摘要:

Thirty-five patients having paretic vertical strabismus were evaluated to determine which clinical parameters could best be used to differentiate congenital or early onset vertical strabismus from late onset vertical strabismus. Those patients with late onset deviations had a higher incidence of diplopia, a higher incidence of cyclodeviation, a higher incidence of compensatory head posture, and manifested larger vertical deviations in the primary position. However, the degree of incomitance, the prevalence of amblyopia, and the level of stereoacuity, did not distinguish the two patient groups. Prism therapy was equally successful for both groups.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Some subjects show a progressive increase in their near phoria, in the direction of more esophoria, when the test is repeated. Eighteen of 100 subjects showed 5Δor more esophoric shift. This result suggests that similar phoria changes may occur during prolonged intensive nearwork. The results reported are not the same as prism adaptation because the esophoric shift was found with dissociated targets. Autonomic arousal with sympathetic activation associated with heightened attention and concentration is proposed as the mechanism.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The perception of the eccentricity of a suprathreshold light flash (lll/4e) presented in a Goldmann perimeter was measured in four ophthalmologically normal observers and three young observers with retinitis pigmentosa (RP). The task was to indicate the perceived distance from central fixation of each light flash by making a mark on a 180-mm line drawn on a sheet of paper. In the center of the line was a hash mark. Observers were instructed that the hash mark should correspond to fixation and the ends of the line to the limits of the visual field. The vertical, horizontal, and both 45 oblique meridians were tested. The results showed that: 1. The extent of the field along the tested meridian determined perceived eccentricity, i.e., eccentricity of 45 in the temporal field of normals was perceived as equally eccentric as 30 in the superior field. 2. The central 20 were taken to represent more of the perceptual field than any other 20. 3. Along a meridian, the eccentricity which extends from fixation to 16% of the way to the field limit along the meridian is perceived as extending to 25% of the field by normal observers. 4. On the other hand, observers with RP reported that along a meridian the eccentricity extending from fixation to 8% of the field limit is perceived as extending to 25% of the field. Kinetic primary with the II/4 target showed no evidence of field constriction in observers with RP. However, losses in sensitivity are evident starting at about 10. Full field single flash electroretinograms were unrecordable in the observers with RP. The data were interpreted to reveal a perceptual magnification of the central field in the relatively early stages of RP.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Air traffic controllers perform a number of tasks which involve color identification, color discrimination, and color naming. Normal color vision is required for air traffic controllers, although the requirement is currently under review. The most critical task involving color is the distinction of red and black on flight strips; the distinction must be made reliably, quickly, and routinely for flight safety. In this study of four protanopes and three normals, all the protanopes were unable to make this distinction reliably under the lighting levels encounterd at air traffic control (ATC) centers, whereas none of the normals had any difficulty. Protanopes also made numerous errors with other ATC tasks involving color. The use of a red filter, often recommended to aid color defectives, actually made performance worse and additionally compounded the usual protanopic loss of brightness for red light. When Snellen visual acuity was tested using the red filters, protanopes needed up to four times larger letters than the color normals. It is concluded that protanopes have inadequate vision for safe performance of some current ATC tasks.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The steady-state accommodation response to Snellen letters of different sizes was measured with a laser-Badal optometer. It was found that the accommodation response was least when viewing the 6/9 letter size for both monocular and binocular observation at 6 m and increased when the letter size got smaller or larger. The mean accommodation response for the monocular viewing state was significantly higher than the binocular state for Snellen letter sizes between 6/4.7 and 6/12. At 40 cm the accommodation response for different letter sizes showed no obvious trend. However, the lag in binocular accommodation was significantly less than the monocular lag.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Seventeen subjects sustained focus for up to 8 min on targets placed either at the nearpoint (NP) or farpoint (FP) of accommodation. This was repeated in separate sessions from three to six times at each target distance and pre-to postexposure changes in dark focus (DF), i.e., accommodative hysteresis, were recorded. For eight subjects the probability (P) of exhibiting hysteresis effects was ≥ 0.50 on both types of sessions. Five additional subjects showed P(NP) ≥ 0.66 and P(FP) ≤ 0.33, whereas 4 subjects showed a reversed preference with P(NP) ≤ 0.17 and P(FP) ≥ 0.83. Thus, strong individual differences emerged with respect to susceptibility to accommodative hysteresis. Linear regression analyses were performed on the individual data of the 13 subjects in condition NP and 12 in condition FP who exhibited hysteresis effects on ≥ 50% of their sessions. Relative magnitudes of accommodative hysteresis resulting either from sustained NP or FP focusing were negatively related to the DF level measured directly before the period of sustained focus. Thus, for example, a relatively near initial DF correlated with a small inward shift of the DF after NP focusing, but with a large outward shift after FP focusing. Only in the FP condition was there evidence for a positive regression of hystereis effects on the dioptric distance separating the sustained focus target and the initial DF level, viz., the less the separation, the smaller the hysteresis effect. Accordingly, although the FP serves as a functional limit to FP-induced shifts in DF, the NP does not plays a corresponding role in the case of NP-induced hysteresis effects. Session to session fluctuations in DF thus have been shown to be Predictive of relative hysteresis magnitudes.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

The Howard-Dolman (H-D) is a version of Howard's Stereoacuity test (H) which has almost completely eclipsed the original. However, there is reason to believe that the H-D is not as good a test as the H. To find out whether or not the H-D gave results similar to the H, 34 subjects were tested by both procedures with the same Stereoacuity tester. This was fully automated and programmable. There are at least four ways of relating H-D findings to stereoacuity. None of these gave results comparable to those found with the H. Therefore, the H-D may be of questionable worth for clinical and scientific use. The same conclusion can be drawn regarding the relation between the H-D constant error and aniseikonia.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

Central corneal thickness changes were monitored in nine subjects who wore low water content hydrogel lenses of varying thickness for 3 h in the open and closed eye conditions. At the end of 3 h of lens wear, corneal de-swelling to prelens thickness for the different levels of hypoxia was determined by pachometry performed every 5 min for the first 30 min, every 10 min for the next 40 min, and every 15 min thereafter. Examination of the individual deswelling profiles indicates (1) a biphasic response in those with corneal edema greater than 14%, and (2) a large portion of the deswelling occurred during the first 30 min, followed by a more gradual rate until baseline was reached. Small amounts of corneal edema (less than 5%) required up to 25 min to return to baseline, whereas 6 to 15% required 30 to 70 min, and 20% required 95 min. The time taken for the cornea to deswell to baseline was linearly related to the amount of corneal swelling (r = 0.88; p < 0.0001).

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

In previous studies we have shown that subjects with normal binocular vision adapt to prism-induced heterophorias. In this study we have continued the work by investigating whether the oculomotor system can also adapt to lens-inuced heterophorias. It was found that subjects gradually adapted to the esophoria induced when viewing a distance chart through negative lenses. Adaptation also occurred to lens-induced esophoria and exophoria at near, while at distance, where the visual feedback was unaltered, the phoria remained virtually constant. These findings demonstrate the flexibility of the oculomotor system.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID

摘要:

A total of 447 female and 915 male presbyopic patients were examined in the Benin-City, Nigeria optometry clinic. Comparison of bifocal adds with published data from other areas of the globe suggests that climatic temperature has less effect on the age of onset of presbyopia than other authors have claimed.

ISSN:0093-7002    

出版商:OVID    

年代:1985

数据来源: OVID