Wear studies on prosthetic materials using the pin-on-disc machine.

The wear of ultra high molecular weight polyethylene in combination with cobalt-chromium-molybdenum alloy was investigated by pin-on-disc experiments in which the alloy pin was loaded against the rotating polyethylene disc. In some experiments the pin was stationary, but in others it rotated about its axis. The effect of lubricant type, pin rotation, magnitude of the applied load, magnitude of the relative surface velocity, and disc storage in various environments was investigated. Wear of the polyethylene was assessed at 100 h intervals by both volumetric and gravimetric methods. Each experiment lasted 1000 h. It was concluded that of the lubricants tested bovine serum was the most suitable and that pin rotation produced more suitable polyethylene surfaces than did the stationary pin. The wear rate increased slightly with load (possibly owing to creep), was insensitive to speed, and was not affected by disc storage. The dynamic coefficient of friction increased with running tme. Results obtained by the two wear assessment methods were comparable and the reproducibility of the results was good.

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.

Independence of optokinetic nystagmus asymmetry and binocularity in infantile esotropia.

OBJECTIVE: Children with congenital esotropia, amblyopia, or early visual deprivation have persistent asymmetric monocular pursuit, as measured by optokinetic nystagmus (OKN), and favor targets moving in a temporal to nasal direction. Previous studies suggest that binocular visual development is necessary for the development of symmetric monocular OKN. We recently treated patients with congenital esotropia with unconventionally early surgery to establish good binocularity. We wished to determine if mature symmetric OKN responses could develop in patients with congenital esotropia following the acquisition of good stereopsis. METHODS: Electro-oculographic recordings documented horizontal eye movements in response to an electronic OKN stimulus. PATIENTS: The recordings of three patients with congenital esotropia that had been surgically aligned before age 20 weeks and who had achieved high-grade stereopsis with random dot and Titmus stereographic testing were studied. We compared this group of children with groups of age-matched controls, including the following: (1) three patients with congenital esotropia who underwent surgical alignment after age 6 months and who had no amblyopia but poor stereopsis; (2) three children with accommodative esotropia, good ocular alignment when wearing spectacles, and good stereopsis; and (3) three normal children. RESULTS: The normal children and those with accommodative esotropia demonstrated normal symmetrical OKN. The patients with congenital esotropia showed poor nasal to temporal OKN regardless of the degree of stereopsis or timing of surgery. CONCLUSIONS: Our results indicate that good binocularity, as measured by stereopsis, is not sufficient for the development of symmetric OKN in patients with congenital esotropia.

10-Diopter fixation test for amblyopia.

Fixation-preference testing has been useful in detecting amblyopia in children unable to give reliable visual acuities, except for children with small-angle tropias and those without manifest deviations. This study introduces a method of fixation testing that includes all children, regardless of the presence or size of the deviation. By placing a 10-diopter vertical prism over one eye, we induce a vertical deviation. Once the eyes are dissociated, fixation preference is evaluated and used to predict the presence of amblyopia. We prospectively studied fixation patterns in 98 children with either small-angle tropia or essentially straight eyes. All children with amblyopia of two lines or more showed abnormal fixation patterns, and those without amblyopia showed normal patterns. We were able to obtain fixation patterns on all children studied, including 13 infants less than 24 months of age. This test proved to be a reliable, objective method for detecting amblyopia in children with straight eyes or in children with microstrabismus of almost any age.

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.

Acquired inflammatory superior oblique tendon sheath syndrome. A clinicopathologic study.

To our knowledge, this is the first reported clinicopathologic study of a patient with acquired inflammatory Brown's syndrome. The superior oblique tendon, trochlea, and anterior superior oblique muscle were surgically removed en bloc and studied by light microscopy. Surprisingly, the entire specimen was normal, without signs of inflammation or intrasheath scarring. The only abnormal finding was found during surgery, which consisted of perisheath adhesions anterior to the trochlea. These findings indicate that the cause of acquired inflammatory Brown's syndrome may, in many cases, be from scarring around the tendon sheath rather than an intrasheath pathologic condition, as proposed by recent literature.

Reliability of fixation preference testing in diagnosing amblyopia.

We evaluated the sensitivity and specificity of standard fixation preference testing and the 10-prism diopter (PD) fixation test in 427 patients. Standard fixation preference testing showed good sensitivity and specificity for than 10 PD. Patients with small angle tropias, however, had a high false-positive rate, with 40% of nonamblyopic patients inappropriately responding with strong fixation preference. The 10-PD fixation test reduced this high false-positive rate and showed only 1.5% false-positive results. Unfortunately, this shift to equal fixation preference was also seen in some patients with amblyopia, as five of 19 patients with three or more lines difference alternated fixation with the 10-PD fixation test. Retesting disclosed that, although these children would briefly alternate to the amblyopic eye while viewing a stationary target, they would not hold fixation with the amblyopic eye through smooth pursuit. Our conclusion is that standard fixation preference testing can be used to diagnose moderate to severe amblyopia in patients with tropias greater than 10 PD. Patients with small angle deviations or straight eyes should be examined with the 10-PD fixation test, with the criterion for equal vision being the ability to hold fixation well with either eye through smooth pursuit.

High-grade stereo acuity after early surgery for congenital esotropia.

OBJECTIVE: To evaluate the effectiveness of very early surgery for establishing straight eyes and sensory fusion in patients with congenital esotropia. DESIGN: A review of consecutive patients with congenital esotropia who underwent surgery between 13 and 19 weeks of age. SETTING: A children's hospital with a teaching affiliation. PATIENTS: Seven patients who had surgery between 13 and 19 weeks of age. INTERVENTION: A bilateral medial rectus recession through a fornix incision with recessions ranging from 5.75 to 6.5 mm in infants younger than 6 months of age. MAIN OUTCOME MEASURES: Sensory fusion as measured by stereo acuity and Worth four-dot testing and motor alignment within 8 prism diopters. RESULTS: Five of the seven patients achieved essentially straight eyes with tropias of less than 8 prism diopters after one horizontal surgery. Five patients cooperated with sensory testing, and all showed stereo acuities that ranged from 400 to 40 seconds of arc. Three children had evidence of high-grade stereo acuity by showing stereopsis on random dot stereograms (Randot, Stereo Optical Co, Chicago, Ill) and by fusing the Worth four-dot test at distance and near range. Two of the patients with high-grade stereo acuity achieved a stereo acuity of 40 seconds of arc by Titmus testing; however, one had a late reduction of stereo acuity to 70 seconds of arc. CONCLUSION: Very early surgery can result in excellent motor alignment and high-grade stereo acuity in some patients with congenital esotropia.

Recording pattern visual evoked potentials under chloral hydrate sedation.

Accurate assessment of visual function in infants and preverbal children is difficult because of the dependence on vision tests that require the patient's cooperation. In an attempt to resolve this problem, we evaluated pattern visual evoked potentials (PVEPs) obtained on infants under chloral hydrate sedation. Ten patients were studied--four with unilateral amblyopia, three with suspected amblyopia, and three without amblyopia. Patients with amblyopia showed robust and reproducible responses from the sound eye, while responses from the amblyopic eye were significantly diminished (amplitude ratio less than or equal to 0.63). The PVEP responses from patients without amblyopia were large in amplitude and symmetrical between fellow eyes (amplitude ratio greater than 0.9). In two eyes with normal vision, optically fogging the patterned stimulus image substantially reduced the PVEP response, establishing a sensitivity to pattern images rather than changes in the overall luminance. We have thus determined that the PVEP can be reliably obtained under chloral hydrate sedation and that these responses, like PVEP responses taken in the awake state, reflect the presence of amblyopia and image clarity. Use of the PVEP with chloral hydrate sedation may prove clinically useful for detecting amblyopia in uncooperative infants and children.

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.

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.

Leukocoria caused by occult penetrating trauma in a child.

PURPOSE: To report a child with leukocoria caused by occult penetrating trauma. METHODS: Case report. The clinical findings and surgical repair of acquired leukocoria of the right eye in a 2-year-old boy are presented. RESULTS: In the right eye, slit-lamp examination disclosed a retrolenticular cyclitic membrane and moderately severe (3+) cells and flare anterior chamber reaction. The eye was hypotonous, and B scan showed that the membrane was associated with a retinal detachment. Surgery was performed to repair the retinal detachment and to remove the retrolenticular membrane. Two months before initial examination, the patient had been attacked by a rooster. CONCLUSION: Occult penetrating trauma should be considered in the differential diagnosis of pediatric leukocoria.

Finite element stress analysis of a class I amalgam restoration subjected to setting and thermal expansion.

Stress analyses are presented for a second mandibular premolar with a class 1 amalgam restoration. The effects of amalgam setting and thermal expansions are examined. An axisymmetric representation of the structure is used and the analyses are carried out by the finite element method. Lined and unlined restorations are compared with regard to the principal stresses set up in the composite structures and also the patterns of deformation incurred. The effects of various enamel and dentin stiffness combinations are also considered.

Finite element stress analysis of the crowns of normal and restored teeth.

Stress distributions are presented for a normal and a restored mandibular second premolar under masticatory-type forces. These were obtained using the finite element method of stress analysis applied to two-dimensional models. The effect of the relative stiffness of the materials is examined in each instance.

Binocular function and patient satisfaction after monovision induced by myopic photorefractive keratectomy.

PURPOSE: To measure binocular function and patient satisfaction with monovision induced by photorefractive keratectomy (PRK) in myopic presbyopic patients. SETTING: Refractive Department, Cleveland Clinic, Cleveland, Ohio, USA. METHODS: This study comprised 21 myopic presbyopic patients with monovision induced by PRK. Sixteen emmetropic patients who had PRK served as a control group. Monovision was induced by undercorrecting the nondominant eye by 1.25 diopters for near vision and correcting the dominant eye with emmetropia for distance vision. Monocular and binocular uncorrected Snellen visual acuities at 20 feet and 13 inches, manifest refraction, ocular dominance, stereopsis at 20 feet and 13 inches, monocular and binocular contrast sensitivities, Worth-4-Dot test at 20 feet and 1/3 of a meter, and fusional convergence amplitudes were examined in each patient. RESULTS: In the monovision group at near and distance, 20 patients (95.3%) had binocular visual acuity of 20/25 or better. No patient in the monovision group used reading glasses postoperatively; 4 of 16 patients (25.0%) in the control group used such glasses. All patients maintained binocular fusion and stereo acuity ranging from 40 to 800 seconds of arc. Mean patient satisfaction was 86% (range 40% to 100%). In the control group, 12 patients (75.0%) had binocular distance visual acuity of 20/25 or better and 11 (68.8%) had binocular near visual acuity of 20/25 or better. CONCLUSION: Monovision PRK patients had better near vision than control PRK patients, with minimal compromise in stereo acuity and overall high patient satisfaction.

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.

Congenital esotropia.

The prognosis for congenital esotropia remains guarded. Monofixation syndrome currently is the best widely reported result following surgery. The reoperation rate in congenital esotropia (including reoperations for horizontal misalignment, dissociated vertical deulation, and inferior oblique overaction) also is high, approaching 50%. The role of very early surgical intervention needs to be examined further and could result in dramatic improvement in the long-term outcomes associated with congenital esotropia.

The Monk "soft top" endoprosthesis. Clinical, biomechanical and histopathological observations.

This paper presents a prospective trial carried out using the Monk "soft top" endoprosthesis in 33 patients. Two years after operation 70 per cent of the remaining patients had pain. A biomechanical and histopathological analysis of the endoprosthesis and the surrounding tissue, obtained from a further two patients at the time of revision, is presented. It is concluded that the prosthesis has inherent design faults which result in excessive wear of the polyethylene component. The wear debris produced stimulates a prolific fibrous tissue reaction which is associated with progressive clinical deterioration.

Effect of graded anterior transposition of the inferior oblique muscle on versions and vertical deviation in primary position.

INTRODUCTION: There are various methods for weakening the inferior oblique muscle; here we describe the results of a graded anterior transposition. METHODS: Charts of 21 children (37 eyes) who underwent graded anterior transposition of the inferior oblique muscle were reviewed. Graded anterior transposition consisted of reinsertion of the inferior oblique muscle at various points along the temporal aspect of the inferior rectus muscle; the more severe the overaction, the more anterior the placement of the new insertion. In all cases the new inferior oblique insertion line was oriented parallel to the inferior rectus muscle axis. We analyzed the preoperative to postoperative change in inferior oblique overaction (versions) and vertical alignment in primary position. RESULTS: Postoperatively, 18 of 21 patients had normal versions, 2 patients had -1 underaction of 1 eye, and 1 patient had +1 overaction of both eyes. Eleven patients (15 eyes) had a preoperative vertical deviation in primary position of 4 PD or more. Three of these patients had unilateral congenital superior oblique palsy and a preoperative hypertropia of 20 PD. They underwent unilateral graded anterior transposition with a mean postoperative vertical change of 18 PD. Three patients had asymmetric primary inferior oblique overaction with true hypertropia, 1 patient had amblyopia and primary inferior oblique overaction, and 4 patients had dissociated vertical deviation associated with inferior oblique overaction. All patients had improvement after surgery, with no significant vertical deviation in primary position. CONCLUSIONS: Graded anterior transposition of the inferior oblique muscle is effective in normalizing versions and correcting vertical deviations in primary position.

Orbital extension of a frontal sinus osteoma in a thirteen-year-old girl.

Osteomas are uncommon, slow-growing, benign osteogenic neoplasms that arise most frequently in the craniofacial skeleton. (1,2) Osteoma is the most common benign tumor of the nose and paranasal sinuses and the most common neoplasm of the frontal sinus. (3-5) Paranasal sinus osteomas originate in the sinus wall, fill the lumen with well-defined mature osseous tissue, and occasionally extend into the orbit where they give rise to orbital signs and symptoms. Osteomas most commonly become symptomatic in the second to fifth decade in life, but orbital involvement has rarely been reported in patients aged 18 years and younger. (2,6-10) We report a case of a frontal sinus osteoma with orbital extension in a 13-year-old girl.