Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PHORIAS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1982

Uncertainty in the measurement of fixation disparity due to zones of perceived nonius alignment.

Fixation disparity was measured by means of limits within which nonius alignment was perceived. Two pairs of limits were found, one starting from perceived alignment and the other starting from perceived misalignment. These limits outline zones of perceived alignment of nonius lines. The extent of the zone of first perceived misalignment was found to be greater than that of first perceived alignment. The zone width can be expressed either in terms of disparity at a particular prism vergence or as a range of prism vergence at a particular disparity. The latter expression is comparable to what has been called the range of zero-associated phoria.

Computers↗
PubMed1997

Normal heterophoric changes: 20 years' follow-up.

BACKGROUND: Evaluation of changes in the heterophoric condition of 100 normal individuals over a 20-year period. METHODS: A retrospective study was undertaken. Charts of 100 normal men were reviewed. Individual changes in the heterophoric status were recorded over a 20-year period. The average value of the phoria at age 18-22 years was compared with the average value at age 34-38 years. Measurements were taken for near and distance fixation. No one was heterotropic. Changes in convergence and accommodation were also calculated. RESULTS: A 0.9 +/- 1.7 prism diopter increase in esophoria for distance fixation and a 0.6 +/- 2.5 prism diopter increase in exophoria for near fixation were found. These changes were statistically significant (P < 0.001 and P < 0.02 respectively). The near point of convergence receded by 0.5 +/- 1.1 cm (P < 0.001), and a decrease in accommodation over time of 2.8 +/- 1.4 diopters was found (P < 0.001). CONCLUSION: An increase in esophoria for distance fixation and a exophoria for near fixation was found in a 20-year follow-up of 100 normal subjects.

Accommodation, Ocular↗
PubMedDate not supplied

Egocentric visual target position and velocity coding: role of ocular muscle proprioception.

Limited knowledge is available regarding the processes by which the brain codes the velocity of visual targets with respect to the observer. Two models have been previously proposed to describe the visual target localization mechanism. Both assume that the necessary information is derived from the coding of the position of the eye in the orbit, either through a copy of the muscular activation (out flow model) or through eye muscle proprioception (in flow model). Eye velocity coding might be derived from velocity sensitive ocular muscle proprioceptors or from position coding signals through differentiation. We used techniques based on manual pointing and manual tracking of visual target, combined with passive deviation of one covered eye, to demonstrate that ocular muscle proprioception is involved in (i) eye-in-head position coding, hence in target localization function; (ii) long-term maintenance of ocular alignment (phoria); and (iii) sensing of visual target velocity with respect to the head. These observations support other data now available, describing the processes by which the brain codes position and velocity of visual targets. Such findings might interest engineers in the field of robotics who are facing the problem of providing robots with the ability to sense object position and velocity in order to create an internal model of their working environment.

Humans↗
PubMed1998

[New European medical flight safety guidelines. Their significance for the ophthalmologists].

In 1996 the new European Flight Crew Medical Requirements were finalized. The ophthalmological changes compared to the existing German standards range from the organization of evaluations to the necessary frequency of examinations. They also cover different examination techniques and different criteria for fitness. The changes in the requirements for ophthalmological fitness primarily affect ametropia, anisometropia, color vision and phoria. Knowledge of the European requirements is very important to advise pilots and any patient interested in becoming a pilot.

Accidents, Aviation↗
PubMed1979

Estimates of genetic correlations among clinical measures of the eye.

In a quantitative genetic investigation of seven clinical tests, five pairs were significantly correlated: (1) cover test measures and corneal power, (2) corneal power and divergence recovery points, (3) convergence and divergence recovery points, (4) divergence break and recovery points, and (5) convergence break and recovery points. Common genes may account entirely for the gene influence on cover test measure; thus, parents who are above the population mean for corneal power will have offspring with a tendency toward an exodeviation (phoria). The two convergence amplitudes may depend on the same gene differences, whereas the two divergence amplitudes only partly reflect a common function, suggesting that they may be indexing somewhat different underlying physiologic mechanisms.

Accommodation, Ocular↗
PubMedDate not supplied

Vertical prisms. How to avoid them.

Prescribing vertical prisms not infrequently leads to unsightly spectacles at best, and computing them may lead to errors at worst. Prismatic compensation for a particular reading point is of little value when the patient uses other eccentric portions of the lens, and it is not necessary if the patient learns to use (or continues to use) the optical centers. Clinical evaluation of eye-head posture and vertical phorias may reveal tell-tale clues in managing vertical imbalances in general and the anisometropic presbyope in particular.

Eyeglasses↗
PubMed1996

Adaptation of vertical eye alignment in relation to head tilt.

Binocular visual feedback is used to continually calibrate binocular eye alignment so that the retinal images of the two eyes remain in correspondence. Past experiments have shown that vertical eye alignment (measured as vertical phoria) can be altered by training to disparities that vary as a function of orbital eye position. The present experiments demonstrate that vertical eye alignment can also be trained to differ with head position when eye position (with respect to the orbit) is held constant. Changes in head position were about either an earth-vertical or earth-horizontal axis to distinguish otolith-ocular related adaptation from cervical-ocular related adaptation. Changes in head position were implemented by either by rotating the whole body (WB) or by rotating the head with the body stationary (HO). Following training, adaptation of eye alignment was observed in all cases of rotation about an earth-horizontal axis and for HO pitch rotations about an earth-vertical axis. The results illustrate the ability of the oculomotor system to compensate for imbalances in otolith-ocular pathways.

Adaptation, Physiological↗
PubMed1995

Visual training programme applied to precision shooting.

A three month visual training programme was conducted at the CAR of Sant Cugat (Olympic Training Center). Eleven members of 'The Catalan Government Special Intervention Squad' were used in a clinical trial. Pre-test and post-test results were obtained for pistol shooting, visual function, and psychological and physical states. Statistical analysis indicated significant gains in visual function and pistol shooting scores after the programme, while psychological (anxiety) and physical condition remained the same. Some conclusive statements can be made with regard to the relation of visual function improvement and shooting performance increment, after analysing the data. This improvement is evident in statistically significant post-test gains in the following variables: 'phoria at distance, recovery points in fusional reserves at distance, analytical amplitude, negative relative accommodation, saccadic fixations, and accommodative facility at distance and at near. The rest of the controlled visual variables also showed clinical improvement.

Accommodation, Ocular↗
PubMed2006

The sub-clinical see-saw nystagmus embedded in infantile nystagmus.

A transient, decompensated vertical phoria in an individual with infantile nystagmus syndrome (INS) resulted in two images that oscillated vertically-a diplopic oscillopsia. Ocular motor studies during the vertical oscillopsia recreated by vertical prisms, led to the identification of a sub-clinical see-saw nystagmus (SSN), present under the prism-induced diplopic condition. Retrospective analysis of ocular motor recordings made prior to the above episode of vertical diplopia revealed the presence of that same sub-clinical SSN. The SSN had not been detected previously despite extensive observations and recordings of this subject's pendular IN over a period of forty years. Three- dimensional search-coil data from fourteen additional INS subjects (with pendular and jerk waveforms) confirmed the existence of sub-clinical SSN embedded within the clinically detectable horizontal-torsional IN in seven of the fifteen and a sub-clinical, conjugate, vertical component in the remaining eight. Unlike the clinically visible SSN found in achiasma, the cause of this sub-clinical SSN is hypothesized to be due to a failure of the forces of the oblique muscles (responsible for the torsional component of the IN) to balance out the associated forces of the vertical recti; the net result is a small, sub-clinical SSN. Thus, so-called "horizontal" IN is actually a horizontal-torsional oscillation with a secondary, sub-clinical SSN or conjugate vertical component. The suppression of oscillopsia by efference copy in INS appears to be accomplished for each eye individually, even in a binocular individual. However, failure to fuse the two images results in oscillopsia of one of them.

Diplopia↗
PubMed1985

Ocular deviation after retinal detachment surgery.

Thirty patients with untreated rhegmatogenous retinal detachments underwent complete ocular muscle examinations before scleral buckling procedures. The examination was repeated three weeks, six weeks, three months, and six months after surgery. We found a high incidence of heterotropia after surgery; in most cases this resolved during the first six postoperative months. This resolution progressed from heterotropia to heterophoria to orthophoria. We believe this change results from phoria adaptation. Diplopia occurred in three patients. We found no statistically significant association between this diplopia and the type of surgery used.

Adult↗
PubMed1997

Context-specific adaptation of vertical vergence to correlates of eye position.

Vertical phoria (vertical vergence in the absence of binocular feedback) can be trained to vary with non-visual cues such as vertical conjugate eye position, horizontal conjugate eye position and horizontal vergence. These prior studies demonstrated a low-level association or coupling between vertical vergence and several oculomotor cues. As a test of the potential independence of multiple eye-position cues for vertical vergence, context-specific adaptation experiments were conducted in three orthogonal adapting planes (midsagittal, frontoparallel, and transverse). Four vertical disparities in each of these planes were associated with various combinations of two specific components of eye position. Vertical disparities in the plane were associated with horizontal vergence and vertical conjugate eye position; vertical disparities in the frontoparallel plane were associated with horizontal and vertical conjugate eye position; and vertical disparities in the transverse plane were associated with horizontal vergence and horizontal conjugate eye position. The results demonstrate that vertical vergence can be adapted to respond to specific combinations of two different sources of eye-position information. The results are modeled with an association matrix whose inputs are two classes of eye position and whose weighted output is vertical vergence.

Adaptation, Ocular↗
PubMed1998

Dynamics of horizontal vergence movements: interaction with horizontal and vertical saccades and relation with monocular preferences.

We studied the dynamics of pure vergence shifts and vergence shifts combined with vertical and horizontal saccades. It is known from earlier studies that horizontal saccades accelerate horizontal vergence. We wanted to obtain a more complete picture of the interactions between version and vergence. Therefore we studied pure version (horizontal and vertical), pure vergence (divergence and convergence) and combinations of both in five adult subjects with normal binocular vision and little phoria (< 5 degrees). The visual targets were LED's in isovergence arrays presented at two distances (35 and 130 cm) in a dimly lit room. Two targets were continuously lit during each trial and gaze-shifts were paced by a metronome. The two subjects with a strong monocular preference made vergence eye movements together with small horizontal saccades during pure vergence tasks. The other subjects, who did not have a strong monocular preference, made pure vergence movements (without saccades). These findings, suggest that monocular preferences influence the oculomotor strategy during vergence tasks. Vergence was facilitated by both horizontal and vertical saccades but vergence peak-velocity during horizontal saccades was higher than during vertical saccades.

Adult↗
PubMed2003

Effects of lesions of the cerebellar oculomotor vermis on eye movements in primate: binocular control.

The effects of lesions of the dorsal 'oculomotor' cerebellar vermis on binocular oculomotor functions in three monkeys were examined. Prominent findings included (1) a convergence bias during monocular fixation, i.e., an 'esodeviation' in the absence of disparity cues, (2) a loss of comitancy, i.e., alignment varies more with orbital position, (3) abnormal saccade yoking producing saccade disconjugacy, and (4) defects in prism-induced phoria adaptation. There was also a suggestion of a disturbance in the dynamic properties of disparity-induced vergence. These findings point to a role for the 'oculomotor' vermis in binocular aspects of the control of eye movements.

Adaptation, Physiological↗
PubMed1988

Asymptomatic physiologic hyperdeviation in peripheral gaze.

Asymptomatic hyperdeviation (HD) in peripheral gaze may be caused by muscle paresis, restrictive orbital diseases, cranial neuropathy, or skew deviation. The authors suspected that this finding was often physiologic and therefore examined 61 normal subjects with the Maddox rod. Forty-seven of 61 patients (77%) showed an HD of 2 prism diopters (PD) or greater in any field of gaze; 22 of these 47 patients (47%) showed an isolated left HD in right upgaze and right HD in left upgaze; an additional 15 of the 47 patients (32%) had either a right HD in left upgaze or a left HD in right upgaze. In only one patient was a vertical phoria evident in primary gaze. Ninety-four percent noted vertical diplopia where the deviation was found. In 40 of 47 patients (85%), a "V" pattern of less than 15 PD was detected. No HD in primary gaze on head tilt was elicited in those tested. Awareness of this highly prevalent physiologic HD, which follows the pattern of primary overaction of the inferior oblique muscle, may ward off erroneous neurologic diagnoses.

Adult↗
PubMed2001

The Correction of Myopia Evaluation Trial (COMET): design and general baseline characteristics.

The Correction of Myopia Evaluation Trial (COMET) is a multicenter, randomized, double-masked, controlled clinical trial evaluating whether there is a difference in the progression of myopia between children wearing progressive addition lenses (PALs) versus conventional single vision lenses (SVLs), as measured by cycloplegic autorefraction. Axial length, measured by A-scan ultrasonography, is an additional outcome measure. To meet the recruitment goal of 450 participants, eligible children ages 6-11 years (inclusive) with myopia in both eyes (spherical equivalent between -1.25 diopters (D) and -4.50 D, astigmatism < or = 1.50 D, and anisometropia < 1.00 D) were recruited at four clinical centers between September 1997 and September 1998. Children who participated were assigned to receive PALs (Varilux Comfort with a +2.00 D addition) or SVLs. Measures include standardized cycloplegic autorefraction (Nidek ARK700A autorefractor), axial length (Sonomed A2500 ultrasound), subjective refraction (Marco TRS system), visual acuity (modified Early Treatment Diabetic Retinopathy Study protocol), accommodation (Canon R-1), and phoria (cover test and Maddox rod). Outcome measures are collected annually; adherence is assessed and prescriptions updated semiannually. Participants are being followed for at least 3 years. COMET enrolled 469 children. Their mean age is 9.3 years (range 6-11 years); 52% are female. COMET children are ethnically diverse, according to a self-report with 46% White, 26% African American, 14% Hispanic, and 8% Asian. Best-corrected visual acuity is better than 20/32 in both eyes. Baseline mean (+/-SD) cycloplegic refractive correction is -2.38 D (+/-0.81) in the right eye and -2.40 D (+/-0.82) in the left eye; mean (+/-SD) axial length is 24.1 mm (+/-0.7) in both eyes. Follow-up of these children will provide a first step in answering the important question of whether there are effective means to slow myopia progression. Study results should be applicable to a large proportion of children with myopia. The study will also provide useful information on myopia progression in children wearing conventional single vision lenses.

Child↗
PubMed2003

Effects of Solanum melongena (garden egg) on some visual functions of visually active Igbos of Nigeria.

Solanum melongena LINN (garden egg) or bitter tomato is an economic flowering plant belonging to the family Solanaceae and widely distributed throughout the temperate and tropical regions. Members are mostly herbaceous plants, and the fruit is berry and the seeds have large endosperm and are grown mainly for food and medicinal purposes. The effects of bolus consumption of 10 g of S. melongena were undertaken on visually active male volunteers so as to determine its ocular complications. Results showed that the pupil size was reduced (23%), NPC was decreased (9%) and the AA was increased (22%) and the intraocular pressure dropped by 25% while there was no effect on VA, and the habitual phoria. The miotic effect lowered the intraocular pressure appreciably and the reduced NPC which was still within normal range did not produce any vision discomfort. The increased AA and convergence excess positively correlated provide an efficient visual mechanism. It is suggested that S. melongena would be of benefit to patients suffering from raised intraocular pressure (glaucoma) and convergence insufficiency.

Administration, Oral↗
PubMed2003

Ocular dynamics of systemic aqueous extracts of Xylopia aethiopica (African guinea pepper) seeds on visually active volunteers.

Xylopia aethiopica, African guinea pepper, is an angiosperm belonging to the family Annonecae, and used mainly as spice and in traditional medicine. The ocular dynamics of bolus consumption of 300 mg total dose was undertaken on visually active volunteers with a view to finding its ocular effects or complications. Results showed that the aqueous extract of X. aethiopica was neither a miotic nor a mydriatic, but lowered the intraocular pressure (17.48%), reduced the near point of convergence (31.1%) and increased the amplitude of accommodation (8.98%) which are positively correlated (r=0.95). On the other hand, the systemic extract had no effect on the visual acuity at far and near as well as the phoria status at the appropriate distances. The convergence excess resulted in esophoria and the increased amplitude of accommodation placed greater demand on accommodation mechanism without any discomfort. The nonspecific mechanism of action makes it a safer spice which can be exploited in the management of exophoria and raised intraocular pressure (glaucoma) in instances where the efficacy of the older conventional drugs is insufficient.

Adult↗
PubMed2004

Binocular vision impairment after refractive surgery.

PURPOSE: To illustrate the need for an accurate preoperative orthoptic examination to prevent postoperative changes in binocular vision. SETTING: Department of Ophthalmology, University Hospital Antwerp, Edegem, Belgium. METHODS: Five patients presenting major subjective complaints after refractive surgery were analyzed. RESULTS: In 1 patient, a latent N IV palsy decompensated after laser in situ keratomileusis (LASIK) in the more myopic eye to achieve monovision. A second patient, operated on for N IV palsy 10 years earlier, presented a recurrence of the palsy after bilateral LASIK for myopia. The third patient complained of discomfort in binocular vision caused by aggravation of a preexisting intermittent esotropia that worsened after LASIK for hyperopia. The fourth patient complained of diplopia after LASIK in the highly anisometropic and exotropic eye. The fifth patient experienced a decrease in fusion and stereopsis at the time he became anisometropic after bilateral LASIK. CONCLUSIONS: Special care should be taken of patients who have a preoperative history of strabismus surgery, an overcorrection or undercorrection in 1 or both eyes, or anisometropia and of those who are unhappy with contact lenses. An orthoptic examination should be done with and without spectacle correction to detect underlying vertical phorias. Intended monovision should be examined initially using contact lenses.

Adult↗