Glaucomatous Field Defects Research Articles

What Does Functional Testing Tell Us About Optic Nerve Damage?

Information from different regions of the visual field travels through specific bundles of retinal ganglion cell axons. This visual information is disrupted in patients with glaucoma, and the effects can be seen in measurements of the visual field and optic nerve. Typical shapes and sizes of glaucomatous field defects result from damage to these nerve fiber bundles at the level of the optic disk, and we have identified specific patterns of progression. These patterns apply to the visual function-specific field tests that are designed to indirectly assess sub-populations of retinal ganglion cells. The rationale for these tests is described. An argument for the importance of using visual function techniques to assess progression in an individual patient is given.

Projected number of Australians with glaucoma in 2000 and 2030.

Accurate Australian glaucoma prevalence has been provided by two population-based studies: the Blue Mountains Eye Study (BMES) and the Melbourne Visual Impairment Project (MVIP). Both stud es defined glaucoma as the presence of matching optic disc cupp ng with rim thinning and g aucomatous field defects demonstrated on automated perimetry Combining 'definite' and 'probable' rates, the glaucoma prevalence in persons aged 50 and over, age-standardized for the 2000 projected Australian population, was 2.70% (BMES) and 3.13% (MVIP), including rates for 'definite' glaucoma of 2.12% (BMES) and 2.50% (MVIP). The number of Australians aged 50 and over in the year 2000 with g aucoma could be estimated as from 144 000 persons (BMES) to 167 000 persons (MVIP). Assuming similar age-specific rates, the number of Austral ans aged 50 and over in the year 2030 wth glaucoma could be estimated as from 307 000 persons (BMES) to 337 000 persons (MVIP). Ocular hypertens on (OH) was defined as present in subjects without glaucoma wth intraocular pressure (IOP) of more than 21 mmHg, including treated subjects with 'normal' examination IOP The age-standardized OH prevalence was 5.15% (BMES), which projects to 275000 Australians with OH in 2000, increasing to 513000 in 2030.

The diagnostic significance of the multifocal pattern visual evoked potential in glaucoma.

The concept of objective perimetry is an exciting one because it strives to assess glaucoma damage without relying on psychophysical testing. The recent introduction of multifocal stimulus recording has enhanced our ability to examine the human visual field using electrophysiology. A multifocal pattern visual evoked potential can now be recorded, testing up to 60 sites within the central 25 degrees. The test requires only that the subject fixate on a target, while a cortically scaled dartboard pattern stimulus undergoes pseudorandom alternation within each of the test segments. In its present configuration the test requires at least 8 minutes recording time per eye. Modified bipolar electrode positions are required to ensure that adequate signals are detected from all parts of the visual field. In glaucoma patients, pattern visual evoked potential amplitudes have been shown to reflect visual field loss with reduction of signal amplitude in the affected areas. This technique represents the first major step toward objective detection of visual field defects in glaucoma.

Correlation Between Mean Visual Field Loss and Morphometric Optic Disk Variables in the Open-angle Glaucomas

To correlate morphologic changes of the optic disk with mean visual field defect in glaucoma. Color optic disk photographs of 302 patients with primary open-angle glaucoma, 53 patients with pseudoexfoliative glaucoma, and 55 patients with normal-pressure glaucoma were morphometrically evaluated. The data were correlated with mean visual field defect. The correlation between mean visual field defect and neuroretinal rim area was similar to a logarithmic function. The visual field deteriorated slightly in the early stage and markedly in the advanced stages of glaucoma. A discrepancy between normal visual field and abnormal optic disk occurred more often in young than in old patients. Neuroretinal rim shape, total rim area, and rim area in the temporal inferior and temporal superior disk sectors correlated best with mean visual field loss. Alpha and beta zones of peripapillary atrophy and diameter of retinal arterioles were less clearly correlated. Calculated rim variables that were corrected for optic disk area did not markedly improve the correlation coefficients. In eyes with normal visual fields, rim shape was the most important disk variable for detecting glaucomatous optic nerve damage. There were no patients with glaucomatous visual field loss and an unremarkable optic disk. In early glaucoma, changes are more marked in optic disk appearance than in the visual field, suggesting that at least for some patients, for early glaucoma diagnosis, optic disk appearance is more important than perimetry, whereas for follow-up examination, perimetry may be more useful than optic disk morphometry. The most useful planimetric optic disk parameters are neuroretinal rim shape and rim area.

Mapping Structural Damage of the Optic Disk to Visual Field Defect in Glaucoma

To evaluate the relation between the location of focal visual field defects and optic disk damage in eyes with glaucoma by short-wavelength automated perimetery and confocal scanning laser ophthalmoscopy. In 14 patients (14 eyes) with open-angle glaucoma, focal optic disk damage, and focal visual field loss, we obtain visual fields with short-wave-length automated perimetry. The short-wavelength automated perimetry visual field was divided into 21 zones, representing retinal nerve fiber layer arcuate bundles. Test points were compared with a normative database. The optic disk was assessed with a confocal scanning laser ophthalmoscope. Optic disk measurements were calculated in 10-degree sectors and compared with a normative database using a new measure, the rim area ratio, which adjusts for individual differences in disk size. The mean number (+/-SD) of damaged visual field zones was 3.9 (+/-1.9), and the mean number of damaged rim sectors was 5.0 (+/-2.9). Focal defects on the optic disk and on short-wavelength automated perimetry were topographically related with specific damaged visual field zones corresponding to specific damaged rim sectors. In patients with open-angle glaucoma with focal optic disk damage and focal visual field loss, defects in optic disk and short-wavelength automated perimetry are topographically related. The rim area ratio can be used to identify focal optic nerve defects.

Echographic Measurement of Optic Nerve Thickness Correlated With Neuroretinal Rim Area and Visual Field Defect in Glaucoma

To determine whether echographic measurements of the pial diameter of the optic nerve are significantly correlated with glaucomatous changes of the optic disk and retinal nerve fiber layer. In 31 patients with primary open-angle glaucoma and 16 normal control subjects, optic nerve thickness was determined by measuring the maximal pial diameter of the optic nerve using standardized A-scan echography. The optic disks were morphometrically examined using color stereo photographs, and the retinal nerve fiber layer was assessed using wide-angle red-free fundus photographs. Optic nerve thickness as measured echographically decreased significantly (P < .001) with decreasing neuroretinal rim area, diminishing visibility of the retinal nerve fiber layer, narrowing of the retinal arterioles, enlarging parapapillary atrophy, and increasing mean visual field defect. In an intraindividual bilateral comparison, side differences in the optic nerve thickness were significantly correlated with side differences in neuroretinal rim area (P < .0001), diameter of retinal arterioles (P = .003), and visual field defect (P < .0001). In the differentiation of normal and glaucomatous eyes, sensitivity and specificity were higher for echographic measurements of the optic nerve thickness than for parapapillary atrophy and diameter of retinal arterioles but worse than for determination of the neuroretinal rim area. Echographic measurements of optic nerve thickness are significantly correlated with glaucomatous changes of the optic disk and retinal nerve fiber layer. In patients with opaque media, echographic measurement of optic nerve thickness may be helpful in distinguishing among normal eyes, eyes with medium advanced glaucoma, and eyes with markedly progressed glaucoma.

Prevalence of Open-angle Glaucoma in Australia: The Blue Mountains Eye Study

The purpose of this study was to determine the prevalence of open-angle glaucoma and ocular hypertension in an Australian community whose residents are 49 years of age or older. There were 3654 persons, representing 82.4% of permanent residents from an area west of Sydney, Australia, who were examined. The population was identified by a door-to-door census of all dwellings and by closely matched findings from the national census. All participants received a detailed eye examination, including applanation tonometry, suprathreshold automated perimetry (Humphrey 76-point test), and Zeiss stereoscopic optic disc photography. Glaucoma suspects were asked to return for full threshold fields (Humphrey 30-2 test), gonioscopy, and repeat tonometry. A 5-point hemifield difference on the 76-point test was found in 616 persons (19% of people tested). Humphrey 30-2 tests were performed on 336 glaucoma suspects (9.2% of population), of whom 125 had typical glaucomatous field defects. Two hundred three persons had enlarged or asymmetric cup-disc ratios (> or = 0.7 in 1 or both eyes or a cup-disc ratio difference of > or = 0.3). Open-angle glaucoma was diagnosed when glaucomatous defects on the 30-2 test matched the optic disc changes, without regard to the intraocular pressure level. This congruence was found in 87 participants (2.4%), whereas an additional 21 persons (0.6%) had clinical signs of open-angle glaucoma but incomplete examination findings. Open-angle glaucoma was thus found in 108 persons, a prevalence of 3.0% (95% confidence interval [CI], 2.5-3.6), of whom 49% were diagnosed previously. An exponential rise in prevalence was observed with increasing age. Ocular hypertension, defined as an intraocular pressure in either eye greater than 21 mmHg, without matching disc and field changes, was present in 3.7% of this population (95% CI, 3.1-4.3), but there was no significant age-related increase in prevalence. The prevalence of glaucoma was higher in women after adjusting for age (odds ratio, 1.5; CI, 1.0-2.2). There was no sex difference in the age-adjusted prevalence of ocular hypertension. These data provide detailed age and sex-specific prevalence rates for open-angle glaucoma and ocular hypertension in an older Australian population.

The Heidelberg retina tomograph in glaucoma

Purpose: To establish the ability of the Heidelberg retina tomograph (HRT) to detect morphological change of the optic nerve head in glaucomatous optic neuropathy and to evaluate glaucomatous nerve fibre layer defects.Introduction: The HRT is a confocal laser scanning microscope designed for three‐dimensional imaging and measurement of the in vivo fundus. The light source is a diode laser operating at a wavelength of 670 mm. Thirty‐two single, two‐dimensional sectional images are recorded within 0.032 s with a repetition rate of 20 Hz, digitised in a frame of 25 × 256 pixels. Sequential viewing of the plates permits three‐dimensional resolution of the image. Use of the HRT enables comparison of change in optic nerve head morphology with change in visual function.Methods: The sample consists of 30 early primary open angle glaucoma subjects showing repeatable glaucomatous field defects on Humphrey 30‐2 analysis and 65 glaucoma suspects with normal Humphrey 30‐2 fields but with multiple risk factors for the development of glaucoma. All subjects are evaluated using white‐on‐white and blue‐on‐yellow visual fields as well as HRT analysis of the optic nerve head and retina at three‐month intervals over a 15‐month period.Discussion: We have demonstrated the need for consistent image scaling in prospective follow‐up (Hosking et al., 1995), a facility to be incorporated in the next software revision; the importance of selecting an optimum scan; and that the correction of astigmatism required for quality image acquisition results in image distortion. The application of nerve head analysis software to demonstrate localised wedge‐shaped nerve fibre bundle defects is illustrated and further modification of the software to demonstrate more subtle subclinical nerve fibre layer defects will be discussed.

3-dimensional topography of the optic papilla with laser scanning tomography: clinical correlation of cluster analysis

BACKGROUND The evaluation of optic disc topography is essential for the clinical diagnosis of primary open angle glaucoma. The purpose of this study was (1) to establish a computerized cluster formation of optic nerve head topography based on quantitative three-dimensional parameter values and (2) to describe the resulting clusters according to morphological appearance and visual fields. PATIENTS AND METHODS 337 optic nerve heads (glaucomatous optic neuropathy (n = 99), glaucoma suspects (n = 159), normals (n = 79) were analyzed using laser scanning tomography. A hierarchical cluster analysis was performed based on standardized variables (optic disc area, rim area, area-ratio, cup depth, cup steepness, height variations along the contour-line). Visual fields were tested by computerized static threshold perimetry. RESULTS A seven cluster solution met the optimizing criteria. The characteristic morphology of the clusters can be described as "normal" (N), "normal, large" (NL), "supernormal" (SN), "pseudonormal" (PN), "glaucoma-like-flat" (GF), "glaucoma-like-steep" (GS) and "macropapillary" (M). Visual fields were normal in 180 eyes. 99 eyes had glaucomatous field defects, 58 eyes revealed isolated relative scotomas < 10 db. Presence and degree of visual field defects varied within the automatically classified optic disc groups considerably. Visual field defects were found in 7.7% (SN), 8.3% (N), 18.8% (NL), 33.3% (M), 37% (PN), 64.7% (GF) and 83.3% (GS) respectively. Pseudonormal discs were characterized by a flattening of the height variations along the disc border. CONCLUSIONS (1) Optic nerve heads may be automatically classified based upon a combination of three-dimensional topographic variables. (2) Analysis of optic disc topography and computerized perimetry are supplementary tools in the evaluation of the glaucoma patient. Visual field defects may be present within any cluster. However, the likelyness of the presence of visual field defects differs considerably among the topometrically defined groups of optic nerve heads. Functional damage is to be expected in association with reduced height variations along the disc border, a small rim area and a steep cupping of the optic nerve head.

A comparison of automated static dark stimuli with the Humphrey STATPAC program in glaucomatous visual field loss.

Visual field examination is conventionally performed with bright stimuli on a dark background. Dark stimuli on a bright background, however, may provide different information as light increases and decreases are subject to parallel processing in the visual pathway. Twenty five eyes with primary open angle glaucoma and visual field loss were examined with the Humphrey visual field analyser thresholding program 30-2 and the computer assisted moving eye campimeter (CAMEC) using static dark stimuli at four different Weber contrast levels of -10 (n = 9), -22 (n = 25), -37 (n = 14), and -76% (n = 25) on a cathode ray tube with a background luminance of 10 cd/m2. The cumulative results obtained with STATPAC 'pattern deviation' empirical probability maps and the results from each contrast of the dark stimulus at identical test locations were compared at eccentricity annuli bands of 4-9, 10-20, and 21-28 degrees. Dark stimuli of lower contrast provided higher abnormal point detection rates. Furthermore, visual field defects to the low contrast dark stimuli were more extensive than those to the luminous stimuli. In conclusion, dark stimuli allowed the delineation between glaucomatous field defects and the normal regions in the central visual field.

Visual impairment of open angle glaucomas at first presentation and after a five to ten year follow-up.

Of all patients attended to in a clinic during 1986, 441 had open angle glaucoma diagnosed during 1974-1986 on the basis of either a verified visual field defect, a glaucomatous disc, or a repeated intraocular pressure value of at least 35 mm Hg. At first presentation of recent cases 1984-1986 (N = 128) 65 per cent were more than 70 years old. Capsular glaucomas were twice as common as simple glaucomas (low tension cases included). 62 per cent of capsular but only 26 per cent of simple glaucomas had an initial pressure of 35 mm Hg or more (p < 0.001). One third of both capsular and simple glaucomas had an advanced visual field defect with breakthrough to the periphery in the worse eye already at first presentation. This was more common if the initial pressure was 35 mm Hg or more (p < 0.05). Almost half remained unilateral cases, and the rate of severely impaired visual function in the better eye did not exceed 15 per cent. While generally 30-50 per cent of glaucomatous field defects had progressed in five years, the progression in early detected cases was only three per cent (p < 0.05). Visual field defects with breakthrough to the periphery already at first presentation progressed more often than circumscribed scotomas (p < 0.02).

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° 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°. 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° 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.

Prognostic significance of the pattern visual evoked potential in ocular hypertension.

This paper reports a prospective study on 49 ocular hypertensive patients to evaluate the prognostic significance of transient abnormalities in the pattern visual evoked potential (VEP) in the development of glaucoma. Seven of 24 patients with VEP abnormalities at diagnosis of ocular hypertension developed glaucomatous field defects in the follow-up period as compared with none of 25 patients with normal VEPs at diagnosis. We conclude that appropriately designed pattern VEP testing is a valuable complement to careful (preferably computerised, static) perimetry. In addition, our findings support the contention that, in glaucomatous disease of the optic nerve, rudimentary pattern processing mechanisms--that is 'Y'-type units of the magnocellular pathways--may be affected earlier than luminance processing mechanisms.

Gesichtsfeldveränderungen durch Linsentrübungen

60 eyes with advanced opacity of the lens nucleus and a corrected visual acuity of at least 0.1 have been examined by Octopus perimetery before and after a cataract extraction with posterior chamber lens implantation. 20 eyes had chronic glaucoma with glaucomatous alterations of the optic nerve head. Our purpose was to determine the effect of lens opacities on the result of automated perimetry especially in view of glaucomatous field defects. The influence of the cataract on the differential light threshold in the whole field (30 degrees) area showed a wide variance. The calculated visual field indices loss variance (LV) and corrected loss variance (CLV) did not clearly separate glaucomatous from cataractous field changes. Often an exact analysis of the numerical printout of the visual field helps in finding of localized glaucomatous field defects.

Clinically Detectable Nerve Fiber Atrophy Precedes the Onset of Glaucomatous Field Loss

Standardized perimetry and nerve fiber layer and color fundus photography were performed annually on 1344 eyes with elevated intraocular pressures. In 83 eyes, glaucomatous field defects developed that met rigid criteria on manual kinetic and suprathreshold static perimetry. Individual nerve fiber layer photographs were read by two masked observers. The more sensitive of the two identified nerve fiber layer defects in 88% of readable photographs at the time field loss first occurred; 60% (6/10) of eyes already had nerve fiber layer defects 6 years before field loss. In contrast, the nerve fiber layer was considered abnormal in only 11% (3/27) of normal eyes and 26% (84/327) of hypertensive eyes. The location of nerve fiber layer and field defects closely corresponded, but nerve fiber layer loss was generally more widespread. Examiner experience and severity of optic nerve damage influenced results. Mild focal defects were more readily recognized than more severe diffuse atrophy. Nerve fiber layer defects expanded with time, often by the development and coalescence of adjacent areas of damage.

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.

Quantitative Regional Structure of the Normal Human Lamina Cribrosa

We digitized magnified photographs of cross-sections of the laminae cribrosae of 16 normal subjects 50 or more years of age. The sample included 7 blacks and 9 age-matched whites. Connective tissue area as a proportion of the lamina cribrosa area was significantly less and pores were significantly larger in the superior and inferior than in the nasal and temporal quadrants of the lamina cribrosa. These differences were more pronounced for peripheral as compared with central regions of the lamina cribrosa. Less connective tissue support for nerve fibers in the superior and inferior quadrants of the optic nerve head could contribute to their greater susceptibility to glaucoma damage by allowing greater distortion of these regions at elevated intraocular pressures. The least connective tissue support was present in the inferoperipheral region of the lamina cribrosa, which may be related to the greater frequency of superior visual field defects in glaucoma. Blacks had larger total lamina cribrosa area, indicating a larger optic nerve head, and also a greater number of laminar pores than whites. However, the connective tissue proportion and pore size distribution in the laminae cribrosae of blacks were almost identical to those of whites. We found no evidence suggesting that the greater susceptibility of blacks to glaucoma damage is due to less connective tissue support for nerve fibers passing through their laminae cribrosae than in whites.

Short-term fluctuation of light discrimination sensitivity at the borders of glaucomatous visual field defects

Using profile program F-4 of the Octopus 201 computerized perimeter, retinal light sensitivity and threshold short-term fluctuations were studied in 15 eyes of 15 patients with glaucomatous field defects, with a resolution of 1.5 degrees. The scotomata were verified with programs 33 and 34 of the Octopus 201. Control profiles, either at identical locations in the healthy fellow eye or in areas showing no glaucomatous changes, were used to compare focal fluctuation in the vicinity of the scotoma. At the borders of the scotomata, between 20 degrees and 30 degrees eccentricity, a significant increase in short-term fluctuation of retinal sensitivity was found. This change in short-term fluctuation decreased with increasing distance from the field defect. Significantly greater short-term fluctuations were also detected in border-area measurements of scotomata located between 0 and 10 or 10 and 20 degrees of eccentricity.

Clinical measures of central vision function in glaucoma and ocular hypertension.

A generalized loss of visual sensitivity, even for foveal targets, has been reported as an early sign of glaucoma. In the present study of central vision, we used relatively simple and rapid clinical tests of color thresholds, color discrimination, and spatial contrast sensitivity to compare the vision of three age-matched groups of patients who had primary open angle glaucoma (n = 33) or ocular hypertension (n = 32) as well as normal subjects (n = 24). The largest sensitivity losses for both glaucoma and ocular hypertensive groups were disclosed by a color threshold test with blue lights designed to isolate the blue-sensitive pathways of the visual system. The loss of sensitivity for both the glaucoma group and the ocular hypertensive group is consistent with recent reports (from postmortem studies of human eyes) of extensive axon death even in the absence of glaucomatous field defects.

Pathogenesis of Optic Nerve Head Changes in Glaucoma

The perplexing subject of optic nerve head (ONH) damage and visual field defects in glaucoma is discussed very briefly. Most of the views on the subject can be broadly classified into either the vasogenic or the mechanical concept. For a proper understanding of the vasogenic concept, it is essential to have a thorough grasp of the marked complexities of the blood supply of the ONH; this is briefly summarized. The vasogenic and mechanical concepts are summarily reviewed. The various risk factors responsible for the interindividual variation in susceptibility to pressure-related ONH damage are mentioned. From the available evidence it can be concluded that the ONH damage in primary open angle glaucoma (POAG), low-tension glaucoma (LTG), and allied disorders is multi-factorial in origin, and most of the evidence strongly suggests vascular disturbance in the ONH as the principal culprit.