Frequency Doubling Technology Results Research Articles

Visual Field Loss, Quality of Life and Ocular Biometric Parameters: A Cross Sectional Study of Taiwanese Adults

Purpose: To evaluate the severity of visual field loss in Taiwanese adults and assess the associations between visual field loss detected by frequency doubling technology (FDT) perimetry and vision-related quality of life (QoL) in Taiwanese adults. Methods: A total of 206 eyes from 206 subjects were included. Each subject was examined using FDT (N-30 threshold test) perimetry, optical coherence tomography (OCT), noncontact tonometry, cycloplegic refractometry, and National Eye Institute Visual Functioning Questionnaire 25 items (NEI VFQ-25). Results of FDT tests were classified into four groups (normal, early, moderate, and severe defects) using FDT probability map analysis. OCT parameters included central cornea thickness (CCT), thickness of retinal nerve fiber layer (RNFL), ganglion cell complex (GCC), focal loss volume (FLV), and global loss volume (GLV) of GCC. The global score, subscales of near and distance activities of VFQ were calculated. Linear regression analysis was used to analyze the factors associated with visual field loss. Kruskal-Wallis analysis was used to examine the relationship between FDT results and vision-related QoL. Results: Among the 206 subjects, 72 were normal. The numbers of participants having early, moderate, and severe visual field loss were 101, 27, and 6. Moderate visual field defect was associated with CCT, GLV, GCC, and SE when compared to the subjects with normal response. Kruskal-Wallis analysis indicated that those with moderate visual field loss determined by FDT had worse vision related QoL and more difficulties in distance activities of VFQ (p=0.01) than people with normal response. Conclusion: Moderate visual field loss detected by FDT was associated with vision-related QoL in young adults. Further study is warranted to determine the potential of visual field loss as a predicting factor for vision loss related QoL.

Recognizing patterns of visual field loss using unsupervised machine learning.

Glaucoma is a potentially blinding optic neuropathy that results in a decrease in visual sensitivity. Visual field abnormalities (decreased visual sensitivity on psychophysical tests) are the primary means of glaucoma diagnosis. One form of visual field testing is Frequency Doubling Technology (FDT) that tests sensitivity at 52 points within the visual field. Like other psychophysical tests used in clinical practice, FDT results yield specific patterns of defect indicative of the disease. We used Gaussian Mixture Model with Expectation Maximization (GEM), (EM is used to estimate the model parameters) to automatically separate FDT data into clusters of normal and abnormal eyes. Principal component analysis (PCA) was used to decompose each cluster into different axes (patterns). FDT measurements were obtained from 1,190 eyes with normal FDT results and 786 eyes with abnormal (i.e., glaucomatous) FDT results, recruited from a university-based, longitudinal, multi-center, clinical study on glaucoma. The GEM input was the 52-point FDT threshold sensitivities for all eyes. The optimal GEM model separated the FDT fields into 3 clusters. Cluster 1 contained 94% normal fields (94% specificity) and clusters 2 and 3 combined, contained 77% abnormal fields (77% sensitivity). For clusters 1, 2 and 3 the optimal number of PCA-identified axes were 2, 2 and 5, respectively. GEM with PCA successfully separated FDT fields from healthy and glaucoma eyes and identified familiar glaucomatous patterns of loss.

Glaucomatous Patterns in Frequency Doubling Technology (FDT) Perimetry Data Identified by Unsupervised Machine Learning Classifiers

PurposeThe variational Bayesian independent component analysis-mixture model (VIM), an unsupervised machine-learning classifier, was used to automatically separate Matrix Frequency Doubling Technology (FDT) perimetry data into clusters of healthy and glaucomatous eyes, and to identify axes representing statistically independent patterns of defect in the glaucoma clusters.MethodsFDT measurements were obtained from 1,190 eyes with normal FDT results and 786 eyes with abnormal FDT results from the UCSD-based Diagnostic Innovations in Glaucoma Study (DIGS) and African Descent and Glaucoma Evaluation Study (ADAGES). For all eyes, VIM input was 52 threshold test points from the 24-2 test pattern, plus age.ResultsFDT mean deviation was −1.00 dB (S.D. = 2.80 dB) and −5.57 dB (S.D. = 5.09 dB) in FDT-normal eyes and FDT-abnormal eyes, respectively (p<0.001). VIM identified meaningful clusters of FDT data and positioned a set of statistically independent axes through the mean of each cluster. The optimal VIM model separated the FDT fields into 3 clusters. Cluster N contained primarily normal fields (1109/1190, specificity 93.1%) and clusters G1 and G2 combined, contained primarily abnormal fields (651/786, sensitivity 82.8%). For clusters G1 and G2 the optimal number of axes were 2 and 5, respectively. Patterns automatically generated along axes within the glaucoma clusters were similar to those known to be indicative of glaucoma. Fields located farther from the normal mean on each glaucoma axis showed increasing field defect severity.ConclusionsVIM successfully separated FDT fields from healthy and glaucoma eyes without a priori information about class membership, and identified familiar glaucomatous patterns of loss.

Changes in Frequency-Doubling Perimetry in Patients with Type I Diabetes prior to Retinopathy

Purpose. To evaluate the ability of frequency-doubling technology (FDT) perimetry in detecting visual field defects in young adults with type I diabetes prior to retinopathy or with minor retinovascular changes. Methods. This comparative cross-sectional study included 30 healthy subjects and 73 age-matched patients with type I diabetes mellitus. All subjects underwent a full ocular examination including an FDT with the threshold C-20-5 strategy. Only one eye per subject was randomly included in the statistical analysis. FDT results and time to perform the test were compared between the groups. Results. The mean age was 27.1 years in the control group and 26.6 years in the diabetic group (P = 0.875). The mean period from the onset of diabetes was 12.6 ± 6.7 years, while minimal retinovascular changes were observed in 18 eyes. Mean deviation of FDT did not differ between the groups. Although global indices of FDT were within normal limits, pattern standard deviation of FDT was higher in the diabetic group (P = 0.035). The area under the receiver operating characteristic curve was 0.647 for pattern standard deviation of FDT (standard error = 0.052; P = 0.017). Conclusion. FDT can detect retinal dysfunctions in diabetic patients prior to the onset of significant vascular complications.

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.

Potential of Stratus Optical Coherence Tomography for Detecting Early Glaucoma in Perimetrically Normal Eyes of Open-angle Glaucoma Patients With Unilateral Visual Field Loss

To evaluate the potential of stratus optical coherence tomography (OCT) for detecting early glaucoma. Fifty-two open-angle glaucoma patients with unilateral visual field loss detected by standard automatic perimetry were tested using stratus OCT and frequency doubling technology (FDT) N-30. Fifty-two perimetrically normal eyes were enrolled and divided into 2 groups: eyes with normal OCT results and eyes with abnormal OCT results. FDT parameters and scores were compared between the 2 groups. We evaluated the topographic relationship of the OCT-measured retinal nerve fiber layer (RNFL) defects with the FDT-measured visual field loss and glaucomatous optic neuropathy. In eyes with abnormal OCT results, the percentage of eyes with abnormal FDT results was significantly higher (P<0.001); FDT mean deviation, pattern standard deviation, and scores were significantly worse than those with normal OCT results (P=0.005, P<0.001, P<0.001, respectively); and the OCT-measured RNFL defects showed good topographic agreement with the FDT-measured visual field loss and glaucomatous optic neuropathy. RNFL defects detected by stratus OCT were associated with FDT visual field loss. Stratus OCT can detect early glaucoma sooner than standard automatic perimetry.

Rarebit Perimetry and Frequency Doubling Technology in Patients with Ocular Hypertension

To test the capability of rarebit perimetry (RP), a recent non-conventional perimetric technique, in detecting early functional damage in subjects with ocular hypertension (OHT) and to compare RP findings with those obtained by frequency-doubling technology (FDT) perimetry. Thirty patients with OHT were matched with 30 healthy subjects. All were tested with RP and FDT. Frequency-doubling technology mean deviation (MD) and pattern standard deviation (PSD), as well as RP mean hit rate (MHR), of the two groups were analyzed. The agreement between the two techniques was tested by Kappa analysis. In the OHT group the mean (SD) FDT MD was 0.5 (2.1), the mean (SD) FDT PSD was 4.2 (1.6), and the mean (SD) RP MHR was 81.4 (6.7). In the control group, corresponding values were mean (SD) FDT MD 1.1 (1.4), mean (SD) FDT PSD 3.0 (0.3), mean (SD) RP MHR 96.2 (2.0). The differences between the two groups were not significant for the studied indexes. Eleven (36.6%) out of the 30 OHT eyes had abnormal RP results; 12 (40.0%) eyes had abnormal FDT results. Five (16.6%) eyes had abnormal RP and FDT findings. Only 1 eye (3.3%) in the control group had abnormal RP results and 3 eyes (10.0%) had abnormal FDT results. RP and FDT showed a moderate agreement (Kappa=0.43; 95% CI: 0.42 to 0.51). RP and FDT showed VF defects not shown in standard automated perimetry in the OHT group. This may be indicative of an increased risk in developing glaucoma, even if a gold standard for detecting subtle defects is not currently available. RP has the additional advantage of not requiring any expensive device to be used. The poor agreement between these techniques in identifying eyes with early damage warrants further investigations. Large longitudinal studies are needed before defining the role of RP in early glaucoma diagnosis.

The Results of Screening Frequency Doubling Technology Perimetry in Different Locations of the Community

To determine the effect of screening location on the frequency of abnormal test results with Frequency Doubling Technology (FDT) perimetry. Retrospective cross-sectional study. The Vision Screening Outreach Project conducted FDT testing in community sites surrounding Portland, Oregon. The sites were separated into a specific location type: health care clinics, work sites, senior centers, festivals/fairs, food banks/shelters, and other locations. These locations were compared for differences in the proportion of screening failures. Screening failure (defined as a repeatable, abnormal FDT result in either eye). There were 9052 participants from 211 locations in Oregon and Washington. On initial FDT testing, the right and left eye had abnormal results in 18% (1654/9052) and 21% (1918/9052) of participants. Of those with abnormal FDT results, approximately 30% of eyes reverted to normal on repeat testing. Overall, 13% of participants were screening failures. Screening failure was highly associated with age (P<0.001). After controlling for age, participants at senior centers (P<0.001) were most likely to be screening failures and participants at work sites (P=0.006) were least likely to be screening failures when compared with health clinics. An investigator should repeat an initially abnormal FDT result when screening with FDT. Age and the location of testing influence the probability of a screening failure. Screening in senior centers is most likely to result in screening failure. However, only a randomized controlled trial can determine the true benefit of FDT screening in these locations.

Performance of Frequency-Doubling Technology Perimetry in a Population-Based Prevalence Survey of Glaucoma: The Tajimi Study

To evaluate the performance of frequency-doubling technology (FDT) perimetry in a population-based glaucoma prevalence survey. Population-based cross-sectional study. Participants older than 40 years randomly selected from the population of Tajimi City. Each participant underwent screening ophthalmic examinations including a visual field test using FDT with the C-20-1 screening protocol. A diagnosis of glaucoma was determined by glaucoma specialists with another detailed visual field test using Humphrey Field Analyzer (HFA; Humphrey Instruments, San Leandro, CA) with the 30-2 Swedish interactive threshold algorithm standard protocol and stereoscopic disc photographs. The ratios of reliable FDT results and the sensitivity and specificity for detecting glaucoma in a general population. Of 5784 eyes of 2892 participants (age range, 40-92 years; refractive error, -23 to 11 diopters) in whom FDT was performed in both eyes, reliable results (< or =33% fixation loss and < or =33% false-positive errors) were obtained in 5707 eyes (98.7%), including 2871 right eyes (99.3%) and 2836 left eyes (98.1%) with a significant bilateral difference (P<0.001, chi-square test). The rate of reliable FDT results did not differ between men and women (P = 0.81) but decreased with age. In 5582 eyes with reliable FDT results, FDT showed 1 or more abnormal points in the visual field in 502 eyes (9.0%), including 388 (7.3%) of 5295 normal eyes, 19 (16.4%) of 116 eyes of glaucoma suspects, and 95 (55.6%) of 171 eyes with definite glaucoma. The sensitivity and specificity values for detecting definite glaucoma were 55.6% and 92.7%, respectively. The positive and negative predictive values were 18.9% and 98.5%, respectively. In further analyses stratified with the mean deviation (MD) of the HFA, the sensitivities were 32.1%, 48.4%, 73.7%, and 96.6% for detecting definite glaucoma with an MD of more than -2 dB, an MD of -2 dB or less and more than -5 dB, an MD of -5 dB or less and more than -8 dB, and an MD of -8 dB or less, respectively. In a population-based glaucoma screening study, FDT perimetry with the C-20-1 screening protocol was reliably performed in more than 98% of participants. The sensitivity for detecting glaucomatous visual field damages, especially early damage, was not sufficiently high, whereas the specificity was high.

Frequency Doubling Technology and Scanning Laser Tomography in Eyes With Generalized Enlargement of Optic Disc Cupping

To characterize functional and structural changes in eyes with generalized enlargement of optic disc cupping (vertical cup/disc ratio > or = 0.8), normal intraocular pressure, normal standard achromatic automated perimetry (SAP) results, and no other ophthalmoscopic findings suggesting glaucoma (large C/D eyes) using frequency doubling technology (FDT) and the Heidelberg Retina Tomograph (HRT). This comparative observational case series included 30 large C/D eyes (30 subjects), 17 eyes (17 patients) with early-stage normal tension glaucoma with generalized enlargement of optic disc cupping (NTG eyes), and 25 eyes from 25 normal subjects (normal eyes). Results with Humphrey 30-2, FDT N-30 threshold programs, and HRT were compared among these groups. Large C/D eyes were subdivided into FDT-normal and -abnormal eyes according to the predetermined criteria and HRT parameters were compared among them. No significant difference was seen in HRT parameters between the large C/D and NTG eyes. In the large C/D eyes, FDT mean deviation was lower than in the normal eyes and higher than in the NTG eyes, whereas FDT pattern standard deviation was smaller than in the NTG eyes (P = 0.02-0.03). Among HRT parameters, only cup shape measure (CSM) showed significant negative correlation with FDT mean deviation in the large C/D eyes. Between FDT-normal and -abnormal subgroups, only CSM showed significant difference (P < 0.01). Frequency doubling technology showed abnormalities in large C/D eyes. Only CSM showed significant correlation with FDT result and difference between those with normal and abnormal FDT results. In management of large C/D eyes, FDT and CSM will be useful to detect functional and structural change.

Corneal Thickness and Functional Damage in Patients with Ocular Hypertension

To correlate functional damage over time detected by standard automated perimetry (SAP) and frequency doubling technology (FDT) with central corneal thickness (CCT) in patients with ocular hypertension (OHT). Seventy-eight OHT patients underwent CCT measurements, SAP, and FDT (the latter two also after 12 and 18 months). Patients were divided into three equally sized groups of 26 patients each: thin (< 540 microm), normal (540-580 microm), and thick cornea (> 580 microm). The frequency of abnormal FDT and SAP results was analyzed over time (Pearson chi2 test). Six of 26 patients with thin corneas (23.1%) presented an abnormal FDT test at baseline, compared to 1 of 26 (3.8%) in the normal thickness cornea group and 1 of 26 (3.8%) in the thick cornea group. After 12 months, the abnormal FDT tests were as follows, respectively: 9 of 26 (34.6%), 2 of 26 (7.7%), and 2 of 26 (7.7%). For SAP the abnormal results were as follows, respectively: 8 (30.1%), 5 (19.2%), and 2 (7.7%). After 18 months, the abnormal FDT tests were as follows, respectively: 16 (61.5%), 5 (19.2%), and 5 (19.2%). For SAP, the abnormal results were as follows, respectively: 10 (38.5%), 5 (19.2%), and 2 (7.7%). OHT patients with thinner corneas have a greater risk of developing functional damage over time.

Correlation Between Frequency Doubling Technology Perimetry and Scanning Laser Polarimetry in Glaucoma Suspects and Glaucomatous Eyes

The aim of this study was to determine the relationship between the frequency doubling technology (FDT) screening algorithm and parapapillary retinal nerve fiber layer (RNFL) thickness in the eyes of glaucoma suspects and patients with open angle glaucoma. FDT C20-1 screening program and a scanning laser polarimetry (SLP) system (GDx-NFA) was used to assess 53 glaucomatous eyes, 53 glaucoma suspects and 36 normal control eyes. In glaucomatous eyes, there were correlations between the FDT the screening algorithm and RNFL retardation values in several polarimetric indices, most significantly "inferior thickness" (r = -0.321, P = 0.029). In the eyes of glaucoma suspects, however, we observed no correlation between the FDT results and RNFL retardation values (r = 0.080, P > 0.05, "inferior thickness"). In glaucomatous eyes, the abnormal scores obtained with FDT screening program correlated negatively with RNFL retardation values, as measured by SLP. Despite poor correlation between the FDT abnormal score and RNFL retardation value in glaucoma suspects, detection of abnormality using the FDT screening protocol may aid in the assessment of early glaucomatous structural damage.

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 μm versus 575±35 μm; P = 0.003). The mean CCT in the normal control group was 556±36 μm. 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.

The Ability of Frequency Doubling Technology to Detect Abnormality of Visual Function in Early Glaucoma

To evaluate the ability of the Frequency Doubling Technology(FDT) threshold test in detecting abnormality of visual function in early glaucoma patients. The C-20 full threshold test of FDT was performed on 34 normal-tension glaucoma(NTG) patients and 39 primary open-angle glaucoma(POAG) patients with visual field defects limited to the upper or lower hemi-field as detected by Humphrey Field Analyzer(HFA) and on 79 normal control subjects. Optic disk findings and FDT results corresponding to the intact hemi-field were evaluated. FDT abnormalities in normal subjects were calculated as false positive rates in FDT. The sensitivity and specificity of FDT, calculated based on optic disk findings, were 75.0% and 61.1% in POAG, and 61.1% and 66.7% in NTG, respectively, while the false positive rate in normal subjects was 11.4%. FDT can detect glaucomatous functional abnormality earlier than HFA.

Effect of Decreased Retinal Illumination on Frequency Doubling Technology

Purpose: To investigate the effect of changes in retinal illumination on Frequency Doubling Technology (FDT). Methods: Five eyes, of 5 adults who were free from identifiable ocular pathology, were examined using the Snellen chart and the Pelli-Robson chart, conventional automated perimetry, and the full threshold N-30 program of FDT. Each test was performed with and without a 0.9, 1.5, or 2.4 log unit neutral-density (ND) filter placed before the eye. Furthermore, the influence of pupil diameter on FDT test results was compared after treatment with pilocarpine or cyclopentolate with the influence of ND filters. Results: All tests showed a decrease in sensitivity with decreasing retinal illumination. Frequency Doubling Technology showed an especially pronounced and significant decrease in sensitivity. The maximum mean threshold difference in FDT results with ND filter was 31.2 dB while that with the Humphrey Field Analyzer and the Pelli-Robson chart were 13.3 dB and 0.66 log contrast, respectively. The mydriatic state of the pupil increased the sensitivity of FDT and the miotic state decreased it to about the same extent as the the 0.9 ND filter. Conclusion: The change in retinal illumination has more impact on FDT than on spatial contrast tests and conventional automated perimetry. It is important to take this into account in evaluating FDT results.

Identification of glaucoma-related visual field abnormality with the screening protocol of frequency doubling technology

Purpose: To evaluate the predictive power of frequency doubling technology to distinguish glaucoma suspects from persons with glaucoma visual field loss. Methods: A consecutive series of 76 subjects referred to a glaucoma service underwent perimetry in one eye with frequency doubling technology in a screening mode and Humphrey 24-2 threshold testing in random order, and had optic disk and clinical nerve fiber layer grading. Results: All subjects performed perimetry with both instruments satisfactorily, with an average test time of 1.8 ± 0.7 minutes per eye for the frequency doubling technology (instrument time). Of 33 eyes classified as abnormal by glaucoma hemifield test, 91% (30/33) were abnormal on frequency doubling technology (two or more abnormal locations of 17), whereas 94% (31/33) of glaucoma suspects with normal Humphrey fields had normal results with frequency doubling technology. Frequency doubling technology results were highly correlated with Humphrey mean deviation by linear regression ( r 2 = .74, P = .047) and with corrected pattern standard deviation probability value. A frequency doubling technology error score for each quadrant of the field was highly correlated with the number of severely abnormal points per quadrant in Humphrey threshold tests ( r 2 = .63, P = .034). There was close agreement between clinical examination of the optic disk and nerve fiber layer and frequency doubling technology results. Three-level quantification of abnormality in frequency doubling technology results did not add to diagnostic accuracy. Conclusion: Frequency doubling technology testing shows promise as a screening method in glaucoma.