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Biomedical subjects

J A Pratt-Johnson

Publications and source records attributed to J A Pratt-Johnson.

At least 19 recordsLinked to original sources
PubMed1991

Results of surgery to modify the null-zone position in congenital nystagmus.

The author reports the long-term (average 11 years) results of surgery to correct the face turn or tilt adopted to use the null zone associated with nystagmus. Of the 18 patients 16 had a face turn (7 with fusion and no strabismus, and 9 without fusion and strabismus) and 2 had a head tilt. Surgery was done after the age of 7 years (average 11 years), the same amount of surgery being done on all four horizontal rectus muscles in patients without strabismus to turn the eyes in the same direction as the face turn. Ten-millimetre recession/resection surgery produced the best correction of the face turn and the most gaze restriction. In patients with straight eyes before surgery strabismus was not produced or fusion or stereopsis lost. In patients with strabismus, surgery was modified on the nonfixing eye to correct the strabismus in addition to the face turn.

Adolescent↗
PubMed1989

Intractable diplopia after vision restoration in unilateral cataract.

Twenty-four patients lost their ability to fuse when their binocular function was disrupted for at least 2 1/2 years by a unilateral traumatic cataract or a unilateral traumatic cataract followed by uncorrected aphakia. Three patients were 6 years old, one was 8 years old, and the remaining 20 patients were aged 10 years or older at the time of the injury. All patients had intractable diplopia when the cataract was removed and the aphakia corrected. Aniseikonia was not the cause of this inability to fuse and the insertion of an intraocular lens provided no relief. The prognosis for the elimination of diplopia, other than by occlusion of one eye, was poor.

Adolescent↗
PubMed1988

Fusion ability lost and regained in visual adults.

The case reports are given of two adult patients who lost all fusion ability and had the signs and symptoms of central fusion disruption and intractable diplopia. Both patients suffered binocular sensory deprivation for several years caused by a combination of a traumatic cataract and uncorrected unilateral aphakia. One patient had a posterior chamber intraocular lens inserted to correct the aphakia and the other patient had a contact lens. Aniseikonia was not appreciated by either patient and did not appear to contribute to the fusion problem. Adjustable strabismus surgery, in both patients, and prism glasses, in one, enabled approximate superimposition of the visual axes. After several months, both patients began to develop some fusion with small amplitudes and the vertical bobbing typical of central fusion disruption disappeared.

Adult↗
PubMed1988

The loss of fusion in adults with intractable diplopia (central fusion disruption).

People over the age of 10 years can lose their fusion ability. This acquired disruption of fusion gives rise to intractable diplopia without suppression. An involuntary vertical bobbing movement of the non-fixing eye, present only with both eyes open, occurs at or near the angle of superimposition. This appears to be a unique and characteristic sign of acquired disruption of fusion and was present in all cases. Other causes of diplopia are mentioned and differentiated. Acquired central fusion disruption usually results from serious head injury. Partial recovery may occur but is unlikely. Sensory deprivation of at least 3 1/2 years' duration due to poor vision in one eye resulting from a traumatic cataract and sometimes subsequent uncorrected unilateral aphakia caused loss of fusion in 15 patients. The practical implications with regard to intraocular lenses and unilateral aphakia is discussed. Less commonly, vascular, neoplastic and presumed inflammatory lesions in the mid-brain area cause central fusion disruption.

Adult↗
PubMed1988

Complicated strabismus and adjustable sutures.

Clinical experience in performing over 500 adjustable strabismus operations is mentioned in this paper particularly as it relates to complicated strabismus. A maximum hang-loose recession of a rectus muscle has a limited effect, which is tabulated and the implications discussed. Aids in finding the lost medial rectus muscle are mentioned. Adjustable sutures are then exploited in managing the found "lost" medial rectus. Adjustable recession of both vertical recti in the affected eye were used in some cases of blow-out fracture to manage limitations of upward and downward gaze. Adjustable recession of both yoke medial recti are used in some unilateral superior oblique palsies where the main sequela is hypertropia in downward gaze only. A previously paralysed lateral rectus muscle, which has completely recovered function but has left the patient with a concomitant esotropia with full ductions and normal versions, responds excessively to resection. This should be taken into consideration when planning adjustable strabismus surgery in such a case.

Abducens Nerve↗
PubMed1985

Adjustable-suture strabismus surgery: a review of 255 consecutive cases.

Adjustable-suture strabismus surgery was performed on 255 patients under general anesthesia. Prophylactic topical and oral antibiotic therapy was used in all cases; only one postoperative infection occurred. Adjustments were needed for 123 patients and were done under topical tetracaine anesthesia within a few hours after recovery from general anesthesia. Overall the adjustments appeared to be reliable. The use of droperidol, however, made reliable adjustment impossible in two cases and is therefore strongly contraindicated if suture adjustment is to be done within a few hours of general anesthesia. There were two cases of temporary palsy of the muscle with the adjustable suture, presumed to be due to the topical anesthetic. Unexpectedly large effects of the surgery occurred in three cases of acquired sixth cranial nerve palsy in which full abduction had been recovered but a concomitant esotropia remained and in a few cases in which the muscles had previously been resected and there were normal active ductions preoperatively. Contraindications to the use of adjustable sutures in strabismus surgery may include multiple orbital fractures, previous orbital floor decompression for dysthyroid ophthalmopathy, and a variable angle.

Adolescent↗
PubMed1984

Suppression in strabismus--an update.

Previous reports have described suppression scotomas, suppression varying with the type of strabismus and suppression confined to one half of the retina (hemiretinal suppression). Our findings show that suppression in all varieties of strabismus, with the exception of the monofixation syndrome, involves the whole of the visual field of the deviating eye except for its monocular temporal crescent. In the monofixation syndrome our findings show a small central suppression scotoma involving the fovea but leaving the rest of the visual field of the deviating eye unsuppressed. We could find no evidence to support the concept of hemiretinal suppression but found evidence to support the presence of a trigger mechanism for suppression which operates on a hemiretinal basis.

Depth Perception↗
PubMed1984

Sensory outcome with nonsurgical management of esotropia with convergence excess (a high accommodative convergence/accommodation ratio).

Twenty-seven patients with esotropia and convergence excess (a high accommodative convergence/accommodation [AC/A] ratio) managed nonsurgically underwent a final standardized evaluation of their sensory and motor status after a follow-up period of at least 8 years. All had a deviation with distance fixation of less than 10 prism dioptres (PD) of esotropia with full optical correction both initially and throughout the follow-up period. The average spherical-equivalent refractive error was +2.3 D. The AC/A ratio had tended to decrease with age, and most patients had fusion, although only a small proportion had central fusion and stereopsis. Approximately half of the patients had been treated with bifocals, but their sensory outcome did not differ from that of the other patients. Miotics had not been used for more than a few months in any patient, as they were ineffective in reducing the deviation with near fixation to less than 10 PD of esotropia. A study, possibly a multicentre one, involving larger numbers of patients should be designed to find out whether bifocal therapy offers an advantage in the final sensory outcome of such patients.

Accommodation, Ocular↗
PubMed1983

Suppression in strabismus and the hemiretinal trigger mechanism.

A perimeter and a modified Lees screen were used to determine the area of visual field that is suppressed in strabismus. Strabismic patients without fusion suppress the whole area of the visual field of the deviating eye that could have correspondence with the dominant eye. In the monofixation syndrome, suppression only involves the fovea and the diplopic point of the deviating eye. Diplopia, if present, is appreciated throughout the visual field shared by the two eyes, except for the blind spots. No evidence of hemiretinal suppression was found in any type of horizontal strabismus, including exotropia. However, there is a hemiretinal trigger mechanism for suppression. Once suppression has been triggered by this mechanism, it involves the whole visual field of the deviating eye, except for the monocular temporal crescent.

Adolescent↗
PubMed1983

Sensory results following treatment of infantile esotropia.

Forty patients with infantile esotropia were treated by one ophthalmologist and followed up for 5 to 14 years. In all cases the initial surgery was performed by the age of 2 years, 4 months. The angle of deviation was reduced to within 10 prism diopters of orthotropia in 34 patients, and in 26 of them the reduction was maintained. However, only 6 of the 26 with a stable reduction showed evidence of binocular function by both troposcopic evaluation and the Wirt stereo test. Dissociated vertical divergence, nystagmus and amblyopia were much more common among the patients in whom fusion did not develop and may be the cause of this failure.

Child↗
PubMed1981

Visual results after removal of congenital cataracts before the age of 1 year.

Six patients underwent removal of congenital cataracts (Unilateral in three and bilateral in three) from otherwise normal eyes in the first year of life. Good corrected vision, including 6/9 in one of the unilateral cases, was obtained in each aphakic eye. A more aggressive approach to eliminating the sensory obstacles to seeing should include the removal of dressings 1 day after the operation, the use of soft, permanent-wear contact lenses within a few days thereafter and reduction of the time between the operations on bilateral cataracts to 5 days. In unilateral cases an occlusive patch must always be worn over the normal eye 90% of the waking day, even during illnesses.

Age Factors↗
PubMed1980

A pilot study of children with amblyopia treated by the gratings method.

A total of 6 patients, 2 with anisometropic, 2 with strabismic and anisometropic, and 2 with strabismic amblyopia treated with the 'gratings method' showed more than 2 lines of improvement in linear visual acuity. Patient attention and interest and repeated testing of the visual acuity were uncontrolled factors in this study. Moreover, the detailed visual tasks performed by the amblyopic eye may in themselves be the reason for improvement. Clearly a careful study which controls these possibilities is needed before a claim can be made that the 'gratings' per se offer an improved method of treatment of amblyopia.

Amblyopia↗
PubMed1979

Acquired central disruption of fusional amplitude.

Acquired central disruption of fusional amplitude is characterized by a complete loss of fusional amplitude, the patient maintaining fusion for only a moment under test conditions before breaking to constant diplopia. Under normal viewing conditions, the patient has constant diplopia with both eyes open. Patients who have bilateral superior oblique palsy may mimic this loss of fusion and constant diplopia, but they are distinguished by fusing readily on the troposcope, which compensates for the excyclotorsion, in contrast to prisms, which do not remove the double vision. Case reports document an association with convergence palsy, an infranuclear unilateral superior oblique palsy, and a nonparetic acquired strabismus in visual adults. Head trauma is the usual cause.

Adult↗
PubMed1979

Prismotherapy in intermittent exotropia. A preliminary report.

Twenty-five patients with intermittent exotropia and suppression were prescribed prisms which neutralised their maximum deviation. Thirteen patients failed to wear their prisms properly and served as controls and none were cured. Eight of the 12 patients who wore their corrective prisms more than half the time they were awake were cured.

Child↗
PubMed1977

Emotional factors in strabismus.

Emotional disturbance may cause strabismus which disappears when the disturbance is relieved. It is frequently the cause of a deterioration in the control of an esotropia particularly that associated with a high AC/A ratio. Two cases are reported. In the first, a concomitant esotropia was present in an adult with paranoid schizophrenia. This resolved completely after psychiatric treatment. The second case resembled a lateral rectus palsy. This also resolved on psychiatric treatment.

Adult↗