Recent developments in automated perimetry in glaucoma diagnosis and management

Attenuated Amplitude of Pattern Electroretinogram in Glaucoma Patients with Choroidal Parapapillary Microvasculature Dropout

This study aims to investigate whether parapapillary choroidal microvasculature dropout (MvD) is related to visual function measured by pattern electroretinogram (PERG) in glaucomatous eyes with β-zone parapapillary atrophy (PPA). A total of 79 patients with open angle glaucoma and preperimetric glaucoma with β-zone PPA was included in this cross-sectional study. Through the deep layer of the Swept-source optical coherence tomography angiography image, the angular width and the area of MvD were measured. Visual function was evaluated with a standard automated perimetry and PERG. N95 and P50 PERG amplitudes in eyes with MvD were noticeably decreased compared to those without MvD (p = 0.004 and p = 0.007, respectively), although the mean deviation was not significantly different (p = 0.107). The lower N95 amplitude was associated with the presence of MvD (β = −0.668, p = 0.017) and wider angular width of MvD (B = −7.612, p = 0.014). Old age (p = 0.001), average ganglion cell’s inner plexiform layer thickness (p = 0.003), and the presence of MvD (p = 0.020) were significantly related to low N95 amplitude. Association between the presence and extent of the MvD and PERG amplitudes suggests that the presence of MvD has relevance to the generalized dysfunction of retinal ganglion cells.

Detection of Early Glaucomatous Damage: Performance of Summary Statistics From Optical Coherence Tomography and Perimetry

Purpose

To evaluate the diagnostic performance of optical coherence tomography (OCT) and visual field (VF) summary statistics (metrics) that are available in OCT and VF reports.

Methods

OCT disc and macular scans and 24-2 and 10-2 VFs were obtained from 56 healthy control (HC) eyes/participants and 61 eyes/patients with 24-2 mean deviation of better than –6 dB. All metrics were obtained from OCT radial, circle, and posterior pole cube scans and 24-2 and 10-2 VFs. Their diagnostic performances were evaluated, in isolation and in combinations. For specificity, the 56 HC eyes were used. For sensitivity, 40 of the 61 patient eyes were deemed likely glaucomatous based on an automated topographic method that evaluates structure–function (S–F) agreement. Any 1 of these 40 eyes not judged as abnormal by any given metric was considered a false negative.

Results

All single OCT and VF metrics misclassified HCs as glaucomatous and missed likely glaucomatous eyes. The best performing single metric was the temporal inferior thickness of the 3.5-mm circle scan, with 96% specificity and 83% sensitivity. Combinations of OCT–OCT and OCT–VF metrics markedly improved specificity. A newly proposed metric that evaluates structure–structure (S–S) agreement at a hemifield level had the highest accuracy. This S–S metric had 98% specificity and 80% sensitivity.

Conclusions

OCT and VF metrics, single or in combinations, have only moderate sensitivity for eyes with early glaucoma.

Translational Relevance

OCT and VF metrics combinations evaluating S–S or S–F agreement can be highly specific, which is an important implication for clinical and research purposes.

Comparison of ZETA Fast (PTS) (Optopol Technology) and Humphrey SITA Fast (SFA) (Carl Zeiss Meditec) Perimetric Strategies

Purpose

To compare two threshold strategies for visual field assessment, ZETA Fast (Optopol Technology) and Humphrey SITA Fast (Carl Zeiss Meditec), in controls and subjects with glaucoma. Patients and Methods. A prospective case-control study was carried out in which the clinical practice study included 26 controls and 26 glaucoma subjects. Testing for each strategy was monocular. Quantitative comparisons of mean deviation (MD), pattern standard deviation (PSD), visual field index (VFI), and test duration were made using two one-sided t-tests and Wilcoxon signed-rank tests. Confusion matrices were constructed to assess Optopol's detection as a proxy for Zeiss's detection of early glaucomatous defects. Receiver operating characteristic (ROC) curves were used to assess MD and PSD's discriminability.

Results

The difference in MD values (Optopol-Zeiss) was within the margin for controls (difference = 0.36, p=0.06), but not for glaucomatous subjects (difference = 2.16, p=1.0). The Optopol strategy took longer than the Zeiss strategy in both controls (difference = 23 seconds, p=0.001) and glaucomatous subjects (difference = 49 seconds, p < 0.001). PSD values were higher and VFI values were lower from Optopol in glaucomatous subjects (p < 0.001 and p=0.002). Optopol was 92% sensitive in capturing early glaucomatous defects with MD <−2 when compared to Zeiss (p < 0.001). ROC analysis shows Optopol yields higher discriminability than Zeiss for MD/PSD indices.

Conclusions

Both strategies enable effective identification of glaucomatous defects within 6 minutes; they also offer high sensitivity with a high correlation in global indices between the two strategies. The Optopol strategy is an alternative to the Zeiss counterpart with the limitation of a marginally longer testing protocol but a higher sensitivity of detecting glaucomatous defects.

Comparison of the SITA Faster-a new visual field strategy with SITA Fast strategy

AIM

To compare visual field defects using the Swedish Interactive Thresholding Algorithm (SITA) Fast strategy with SITA Faster strategy, a newly developed time-saving threshold visual field strategy.

METHODS

Ninety-three participants (60 glaucoma patients and 33 normal controls) were enrolled. One eye from each participant was selected randomly for the study. SITA Fast and SITA Faster were performed using the 24-2 default mode for each test. The differences of visual field defects between the two strategies were compared using the test duration, false-positive response errors, mean deviation (MD), visual field index (VFI) and the numbers of depressed test points at the significant levels of P<5%, <2%, <1%, and <0.5% in probability plots. The correlation between strategies was analyzed. The agreement between strategies was acquired by Bland-Altman analysis.

RESULTS

Mean test durations were 246.0±60.9s for SITA Fast, and 156.3±46.3s for SITA Faster (P<0.001). The test duration of SITA Faster was 36.5% shorter than SITA Fast. The MD, VFI and numbers of depressed points at P<5%, <2%, <1%, and <0.5% in probability plots showed no statistically significant difference between two strategies (P>0.05). Correlation analysis showed a high correlation for MD (r=0.986, P<0.001) and VFI (r=0.986, P<0.001) between the two strategies. Bland-Altman analysis showed great agreement between the two strategies.

CONCLUSION

SITA Faster, which saves considerable test time, has a great test quality comparing to SITA Fast, but may be not directly interchangeable.

Nomograms for Converting Perimetric Sensitivity From Full Threshold and SITA Fast to SITA Standard in Patients With Glaucoma and Healthy Subjects

Purpose

The purpose of this study was to develop nomograms for converting Full Threshold (FT) and Swedish Interactive Threshold Algorithm (SITA) Fast (SF) tests to SITA Standard (SS) tests with the Humphrey Field Analyzer in patients with glaucoma and healthy subjects.

Methods

One eye each of 49 patients with glaucoma and 50 healthy subjects was tested in 4 and 2 sessions (each containing the 3 strategies), respectively, over 4 weeks. The difference between pointwise Best Available Estimate (BAE; mean of all FT tests) and SS sensitivity at each session was used to derive four nomograms. Nomogram accuracy was assessed by: (1) comparing the converted FT to actual SS sensitivity (omitting the test session used to derive the nomogram) and (2) comparing the distribution of the differences between the converted and actual SS sensitivity to the actual SS test-retest differences. The process was repeated for SF and healthy subjects.

Results

In patients with glaucoma, 39.85% and 59.69% of the conversion differences from FT were within 1 dB and 2 dB of the mean, respectively. The respective figures for SF were 45.69% and 65.04%, and in healthy subjects, they were 54.34% and 76.48% for FT and 61.17% and 82.66% for SF. The difference in the mean conversion and test-retest differences was <0.5 dB for all comparisons, with an overlap in distributions ranging from 78.75% to 85.24. There was no association between conversion differences and BAE for either FT or SF in either subject group.

Conclusions

Nomograms to convert FT and SF tests to SS tests yield accuracies that are negligibly different from test-retest differences with SS.

Translational Relevance

Nomograms allow direct comparisons between different perimetric strategies for a more comprehensive assessment of visual field change.

A novel Bayesian adaptive method for mapping the visual field

Measuring visual functions such as light and contrast sensitivity, visual acuity, reading speed, and crowding across retinal locations provides visual-field maps (VFMs) that are extremely valuable for detecting and managing eye diseases. Although mapping light sensitivity is a standard glaucoma test, the measurement is often noisy (Keltner et al., 2000). Mapping other visual functions is even more challenging. To improve the precision of light-sensitivity mapping and enable other VFM assessments, we developed a novel hybrid Bayesian adaptive testing framework, the qVFM method. The method combines a global module for preliminary assessment of the VFM's shape and a local module for assessing individual visual-field locations. This study validates the qVFM method in measuring light sensitivity across the visual field. In both simulation and psychophysics studies, we sampled 100 visual-field locations (60° × 60°) and compared the performance of qVFM with the qYN procedure (Lesmes et al., 2015) that measured light sensitivity at each location independently. In the simulations, a simulated observer was tested monocularly for 1,000 runs with 1,200 trials/run, to compare the accuracy and precision of the two methods. In the experiments, data were collected from 12 eyes (six left, six right) of six human subjects. Subjects were cued to report the presence or absence of a target stimulus, with the luminance and location of the target adaptively selected in each trial. Both simulations and a psychological experiment showed that the qVFM method can provide accurate, precise, and efficient mapping of light sensitivity. This method can be extended to map other visual functions, with potential clinical signals for monitoring vision loss, evaluating therapeutic interventions, and developing effective rehabilitation for low vision.

Predicting conversion to glaucoma using standard automated perimetry and frequency doubling technology

PURPOSE

To test the hypothesis that development of glaucomatous visual fields can be predicted several years earlier from prior visual field information.

METHODS

One-hundred and seven eyes with glaucomatous optic neuropathy (n = 47 eyes) or which were suspicious for glaucoma (n = 60) were prospectively enrolled in a longitudinal study. Visual fields were evaluated on an annual basis using standard automated perimetry (SAP), the original version of frequency doubling technology (FDT) perimetry, and a custom version of FDT that used the 24-2 stimulus pattern. All SAP fields were within normal limits at the initial visit. When the SAP glaucoma hemifield test was 'outside normal limits' or the pattern standard deviation probability was worse than the lower 5th percentile or more than two clustered locations at the p < 0.05 level were present on the pattern deviation probability plot, an eye was defined as being abnormal. We used a classification tree analysis to predict which eyes would convert, using only baseline test results.

RESULTS

Classification trees that were constructed using only baseline data had excellent specificity (near 100%) but worse sensitivity (25-50%) for predicting which eyes would convert during follow-up.

CONCLUSIONS

Predictive information is present in visual field results, even when they are still within normal limits.

Attentional Gating in Primary Visual Cortex: A Physiological Basis for Dyslexia

The visual magnocellular pathway is known to play a central part in visuospatial attention and in directing attention to specific parts of the visual world in serial search. It is proposed that, in the case of reading, this mechanism is trained to perform a sequential gating of visual information coming into the primary visual cortex to enable further orderly processing by the ventral stream. This scheme, taken together with the potential for plasticity between the different afferent channels in the case of a relative impairment of the magnocellular system, can provide some limited rationale for the beneficial effects that have been claimed for the use of coloured overlays and glasses.

Long-term follow-up in preperimetric open-angle glaucoma: progression rates and associated factors

PURPOSE

To investigate the rate of progressive visual field (VF) loss and associated factors for structural or functional progression in preperimetric open-angle glaucoma (OAG).

DESIGN

Longitudinal, observational study.

METHODS

We included 127 eyes of 127 preperimetric OAG patients who were treated with topical medication and followed for more than 5 years. All patients underwent stereo optic disc photography, red-free retinal nerve fiber layer (RNFL) photography, frequency doubling technology perimetry, and standard automated perimetry (SAP). Progression was defined as a structural (glaucomatous change confirmed by stereo optic disc and red-free RNFL photography) or functional (new glaucomatous defect on SAP) deterioration. The progression rate of SAP mean deviation (dB/year) and factors associated with progression were evaluated.

RESULTS

Glaucoma progression was detected in 72 of 127 eyes (56.7%). Mean rate of VF progression was -0.39 ± 0.64 dB/year in all patients; -0.66 ± 0.60 dB/year in progressors and -0.03 ± 0.24 dB/year in nonprogressors. A multivariate Cox proportional hazard model revealed that optic disc hemorrhage (hazard ratio [HR] = 1.718, P = .031) and the percentage reduction in intraocular pressure (IOP; HR = 0.964, P = .002) were significantly associated with disease progression. Patients with disc hemorrhage had a greater cumulative probability of progression than those without disc hemorrhage (P = .014 by log-rank test).

CONCLUSIONS

Our results support the importance of lowering IOP, even at the preperimetric stage. Preperimetric glaucoma patients with disc hemorrhage and insufficient IOP control should be carefully monitored for greater risk of progression.

Visual electrodiagnosis in glaucoma screening: a clinical study

BACKGROUND

The aim of the present study was to investigate the value of pattern visual-evoked potentials (pVEP) and pattern electroretinograms (pERG) in early glaucoma diagnosis.

MATERIALS AND METHODS

Thirty-eight eyes of 38 patients were included. Patients were classified into normal control (NC) and glaucoma patient (GP) groups. Patients underwent a detailed clinical ophthalmic examination and an electrodiagnostic examination using steady-state pVEP and pERG. Differences between groups in the amplitudes of the second harmonic of the pVEP and pERG responses to 480' (A480) and 48' (A48) check sizes and the ratio of the above amplitudes (A48/A480) were examined.

RESULTS

Differences in the 48' and 480' pVEP between groups were not statistically significant. The pVEP A48/A480 ratio was significantly higher in NC than in GP. Differences in pERG between groups were statistically not significant for both 48' and 480' check sizes. In contrast, respective differences in pERG A48/A480 ratio were statistically significant.

CONCLUSIONS

Steady-state pVEP and pERG A48/A480 ratio may be of value in glaucoma diagnosis.

Measurement of the optic disc vertical tilt angle with spectral-domain optical coherence tomography and influencing factors

PURPOSE

To report a novel method for measuring the vertical tilt angle of the optic nerve (ON) head and to investigate the associated factors.

DESIGN

Cross-sectional diagnostic study.

METHODS

One hundred and twelve normal, glaucomatous, and glaucoma suspect eyes (99 patients) were enrolled in this study. Subjects underwent a full eye examination, biometry, and spectral-domain optical coherence tomography (SDOCT). The vertical tilt angle was measured on high-resolution cross-sectional SDOCT images passing through the ON head and foveal centers using the inner edges of the Bruch membrane opening as the reference plane. The correlation between the vertical tilt angle with the ovality index and the potential associated factors was estimated with univariate and multivariate linear regression analyses.

RESULTS

The median (interquartile range, [IQR]) axial length and visual field mean deviation were 24.5 (23.8-25.3) mm and -0.9 (-2.76 to 0.26) dB. The median (IQR) tilt angle was 3.5 (1.2-11.2) degrees. There was a moderate correlation between the ovality index and tilt angle (Spearman ρ = 0.351; P < .001). In univariate analyses, axial length, spherical equivalent, and mean deviation were correlated with the tilt angle (P = .002, P = .011, and P = .013, respectively). Axial length, mean deviation, and their interaction showed a statistically significant correlation with the tilt angle in multivariate analyses (P = .044 for axial length, P = .039 for mean deviation, and P = .028 for their interaction).

CONCLUSIONS

We describe a new method for measuring the ON head vertical tilt angle with high-resolution SDOCT imaging. The ovality index demonstrated only a moderate correlation with the tilt angle measurements and hence is not a good proxy measure for the vertical ON head tilt angle. Axial length and visual field mean deviation are the main factors associated with the ON head vertical tilt angle. The underlying basis for the relationship of vertical tilt angle and glaucoma severity should be further explored.

Frequency doubling technology, optical coherence technology and pattern electroretinogram in ocular hypertension

BACKGROUND

To assess which of three methods, namely, optical coherence tomography (OCT), pattern electroretinogram (PERG) or frequency-doubling technology (FDT), is the most sensitive and specific for detecting early glaucomatous damage in ocular hypertension (OH).

METHODS

Fifty-two patients with OH (24 men and 28 women, mean age of 56 ± 9.6 years) with an intraocular pressure (IOP) > 21 mm Hg and fifty-two control patients (25 men and 27 women, mean age of 54.8 ± 10.4 years) with IOP < 21 mm Hg, were assessed. All the patients had normal visual acuity, normal optic disk and normal perimetric indices.All subjects underwent OCT, FDT and PERG. Data were analyzed with unpaired t-tests, Chi-square test and Receiver Operating Characteristic (ROC) curve analyses.

RESULTS

In patients with OH, OCT showed retinal nerve fiber layer (RNFL) thinner than in control group in the superior quadrant (130.16 ± 10.02 vs 135.18 ± 9.27 μm, respectively; p < 0.011) and inferior quadrant (120.14 ± 11.0 vs 132.68 ± 8.03 μm; p < 0.001). FDT showed a significantly higher pattern standard deviation (PSD) (3.46  ± 1.48 vs 1.89 ± 0.7 dB; p < 0.001). With respect to PERG, only the amplitude showed significant differences (p < 0.044) between the two groups. ROC curve analysis revealed a sensitivity and specificity of 92% and 86%, respectively, for FDT-PSD (with an area under the ROC curve of 0.940), whereas with OCT, a sensitivity of 82% and a specificity of 74% was recorded in the inferior RNFL quadrant (with an area under the ROC curve of 0.806) finally with PERG amplitude we found a sensitivity of 52% and specificity of 77% (with an area under the ROC curve of 0.595).

CONCLUSIONS

FDT is the most sensitive and specific method for detecting early glaucomatous damage in eyes with OH, and together with OCT, can be useful in identifying those patients who may develop glaucoma.

TRIAL REGISTRATION

ISRCT number: ISRCTN70295497.

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.

Clinical trials in neuroprotection

Neuroprotection is a therapeutic approach that aims to prevent neuronal degeneration and loss of function. Research has focused on developing neuroprotective agents for the therapy of various degenerative diseases, including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and glaucoma. Clinical trials for the evaluation of neuroprotective agents pose unique challenges in terms of experimental design and data interpretation. In order to generate meaningful results, clinical trials on neuroprotective agents should ideally be designed to minimize the potential for bias and optimize the ability to detect the neuroprotective effect of a therapeutic intervention in as short a time as possible. Key issues for the design of clinical trials of neuroprotective therapies include identifying appropriate endpoints and determining the ideal timing of the intervention. Neuroprotection trials in glaucoma must be designed to distinguish between the neuroprotective effects of the therapy and the protective effect of intraocular pressure lowering. The choice of suitable functional endpoints in glaucoma trials is also a critical consideration. For example, visual field loss can be used as a functional endpoint; however, it occurs slowly and may require many years before meaningful changes occur. New methods for assessing visual function may be useful for assessing neuroprotective effects of therapeutic interventions. Although there have been a plethora of medications studied for neuroprotective effects in clinical trials, few have been approved by regulatory agencies for use in patients. Despite these challenges, properly designed clinical trials with validated endpoints will yield the most useful information on the neuroprotective effects of therapy, and may provide new treatment options to prevent the loss of neurologic function, including vision.

Comparison of different analytic algorithms for interpretation of the Swedish interactive threshold algorithm strategy

OBJECTIVE

To compare 4 analytic algorithms for interpretation of the Swedish Interactive Threshold Algorithm.

INTRODUCTION

Analytic algorithms were initially developed for interpretation of standard automated perimetry (using a full threshold strategy). The Swedish interactive threshold algorithm is a novel strategy that was developed to shorten test duration.

METHODS

One hundred forty-three printouts of normal and glaucomatous patients were analyzed using Caprioli's (strict, moderate and liberal) criteria and Anderson's modified criteria for perimetric defect. Areas under the receiver operator characteristics (ROC) curves, sensitivity, and specificity for each criteria were calculated.

RESULTS

Caprioli's strict and Anderson's modified criteria presented similar sensitivity (94.5% and 92.3%, respectively) and specificity (63.5% and 61.5%, respectively). Caprioli's liberal criteria were more sensitive (98.9%) and less specific (42.5%) than the other three criteria.

CONCLUSION

Both Caprioli's and Anderson's modified criteria can be used for interpretation of the Swedish interactive threshold algorithm.

Multifocal objective perimetry compared with Humphrey full-threshold perimetry in patients with optic neuritis

BACKGROUND

The aim of the study is to compare multifocal visual evoked potential (mfVEP) objective perimetry with Humphrey full-threshold visual field (HVF) perimetry, in the assessment of patients with optic neuritis (ON).

METHODS

We assessed 16 patients with clinically diagnosed ON. A comparison was made between the HVF and mfVEP, based on the global severity indices of both tests and number and topography of significant abnormalities detected. The latency data and inter-eye asymmetry findings on the mfVEP were also evaluated.

RESULTS

From a total of 128 quadrants analysed in the 16 patients (100 affected, 28 unaffected eyes), HVF perimetry identified a scotoma in 39/128 (30.5%) quadrants, all of which were in affected eyes; the mfVEP detected a scotoma in 68/128 (53.1%) quadrants using amplitude and/or asymmetry data (XV2=7.2485, P=0.0071). Latency plots on the mfVEP identified a significant latency deviation cluster in 20/25 (80%) affected eyes. Abnormalities were also detected in 4/7 (57%) unaffected eyes. The global severity indices in the affected eyes showed a high correlation between the two tests (r=0.73).

CONCLUSIONS

The mfVEP detected more abnormalities in patients with ON than HVF perimetry. The use of latency recordings as well as combined amplitude and asymmetry plots is advantageous and has the potential to detect abnormalities not otherwise detected on HVF perimetry.

Sensitivity and specificity of frequency-doubling technology, tendency-oriented perimetry, SITA Standard and SITA Fast perimetry in perimetrically inexperienced individuals

PURPOSE

To evaluate the sensitivity and specificity of the screening modes of frequency-doubling technology (FDT), tendency-oriented perimetry (TOP), SITA Standard (SS) and SITA Fast (SF) in perimetrically inexperienced individuals.

METHODS

One eye of 64 glaucoma patients and 53 normal subjects who had never undergone automated perimetry were tested with programs C-20-5 (FDT), G1 (TOP) and 24-2 (SS and SF). The gold standard for glaucoma was the presence of a typical glaucomatous optic disc appearance on stereoscopic examination (judged by a glaucoma expert), and intraocular pressure (IOP) > 21 mmHg. The test order among strategies was randomized for each subject. To define an abnormal visual field, we applied three criteria for SS and SF and two criteria for TOP and FDT, all of which have been previously described in the literature. Sensitivities and specificities among the different criteria were compared using the Cochran test.

RESULTS

Frequency-doubling technology showed the shortest mean test duration, followed by TOP, SF and SS (p < 0.05). Sensitivity ranges were 87.5-89.1% for SS, 92.2-93.8% for SF, 87.5-89.1% for TOP, and 82.8-85.9% for FDT (p = 0.34). Specificity ranges were 73.6-83% for FDT, 56.6-62.3% for TOP, 60.4-69.8% for SF and 66.0-71.7% for SS. The specificity obtained with criterion 2 for FDT (based on the presence of two or more abnormal locations regardless of the severity of abnormal points) was higher than those measured with the other strategies (p < 0.01).

CONCLUSION

When testing individuals with no perimetric experience, moderate sensitivities and specificities should be expected, regardless of the strategy chosen.

Optical coherence tomography, frequency-doubling technology, and colour Doppler imaging in ocular hypertension

PURPOSE

To study in ocular hypertension (OH) the retinal nerve fibre layer (RNFL) with optical coherence tomography (OCT) and the neuronal function with frequency-doubling technology (FDT) to assess which of the two methods was more sensitive in detecting early glaucomatous damage. Furthermore, a colour Doppler imaging (CDI) of the optic nerve was carried out to highlight any correlation with RNFL thickness and FDT abnormality.

MATERIALS AND METHODS

We enrolled 28 ocular hypertensive patients who underwent OCT of the RNFL and FDT. Moreover, we performed a CDI of the ophthalmic artery (OA), central retinal artery (CRA), and posterior ciliary arteries (PCAs).

RESULTS

The patients with OH following OCT revealed a significant thinning in the RNFL as compared to the control group only in the inferior quadrant: 122.250+/-14.091 vs131.750+/-10.729 mum (P<0.045). As regards FDT, there was a significant difference between the two groups only for pattern standard deviation (PSD): 3.873+/-1.488 vs1.938+/-0.704 dB (P<0.044). In OH and in the control group, CDI resistance index (RI) in the OA was 0.768+/-0.012 vs0.745+/-0.019 (P<0.022), in the CRA was 0.66+/-0.012 vs0.645+/-0.019 (P<0.032), and in PCAs was 0.673+/-0.039 vs0.622+/-0.012 (P<0.037). The OCT had a sensitivity of 83% but only in the inferior RNFL quadrant. The FDT-PSD revealed a sensitivity of 85%.

CONCLUSIONS

Both FDT and OCT detect early glaucomatous damage with a slightly superior sensitivity of FDT vsOCT. The CDI measurements suggest that circulatory abnormalities may have a role in the development of OCT and FDT damage.

Humphrey Matrix Frequency Doubling Technology Perimetry and Optical Coherence Tomography Measurement of the Retinal Nerve Fiber Layer Thickness in Both Normal and Ocular Hypertensive Subjects

PURPOSE

The purpose of this study was to determine by means of the Humphrey Matrix frequency doubling technology (FDT) perimetry and the optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurement whether functional and/or structural differences exist between normal and ocular hypertensive (OHT) subjects.

PATIENTS AND METHODS

One eye of 60 consecutive normal individuals and 60 OHT subjects was enrolled in this prospective observational comparative case series study. All subjects were examined at either the Ophthalmology Clinic, University of Chieti-Pescara, Chieti, Italy or the Department of Ophthalmology, S. Maria della Misericordia Hospital, Udine, Italy. All subjects underwent a full ophthalmic examination, including visual acuity, slit-lamp biomicroscopy, central corneal thickness ultrasound pachymetry measurement, achromatic automated perimetry, Matrix FDT perimetry, stereoscopic optic nerve head photography, and OCT. Matrix FDT perimetry mean deviation (MD), pattern standard deviation, glaucoma hemifield test, and 12 OCT RNFL thickness parameters were examined. Student t test, Bonferroni correction for multiple comparisons and receiver operator characteristics curve areas (AUROCs) were used to find any discrimination function between healthy and OHT eyes. Sensitivities at 83% and 92% specificities were reported.

RESULTS

The FDT MD scores ranged from -1.10 to +3.80 decibels (db) in normal individuals and from -4.75 to +3.20 db in OHT subjects. The comparison between the average MD in the 2 groups showed a statistically significant difference (P=0.024). OCT showed a statistically significant difference between the 2 groups when examining the ratio between the inferior and the superior mean RNFL thickness (P=0.004). For OCT, the parameter with the largest AUROC for discriminating between healthy and hypertensive eyes was the ratio between the mean inferior and superior RNFL thickness (AUROC=0.85, sensitivity=75% at specificity=83%, sensitivity=67% at specificity=92%). For Matrix FDT perimetry, the parameter with the largest AUROC was MD (AUROC=0.78, sensitivity=67% at specificity=83%, sensitivity=58% at specificity=92%).

CONCLUSIONS

Our results suggest that OHT eyes having a normal achromatic automated perimetry and a normal clinical disc appearance cannot be differentiated from normal eyes using conventional OCT parameters. When analyzing the ratio between inferior and superior average RNFL thickness, however, a significant difference is evident between healthy and hypertensive eyes. Using Matrix FDT perimetry, a significant difference in MD seems to exist between these 2 groups of eyes. The AUROCs confirm that OCT Iavg/Savg and Matrix FDT MD show the greatest sensitivity and specificity among the examined OCT and Matrix FDT parameters.

Repeatability of Normal Multifocal VEP: Implications for Detecting Progression

PURPOSE

To assess the repeatability of the multifocal visual evoked potential (mfVEP) and to compare it with the repeatability of standard automated perimetry (SAP) in the same group of 50 normal controls retested after 1 year. Our second aim was to assess the repeatability of false alarm rates determined previously for the mfVEP using various cluster criteria.

METHODS

Fifty individuals with normal vision participated in this study (33 females and 17 males). The age range was 26.7 to 77.9 years and the group average age (+/- SD) was 51.4 (+/- 12.1) years. Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS and two 8-minute runs per eye were averaged. The average number of days between the first and second mfVEP tests was 378 (+/- 58). SAP visual fields were obtained within 17.4 (+/- 20.3) days of the mfVEP using the SITA-standard threshold algorithm. Repeatability of mfVEPs and SAP total deviation values were evaluated by calculating point-wise limits of agreement (LOA). Specificity (1-false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied.

RESULTS

Point-wise LOA for the mfVEP signal-to-noise ratio (SNR) ranged from 2.0 to 4.3 dB, with an average of 2.9 dB across all 60 locations. For SAP, LOA ranged from 2.4 to 8.9 dB, with an average of 4.0 dB (excluding the points immediately above and below the blind spot). Clusters of abnormal points were not likely to repeat on either mfVEP or SAP. When an mfVEP abnormality was defined as the repeat presence (confirmation) of a 3-point (P < 0.05) cluster anywhere within a single hemifield, only 1 (of 200) monocular hemifield was deemed abnormal. Although the LOA of the mfVEP were similar throughout the field, the limited dynamic range of SNR at superior field locations will limit the ability to follow progression in "depth" at those locations.

CONCLUSIONS

Repeatability of the mfVEP was slightly better than SAP visual fields in this group of controls with a 1-year retest interval. This suggests that progression in early stages should be more easily detectable by mfVEP. However, in certain field locations (eg, superior periphery), the relatively more narrow dynamic range of the SNR of the mfVEP may limit detection of progression to just 1 event. Confirmation of a 3-point cluster abnormality is highly suggestive of a true defect on the mfVEP.

Detecting glaucoma with frequency-doubling technology perimetry: a comparison between N-30 and C-20 screening programs

PURPOSE

To evaluate the ability of frequency-doubling technology (FDT) perimetry in detecting glaucoma with N-30 and C-20 screening programs.

METHODS

Eighty eyes of 80 patients were enrolled (40 glaucomatous, 40 controls). Humphrey achromatic perimetry (standard automated perimetry, SAP) was considered as the "gold standard" for diagnosis. To assess whether N-30 screening program could detect more initial glaucomatous defects than C-20, glaucomatous patients included 20 cases with nasal step at SAP (pre-selected by medical chart inspection). Patients underwent two SAP examinations to confirm diagnosis; then two N-30 and two C-20 screening tests with frequency-doubling technology were performed in a randomized sequence. Finally, a frequency-doubling technology N-30 full-threshold examination was performed. Several criteria to define abnormality at frequency-doubling technology screening programs were evaluated.

RESULTS

For both C-20 and N-30 screening programs, the best parameter to detect glaucoma was the presence of at least 1 point with P < 5% (sensitivity = 87.5% for both tests and specificity of 90% and 95% for C-20 and N-30, respectively). Both screening procedures obtained a lower sensitivity (75%) in patients with a nasal step, whereas frequency-doubling technology full-threshold program was able to detect the initial defects in all cases.

CONCLUSIONS

N-30 and C-20 screening procedures obtained similar results in well-defined glaucoma patients in terms of sensitivity and specificity. In the presence of a standard automated perimetry nasal step, diagnostic ability with both frequency-doubling technology screening strategies decreased and one quarter of nasal steps went undetected.

Comparison of Diagnostic Ability between a Fast Strategy, Tendency-Oriented Perimetry, and the Standard Bracketing Strategy

PURPOSE

To compare the diagnostic abilities of the standard bracketing strategy (BR) and a fast strategy, the tendency-oriented perimetry (TOP).

METHODS

Seventy-seven controls and 91 eyes from patients with glaucoma were analyzed with the strategies TOP and BR. Sensitivity (Se), specificity (Sp), the area under the receiver operating characteristic (ROC) curve (AC) and the optimum cutoff value (CO) were calculated for the visual field indices mean defect (MD), the square root of the loss variance (sLV) and the number of pathological points (NPP).

RESULTS

In the glaucoma group, the mean MD value using TOP and BR was 7.5 and 8.3 dB, respectively. The mean sLV value using TOP and BR was 5.0 and 5.3 dB, respectively. Indices provided by TOP had higher ROC values than the ones provided by BR. Using TOP, the index with the best diagnostic ability was sLV (Sp = 94.8, Se = 90.1, AC = 0.966, CO = 2.5 dB), followed by NPP and MD. Using BR, the best results were obtained for MD (Sp = 92.2, Se = 81.3, AC = 0.900, CO = 2.5 dB) followed by sLV and NPP.

CONCLUSIONS

A fast strategy, TOP, had superior diagnostic ability than the standard BR. Although TOP provided lower LV values than BR, the diagnostic ability of this index was higher than that of the conventional strategy.

Advances in glaucoma therapeutics

Glaucoma is a major cause of irreversible blindness in the world. The prevalence of glaucomatous loss in vision will continue to grow as our populations age. Ocular hypertension is a major risk factor for the development of glaucoma and current glaucoma therapy is directed at lowering intraocular pressure. Several new ocular hypotensive agents have been introduced in the past several years providing a variety of treatment options. In addition, various classes of neuroprotective agents demonstrating activity in a wide variety of animal models have been proposed as potential new glaucoma therapeutics. Although these approaches will slow the progression of vision loss, they do not directly intervene in the disease process(es). Advances have been made attempting to understand the pathogenic pathways involved in glaucomatous damage to the eye and in methods to clinically measure glaucoma damage. An increased understanding of the pathophysiology of glaucoma will lead to the development of new therapeutic agents that intervene and perhaps even reverse glaucomatous damage to the eye. There also is a need to develop new methods to clinically measure glaucoma damage because, currently, considerable damage occurs before glaucoma is diagnosed and glaucoma remains underdiagnosed in the general population.

Normative ranges and specificity of the multifocal VEP

PURPOSE

To describe a normative database for the multifocal VEP (mfVEP) and to evaluate specificity for a range of cluster criteria.

METHODS

One hundred persons (62 females and 38 males) with normal visual fields and ranging in age from 21.6 to 92.4 years participated in this study. Self-reported race in 80 of these 100 persons was 'White or Caucasian,' eight were 'Black or African-American,' eight were 'Asian,' and four were 'Hispanic or Latino.' Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS and two 8-min runs per eye were averaged. A bootstrap technique was used to estimate the normal range of mfVEP response signal-to-noise ratio (SNR) and inter-ocular amplitude ratio at each location. Specificity (1 - false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied.

RESULTS

There was no overall effect of age on SNR (r2 = 0.16, p = 0.22) nor was the interaction between age and location significant (F = 0.83, p = 0.82, ANOVA). The location with the largest age effect had an r2 of only 0.13. There was a small but significant effect of sex (t = 2.1, p = 0.04) such that SNR was slightly (11%) larger in females than males, but there was no significant interaction between sex and age (t = 0.82, p = 0.41). There was a slight trend toward higher SNR in the Asian group and lower SNR in the African-American group, but the overall effect of race was not significant (F = 1.99, p = 0.12). Specificity depended on the number and probability level of the points defining a cluster. Specificity did not vary by age group in a simple monotonic manner. False positive rates were slightly higher in females than males, and slightly higher in the African-American group as compared with the Asian group.

CONCLUSIONS

Excellent specificity can be achieved for the mfVEP by using particular cluster criteria for monocular and inter-ocular tests. The effects of age, sex, and race were all very small and only the effect of sex was statistically significant. This normative database can be used for analyses of mfVEP results from individual patients with little risk that demographic factors such as age and sex will confound diagnostic accuracy.

Glaucoma studies from 1996 to 1999 in peer-reviewed journals

BACKGROUND

Studies on glaucoma therapy were analyzed with regard to study design, diagnostic parameters and success criteria.

MATERIALS AND METHODS

In 11 frequently read peer-reviewed periodicals, 101 studies published between 1996 and 1999 were chosen according to specific criteria. Design parameters, diagnostic measures and success criteria were investigated.

RESULTS

Thirty-seven studies were retrospective and 64 prospective. Twenty-five studies were multicenter studies. Thirty-seven studies dealt with drug therapy, 12 with laser therapy, and 52 with surgical therapy. The study duration in 51% of the studies (n=52) was up to 1 year, in 28% (n=28) from 1 to 2 years, in 17% (n=17) over 2 years, and in 5% (n=5) in excess of 4 years. Four studies gave insufficient data. Forty-one studies recruited less than 50 patients and 57 studies recruited less than 75 patients. Thirty-four studies included more than 100 patients and 11 studies more than 250 patients. Sixty-one studies included race as a parameter. All 101 studies measured intraocular pressure (IOP). Forty-five studies explicitly described the method of tonometry. Thirteen studies measured a diurnal IOP. Forty-one studies examined the visual field, of which 30 named the method of perimetry. Only 28 studies examined the optic disc morphology. They all employed ophthalmoscopy, and two additionally employed optic disc photography. Sixty-three studies explicitly defined success criteria, establishing 95 different definitions: 74 definitions (78%) used a specified value for IOP as a success criterion. Out of the 70 definitions that gave an absolute value for IOP, 12 definitions (17%) used IOP values between 14 and 16 mmHg as the upper limit, 4 definitions (6%) used IOP values between 17 and 19 mmHg, and 54 definitions (77%) used IOP values between 20 and 22 mmHg. Out of the 26 definitions that specified a percentage IOP reduction, it was judged to be a success when the IOP was lowered by 20% or more from the starting value in ten definitions (38%), by 25% or more in three definitions (12%), and by 30% or more in 13 definitions (50%).

CONCLUSIONS

Examples of prestigious studies show the necessity of observation periods of several years and demonstrate the need for a high number of participants, necessitating the cooperation of many study centers. Beside a more precise characterization of the patient collectives, clinical studies should always specify the measurement method clearly. Investigating a diurnal IOP profile to recognize changes in IOP and IOP peaks, as well as the routine determination of central corneal thickness, would be desirable. New diagnostic techniques for improved assessment of the functional and morphologic damage will gain in relevance in the future. The lack of a common definition of success reveals the complexity of the disease. However, an IOP reduction based on the degree of damage and ascertaining the target pressure seems sensible.

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.

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.