Early Glaucomatous Field Loss Research Articles

Commentary: Rethinking 10-2 visual fields in early diagnosis of glaucoma for a glided glaucoma practice: The right choice to pick up a feeble noise?

Commentary: Rethinking 10-2 visual fields in early diagnosis of glaucoma for a glided glaucoma practice: The right choice to pick up a feeble noise?

Comparative quantification of focal and diffuse visual field loss by the SPARK Precision threshold algorithm and SITA

PurposeThe aims of this paper were to examine focal and diffuse visual field loss in terms of threshold agreement between the widely used SITA Standard Humphrey Field Analyser (HFA) threshold algorithm with the SPARK Precision algorithm (Oculus Twinfield 2).MethodsA total of 39 treated glaucoma patients (34 primary open angle and 5 primary angle closure glaucoma) and 31 cataract patients without glaucoma were tested in succession with the Oculus Twinfield 2 (Oculus Optikgeräte GmbH, Wetzlar, Germany) using the SPARK Precision algorithm and with the HFA 3 (Carl Zeiss Meditec, Dublin, CA) using the 30–2 SITA Standard algorithm.ResultsSPARK Precision required around half the testing time of SITA Standard. There was a good correlation between the MS of the two threshold algorithms but MD and PSD were significantly less severe with SPARK Precision in both glaucoma (focal field loss) and cataract (diffuse field loss) groups (p < 0.001). There was poor agreement for all global indices (MS, MD and PSD) between the two algorithms and there was a significant proportional bias of MD in the glaucoma group and PSD in both glaucoma and cataract groups. The pointwise sensitivity analysis yielded higher threshold estimates in SPARK Precision than in SITA Standard in the nasal field. Classification of glaucoma severity using AGIS was significantly lower with SPARK Precision compared to SITA Standard (p < 0.001).ConclusionSITA renders deeper defects than SPARK. Compared to the SITA Standard threshold algorithm, SPARK Precision cannot quantify early glaucomatous field loss. This may be due to the mathematical linear interpolation of threshold sensitivity or deeper scotomas due to the plateau effect caused by the reduced dynamic range of the Twinfield 2 perimeter. Although not of clinical significance in early glaucoma, the plateau effect may hinder the long-term follow-up of patients during disease progression.

Diagnostic Performance of Visual Field Test Using Subsets of the 24-2 Test Pattern for Early Glaucomatous Field Loss

To explore the diagnostic performance of threshold visual field tests using subsets of the standard 24-2 test pattern in detecting early/moderate glaucomatous field loss. Normal (Brusini stage 0, n = 2344) and defective eyes (Brusini stage 2-3, n = 2222) from a database of visual field tests (6696 eyes/3586 patients, SITA standard 24-2 algorithm) were selected and resampled using a bootstrap method. The positive predictive values (PPVs) of each test location were calculated for the resampled datasets with a fail criteria of a single missed stimulus at a pattern deviation probability level of less than 0.01. Optimized test patterns started with the most frequent location of the maximum PPV in datasets. Eyes missing the location were removed and the PPV values of residual sample recalculated. The process was repeated until all defective eyes were detected. Receiver operating characteristic (ROC) curves were established for the PPV-optimized and five randomized patterns. Characteristics of visual field defects detected with subsets of optimized test pattern were established. With the PPV-optimized pattern, 95% of the field defects were detected with 30 locations and all with 43 locations. Areas under the ROC curve were greatest for the optimized pattern. With each increment in the number of test locations, the Mean Deviation of additionally detected eyes became more positive while Pattern Standard Deviation became less positive (P < 0.001). Good diagnostic performance can be obtained with optimized subsets of the standard 24-2 test pattern that can provide substantial savings in test times.

Change in Optic Nerve Head Topography in Progression of Early Glaucoma

Purpose: To investigate the clinical manifestation and the structural optic disc changes according to the development of reproducible visual field defects in a group of preperimetric patients converting to early glaucoma. Methods: Standard automated perimetry (Humphrey Field Analyzer) was performed every six months in 294 preperimetric patients. Each subject was classified as either converter or non-converter according to glaucomatous visual field changes, and the clinical manifestations were analyzed retrospectively. Sequential optic disc images were obtained using the TopSS scanning laser ophthalmoscope (TopSSTM) and optic disc parameters were measured to determine if any change had occurred. Results: A total of 44 eyes from 44 subjects (14.9%) in 294 patients subsequently developed early glaucomatous field loss (converters). The progression rate of visual field defect is 0.43dB/year. In respect to age, sex, refractive error, and diabetes mellitus, no significant differences were observed. Elevated IOP, hypertension, and family history of glaucoma were detected more frequently in the converter group than in the non-converter group. Among TopSS parameters, cup-to-disc ratio, effective area, volume above, maximum slope, and neuroretinal rim area showed statistically significant change. Changes of the neuroretinal rim were prominent in superior and inferior sectors. Conclusions: Among TopSS parameters, cup-to-disc ratio, effective area, volume above, and neuroretinal rim are useful in detecting the progression of glaucoma. Furthermore, neuroretinal rim changes in each sector may provide clinically relevant information in detecting and monitoring the progression of glaucoma.

Limitations of the glaucoma hemifield test in identifying early glaucomatous field loss

In early glaucoma, the Glaucoma Hemifield Test (GHT) interpreted 27% of 1676 fields as “within normal limits” despite the presence of real scotomas on numeric pattern deviation displays (P<.0001). In early glaucoma, visual field analysis based on the GHT alone is at signficant risk for misinterpretation, underdiagnosis, and under-treatment. In glaucoma suspects, the defect depth or pattern deviation displays should always be examined before any diagnostic or therapeutic decision.

Kinetic and Static Fixation Methods in Automated Threshold Perimetry

Static fixation is the standard method for stabilizing the eye during automated perimetry. Kinetic fixation is an alternative for fixation control in which the eye follows a moving target. This study was conducted to evaluate the fixation accuracy of static and kinetic fixation perimetry and to determine their ability to detect the absolute scotoma of the physiologic blind spot. The 71 patients with early glaucomatous field loss (mean age 65 years) and 45 control subjects (mean age 57 years) recruited from five clinical sites underwent threshold testing on the Dicon perimeter (kinetic fixation; Vismed, San Diego, CA) and Humphrey Field Analyzer (static fixation). The frequency of Heijl-Krakau fixation catch-trial errors was used as an indicator of fixation accuracy, and the measured sensitivity at the physiologic blind spot was used as an indicator of perimetric accuracy. In patients with glaucoma, the frequency of fixation errors was significantly greater for kinetic fixation (17.2%) than for static fixation (10.2%). In the control group, the frequency of fixation errors also was significantly greater for kinetic fixation (27.5%) than for static fixation (12.6%). The threshold at the presumed location of the blind spot (15 degrees temporal, 3 degrees inferior from fixation) was 14.8 dB using kinetic fixation versus 4.0 dB with static fixation in patients with glaucoma, and 18.5 dB using kinetic fixation versus 2.5 dB using static fixation in the control group. Relative to static fixation, kinetic fixation was associated with fixation inaccuracy and underestimation of the absolute scotoma at the physiologic blind spot.

Blue-on-yellow perimetry

Summary Laboratory based studies which employ foveal stimuli have demonstrated a selective short-wavelength sensitive (SWS) pathway deficit prior to visual field loss in glaucomatous patients. Early glaucomatous visual field loss as revealed by conventional perimetry, however, is generally accepted to occur outside the fovea. Consequently, blue-on-yellow perimetry was developed which permits the assessment of SWS function across the central visual field. This new clinical technique employs a blue stimulus to preferentially stimulate the SWS pathway and a high luminance yellow background to saturate the other receptor types. Clinical studies suggest that blue-on-yellow perimetry reveals early glaucomatous field loss before conventional perimetry which follows a pattern dictated by the anatomy of the retinal nerve fibre bundles. Blue-on-yellow perimetry is particularly prone to attenuation by the ocular media and macular pigment because of the use of a short-wavelength stimulus. Ocular media absorption (OMA) increases with increase in age (approx. a 10 dB increase in mean OMA between 20 and 70 years relative to 410 nm), exhibits a large variation between individuals of the same age (approx. 9 dB) and is exaggerated in diabetics. Both OMA and forward light scatter (LS) result in a diffuse reduction of blue-on-yellow sensitivity. Macular pigment absorption (MPA) does not vary systematically with age (P > 0.05) but exhibits a large variation between individuals (approx. 10 dB relative to 460 nm). MPA results in a symmetrical reduction of blue-on-yellow sensitivity centred on the fovea (mean foveal MPA 4 dB, P < 0.001) with 5° eccentricity. The psychophysical techniques employed to quantify OMA, forward LS and MPA are time-consuming and not suitable as routine clinical procedures. Methods of analysis which avoid the use of absolute sensitivity values need to be employed to identify abnormality in the blue-on-yellow visual field. Such an approach may rely on the identification of change in shape (i.e. pattern standard deviation) or symmetry (i.e. glaucoma hemifield test) of the visual field. Alternatively, the clustering of stimulus locations with markedly reduced sensitivity and the conformity of clusters to recognized patterns of glaucomatous nerve fibre loss should provide sensitive measures of abnormality.

Blue‐on‐yellow perimetry

SummaryLaboratory based studies which employ foveal stimuli have demonstrated a selective short‐wavelength sensitive (SWS) pathway deficit prior to visual field loss in glaucomatous patients. Early glaucomatous visual field loss as revealed by conventional perimetry, however, is generally accepted to occur outside the fovea. Consequently, blue‐on‐yellow perimetry was developed which permits the assessment of SWS function across the central visual field. This new clinical technique employs a blue stimulus to preferentially stimulate the SWS pathway and a high luminance yellow background to saturate the other receptor types. Clinical studies suggest that blue‐on‐yellow perimetry reveals early glaucomatous field loss before conventional perimetry which follows a pattern dictated by the anatomy of the retinal nerve fibre bundles.Blue‐on‐yellow perimetry is particularly prone to attenuation by the ocular media and macular pigment because of the use of a short‐wavelength stimulus. Ocular media absorption (OMA) increases with increase in age (approx. a 10 dB increase in mean OMA between 20 and 70 years relative to 410 nm), exhibits a large variation between individuals of the same age (approx. 9 dB) and is exaggerated in diabetics. Both OMA and forward light scatter (LS) result in a diffuse reduction of blue‐on‐yellow sensitivity. Macular pigment absorption (MPA) does not vary systematically with age (P &gt; 0.05) but exhibits a large variation between individuals (approx. 10 dB relative to 460 nm). MPA results in a symmetrical reduction of blue‐on‐yellow sensitivity centred on the fovea (mean foveal MPA 4 dB, P &lt; 0.001) with 5° eccentricity.The psychophysical techniques employed to quantify OMA, forward LS and MPA are time‐consuming and not suitable as routine clinical procedures. Methods of analysis which avoid the use of absolute sensitivity values need to be employed to identify abnormality in the blue‐on‐yellow visual field. Such an approach may rely on the identification of change in shape (i.e. pattern standard deviation) or symmetry (i.e. glaucoma hemifield test) of the visual field. Alternatively, the clustering of stimulus locations with markedly reduced sensitivity and the conformity of clusters to recognized patterns of glaucomatous nerve fibre loss should provide sensitive measures of abnormality.

New approach to estimating variability in visual field data using an image processing technique.

A new framework for evaluating pointwise sensitivity variation in computerised visual field data is demonstrated. A measure of local spatial variability (LSV) is generated using an image processing technique. Fifty five eyes from a sample of normal and glaucomatous subjects, examined on the Humphrey field analyser (HFA), were used to illustrate the method. Significant correlation between LSV and conventional estimates--namely, HFA pattern standard deviation and short term fluctuation, were found. LSV is not dependent on normals' reference data or repeated threshold determinations, thus potentially reducing test time. Also, the illustrated pointwise maps of LSV could provide a method for identifying areas of fluctuation commonly found in early glaucomatous field loss.

Blue versus white stimuli in ocular hypertension with the Friedmann Mark 1 Visual Field Analyser.

Fifty eyes of fifty patients with ocular hypertension had their visual fields tested on a Friedmann Mark 1 field analyser whilst wearing a Wratten 47B blue filter in a spectacle frame. All had normal visual fields to a white stimulus. Use of a scoring system with the blue field identified 11 patients (22%) with ocular hypertension as abnormal. The scores from this subgroup were indistinguishable from a group of subjects with early glaucomatous field loss, whilst the remaining scores were similar to normal subjects. These two subgroups of ocular hypertensive patients were similar in age and intraocular pressure. The use of a blue filter in front of the eye may offer a simple test to identify a subgroup of patients with ocular hypertension who are at increased risk of developing field loss.

Use of a blue filter in visual field analysis.

One hundred and twenty seven eyes of 127 patients were studied by means of a Kodak 47B Wratten blue gelatin filter in conjunction with the Friedmann Mark 1 visual field analyser. There were 49 patients in the normal group, 50 patients in the ocular hypertension group, and 28 patients in a group with early glaucoma. A simple scoring system did not show a useful difference between these three groups. However, use of a derived threshold value for each target group designated by the letters B to P (giving selective blue field scores) differentiated between normal subjects and those with early glaucomatous field loss. When used with a calculated upper limit of normal to give a specificity of 96%, this test had a sensitivity of 64%. Of the ocular hypertension group 22% gave abnormal results in comparison with normal persons. This simple adaptation to the Friedmann protocol may aid the ophthalmologist in the detection and confirmation of early glaucoma.

Detecting early glaucomatous field defects with the size I stimulus and Statpac.

The influence of stimulus size and normal database on the detection of visual field defects in automated static threshold perimetry (Humphrey Field Analyzer) was investigated in 82 eyes having a diagnosis of normal, glaucoma suspect, or early glaucoma. Using a mathematically derived 'normal' database, which assumes constantly decreasing threshold sensitivities with increasing eccentricity, the size I stimulus showed significantly greater sensitivity than the size III stimulus for detecting small, shallow scotomata in the central visual field. The use of Statpac, which contains an empirically derived, age-related normal database, increased the sensitivity significantly over that of the size III stimulus (with its mathematical model), and to a degree similar to that of the size I stimulus. The results obtained with the size I stimulus were reproducible and independent of the patient's age. This study suggests a potential role for the size I stimulus in evaluating eyes having or at risk of developing early glaucomatous field loss.

VISUAL FIELD AND RETINAL NERVE FIBRE LAYER IN EARLY GLAUCOMA AFTER OPTIC DISC HAEMORRHAGE

Computerized visual field testing with the Competer automatic perimeter including automatic profile perimetry revealed early glaucomatous field loss in 9 of 10 eyes with photographically demonstrable retinal nerve fibre layer (RNFL) defects after optic disc haemorrhages despite the fact than conventional routine perimetry had failed to do so. In 7 of these cases the Competer central pattern test was abnormal; in 2 cases field defects could be shown only when automatic high-resolution static profile perimetry was performed and directed according to the information present in wide-angle RNFL photographs. A field defect was also found in one of five eyes with no photographic RNFL changes. Visual field defects seem to occur in a higher proportion of cases with RNFL defects than was previously thought, but they can be very subtle and hard to find. There are, however, cases where in spite of the presence of an indisputable RNFL defect no visual field defects can be shown even with painstaking technique and conversely field defects may be present without RNFL defects. Automatic perimetry and RNFL photography complement each other in early detection and quantitation of glaucomatous damage.

Zur Topographie früher glaukomatöser Gesichtsfeldausfälle bei der Computerperimetrie

A total of 301 visual fields of 215 glaucoma patients exhibiting early glaucomatous field loss up to Stage II according to Aulhorn were investigated to determine the frequency distribution of absolute and relative defects at the 73 test points of Program 31 of the Octopus computer perimeter. The following results were obtained: (1) The frequency of absolute and relative defects was higher in the upper half of the visual field; (2) The frequency of both absolute and relative defects increased from 6 to 30 degrees eccentricity in the upper visual field, predominantly in the upper nasal quadrant, whereas in the temporal lower quadrant there were less absolute defects but equally frequent relative defects; (3) Defects in the nasal quadrant and above the horizontal meridian are most frequent (between 18 and 30 degrees absolute, between 12 and 30 degrees relative), while temporally of the blind spot and below the horizontal meridian they are quite rare; (4) In the upper half of the field, defects are closer to the fixation point and blind spot; the area between blind spot and macula largely free of defects. --In 71 eyes of 69 patients a similar frequency distribution was found with the Competer computer perimeter (test field 15-20 degrees eccentricity) giving good correlation with the Octopus results. --In 301 eyes of 215 patients with early glaucomatous defects the four test points in the region of the blind spot were evaluated and compared with the results of 121 eyes of 71 patients with ocular hypertension and no field changes. It appears highly probable that an increase in the size of the blind spot is associated with the incidence of field defects. --The distribution of early glaucomatous field defects in 214 eyes revealed a combination of paracentral scotomata with peripheral defects in 75.2%, exclusively peripheral scotomata in 19.6% and exclusively paracentral scotomata in 5.1%. The significance of the results with regard to the pathophysiology of glaucomatous visual field loss is discussed.

Regional Differences in the Structure of the Lamina Cribrosa and Their Relation to Glaucomatous Optic Nerve Damage

Previously, there was no feature of optic nerve head anatomy or physiology that could explain the greater susceptibility for early damage in some nerve fibers by chronic glaucoma. Using a new technique for scanning electron microscopic examination of human optic nerve heads, regional differences were found in the fine structure of the lamina cribrosa. The superior and inferior parts of the lamina at the level of the sclera appear to contain larger pores and thinner connective tissue support for the passage of nerve-fiber bundles than the nasal and temporal parts of the lamina. Since the superior and inferior laminar zones are the sites of passage for arcuate area ganglion cell axons that are most susceptible to glaucoma damage, the differences found in laminar structure in these locations may explain the characteristic pattern of early glaucomatous field loss.

Mathematical optimization of glaucoma visual field screening protocols.

There is potential for significantly shortening the time required for visual field screening protocols by a precise specification of the number, exact location, and sequence of points to be tested. Through statistical and mathematical methods, protocols have been developed for maximizing the probability of detecting at least one visual field defect in a subject who is a risk for early glaucomatous field loss. The mathematical formulation was derived in a generalized manner so that it could be applied to most kinetically or statically determined visual field screening methods.