Base-in Research Articles

Effect of Vergence Facility Testing on Horizontal Fusional Reserves.

The effect of vergence adaptation on test sequences should be considered in clinical practice. This study aimed to compare the effect of vergence adaptation after different vergence facility (VF) testing methods on following horizontal fusional reserve measurement at near. This cross-sectional study was performed on 50 healthy subjects with a mean ± standard deviation age of 21.18 ± 1.41 years. The baseline horizontal fusional reserves were measured using base-in (BI) and base-out (BO) prisms (∆) at near. Then, VF was measured using 3∆BI/12∆BI flip prism at near, and then the measurement of fusional reserves was repeated. In the next step, fusional reserves were measured after VF testing using 8∆BI/8∆BO flip prism. The values of fusional reserves were compared with their baseline findings. The results of negative fusional reserves after VF measurement using the 3∆BI/12∆BO prisms were significantly lower than the baseline values (blur [P = .03], break [P = .03], and recovery [P = .03]). There were no significant differences between the values of fusional reserves before and after VF testing using the 8∆BI/8∆BO prisms (P > .05). No correlation was observed between fusional reserves and VF responses (P > .05); however, the results revealed a positive correlation between the values of fusional reserves before and after VF testing using both methods (all P < .05). There was no significant difference in VF findings between the methods (P = .23). The measurements of horizontal fusional reserves followed by VF testing were not affected except for the responses of negative fusional reserves, which decreased after VF determination using the 3∆BI/12∆BO method. Although the vergence adaptation does not seem clinically significant, it is recommended to evaluate horizontal fusional reserves before VF measurement or long-enough time after VF testing for the vergence system to return to its nonadapted state.

Effect of Induced Vertical Disparity on Horizontal Fusional Reserves

ABSTRACTPurpose: The aim of this study was to investigate the effects of induced vertical disparity on horizontal fusional reserves at near. Materials and Methods: In 170 healthy subjects wearing best corrective refraction, the negative and positive horizontal fusional reserves were measured with base-in (BI) and base-out (BO) prisms, respectively, in the presence of 0.5 prism diopters (∆) and 1∆ vertical prisms placed in trial frames in front of the right eye. The prism power was slowly increased step by step until the subject reported sustained blur, break, and recovery. These were compared to horizontal fusional reserves in the same subjects without a vertical prism. Data were analyzed in SPSS.17 software using a repeated measures ANOVA. Results: Induced vertical disparity decreased negative fusional reserves (NFR) horizontally and was more significant with 1∆ vertical disparity (P<0.001). There were significant differences between the blur (P<0.001), break (P<0.001), and recovery (P<0.001) for NFR before and after induced vertical disparity and no significant difference between blur (P=0.173) and recovery points (P=0.261) with a marginal difference for break points (P=0.045) for the positive fusional reserves (PFR). Conclusion: Inducing vertical disparity even with small magnitudes affects all 3 aspects (blur, break, and recovery) of horizontal negative fusional reserves while only break is affected in positive fusional reserves. These changes are statistically significant but do not seem to be clinically significant except for cases accompanied by symptoms.

Dynamic Magnetic Resonance Imaging- a sensitive tool in managing consecutive exotropia.

Proper evaluation and accurate diagnosis are crucial in managing a case of strabismus. Report a case of prolonged large angle complicated consecutive exotropia where dynamic Magnetic Resonance Imaging helped us to diagnose and simplify the management plan. A 19-year-old male presented with outward deviation of both eyes for last 16 years with right face turn, without diplopia and trauma. However, he had history of two consecutive squint surgeries, a month apart, at the age of 3 years. Visual acuity (best corrected) in the right and left eye was 6/36 and 6/6 respectively. Extraocular movements revealed minus (-) 4 adduction deficits in the left eye with right eye suppression. Prism Alternate Cover Test (PACT) showed 65 prism diopter (PD) base in (BI), for primary and near gazes with lateral incommitance and without any pattern. Forced Duction Test (FDT) showed restriction of the left lateral rectus. Dynamic Magnetic Resonance Imaging revealed posterior insertion of the left medial rectus with thinning of the tendinous insertion of the left lateral and medial rectus in neutral position. On adduction of left eye, there was slight increased bulk of the left medial rectus. Medial Rectus (MR) advancement 5.5 mm and Lateral Rectus (LR) recession 9mm was done. Repeat FDT showed improvement in resistance. After 3 month, the patient had excellent outcome with 5 PD primary position exotropia and 2 units of improvement in left eye adduction. Precise workup and appropriate investigation decreases the undue interventions with excellent outcome in a case of large angle consecutive XT. Keywords Consecutive exotropia; dynamic MRI; esotropia; medial rectus advancement; slipped muscle.

Objective Measurement of Fusional Vergence Ranges and Heterophoria in Infants and Preschool Children

PurposeBinocular alignment typically includes motor fusion compensating for heterophoria. This study evaluated heterophoria and then accommodation and vergence responses during measurement of fusional ranges in infants and preschoolers.MethodsPurkinje image eye tracking and eccentric photorefraction (MCS PowerRefractor) were used to record the eye alignment and accommodation of uncorrected infants (n = 17; 3–5 months old), preschoolers (n = 19; 2.5–5 years), and naïve functionally emmetropic adults (n = 14; 20–32 years; spherical equivalent [SE], +1 to −1 diopters [D]). Heterophoria was derived from the difference between monocular and binocular alignments while participants viewed naturalistic images at 80 cm. The presence or absence of fusion was then assessed after base-in (BI) and base-out (BO) prisms (2–40 prism diopters [pd]) were introduced.ResultsMean (±SD) SE refractions were hyperopic in infants (+2.4 ± 1.2 D) and preschoolers (+1.1 ± 0.6 D). The average exophoria was similar (P = 0.11) across groups (Infants, −0.79 ± 2.5 pd; Preschool, −2.43 ± 2.0 pd; Adults, −1.0 ± 2.7 pd). Mean fusional vergence range also was similar (P = 0.1) for BI (Infants, 11.2 ± 2.5 pd; Preschool, 8.8 ± 2.8 pd; Adults, 11.8 ± 5.2 pd) and BO (Infants, 14 ± 6.6 pd; Preschool, 15.3 ± 8.3 pd; Adults, 20 ± 9.2 pd). Maximum change in accommodation to the highest fusible prism was positive (increased accommodation) for BO (Infants, 1.69 ± 1.4 D; Preschool, 1.35 ± 1.6 D; Adults, 1.22 ± 1.0 D) and negative for BI (Infants, −0.96 ± 1.0 D; Preschool, −0.78 ± 0.6 D; Adults, −0.62 ± 0.3 D), with a similar magnitude across groups (BO, P = 0.6; BI, P = 0.4).ConclusionsDespite typical uncorrected hyperopia, infants and preschoolers exhibited small exophorias at 80 cm, similar to adults. All participants demonstrated substantial fusional ranges, providing evidence that even 3- to 5-month-old infants can respond to a large range of image disparities.

Von Graefe법의 프리즘 세팅에 따른 사위검사의 비교

Purpose: The aim of this study was to compare the differences among prism settings of the von Graefe technique for phoria measurement. Methods: Thirty eight healthy subjects (mean age ) were tested with eye examination by interview, cover test, and refraction. Phorias were measured in a random order using four prism settings for the von Graefe method: base-in (BI) and base-up (BU), BI and base-down (BD), BU and BI, and BD and BI over the right and left eye, respectively. Results: Among the four prism settings in measurements of lateral and vertical phoria, there were not significant differences at distance, whereas there were significant at near. The reliability of near lateral phoria (ICC: 0.95) was good, but that of near vertical phoria was less reliable (ICC: 0.83). In comparisons of the paired t-test, the 95% limits of agreement, and mean difference between prism settings, BU had more useful than other prism settings at near phoria. Conclusions: Results from this study suggest that the von Graefe test with BU or BU including other setting prisms have useful methods, especially for near phoria measurements.

Convergence Accommodation to Convergence CA/C Ratio: Convergence Versus Divergence

Aim: To determine whether the convergence accommodation to convergence (CA/C) ratio during divergence with base-in (BI) prisms is of a similar or different magnitude to that measured during convergence with base-out (BO) prisms.Methods: Eighteen participants with normal binocular single vision were recruited. The participants viewed a pseudo-Gaussian target, which consisted of a light emitting diode (LED) behind a diffusing screen at 40 cm. After 5 minutes of dark adaptation, the refractive status of the eye was measured without any prism using a Shin-Nippon SRW-5000 autorefractor. The participant held the selected prism (5Δ or 10Δ BO or BI, counterbalanced) in front of their right eye and obtained a single, fused image of the target while refractive measures were taken with each. A 30-second rest period was given between measurements. The mean age of the participants was 20.6 ± 3.22 years.Results: The mean CA/C ratios for the 5Δ BO, 10Δ BO, 5Δ BI, and 10Δ BI were 0.108 (±0.074) D/Δ, 0.110 (±0.056) D/Δ, 0.100 (±0.090) D/Δ, and 0.089 (±0.055) D/Δ, respectively. A 2-factor repeated measures ANOVA found that the CA/C ratio did not significantly change with differing levels of prism-induced convergence and divergence (p = 0.649).Conclusions: Change in accommodation induced by manipulating vergence is similar whether convergence or divergence are induced. The CA/C ratio did not show any change with differing levels of prism-induced convergence and divergence.

Stereoacuity as an Indicator of Prism Adaptation

Purpose: The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation.Materials and Methods: Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively. Prism vergences were measured using a prism bar. For each participant, prism power equivalent to the blur point of base-in (BI) and base-out (BO) fusional vergence at 40 cm was divided and placed in front of both eyes. At 0, 3, 6, 9 and 12 min after prism introduction, the stereoacuity was measured, and at 0 and 12 min, the heterophoria was measured.Results: The repeated measures ANOVA showed a significant difference between the mean stereoacuity for BI and BO prisms at the different measurement times (p < 0.05). For BO prism, the initial value was different between 0 and 3 min after the prism introduction, whereas for BI prism, a difference in stereoacuity was found between the pre-prism value and the value at 0, 3 and 6 min. The size of the heterophoria with BO and BI prisms was different from 0 to 12 min (p < 0.05).Conclusion: The time required for stereoacuity to return to baseline level was more than 3 min for BO, and more than 6 min for BI prism. In addition, the time required to return to baseline values was not similar for the stereoacuity and heterophoria. The recovery of stereoacuity is slower when adapting to divergence, as when looking from near to far. This implies that stereopsis responds faster to near targets than to distant one, and may precede complete phoria adaptation.

Ten-Year Changes in Fusional Vergence, Phoria, and Nearpoint of Convergence in Myopic Children

To identify longitudinal changes in fusional vergence ranges and their relationship to other clinical measures in young myopic subjects. Measurements were collected annually for 10 years on 114 subjects from the University of Houston Correction of Myopia Evaluation Trial cohort. Subject age was 7 to 13 years at year 1 of follow-up. Measurements included refractive error, distance and near phoria, interpupillary distance (IPD), prism bar fusional vergence ranges, and nearpoint of convergence (NPC). Multilevel modeling was used to determine baseline and rate of change for fusional vergence ranges and the impact of phoria, IPD, and NPC on these measures. Year 1 mean distance base-out (BO) break was 20 prism diopters (pd) and decreased 5.6 pd over 10 years (p < 0.001). Mean near BO break was 30 pd at year 1 and decreased 9.4 pd over 10 years (p < 0.001). Greater esophoria was significantly related to greater BO break (p < 0.02) and receded NPC was significantly related to lower magnitude BO break at near (p < 0.001). Distance IPD increased 3 mm over 10 years (p < 0.001) but was unrelated to the magnitude of the BO ranges (p > 0.2). Mean distance base-in (BI) break was 7 pd at year 1 and increased 0.5 pd in 10 years (p = 0.04). Mean near BI break was 13 pd at year 1 and did not significantly change. Mean distance phoria was 0.1 pd exophoria at year 1 and did not change, whereas near phoria was 2.4 pd esophoria at year 1 and became more exophoric (4 pd in 10 years, p < 0.001). These results suggest that for myopic children convergence ranges decrease for both distance and near viewing during the school years as near phoria becomes more exophoric. These findings could have clinical implications given that compensating convergence ranges decrease as near phoria becomes more divergent.

Comparison of Fixation Disparity Measured by Saladin Card and Disparometer

The purpose of this study was to compare the fixation disparity (FD) measurements taken with the Saladin Near Point Balance Card (Saladin card) to those made with the Sheedy Disparometer, and to determine if the same clinical norms used with the Disparometer can be applied to the newer Saladin card. Subjects were 44 optometry students (aged 23 to 34 years) without strabismus, amblyopia, or asthenopia during near work. They were randomized to begin at one of three examiners' stations: dissociated near phoria using Modified Thorington card; FD with Saladin card; and FD with Disparometer. Subjects proceeded to each station in turn. FD was measured for each subject through forced vergence demands of 0, 3, 6, and 9 base-in (BI), and 3, 6, 9, 16, and 20 base-out (BO), alternating BI and BO demands. Examiners were masked to subjects' results from the other stations. FD curve (FDC) types were the same with the two instruments in most cases. However, statistically significant differences were found for FDC slopes (p = 0.048), y intercepts (p < 0.0001), and FD values through BI prisms (p < 0.0001), with the Disparometer finding the FD to be more eso/less exo than did the Saladin card. FD values through BO prisms showed no statistically significant differences but great variability. The two instruments generally produce similar types of FDCs. However, the Disparometer tends to yield more eso/less exo FD measurements compared with the Saladin card. Although the newer Saladin card frequently produces FDC slopes and y intercepts within the expected range (as published for the Disparometer) for asymptomatic subjects, slopes and y intercepts obtained by the Saladin card are not sufficiently similar to those obtained by the Disparometer to warrant use of the same norms. Further study is needed to establish appropriate norms for the Saladin card.

Accommodation and convergence during sustained computer work

Purpose With computer usage becoming almost universal in contemporary society, the reported prevalence of computer vision syndrome (CVS) is extremely high. However, the precise physiological mechanisms underlying CVS remain unclear. Although abnormal accommodation and vergence responses have been cited as being responsible for the symptoms produced, there is little objective evidence to support this claim. Accordingly, this study measured both of these oculomotor parameters during a sustained period of computer use. Methods Subjects (N = 20) were required to read text aloud from a laptop computer at a viewing distance of 50 cm for a sustained 30-minute period through their habitual refractive correction. At 2-minute intervals, the accommodative response (AR) to the computer screen was measured objectively using a Grand Seiko WAM 5500 optometer (Grand Seiko, Hiroshima, Japan). Additionally, the vergence response was assessed by measuring the associated phoria (AP), i.e., prism to eliminate fixation disparity, using a customized fixation disparity target that appeared on the computer screen. Subjects were asked to rate the degree of difficulty of the reading task on a scale from 1 to 10. Results Mean accommodation and AP values during the task were 1.07 diopters and 0.74∆ base-in (BI), respectively. The mean discomfort score was 4.9. No significant changes in accommodation or vergence were observed during the course of the 30-minute test period. There was no significant difference in the AR as a function of subjective difficulty. However, the mean AP for the subjects who reported the least and greatest discomfort during the task was 1.55∆ BI and 0, respectively ( P = 0.02). Conclusions CVS, after 30 minutes was worse in subjects exhibiting zero fixation disparity when compared with those subjects having a BI AP but does not appear to be related to differences in accommodation. A slightly reduced vergence response increases subject comfort during the task.

Comparison of near fusional vergence ranges with rotary prisms and with prism bars

Background Common methods for determination of fusional vergence ranges make use of rotary prisms in the phoropter or prism bars out of the phoropter. This study compared near fusional vergence ranges with rotary prisms with those with prism bars. Methods Fifty young adults served as subjects. Odd-numbered subjects had rotary prism vergences performed before prism bar vergences. For even-numbered subjects, prism bar vergences were done first. Base-in (BI) vergences were done before base-out (BO) vergences with both rotary prisms and prism bars. A coefficient of agreement was calculated by multiplying the standard deviation of the individual subject differences between rotary prisms and prism bars by 1.96, to approximate the range within which the 2 tests would agree 95% of the time. Results The lowest coefficient of agreement was 7.3Δ for the BI recovery. The others were high, ranging from 15.4Δ for the BO recovery to 19.5Δ for the BO break. Conclusion Fusional vergence ranges determined by prism bars out of the phoropter cannot be used interchangeably with those determined by phoropter rotary prisms for the purpose of follow-up on individual patients or for the purpose of comparison with norms.

Cubing the Kyoto Protocol: Post-Copenhagen Regulatory Reforms to Reset the Global Thermostat

ABSTRACT: The Copenhagen Conference of the Parties (COP-15), which took place in December 2009, was intended to set in stone an ambitious global climate change agreement for the post-2012 period, when the Kyoto Protocol expires. It did not succeed, resulting only in a 13-paragraph political accord which was not agreed to, but only noted because of lack of consensus. The COP-16 in December 2010 in Cancun, Mexico, met a similar, if less contentious, inconclusive end. Every fundamental issue was left unresolved at both disappointing critical Conferences. Left unreformed as an international legal regulatory mechanism, the Kyoto Protocol has no chance of success, and terminates by its own terms in 2012. A new legal architecture must address issues of participation, global warming chemical emissions, the failure in both participating developed nations and developing nations to shift power generation bases to sustainable low-carbon alternatives, misuse of carbon offsets, and lack of effective enforcement. This article proposes a four-sided approach towards a new international legal architecture. I describe these approaches in the following dimensions, and propose to create a model of governance that will put into place the ideals of the Kyoto Protocol. Dimension 1: The legal line covering international stakeholders must be altered to include transitional developing countries. Policies must speak a new language of carbon control through adding forestation preservation protocols and including regulation of the most harmful global warming chemicals in developing countries. Dimension 2: There is no Kyoto Protocol legal requirement whatsoever that developed economies make any shift to zero-carbon renewable power resources. A new legal architecture must construct renewable power alternatives. The successful demonstrated model for developing countries is examined in the article for a post-Kyoto legal protocol. Dimension 3: There must be incentives for in-country zeroemission renewable compliance options rather than non-C[O.sub.2] external offsets as a default option. Legal mechanisms must be carefully tailored to different regulatory systems. Dimension 4: The Kyoto Protocol contains no enforcement architecture or compliance mechanism. A method of legal enforcement, applicable in real time, must be implemented if international carbon control has any chance for success. Kyoto is an international legal system that requires a dimensionally cubed reform of its basic legal architecture to become anything other than an unsuccessful historical footnote. At risk is the warming of the planet and well-publicized catastrophes. Without all of these four dimensions of legal reform, the Kyoto Protocol lacks the requisite legal depth and coverage to function as an effective limit on global warming forecasted to take place in the 21st century. If the Kyoto Protocol continues beyond 2012 in its current legal format, as the April 2008 Bangkok and 2009 Copenhagen climate change conference now plan, (1) it will fail. Mere extension of the original Protocol will not work. There must be final alterations in the scope of the regulatory construct. This Article draws this new architecture for international carbon regulation in the above four dimensions. The final section of this Article examines whether U.S. carbon control legislation now working through the U.S. Congress could aid or remedy these Kyoto deficiencies. ABSTRACT: I. A NEW CUBIST CARBON ARCHITECTURE A. Legally Covered Countries B. CDM Zero-C[O.sub.2] Technology-Transfer C. Increasing In-Country Compliance D. Enforceable Implementation in Real Time II. THE FIRST DIMENSION: PARTICIPATION A. The New Math of Effective Kyoto Architecture B. Reforming Forest Architecture--Now Ineligible under Kyoto C. Black Carbon III. THE SECOND DIMENSION: REENGINEERING THE POWER BASE IN NON-ANNEX 1 DEVELOPING COUNTRIES A. …

Effectiveness of Base in Prism for Presbyopes with Convergence Insufficiency

Although the treatment of symptomatic convergence insufficiency (CI) with base-in (BI) prism in adults has a strong theoretical foundation, there have been very few studies addressing its efficacy. The purpose of this study was to investigate whether the application of BI prism, using a novel progressive addition lens design which incorporates BI prism in the near portion only, could help alleviate the symptoms in presbyopes with CI. A total of 29 symptomatic CI subjects aged 45 to 68 years were examined. All subjects took the CI Symptom Survey V-15 (CISS) and scored >or=16 points. Each subject was assigned two pairs of progressive addition glasses made by the same manufacturer in a randomized sequence, one with BI prism and one with the same lens prescription but no prism (placebo). Subjects wore each pair of glasses for 3 weeks and completed the CISS at the end of the 3rd week. Symptom level measured with CISS was the major outcome measure. The mean (standard deviation) CISS score was 30.21 (9.30) at baseline and decreased to 13.38 (9.44) with the BI-prism glasses, vs. 23.62 (10.76) with the placebo glasses. There were significant differences between the baseline survey score and the score with the BI-prism glasses (p < 0.0001) and between the score with placebo glasses and the one with BI-prism glasses (p = 0.001). The progressive addition glasses with BI-prism were found to be effective in alleviating symptoms of presbyopes with symptomatic CI.

Surgical Treatment of Internuclear Ophthalmoplegia and its Variants

The purpose of this study is to describe the surgical management of internuclear ophthalmoplegia (INO) and its variants. This is a retrospective, noncomparative, observational study of 15 surgical procedures on thirteen patients with symptoms attributed to INO which were conducted between December 1993 and October 2006. Surgical management was decided on the results of orthoptic measurements and tailored to each individual patient. In this group of 13 patients there were 4 cases of ‘wall-eyed’ bilateral INO (WEBINO) syndrome, 6 cases of bilateral INO with intact convergence and 3 cases of unilateral INO. The commonest indication for surgery was diplopia, either in primary or immediate lateral gaze, in 12 cases. The mean length of symptoms was 61 months (range 12 to 180). The mean angle of deviation pre-operatively was 25.7 prism diopters (PD) base-in (BI). Bilateral lateral rectus (LR) recession was used in 9 cases. Unilateral LR recession combined with medial rectus (MR) resection was performed in 2 cases. The remaining 4 cases had a unilateral LR recession. The mean post-operative angle of deviation was 11.6PD BI. The mean change in deviation was 14.6 PD. There were no intra- or post-operative surgical complications. Incomplete symptomatic relief in 2 patients necessitated a second surgical procedure. At final review all patients were asymptomatic. Surgery is an option that should be considered in all patients with an incompletely resolved INO. All our patients had complete relief from their symptoms. In the hands of an experienced strabismus surgeon, the surgery is routine. We show that patients who are willing for surgical intervention wait an average of 5 years for surgery and could be offered surgery more quickly.

Distance vergence adaptation is abnormal in subjects with convergence insufficiency

It is well known that in convergence insufficiency (CI) prism adaptation is reduced in response to base-out (BO) prisms at near. There have also been some suggestions in the literature that adaptation is reduced at other distances as well. The present data show that in CI adaptation is not only reduced in response to BO at near, but also in response to base-in (BI) at near and for both BI and BO at distance. This raises the interesting question whether distance adaptation becomes reduced because of reduced near adaptation or whether these subjects have a generally reduced horizontal adaptation mechanism.

Vergence facility: establishing clinical utility.

Vergence facility testing attempts to assess the ability of the fusional vergence system to respond rapidly and accurately to changing vergence demands over time [defined as the number of cycles per minute (cpm) that a stimulus can be fused through, alternating base-in (BI) and base-out (BO) prisms]. Decisions to use vergence facility as a clinical test are hampered by a lack of systematically gathered normative data. Twenty symptomatic and 20 control subjects with ages between 18 to 35 years of either sex and any race were pooled, based on vision-symptom level determined by a self-report questionnaire. Inclusion/exclusion criteria included vision correctable to 6/6 (20/20) Snellen acuity or better in each eye and normal phorias. Vergence facility response was tested over a 1-min period, using 16 combinations of BI/BO flip prisms at 4.0 and 0.4 m, based on Morgan's norms and pilot data. Horizontal vergence facility responses were not the same among those with and without symptoms, and not all magnitudes of BI/BO flip prisms produced the same response difference. A single flip prism, 3 delta BI/12 delta BO, was found to differentiate optimally between groups at distance and near. Repeatability of test results (with the 3 delta BI/12 delta BO prism) was poor at distance and good at near. In addition to providing valuable normative data, this study indicates that the vergence system nearly resets its "zero point" at any distance and sheds further light on the results of dynamic convergence and divergence stimulation on the accommodative-vergence system. From a clinical standpoint, the results improve the diagnosis of binocular vision abnormalities. The recommended near vergence facility test is easily implemented, using a commonly available flip prism (3 delta BI/12 delta BO) and having a clinical failure criterion that is easily recalled (15 cpm, sum of the BI and BO magnitudes).

Vergence facility and target type.

Target suppression-cues are considered important for valid binocular accommodative facility response. However, there are no comparable recommendations concerning the effect of target type on vergence facility response. Ten subjects ages 16 to 19 years of either sex and any race were pooled, based on the lack of any asthenopic symptoms determined by a verbal interview with the investigator. Inclusion/exclusion criteria included vision correctable to 6/6 (20/20) Snellen acuity or better in each eye, and near-normal phorias. Vergence facility response was tested over a 1-min period using 8 delta base-in (BI) and 20 delta base-out (BO) loose prisms at near (0.4 M) for 3 different vertically oriented targets: 6/9 (20/30) Snellen letters, back-illuminated anaglyphic shapes, and modified Wirt circles. For the group, the mean facility response was similar among the target types [Snellen letters: 9.5 cycles per minute (cpm) +/- 5.6; anaglyphic shapes: 9.0 cpm +/- 6.3; and Wirt circles: 9.4 cpm +/- 4.5]. Group response-differences were not significantly different by one-way ANOVA polynomial regression testing at the 0.05 level (F-value = 0.03, p = 0.97, df = 2). Whereas a binocular accommodative facility target must have additional vectographic or anaglyphic suppression-cues, vergence facility testing may incorporate a simple and available vertical row of 6/9 (20/30) Snellen letters, which provide inherent fusional suppression-cues, for a valid binocular response.

Comparison of Fixation Disparity Curve Variables Measured with the Sheedy Disparometer and the Wesson Fixation Disparity Card

Previous studies suggest differences in the fixation disparity curves obtained with the Sheedy Disparometer and the Wesson Fixation Disparity Card, the two most commonly used methods for measuring fixation disparity. In one study the investigators proposed that the differences do not exist for subgroups divided by phoria. The purpose of this paper is to try to clarify this issue by use of two large sets of data. Dissociated phorias were measured by the von Graefe method. Fixation disparity curves were plotted using the Disparometer and the Wesson card. Type I fixation disparity curves were most common with the Wesson card. Type II curves were found more often with the Disparometer than with the Wesson card. The x-intercepts were shifted in the base-in (BI) direction with the Wesson card compared to the Disparometer. The y-intercepts were shifted in the exo direction with the Wesson card compared to the Disparometer. The differences were statistically significant regardless of whether the dissociated phoria was exo or eso. The slope of the fixation disparity curve was steeper with the Wesson card than with the Disparometer. The difference was statistically significant for exophores but not for esophores. The differences between results obtained with the two instruments are not consistent from one subject to another as shown by high standard deviations of the differences. The fixation disparity curves measured with these two instruments are different. Fixation disparity parameters obtained from one of these instruments cannot be used with normative findings from the other.

住生活拠点の存在確認と拠点のとられ方 : 高齢期における住生活の拠点に関する研究 その1

住生活拠点の存在確認と拠点のとられ方 : 高齢期における住生活の拠点に関する研究 その1

Microstructural investigation of IN 939 superalloy

The vacuum cast nickel base IN 939 superalloy was investigated in the as-cast condition, as well as in the fully heat treated condition, i.e. after solution treatment followed by ageing. The alloy was characterized by optical microscopy, electron probe microanalysis and X-ray diffraction analysis. Volume fraction of the γ'-strengthening phase was determined by electrolytic phase extraction. The room and high temperature tensile properties and the Vickers hardness were determined for the as-cast and heat treated condition of the alloy. It was determined that the structure of the alloy consists of the γ-solid solution matrix, the γ'-intermetallic precipitate and various carbide phases. The simple heat treatment employed was shown to be effective in raising the γ' volume fraction and the yield and tensile stress.