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Biomedical subjects

K W Wright

Publications and source records attributed to K W Wright.

At least 37 records · Page 2Linked to original sources
PubMed1994

Strabismus management.

In this article, three topics of current interest in strabismus are covered. These include strabismus after glaucoma implant surgery, management of accommodative esotropia, and the timing of treatment for strabismic amblyopia. Glaucoma implants have improved our results with difficult glaucoma syndromes, however, a high incidence of postoperative strabismus has been associated with this procedure. The mechanism of the strabismus has not been clearly defined in previous literature, but in this article we describe three mechanisms that cause strabismus after glaucoma implant surgery and describe methods for managing this problem. The standard management of accommodative esotropia has historically resulted in a large number of undercorrections. Patients with accommodative esotropia have good fusion potential as the strabismus is acquired and binocular visual development occurred during the critical period. Recent studies indicate that we should increase our surgical numbers when managing patients with accommodative esotropia. Various treatment strategies are covered in the section on accommodative esotropia. Finally, a discussion on the management of strabismic amblyopia is presented. The importance of treating amblyopia first, then secondarily correcting the strabismus is emphasized.

Accommodation, Ocular↗
PubMed1993

Surgical techniques of strabismus.

Improvements in the management of strabismus are largely dependent on making the specific diagnosis and differentiating patterns of strabismus. This finding is especially true in the management of superior oblique paresis because there are various types. Recent observation suggests that superior oblique paresis may be associated with a lax superior oblique tendon and that the cause of the paresis is not always neurogenic. Some authorities have suggested using the traction test of the superior oblique to determine whether the superior oblique tendon is lax. If it is lax, the treatment of choice would be a tightening procedure of the superior oblique such as the superior oblique tuck. Adjustable-suture strabismus surgery has reduced the incidence of repeat operations; however, adapting the procedure to the fornix incision has been difficult. The use of a scleral traction suture that retracts the conjunctiva to expose the muscle suture area has been useful for fornix surgery. The rectus muscles supply circulation to the anterior segment via the anterior ciliary vessels, which are routinely interrupted during strabismus surgery. Various procedures have recently been described to preserve the anterior ciliary vessels, and these procedures will be useful in patients who are predisposed to anterior segment ischemia. In the 1950s, inferior oblique weakening procedures were deemed dangerous and unpredictable. Recent advances in the understanding of inferior oblique physiology and fascial relationships have inspired the development of a new inferior oblique weakening strategy--the anteriorization procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Anterior Eye Segment↗
PubMed1993

Unilateral congenital ptosis: compensatory head posturing and amblyopia.

Patients with unilateral congenital ptosis often adopt chin elevation to maintain fusion. This compensatory head posturing has been considered a sign of fusion, thus indicating a low risk for amblyopia. To evaluate this sign, we reviewed the charts of 11 preverbal children with unilateral congenital ptosis who had straight eyes and appropriate compensatory head posturing to maintain binocular vision. Four additional patients with unilateral ptosis and no compensatory head posturing were tested for comparison. All patients had undergone an examination and had been tested by pattern Visual Evoked Potential (VEP) under chloral hydrate sedation. Five of the 11 patients with compensatory head posturing were found to be amblyopic, three moderately so and two severely affected. The four patients without compensatory head posturing were amblyopic. It is our hypothesis that compensatory head posturing allows peripheral fusion even when significant amblyopia is present. Additionally, the clinical sign of a compensatory head turn to maintain binocular vision does not rule out the presence of significant amblyopia.

Amblyopia↗
PubMed1992

Results of late surgery for presumed congenital cataracts.

We reviewed the results of cataract extraction and visual rehabilitation in 76 eyes of 47 infants and children with presumed congenital cataracts who were first seen after they were 10 months old. Eighteen patients underwent surgery for unilateral cataracts, including five patients with persistent hyperplastic vitreous, five with posterior lenticonus, one with a nuclear cataract, six with posterior subcapsular cataracts, and one with a lamellar cataract. Of these 18 patients, seven (39%) attained a visual acuity of 20/60 or better, one (6%) had a visual acuity of 20/100, and ten (60%) had a visual acuity of 20/200 or worse. Twenty-nine patients (62 eyes) underwent bilateral cataract extraction. The visual acuity could be measured in 22 patients (44 eyes). Visual acuity improved to 20/60 or better in 32 eyes (73%), was between 20/70 and 20/150 in 11 eyes (25%), and became worse than 20/200 in one eye (2%). Results were good in patients with persistent hyperplastic primary vitreous, posterior lenticonus, and bilateral cataracts.

Adolescent↗
PubMed1992

Binocular fusion and stereopsis associated with early surgery for monocular congenital cataracts.

Despite improved visual acuity results in infants undergoing early surgery for monocular congenital cataracts, virtually all reports indicate a lack of binocular vision and the presence of strabismus in these patients. We report herein the presence of motor fusion and stereopsis in patients who have undergone early surgery for monocular congenital cataracts. Of 13 patients with congenital cataracts who were operated on by age 9 weeks, five (38%) had essentially straight eyes and evidence of motor fusion with a minimum of 1 year of follow-up. Three (60%) of five patients demonstrated sensory fusion, two with Titmus testing and one with Randot Stereo Acuity (Stereo Optical Co Inc, Chicago, Ill) of 250 seconds of arc. We conclude that binocular fusion and stereo visual acuity are obtainable in patients with monocular congenital cataracts.

Cataract↗
PubMed1992

Third nerve palsy due to cerebral artery aneurysm in a child.

We report a case of cerebral aneurysm in a seven-year-old girl who presented with subacutely progressive third nerve palsy. To our knowledge this is the youngest reported patient with this condition. Confusion with myasthenia gravis occurred because of improvement in the patient's ptosis after intravenous edrophonium chloride. Cerebral CT revealed a hyperdense mass that was characterised on cerebral angiography as an aneurysm of the posterior communicating artery. Another occult aneurysm of the posterior cerebral artery was found at surgery. This case demonstrates that third nerve palsy due to cerebral aneurysm may affect patients at a younger age than has previously been recognised. Therefore we suggest that even young children should have aneurysm excluded by cerebral CT and angiography if they present with acquired third nerve palsy involving the pupil. In addition this case highlights the false-positive results that may occur with the edrophonium chloride test for myasthenia gravis.

Blepharoptosis↗
PubMed1991

Conjunctival retraction suture for fornix adjustable strabismus surgery.

The fornix approach to strabismus surgery is advantageous because the incision is made under the eyelid, there is no need for conjunctival sutures, it is comfortable for the patient, and there is minimal postoperative scarring. The major disadvantage of the fornix approach for the adjustable suture technique has been poor exposure to the muscle-suture apparatus and poor postoperative knot exposure. We describe herein the use of a subconjunctival retraction suture for adjustable suture surgery with the fornix approach. This suture retracts the conjunctiva, exposing the adjustable muscle-suture apparatus while simultaneously fixating the globe. A novel way of tying the noose around the pole sutures and preventing noose slippage is also presented. This technique provides excellent exposure, fixation of the globe, and complete coverage of the knot with conjunctiva after adjustment.

Conjunctiva↗
PubMed1991

Hereditary lymphedema and distichiasis.

Two patients with lymphedema-distichiasis syndrome illustrate that both Milroy's disease and late-onset hereditary lymphedema are sometimes associated with distichiasis. It is important for ophthalmologists to be aware of the lymphedema-distichiasis syndrome because of its ophthalmic manifestations and the associated systemic abnormalities that can be potentially life threatening.

Adolescent↗
PubMed1991

Effect of a modified rectus tuck on anterior ciliary artery perfusion.

Strabismus surgery results in the permanent interruption of anterior ciliary blood flow, predisposing the eye to anterior segment ischemia (ASI). A primate model was used to assess the effectiveness of a new muscle-scleral tuck for preserving anterior ciliary artery circulation. The model consisted of removing 3 rectus muscles from both eyes of 2 rhesus monkeys, then performing a tuck on the inferior rectus (IR) right eye while leaving the left IR as a control. Four weeks later, a modified tuck was performed on the virgin left IR. Fluorescein iris angiograms of both eyes were obtained, and preoperative angiograms at 5-15 sec. showed normal 360 degrees perfusion. Postoperative follow-up angiograms showed segmental superior temporal filling defects and preservation of perfusion in the distribution of the IR. Comparison of fellow eyes tucked vs control IR showed no difference in the filling pattern in both monkeys. Comparison of the same eye before and after tuck also showed essentially the same filling pattern in all 4 eyes with preservation of inferior circulation. Our conclusion is that the modified tuck preserves the anterior ciliary blood flow and may be useful as a muscle-strengthening procedure in patients predisposed to developing ASI.

Animals↗
PubMed1990

Automated perimeter for binocular suppression.

Scotomas associated with suppression amblyopia can appear or enlarge under binocular conditions. A device was designed to present an independent LED stimulus array to each eye while both eyes fixate together through beam splitters on a common background pattern. A computer-controlled field screening examination was designed to automatically plot suppression scotomas under binocular conditions.

Amblyopia↗
PubMed1989

Nucleotide-free kinesin hydrolyzes ATP with burst kinetics.

Bovine brain kinesin binds ADP tightly and contains a stoichiometric amount of ADP at its active site when isolated in the presence of free Mg2+ (Hackney, D. D. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 6314-6318). EDTA in excess of Mg2+ weakens ADP binding and nucleotide-free kinesin can be prepared by gel filtration with excess EDTA. On addition of ATP, this nucleotide-free enzyme catalyzes the rapid hydrolysis of a stoichiometric amount of ATP in a burst phase followed by much slower continued ATP hydrolysis limited by the release of ADP from the active site. This burst reaction is evident both by formation of [32P]Pi from [gamma-32P]ATP and by formation of [alpha-32P]ADP from [alpha-32P]ATP. At 1.1 nM kinesin active sites, the observed rate of the burst phase increases linearly with ATP over the 1-20 nM range yielding a bimolecular rate of net ATP binding and hydrolysis of 2.5 microM-1 s-1. The intercept at zero ATP is 0.008 s-1 which equals the ADP release rate at 0.008-0.009 s-1. This predicts a Km for ATP of approximately 3.5 nM and measurements of the dependence on ATP concentration of the steady state rate and amount of bound ADP are consistent with a Km of this magnitude.

Adenosine Triphosphatases↗
PubMed1988

Bed rest versus activity ad lib in the treatment of small hyphemas.

The management of small hyphemas remains controversial. Some authors advocate hospitalization, strict bed rest, and medical therapy with aminocaproic acid. Others are less conservative and recommend treatment on an ambulatory basis without the drug. In order to establish the overall rebleed rate for small hyphemas and to assess whether or not strict bed rest improves the prognosis, we studied 73 patients with small hyphemas occupying less than one third of the anterior chamber. Thirty-seven patients, during the first year of the study, were hospitalized and treated with strict bed rest while 36 patients, during the second year, were hospitalized but allowed to ambulate freely. The overall incidence of rebleeds was 15% (11 of 73). The incidence of rebleeds and other complications was not statistically different between the two study groups. Additionally, the final visual acuity in both groups was essentially identical. We conclude that bed rest does not improve the prognosis in cases of small hyphemas.

Atropine↗