Can the specificity of the FDT for glaucoma be improved by confirming abnormal results?

PURPOSE: To determine whether the specificity of the frequency-doubling technology (FDT) perimeter in the screening mode for glaucoma can be improved by repeating abnormal screening results. METHODS: The FDT perimeter was used in C-20-5 screening mode, and the right eye was tested first. After both eyes were tested, the screening was repeated in eyes with any abnormal visual field defects on FDT perimetry. The printouts were categorized as possible visual field abnormality (zero or one miss), probable visual field abnormality (two to four misses), and definite visual field abnormality (more than five misses). A clinical ophthalmologic examination was conducted on the day of the FDT perimetry screening. RESULTS: Complete data were available for 223 people. The participants ranged in age from 23 to 91 years (mean, 68.5 years; standard deviation. 13.7 years), and 119 (53%) were women. The sensitivity of the FDT perimetry screening was 100%; both cases of glaucoma showed an abnormality on FDT perimetry both times. The specificity improved moderately from the first screening to the second screening. The specificity the first time was 62% (95% confidence interval, 53.1-71.2). The specificity the second time was 68.5% (95% confidence interval, 59.8-77.1). Improvement on FDT perimetry rescreening varied by the language spoken at home. Seven of the 19 non-English speakers without glaucoma improved on rescreening, compared with none of the 23 English speakers (P = 0.002). Seven of the 25 right eyes with FDT perimetry abnormalities both times and no glaucoma had no other detectable diseases. Three of 24 left eyes with FDT perimetry abnormalities both times and no glaucoma had no other detectable diseases. Of the 85 patients who did not have glaucoma but had FDT perimetry abnormalities both times, only one did not have some other detectable disease. DISCUSSION: In summary, the sensitivity for glaucoma of the C-20-5 screening mode is excellent, but a paradigm for screening with the FDT perimeter to improve the overall specificity for glaucoma still must be developed.     

Testing for glaucoma with frequency-doubling perimetry in normals, ocular hypertensives, and glaucoma patients

BACKGROUND: The aim of this study was to evaluate the diagnostic usefulness of the FDT perimeter protocol (C-20-5) in combination with a database system for analysis of single test locations. METHODS: One hundred seventy-three ocular hypertensive eyes, 116 "preperimetric" open-angle glaucoma eyes (glaucomatous optic disc atrophy, elevated intraocular pressure, no visual field defects in standard white-on-white perimetry), 199 "perimetric" open-angle glaucoma eyes (glaucomatous optic disc atrophy and visual field defects), and 151 control eyes underwent FDT screening and conventional white-on-white perimetry. Four repeated measurements were carried out in 15 glaucoma patients at 2-h intervals to judge reproducibility of all test locations. The present screening strategy begins testing at the normal 5% probability level. If a stimulus is not detected, further targets are presented. FDT-Viewfinder and statistics software were used for case-wise recalculation of all missed localized probability levels and correlation with corresponding test locations using conventional perimetry. RESULTS: Analysis of repeated measurements in patients reveals that variation of single test points can be considerable. However, the numbers of missed test-stimuli calculated globally or in quadrants are significantly correlated with corresponding Octopus visual field defects (Spearman rank correlation P<0.001). Using a predefined specificity of 96% in control eyes, 11% of ocular hypertensive eyes, 28.5% of "preperimetric" glaucoma eyes and 86.9% of "perimetric" glaucoma eyes have been classified glaucomatous using an overall score and with consideration of different cut-off points in right and left eyes. CONCLUSION: Point-wise analysis of FDT screening results can be helpful for classification of patient groups and consideration of the individual learning curve in repeated measurements. The C-20-5 protocol of the FDT perimeter is able to detect a considerable proportion of glaucomatous patients.     

Frequency doubling technology perimetry abnormalities as predictors of glaucomatous visual field loss

PURPOSE: To determine whether frequency doubling technology (FDT) perimetry results predict glaucomatous visual field defects, as assessed by standard automated perimetry (SAP), in a glaucoma suspect population. DESIGN: Longitudinal observational study. METHODS: The study included 105 eyes of 105 glaucoma suspect patients, with a mean follow-up time of 41 +/- 17 months. Glaucoma suspects had either intraocular pressure (IOP) higher than or equal to 23 mm Hg or glaucomatous optic neuropathy by stereophotograph assessment. All patients had normal SAP visual fields at baseline. A baseline FDT test was performed within 3 months of the normal SAP examination. Several baseline FDT parameters and other variables (age, gender, IOP, central corneal thickness, SAP visual field indices, and stereophotograph assessment) were investigated by univariate and multivariate Cox proportional hazards models to obtain hazard ratios (HR) and identify factors that predicted which patients had SAP glaucomatous visual field loss during follow-up. RESULTS: Seventeen patients (16%) developed repeatable SAP visual field abnormality during follow-up. An abnormal FDT examination at baseline predicted the development of SAP visual field conversion in both univariate (HR = 3.17; 95% confidence interval [CI] = 1.22-8.25; P =.018) and multivariate models (Adjusted HR = 3.68; 95% CI = 1.06-12.8; P =.04). The analysis of FDT examinations during follow-up revealed that in 59% of converters the FDT abnormalities preceded SAP visual field loss by as much as 4 years. Also, the initial development of glaucomatous visual field loss as measured by SAP occurred in regions that had previously demonstrated abnormalities on FDT testing. CONCLUSION: Functional abnormalities detected by FDT perimetry were predictive of the future onset and location of SAP visual field loss among glaucoma suspect patients.     

The distribution of visual field defects per quadrant in standard automated perimetry as compared to frequency doubling technology perimetry

To test the ability of frequency doubling technology (FDT) perimetry to reveal defects in the same field quadrants as detected by standard automated perimetry (SAP). Ninety-two eyes with open-angle glaucoma and documented visual field defects by threshold SAP (Octopus Dynamic strategy) also underwent threshold FDT testing after successfully passing the FDT screening test. All eyes revealed varying stages of SAP defects while only 80 revealed FDT damage: 31:21 eyes in the early field loss stage, 36:35 in the moderate field loss stage, and 25:24 in the severe field loss stage in SAP versus FDT, respectively. SAP was able to detect abnormalities in 74 and 79% of the superotemporal, and inferotemporal quadrants, respectively, while the corresponding FDT figures were 70 and 69% for the same quadrants (P < 0.05 each). With regards to the nasal hemifield, SAP detected defects in 73 and 81% of the superonasal and inferonasal quadrants, respectively, compared to 69 and 66% for FDT (P < 0.001 each). The test duration per individual eye was significantly shorter with FDT than with SAP (P < 0.05). As well as the already established lower sensitivity of FDT compared to SAP, this study also demonstrated the significantly poorer ability of FDT in detecting the same field quadrant defects, especially in the early stages of glaucomatous damage.     

Relationship of SITA and full-threshold standard perimetry to frequency-doubling technology perimetry in glaucoma

PURPOSE: To compare full-threshold (FT) and SITA algorithms for standard automated perimetry (SAP) with frequency-doubling technology perimetry (FDT) in glaucoma, to help clinicians to relate results in patients who have had two or more of these tests during follow-up. METHODS: This study was a retrospective analysis of data from a longitudinal prospective study at the University of California, San Diego. One hundred four eyes of 104 patients with glaucomatous optic neuropathy detected by optic disc stereophotographs were included. All patients had standard perimetry (SITA and FT) and FDT within 3 months of each other. Global indices, abnormality and severity using two threshold algorithms of standard perimetry were compared with FDT. RESULTS: More eyes had normal visual fields by SAP-FT (57 eyes) than by either SAP-SITA (42 eyes) or FDT (45 eyes), although SAP-FT agreed more closely with FDT (kappa = 0.54 +/- 0.08) on the presence of a visual field defect than did SAP-SITA (kappa = 0.34 +/- 0.08). Correlations of FDT to standard perimetry global indices were similar regardless of the threshold strategy used for standard perimetry, yielding r2= 0.38-0.57 for SAP-FT with FDT, 0.36-0.54 for SAP-SITA with FDT. CONCLUSIONS: Despite many similarities of SAP-SITA and SAP-FT, switching the standard of comparison from SAP-FT to SAP-SITA changes the relationship to FDT with regard to visual field abnormality, but not correlations of global indices. FDT detected abnormal fields in more eyes than SAP-FT. SAP-FT tended to detect a subset of eyes found abnormal by FDT. Visual field defects may be detected more often by FDT and SAP-SITA in eyes with early visual field loss, but these two tests may not agree on which eyes show field loss in patients who undergo both tests at follow-up.     

Combined use of frequency doubling perimetry and polarimetric measurements of retinal nerve fiber layer in glaucoma detection

PURPOSE: The aim of this study was to evaluate the diagnostic usefulness of the combined use of frequency-doubling technology (FDT) perimetry and polarimetry of the retinal nerve fiber layer. DESIGN: Cross-sectional study. METHODS: Seventy ocular hypertensive patients (normal optic disk and standard perimetry, elevated intraocular pressure [>21 mm Hg]), 59 patients with "preperimetric" open-angle glaucoma (glaucomatous optic disk atrophy, elevated intraocular pressure [>21 mm Hg], no visual field defect in standard perimetry), 105 patients with "perimetric" open-angle glaucoma (glaucomatous optic disk atrophy and clearly marked visual field defect), and 73 control subjects had FDT screening (protocol: C-20-5) and polarimetric measurements (GDx). Criteria for exclusion: optic disks larger than 4 mm(2), media opacities, patients younger than 33 years or older than 66 years. None of the subjects had earlier FDT perimetry. One eye of each patient and control subject entered the statistical evaluation. Database and statistical software were used for case-wise recalculation of all missed localized probability levels to create a FDT screening score. RESULTS: At a predefined specificity of 94.5% in control eyes, discrimination between "perimetric" glaucoma and normal subjects is superior using the FDT perimetry (sensitivity = 84.8%) in comparison to polarimetry (sensitivity = 63.8%), whereas sensitivity is similar with both methods in "preperimetric" patients (GDx, FDT: 25.4%). In several cases, patients classified as glaucomatous by the GDx are not the same patients as identified by the FDT perimetry. Therefore, a two-dimensional discrimination analysis can increase correct positive classification. Using a linear combination of the present FDT screening score and polarimetry ("the number"), 92.4% of "perimetric" glaucoma eyes and 44.1% of "preperimetric" glaucoma eyes have been classified as glaucomatous. CONCLUSION: Joint usage of polarimetry and FDT perimetry indicate that a combination of different techniques which can uncover different glaucoma properties, might be helpful in early glaucoma detection.     

Glaucoma detection with frequency doubling perimetry and short-wavelength perimetry

PURPOSE: The aim of this analysis was to evaluate the diagnostic usefulness of frequency doubling technology (FDT) perimetry and short-wavelength perimetry (SWAP). Moreover, to study a combination of both methods using the machine-learning technique double-bagging, which was recently established in glaucoma research. METHODS: Forty-three patients with "preperimetric" open-angle glaucoma (glaucomatous optic disc atrophy and no visual field defect in standard perimetry), 26 patients with "perimetric" open angle glaucoma (glaucomatous optic disc atrophy and visual field defect in standard perimetry), and 40 control subjects had FDT screening (protocol: C-20-5) and SWAP (Octopus 101, G2). Criteria for exclusion were color vision abnormalities, media opacities, and an age below 31 years or above 63 years. Data of 1 eye of each patient and control subject entered the statistical evaluation. A point wise evaluation of the diagnostic power of SWAP values was performed to derive spatial patterns of visual field loss. A double-bagging machine-learning algorithm was used to train classification rules on the basis of a combination of FDT scores and nerve fiber related visual field losses in SWAP. The diagnostic power of the classifiers was compared regarding their misclassification error rates and area under the receiver-operating characteristic curve. RESULTS: The combination of FDT perimetry and SWAP yielded better diagnostic results compared with FDT or SWAP separately. The overall estimated misclassification error rate of the combined classifier was 24% compared with 28% for both SWAP and FDT perimetry. Regarding the estimated performance of classifier at high specificities (>80%) in control eyes as measured by the partial area under the receiver-operating characteristic curve, the combination of both instruments is also superior to the individual instruments. CONCLUSIONS: A combination of SWAP and FDT perimetry, each targeting different neuronal pathways, may improve early glaucoma detection.     

Performance of glaucoma mass screening with only a visual field test using frequency-doubling technology perimetry

PURPOSE: To report the performance of glaucoma mass screening with only a visual field test utilizing frequency- doubling technology (FDT) perimetry in general populations.DESIGN: Hospital and population-based cross-sectional study.METHODS: This study took place in a multicenter setting. One hundred three consecutive glaucomatous patients and 14,814 persons were randomly selected. We had created a glaucoma screening protocol (GSP) using FDT perimetry (FDT-GSP). Frequency-doubling technology-glaucoma screening protocol was tested on consecutive glaucoma patients diagnosed with Humphrey visual field analyzer (30-2 SITA standard), and then FDT-GSP was applied to general populations. Frequency-doubling technology-glaucoma screening protocol positive subjects were ophthalmologically diagnosed. Detection ability of FDT-GSP was determined in consecutive patients, and the positive predictive value (PPV) of FDT-GSP to detect definitive glaucoma was estimated in general populations.RESULTS: Frequency-doubling technique-glaucoma screening protocol detected 83.3% and 100% of definitive glaucoma patients with an early (mean deviation [MD] > -6 dB) and more advanced stage (MD < or = -6 dB), respectively. In the population-based screening, there were 660 (4.5%) subjects who had positive FDT-GSP, including 512 in whom no visual field abnormalities (VFA) had been pointed out previously. Of them, 370 subjects underwent ophthalmologic diagnosis. Then, 266 (71.9%, 266/370) subjects had a glaucomatous disk and 167 had definitive glaucomatous VFA. Fifty-five (14.9%) and 39 (10.5%) subjects were diagnosed as having other diseases and as normal, respectively. The PPV of FDT-GSP ranged from 32.6% (167/512)-45.1% (167/370).CONCLUSIONS: Frequency-doubling technology-based screening with only a visual field test showed reasonable performance on mass screening for detection of definitive glaucoma in this study population, considering the glaucoma prevalence.     

Test-retest variability in glaucoma patients tested with C-20-1 screening-mode frequency doubling technology perimetry

PURPOSE: To investigate test-retest variability in glaucoma patients tested with C-20-1 (screening) Frequency Doubling Technology (FDT) perimetry. METHODS: Thirty-one glaucoma patients with a range of visual field defects (17 with mild, 11 with moderate, and 3 with severe defects by AGIS classification) and experienced in standard automated perimetry but not FDT perimetry were prospectively recruited. The C-20-1 screening mode of FDT was consecutively administered three times. Concordance between tests for each patient was measured by presence and severity of defects for each test location. Learning and/or fatigue effects were also evaluated using FDT test scores in which number and severity of defects was graded. RESULTS: Agreement between FDT test locations averaged 88% for any defect, but only 51% for severity of defect. Although the mean test score increased slightly over the three tests, subjects did not demonstrate a statistically significant change in test score across the three testings (P = 0.975). Among 17 patients with early glaucoma (AGIS score 1-5), two returned a normal initial FDT test, and four returned a normal second FDT test. CONCLUSIONS: Using C-20-1 FDT, concordance between tests at a given test location was high for the presence of any defect, which would be important in glaucoma screening, but was only fair for severity of defect. Six of 17 patients with early glaucoma returned normal tests during testing. This group of glaucoma patients with perimetric experience did not demonstrate a significant learning or fatigue effect with FDT screening perimetry.     

Frequency doubling technology and high-pass resolution perimetry in glaucoma and ocular hypertension

PURPOSE: To study the correlation between frequency doubling technology perimetry (FDT) and high-pass resolution perimetry (HRP) in eyes with primary open-angle glaucoma, suspect glaucoma, ocular hypertension, and in normal eyes. PATIENTS AND METHODS: Ninety-four patients (162 eyes) were studied. Visual fields were assessed by HRP, FDT screening C-20-5 and FDT threshold C-20 programs. In eyes with a discrepancy between the test results, a comprehensive clinical examination was performed, including optic disc photography and Heidelberg retinal tomography (HRT). RESULTS: There was a strong correlation between HRP global deviation and the FDT mean deviation (for FDT threshold C-20 test), and between HRP score and FDT score (for FDT screening C-20-5 ). The correlation coefficients were r = -0.83 and r = 0.77, respectively. In all, 75 eyes (46.3%) had normal HRP and FDT screening results, while 67 eyes (41.4%) showed abnormal results in both tests. In 12 eyes (7.4%) HRP was within normal limits while FDT screening was abnormal. Seven of these eyes were judged to have glaucoma; three of them had converted from ocular hypertension to glaucoma. In eight eyes (4.9%) HRP was abnormal while FDT screening was normal. Three of these were judged to have glaucoma. Thus, the sensitivity and specificity of the FDT screening test for the detection of glaucoma were 91.7% and 87.8%, respectively. CONCLUSION: There was a strong correlation between FDT threshold C-20, FDT screening C-20-5 and HRP test results. Frequency doubling technology perimetry C-20-5 represents a good screening test for the detection of optic nerve damage in open-angle glaucoma.     

Frequency doubling technology perimetry in open-angle glaucoma eyes with hemifield visual field damage: comparison of high-tension and normal-tension groups

PURPOSE: To evaluate the performance of frequency doubling technology (FDT) perimetry in open-angle glaucoma eyes with hemifield visual field damage and to compare it between open-angle glaucoma with high pressure [high-tension glaucoma (HTG)] and those with normal pressure [normal-tension glaucoma (NTG)] groups. METHODS: FDT perimetry with the N-30 full threshold protocol and standard automated perimetry (SAP) using the Humphrey Field Analyzer with the 30-2 full threshold protocol were performed in 20 eyes of 20 HTG patients and 36 eyes of 36 NTG patients with visual field damage confirmed with SAP in only one hemifield. RESULTS: There was no significant difference in demographics, the Heidelberg Retina Tomography indices, and the Humphrey Field Analyzer indices between HTG and NTG groups. Regarding the FDT perimetry results, mean deviation in the global field (P=0.009) and mean sensitivity in the SAP-spared (P=0.001) and SAP-impaired (P=0.011) hemifields were lower; the numbers of FDT abnormal test points (probability of abnormality <5%) in the SAP-spared hemifield were significantly greater (P=0.005) in HTG than in NTG groups. Eyes in which FDT results of the SAP-spared hemifield were judged as abnormal was more frequent in HTG groups (P=0.007). CONCLUSIONS: The performance of FDT perimetry to detect early or preperimetric glaucomatous functional changes should be different between HTG and NTG eyes.     

Application of frequency doubling technology perimetry in the diagnosis of glaucoma

PURPOSE: Evaluation of the frequency doubling technology perimetry in the detection of an early glaucomatous field loss. MATERIAL AND METHODS: Twenty-two patients (40 eyes), who were diagnosed with ocular hypertension were enrolled in the study. The diagnosis was made based on slit lamp examination, 3 measurements of intraocular pressure (IOP) over 21 mmHg. Standard perimetry was performed with Humphrey perimeter and SITA program (30-2 threshold). Then, all patients underwent FDT perimetry with 30-2 threshold program. Patients, who had any changes in FDT visual field had to repeat the test, to confirm the results. RESULTS: Out of 40 eyes with the normal white on white perimetry 5 eyes (5 patients) presented defects in FDT perimetry. They had optic disc c/d asymmetry > 0.1 and the nerve fiber layer defects corresponding to the visual field defects in FDT perimetry. CONCLUSION: Frequency Doubling Technology perimetry may be useful as a supplemental method of the visual field evaluation, particularly in patients where standard perimetry does not show any functional damage.     

Predictive value of frequency doubling technology perimetry for detecting glaucoma in a developing country

PURPOSE: To determine the feasibility and diagnostic precision of Frequency Doubling Technology (FDT) perimetry as a method to detect glaucoma in rural villages of a developing country. DESIGN: Cross-sectional study. METHODS: Testing included FDT perimetry (C-20-5 screening protocol), tonometry, anterior segment biomicroscopy, and dilated ophthalmoscopy in 296 rural, non-English speaking residents of Southern India over 35 years old. Participants repeated the FDT if they had a location with reduced sensitivity or an unreliable result. We defined an abnormal FDT as one location of reduced sensitivity present on both the initial and repeat examination. We determined the diagnostic precision of FDT separately for a glaucomatous optic disc, a cup to disc ratio (C/D) > or = 0.7, and a C/D > or = 0.8. RESULTS: Ninety-three percent of subjects were able to complete the test satisfactorily. With repeat FDT testing, 37% of eyes with abnormal FDT results subsequently converted to normal and 67% of eyes with unreliable results subsequently became reliable. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for a glaucomatous optic disc were 7%, 87%, 13%, 76%, and 69%, respectively; for a C/D > or = 0.7, they were 0%, 87%, 0%, 91%, and 81%, respectively; and for a C/D > or = 0.8, they were 0%, 87%, 0%, 99%, and 87%, respectively. CONCLUSION: Clinicians can use FDT perimetry to rapidly screen for glaucoma in rural villages of a developing country. FDT testing had high specificity and negative predictive value, but low sensitivity and positive predictive value. The low sensitivity suggests that FDT has limited applicability as the sole test for glaucoma screening in this population. Repeat testing of FDT results that are unreliable or suspected of being abnormal is beneficial for this screening procedure.     

Learning effects among perimetric novices in frequency doubling technology perimetry

PURPOSE: To investigate learning effects, including improvements in reliability indices, in frequency doubling technology (FDT) perimetry in subjects without glaucoma who have not undergone previous automated perimetry. DESIGN: Prospective consecutive case series. PARTICIPANTS: Eighty-one normal subjects. METHODS: Normal subjects were recruited from the University of Washington Eye Clinic who had no history of automated visual field testing. All eyes underwent complete ophthalmic examination. The C-20-5 screening mode of FDT perimetry (Zeiss-Humphrey, San Leandro, CA) was performed after appropriate instruction, including a demonstration of the frequency doubling phenomenon. If any abnormal areas were identified or there were greater than 33% fixation losses or false-positive results, then the test was readministered up to three times or until a normal result was returned. MAIN OUTCOME MEASURES: Normal FDT test. RESULTS: The mean age was 54.8 years (range, 19-94). Sixty-nine subjects (85.2%) returned a normal test after a single test administration. Nine subjects (11.1%) required two administrations, and two subjects (2.5%) required three or more administrations to return a normal test. One subject still tested unreliably after four tests. The number or severity of abnormal locations did not predict the number of trials necessary to overcome learning effects. Fixation loss was the most common reliability problem. Subjects who demonstrated learning effects did not differ significantly in age, visual acuity, refraction, or test time from those who did not. CONCLUSIONS: Some perimetric novices demonstrate learning effects in C-20-5 screening-mode FDT perimetry. Learning effects in FDT perimetry must be considered during screening for glaucoma or other ocular disease.     

Localized retinal nerve fiber layer defects and visual field abnormalities by humphrey matrix frequency doubling technology perimetry

PURPOSE: To investigate the ability of frequency doubling technology (FDT) perimetry to identify eyes with a localized retinal nerve fiber layer (RNFL) defect and normal Humphrey C30-2 SITA-Standard visual field (HVF). DESIGN: Retrospective case-control study. METHODS: Fifty-four eyes were divided into two groups, an abnormal (n = 29) and a normal (n = 25) FDT perimetry group. Approximation of the RNFL defect to the macula (angle alpha) and width of the defect (angle beta) were measured by RNFL photograph and compared between two groups. RESULTS: Angle alpha and angle beta were significantly different between two groups (P < .001 by Mann-Whitney U test, respectively). A multivariate logistic regression analysis demonstrated that only angle beta was significantly associated with FDT perimetry abnormalities (P = .002). CONCLUSIONS: Only 53.7% of the eyes with a localized RNFL defect and normal HVF had visual field abnormalities identified by FDT perimetry. Width of the RNFL defect was more strongly associated with FDT perimetry abnormalities than location of the defect.     

Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects

PURPOSE: To evaluate the clinical use of a test battery of short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), and pattern electroretinography (PERG) in predicting progressive glaucomatous visual field defects on standard automated perimetry (SAP). STUDY DESIGN: A prospective, longitudinal, observational case series. PARTICIPANTS: One hundred and fifty-two patients with primary open-angle glaucoma (POAG) with bilateral glaucomatous visual field defects on SAP were followed at 6-month intervals over a period of 30 months. MAIN OUTCOME MEASURES: Short wavelength automated perimetry, FDT, and PERG results were compared between POAG eyes with and without progressive field loss on SAP. These two groups were used to evaluate whether PERG, SWAP, and/or FDT is predictive of future progression of field loss on SAP. RESULTS: Using the criteria of progressive field loss on SAP defined by the Collaborative Normal Tension Glaucoma Study, 54 eyes (study group) of 54 POAG patients showed progressive defects, whereas 84 eyes (control group) of 84 POAG patients showed no progression. Only 11.1% (6 of 54) of the eyes with a progression of field loss on SAP showed no increase of deficits on the three functional tests before progression. Short wavelength automated perimetry detected early progressive defects on SAP in 43 of the 54 eyes (79.6%). Of these 54 POAG eyes, FDT showed progressive deficits in 40 eyes (74.1%), whereas PERG amplitude P1N2 showed progressive deficits in 35 eyes (64.8%) before progression of field loss on SAP. A test battery consisting of SWAP and PERG P1N2-amplitude was able to detect 88.9% of eyes before a prediction of field loss on SAP. When comparing the results of the two functional tests, SWAP and FDT in the 84 eyes without progression of field loss on SAP between baseline and at 30 months, SWAP and FDT showed progressive deficits in 34.5% and 35.7%, respectively. CONCLUSIONS: All three tests (SWAP, FDT, and PERG) have been successful in detecting glaucoma eyes with a future progression of standard visual field defects. A test battery of SWAP and PERG P1N2-amplitude improved the power to predict these progressive defects on SAP. It remains to be seen whether the long-term follow-up in POAG eyes will improve the false-positive rate of SWAP and FDT.     

Frequency-doubling perimetry in patients following penetrating keratoplasty

PURPOSE: Perimetry using a frequency-doubling technique (FDT perimetry) is becoming established as a new diagnostic tool to detect early visual field losses. The aim of this study was to evaluate the diagnostic usefulness of an FDT perimetry protocol (C-20-5) in patients after penetrating keratoplasty (PK) and to assess whether this method is influenced by postoperative corneal topographic changes. METHODS: Thirty-six patients (age 40 +/- 13, median 41 years) following PK and 68 age-matched controls were included in this study. The postoperative interval was 21 +/- 19, median 14 months. Patients with preexisting glaucoma or any postoperative intraocular pressure elevation were excluded. The indications for PK were keratoconus in 82%, Fuchs dystrophy in 15%, and secondary bullous keratopathy in 3%. In 19 patients keratoplasty was performed in 1 eye. FDT perimetry was evaluated in both eyes to judge intraindividual variability. FDT perimetry was done using the screening strategy, which begins testing at the normal 5% probability level. If a stimulus is not detected, further targets are presented. FDT viewfinder and statistics software were used for case-wise recalculation of all missed localized probability levels. RESULTS: Neither mean overall FDT score (0.8 +/- 1.9, median 0.0 versus 0.9 +/-1.0, median 0.0) nor total test time (44 +/- 4.7, median 44 versus 44 +/- 4.2, median 42 seconds) showed significant differences between patients after PK and controls (P = 0.5). There was also no significant difference of mean FDT score between eyes after keratoplasty (0.8 +/- 1.9, median 0.00) and nonoperated contralateral eyes (0.9 +/- 2.0, median 0.00, P = 0.8) in the same patient. No significant correlation between FDT score and visual acuity as well as corneal keratometric astigmatism could be found in patients after PK and in normals (r < 0.2, P = 0.3). In patients after PK, FDT score and examination time were statistically independent of keratometric astigmatism (P = 0.7), topographic astigmatism (P = 0.4), spherical equivalent (P = 0.5), central corneal thickness (P = 0.7), and interval of postoperative follow-up (P = 0.6). CONCLUSIONS: Perimetry using the FDT protocol (C-20-5) seems to be feasible in patients after PK and does not depend on postoperative topographic changes of the cornea. This method allows valid information on visual field abnormality in patients after PK The results indicate that this method may be helpful as a supplement to detect early glaucomatous damage in patients after PK.     

Does frequency doubling technology perimetry reliably detect neurological visual field defects?

AIM: To determine the ability of frequency doubling technology (FDT) perimetry to detect visual field defects of neurological origin. METHODS: A total of 15 eyes of nine patients who all had complete hemianopias or quadrantanopias underwent the FDT 20-5 screening mode test and Humphrey 24-2 SITA Fast visual field test (HFA). The FDT results were scored according to the number of abnormal test locations (out of a maximum of 4) in each affected quadrant. FDT locations showing a defect of P< 2% were considered abnormal. RESULTS: Of the 15 eyes, six showed complete superior quadrantanopic and nine complete hemianopic field defects on HFA. Of 96 FDT test locations in these quadrants or hemifields only 38 were abnormal on FDT testing (40%). For the quadrantanopic field defects, five out of 24 locations were abnormal (21%). For the hemianopic field defects, 33 out of 72 locations were abnormal (49%). In three eyes (two with quadrantanopias and one with complete hemianopia), FDT perimetry failed to demonstrate any corresponding abnormality. CONCLUSIONS: The FDT screening test can fail to demonstrate complete hemianopic and quadrantanopic field defects. Users should be aware of this deficiency when using FDT to screen for field defects.     

Performance of efficient test procedures for frequency-doubling technology perimetry in normal and glaucomatous eyes

PURPOSE: To validate the clinical performance of two new efficient threshold-estimation procedures for frequency-doubling technology (FDT) perimetry in both visually normal individuals and patients with glaucomatous visual field loss. METHODS: Forty-one normal subjects (mean age, 48.3 +/- 11.6 years) and 50 patients with glaucomatous visual field loss (mean age, 72.7 +/- 10.0 years) were tested. Some of these participants were retested within a 3-month period. FDT perimetry was performed on a color monitor driven by a visual-stimulus-generating video board, with stimulus parameters designed to closely mimic those of the commercial FDT test. Visual field sensitivity was measured using three procedures: a modified binary search (MOBS) identical with the one used in the commercial FDT device, a rapid efficient binary search (REBS), and a procedure the uses Bayesian methods (zippy estimation of sequential testing; ZEST). The selection of optimum parameters for REBS and ZEST were based on results from previous simulations. RESULTS: Both ZEST and REBS were 40% to 50% faster than MOBS. All three methods produced similar visual field sensitivity measures, with 95% of the differences occurring between +/-2 dB for normal subjects and +/-3 dB for glaucoma patients. Test-retest performance was similar for all three procedures. CONCLUSIONS: The test time for full-threshold FDT perimetry can be approximately halved, by using either the ZEST or REBS procedure, without affecting the accuracy or reliability of the measurements. These findings in normal subjects and patients with glaucoma provide clinical confirmation of our previous investigations of these test strategies that use computer simulation.     

Corneal thickness measurements and frequency doubling technology perimetry abnormalities in ocular hypertensive eyes

OBJECTIVE: It has been suggested that some patients currently diagnosed with ocular hypertension (OHT) may have thicker than average corneas that result in an overestimation of their true intraocular pressure. Consequently, patients with OHT with greater corneal thickness may be at a lower risk for functional glaucomatous damage, including visual field loss measured with frequency doubling technology (FDT) perimetry. The purpose of this study was to evaluate the frequency of FDT perimetry deficits in patients with OHT and to correlate these findings with central corneal thickness (CCT) measurements. DESIGN: Observational case control study. PARTICIPANTS AND CONTROLS: Sixty-five patients with OHT with normal optic discs and normal standard achromatic automated perimetry (SAP) visual fields and 52 normal control subjects. METHODS: All participants underwent SAP, FDT perimetry, and CCT measurements using ultrasound pachymetry. MAIN OUTCOME MEASURES: CCT measurements in patients with OHT with abnormal repeatable FDT test results were compared with CCT measurements in patients with OHT with normal FDT results. In addition, CCT measurements in patients with OHT were compared with CCT measurements in normal control subjects. RESULTS: Fourteen of 65 patients with OHT (21.5%) demonstrated repeatable FDT abnormalities. The mean CCT of patients with OHT with abnormal FDT results was significantly lower than the mean CCT of patients with OHT with normal FDT results (542+/-35 microm versus 575+/-35 microm; P = 0.003). The mean CCT in the normal control group was 556+/-36 microm. The mean CCT in patients with OHT with normal FDT results was significantly higher than in normal subjects (P = 0.008). No statistically significant difference was found between mean CCT in normal subjects and in patients with OHT with abnormal FDT results (P = 0.18). CONCLUSIONS: Patients currently diagnosed with OHT, but with visual field loss detected by FDT perimetry, had significantly lower CCT measurements than patients with OHT with normal FDT results. These findings suggest that patients with OHT with thinner corneas are more likely to develop early glaucomatous functional damage and that CCT measurements should be taken into account when assessing risk for the development of glaucoma among OHT subjects.