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Behavorial assessment of visual function is now possible in 6- to 24-month-old children through the use of an operant preferential looking technique. Use of the technique to measure grating acuity shows that acuity develops from 6 to 8 min arc at 6 months of age to near adult levels by 2 years.
The mechanism of inhibition of binocular vision (at a cortical level in the Pavlovian sense) in convergent strabismus is described. The study concerns both those patients whith no amblyopia and those whose amblyopia has been cured. Part one of the article describe the clinical characteristics of this cortical inhibition as shown by the polarised light stereoscopic projector. Some basic concepts with this therapeutic application are described in part two. In this paper the author suggests a relationships between the severity of inhibition of binocularity and the degree of disturbance in spatial localisation. The greater the inhibition at a cortical level, the more disturbed is the localisation of objects in space in binocular vision. The treatment of inhibition must include precipitating causes that is to say the disturbed binocular relationships of abnormal retinal correspondence and is complete when cortical inhibition and abnormal retinal correspondence has been completely rectified. On the other hand there are occasions when it is not possible to eliminate abnormal retinal correspondence, this is especially true in older patients, and under this circumstances, it is better to accept inhibition of binocular function than to have diplopia.
A comparison between 100 percent correct response thresholds of stereopsis for nine subjects measured with and without viewing using a 33 percent difference in ocular image magnification is presented. Two subjects performed threshold settings, using the method of adjustments, with 1, 5, 10, 15, and 33 percent magnification differences. The extent of the increase explains reports of stereopsis in corrected unilateral aphakia.
A team approach directed at a total evaluation of an athlete's visual needs is essential to proper sports vision care. Consideration of the visual requirements of the athlete through observation of on-the-field performance enables the sports vision specialist to adapt specific therapy procedures that are pertinent to the player's overall athletic success.
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In a series of psychophysical experiments monocular and binocular reaction times (RTs) were measured in response to the presentation of sinusoidal grating patterns. Over a wide range of contrast values, binocular RT was consistently faster than monocular RT, even at high-contrast levels where RT had reached asymptotic levels. For observers with good stereopsis this binocular summation effect was greater than that expected on the basis of probability summation alone, whereas observers with deficient stereopsis performed at the level of probability summation. For normal observers broadband random noise presented to one eye produced an elevation in RT to gratings presented to the other eye; no such dichoptic masking effect was found in a stereoblind observer. These results validate the use of RT as an efficient, reliable measure of binocular interaction in human vision.
Interactions between direction-selective mechanisms for motion were examined in strabismic and anisometropic amblyopia. Amblyopes were found to have a marked reduction in sensitivity to flicker or movement when the amblyopic eye was presented with a combination of two gratings drifting in opposite directions at the same velocity (i.e., a counterphase grating). Sensitivity to flicker of the counterphase grating was improved by preadapting the amblyopic eyes to a single grating which was drifting nasalward, but there was no improvement if the drift of the adapting grating was temporalward. Sensitivity to flicker was also improved by reducing field size from 10 degrees to 3 degrees. However, occluding the central 4 degrees of the 10 degrees field did not significantly alter the sensitivity to flicker. These data suggest that inhibition between motion detectors in the parafovea of amblyopic eyes reduces slow-motion perception in both the parafovea and the fovea. The results also demonstrated a reduction in amblyopic eyes of direction slectivity for motion detection.
In connection with investigations to objectify the biological age the authors deal with questions of the relations between biological age and facts representing risks for normal aging. In this paper results are representing and discussed which are based on investigations to determine the biological age of juvenile and maturity diabetics and of a defined "normal" reference population. The investigations were done by the aid of a complex measuring and evaluation method and completed already published orientation studies on the biological age of obese patients and hypertonics. With a view to a normal course of aging a measurable premature aging in different age groups could be established for all three risk groups. The authors consider the above represented method in a modified form appropriate to contribute to answer practive relevant questions referring to the premature aging of certain risk groups from the clinical point of view.
Table 6 gives an example of a similar task (N10 print of 75% contrast) but with different requirements of fluency showing how much extra visual performance (acuity threshold, contrast threshold and magnification) is needed to achieve fluent reading. After the clinical assessment of visual function, it should be possible to categorize clients into three different groups on the basis of their threshold visual performance, each needing a different approach depending on their goals and needs as shown in Table 7. These are: Group I: Limited or no survival reading potential. Group II: Survival reading potential but limited likelihood of fluency. Group III: Clear survival reading potential with fluent reading possible if motivated. The author believes that it is always best to start with what the client has to read in order to maintain their independence, rather than what they wish to read for leisure, education or employment. Therefore, it is more successful to concentrate initially on spot/survival reading even if the client seems to have potential for regaining fluency. It should, however, be made clear to the client that this is the approach to be adopted. It is futile for the practitioner, as well as frustrating and demoralizing to the client, to press ahead with complex devices or wasteful trial and error sessions if, at an early stage, it is clear that the client will never return to fluent reading. Instead, it is far better to begin the move to vision substitution (e.g. audio-tapes) for leisure reading at an earlier stage. The overriding influence in low vision management is clearly the motivation of the client.(ABSTRACT TRUNCATED AT 250 WORDS)
1. The visual acuity with the Fresnel membrane prism is significantly less than that with the conventional prism of the same power for all prism powers from 12 delta through 30 delata at distance and from 15 delta through 30 delta at near. 2. The difference in the visual acuity between base up and base down, and between base in and base out, is not significantly different for either the Fresnel membrane prism or for the conventional prism. 3. For both Fresnel membrane prism and the conventional prism, the visual acuity when looking straight ahead. 4. Using Fresnel membrane prisms of the same power from different lots, the visual acuity varied significantly. The 30 delta prism caused the widest range in visual acuity. 5. When normal subjects are fitted with the higher powers of the Fresnel membrane prism, fusion and stereopsis are disrupted to such an extent that the use of this device to restore or to improve binocular vision in cases with large-angle deviations is seriously questioned. 6. Moreover, the disruption of fusion and stereopsis is abrupt and severe and does not parallel the decrease in visual acuity. The severely reduced ability to maintain fusion may be related to the optical aberrations, which, in turn, may be due to the molding process and the polyvinyl chloride molding material. 7. Through the flexibility of the membrane prism is a definite advantage, because of its proclivity to reduce visual acuity and increase aberrations its prescription for adults often must be limited to only one eye. 8. For the same reasons in the young child with binocular vision problems, the membrane prism presently available should be prescribed over both eyes only in powers less than 20 delta. When the membrane prism is to be used as a partial occluder (over one eye only), any power can be used. 9. The new Fresnel "hard" prism reduces visual acuity minimally and rarely disrupts binocularity, thus increasing the potential for prismotherapy to establish binocularity. This prism is currently available only for use as a trial set. Since the cosmetic appearance of the Fresnel "hard" prism is similar to that of the Fresnel membrane prism and it is easier to maintain, it would be the prism of choice (over all other types) for bilateral prescriptions in the young patient with emmetropia. The manufacturer is urged to make these prisms available to fit a special round adjustable frame, such as that developed in Europe for use with the wafer prism.
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The measurement of contrast sensitivity using gratings is a new clinical procedure which yields information about the functioning of the visual system. Previously, this type of information has not been readily obtainable in the clinical environment. This article includes the basic concepts of measuring contrast sensitivity with gratings and preliminary clinical results.
UNLABELLED: The aim of this study is to compare two modes of treatment of acute optic neuritis (AON). MATERIALS AND METHODS: 98 patients, treated between January 1992 and February 1995, after diagnosis of AON were included in this study. The diagnosis and results of treatment were determined on the basis of ophthalmological examination including visual acuity, perimetry, colour vision testing and neurological assessment. A comparison was made between the two treatment regimens of AON: oral and peribulbar injections of steroids versus intravenous administration followed by oral medication with steroids. The results are in agreement with other studies and show that intravenous steroids followed by oral steroids are more effective treatment of AON on its own or in association with MS.
BACKGROUND: The Missouri State Highway Patrol (MSHP) had 902 troopers on duty at the time of this study. The purpose of this study was to determine, for the first time, the visual characteristics of this group. METHODS: All 902 troopers were requested to be screened during early 1993 at their local MSHP troop headquarters. Vision screening was done by Department of Motor Vehicle Personnel using Keystone/Mast DVS II Driver Vision Screeners. The results, along with current prescriptions obtained from their eye care practitioners, were mailed to the author. RESULTS: A 94 percent response rate was achieved. The group's mean age was 38.7 years and most (98 percent) were male. Forty-seven percent wear an optical correction either some or all of the time and these were evenly divided between single vision and multifocal corrections. Seventy-four percent of eyes had uncorrected distance acuity of 20/20 increasing to 94 percent of eyes with 20/20 when corrections were worn. CONCLUSIONS: The results of this study will be used as a basis to update MSHP vision standards for acquisition and retention of troopers.
Twenty patients having associated heterophoria values of 2 delta and greater, as recorded with a Mallett unit, had their near monocular and binocular visual acuities measured. In the latter case, measurements were taken both with the associated heterophoria corrected by prisms and without prism correction. Bradford Near Vision charts, specially designed to measure visual acuity at near in seconds of arc, were used in the acuity measurement. The improvement of binocular acuity compared with monocular acuity was less than would occur in normal subjects without associated heterophorias. When the associated heterophorias were corrected with prisms the improvement in binocular over monocular acuity was similar to that found in normal subjects, with zero associated heterophoria readings.
The ocular globe is incompletely developed at the time of birth. The majority of sensorial and motor visual functions differentiate specifically after birth, in a certain chronology. The study of the visual function of the just-born child was based especially on the exams of reflexes, of the ocular globes motility, on the morphological aspect of the ocular globes and on the exam of the eye fundus, the exam of the visual acuity using preferential look (PL), and visual evoked potentials (VEP). The fact that the development of the visual function is directly dependent by the visual experience was emphasized. So the treatment of any ocular disease, which is manifest at bith-time or immediately after birth and which is disturbing the vision, must be done correctly and as soon as possible.
BACKGROUND: The use of a bioptic telescope for driving purposes has been controversial. This controversy has been fueled by confusion over which vision skills are needed for driving and how they are measured and developed. To make this issue even more complex, there are no standardized programs for evaluating patients and teaching basic vision skills needed to drive safely. METHODS: This paper will address vision skills and abilities which, intuitively, play an important role in driving. We will also propose a training program for the successful development of these skills since they relate to active driving, specifically, with a bioptic telescope. RESULTS: Our experience in working with patients who are partially sighted in the driving program seems to indicate that these patients have confidence in using their bioptic telescopic lens system for driving purposes. They appreciate and recognize the responsibility that comes with the independence that is gained from driving with the bioptic system. CONCLUSIONS: It is our hope that by providing these patients with appropriate care and training, we afford them the opportunity to adjust to their bioptic driving lens system and enjoy more years of independence and safe driving.
PURPOSE: To compare recognition (letter) and resolution (grating) acuity in eyes with and without retinopathy of prematurity (ROP) residua. METHOD: Letter acuity measured with the crowded HOTV chart or pocket cards (Good-Lite), and grating acuity measured with the Teller Acuity Card (TAC) procedure, were compared at the 3 1/2- and 4 1/2-year follow-up exams in the CRYO-ROP study. Testers were unaware of the retinal status of individual eyes. RESULTS: Measurable scores for both letter and grating acuity were obtained from 1694 eyes at 3 1/2 years and 2101 eyes at 4 1/2 years. Correlation analysis showed that the relation between crowded HOTV and grating acuity scores was best described by a quadratic function, with r2 values of 0.57 at 3 1/2 years and 0.68 at 4 1/2 years. Difference scores were calculated for each eye by subtracting the log of the HOTV score (converted to cyc/deg based on the convention that 20/20 = 30 cyc/deg) from the log TAC score. Normal eyes showed HOTV acuity that was higher than TAC acuity by an average of 0.37 octave (SD = 0.46, n = 1150) at 3 1/2 years and 0.27 octave (SD = 0.43, n = 1337) at 4 1/2 years. HOTV and grating acuity scores were similar to each other in eyes with retinal residua of ROP. Overall, eyes with acuity better than 20/150 to 20/300 tended to show better HOTV than grating acuity, whereas those with acuity below 20/150 to 20/300 generally showed better grating than HOTV acuity. CONCLUSIONS: There is a significant correlation between crowded HOTV letter acuity and TAC grating acuity in young children for normal eyes and eyes with ROP residua. In both groups of eyes, eyes with lower acuity show better grating than letter acuity, whereas eyes with better acuity show slightly higher letter than grating acuity.