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PubMed1997

Algorithm for Purkinje images I and IV and limbus centre localization.

PURPOSE: To develop a fast and reliable image processing algorithm for the extraction of Purkinje reflection data for measurement of ocular alignment with standard PC hardware. METHODS: Purkinje images I and IV are specular reflections of light sources, the positions of which are proportional to eye rotation. Fast histogram-based thresholding and gradient techniques were used to localize Purkinje images I and IV, the pupil centre and the limbus centre in images obtained with near infrared light. RESULTS AND CONCLUSIONS: Execution time was 500 ms per eye. A set of 540 images was evaluated of which 94% were automatically analysed.

Accommodation, Ocular↗
PubMedDate not supplied

Bilateral myopia following blunt trauma to one eye.

PURPOSE: To evaluate bilateral myopia following blunt trauma to one eye. CASE REPORT: Traumatic myopia is a rare transient situation which may be seen in the injured eye or both eyes after blunt ocular trauma. We examined one case with transient myopia in the left eye which had been exposed to a blunt ocular injury. Myopia was also observed in the right eye 12 hours after the trauma. The right eye and left eye had reverted to emmetropia respectively two and six weeks after trauma. DISCUSSION: The myopia may have been due to ciliary spasm arising from stimulation of the efferent autonomic system in the right eye and ciliary body edema in the left eye. CONCLUSIONS: To our knowledge, this is the first reported case developing bilateral transient myopia after the blunt trauma to only one eye.

Accommodation, Ocular↗
PubMed1989

The effects of 0.025% hyoscine hydrobromide eyedrops on visual function in man.

Instillation of three drops of 0.025% hyoscine hydrobromide into one eye at 5 min intervals caused a mydriasis and cycloplegia of rapid onset and of 4-6 days' duration; this was similar to the previously reported actions of concentrations of up to 0.5%. After refraction for the working distance of the experiments, contrast sensitivity to stationary oscilloscope-generated grating patterns of 10 and 20 c/deg was unaffected despite the mydriasis. Also, contrast sensitivity to laser interference fringes of 10 and 20 c/deg observed in the Maxwellian view, in which the effects of the ocular media are bypassed, was unaffected. Contrast sensitivity to a 3 c/deg phase-reversed grating pattern was, however, transiently reduced by 40% after hyoscine. A second series of experiments showed a deleterious effect of hyoscine on contrast sensitivity to both stationary and phase-reversed grating patterns of 2, 3 and 5 c/deg while contrast sensitivity at 10 c/deg was not consistently affected. These results were explained by a direct deleterious action of hyoscine at the level of the retina, specific to channels that detect low spatial frequencies.

Accommodation, Ocular↗
PubMed1979

Ophthalmologic safety of long-term hydroxychloroquine treatment.

Ocular toxicity of long-term hydroxychloroquine treatment was assessed by regular ophthalmologic examinations in 99 patients. No patient developed significant loss of vision or visual field constriction to a white test object. Three patients had evidence of toxicity, but the medication had to be permanently discontinued in only one who subsequently had regression of all abnormalities except visual field constriction to a red test object. Neither duration of treatment nor the diagnosis of systemic lupus erythematosus predisposed patients to toxicity.

Accommodation, Ocular↗
PubMed2003

[Asthenopic complaints and ocular convergence at the computer workstation: new test procedures for practice and research].

BACKGROUND: The present paper summarizes a series of ergonomic studies on the relation between asthenopic complaints and binocular vision at the computer workstation. In particular, the paper reports on measurements of the accuracy of ocular convergence during fixation of central fusion stimuli (i. e. fixation disparity) as a function of viewing distance. METHODS: Different versions of subjective tests for fixation disparity (using dichoptic nonius lines) are presented, including a computer-controlled procedure (the eye-test PC). RESULTS: These new tests suggest that non-presbyopic subjects with normal binocular vision may suffer from asthenopic complaints if they have - in near vision - an exo fixation disparity larger than average. CONCLUSION: In these cases, the stress exercised on the convergence system can be reduced by using a longer viewing distance at the workplace.

Accommodation, Ocular↗
PubMedDate not supplied

Infantile esotropia: results in the neurologic impaired and "normal" child at NCMH (six years).

Charts of all infantile esotropes who received their primary surgical procedure at the North Carolina Memorial Hospital, between February 1978 and June 1984 were reviewed. Neurologic problems (general and ocular) were identified in 29 of the 47 patients (61.7%) followed a minimum three months (mean = 25.0 +/- 2.9 mos). Frequent general neurologic problems were prematurity, hydrocephalus, mental retardation, cerebral palsy, meningomyelocele, intraventricular hemorrhage, and seizures (neonatal and/or postnatal). Abducens nerve palsy was the most common ocular neurologic impairment. Neurologic impaired esotropes were older (mean = 31.9 +/- 3.8 mos) than the "normal" group (mean = 17.0 +/- 3.3 mos) at the time of surgery. Recession/resection procedures were performed on 13 (44.8%) of the neurologically impaired and nine (50.0%) of the normal esotropes. Bimedial recessions were employed on 12 (41.4%) of the patients with neurologic problems and seven (38.8%) of the normal esotropes. Unilateral medial recessions and/or inferior oblique recessions were performed on six patients. At last follow-up, orthophoria (+/- 10 delta) was present in 16 (55.2%) neurologically impaired patients and 15 (83.3%) normal esotropes (p less than 0.05 by the normal deviate (z) test). Seven (24.1%) neurologically impaired patients had residual esotropia, while consecutive exotropia was present in six (20.7%) patients. Among normal esotropes, residual esotropia was found in one patient and consecutive exotropia in two (11.1%) patients. DVD's occurred in nine patients while four subjects developed a postoperative accommodative component.

Accommodation, Ocular↗
PubMed2002

[Children and adolescents with Down syndrome. Continuous ophthalmological monitoring crucial!].

Children with Down's syndrome are at increased risk of ocular manifestations, which is confirmed by a study in Uppsala, Sweden. Sixty percent of the children were wearing glasses and/or had other ocular problems. However, lapses were found in follow-up and referral to the eye clinic. Good visual function is an important prerequisite for optimal quality of life of children and adults with Down's syndrome. Since this group does not always spontaneously get in touch with the health care system including ophthalmologists, the infant must be referred by the pediatrician immediately after birth. The number of individuals with Down's syndrome in Sweden is large (3,500-5,000), and an ophthalmological follow-up program, as presented in this paper, is of key importance.

Accommodation, Ocular↗
PubMed1993

Thalamic infarctions: differential effects on vestibular function in the roll plane (35 patients).

We determined the subjective visual vertical (SVV), ocular torsion (OT), skew deviation, and lateral head tilt in 35 patients with acute thalamic infarctions (14 paramedian, 17 posterolateral, and four anterior polar) and in five patients with mesodiencephalic hemorrhages to obtain the tonic effects on vestibular function in the roll plane. Eight of 14 paramedian infarctions had complete ocular tilt reaction (OTR) with contraversive head tilt, skew deviation, OT, and SVV tilt. The OTR was due to ischemia of the rostral midbrain tegmentum, including the interstitial nucleus of Cajal (INC), and not to thalamic ischemia. Thus, the INC (and the rostral interstitial nucleus of the medial longitudinal fascicle) is the most rostral brainstem structure mediating eye-head coordination in roll. Eleven of 17 posterolateral infarctions exhibited moderate SVV tilts that were either ipsiversive or contraversive. In these 11 cases, vestibular thalamic nuclei (nucleus ventro-oralis intermedius, nucleus ventrocaudalis externus, and nucleus dorsocaudalis) were involved; infarctions in the remaining six were more ventromedial. Anterior polar infarctions did not affect vestibular function in roll.

Accommodation, Ocular↗
PubMed1996

Ultrasound biomicroscopy of the anterior segment.

BACKGROUND: New imaging technologies are revolutionizing the understanding and treatment of a wide variety of ocular disorders. Confocal scanning laser ophthalmoscopy, ultrasound biomicroscopy, confocal scanning laser polarimetry, color doppler imaging of blood flow, and optical coherence tomography are providing important information regarding disease pathophysiology, diagnosis, progression, and treatment. METHODS: High frequency (50 MHz), high resolution ultrasound biomicroscopy of the anterior segment was obtained in a wide variety of disorders of the anterior segment. Tissue resolution is approximately 50 microns and the penetration depth is 5 mm. RESULTS: Ultrasound biomicroscopy is capable of imaging the comea, iris, anterior chamber, anterior chamber angle, posterior chamber, and ciliary body with great detail. The structures surrounding the posterior chamber, previously hidden from clinical observation, can be imaged and their normal anatomic relationships assessed. The various forms of angle closure glaucoma, such as pupillary block and plateau iris configuration, can be differentiated. The concave iris found in pigment dispersion and its response to treatment can be assessed. Visualization of anterior segment anatomy in eyes with opaque media is possible. CONCLUSIONS: Ultrasound biomicroscopy assists in the management of eyes with disorders of the anterior segment. Future applications of this technology will yield important information regarding accommodation, normal ocular physiology and disease pathophysiology.

Anterior Eye Segment↗
PubMed1990

Ocular digitalis effects in normal subjects.

Several visual functions were examined before and during self-application of therapeutic doses of digitoxin. The ERG recordings showed a reduction of the critical flicker fusion frequency from 70 Hz to 35-40 Hz. Recovery of color vision after macular photostress was examined with Nagel's anomaloscope and Jaeger's tritanomaloscope. After digitoxin intake the matching range at the tritanomaloscope was enlarged. Following macular photostress the recovery time of both the Rayleigh and the Trendelenburg matches was significantly prolonged. The mesoptometer readings did not show any changes during the application of digitalis. This demonstrates that the process of neural adaptation is intact during digitoxin therapy. The error score in the Lanthony desaturated 15 panel test was slightly increased after digitalis application. The Farnsworth-Munsell 100-hue test showed a marked increase in the total error score. There were no changes in the standard panel D-15. The Ishihara pseudoisochromatic plates were read without mistakes after digitalis medication. The chromatic visual acuity for red-green and blue was examined by recording the maximum reading distance for the Velhagen pseudoisochromatic plates "65" (Jaeger's test) and "49". For both plates the reading distance was reduced by 50% during digitoxin therapy. Computerized perimetry by colored stimuli (Tübingen Automatic Perimeter by Aulhorn and Durst) did not reveal any definitive changes in sensitivity thresholds with therapeutic serum levels of digitalis. Spectral increment sensitivity for the isolated blue cone system (Wald-Marré approach) was not influenced by therapeutic doses of digitoxin. Topical digitoxin application (0.02 mg/10 ml) did not interfere with the pupillary light reflex (infrared pupillography) or with the accommodative amplitude or intraocular pressure. It did, however, result in toxic keratopathy with swelling of endothelial cells and edema of the corneal stroma and epithelium. All changes disappeared after withdrawal of digitalis.

Accommodation, Ocular↗
PubMed2001

Ultrasound biomicroscopy of the aging rhesus monkey ciliary region.

Ultrasound biomicroscopy of the living rhesus monkey ocular ciliary region was undertaken to identify age-dependent changes that might relate to the progression of presbyopia. Monkeys were anesthetized and pharmacologically cyclopleged, the eyelids were held open with a lid speculum, and sutures were placed beneath the medial and lateral rectus muscles. Ultrasound biomicroscopy imaging of the nasal and temporal quadrants of the eye were performed, and the live images were recorded to videotape. Subsequent image analysis was performed to obtain objective morphometric measurements of the ciliary body region. The ciliary body inner radius of curvature, outer radius of curvature, inner arc length, area, thickness, perimeter, zonular fiber length, and circumlental space were measured. Zonular space was calculated. The circumlental space decreased with increasing age in the temporal quadrant. The other morphologic measurements were not significantly correlated with age or body weight. Most morphologic measurements were significantly different comparing temporal vs. nasal quadrants. Bifurcation of the posterior zonular fibers was frequently observed. Although temporal circumlental space was the only measurement found to change with age, ultrasound biomicroscopy of the living rhesus ciliary region did identify distinct nasal vs. temporal asymmetries, which may reflect anatomical requirements for convergence-associated accommodation.

Accommodation, Ocular↗
PubMed1996

Effects on the compensatory responses to positive and negative lenses of intermittent lens wear and ciliary nerve section in chicks.

This study examined the ocular compensation to lens-induced defocus in chick and the effect of interrupting lens wear on a daily basis. Eyes fitted with +10 D lenses at hatching compensated rapidly, with almost complete compensation after 4 days of lens wear; they had decreased vitreous chamber depth compared to normal eyes and were thus hyperopic when the lenses were removed. In contrast, adaptation to the -10 D lenses was much slower, was still incomplete after 9 days of lens wear, and in this case, eyes had increased vitreous chamber depth and were myopic without the lenses. Adaptation improved when lens wear was delayed until 7 days after hatching. The effect of interrupting lens wear by periods of normal vision varied with the sign of the lenses worn. Hyperopia was always seen in response to +10 D lenses, although the magnitude of the response decreased as the duration of lens wear was decreased. In contrast, even brief periods of normal vision, i.e., 3 hr, prevented the development of myopia in response to the -10 D lenses; this apparent sensitivity to normal vision is similar to that reported for form-deprivation myopia. Ciliary nerve section used here to eliminate accommodation did not alter these response patterns.

Accommodation, Ocular↗
PubMed2005

Postblink changes in the ocular modulation transfer function measured by a double-pass method.

PURPOSE: To examine the temporal changes in the modulation transfer function (MTF) of the eye after a blink. METHODS: The distance MTF of a 5-mm pupil was derived from double-pass retinal images in 20 healthy young subjects at various intervals after a blink (1 second up to 15 seconds). Such measurements include the effects of wavefront aberration, scattered light, and errors in focus and are thus more relevant to real life than are estimates of MTF based on wavefront errors alone. RESULTS: Optimal MTF by a variety of criteria was found some 6 seconds after a blink. CONCLUSIONS: Inclusion of the effects of stray light and errors of focus does not affect the finding that optimal retinal image quality occurs some time after a blink. It does not appear that a loss in optical quality is the trigger of normal blinking.

Accommodation, Ocular↗
PubMed2005

Biometry accuracy using zero- and negative-powered intraocular lenses.

PURPOSE: To audit the accuracy of biometry using the SRK/T formula when negative- or zero-powered intraocular lenses (IOLs) are predicted and to compare the results between A-scan, B-scan, and optical methods of biometry. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: This retrospective analysis comprised 78 eyes of 54 patients having cataract surgery with zero- or negative-powered IOLs. Axial lengths were measured with A-scan, B-scan, applanation, or optical methods. Differences between SRK/T-predicted and actual postoperative refraction were analyzed for 75 eyes having cataract surgery. Ocular comorbidity, visual acuity, and biometry readings were also compared. RESULTS: Forty-one percent of 75 patients analyzed were within +/-1.00 diopter (D) of the predicted refraction, although there was a significant tendency toward a hyperopic overcorrection by 1.14 D (95% confidence interval, 0.89-1.39 D). This overcorrection error was consistent across all 3 biometry methods used to estimate axial length and increased with the use of stronger (more negative) IOLs. CONCLUSION: Surgeons should be aware of the tendency for negative-powered lenses to overcorrect and lead to a hyperopic outcome when using the SRK/T biometry formula in highly myopic eyes. A weaker-powered negative IOL is recommended to aim for a more myopic postoperative outcome by about 1.00 to 2.00 D.

Accommodation, Ocular↗
PubMed1999

Slanted lateral rectus recession for exotropia with convergence weakness.

OBJECTIVE: To evaluate the efficacy of slanted recession of the lateral rectus (LR) muscle for exotropia (XT) with convergence weakness. DESIGN: Predesigned, nonrandomized, comparative trial. PARTICIPANTS: Twelve study patients and six control subjects with XT greater at near than at distance by > or =10 prism diopters (PD). INTERVENTION: Twelve consecutive patients underwent slanted LR recession, and six consecutive control subjects underwent standard LR recession. MAIN OUTCOME MEASURES: Between-groups comparison of the postoperative ocular alignment at distance and near, and the difference between them, as well as the stereopsis. RESULTS: Slanted LR recession reduced the XT to <8 PD in all patients at distance and in 11/12 patients at near. Additionally, the mean difference between the distance and near exodeviation was reduced from 14+/-4.5 PD preoperatively to 2.9+/-2.4 PD postoperatively. All patients in the control group demonstrated postoperative deviations of <8 PD at distance, but all had residual exodeviations >8 PD at near. Three of the study patients gained gross stereopsis postoperatively. CONCLUSIONS: Slanted recession of the LR is superior to standard recession in reducing both distance and near XT and in collapsing the difference between them. This technique may also have a positive impact on gross stereopsis.

Accommodation, Ocular↗
PubMed2006

Neuro-ophthalmologic manifestations of psychogenic disease.

From a neuro-ophthalmologic standpoint, five areas may be affected by psychogenic disease: (1) vision, including visual acuity and visual field; (2) ocular motility and alignment; (3) pupillary size and reactivity; (4) eyelid position and function; and (5) corneal and facial sensation. The physician faced with a patient complaining of decreased vision or some other disturbance related to the afferent or efferent visual systems for which there is no apparent biologic explanation has three responsibilities. First, the physician must ascertain that an organic disorder is not present. Second, the physician should induce the patient to see or do something that would not be possible if the condition were organic in nature. Finally, the physician should attempt to determine whether the patient has an underlying psychiatric disease or is experiencing psychosocial stress. In this article, manifestations of psychogenic disease as they pertain to vision are considered, and, where appropriate, the various methods used to diagnose and treat these phenomena are discussed.

Accommodation, Ocular↗
PubMed2002

Myopia: attempts to arrest progression.

Previous studies have evaluated the efficacy of several interventions to decrease the progression of myopia. These include devices that alter the perception of the visual environment and pharmacological treatments. There is no conclusive evidence thus far that alteration of the pattern of spectacle wear, bifocals, ocular hypotensives, or contact lenses retards the progression of myopia. Several randomised clinical trials have demonstrated that the rate of progression of myopia is lower in children given atropine eye drops than those given placebo. However, atropine is associated with short term side effects such as photophobia and possible long term adverse events including light induced retinal damage and cataract formation. Other more selective antimuscarinic agents such as pirenzipine are presently being evaluated. Further well conducted randomised clinical trials with large sample sizes and adequate follow up designed to evaluate treatments to retard the progression of myopia should be conducted, since the identification of an effective intervention may have a greater public health impact on the burden and morbidity from myopia than the few treatments currently available.

Accommodation, Ocular↗
PubMed1997

Expanding forces in aqueous outflow pathways of a nonaccommodating mammal: an approach via comparative dynamic morphology.

Six dog eyes were fixed by intracameral perfusion of fixative at pressures of 0, 5, 10, 15, 20, and 25 cm of water. Eight dog eyes were fixed after the injection in both ocular chambers of a number of cholinergic agents, either singly or in combination. Under the effect of miotics and under increased ocular pressure, the aqueous pathways expand. An analysis of the forces involved in expansion of the exit pathways reveals the primary role of the detached ciliary body in nonaccommodating mammals. Two mechanisms appear to have been conserved in dogs and humans throughout evolution. The first is an active mechanism: the opening of the trabecular meshwork as a consequence of the combined action of the ciliary muscle and the iris and its insertion ligaments-the uveoscleral trabeculate-in dogs, and the longitudinal portion of the ciliary muscle and scleral spur in humans. The second is a passive mechanism: the infundibular arrangement of the drainage structures assisted by the traction on the zonular ligament of the lens, which responds to an increase in pressure in the anterior chamber by widening the pathways, thus favoring outflow.

Accommodation, Ocular↗