Standard Automated Perimetry Tests Research Articles

The Influence of Sampling Errors on Test–Retest Variability in Perimetry

To determine whether visual fields measured by standard automated perimetry (SAP) can be distorted by higher-spatial-frequency image components and, in particular, whether test-retest variability of SAP fields can be explained by the combination of small scale fixational drift, small stimulus size, and coarse spatial sampling of the visual fields. Standard SAP test patterns have points 6° apart. The amplitude spectra of the perimeter's 10-2 fields (model 511 Humphrey Field Analyser [HFA]; Carl Zeiss Meditec, Inc., North Ryde, NSW, Australia) were assessed to see whether their finer grained sampling revealed spatial frequencies that could cause distortions of standard fields because of undersampling. Model visual fields were then constructed whose spectra were similar to the 10-2 fields, and test-retest variability was examined for Goldmann sizes III to VI stimuli and Gaussian fixational drift with standard deviations of 0.075° to 0.3°. The 10-2 fields showed significant spatial frequency content up to 0.25 cyc/deg, three times the highest frequency that a 30-2 or 24-2 sample grid can resolve. As reported for SAP, test-retest variability increased with scotoma depth, and increasing the stimulus size from III to VI caused a reduction in test-retest variability, as did reduced fixation jitter. With fixation drift half the size of that exhibited by good fixators, many of the features of SAP test-retest variability were reproduced. Reducing test-retest variability may therefore involve using large test stimuli that are blurry in appearance and that overlap somewhat when placed on the perimetric test grid. Overlap across the meridians should perhaps be avoided.

Rarebit Perimetry for Bedside Testing: Comparison With Standard Automated Perimetry

Rarebit perimetry (RBP), a technique developed for the detection of early damage to the afferent visual system, has not been extensively tested at the bedside. This study was designed to test the feasibility of bedside testing with RBP in comparison with standard automated perimetry (SAP) performed in the clinic. We tested 29 eyes of 15 subjects admitted with neurologic or neurosurgical diseases affecting the afferent visual system. RBP was performed on a laptop computer at the bedside. SAP (Humphrey field analyzer) testing was performed later in the clinic. Results were evaluated by a masked neuro-ophthalmologist. Visual fields corresponded between RBP and SAP in 21(72%) of the 29 tested eyes. RBP detected defects in 5 subjects who had normal visual field results on SAP. All subjects preferred RBP for convenience. RBP is a convenient method of bedside visual field testing and is no less sensitive to visual field defects in this role than SAP.

Usefulness of Frequency-Doubling Technology for Perimetrically Normal Eyes of Open-Angle Glaucoma Patients with Unilateral Field Loss

To determine whether frequency-doubling technology (FDT) perimetry detects visual field loss in perimetrically normal eyes of patients with open-angle glaucoma (OAG) and whether these visual field defects subsequently are detected by standard automated perimetry (SAP), and to explore the relating factors of the progression from abnormalities based on FDT to visual field loss based on SAP. Prospective cohort study. Sixty-eight OAG patients with unilateral field loss detected by SAP (Octopus, G2 program; Interzeig, Schlieren, Switzerland). Perimetrically normal eyes of participants were examined with the FDT N-30 threshold program (Humphrey Instruments, Welch-Allyn, Skaneateles, NY). The visual field examination was followed by a series of SAP examinations administered over 3 years. The relationship between FDT and subsequent SAP results in perimetrically normal eyes was analyzed. Glaucomatous optic neuropathy (GON), visual field indices, intraocular pressure (IOP), and central corneal thickness (CCT) were compared between converters (eyes with subsequent SAP abnormality) and nonconverters within perimetrically normal eyes with abnormal FDT results. Finally, the SAP test points were matched to the abnormal FDT sectors. The relative risk (RR) of subsequent SAP abnormality corresponding to FDT abnormal sectors was calculated. Sixty perimetrically normal eyes of 60 participants had complete data and a qualifying follow-up. Baseline FDT results were abnormal in 65%. Of the eyes with abnormal FDT results, 51% developed abnormal SAP results after 4 to 27 months, whereas none of the eyes with normal FDT results developed abnormal SAP results (P<0.05). In perimetrically normal eyes with abnormal FDT results, converters had a greater cup-to-disc ratio, more eyes with GON, larger and deeper cups, and worse FDT mean deviation than nonconverters (P<0.05). The IOP and CCT did not differ between the 2 groups. The RR of subsequent SAP abnormality corresponding to abnormal FDT sectors was 5.38 (95% confidence interval, 3.61-8.04; P<0.05). In perimetrically normal eyes of OAG patients, FDT detected visual field loss in almost 2 of every 3 of these eyes and also predicted to some extent future visual field loss on SAP. Severity of glaucomatous neuropathy at baseline was related to conversion of abnormalities on FDT to visual field loss on SAP.

African Descent and Glaucoma Evaluation Study (ADAGES)

To investigate differences in visual function between the healthy eyes of people of African (AD) and European descent (ED). Visual function was assessed in 393 AD and 367 ED participants selected from the African Descent and Glaucoma Evaluation Study and the Diagnostic Innovations in Glaucoma Study. Participants had normal appearance of the optic disc and intraocular pressure of less than 22 mm Hg. Each participant had 2 reliable 24-2 standard automated perimetry tests, and most had short-wavelength automated perimetry and frequency-doubling technology tests. The generalized estimating equation was used to adjust for intereye correlations. Results were adjusted for age, vertical cup-disc ratio, disc size, central corneal thickness, and presence of high blood pressure. The AD participants were younger (mean [SD] age, 46.2 [13.2] years) than the ED participants (age, 49.5 [16.6] years) (P = .003). The AD participants had worse mean deviation and pattern standard deviation and more points triggered as abnormal on the total and pattern deviation plots compared with ED participants on all tests (P < .05). A larger percentage of AD participants had confirmed abnormal glaucoma hemifield test results on standard automated perimetry only. People of AD have significantly worse performance than people of ED on all tests of visual function. Additional research using longitudinal data is needed to determine the cause of these small but significant ancestry differences in visual function.

Structure–Function Relationship and Diagnostic Value of Macular Ganglion Cell Complex Measurement Using Fourier-Domain OCT in Glaucoma

To assess the relationship between visual function and macular ganglion cell complex (GCC) thickness measured by Fourier-domain optical coherence tomography (OCT) and to evaluate the diagnostic value of GCC thickness for detecting early, moderate, and severe glaucoma. Participants underwent reliable standard automated perimetry testing and OCT imaging with optic nerve head (ONH) mode and GCC mode within a single day. The relationship between structure and function was evaluated by comparing GCC thickness with mean deviation (MD) and visual field index (VFI), by regression analysis. The results were compared with those obtained for retinal nerve fiber layer (RNFL) thickness. The area under the receiver operating characteristic curve (AUC) was used to determine the relationship between disease severity and glaucomatous changes in RNFL and GCC parameters. One hundred three normal control subjects and 138 patients with glaucoma were included in the present study. Compared with linear models, second-order polynomial models better described the relationships between GCC thickness and MD (P<0.001), and between GCC thickness and VFI (P<0.001). A GCC pattern parameter, global loss volume (GLV), had the highest AUC for detecting early glaucoma. The AUC of mean GCC thickness for early glaucoma was higher than that of mean RNFL; however, the difference was not significant (P=0.330). A curvilinear function best described the relationship between VF sensitivity and GCC thickness. Macular GCC thickness and RNFL thickness showed similar diagnostic performance for detecting early, moderate, and severe glaucoma.

Use of a Continuous Probability Scale to Display Visual Field Damage

To derive and display the percentile score (1st-99th percentile) at each perimetric location of a standard automated perimetry test to determine whether this technique will uncover patterns of loss not visible in standard (StatPac) probability maps. We computed continuous scale probability plots of data collected from testing 305 visually healthy participants with standard automated perimetry (24-2 Swedish interactive thresholding algorithm). The age-corrected thresholds were sorted by sensitivity at each visual field location. Percentiles were derived in single increments from the 1st to the 99th. We displayed the percentiles as a color scale and then interpreted visual field plots from healthy control subjects and patients with visual system disorders. Added information was achieved for identifying patterns of visual loss by using the 5th- to 20th-percentile range in conjunction with the lower range below the 5th percentile that is typically used. The extent of contiguous regional defects appeared larger using this method. Healthy control subjects often have threshold results within the 5th- to 20th-percentile range, but these test locations usually appeared randomly spaced rather than in contiguous patterns commonly seen in patients at the border of visual field defects. Continuous scale probability plots are a potentially useful adjunct for interpretation of perimetry results.

Visual Function-Specific Perimetry to Identify Glaucomatous Visual Loss Using Three Different Definitions of Visual Field Abnormality

To compare the most recent versions of standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), and frequency-doubling technology (FDT) using three definitions of visual field (VF) abnormality: single-test abnormality, abnormality confirmed by the same test, and abnormality confirmed by a different test. Data obtained from one eye of each of 174 patients with glaucoma and 164 age-matched healthy control subjects from the Diagnostic Innovations in Glaucoma Study and African Descent and Glaucoma Evaluation Study were included, based on the appearance of the optic disc on stereophotographs. Each participant had two reliable 24-2 SAP-SITA, SWAP-SITA, and Matrix FDT tests. Receiver operating characteristic (ROC) curves were generated for the PSD of each test to equate the tests at 90% and 95% specificity. SAP, SWAP, and FDT were compared under each definition of VF abnormality by assessing the sensitivities, the agreement between tests and the overlap in deficit location at these set specificities. The tests were also compared using the machine-derived PSD. At a set specificity of 95%, single-test sensitivities of 30% (SAP), 29% (SWAP), and 28% (FDT) were observed (all P > 0.05). Sensitivities ranged from 24% to 27% (all P > 0.05) when same-test confirmation was used and from 20% to 23% (all P > 0.05) when different-test confirmation was used. SAP/SAP sensitivity was higher than all different-test combinations (all P < 0.05), and SWAP/FDT sensitivity was lower than all same-test combinations (all P < 0.05). Confirming VF abnormality is important and optimal when an abnormal SAP is confirmed by a subsequent SAP or SWAP test.

Mapping Standard Automated Perimetry to the Peripapillary Retinal Nerve Fiber Layer in Glaucoma

To establish a map relating visual field (VF) test points to corresponding areas of the retinal nerve fiber layer (RNFL) measured with optical coherence tomography (OCT) in patients with glaucomatous optic neuropathy. One hundred four consecutive subjects with open-angle glaucoma were prospectively selected. All subjects underwent standard automated perimetry (SAP) and imaging with OCT. Factor analyses of the mean thresholds for the SAP test points were performed, independently for each hemifield, to define regions of related points. Pearson correlations were then calculated between the VF regions and peripapillary RNFL thickness measured with OCT at each of the 12 clock-hour positions. A map relating the VF regions to the OCT sectors was plotted based on the strongest correlations between both techniques. Factor analysis distributed the VF points into five VF regions for each hemifield. A slightly asymmetric distribution of VF regions was obtained for the upper and lower points, with respect to the horizontal meridian. Mild to moderate correlations were observed between the VF regions and RNFL thickness. The superior VF regions and RNFL segments correlated most strongly at the 6- and 7-o'clock positions (r = 0.4-0.5). There was a moderate association between the VF regions and the RNFL thickness in patients with glaucomatous optic neuropathy, as measured by OCT. Within sectors of the RNFL, there was some overlap in the representation of the VF regions. The map obtained validates previously reported clinical findings and contributes to a better understanding of the relationship between structure and function in patients with glaucoma.

Influence of blue light spectrum filter on short-wavelength and standard automated perimetries

To evaluate the influence of a blue light spectrum filter (BLSF), similar in light spectrum transmittance to the intraocular lens Acrysof Natural, on standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP). Twenty young individuals (< 30 y.o.), without any systemic or ocular alterations (twenty eyes) underwent a random sequence of four Humphrey visual field tests: standard automated perimetry (SAP) and short-wavelength automated perimetry (SWAP) with and without a blue light spectrum filter. All patients had intraocular pressure lower than 21 mmHg, normal fundus biomicroscopy, and no crystalline lens opacity. Foveal threshold (FT), mean deviation (MD), and pattern standard deviation (PSD) indexes obtained from the visual field tests and the difference caused by eccentricity in short-wavelength automated perimetry examinations were analyzed using paired t test. Interindividual variability (standard deviation) was calculated using Pitman's test for correlated samples. Statistically significant reductions in the mean deviation (p < 0.001) and in the foveal threshold (p < 0.001) measured by short-wavelength automated perimetry with the use of the blue light spectrum filter in comparison to short-wavelength automated perimetry without the use of the blue light spectrum filter were observed, but not in standard automated perimetry exams. No other parameters showed statistically significant differences in the short-wavelength automated perimetry and standard automated perimetry tests. Interindividual standard deviation of the test points in the short-wavelength automated perimetry exams increased with eccentricity both with and without the use of the blue light spectrum filter, as sensitivity for inferior and superior hemifields (inferior hemifield minus superior hemifield), but no statistically significant difference in the variability when comparing the use or not of the blue light spectrum filter was noted. When comparing only the four most inferior points and the four most superior points, the inferior-superior difference increases in both situations - without and with the use of the blue light spectrum filter. The difference between without and with the use of the blue light spectrum filter was not statistically significant. Statistically significant reductions in mean deviation and foveal threshold in the short-wavelength automated perimetry with the use of the blue light spectrum filter were observed, but not in standard automated perimetry examinations. Additional studies are necessary to determine the influence of intraocular lenses with short-wavelength light filter after cataract extraction on short-wavelength automated perimetry.

Evaluation of the Structure-Function Relationship in Glaucoma

While glaucoma is evaluated on the basis of structural and functional test results, the spatial relationship between structure and function is not well defined. This study produces a topographical map to demonstrate how sectors of the optic nerve head (ONH) are related to locations in the visual field, using empiric cross-sectional patient data. One hundred nine subjects with healthy eyes and 166 subjects with diagnosed or suspected glaucoma (one test per patient) were evaluated using a retina tomograph and white-on-white standard automated perimetry (SAP). The tomograph ONH images were divided into 36 sectors; and the sector rim areas normalized to account for changes in the total rim area. These were then correlated with SAP thresholds. For each visual field location, a map was produced indicating the strength of correlation between the normalized sector rim areas and thresholds. The highest correlation between a sector's normalized rim area and a SAP location's sensitivity was 0.520. Twenty-seven of the 52 non-blind spot SAP locations exhibited a correlation greater than 0.2 with at least one ONH sector. Locations in the superior hemifield were usually best correlated with the polar inferior temporal sectors of the ONH; locations in the inferior hemifield were usually best correlated with the polar superior temporal sectors of the ONH. A map relating regions of the ONH to SAP test locations has been produced. This map may be useful in elucidating the structure-function relationship, particularly for cases of localized glaucomatous loss.

The effect of the menstrual cycle on optic nerve head analysis in healthy women

To determine the effect of the menstrual cycle on optic nerve head topographic analysis in normally menstruating, healthy women. The study included single eyes selected randomly from each of 52 healthy women with regular menstrual cycles. All subjects underwent a complete ocular examination. Optic nerve head topographic analyses were performed using a confocal scanning laser ophthalmoscope, the Heidelberg Retinal Tomograph II (HRT II, software version 1.6). The analyses were repeated three times during the menstrual cycle: in the follicular phase (days 7-10 of the cycle), at ovulation, and in the late luteal phase (days 1-3 before menstrual bleeding). Serum oestradiol, progesterone and luteinizing hormone levels were measured at each menstrual phase. Fourteen subjects were excluded from the study. The mean age of the subjects (n = 38) was 25.6 +/- 3.7 years (range 21-34 years). Blood oestradiol levels were significantly lower in the late luteal phase (35.8 pg/ml) (p < 0.0001). The mean disc area of the subjects was 1.94 +/- 0.33 mm(2). The neuroretinal rim area decreased significantly during the luteal phase (p < 0.001). However, the linear cup : disc ratio, cup : disc area ratio and the cup area were significantly higher during the luteal phase (p < 0.001). These observations raise the possibility that sex hormone fluctuations which occur during a normal menstrual cycle in healthy women significantly alter neuroretinal rim area and cup variables of the optic nerve head. These findings should be taken into consideration in the clinical follow-up of young women with glaucoma.

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes

Purpose To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Design Retrospective observational case series. Partcipants Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >−8 dB were included. Methods Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. Main outcome measures The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography–measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression ( R 2). Results The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results ( R 2) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions ( R 2 range, 0.34–0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region ( R 2 = 0.01). Conclusions Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.