• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.93-104
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• 2004

In order to have a comfortable vision without any asthenopia in work place, it is very necessary to make a complete binocular correction in addition to the perfect correction of refractive deficits. For this, At first, the exact understanding of the required corrective value of the existing angular ametropia(associated phoria) is needed. The fact likely seems fact that a correction of refractive deficits could not to be reached with single optotype, the corrections of angular ametropia(associated phoria) with single optotype is impossible. The reason is that a most ametropia(associated phoria) is accompanied with the fixation disparity. To make a perfect measurement of ametropia(associated phoria), at least, 3 kinds of optotype is essential. This fact could be explained by stating the fusional stimulus in the binocular refraction tests on each eye. If these types of three tests have not practical practice. The most of many cases may result in undercorrection.

• 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 Convergence for Information Technology
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• v.8 no.6
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• pp.101-106
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• 2018

We examined refractive error, the corrected visual acuity, phoria and fusional reserve of 114 healthy myopes and hyperopia who had no strabismus, no ocular and physical diseases. We evaluated the occurrence of asthenopia according to phoria and fusional reserve. 41 out of 114 subjects which exophoria was 69% and esophoria was 5.5%, orthophoria was 26% made a complaint against asthenopia. The subjects who had exophoria of $0-6{\Delta}$ in the range of normal state was 61.4%, while the subjects who had exophoria of $7{\Delta}$ or more in the range of abnormal state was 38.6%. Reducing fusional reserve was associated with increasing phoria. The fusional reserve twice or more than phoria were 27.2%, and twice or under were 72.8%. Futhermore, AC/A ratio for heterophoria was found from 1.0 to 12.6 and its relationship to asthenopia of phoria could not be determined.

• 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.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.229-235
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• 2015

Purpose: This study was undertaken to study on visual function before and after prescription of vertical prism. Methods: 80 subjects (10-30ages) who had been precribed vertical prism and 1 year after they were represcribed vertical prism. Results: Phoria (p=0.000), supra vergence (p=0.000), NPC (p=0.003), NPA (right eye) (p=0.005), NPA(left eye) (p=0.000) showed a significant change. Conclusion: Vertical prism prescription was reduced during revisit. Supra vergence, NPC, NPA(right eye), NPA(left eye) showed a significant change. Binocular Accommodative lag was not associated with vertical prism prescription and binocular vision findings.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.3
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• pp.235-242
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• 2016

Purpose: This study was to investigate whether the application of different diagnostic criteria affected the frequency of convergence insufficiency (CI). Methods: Eighty one subjects with mean age of 22.54 years (20 to 27 years) were evaluated. Binocularity tests after refraction were performed as the following tests: near point of convergence (NPC) with an accommodative target, phoria using von Graefe method, positive fusional vergence (PFV) with a phoropter. Subjects with CI were diagnosed when exophoria (exo) was greater at near than at distance ($exo{\geq}4{\Delta}$, or >$6{\Delta}$), fusional vergence was $PFV{\leq}11{\Delta}$ for blur, $PFV{\leq}15{\Delta}$ for break, Sheard's or Percival's criterion, and NPC was $NPC{\geq}6cm$, ${\geq}7.5cm$ or >10 cm. Results: Frequency of CI with one diagnostic criterion was ranged from 6.2% to 77.8%, and was overestimated or underestimated according to criteria. It was reduced to the range of 6.2% to 43.2% with diagnostic criteria more than two, especially to the range of 24.7% to 28.4% with lower variability in diagnostic criteria including phoria and Sheard's criterion. There were high relationship between total score of signs and phoria score (r = 0.772, p<0.001), and measured phoria and Sheard's criterion (r = -0.654, p<0.001), but NPC had a high variability and a weak or no significant relationship with other diagnostic criteria. Results suggested $exo{\geq}4{\Delta}$, Sheard's criterion and $NPC{\geq}7.5cm$ for diagnostic criteria of signs and sequence for CI. Conclusions: Frequency of CI is likely to be over- and underestimated with diagnostic criteria. Cutoff values and procedures for phoria, Sheard's criterion and NPC as clinical signs should be suggested definitely in diagnosis associated with CI.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.2
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• pp.171-177
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• 2011

Purpose: The purpose of this study was to investigate the relationships between reading ability and binocular functions, based on self tests through surveys. The possibility of the reading ability tests used in this study as a tool on the determination about vision efficiency was also evaluated. Methods: Through reading ability tests about 138 university students, 72 students (52.2%) of them were first selected. Through self tests about dyslexia and light sensitivity, 38 students (52.7%) of the first selected students were secondly selected, whose extents are more than 3. Binocular tests were carried out about three groups (high, middle, low) of these secondly selected students. Tests about NPCs, distance and near phoria, amplitude of accommodation, fusional vergence, AC/A ratio, accommodative facility, and vergence facility were performed as binocular tests. Results: NPCs were closest to eyes at high groups. Fusional vergence, AC/A ratio, accommodative facility, and vergence facility of high group showed higher than other groups. The phoria at middle group showed higher than other groups. Conclusions: We found that reading ability and some of binocular functions were closely related. Therefore, vision training, associated with insufficiencies of binocular functions, is expected to improve reading ability.

• 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.20 no.3
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• pp.333-339
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• 2015

Purpose: The aim of this study was to evaluate clinical characteristics of subjective accommodative lags determined by fused cross-cylinder (subjective method), and an open-field autorefractor (objective method) under uncorrected and corrected conditions. Methods: Thirty three healthy subjects (26 males and 7 females aged $23.73{\pm}1.35$ years from 22 to 27 years) participated. Four methods were used to determine accommodative lag: (1) a subjective method with the fused cross-cylinder (FCC) under +2.00 D fogging lenses condition, (2) an objective method with the autorefractor under uncorrected condition (3) a corrected method (effective accommodative lag) using equations presented by Gwiazda et al. in objective methods, and (4) a corrected method using equations presented by Mutti et al. in objective methods. Results: The mean accommodative lags were 0.72 D for subjective method, 0.82 D for uncorrected objective method, 0.88 D for corrected method with Gwiazda's equations, and 0.78 D for corrected method with Mutti's equations. There were significant differences between the objective accommodative lags, but no significant differences between the objective and subjective accommodative lags. The effective accommodative lags showed significant correlations between phorias and refractive errors. The effective accommodative lag by Mutti's equations had a high correlation with uncorrected accommodative lags (r=0.99, p<0.001). Conclusions: The objective accommodative lag correlated with phorias and refractive errors. Especially, The effective accommodative lag using Mutti's equations may be considered for clinical availability and qualitative evaluation associated with symptoms.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.661-666
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• 2013

The aim of this study was to evaluate the property of heterophoria and fusional reserve in Adults in Jeon-buk Area. We examined the corrected visual acuity, corrected refractive error, heterophoria and fusional reserve of 116 healthy myopes aged from 20 to 44 old who had no strabismus no ocular and phyisical diseases. Using Von Graefe test of horizontal heterophoria Measurement, we measured orthophoria(26.7%), exophoria(52.5%) and esophoria(20.7%) for at near distance. The subjects who had exophoria of 0-6${\Delta}$ in the range of normal state was 38.8%, while the subjects who had exophoria in the range of abnormal state was 61.2%. Reducing fusional reserve was associated with increasing phoria. We found a relationship between asthenopia and fusional reserve of heterophoria and considered that fusional reserve must be examined when we preserve for a patient with heterophoria. Furthermore, Gradient method AC/A ratio was found 4.03 and its relationship to refractive error could not be determined.