Detecting early glaucoma by assessment of retinal nerve fiber layer thickness and visual function.

PURPOSE: To compare the abilities of scanning laser polarimetry (SLP), optical coherence tomography (OCT), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) perimetry to discriminate between healthy eyes and those with early glaucoma, classified based on standard automated perimetry (SAP) and optic disc appearance. To determine the agreement among instruments for classifying eyes as glaucomatous. METHODS: One eye of each of 94 subjects was included. Healthy eyes (n = 38) had both normal-appearing optic discs and normal SAP results. Glaucoma by SAP (n = 42) required a repeatable abnormal result (glaucoma hemifield test [GHT] or corrected pattern standard deviation [CPSD] outside normal limits). Glaucoma by disc appearance (n = 51) was based on masked stereoscopic photograph evaluation. Receiver operating characteristic (ROC) curve areas, sensitivities, and specificities were calculated for each instrument separately for each diagnosis. RESULTS: The largest area under the ROC curve was found for OCT inferior quadrant thickness (0.91 for diagnosis based on SAP, 0.89 for diagnosis based on disc appearance), followed by the FDT number of total deviation plot points of < or =5% (0.88 and 0.87, respectively), SLP linear discriminant function (0.79 and 0.81, respectively), and SWAP PSD (0.78 and 0.76, respectively). For diagnosis based on SAP, the ROC curve area was significantly larger for OCT than for SLP and SWAP. For diagnosis based on disc appearance, the ROC curve area was significantly larger for OCT than for SWAP. For both diagnostic criteria, at specificities of > or =90% and > or =70%, the most sensitive OCT parameter was more sensitive than the most sensitive SWAP and SLP parameters. For diagnosis based on SAP, the most sensitive FDT parameter was more sensitive than the most sensitive SLP parameter at specificities of > or =90% and > or =70% and was more sensitive than the most sensitive SWAP parameter at specificity of > or =70%. For diagnosis based on disc appearance at specificity of > or =90%, the most sensitive FDT parameter was more sensitive than the most sensitive SWAP and SLP parameters. At specificity > or = 90%, agreement among instruments for classifying eyes as glaucomatous was poor. CONCLUSIONS: In general, areas under the ROC curve were largest (although not always significantly so) for OCT parameters, followed by FDT, SLP, and SWAP, regardless of the definition of glaucoma used. The most sensitive OCT and FDT parameters tended to be more sensitive than the most sensitive SWAP and SLP parameters at the specificities investigated, regardless of diagnostic criteria.

Visual function-specific perimetry for indirect comparison of different ganglion cell populations in glaucoma.

PURPOSE: To compare short-wavelength automated perimetry, frequency-doubling technology perimetry, and motion-automated perimetry, each of which assesses different aspects of visual function, in eyes with glaucomatous optic neuropathy and ocular hypertension. METHODS: One hundred thirty-six eyes from 136 subjects were evaluated with all three tests as well as with standard automated perimetry. Fields were not used in the classification of study groups to prevent bias, because the major purpose of the study was to evaluate each field type relative to the others. Seventy-one of the 136 eyes had glaucomatous optic neuropathy, 37 had ocular hypertension, and 28 served as age-matched normal control eyes. Glaucomatous optic neuropathy was defined by assessment of stereophotographs. Criteria were asymmetrical cupping, the presence of rim thinning, notching, excavation, or nerve fiber layer defect. Ocular hypertensive eyes had intraocular pressure of 23 mm Hg or more on at least two occasions and normal-appearing optic disc stereophotographs. Criteria for abnormality on each visual field test were selected to approximate a specificity of 90% in the normal eyes. Thresholds for each of the four tests were compared, to determine the percentage that were abnormal within each patient group and to assess the agreement among test results for abnormality, location, and extent of visual field deficit. RESULTS: Each test identified a subset of the eyes with glaucomatous optic neuropathy as abnormal: 46% with standard perimetry, 61% with short-wavelength automated perimetry, 70% with frequency-doubling perimetry, and 52% with motion-automated perimetry. In the ocular hypertensive eyes, standard perimetry was abnormal in 5%, short wavelength in 22%, frequency doubling in 46%, and motion in 30%. Fifty-four percent (38/71) of eyes with glaucomatous optic neuropathy were normal on standard fields. However, 90% were identified by at least one of the specific visual function tests. Combining tests improved sensitivity with slight reductions in specificity. The agreement in at least one quadrant, when a defect was present with more than one test, was very high at 92% to 97%. More extensive deficits were shown by frequency-doubling perimetry followed by short-wavelength automated perimetry, then motion-automated perimetry, and last, standard perimetry. However, there were significant individual differences in which test of any given pairing was more extensively affected. Only 30% (11/37) of the ocular hypertensive eyes showed no deficits at all compared with 71% (20/28) of the control eyes (P < 0.001). CONCLUSIONS: For detection of functional loss standard visual field testing is not optimum; a combination of two or more tests may improve detection of functional loss in these eyes; in an individual, the same retinal location is damaged, regardless of visual function under test; glaucomatous optic neuropathy identified on stereophotographs may precede currently measurable function loss in some eyes; conversely, function loss with specific tests may precede detection of abnormality by stereophotograph review; and short-wavelength automated perimetry, frequency-doubling perimetry, and motion-automated perimetry continue to show promise as early indicators of function loss in glaucoma.

Current practice with standard automated perimetry.

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

The loss of visual function in glaucoma.

This article reviews innovative techniques for assessing the visual field and for examining glaucoma patients for evidence of visual field progression. The authors discuss the algorithms for assessing change in visual fields used in each of several multicenter studies sponsored by the National Eye Institute. The authors also give a brief review of 2 currently available alternatives to standard automated perimetry. Both are visual function specific tests that attempt to evaluate a subpopulation of retinal ganglion cells. Shortwavelength automated perimetry isolates the small bistratified (blue-yellow) ganglion cells, and Frequency Doubling Technology Perimetry tests functions that should be primarily handled by the magnocellular ganglion cells. These new perimetric procedures are promising as improvements over standard automated perimetry; however, there is still no agreed upon method for determination of glaucomatous visual field progression.

Spatial relationship of motion automated perimetry and optic disc topography in patients with glaucomatous optic neuropathy.

PURPOSE: To compare the spatial relationship of focal motion automated perimetry (MAP) visual field defect with focal defect in optic disc topography. METHODS: Patients (n = 12) with focal MAP visual field loss and focal change in optic disc topography were studied. The MAP visual field was divided into 12 field zones representing retinal nerve fiber layer arcuate bundles. Zones of MAP loss were related to rim area ratio (RAR), which was obtained by dividing the rim area, measured by the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany), into 36 10 degrees sectors and then dividing the area of each sector by the total rim area for each subject. Rim area ratio was compared to a normative database (n = 76) to quantify change in optic disc topography. In these same patients, the spatial relationship between standard automated perimetry (SAP) and short-wavelength perimetry (SWAP) and optic disc topography was also assessed. RESULTS: Motion automated perimetry superior visual field zones 14 through 19 were most often associated with a reduction in RAR for inferior sectors 24 through 29, and inferior visual field zones 4 through 7 were most often associated with a reduction in RAR for superior temporal sectors 11 through 16. Similar spatial relationships were found between SWAP and SAP and the RAR. CONCLUSION: Focal MAP visual field loss and focal changes in optic disc topography are spatially related. This relationship is similar to that found between SWAP and SAP with optic disc topography. Focal thinning or notching detected by RAR analysis might be independent of the specific functional test employed.

Motion automated perimetry identifies early glaucomatous field defects.

OBJECTIVE: To determine if motion automated perimetry can identify early glaucomatous visual field defects in patients with suspected glaucoma (by disc), those with ocular hypertension, and those with primary open-angle glaucoma. METHODS: Motion automated perimetry, a foveally centered motion test, and standard visual field tests were conducted on one randomly selected eye of normal patients (n = 38), patients with suspected glaucoma (by disc) (n = 28), patients with ocular hypertension (n = 18), and patients with primary open-angle glaucoma (n = 21). Subjects' performance on both motion tests were compared with their performance on standard perimetry. RESULTS: Perimetric motion thresholds significantly distinguished the groups (P< or =.001), while the foveally centered motion test was unable to separate them (P< or =.32). Of the total patients, 90.5% of those with glaucoma, 39.3% of those with suspected glaucoma, 27.8% of those with ocular hypertension, and 5.3% of the normal subjects had abnormal results on motion automated perimetry testing. Perimetric motion thresholds were significantly correlated with standard visual field thresholds (P< or =.001). CONCLUSION: Motion automated perimetry identifies visual field defects in patients who already show standard visual field loss as well as in a moderate percentage of those with suspected glaucoma and ocular hypertension, indicating that the testing of discrete locations might be necessary for increased diagnostic utility.

Short-wavelength automated perimetry and motion automated perimetry in patients with glaucoma.

OBJECTIVE: To compare short-wavelength automated perimetry (SWAP), a test favoring the detection of the target by the parvocellular pathways of vision, with motion automated perimetry (MAP), a test favoring detection by the magnocellular pathways, in the same eyes. PARTICIPANT: Thirty-three individuals in whom glaucoma was suspected (glaucoma suspects) and 17 patients with primary open-angle glaucoma were compared with 30 age-matched normal control subjects. INTERVENTIONS: Short-wavelength automated perimetry was done with the usual protocol (program 24-2). Motion coherence thresholds were measured with 14 random do targets that covered the 24-2 field area. Short-wavelength automated perimetry test locations corresponding to each of the 14 motion automated perimetry locations were averaged to compare 14 locations for each text. RESULTS: Short-wavelength automated perimetry and motion automated perimetry were correlated by visual field location (whole field r = -0.40, P < .001), especially in the superior field (r = -0.45, P < .001). Overlap for defective locations was present in 16 (94%) of the 17 eyes with glaucoma, although in the glaucoma suspect eyes each test showed the earliest deficit in a percentage of individuals with overlap in only 3 (21%) of the 14 eyes. An analysis of variance showed a significant effect of diagnosis for both tests (SWAP and MAP, P < .001); the eyes of patients with glaucoma were significantly different from those of the normal controls. The results for glaucoma suspects were significantly different on SWAP only in the superior temporal field (Tukey-Kramer test). CONCLUSIONS: Both tests successfully identified eyes with glaucoma and a percentage of the glaucoma suspect eyes; both were correlated by field location. These results suggest that damage due to glaucoma is nonselective for either the parvocellular or the magnocellular ganglion cell axons, that there may be individual differences in which type of ganglion cell shows damage first, and that when standard visual field loss is present the results of SWAP and MAP are defective.

Perimetric motion thresholds are elevated in glaucoma suspects and glaucoma patients.

The purpose of this study was to determine if a clinically feasible perimetric motion test utilizing random-dot kinematograms could identify glaucomatous visual field defects. Using a staircase procedure, an automated perimetric motion test and a larger foveally presented target were given to normal (n = 30), glaucoma suspects (n = 31) and primary open-angle glaucoma patients (n = 19). Motion thresholds at specific locations throughout the whole visual field were significantly elevated in glaucoma patients (P < or = 0.001). Perimetric motion testing identified 84.2% of the primary open-angle glaucoma patients and 25.8% of the glaucoma suspects as abnormal. A larger foveal stimulus was unable to distinguish between the different subject groups (P < or = 0.185). Perimetric motion thresholds were significantly correlated with Humphrey standard visual field thresholds in the glaucoma and glaucoma-suspect patients (P < or = 0.0002).

Motion perception thresholds in areas of glaucomatous visual field loss.

This study examined whether one can differentiate between areas of known visual field loss and areas of known relative field sparing in eyes with primary open angle glaucoma using motion coherence thresholds. Two visual field locations from patients with primary open angle glaucoma (n = 14), which differed significantly in sensitivity, were selected for presentation of a motion stimulus. In the area of visual field loss mean threshold was 17.4 +/- 4.1 dB (1.74 +/- 0.41 log units relative to the brightest stimulus). In the area of relative field sparing mean threshold was 27.0 +/- 3.6 dB (2.70 +/- 0.36 log units). Motion coherence thresholds were significantly poorer for the area of visual field loss compared to the area of relative field sparing (P < 0.0032, two-tailed paired t-test). This result suggests that a perimetric type motion test should be evaluated for early detection of glaucoma.