Evaluation of hemifield sector analysis protocol in multifocal visual evoked potential objective perimetry for the diagnosis and early detection of glaucomatous field defects

CONCLUSIONS: The new HSA protocol used in the mfVEP testing can be applied to detect glaucomatous visual field defects in both glaucoma and glaucoma suspect patients. Using this protocol can provide information about focal visual field differences across the horizontal midline, which can be utilized to differentiate between glaucoma and normal subjects. Sensitivity and specificity of the mfVEP test showed very promising results and correlated with other anatomical changes in glaucoma field loss. PURPOSE: Multifocal visual evoked potential (mfVEP) is a newly introduced method used for objective visual field assessment. Several analysis protocols have been tested to identify early visual field losses in glaucoma patients using the mfVEP technique, some were successful in detection of field defects, which were comparable to the standard automated perimetry (SAP) visual field assessment, and others were not very informative and needed more adjustment and research work. In this study we implemented a novel analysis approach and evaluated its validity and whether it could be used effectively for early detection of visual field defects in glaucoma. METHODS: Three groups were tested in this study; normal controls (38 eyes), glaucoma patients (36 eyes) and glaucoma suspect patients (38 eyes). All subjects had a two standard Humphrey field analyzer (HFA) test 24-2 and a single mfVEP test undertaken in one session. Analysis of the mfVEP results was done using the new analysis protocol; the hemifield sector analysis (HSA) protocol. Analysis of the HFA was done using the standard grading system. RESULTS: Analysis of mfVEP results showed that there was a statistically significant difference between the three groups in the mean signal to noise ratio (ANOVA test, p < 0.001 with a 95% confidence interval). The difference between superior and inferior hemispheres in all subjects were statistically significant in the glaucoma patient group in all 11 sectors (t-test, p < 0.001), partially significant in 5 / 11 (t-test, p < 0.01), and no statistical difference in most sectors of the normal group (1 / 11 sectors was significant, t-test, p < 0.9). Sensitivity and specificity of the HSA protocol in detecting glaucoma was 97% and 86%, respectively, and for glaucoma suspect patients the values were 89% and 79%, respectively

Two Essays on Monetary Policy and Exchange Rates in Thailand

This dissertation presents two essays on monetary policy determination and exchange rate forecasting in Thailand. Thailand is a small open economy using an inflation-targeting framework with a managed floating exchange rate. The Bank of Thailand uses the policy interest rate as the main monetary policy instrument and intervenes in the exchange rate market only when necessary to prevent excess volatility and to achieve economic policy goals. Both interest rates and exchange rates shape the economic decisions of households and firms and thus play an important role in economic conditions and stability. Therefore, it is crucial to understand the determinants and dynamics of these variables. The first paper investigates the Bank of Thailand's interest rate determination using the Taylor rule, which posits that the optimal interest rate is a function of inflation and the output gap. Because Thailand is a small open economy highly exposed to international trade and capital flows, I also include international factors (the federal funds rate and exchange rates) in the Taylor equations. I find that the Bank of Thailand significantly responds to expected inflation, which is consistent with an inflation-targeting framework, while the output gap does not play an important role in the monetary policy reaction function. I also find that the Bank of Thailand significantly responds to international factors, in particular adjusting the interest rate in the same direction as the federal funds rate and reacting to exchange rate movements. The second paper evaluates out-of-sample exchange rate forecasting for the Thai baht vis-a-vis the U.S. dollar (USDTHB) using fundamental models from the literature such as the purchasing power parity model, the uncovered interest rate parity model, the monetary model, and the Taylor rule fundamental model at different forecast horizons and using various rolling window sizes. Using the Diebold-Mariano/West test, I find that the Taylor rule with inertia and asymmetric coefficients model and the monetary model with sticky prices have the strongest ability of the fundamental models to predict exchange rate movements. This Taylor rule model outperforms the random walk starting at the six-month forecast horizon, while this monetary model outperforms the random walk starting at the one-year forecast horizon. Then, I construct a hybrid model combining variables from these two top-performing models; pairwise comparison determines that this hybrid model outperforms both models individually. Additionally, I find that the exchange rate predictability of all models tends to improve as the forecast horizon increases, with the highest rejection against the random walk at the three-year forecast horizon while there is no significant evidence of short-run predictability. Overall, I find that Thailand's monetary policy is best described by the Taylor rule, under which the Bank of Thailand strictly targets inflation in accordance with its economic goals. Additionally, the Bank of Thailand responds to changes in exchange rates and the federal funds rate. Therefore, based on this augmented Taylor rule, the nominal exchange rate can be forecasted using the Taylor rule with inertia and asymmetric coefficients model. However, exchange rate predictability is only found at the six-month horizon and beyond. I also find that by incorporating useful information from various macroeconomic variables, the hybrid model has the strongest predictive performance of all models.Economics, Department o

Multifocal VEP and OCT findings in patients with primary open angle glaucoma: A cross-sectional study

<p>Abstract</p> <p>Bakground</p> <p>To evaluate objectively the anatomical and functional changes of optic nerve in eyes with primary open angle glaucoma (POAG) by the joint use of optical coherence tomography (OCT) and multifocal visual evoked potentials (mfVEP).</p> <p>Methods</p> <p>29 eyes with open angle glaucoma and visual field defects, as well as 20 eyes of 10 age-matched control normal subjects were tested. All participants underwent a complete ophthalmological examination. Moreover, Humphrey visual field test, OCT examination and recording of mfVEP were performed. Amplitude and implicit time of mfVEP, as well as RNFL thickness were measured. Differences in density components of mfVEP and in RNFL thickness among POAG eyes and control eyes were examined using Student’s t-test.</p> <p>Results</p> <p>In glaucomatous eyes the mean Retinal Response Density (RRD) was lower than normal in ring 1, 2 and 3 of mfVEP (p < 0.0001). Specifically the mean amplitude of mfVEP in POAG eyes was estimated at 34.2 ± 17.6 nV/deg², 6.9 ± 4.8 nV/deg² and 2.6 ± 1.6 nV/deg² in rings 1, 2 and 3 respectively. In contrast the mean implicit time was similar to control eyes. In addition, the mean RNFL thickness in POAG eyes was estimated at 76.8 ± 26.6 μm in the superior area, 52.1 ± 16.3 μm in the temporal area, 75.9 ± 32.5 μm in the inferior area and 58.6 ± 19.4 μm in the nasal area. There was a statistically significant difference in RNFL thickness in all peripapillary areas (p < 0.0001) between POAG eyes and controls, with superior and inferior area to present the highest decrease.</p> <p>Conclusions</p> <p>Our study shows that, although Standard Automatic Perimetry is the gold standard to evaluate glaucomatous neuropathy, the joint use of mfVEP and OCT could be useful in better monitoring glaucoma progression.</p