Some aspects of the automation of perimetry

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.

A new static visual field test algorithm: the Ambient Interactive ZEST (AIZE)

Visual field (VF) test is one of the most vital tests in the diagnosis of glaucoma and to monitor the disease worsening. In the past couple of decades, the standard automated perimetry (SAP) test takes a major role in VF test for glaucoma patients. The SAP has been demanded to finish a test in short time without sacrificing accuracy. In this study, we developed and evaluated the performance of a new perimetric algorithm (ambient interactive zippy estimation by sequential testing (ZEST): AIZE) by computer simulation. AIZE is a modification of the ZEST procedure that utilizes the spatial information (weighted likelihood: WL) of neighboring test locations, which varies from the distance to the tested location, to estimate a visual threshold. Ten glaucomatous and 10 normal empirical visual field (VF) test results were simulated with five error conditions [(3% false positives (FP), 3% false negatives (FN)), (9% FP, 9% FN), (15% FP, 15% FN), (3% FP, 15% FN), (15% FP, 3% FN)]. The total number of test presentations and the root mean square error (RMSE) of the estimated visual sensitivities were compared among AIZE, the non-weighted test (WL = 0) and the fixed-weighted test (WL = 0.33). In both glaucomatous (G) and normal (N) VFs, the fixed-weighted test had the lowest number of test presentations (median G 256, N 139), followed by the AIZE (G 285, N 174) and the non-weighted test (G 303, N 195). The RMSE of the fixed-weighted test was lower (median 1.7 dB) than that of the AIZE (1.9 dB) and the non-weighted test (1.9 dB) for normal VFs, whereas the AIZE had a lower RMSE (3.2 dB) than the fixed-weighted test (4.5 dB) and the non-weighted test (4.0 dB) for glaucomatous VFs. Simulation results showed that AIZE had fewer test presentations than the non-weighted test strategy without affecting the accuracy for glaucomatous VFs. The AIZE is a useful time saving test algorithm in clinical settings.

Relationship between visual acuity and visual field and its reproducibility in patients with retinitis pigmentosa

BACKGROUND/OBJECTIVES

To investigate the association between visual acuity (VA) and visual field (VF) and its reproducibility in patients with retinitis pigmentosa (RP).

SUBJECTS/METHODS

The study cohort comprised 227 eyes of 227 patients with RP. The reproducibility of two Humphrey VF tests (10-2 Swedish Interactive Threshold Algorithm [SITA] tests) performed within a period of 3 months was calculated using the root mean squared error (RMSE) of each VF test point's sensitivity. The association between the logarithm of the minimum angle of resolution (logMAR) VA and VF sensitivity was investigated. Additionally, the relationship between RMSE and age, fixation loss, false positives, false negatives, and logMAR VA was determined.

RESULTS

The association between visual sensitivity and VA was most tight at the fovea, and it became weak toward the peripheral region in an eccentric manner. VF reproducibility appreciably increased as VA decreased. In particular, reproducibility was significantly decreased when logMAR VA was >0.5 compared with logMAR VA ≤ 0.

CONCLUSION

Reproducibility of VF tests decreases with a decrease in VA. Careful consideration is necessary when a patient's logMAR VA is >0.5.

Gaze tracker parameters have little association with visual field metrics of intrasession frontloaded SITA-Faster 24-2 visual field results

PURPOSE

To determine the usefulness of Humphrey Field Analyser (HFA) SITA-Faster 24-2 gaze tracker outputs on interpreting intra-visit visual field (VF) result pairs.

METHODS

Analysis of 1380 right-left eye pairs and 1432 pairs of test 1-test 2 intrasession VF results of patients seen within a university-based glaucoma service was undertaken to understand gaze deviation distributions. Output gaze tracker results were aggregated into total ticks, sum of amplitudes and average amplitudes. Correlations between visual field indices (mean deviation [MD], "events" and overall hill of vision) and independent variables (age and test order) were performed using one eye from each subject.

RESULTS

There was no association of test order (right-left, test 1-test 2) with eye movements. There was a significant, but weak correlation between eye movements and age (r = 0.16). Correlations of eye movements with MD were driven by more severe MD values. There were no significant correlations between intrasession difference in eye movements and the change in MD, number of "events" and hill of vision, or in the root mean square of sensitivity and total deviation values. There was also no significant correlation between gaze tracker outputs and another commonly used "reliability" metric, false positive rate.

CONCLUSIONS

Eye movement parameters as currently reported by the HFA do not appear to be correlated with key sensitivity parameters when considering the repeatability of intrasession SITA-Faster 24-2 VF results. Thus, current gaze tracker outputs do not appear to provide clinically meaningful information for interpretation of intra-visit visual field results that cannot already be garnered using other strategies.

False Positive Responses in Standard Automated Perimetry

PURPOSE

To analyze the relationship between rates of false positive (FP) responses and standard automated perimetry results.

DESIGN

Prospective multicenter cross-sectional study.

METHODS

One hundred twenty-six patients with manifest or suspect glaucoma were tested with Swedish Interactive Thresholding Algorithm (SITA) Standard, SITA Fast, and SITA Faster at each of 2 visits. We calculated intervisit differences in mean deviation (MD), visual field index (VFI), and number of statistically significant test points as a function of FP rates and also as a function of general height (GH).

RESULTS

Increasing FP values were associated with higher MD values for all 3 algorithms, but the effects were small, 0.3 dB to 0.6 dB, for an increase of 10 percentage points of FP rate, and for VFI even smaller (0.6%-1.4%). Only small parts of intervisit differences were explained by FP (r² values 0.00-0.11). The effects of FP were larger in severe glaucoma, with MD increases of 1.1 dB to 2.0 dB per 10 percentage points of FP, and r² values ranging from 0.04 to 0.33. The numbers of significantly depressed total deviation points were affected only slightly, and pattern deviation probability maps were generally unaffected. GH was much more strongly related to perimetric outcomes than FP.

CONCLUSIONS

Across 3 different standard automated perimetry thresholding algorithms, FP rates showed only weak associations with visual field test results, except in severe glaucoma. Current recommendations regarding acceptable FP ranges may require revision. GH or other analyses may be better suited than FP rates for identifying unreliable results in patients who frequently press the response button without having perceived stimuli.

Cost-Effectiveness Analysis of Minimally Invasive Trabecular Meshwork Stents with Phacoemulsification

PURPOSE

To investigate the costs and effects of implanting trabecular meshwork bypass stents during cataract surgery from a societal perspective in the United States.

DESIGN

Cost-utility analysis using Markov models and efficacy/safety data from published pivotal or randomized control trials (RCTs) of devices investigated.

PARTICIPANTS

Patients aged 65 years and older with mild to moderate primary open-angle glaucoma with or without visually significant cataract.

METHODS

With the use of Markov models, glaucoma progression through 4 glaucoma states (mild, moderate, advanced, severe/blind) and death were simulated over 35 years. The cohort with cataract entered the model and received cataract surgery with or without device implantation. We included a medication management only reference group to calculate total costs and outcomes for those without cataract. Intraocular pressure (IOP) reductions from RCTs were converted to glaucoma state transition probabilities using visual field (VF) mean deviation (MD) decline rates from the Early Manifest Glaucoma Trial. Progressive thinning of the retinal nerve fiber layer (RNFL) on OCT imaging related to IOP control warranted further intervention, including adding medication, selective laser trabeculoplasty (SLT), or incisional glaucoma surgery. We estimated whole costs at Medicare rates and obtained utility values for glaucoma states from previous studies. Incremental costs per quality-adjusted life-year (QALY) gained were evaluated at a QALY threshold of $50 000. One-way deterministic sensitivity analysis, scenario analyses, and probabilistic sensitivity analyses addressed parameter uncertainty and demonstrated model robustness.

MAIN OUTCOME MEASURES

Total costs, QALY, and incremental cost-effectiveness ratio (ICER).

RESULTS

Over 35 years in the base case, the Hydrus (Ivantis, Inc.) implanted with cataract surgery arm cost $48 026.13 and gained 12.26 QALYs. The iStent inject (Glaukos Corp.) implanted with cataract surgery arm cost $49 599.86 and gained 12.21 QALYs. Cataract surgery alone cost $54 409.25 and gained 12.04 QALYs. Initial nonsurgical management cost $57 931.22 and gained 11.74 QALY. The device arms dominated or were cost-effective compared with cataract surgery alone within 5 years and throughout sensitivity analyses. The iStent inject arm was cost-effective in 94.19% of iterations in probabilistic sensitivity analyses, whereas the Hydrus arm was cost-effective in 94.69% of iterations.

CONCLUSIONS

Implanting the Hydrus Microstent or iStent inject during cataract surgery is cost-effective at a conservative QALY threshold.

The usefulness of the Deep Learning method of variational autoencoder to reduce measurement noise in glaucomatous visual fields

The aim of the study was to investigate the usefulness of processing visual field (VF) using a variational autoencoder (VAE). The training data consisted of 82,433 VFs from 16,836 eyes. Testing dataset 1 consisted of test-retest VFs from 104 eyes with open angle glaucoma. Testing dataset 2 was series of 10 VFs from 638 eyes with open angle glaucoma. A VAE model to reconstruct VF was developed using the training dataset. VFs in the testing dataset 1 were then reconstructed using the trained VAE and the mean total deviation (mTD) was calculated (mTDVAE). In testing dataset 2, the mTD value of the tenth VF was predicted using shorter series of VFs. A similar calculation was carried out using a weighted linear regression where the weights were equal to the absolute difference between mTD and mTDVAE. In testing dataset 1, there was a significant relationship between the difference between mTD and mTDVAE from the first VF and the difference between mTD in the first and second VFs. In testing dataset 2, mean squared prediction errors with the weighted mTD trend analysis were significantly smaller than those form the unweighted mTD trend analysis.

Vision to improve: quality improvement in ophthalmology

Improving quality of care and patient outcomes is a professional duty of all health care workers. Quality improvement is a part of health policy, an accreditation requirement of residency programs, and a recognized sub-specialty in academic medicine. Given the increasing need for ophthalmological services with our aging population, it is critical for ophthalmologists and their staff to develop the necessary skills in quality improvement to ensure access to care that is safe, patient-centered, effective, efficient, equitable, and timely. This narrative review outlines tools that are used in a recognized framework, including the creation of an aim statement, Ishikawa diagram, Pareto analysis, process maps, Plan-Do-Study-Act cycles, and run charts. We also discuss common challenges that occur when conducting quality initiatives. Two quality improvement projects conducted in the Department of Ophthalmology at University of Toronto are used as examples to illustrate these tools. The aim of the first project was to improve visual field test reliability and the aim of the second was to ensure secure email communication between residents and staff in caring for emergency patients. This primer provides the foundations ophthalmologists and their staff can use to support and guide their quality improvement efforts.

Estimating the Reliability of Glaucomatous Visual Field for the Accurate Assessment of Progression Using the Gaze-Tracking and Reliability Indices

PURPOSE

To investigate the usefulness of visual field (VF) reliability indices and gaze tracking (GT) for the accurate assessment of progression in glaucoma.

DESIGN

Institutional practice.

PARTICIPANTS

Four hundred eighty-three eyes of 304 patients with open-angle glaucoma.

METHODS

In each eye, a series of 10 VFs were examined. Using the GT chart at the bottom of the VF printout (Humphrey Field Analyzer, Swedish interactive threshold algorithm standard), average tracking failure frequency (TFF), average blinking frequency (BF), and the total amount of eye movement per stimulus (MPS) were calculated. Mean total deviation (mTD) was calculated based on the 52 total deviation values in each 24-2 VF, and linear regression was applied to the series of mTD measurements over time. Progression was deemed to have occurred based on 2 separate definitions: (1) the mTD rate across all 10 VFs (VF_1-10) was significant (P < 0.05) and less than 0 dB/year and (2) the mTD rate was less than -0.5 dB/year and significant at P < 0.05. The mTD rate also was calculated in shorter VF series (VF_1-5-VF_1-9). The area under the receiver operating characteristic curve (AUC) was calculated from the relationship between mTD rates of shorter VF series (n < 10) and the diagnosis of progression in all 10 VFs. This analysis was iterated after excluding eyes with increasingly strict cutoff values for the standard VF reliability indices (fixation loss [FL], false-positive [FP] rate, and false-negative [FN] rate) and the GT parameters (TFF, BF, and MPS).

MAIN OUTCOME MEASURES

Area under the receiver operating characteristic curve values with different exclusion criteria for GT and standard reliability indices.

RESULTS

The AUC was largely unchanged according to stricter FL and FP criteria. The AUC increased with a more stringent FN criterion, but only when progression was described using the second definition (a rate of less than -0.5 dB/year). The AUC increased with stricter criteria for TFF, BF, and, to some extent, MPS.

CONCLUSIONS

Mean total deviation progression rates are more reliable when FN, TFF, BF, and MPS indices are stricter. Gaze-tracking results should be considered when assessing glaucomatous progression.

The association between structure-function relationships and cognitive impairment in elderly glaucoma patients

Accurate measurement of visual field (VF) is important in accessing glaucoma, however this may not be achieved in patients with dementia or mild cognitive impairment (CI). We investigated the association between CI and structure-function relationships in elderly glaucoma patients. The study included 94 eyes of 51 glaucoma patients aged ≥75 years with no diagnoses of dementia. CI was assessed using the Mini Mental State Examination (MMSE). Using the leave-one-out cross-validation, the mean deviation (MD) of the Humphrey 30-2 VF was predicted from measurements of optical coherence tomography, and the relationship between the squared prediction error and the MMSE score, together with age, fixation loss (FL), false positive (FP), and false negative (FN) percentages that were analyzed using the linear mixed model. A high prevalence of MCI or dementia was observed in the elderly population. The squared prediction error value of the MD was 17.0 ± 21.1 (mean ± standard deviation). The squared prediction error increased with decreasing MMSE total score, but age, FL, FP, and FN were not related. Careful consideration is needed when interpreting the VF results of these patients, because VF can be over- or underestimated, as suggested by the decreased structure-function relationships.

The association between ocular surface measurements with visual field reliability indices and gaze tracking results in preperimetric glaucoma

Background/aims

To investigate the relationship between gaze tracking (GT) results and ocular surface condition in glaucoma.

Method

The Humphrey 24–2 visual field (VF) was measured in 34 eyes of 30 patients with open-angle glaucoma without VF damage. Tear break-up time, Schirmer’s test, tear meniscus volume (TMV) and presence of superficial punctate keratopathy (SPK) were also measured in order to describe the condition of the ocular surface. Various GT parameters were calculated: the average frequency of eye movements per stimulus between 1° and 2° (move1-2), the average frequency of eye movements per stimulus between 3° and 5° (move3-5), the average frequency of eye movements per stimulus more than 6° (move≥6), the average tracking failure frequency per stimulus (TFF) and the average blinking frequency. The relationship between GT parameters, reliability indices and ocular surface measurements was investigated using linear mixed modelling.

Results

SPK was positively associated with high rates of move3-5 (coefficient=0.12 for SPK+, p=0.003) and move≥6 (coefficient=0.052 for SPK+, p=0.023). High TMV was significantly related to TFF (coefficient=0.37, p=0.023). Fixation losses, false-positives and false-negatives were not significantly associated with any GT parameters or ocular surface measurements.

Conclusion

SPK is associated with increased frequency of eye movements (move3-5 and move≥6). In addition, large TMV is associated with increased rate of TFF. Careful attention should be paid when interpreting GT parameters in patients with SPK or a large TMV.

Comparison of size modulation and conventional standard automated perimetry with the 24-2 test protocol in glaucoma patients

This prospective randomized study compared test results of size modulation standard automated perimetry (SM-SAP) performed with the Octopus 600 and conventional SAP (C-SAP) performed with the Humphrey Field Analyzer (HFA) in glaucoma patients. Eighty-eight eyes of 88 glaucoma patients underwent SM-SAP and C-SAP tests with the Octopus 600 24-2 Dynamic and HFA 24-2 SITA-Standard, respectively. Fovea threshold, mean defect, and square loss variance of SM-SAP were significantly correlated with the corresponding C-SAP indices (P < 0.001). The false-positive rate was slightly lower, and false-negative rate slightly higher, with SM-SAP than C-SAP (P = 0.002). Point-wise threshold values obtained with SM-SAP were moderately to strongly correlated with those obtained with C-SAP (P < 0.001). The correlation coefficients of the central zone were significantly lower than those of the middle to peripheral zone (P = 0.031). The size and depth of the visual field (VF) defect were smaller (P = 0.039) and greater (P = 0.043), respectively, on SM-SAP than on C-SAP. Although small differences were observed in VF sensitivity in the central zone, the defect size and depth and the reliability indices between SM-SAP and C-SAP, global indices of the two testing modalities were well correlated.

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.

Comparison of clinicians and an artificial neural network regarding accuracy and certainty in performance of visual field assessment for the diagnosis of glaucoma

PURPOSE

To compare clinicians and a trained artificial neural network (ANN) regarding accuracy and certainty of assessment of visual fields for the diagnosis of glaucoma.

METHODS

Thirty physicians with different levels of knowledge and experience in glaucoma management assessed 30-2 SITA Standard visual field printouts that included full Statpac information from 99 patients with glaucomatous optic neuropathy and 66 healthy subjects. Glaucomatous eyes with perimetric mean deviation values worsethan -10 dB were not eligible. The fields were graded on a scale of 1-10, where 1 indicated healthy with absolute certaintyand 10 signified glaucoma; 5.5 was the cut-off between healthy and glaucoma. The same fields were classified by a previously trained ANN. The ANN output was transformed into a linear scale that matched the scale used in the subjective assessments. Classification certainty was assessed using a classification error score.

RESULTS

Among the physicians, sensitivity ranged from 61% to 96% (mean 83%) and specificity from 59% to 100% (mean 90%). Our ANN achieved 93% sensitivity and 91% specificity, and it was significantly more sensitive than the physicians (p < 0.001) at a similar level of specificity. The ANN classification error score was equivalent to the top third scores of all physicians, and the ANN never indicated a high degree of certainty for any of its misclassified visual field tests.

CONCLUSION

Our results indicate that a trained ANN performs at least as well as physicians in assessments of visual fields for the diagnosis of glaucoma.

Glaucoma diagnostics

This thesis addresses several aspects of glaucoma diagnostics from both a clinical and a screening perspective. New instruments for diagnosing glaucoma have been developed over the past years, but little information is available regarding their performance as screening methods and their usefulness in ordinary clinical practice. PURPOSE OF THE RESEARCH UNDERLYING THIS THESIS:  The objectives of this research were as follows: to compare the accuracy of results of analysis of the optic nerve head (ONH) achieved by computerized imaging using the Heidelberg Retina Tomograph (HRT) and by subjective assessment performed by physicians with different degrees of experience of glaucoma (paper III); to evaluate the effect of a continuous medical education (CME) lecture on subjective assessment of the ONH for diagnosis of glaucoma (paper II); to investigate subjective assessment of perimetric test results by physicians with varying knowledge of glaucoma with a trained artificial neural network (ANN) and to compare the certainty of the classifications (paper IV); and to compare the diagnostic performance of time-domain Stratus optical coherence tomography (OCT) with that of spectral-domain Cirrus OCT (paper I), frequency doubling technology (FDT) screening perimetry and scanning laser polarimetry with the GDx variable corneal compensator (VCC) in a random population-based sample and in patients with glaucoma of varying disease severity.

METHODS AND RESULTS

  In evaluation of the ONH, use of the HRT statistical tools, Moorfields regression analysis (MRA) and the Glaucoma Probability Score (GPS) was compared with subjective assessment performed by 45 physicians. Optic nerve head images and photographs from 138 healthy and 97 glaucoma subjects were included. The sensitivity of MRA was higher (87-94%) than that of the average physician (62-82%), considerably greater than that of ophthalmologists with subspecialties other than glaucoma (53-77%) and non-significantly better than that of glaucoma experts (72-88%). Sensitivity achieved by GPS (79-93%) was also greater than that of the average physician. MRA correctly classified all eyes with advanced glaucomatous visual field defects, a result that was not achieved by GPS or even by the glaucoma experts. In eyes with small discs, MRA sensitivity (88%) was comparable with that of glaucoma experts (85%) and much better than that of GPS (50%). Also, the group comprising all physicians provided specificity (75-92%) similar to that of both MRA (69 - 86%) and GPS (72-94%) (Andersson et al. 2011a). A 1-hr CME lecture on ONH assessment led to a significant improvement in sensitivity (from 70% to 80%) and a significant decrease in uncertain assessments (from 22% to 13%), whereas specificity remained unchanged (68%) (Andersson et al. 2011b). A rise in sensitivity was seen in all subgroups of physicians, including glaucoma experts. Thirty physicians assessing standard automated perimetry (SAP) test results as Humphrey Field Analyzer single-field analysis printouts with full StatPac information from 99 patients with glaucoma and 66 healthy subjects were compared with a trained ANN regarding diagnostic performance. ANN reached significantly higher sensitivity (93%) than the average physician (83%), whereas specificity was similar for these two groups (91% and 90%, respectively). Diagnostic accuracy was similar among the different groups of physicians and seemingly rather independent of experience. Sensitivity ranged from 82% in the subgroup of other subspecialists to 87% in the glaucoma expert group, and specificity ranged from 88% among general ophthalmologists to 91% for glaucoma experts. The ANN attained certainty of classification that was in parity with that provided by the glaucoma experts and did not make any completely incorrect classifications of the visual fields (i.e. erroneous classifications were in the borderline zone) (Andersson et al. 2012). From a population-based randomly selected sample (n=308) of older subjects (aged ≥ 50 years) living in southern Sweden, 170 subjects underwent a comprehensive examination that included Stratus OCT, Cirrus OCT, an FDT screening programme and the GDx VCC. The same test protocol was applied to 138 randomized clinical patients with different stages of glaucoma. In the population-based sample, both Stratus and Cirrus OCT showed high diagnostic accuracy with area under the receiver-operating curve (aROC) values close to 1.0 (Bengtsson et al. 2012). Both OCT instruments correctly classified all of the clinical glaucoma patients with advanced disease. FDT screening showed high sensitivity (91%) but erroneously gave normal test results for some eyes with advanced disease. GDx VCC had lower sensitivity (73-92%) and also led to a large proportion of examinations with an atypical retardation pattern that is known to affect the diagnostic efficiency of this instrument.

CONCLUSIONS

  The HRT MRA performed better than most physicians and was consistent with the glaucoma experts. These results suggest that MRA can be a valuable tool for diagnosing glaucoma in ordinary practice, particularly when only a few glaucoma experts are available. Even though MRA provided 100% sensitivity in eyes with advanced glaucoma, it probably does not offer sufficient specificity to make it suitable as a screening method. Continuing medical education on ONH analysis had a small, but positive effect on diagnostic accuracy for glaucoma. An ANN trained to classify visual fields seemed to perform at least as well as most of the participating physicians, whose performances were remarkably similar regardless of their level of experience. This indicates that available tools for interpreting SAP findings are helpful in assessments of visual field test results. However, SAP is associated with learning effects (Heijl et al. 1989) that may entail low specificity for untrained subjects, and hence, it is not an ideal screening method for glaucoma. By comparison, the screening test of FDT is rapid and easy, but it is probably less suitable for screening purpose, because some eyes with advanced glaucoma were missed in this investigation. GDx VCC images for a relatively large number of eyes could not be analysed and is thus not appropriate for screening. The OCT instruments offer both high sensitivity and high specificity, and all eyes with advanced disease were correctly classified as glaucomatous in this evaluation. However, these instruments are still expensive and require special operator skills. Additional development to obtain OCT instrument that is more compact, easier to use and less expensive might render such tomography suitable as a screening tool for glaucoma.

Persistence, spatial distribution and implications for progression detection of blind parts of the visual field in glaucoma: a clinical cohort study

BACKGROUND

Visual field testing is an essential part of glaucoma care. It is hampered by variability related to the disease itself, response errors and fatigue. In glaucoma, blind parts of the visual field contribute to the diagnosis but--once established--not to progression detection; they only increase testing time. The aims of this study were to describe the persistence and spatial distribution of blind test locations in standard automated perimetry in glaucoma and to explore how the omission of presumed blind test locations would affect progression detection.

METHODOLOGY/PRINCIPAL FINDINGS

Data from 221 eyes of 221 patients from a cohort study with the Humphrey Field Analyzer with 30-2 grid were used. Patients were stratified according to baseline mean deviation (MD) in six strata of 5 dB width each. For one, two, three and four consecutive <0 dB sensitivities in the same test location in a series of baseline tests, the median probabilities to observe <0 dB again in the concerning test location in a follow-up test were 76, 86, 88 and 90%, respectively. For <10 dB, the probabilities were 88, 95, 97 and 98%, respectively. Median (interquartile range) percentages of test locations with three consecutive <0 dB sensitivities were 0(0-0), 0(0-2), 4(0-9), 17(8-27), 27(20-40) and 60(50-70)% for the six MD strata. Similar percentages were found for a subset of test locations within 10 degree eccentricity (P>0.1 for all strata). Omitting test locations with three consecutive <0 dB sensitivities at baseline did not affect the performance of the MD-based Nonparametric Progression Analysis progression detection algorithm.

CONCLUSIONS/SIGNIFICANCE

Test locations that have been shown to be reproducibly blind tend to display a reasonable blindness persistence and do no longer contribute to progression detection. There is no clinically useful universal MD cut-off value beyond which testing can be limited to 10 degree eccentricity.

Infrequent confirmation of visual field progression

OBJECTIVE

To evaluate the effects of the repeatability criteria on the detection of change in visual fields by six progression algorithms used in standard automated perimetry.

DESIGN

Retrospective, observational case series

PARTICIPANTS

Fifty-one glaucoma patients, each with multiple visual fields performed between May 1990 and December 1998, were included.

METHODS

Each patient's set of visual fields were analyzed using the glaucoma change probability, the Early Manifest Glaucoma Trial (EMGT) algorithm, a modified glaucoma change probability score, a modified EMGT score, the Advanced Glaucoma Intervention Study algorithm, and the Collaborative Initial Glaucoma Treatment Study algorithm.

MAIN OUTCOME MEASURES

The effects of repeatability on the detection of field change, the level of agreement among algorithms, as well as the number of eyes identified as changed with each algorithm, were assessed.

RESULTS

Mean follow-up was 34 months (range, 12-87 months). The average percentage of eyes with change based on three consecutive follow-up fields was 8.2% (4.0%-12.5%). However, of those showing change on the initial follow-up, this change from baseline was observed in subsequent examinations on average in 23% (18%-33%), depending on the algorithm. When change was based on just one field, four of the six algorithms noted a significantly greater number of eyes with change. The algorithms, however, did not differ significantly when confirmation of field change required two versus three consecutive follow-up visual fields.

CONCLUSIONS

Although current algorithms may help identify change, there are inconsistencies among them. We found that requiring repeatable change from baseline significantly reduces the number of changed eyes identified with each subsequent follow-up field. Identification and confirmation of change in visual fields plays an important role in helping to identify true glaucoma progression; however, the specific methods to do so have yet to be determined.

A new generation of algorithms for computerized threshold perimetry, SITA

PURPOSE

The purpose of this work was to develop a new family of test algorithms for computerized static threshold perimetry which significantly reduces test time without any reduction of data quality.

METHODS

A comprehensive visual field model constructed from available knowledge of normal and glaucomatous visual fields is continuously updated during testing. The model produces threshold estimates and also estimates of the certainty to which the threshold is known at each point. Testing is interrupted at each test location at predetermined levels of threshold certainty. New time-saving methods are employed for estimation of false answers, and test pacing is optimized. After completion of the test, all threshold estimates are re-computed, taking into account the complete body of patient responses. Computer simulations were used to optimize the different parameters of the new algorithms, to evaluate the relative importance of those parameters, and to evaluate the performance of the algorithm as a whole in comparison with a standard algorithm.

RESULTS

Simulated test results obtained with this algorithm were slightly more accurate than those of the Humphrey Full Threshold test algorithm. The number of simulated stimuli presented was reduced by an average of 29% in normal fields and 26% in glaucomatous fields. Actual clinical test time should be further reduced, since the influence of the improved timing algorithm was not included in the simulations.

CONCLUSIONS

We applied new methods which take available knowledge of visual field physiology and pathophysiology into account, and employ modern computer-intensive mathematical methods for real time estimates of threshold values and threshold error estimates. In this way it was possible to design a family of testing algorithms which significantly reduced perimetric test time without any loss of quality in results.

Automated perimetry detects visual field loss before manual Goldmann perimetry

PURPOSE

To determine if automated perimetry detects visual field defects before manual Goldmann perimetry.

METHODS

Subjects with ocular hypertension without field loss on detailed manual perimetry were followed prospectively with annual automated and manual perimetry. Subjects with field loss on manual perimetry were age-matched post hoc to subjects who did not have field loss. The automated fields 1 year before the development of field loss on manual perimetry were compared between the two groups. Subjects were recruited from ophthalmologists' offices, eye clinics, and a population-based glaucoma survey in the Baltimore area. Abnormal results detected on the Humphrey Field Analyzer were defined using the glaucoma hemifield test, mean defect, and corrected-pattern standard deviation.

RESULTS

Forty subjects who had field loss during 8 years of follow-up were compared with 145 control subjects with ocular hypertension who did not have defects. Seventy-five percent of converters had abnormal results of the glaucoma hemifield test 1 year before field loss on manual perimetry, whereas 22% of controls had abnormal results of the glaucoma hemifield test (odds ratio, 13.4). The odds ratio of field loss developing on manual perimetry within 12 months was 3.3 for those with borderline results of the glaucoma hemifield test relative to the control subjects. The odds ratio was 6.0 for corrected-pattern standard deviation (P < 0.05) and 3.9 for mean deviation (P < 0.05).

CONCLUSIONS

Those with field loss on manual perimetry were more likely to have had an abnormal automated field 1 year before conversion than those who did not convert. However, 22% of subjects in whom definitive field loss did not develop on manual perimetry during the study had abnormal automated fields at one visit and 15% had abnormal automated fields on two consecutive visits.

Influence of missed catch trials on the visual field in normal subjects

A total of 20 healthy individuals purposely missed an increasing number of individual catch trial questions (false positive or negative errors or fixation losses) when tested on the Humphrey Field Analyzer to determine the effect on the normal visual field. As determined by Statpac, the global indices and probability maps became significantly altered from those for the control fields at a prevalence of 20% for false negatives and 33% for fixation losses and false positives. However, the perimeter's recorded prevalence of missed catch trials showed a wide distribution from the percentage purposely missed. A high prevalence of missed catch trials was also indicated by a greater than normal mean defect and number of questions asked. This study suggests that although the number of missed catch trials are often recorded inaccurately, they help to identify unreliable normal visual fields, as do the mean defect and the number of questions asked.

The peripheral visual field in glaucoma: reevaluation in the age of automated perimetry

With the advent of automated static perimetry has come the common practice of measuring only the central 30 degrees of vision in the diagnosis and management of glaucoma. While most glaucomatous field defects appear first in this portion of the visual field, the question remains as to how much useful information is being missed by ignoring the peripheral field, i.e., outside the central 30 degrees. Studies with both static and kinetic automated perimetry have revealed the same peripheral glaucomatous field defects previously recognized with manual perimetry, including generalized contraction, nasal steps, temporal sector defects, and hemianopic offsets. Of these, however, only measurement of the nasal periphery may add sufficient information to that obtained with static testing in the central 30 degrees to justify the added examination time; however, there are special situations in which peripheral field testing in other or all quadrants may be useful. Further study is required to establish optimum techniques for automated measurement of the peripheral visual field and to determine the significance of the results in the management of glaucoma.

Factors that influence the prevalence of positive catch trials in glaucoma patients

We evaluated factors that influence the catch-trial response in automated perimetry by consecutively examining 408 glaucoma patients (703 eyes) with either the program 30-2 or a 76-point screen with a quantified defect on the Humphrey Field Analyzer. The prevalence of positive catch trials using both programs was: 15.9% fixation losses, 5.5% false-positives, and 17.0% false-negatives. The only significant difference between the two programs was a lower prevalence of false-negatives on the program 30-2 (P less than 0.01). False-positive responses showed a significant positive correlation to fixation losses, and the catch trial response in general was correlated significantly to defect depth, test time, age, and visual acuity (P less than 0.05). This study suggests that the prevalence of positive catch trials is not an independent variable when testing glaucoma patients with automated perimetry and is not reduced by using a screening strategy over a full-threshold exam.

Full threshold versus quantification of defects for visual field testing in glaucoma

Nineteen glaucoma patients, 17 ocular hypertensives, and 16 normal subjects underwent visual field testing on the Humphrey Field Analyzer using two programs: full threshold (thresholding of all test points with double-crossing technique) and quantification of defects (thresholding only points that deviated more than 6 dB from a presumed normal retinal contour). The purpose of the study was to compare the diagnostic value of information gained by the latter, less time-consuming test with that of the full threshold procedure. The average time requirement per eye was 13 min 11 s for full thresholding and 4 min 22 s for quantification of defects. Of the 104 sets of fields, the diagnosis was at variance in 18. The differences were most often due to shallow defects in otherwise normal fields or shallow defects surrounding deeper scotomas that had been detected by both programs. The shallow defects placed the fields in more advanced diagnostic categories and were all detected with the full threshold technique.

Computerized perimetry: possibilities for individual adaptation and feedback

Computerized perimetry is often poorly accepted by the tested subjects, presumably because of sparse feedback and lack of adaptation to individual capacity. Several remedies are suggested, including visual response feedback, active correction of erroneous responses, various fixation prompts, and continuous adaptation to current reaction time. Intuitively intelligible result displays are also desirable. A novel format representing threshold level by symbol size may meet this need.

Surgical treatment of open-angle glaucoma

The influence of intraocular pressure (IOP) on the visual field of glaucoma patients is discussed; the criterion level for postoperative IOP control was set at 20 mmHg. When the IOP exceeded this level for two consecutive months, the IOP control was judged to be a failure, and the surgical results were analysed by a life-table method. Argon laser trabeculoplasty (ALT) with 50 shots over 180 degrees of the angle was used routinely, because of fewer complications than with 360 degrees ALT. A second session sometimes improved the final success rate, which was about 57% in primary open-angle glaucoma and 94% in capsular glaucoma after a follow-up period of two years and two months. All patients (120 eyes) required drugs, but their use could be reduced in about 35%. The IOP distribution in successful cases showed a peak at 16 to 17 mmHg, and the IOP was 15 mmHg or less in 21%. In trabeculectomy, pretreatment with topical indomethacin and steroid drip infusion was advocated, and concentrated sodium hyaluronate was used during surgery. These procedures reduced the incidence of shallow anterior chamber and associated choroidal detachment. The final success rate was about 60% after five years of follow-up. The IOP distribution after more than two years peaked at 13 to 15 mmHg, and the IOP was 15 mmHg or less in 53%.

Diurnal intraocular pressure. Correlation to automated perimetry

Patients referred to a centralized glaucoma laboratory obtained intraocular pressure measurements every two hours from 5:00 am to 3:00 pm. Analysis revealed 400 eyes with visual field defects and 400 eyes without visual field defects as determined by Octopus perimetry of the central 20 degrees. The diurnal variation in intraocular pressure was 6.2 mmHg +/- 3.6 for those with visual field defects and 5.5 mmHg +/- 2.7 for those without visual field defects. There was no statistical significance in the mean diurnal variation between the two groups (P = 0.91). The highest intraocular pressure tended to occur at either 5:00 am to 7:00 am or 11:00 am to 1:00 pm in both groups. The lowest intraocular pressure tended to occur between 7:00 am to 9:00 am or 1:00 pm to 3:00 pm in both groups. No significant differences were noted in the distribution between the two groups with regard to the time of the highest or lowest intraocular pressure. In the group with visual field defects, 30% had an intraocular pressure of less than 23 mmHg and 23% had an intraocular pressure of greater than or equal to 23 mmHg at all five time periods.

Variation in visual field measurements with an automated perimeter

Using the Octopus automated perimeter, we conducted visual measurements on four separate occasions during a four-week period in six subjects with normal eyes. In 11 of 12 eyes, we found at least one point at which the threshold for light detection determined for that point showed a variance of more than 4 dB between tests. Thus, automated visual fields must be interpreted cautiously because an apparent pathologic change may only represent normal variation.

Comparative material on automated and semiautomated perimeters-1983

In reviewing all the responses from the private practitioners and clinicians in Departments of Ophthalmology throughout the United States and Canada, it would appear that the majority of individuals are quite happy with the automated perimeters they have purchased. Clinicians should be aware that this is a rapidly changing field and several devices which were previously available are no longer being manufactured. In addition, because of the competition which has recently developed in the automated perimetry industry, prices are continuing to come down. Some practitioners have been unhappy with the fact they paid a higher price for a device which is currently selling at a lower price. However, a similar phenomenon has happened in the computer world and is to be expected as competition increases. The major problems which seem to be of concern to all ophthalmologists, are the difficulty in interpreting data and the management of the data. We believe one of the major frustrations of all practitioners using automated perimeters relates to the fact that this is a totally new technique, which requires time and practice to gain familiarity. In general, it would appear that most of the practitioners have been happy with the service provided by various companies, although there are a few exceptions. Read the enclosed responses and develop your own conclusions. We hope you find the information useful.

Concepts for automatic perimetry, as applied to the Scoperimeter, an experimental automatic perimeter

The development of an experimental automatic perimeter, the Scoperimeter, is described. We use an oscilloscope as campimeter screen for the examination of the central 25 degrees of the visual field. The oscilloscope beam generates a homogeneous background luminance (0.1 cd/m2) and single stimulus static stimuli in any given position. The effective luminance-range of the stimuli is 3.0-3.5 log.unit. The visual field examination is controlled by a small computer system. Four examination programs written in Basic, are described. The screening programs using threshold related suprathreshold stimuli appear to be the most efficient compromise between speed and accuracy of the examination. The printout of these programs consists of a noninterpolated grey-scale presentation. Other programs perform static meridional perimetry or measure luminance threshold in 60 regularly distributed positions in the visual field. We have taken into consideration the factors that may influence the outcome of the examination: the presence of an instruction phase, the possibility to follow the progress of the examination and careful stimulus-timing. In a second paper we present clinical results we obtained using our instrument.

Computer analysis of visual field loss and optimization of automated perimetric test strategies

Preliminary investigations of optimal target distribution patterns of automated perimetry were conducted. In the first study, frequency distributions of visual field defects were determined in glaucoma (260 scotomata) and optic nerve disease (110 scotomata) for approximately 30,000 visual field locations. The frequency distributions in glaucoma and optic nerve disease were different, and suggest guidelines for development of target distribution patterns to achieve optimal detection rates. The second study included computer simulation of 20 target distribution patterns currently used in manual and automated perimetry. Each distribution pattern was processed through the 370 glaucoma and optic nerve disease scotomata to assess detection performance. Both the density and distribution of target locations affected overall detection rates. In addition, some target configurations were more susceptible to false alarms than others. These data provide qualitative information for optimization of target distribution patterns in automated perimetry, and serve as a foundation for future quantitative studies.

Comparative evaluation of the Autofield-I, CFA-120, and Fieldmaster Model 101-PR automated perimeters

Clinical evaluations of the Autofield-I, CFA-120, and Fieldmaster Model 101-PR automated perimeters were performed in comparison with manual kinetic testing on the Goldmann perimeter. All the automated perimeters displayed similar high rates of detecting visual field defects, although their false-alarm (false-positive) rates were considerably different. The principal factors responsible for high-detection and low false-alarm rates are discussed.

Automatic (Octopus) and manual (Goldmann) perimetry in glaucoma

Of 115 patients with chronic open angle glaucoma or suspected glaucoma 115 eyes were subjected to a visual field examination with the manual Goldmann perimeter and the automatic Octopus perimeter. In 84.4 +/- 8.9% the automaton detected more visual field loss, including 27.8 +/- 10.9% of the eyes where no visual field loss was found by the manual perimetry. Since some eyes with normal fields on manual perimetry and abnormal fields detected by automatic perimetry remained abnormal on retesting, it is assumed that scotomas found by automatic perimetry and not shown by manual perimetry constitute false-negative manual fields rather than false-positive automatic fields.

Clinical experiences with the use of an automated perimeter (Octopus) in the diagnosis and management of patients with glaucoma and neurologic diseases

This is a study of 59 patients, 42 with glaucoma and 17 with neurological disease, to compare the Octopus automated perimeter with the conventional Goldmann and Tubinger perimeters for detection and assessment of visual field defects. We believe the Octopus automated perimeter is an excellent method for screening patients suspected of glaucoma and can be expected to identify over 90% of the patients actually having visual field loss due to glaucoma. In patients with neurological disease, the Goldmann perimeter was superior to either the Octopus or Tubinger perimeters in providing clinically useful information.