of 13 patients with ESS and left eyes of 15 age-matched normal subjects were included in the study. Visual field testing was performed by Humphrey Visual Field Analyzer II (Fastpack 30-2 strategy) and rarebit perimetry (regular test). Statistical analysis was performed by independent-samples t-test, Mann-Whitney U test, receiver operating characteristic (ROC) curves, and Pearson correlation test.

RESULTS

Humphrey perimetry mean deviation was -3.67 dB in control group and -6.06 dB in patients with ESS (p=0.12). Mean hit rate calculated by rarebit test was 91.8% in control group and 75.9% in cases with ESS (p=0.005). Area under ROC curve was 0.756 for Humphrey visual field test and 0.827 for rarebit hit rate (p=0.59). There was a significant correlation between rarebit hit rate and Humphrey visual field test mean deviation (r=0.755, p<0.001).

CONCLUSIONS

Rarebit perimetry correlates significantly with Humphrey perimeter in detecting visual field defects related with ESS and has a higher sensitivity and specificity.

Visual fields in children with attention-deficit / hyperactivity disorder before and after treatment with stimulants

PURPOSE

This study aimed to evaluate visual function in children with attention-deficit/hyperactivity disorder (ADHD), to correlate these data with the morphology of the optic nerve, and to find out if and how psychostimulant medication affects visual functions.

METHODS

The visual acuity (VA) and visual fields (VFs) of 18 children with ADHD (two girls and 16 boys), aged 6-17 years, were examined before and after treatment with psychostimulants. A control group, consisting of 24 children (nine girls and 15 boys), aged 7-18 years, were examined twice to evaluate the repeatability of the tests and the learning effect. Fundus photographs were analysed by digital planimetry.

RESULTS

Visual acuity increased significantly (p = 0.0039) in the ADHD group after treatment. The difference between the two VF examinations was significantly larger in the ADHD group compared with the control group (p = 0.036). Significantly more ADHD subjects had subnormal VF results without stimulants, compared with controls (p = 0.0043), but with stimulants the difference was no longer significant.

CONCLUSIONS

Children with ADHD showed better VA and VF results with than without psychostimulant medication.

Perception of very small visual stimuli in the fovea: normative data for the Rarebit Foveal Test

BACKGROUND

Conventional visual tests are not sensitive enough to detect low degree neural damage, as 6/6 (1.0) visual acuity can be upheld with less than two-thirds of the normal number of optic nerve axons. The aim of the current study was to evaluate the physiologic properties of a new computerised test, the Rarebit Fovea Test (RFT), using very small stimuli, by quantifying the effect of age and binocular summation in relation to stimulus luminance.

METHODS

The RFT relies on the perception of very small (less than 0.5 minutes of arc) bright stimuli. Two different experiments were performed. 1. Thirty-five subjects (age 19 to 63 years) were tested with five different stimulus luminances, 158, 64, 53, 41 and 33 cd/m(2). 2. Nineteen subjects (age 19 to 63 years) were tested using binocular stimulation to define the binocular summation.

RESULTS

Significantly reduced median hit rates were observed at luminances of 53 cd/m(2) or below. Age and mean hit rate correlated negatively at all luminance levels below 158 cd/m(2). The mean hit rate from binocular stimulation, compared to the highest value from monocular stimulation in the same subject, was increased by a factor of 1.54 +/- 0.45 (SD). No age effect was found regarding binocular summation.

CONCLUSIONS

The results in the current study indicate that RFT can identify some of the well-known features of the visual system, that is, the effects of age and binocular summation, provided that the stimulus luminance is adequately selected.