Lens rim artifact in automated threshold perimetry

Comparison of Structural and Functional Features in Primary Angle Closure and Open Angle Glaucomas

PRCIS

Using a large data set, we showed structural and functional differences between primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG). Primary angle closure glaucoma has relative structural preservation and worse functional loss inferiorly.

PURPOSE

To identify structural and functional differences in PACG and POAG.

MATERIALS AND METHODS

In this large cross-sectional study, differences in structural and functional damage were assessed among patients with POAG and PACG with optical coherence tomography and reliable visual field testing.

RESULTS

In all, 283 patients with PACG and 4110 patients with POAG were included. Despite similar mean deviation on visual fields (mean [SD] -7.73 [7.92] vs. -7.53 [6.90] dB, P =0.72), patients with PACG had thicker global retinal nerve fiber layer (RNFL), smaller cup volume, smaller cup-to-disc ratio, and larger rim area than POAG (77 [20] vs. 71 [14] µm, 0.32 [0.28] vs. 0.40 [0.29] mm 3 , 0.6 [0.2] vs. 0.7 [0.1], 1.07 [0.40] vs. 0.89 [0.30] mm 2 , P <0.001 for all), while patients with POAG had more pronounced inferior RNFL thinning (82 [24] vs. 95 [35] µm, P <0.001). In a multivariable analysis, hyperopia [odds ratio (OR): 1.24, confidence interval (CI): 1.13-1.37], smaller cup-to-disc ratio (OR: 0.69, CI: 0.61-0.78), thicker inferior RNFL (OR: 1.15, CI: 1.06-1.26) and worse mean deviation (OR: 0.95, CI: 0.92-0.98) were associated with PACG. Functionally, POAG was associated with superior paracentral loss and PACG with inferior field loss. After adjusting for average RNFL thickness, PACG was associated with more diffuse loss than POAG (total deviation differences 1.26-3.2 dB).

CONCLUSIONS

Patients with PACG had less structural damage than patients with POAG despite similar degrees of functional loss. Regional differences in patterns of functional and structural loss between POAG and PACG may improve disease monitoring for these glaucoma subtypes.

Effect of presbyopic correction lens on humphrey visual field testing in patients with multifocal intraocular lens

Most previous studies on the effects of multifocal intraocular lenses (MIOL) on Humphrey visual field (HVF) used presbyopic corrective lens (PC). There has been insufficient data from patients with MIOL performing HVF with and without PC. This study aimed to determine the effect of PC on HVF testing in patients with MIOL. This was a prospective, comparative crossover study at the Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University between June 2015 and July 2018. Early-stage glaucomatous and non-glaucomatous pseudophakic patients with 2 models of MIOL completed HVF testing with and without PC. Mean deviation (MD), pattern standard deviation (PSD), and reliability indices (fixation losses, false positives, and false negatives) were compared. Ninety-four eyes of 59 patients were enrolled. After excluding patients with confirmed unreliable visual field, 82 eyes of 51 patients (male, 22; female, 29) with a mean age of 65.4 years were included in the study. Forty-nine eyes were non-glaucoma and 33 eyes were early-stage glaucoma. Forty-four eyes received TECNIS ZM900 and 38 eyes received Acrysof IQ ReSTOR SN6AD1. The overall MD standard deviation was -3.5 (2.1) with PC and -3.1 (2.1) without PC (P = .01). The overall PSD standard deviation was 2.8 (1.5) with PC and 2.7 (1.5) without PC (P = .93). The reliability indices were not statistically significantly different with and without PC. There was a good intraclass correlation (ICC) of MD (ICC = 0.87) and PSD (ICC = 0.88) with and without PC. Eyes with TECNIS ZM 900 had significantly better MD when performing HVF without PC (mean difference -0.7, P < .01), but not with Acrysof IQ ReSTOR SN6AD1 (mean difference -0.1, P = .74). Pseudophakic eyes with MIOL may not require PC during HVF testing regardless of the MIOL model. Although eyes with TECNIS ZM900 performed HVF without PC resulted in a significantly better MD value compared with PC, the difference was not clinically significant.

Perimetric Comparison Between the IMOvifa and Humphrey Field Analyzer

PRCIS

IMO visual function analyzer (IMOvifa), a binocular perimeter, has similar output to the Humphrey Field Analyzer (HFA), but reduced the measurement time.

PURPOSE

The purpose of this study is to evaluate the performance of IMOvifa, a perimeter that performs binocular visual field (VF) testing, and to compare its results with standard automated perimetry.

METHODS

All patients underwent HFA 24-2 SITA-Fast and IMOvifa 24-2 AIZE-Rapid on the same day. Mean deviation (MD), pattern SD (PSD), foveal threshold, and visual field index (VFI) were compared between the 2 perimeters using Wilcoxon signed-rank tests, Pearson correlation, and Bland-Altman plot. Measurement time for performing VF for both eyes was also collected for each device.

RESULTS

In this cross-sectional study, 138 eyes (including 25 healthy, 48 glaucoma suspects, and 65 primary open angle glaucoma) of 69 patients were evaluated. Measurement time was significantly faster for IMOvifa compared with HFA (256 vs. 419 s, P <0.001). No significant differences were seen in MD and VFI between HFA and IMOvifa (both P >0.05). Significant differences were seen in mean PSD 3.2 (2.7, 3.6) dB for HFA versus 4.1 (3.5, 4.6) for IMOvifa ( P <0.001), and foveal threshold 33.9 (33.1, 34.6) dB for HFA versus 30.6 (29.3, 31.9) dB for IMOvifa ( P <0.001). Pearson r was strong for MD ( r =0.90, P <0.001), PSD ( r =0.78, P <0.001), and VFI ( r =0.94, P <0.001). The mean difference (95% limits of agreement) was -0.1 (-3.8, 3.5) dB for MD, -0.4 (-3.4, 2.5) dB for PSD, and 0.1 (-8.9, 9.1) dB for VFI, respectively.

CONCLUSIONS

IMOvifa reduced measurement time by 39%. MD, PSD, and VFI values for IMOvifa showed good agreement with HFA SITA-Fast strategy. This perimeter reduced fatigue for both patient and examiner. Additional studies are needed to determine whether it will be useful for routine VF testing.

Longitudinal Signal-to-Noise Ratio of Perimetry at Different Severities of Glaucoma

Purpose

Automated perimetry is relied on for functional assessment of patients with glaucoma, but questions remain about its effective dynamic range and its utility for quantifying rates of progression at different stages of the disease. This study aims to identify the bounds within which estimates of rate are most reliable.

Methods

Pointwise longitudinal signal-to-noise ratios (LSNR), defined as the rate of change divided by the standard error of the trend line, were calculated for 542 eyes of 273 patients with glaucoma/suspects. The relations between the mean sensitivity within each series and lower percentiles of the distribution of LSNRs (representing progressing series) were analyzed by quantile regression, with 95% confidence intervals derived by bootstrapping.

Results

The 5th and 10th percentiles of LSNRs reached a minimum at sensitivities 17 to 21 dB. Below this, estimates of rate became more variable, making LSNRs of progressing series less negative. A significant step change in these percentiles also occurred at approximately 31 dB, above which LSNRs of progressing locations became less negative.

Conclusions

The lower bound of maximum utility for perimetry was ∼17 to 21dB, coinciding with previous results suggesting that below this point, retinal ganglion cell responses saturate and noise overwhelms remaining signal. The upper bound was ∼30 to 31 dB, coinciding with previous results suggesting that above this point, the size III stimulus used is larger than Ricco's area of complete spatial summation.

Translational Relevance

These results quantify the impact of these two factors on the ability to monitor progression and provide quantifiable targets for attempts to improve perimetry.

Application of Pattern Recognition Analysis to Optimize Hemifield Asymmetry Patterns for Early Detection of Glaucoma

Purpose

To assess the diagnostic utility of a new hemifield asymmetry analysis derived using pattern recognition contrast sensitivity isocontours (CSIs) within the Humphrey Field Analyzer (HFA) 24-2 visual field (VF) test grid. The performance of an optimal CSI-derived map was compared against a commercially available clustering method (Glaucoma Hemifield Test, GHT).

Methods

Five hundred VF results of 116 healthy subjects were used to determine normative distribution limits for comparisons. Pattern recognition analysis was applied to HFA 24-2 sensitivity data to determine CSI theme maps delineating clusters for hemifield comparisons. Then, 1019 VF results from 228 glaucoma patients were assessed using different clustering methods to determine the true-positive rate. We also assessed additional 354 VF results of 145 healthy subjects to determine the false-positive rate.

Results

The optimum clustering method was the CSI-derived seven-theme class map, which identified more glaucomatous VFs compared with the GHT map. The seven-class theme map also identified more cases compared with the five-, six-, and eight-class maps, suggesting no effect of number of clusters. Integrating information regarding the location of glaucomatous defects to the CSI clusters did not improve detection rate.

Conclusions

A clustering map derived using CSIs improved detection of glaucomatous VFs compared with the currently available GHT. An optimized CSI-derived map may serve as an additional means to aid earlier detection of glaucoma.

Translational Relevance

Pattern recognition–derived theme maps provide a means for guiding test point selection for asymmetry analysis in glaucoma assessment.

Ganglion Cell Complex Analysis as a Potential Indicator of Early Neuronal Loss in Idiopathic Intracranial Hypertension

Reliable visual field testing is the gold standard in identifying future vision loss in patients with Idiopathic Intracranial hypertension (IIH). However, when field performance is unreliable, GCC analysis may be useful. We evaluated IIH patients over three visits: initial visit, follow-up visit and a third visit, almost 1 year later. We evaluated mean deviation (MD), GCC and RNFL at presentation and the second visit and compared it to the mean deviation (MD) on fields at the third visit. As early as the second visit, GCC loss correlated with visual field results seen at the third visit.

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.

Clinical Correlates of Computationally Derived Visual Field Defect Archetypes in Patients from a Glaucoma Clinic

PURPOSE

To assess the clinical validity of visual field (VF) archetypal analysis, a previously developed machine learning method for decomposing any Humphrey VF (24-2) into a weighted sum of clinically recognizable VF loss patterns.

MATERIALS AND METHODS

For each of 16 previously identified VF loss patterns ("archetypes," denoted AT1 through AT16), we screened 30,995 reliable VFs to select 10-20 representative patients whose VFs had the highest decomposition coefficients for each archetype. VF global indices and patient ocular and demographic features were extracted retrospectively. Based on resemblances between VF archetypes and clinically observed VF patterns, hypotheses were generated for associations between certain VF archetypes and clinical features, such as an association between AT6 (central island, representing severe VF loss) and large cup-to-disk ratio (CDR). Distributions of the selected clinical features were compared between representative eyes of certain archetypes and all other eyes using the two-tailed t-test or Fisher exact test.

RESULTS

243 eyes from 243 patients were included, representative of AT1 through AT16. CDR was more often ≥ 0.7 among eyes representative of AT6 (central island; p = 0.002), AT10 (inferior arcuate defect; p = 0.048), AT14 (superior paracentral defect; p = 0.016), and AT16 (inferior paracentral defect; p = 0.016) than other eyes. CDR was more often < 0.7 among eyes representative of AT1 (no focal defect; p < 0.001) and AT2 (superior defect; p = 0.027), which was also associated with ptosis (p < 0.001). AT12 (temporal hemianopia) was associated with history of stroke (p = 0.022). AT11 (concentric peripheral defect) trended toward association with trial lens correction > 6D (p = 0.069).

CONCLUSIONS

Shared clinical features between computationally derived VF archetypes and clinically observed VF patterns support the clinical validity of VF archetypal analysis.

The Effect of Attentional Cueing and Spatial Uncertainty in Visual Field Testing

Purpose

To determine the effect of reducing spatial uncertainty by attentional cueing on contrast sensitivity at a range of spatial locations and with different stimulus sizes.

Methods

Six observers underwent perimetric testing with the Humphrey Visual Field Analyzer (HFA) full threshold paradigm, and the output thresholds were compared to conditions where stimulus location was verbally cued to the observer. We varied the number of points cued, the eccentric and spatial location, and stimulus size (Goldmann size I, III and V). Subsequently, four observers underwent laboratory-based psychophysical testing on a custom computer program using Method of Constant Stimuli to determine the frequency-of-seeing (FOS) curves with similar variables.

Results

We found that attentional cueing increased contrast sensitivity when measured using the HFA. We report a difference of approximately 2 dB with size I at peripheral and mid-peripheral testing locations. For size III, cueing had a greater effect for points presented in the periphery than in the mid-periphery. There was an exponential decay of the effect of cueing with increasing number of elements cued. Cueing a size V stimulus led to no change. FOS curves generated from laboratory-based psychophysical testing confirmed an increase in contrast detection sensitivity under the same conditions. We found that the FOS curve steepened when spatial uncertainty was reduced.

Conclusion

We show that attentional cueing increases contrast sensitivity when using a size I or size III test stimulus on the HFA when up to 8 points are cued but not when a size V stimulus is cued. We show that this cueing also alters the slope of the FOS curve. This suggests that at least 8 points should be used to minimise potential attentional factors that may affect measurement of contrast sensitivity in the visual field.

Current Practice with Standard Automated Perimetry

This article reviews standard visual field testing. The authors discuss the psychophysics involved in the design of the perimeter and the parameters used to test visual field sensitivity. The authors also explain normal and pathological sensitivity across the visual field, the patient and testing conditions that influence visual field results, and the interpretation of a single visual field, with an emphasis on detection of glaucomatous damage. The new thresholding program for visual fields, Swedish Interactive Thresholding Algorithm, is explained. Finally, the authors give examples of factors that should be considered when setting criteria for abnormality and review how recent studies have used various criteria to identify abnormality.

Standard automated perimetry and algorithms for monitoring glaucoma progression

Despite increasingly sophisticated techniques for the computerized analysis of the optic nerve and retinal nerve fiber layer, standard automated perimetry (SAP) is still the primary test for assessing functional damage in glaucoma. Most of the diseases affecting the visual field can be studied analyzing the central visual field with a fixed grid of points set at 6 degrees or at a variable density within central 30 degrees, using a III white target stimulus (program 30/2 or 24/2 Humphrey, G1/G2 or 30/2 Octopus). Although there is lack of a true gold standard for glaucoma, SAP results were the primary endpoint in most of the clinical trials in glaucoma. New thresholding strategies allowed a considerable reduction of examination time without substantial loss of accuracy. Moreover, recent findings on structure-function correlation in glaucoma validate the clinical role of this well-known and widespread method of examination.

What's new in perimetry

Despite important refinements that have improved quantitation and shortened test time, modern perimetry remains relatively insensitive and plagued by high test-retest variability. Some novel methods, though not yet fully vetted, offer the promise of improving sensitivity and reducing variability.

Pupillary anomaly masquerading as a glaucomatous visual field defect: a case report

Background

Patients are often referred to ophthalmologists with focal visual field defects on routine testing, possibly related to a potential diagnosis of glaucoma. However, examination of the individual patient's ocular characteristics as well as facial characteristics may often reveal a cause of the visual field defect.

Case presentation

We describe a patient who was found to have a superior visual field defect on routine testing by the optician. Repeat perimetry with pharmacological dilatation of the pupil revealed that the cause of the field defect was related to an eccentric inferiorly displaced pupil, secondary to trauma some years previously.

Discussion

Individual patient characteristics, including both ocular, as well as facial, need to be considered, when interpreting any visual field defect.

Pressure increase following primary laser trabeculoplasty. Effect on the visual field

Possible damaging effects on the visual field of postlaser pressure elevations the first 24 h following primary laser trabeculoplasty were investigated in 61 patients with exfoliative or open-angle glaucoma. The intraocular pressure was monitored the first 24 h after treatment. Treatment with pressure reducing agents was started if the intraocular pressure was > or = 50 mmHg. The visual field was plotted before and 1, 3, and 6 months after laser treatment with the C-30-2 program on a Humphrey visual field analyzer. Peak pressures > or = 50 mmHg occurred with 15 (25%) patients. There was no relationship between visual field changes at 1 month and pressure increase, peak pressure, prelaser pressure, prelaser visual field indices, the use of timolol postlaser, or the pressure decrease or pressure level 1 month after laser treatment. From 1 to 6 months after laser trabeculoplasty the visual field parameters remained stable. Postlaser pressure spikes do not seem to damage the visual field providing they are detected and treated.

Effect of uncorrected refractive errors upon central visual field testing

An investigation of the effects of uncorrected refractive errors upon a central visual field examination has been made with a view to establishing what the likely effects would be of omitting a refractive correction when screening the visual field with a threshold related, supra-threshold strategy on the Henson CFA3000. The results indicate that, while a linear relationship exists between the extent of threshold elevation and the product of residual refractive error and pupil size, the scatter in the results means that accurate predictions cannot be made in individual cases. The threshold elevation was found to be independent of eccentricity (within the central 21 degrees from fixation) and did not increase the variability of results. These last two findings indicate that uncorrected refractive errors are unlikely to affect the sensitivity of the threshold related, supra-threshold strategy to localized visual field defects.

Retinal nerve fiber layer defects and automated perimetry evaluation in ocular hypertensives

Preliminary results of a larger investigation on correlation between Retinal Nerve Fiber Layer Defects (RNFL) and Automated Perimetry (AP) are presented. A group of ocular hypertensive patients was recruited and a cross-section, randomized study was carried out. The group was composed of 54 eyes from 28 patients; 15 men and 13 women, mean age 42.76 year, mean visual acuity 0.95 (Snellen cart) and mean visual defect expressed in diopters was +0.514 (from -2.5 to +5). A total of 17 (31.48%) refractive fields were pathologic according to our criteria, one from a normal RNFL and the others from nerve fiber defects. We observed 6 no reliable RNFL photographs, 18 normal, 11 slits, 6 wedge, 11 diffuse and 2 mixed defects. Comparing RNFL and AP, 53.33% of eyes with fiber defects had abnormal perimetries. The more evolutioned the defect, the larger percentage of abnormal visual fields were observed: 36.36% in slit defects, 66.66% in wedge, 54.55% in diffuse and 100% in mixed ones. Comparing location of defects with location of cluster of decreased sensibility points in visual field, a higher correlation in inferior than superior defects was found.

Visual field global indices in patients with reversal of glaucomatous cupping after intraocular pressure reduction

The authors investigated visual field changes in 28 eyes of 28 adult patients with early-to-moderate chronic open-angle glaucoma (COAG) in whom reversal of glaucomatous disc cupping was documented by computerized image analysis (Rodenstock Optic Nerve Head Analyzer) after intraocular pressure (IOP) reduction from 29.3 (+/- 5.9) to 19.4 (+/- 4.3) mmHg over 34.8 (+/- 24.8) weeks. Humphrey Statpac global indices (mean deviation and pattern standard deviation) improved in direct proportion to the magnitude of IOP reduction even after controlling for the possible influences of learning effect, short-term fluctuation, reliability, duration of IOP reduction, age, and pupil size. The mean visual field global indices (mean deviation and pattern standard deviation) improved in patients with IOP reduction of 40% or greater, in statistically significant contrast to no improvement of mean global indices with IOP reduction less than 35%. The beneficial effect of IOP reduction is apparent in COAG patients with topographical evidence of reversal of cupping.

Time-related variation in normal automated static perimetry

The effects of phase of eye test and order of eye examined were investigated in 38 normal subjects using a customized 30-point central threshold program of the Humphrey Field Analyzer 640. This program, designed to be completed within 5 minutes, was successively repeated three times for each eye (i.e., three phases for each eye) at two visits separated by an interval of approximately 2 weeks. Both global and pointwise group mean sensitivity decreased in a time-related manner, deterioration being greater for the second eye at each visit, for both 200 ms and 100 ms stimulus durations.

Static threshold variability in the peripheral visual field in normal subjects

We assessed the variability of point-wise static threshold values and the components of fluctuation outside the central 30 degrees field in 20 normal individuals tested on the Humphrey field analyzer. We found a mean short-term fluctuation of 2.37 dB, a long-term heterogeneous fluctuation of 5.28 dB, and a long-term homogeneous fluctuation of 1.10 dB. All components of fluctuation were greatest superiorly. Point-wise variation was highest superiorly and nasally and increased with greater eccentricity from fixation in all but the temporal quadrant. Also, point-wise variation was greater between individuals than between tests in a single individual. This study suggests that outside the central 30 degrees field, changes in individual threshold measurements in the superior and nasal quadrants should be greater than those in the temporal or inferior quadrants before they can be distinguished from normal variation.