• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.61-66
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• 2010

Purpose: This study was performed to determine vertical fixation disparity by Fixation Disparity Card. The purpose of this study was to investigate distribution of the curve types obtained with Wesson card. Methods: Fixation disparity curves were measured on 52 subjects with the Wesson fixation disparity card. A fixation disparity curve was an x, y coordinate plot of the angular amount of fixation disparity as a function of the power of prisms through which the patient views. The fixation disparity curve variables that were used to aid in the diagnosis and management of binocular vision disorders included the x-intercept, y-intercept, curve slope and curve type. Results: Vertical fixation disparity curves by Wesson Fixation Disparity Card were very various. Conclusions: Vertiical fixation disparity curves could be used to aid in the diagnosis and prescription.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.1
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• pp.53-59
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• 2007

A commonly used device to determine fixation disparity curves is the Wesson Fixation Disparity Card. A fixation disparity curve is an x, y coordinate plot of the angular amount of fixation disparity as a function of the power of prisms through which the patient views. The fixation disparity curve variables that are used to aid in the diagnosis and management of binocular vision disorders include the x-intercept, y-intercept, curve slope and curve type. Fixation disparity curves were measured on 102 subjects with the Wesson fixation disparity card. The purpose of this study is to investigate distribution of the curve types obtained with Wesson card. Fixation Disparity by Wesson Fixation Disparity Card were that in case of type I 63.0%, in case of type II 0.0%, in case of type III 25.0% and in case of type IV 12.0%.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.539-550
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• 2014

Purpose: This research was designed to figure out if there are changes based on types of vergence fixation disparity curve after optical correction and vision training to for people with steep slope of forced vergence fixation disparity curve and symptoms. Methods: For 30 subjects out of 91 subjects, who have steep slopes of fixation disparity curve examined with Wesson Fixation Disparity Card and symptoms about steep slope of fixation disparity curve, proper vision training was offered for 5 weeks. Results: After Vision training for 30 people with the symptoms of type I, II, III, IV for 5 weeks, slope of fixation disparity curve was significantly changed (p=0.013), and the results of binocular vision test and subjective symptoms were also significantly improved. Conclusions: Vision training can not only affect the change of fixation disparity curve, but also relieve the symptoms. Fixation disparity curve has lots of visual function information of the subject and can be suggested as a guideline for prescribing.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.3
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• pp.79-87
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• 2008

Purpose: This study measured Y-intercept that means a fixation disparity, X-intercept that means a associated phoria and slope of a fixation disparity curve (FDC), which are variables of dissociated phoria and the FDC. We searched for the result value and examined the direction, distribution pattern and a variable that give an most affect on dissociated phoria and the FDC at distance and near. Also this study examined that there were statistically significant differences between distance and near, comparing the result value. Methods: We measured the dissociated phoria and the fixation disparity for 51 subjects at distance and near in June, 2007. All subjects ranged from 20 to 25 years of age (average 21.72${\pm}$1.88 years old) and had no eye disease. At distance the dissociated phoria measured with the distance MIM card (muscle imbalance measure card, Bernell co., USA), and the fixation disparity measured with the modified Mallett Far Unit (Bernell co., USA). At near the dissociated phoria measured with the near MIM card (muscle imbalance measure card, Bernell co., USA), and the fixation disparity measured with the Wesson fixation disparity card (American Optical co., USA). Results: The percentage distribution of types of fixation disparity curves was that at distance prevalence of Type I (74.6%) was the highest, followed by Type IV (17.6%) and Type II (3.9%), Type III (3.9%) and that at near prevalence of Type I (53.0%) was the highest, followed by Type III (29.4%), Type IV (13.7%) and Type II (3.9%). 2. There were significantly correlation in dissociated phoria, fixation disparity (Y-intercept) and associated phoria (X-intercept). 3. The fixation disparity at distance was most affected by associated phoria (X-intercept) (p=0.000). The distance dissociated phoria was most affected by fixation disparity (Y-intercept) (p=0.342), but the influence was weak. 4. The fixation disparity at near was most affected by associated phoria (X-intercept) (p=0.000). The near also dissociated phoria was most affected by associated phoria (X-intercept) (p=0.009). The result that compared the each variables with the same variables at distance and near had statistically significant on paired t-test for among dissociated phoria (t=7.529, p=0.000), X-intercept (t=5.860, p=0.000), the Y-intercept (t=4.640, p=0.000) but slope of the FDC did not differ significant (t=1.336 p=0.188). Conclusions: Relationship of fixation disparity and Heterophoria had close correlation at distance and near.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.3
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• pp.321-327
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• 2013

Purpose: To investigate a correlation between vertical fixation disparity and stereopsis by analyzing distribution of types of vertical fixation disparity. Methods: In this study, RANDOT(R) stereotest partly using random dot was used in stereopsis tests. The vertical fixation disparity in close proximity categorized fixation disparity slope into six types on the basis of the result of measurement in when two thin lines, one for one eye looks, become overlapped as a line by adding into prism with Wesson fixation disparity card while maintaining a distance of 25 cm from patients. Results: In the types of near vertical fixation disparity curve, targeting 43 people, the first type 55.82% was the most distributed, the second type is the least 23.25%, the third type of 4.65%, the fourth type of 4.65%, the fifth type of 6.98%, the sixths types of 4.65% were distributed. The result of a correlation analysis, which shows the degree of linear correlation between two variables, represented that stereopsis is not correlated with Y-intercept (r = -0.07) which show vertical fixation disparity, associated phoria (r = -0.03) and dissociated phoria (r = -0.00), but it was not statistically significant (p>0.05). Fixation disparity slope of vertical fixation disparity (r = 0.36) was shown to have a positive correlation with stereopsis. It has a low positive correlation and a meaningful statistics (p<0.05). The Y-intercept which indicates vertical fixation disparity was also not associated with stereopsis (r = -0.07) and dissociated phoria (r = -0.03), and this was not statistically significant (p>0.05), while it had a high correlation as well as a statistically significant with associated phoria (r = 0.89). There was a negative correlation between Y-intercept and fixation disparity slope of vertical fixation disparity (r = -0.33). It showed a low relationship but statistically valuable (p>0.05). As a result of regression analysis, the stereopsis was changed as 7.631" if vertical fixation disparity changes 1' and the vertical fixation disparity changed as 0.017' if stereopsis changes 1', and the change was statistically significant (p<0.05). Conclusions: The study shows that there is a low correlation between stereopsis and vertical fixation disparity, and it is difficult to determine stereopsis only using vertical fixation disparity. Therefore, it suggests other factors above vertical fixation disparity have greater influence on stereopsis.

• Geophysics and Geophysical Exploration
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• v.3 no.4
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• pp.119-124
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• 2000

A new fast algorithm for travel time calculation using mono-chromatic one-way wave equation was developed based on the delta function and the logarithms of the single frequency wavefield in the frequency domain. We found an empirical relation between grid spacing and frequency by trial and error method such that we can minimize travel time error. In comparison with other methods, travel time contours obtained by solving eikonal equation and the wave front edge of the snapshot by the finite difference modeling solution agree with our algorithm. Compared to the other two methods, this algorithm computes travel time of directly transmitted wave. We demonstrated our algorithm on migration so that we obtained good section showing good agreement with original model. our results show that this new algorithm is a faster travel time calculation method of the directly transmitted wave for imaging the subsurface and the transmission tomography.

• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.146-151
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• 2011

A method to evaluate and to reduce the source- and receiver- consistent noise in a cross-well travel time data was proposed. These systematic noises, which can cause some serious effects on the result of a travel time tomography, can be considered as the source and receiver statics. The method evaluates the statics through a curve-fitting of the first arrival travel times in the common source and common receiver gathers. Feasibility study was conducted on a synthetic data which simulates the cross-well travel time tomography to detect a small scale tunnel in a uniform background medium. First arrival travel times at a given source and receiver points are computed by a raytracing method, and the source consistent- and receiver consistent noises are added to the record. In case of the added noise with rms amounting to 25% of the maximum expected anomalous travel time delays, it is confirmed that the method successfully extracted the noise at the 7th step of iteration.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.1
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• pp.19-24
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• 1997

The seismic of the main shock and two after shocks of the Yeongwol Earthquake are studied based on the phase analysis. The travel time curves and two point ray tracing with 12 different possible phases are used to analyze the phases of the records, which were provided by KIGAM seismic network. The results of phase analysis of the Yeongwol Earthquake show the characteristics as follows 1) The main shock ($M_s$=4.5) clearly shows Pn phase but two after shocks ($M_s$=3.8 and $M_s$=2.5) do not show Pn phase. 2) The Pg PmP looks as first arrival phase in the after shock records whose epicentral distance is smaller or larger than 145 km, 3). It is very difficult to identify the phases in the seismic records, which ae related to the Conrad discontinulty, even if the Conrad discontiulty exists. 4) The record of GRE station located outside of the Kyeongsan Basin shows different arrival time of Pn phase, P-S duration time and frequency comared with those of the other stations located within the Kyeongsan Basin.

• Geophysics and Geophysical Exploration
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• v.1 no.1
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• pp.8-18
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• 1998

In exploration seismology, the Kirchhoff hyperbola has been successfully used to migrate reflection seismo-grams. The mathematical basis of Kirchhoff hyperbola has not been clearly defined and understood for the application of prestack or poststack migration. The travel time from the scatterer in the subsurface to the receivers (exploding reflector model) on the surface can be a kinematic approximation of Green's function when the source is excited at position of the scatterer. If we add the travel time from the source to the scatterer in the subsurface to the travel time of exploding reflector model, we can view this travel time as a kinematic approximation of the partial derivative wavefield with respect to the velocity or the density in the subsurface. The summation of reflection seismogram along the Kirchhoff hyperbola can be evaluated as an inner product between the partial derivative wavefield and the field reflection seismogram. In addition to this kinematic interpretation of Kirchhoff hyperbola, when we extend this concept to shallow refraction seismic data, the stacking of refraction data along the straight line can be interpreted as a measurement of an inner product between the first arrival waveform of the partial derivative wavefield and the field refraction data. We evaluated the Kirchhoff hyperbola and the straight line for stacking the refraction data in terms of the first arrival waveform of the partial derivative wavefield with respect to the velocity or the density in the subsurface. This evaluation provides a firm and solid basis for the conventional Kirchhoff migration and the straight line stacking of the refraction data.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.327-335
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• 2006

Three processing strategies of seismic refraction data are tested in terms of velocity and depth profiles or structures for mapping of geological discontinuities: GRM(generalized reciprocal method), GLI(generalized linear inversion), Tomography. The test data used in this study are the shot gathers reconstructed by numerical modeling for the structures of 3 planar layers(horizontal, inclined), the buried vertical fracture zones, and vertical fault zones. Tomography is shown to be very efficient for mapping of more complicated tone such as vertical fault and buried fracture zones, whereas GRM and GLI can be useful for horizontal and/or inclined layers, probably on their bases of analysis of first arrivals in travel time curves.