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PubMed1989

Vision care in a juvenile detention facility.

Optometry plays a key role in the provision of vision care services at the San Bernardino Juvenile Hall (SBJH), where 400 juvenile offenders, aged 12 to 18 years, are incarcerated. This program in San Bernardino, California, was established in 1979 by a practicing optometrist with support from federal, state, and local funding agencies. It operates as an outreach clinical program to train senior students of the Southern California College of Optometry for professional practice opportunities in a nontraditional setting. An important component of the SBJH program is an ongoing clinical research program to study the relation between vision problems and juvenile delinquency, and the effect of vision training on the rehabilitation of delinquent youths. Preliminary data indicate a reduction in the recidivism rate for this population group.

Adolescent↗
PubMed1991

Quantitative scoring methods for D15 panel tests in the diagnosis of congenital color vision deficiencies.

Farnsworth's standard D15 and L'Anthony's desaturated D15 panel tests were administered to 99 congenital red-green color defective subjects. The results were analyzed in three ways: (1) by summing the color differences between adjacent caps according to Bowman, (2) by averaging color difference vectors (CDV) according to Vingrys and King-Smith, and (3) by visually inspecting and counting the crossings. The Bowman measure was highly correlated with one of the CDV measures but provides less information regarding a cap arrangement. The desaturated D15 test can be expected to misclassify 5% of dichromats by type (protan/deutan) compared to a type misclassification rate of less than 0.1% for the D15 panel test. The correct diagnostic rates for type were 45% for the standard D15 test and 58% for the desaturated D15 test. However, the improvement in correct diagnostic rate for the latter test was accompanied by an increase in the misdiagnostic rate from 2 to 10%. The main value of the desaturated D15 test in congenital color vision diagnosis would seem to be in providing classification of those subjects who pass the standard D15 test. Quantitative scoring of the tests provides a good estimate of severity of defect. Visual inspection provides a similar diagnostic rate to CDV analysis, but has a lower type misdiagnostic rate at the desaturated D15 test and is more likely to be correct when the two methods disagree. We suggest that quantitative scoring techniques are of limited benefit for the clinical diagnosis of congenital color vision defects but that they are of use in clinical trials or for the monitoring of changes in color vision over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Challenges in applying autofocus technology to low vision telescopes.

Autofocus (AF) low vision telescopes offer the potential to increase the acceptance and utilization of such low vision aids (LVA) by the visually impaired. Many patients resist conventional manual focus telescopes for a variety of reasons including appearance, field of view, weight, and utility. The elderly who comprise the significant part of the target population may also resist telescopes due to an avoidance of the technical challenge of its use. Although an AF telescope is technically advanced, it may allow for less manipulation by the wearer and hence enable its more effective application to visual tasks, especially in the near- to mid-range where depths of field narrow and the demands for focusing increase. There are many challenges involved in the application of AF technology to LVA including modification of the focusing range, signal processing for physiologically acceptable performance, and power and weight considerations. A preliminary infrared (IR) AF prototype based upon our recent work with the Ocutech Vision Enhancing System (VES) has been produced. Initial findings are presented which address the requirements of a subsequent version as well as the challenges that will be faced to optimize such a device.

Audiovisual Aids↗
PubMed1995

Effect of location and orientation uncertainty on r.m.s. contrast sensitivity with and without spatial noise in peripheral and foveal vision.

PURPOSE: We studied the effect of spatial location and orientation uncertainty on r.m.s. contrast sensitivity with and without external spatial noise in peripheral and foveal vision. METHODS: In the first experiment we used a small circular cosine grating with randomized location embedded in spatial noise and exposed for 33 to 533 ms in peripheral vision. In the second experiment, performed with and without noise, we varied the randomization range of stimulus location in a foveal search task with free eye movements and an unlimited exposure time. In the third experiment we used a vertical cosine grating exposed for 500 ms and varied the randomization range of aperture orientation in the fovea with and without noise. RESULTS: Uncertainty of spatial location had no effect on r.m.s. contrast sensitivity in the periphery or fovea. However, sensitivity decreased with increasing randomization range of aperture orientation in the fovea. CONCLUSIONS: Uncertainty of spatial location had no effect because the accuracy of positional information is inherently poor in peripheral vision, whereas in the fovea the effect of location uncertainty was compensated for by searching eye movements. Randomization of aperture orientation reduced contrast sensitivity in the fovea because in this case the effect of randomization could not be compensated for.

Adult↗
PubMed1997

Long wavelength pass filters designed for the management of color vision deficiencies.

This study reports on the effectiveness of long wavelength pass filters dispensed as tinted spectacles as an aid for individuals with congenital red-green color vision deficiencies. The effectiveness of the filters was evaluated by the performance on a series of clinical color vision tests and a questionnaire after the subjects had tried the lenses for 1 week. The lenses improved performance on color vision tests that required discrimination between large color differences, particularly between red and green hues. However, performance was degraded on tests which required fine color discrimination or used colors that were located parallel to the tritan confusion axis. The improved performance on certain tests was primarily based on brightness artificats induced by the filters, whereas the degraded performance on the other tests was due to the absorption of short- to midwavelength light by the filters. A slight majority (56%) of the subjects rated the filters as being moderate to highly effective in improving their color discrimination. Nevertheless, only 17% were interested in actually purchasing a pair. Common reasons for rejecting the filters were the color distortions produced by the red filters and fewer colors were actually perceived when wearing the filters.

Adolescent↗
PubMed1997

Effect of small focal errors on vision.

PURPOSE: The aim of this study was to quantify the effects of small plus focal errors on the quality of vision of wearers who habitually wear either no correction, or a low powered, distance only correction. METHODS: Patients wore spectacles with small errors deliberately included for a 2-day trial wear period; a short subjective questionnaire, and some laboratory measures of visual function were also used to assess the effects of these focus errors. RESULTS: A significant number of wearers notice, and are dissatisfied with, focal errors in distance vision as small as +0.25 D, in both sphere and cylinder. CONCLUSION: This finding supports clinical practice in refining the refraction to the nearest 0.25 D. It suggests that for critical applications and for critical patients, the practice of slightly undercorrecting hypermetropes should be applied, so that patients can use a little of their own accommodation for optimal distance vision.

Adult↗
PubMed1997

Relationship between contour plots and the limits of "clear and comfortable" vision in the near zone of progressive addition lenses.

PURPOSE: The aim of the study was to determine the relationship between the magnitude of surface astigmatism and subjective estimates of unacceptable blur flanking the near zone of progressive addition lenses (PALs). METHODS: Eleven presbyopic subjects observed a row of capital letters at a distance of 40 cm looking left and right within the near zone of six 2.00 D add PAL designs, stopping when they reached the limits of "clear and comfortable" vision. Eye rotations were measured by video-based pupil and corneal reflection tracking. RESULTS: There is a good correspondence between the 1.00 D astigmatic contour and the limits of clear and comfortable vision in the near zone of the six 2.00 D and PALs used in this experiment. CONCLUSIONS: Although the 1.00 D astigmatic contour indicates the boundary of clear vision, there are a number of caveats associated with the 1.00 D metric including the influence of laterally declining add power on perceived blur.

Eyeglasses↗
PubMed1998

Psychophysics of reading. XVII. Low-vision performance with four types of electronically magnified text.

Most people with low vision need magnification to read. Page navigation is the process of moving a magnifier during reading. Modern electronic technology can provide many alternatives for navigating through text. This study compared reading speeds for four methods of displaying text. The four methods varied in their page-navigation demands. The closed-circuit television (CCTV) and MOUSE methods involved manual navigation. The DRIFT method (horizontally drifting text) involved no manual navigation, but did involve both smooth-pursuit and saccadic eye movements. The rapid serial visual presentation (RSVP) method involved no manual navigation, and relatively few eye movements. There were 7 normal subjects and 12 low-vision subjects (7 with central-field loss, CFL group, and 5 with central fields intact, CFI group). The subjects read 70-word passages at speeds that yielded good comprehension. Taking the CCTV reading speed as a benchmark, neither the normal nor low-vision subjects had significantly different speeds with the MOUSE method. As expected from the reduced navigational demands, normal subjects read faster with the DRIFT method (85% faster) and the RSVP method (169%). The CFI group read significantly faster with DRIFT (43%) and RSVP (38%). The CFL group showed no significant differences in reading speed for the four methods.

Adolescent↗
PubMed2000

Repeatability and intercorrelations of standard vision tests as a function of age.

PURPOSE: We assessed repeatability and intercorrelations of five standard vision tests in subjects with normal vision. METHODS: Seventy-eight subjects (aged 21 to 68 years) completed five measurements each of high- and low-contrast visual acuity, near visual acuity and contrast sensitivity (Pelli-Robson chart). RESULTS: Except for correlations between high- and low-contrast visual acuity (r = 0.78), intercorrelations between tests were low to moderate (r < 0.5). For each measure, variability for the group was about one line on the chart (one triplet for the Pelli-Robson chart) and the minimum variability for an individual subject was about one third of this. On average, 1 to 2 lines can be expected to be lost over the normal lifespan on each test. Variability in responses did not increase significantly with age for any test. CONCLUSIONS: The criterion for judging change on commonly used clinical vision tests is about one line for subjects over a wide age range.

Adult↗
PubMed2001

Improvements in measures of vision and self-reported visual function after cataract extraction in patients with late-stage age-related maculopathy.

PURPOSE: A recent study indicated that patients with cataracts and early age-related maculopathy may benefit from cataract extraction. To ascertain whether cataract extraction in the presence of concurrent advanced age-related maculopathy was also associated with a clear benefit, we studied visual function and self-reported visual functioning in a cohort of 12 patients pre- and post-phakoemulsification. METHODS. All 12 patients had a diagnosis of advanced age-related maculopathy in the eye scheduled for cataract surgery. Preoperative assessment included refraction and recording of best corrected distance and near acuity and contrast sensitivity in both eyes. The Daily Living Tasks Dependent on Vision questionnaire was administered. After phakoemulsification and intraocular lens implantation, all patients were reviewed and assessed. RESULTS: After surgery, improvement in acuity was recorded in nine operated eyes, whereas acuity remained unchanged in three eyes. Improvement in contrast sensitivity in the operated eye occurred in 10 patients, but in two patients contrast was reduced postoperatively. In terms of self-reported visual functioning, improvement in the ability to undertake many daily living tasks dependent on vision was recorded after cataract surgery. CONCLUSIONS: Significant improvements in specific areas of self-reported visual functioning and measures of vision were recorded after cataract surgery. During the follow-up period, none of the operated eyes suffered a fall in visual acuity. There was also no evidence of worsening of the pre-existing macular lesion as judged by clinical examination and fundus photography.

Aged↗
PubMed1990

Prediction of postoperative vision in eyes with severe trauma.

The single most important factor determining the potential for return of useful vision in severely injured eyes is the magnitude of damage incurred by the macula or optic nerve at the time of injury. Most gravely injured eyes have media opacities that prevent funduscopic examination. In such eyes, the flash visually evoked potential is the single best predictor of postoperative vision. The second most reliable predictor is the bright-flash electroretinogram. Ultrasonography is an important part of the preoperative assessment of injured eyes with opaque media, but is of less value than electrophysiological testing in predicting postoperative vision in eyes with major trauma.

Adolescent↗
PubMed2004

Forms of vision correction: demographic factors in patient attitudes and perceptions.

PURPOSE: To evaluate attitudes toward current treatments for vision correction in a clinical population of adults wearing spectacles and contact lenses (CLs). METHODS: Patients seen in the Indiana University Contact Lens and Primary Care Clinics in the spring of 2002 completed multiple-choice questionnaires evaluating their current device for vision, comfort, convenience, health and safety, cost, and overall satisfaction. They also rated their interest in and the convenience and health and safety of 30-day continuous wear (CW), 7-day extended wear (EW), modern orthokeratology, and LASIK and were given a forced choice on their preferred method of vision correction. RESULTS: Three hundred forty-nine CL and 177 primary care patients completed questionnaires. Subjects reported high satisfaction with their current treatment. Seventy percent of glasses wearers were neutral or not interested in CLs or LASIK. CL patients were interested or very interested in orthokeratology (70%) followed by LASIK (65%), 7-day EW (51%), and 30-day CW (44%). Age and sex were the most significant factors that influenced wearing practices and attitudes, with males (especially young) indicating significantly higher use of EW than females (P = 0.0005, chi(2)). Males were also more interested in 7-day EW (P = 0.011) and 30-day CW (P = 0.001) and rated their health and safety higher (P = 0.045 and P = 0.003, respectively). CONCLUSIONS: In the spring of 2002, many of these patients remained cautious about the health and safety of 7-day EW and 30-day CW CLs.

Adult↗
PubMed2006

Categorical color naming of surface color codes by people with abnormal color vision.

PURPOSE: Past investigations of the ability of people with color vision deficiency (CVD) to name the colors of surface colors have been occupation-specific. This study was undertaken as a more generalized investigation to explore particularly the effects of stimulus size and shape. METHODS: One hundred CVD observers and 20 color vision normal (CVN) subjects named the colors of two sets of surface colors, each set presenting the same 10 colors (red, orange, brown, yellow, green, blue, purple, white, gray, black). One set presented dot stimuli in three sizes (2.4 degrees , 1.0 degrees , 0.27 degrees ) and the other line stimuli with three widths (0.50 degrees , 0.27 degrees , 0.14 degrees ). Color vision was diagnosed using the Ishihara test, the Farnsworth D15 test, the Medmont C100, and the Nagel anomaloscope. RESULTS: All CVN subjects and 37% of CVD subjects made no errors. Type of CVD and stimulus size were significant factors for probability of error and the effect of stimulus size is best described by 1/area. There were significant interactions between CVD type and 1/area and between shape and 1/area. Deuteranomals who passed the Farnsworth D15 test made significantly fewer errors than all other CVD types and 70% made no errors. Their common errors were to confuse red, orange, and brown. Protanomals who passed the Farnsworth D15 test made fewer errors than dichromats. CONCLUSIONS: Mild deuteranomals will make very few errors with a seven-color code that omits orange, brown, and purple and will make very few errors (approximately 0.3%) with a 10-color code when the stimuli are reasonably large (area >20 mm).

Adolescent↗
PubMed1994

Residual colour vision in a human hemianope: spectral responses and colour discrimination.

We present data for a patient, GY, with a right hemianopia caused by traumatic damage to the left occipital cortex. Previous studies have established that this patient has residual vision which enables him to detect and localize transient stimuli presented to his 'blind' hemifield. We have now examined spectral responses associated with this residual vision by using two-colour incremental threshold methods to measure II-spectral functions, and a white light background to examine spectral data for 'colour-opponent' characteristics. We report that both methods yield normal spectral response characteristics for GY's 'blind' hemifield. We have also investigated the patient's ability to identify, verbally, coloured stimuli presented to his 'blind' hemifield, and found that, in 'forced choice' experiments, he achieves a high proportion of correct responses to large stimuli. The patient reported that in threshold detection measurements his responses were based on the presence or absence of a percept associated with transient light stimulation of the 'blind' hemifield (residual vision), whereas colour naming was achieved without conscious perception of colour ('blindsight').

Accidents, Traffic↗
PubMed2004

Binocular vision: moving closer to reality.

Vision science is a truly interdisciplinary field of research, lying at the interface between psychology, computer science and neurobiology. It spans a broad range of research questions, from what visual neurons in the brain do, to the design and use of virtual reality technology. Here, I will take one well-researched area of human vision binocular depth perception, as an exemplar of the various ways in which the processes of human perception can be studied: from basic questions about the sensitivity of binocular vision to understanding how having two eyes helps us function in the natural environment.

Animals↗
PubMed1994

Spatial and temporal response properties of residual vision in a case of hemianopia.

Residual vision in subjects with damage of the primary visual cortex (striate cortex) has been demonstrated in many previous studies and is taken to reflect the properties of known subcortical and extrastriate visual pathways. In this report we describe psychophysical experiments carried out on a subject clinically blind in half of his visual field (i.e. homonymous hemianopia) caused by striate cortex damage. They reveal the existence of two distinct channels mediating such vision. One channel responds to spatial structure and the other to light flux changes. The spatially tuned channel has a peak response at about 1.2 cycles per degree and shows rapid loss of sensitivity at both high and low spatial frequencies. This channel does not respond to diffuse illumination. The light flux channel, however, responds only to sudden increments in light flux levels on the retina and shows extensive spatial summation. Both channels require transient inputs, with a peak sensitivity at about 10 cycles per second and show virtually complete attenuation at temporal frequencies below 2 cycles per second. The spatiotemporal characteristics of these two channels account for much of the reported limits of visual performance attributed to subcortical or extrastriate pathways in some patients, and especially for their relatively good sensitivity for the detection of abrupt, transient stimuli or fast-moving targets. A new method is also applied to the measurement of the amount of light scatter in the eye. The measurements show that light scatter into the sighted hemifield could not account for the results obtained with the stimuli used to characterized the residual vision of this subject.

Accidents, Traffic↗
PubMed1983

Transducin and the cyclic GMP phosphodiesterase: amplifier proteins in vision.

Our experiments have delineated the flow of information in the cyclic nucleotide cascade of vision of ROS. A single, photoexcited rhodopsin molecule activates several hundred phosphodiesterase molecules in two stages. First, photoexcited rhodopsin (R*) interacts with transducin (T), a peripheral membrane protein consisting of alpha- (39 kD), beta- (36 kD), and gamma- (approximately 10 kD) subunits. R* catalyzes the exchange of GTP for GDP bound to the subunit of transducin. About 500 T alpha- GTPs are produced per photoexcited rhodopsin at low light levels. T alpha-GTP, released from the beta- and gamma-subunits of transducin, then interacts with the phosphodiesterase to relieve the inhibitory constraint imposed by its gamma-subunit. Hydrolysis of GTP bound to T alpha serves to restore the system to the dark state. Transducin is the amplified signal carrier in this light-triggered cascade. The formation of hundreds of T alpha- GTPs is likely to be the first stage of amplification in visual excitation. The photoactivation of the phosphodiesterase in ROS closely resembles the activation of adenylate cyclase in hormone-sensitive cells. Our cholera toxin labeling studies have shown that transducin is akin to the signal-coupling G protein of the adenylate cyclase system. Cholera toxin specifically ADP- ribosylates and inactivates the GTPase activity of T alpha, just as it does with Gs. The action of pertussis toxin on ROS further underscores the homology of the photoreceptor and hormone-responsive systems. It seems likely that transducin, the stimulatory G protein, and the inhibitory G protein are members of the same family of signal-amplifying proteins. The study of the cyclic nucleotide cascade of vision is proving to be rewarding in affording a view of a recurring motif of signal amplification in nature in addition to providing insight into the mechanism of vision.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2006

Vehicle detection by means of stereo vision-based obstacles features extraction and monocular pattern analysis.

This paper presents a stereo vision system for the detection and distance computation of a preceding vehicle. It is divided in two major steps. Initially, a stereo vision-based algorithm is used to extract relevant three-dimensional (3-D) features in the scene, these features are investigated further in order to select the ones that belong to vertical objects only and not to the road or background. These 3-D vertical features are then used as a starting point for preceding vehicle detection; by using a symmetry operator, a match against a simplified model of a rear vehicle's shape is performed using a monocular vision-based approach that allows the identification of a preceding vehicle. In addition, using the 3-D information previously extracted, an accurate distance computation is performed.

Algorithms↗