Pathway to the piezoelectronic transduction logic device.

The piezoelectronic transistor (PET) has been proposed as a transduction device not subject to the voltage limits of field-effect transistors. The PET transduces voltage to stress, activating a facile insulator-metal transition, thereby achieving multigigahertz switching speeds, as predicted by modeling, at lower power than the comparable generation field effect transistor (FET). Here, the fabrication and measurement of the first physical PET devices are reported, showing both on/off switching and cycling. The results demonstrate the realization of a stress-based transduction principle, representing the early steps on a developmental pathway to PET technology with potential to contribute to the IT industry.

Superior oblique adjustable suture surgery. A rabbit model.

Adjustable suture techniques have played a limited role in superior oblique muscle surgery. In this study, one of two different adjustable suture techniques was performed on the superior oblique muscle of 12 rabbit eyes. One day after surgery, each muscle was advanced using the adjustable suture and was permanently secured to the eye. No significant difference was noted in the amount of force (P = .4603) necessary to advance the muscle with either of the procedures. Postmortem examinations performed several weeks after both procedures demonstrated that the superior oblique muscle was firmly attached to the globe in the same position where it was left following the adjustment. Adjustable suture techniques may be useful alternatives to traditional superior oblique muscle surgery.

Management of monocular congenital cataracts.

From 1971 through 1985, a diagnosis of monocular congenital cataract was made in 14 consecutive patients. All patients had a visually significant cataract that was documented at birth or within 2 months of age. All patients were followed up long enough to report distance linear recognition acuity. Excellent visual acuity (V/A) correlated with earlier surgery, earlier contact lens fit, and excellent amblyopia therapy compliance. The oldest age for attainment of excellent or good V/A was 17 weeks. Patching therapy was based on the binocular fixation pattern. The patching program consisted of 50% occlusion until the age of 2 months and gradually increased to 100% occlusion after the age of 7 months. Six patients (43%) attained excellent V/A (greater than 20/50), with three patients (21%) attaining good V/A (20/60 to 20/100) and five patients attaining poor V/A (less than 20/100).

Clinical characterization and linkage analysis of a family with congenital X-linked nystagmus and deuteranomaly.

OBJECTIVES: To identify a congenital nystagmus locus on the X chromosome and to characterize the phenotype of a 4-generation family affected with congenital nystagmus and color deficiency. METHODS: Sixty-five patients underwent an eye examination, including evaluation for the presence of nystagmus and color vision abnormalities. Affected patients and obligate carriers of the congenital nystagmus mutation were genotyped with short tandem repeat polymorphisms located on the X chromosome, and these data were subjected to linkage analysis. RESULTS: Fourteen patients were affected with a horizontal, conjugate, congenital nystagmus. All examined patients had a visual acuity of 20/60 or better. There were no associated ocular or systemic findings except that 18 of the family members had deficient red-green color vision, which was classified as deuteranomaly (the most common form of anomalous trichromacy). Five patients exhibited nystagmus and deuteranomaly. Significant linkage was demonstrated between the nystagmus phenotype and 11 markers from Xq. The maximum lod score was 4.84 (theta = 0) and was obtained with marker DXS8041. Analysis of recombinants defined the disease interval to lie between markers ATA59C05 and DXS1192 (a 5.4-centimorgan region). The proximity of this locus to the red-green opsin gene cluster (11 centimorgans more telomeric) explains the frequent coexistence of nystagmus and color vision deficiency in this family. CONCLUSIONS: We have identified the genetic locus of the X-linked congenital nystagmus gene in this family. The critical interval in this report is less than half the size of the previously described nystagmus locus. These findings will aid in identifying the gene responsible for this condition.

The gradient filter test to assess amblyopia.

A new technique, the gradient filter test, was developed for evaluating changes in the visual acuity of preverbal children undergoing treatment for amblyopia. The gradient filter test consists of a series of calibrated photographic fog filter and prism lenses. The combined prism-filter lenses are placed in front of the normal fixing eye. The greatest density (fogging value) filter that causes a switch in fixation from the amblyopic to the normal eye is noted. In both normal eyes of 20 nonamblyopic patients and the fellow (non-amblyopic) eyes of 20 amblyopic patients, visual acuity decreased as the density of the prism-filter lens increased. The gradient filter test accurately detected an improvement in visual acuity when compared with optotype measurements in eight patients undergoing occlusion therapy. The gradient filter test is a useful clinical tool that can assess changes in visual acuity in preverbal children who are being treated for amblyopia.

Factors affecting visual outcome after surgery for bilateral congenital cataracts.

The medical records of 33 patients with dense bilateral congenital cataracts were analyzed for factors affecting visual outcome. The average postoperative follow-up was 6.3 years. Of the 23 patients tested with optotypes (verbal children), 14 had visual acuities of 20/80 or better. Eight patients had binocular vision. Preoperative nystagmus, age at surgery, microphthalmos, and postoperative strabismus were not prognostically significant in visual outcome. Postoperative nystagmus was common and was not indicative of a poor visual outcome. Ocular anomalies, systemic anomalies, and postoperative complications were associated with a lower percentage of good postoperative visual acuities.

The medial rectus muscle insertion site in infantile esotropia.

The distance from the corneoscleral limbus to the insertion site of the medial rectus muscle was measured at several stages of medial rectus recession surgery in 20 patients (40 eyes) with infantile esotropia. Disinsertion of the medial rectus muscle resulted in a mean reduction in the distance from the muscle insertion site to the corneoscleral limbus of 0.903 mm (P less than .001), whereas the use of fixation forceps on the insertion to abduct the eye resulted in an additional mean reduction of 0.306 mm (P less than .01). The strabismus surgeon often uses the muscle insertion site as a reference point in determining the desired location for recessing a muscle. Our results suggest that this method of measurement is unreliable in infantile esotropia because the position of the medial rectus muscle insertion site varies considerably during surgery.

Complications after surgery for congenital and infantile cataracts.

We reviewed the records of 78 patients who underwent 128 surgical procedures for congenital or infantile cataracts before age 30 months for the type and frequency of postoperative complications. The surgeries included 92 limbal lensectomies and anterior vitrectomies, 13 pars plicata lensectomies, 20 aspirations, and three additional procedures. Complications developed after 21 of the 105 lensectomy and anterior vitrectomy procedures. Ten eyes (10%) required additional surgery for a secondary membrane, 12 eyes (11%) developed glaucoma, and one (1%) developed a retinal detachment. Patients who underwent surgery by 8 weeks of age had a significantly greater number of complications (P less than .025). Patients undergoing cataract surgery early in life should be routinely examined for possible postoperative glaucoma. The best method for reducing secondary membrane formation and some types of glaucoma appears to be an extensive removal of the lens cortex, posterior capsule, and anterior vitreous.

Myopia induced by vitreous hemorrhage.

Six of 11 children developed myopia in one eye after vitreous hemorrhage. None had retinopathy of prematurity, glaucoma, aphakia, or scleral buckling. In seven children developing vitreous hemorrhage before 1 year of age, six exhibited a myopic anisometropia in the affected eye of 1.37 to 12.00 diopters (mean, -4.7 diopters; S.D., 4.0). The degree of myopia correlated with the age of onset and duration of media opacification. In the child without myopia, the hemorrhage did not obscure the posterior pole. None of the four children whose hemorrhage occurred after 2 1/2 years of age showed myopic anisometropia (mean, +0.16 diopters; S.D., 0.24). We conclude that vitreous hemorrhage occurring in infancy is strongly associated with the development of myopia in the affected eye.

Surgical outcome after prism adaptation for esotropia with a distance-near disparity.

INTRODUCTION: Prism adaptation for patients with esotropia and a distance-near disparity is controversial. The purpose of this study was to evaluate the surgical outcome for patients who underwent prism adaptation for esotropia with a distance-near disparity and determine whether both preoperative sensory and motor fusion are necessary to determine surgical success. METHODS: The medical records of 65 prism-adapted patients with a distance-near disparity of 9 PD or more were reviewed. Prism responders had a fusion response to near Worth 4-dot test and a deviation with prisms of 8 PD or less of esotropia at near, and 5 PD or less of exotropia at distance, or both. The same criteria were used postoperatively to assess a successful surgical outcome. Patients were operated for the near angle or greater than the near angle. RESULTS: Fifty-eight of 65 patients (89%) demonstrated fusion with prisms. Twenty of 65 patients (31%) had increased deviations that were greater than their original near angle (prism builders). Eleven percent (7 of 65) had no fusion. Postoperatively, 88% (51 of 58) of all fusers, 95% (18 of 19) of prism builders, and 71% (5 of 7) of nonfusers had a good surgical outcome of 8 PD or less of esotropia at near, 5 PD or less of exotropia at distance, or both. CONCLUSIONS: Prism response for distance-near disparity esotropia is a good indicator of postoperative outcome. Responders to prism adaptation had a better surgical outcome compared with nonresponders. In particular, prism adaptation aids in detecting those patients who will benefit from larger amounts of surgical correction.

Glaucoma and ocular hypertension in pediatric patients with cataracts.

BACKGROUND: The pathogenesis of open-angle glaucoma and ocular hypertension in patients who have undergone surgical correction of their congenital cataracts remains undetermined. This study examines the prevalence of glaucoma and ocular hypertension in a population of patients who did not undergo surgical correction of their pediatric cataracts. METHODS: Fifty-eight eyes of 41 patients had cataracts before 2.5 years of age and were followed up until at least 5 years of age without operative correction. The patients were studied for the following parameters: age at diagnosis, type of cataract, etiology, bilaterality, optic nerve head cup-to-disc ratio, intraocular pressures, and reason why the patient did not undergo an operation. Glaucoma was defined as the presence of glaucomatous optic nerve head cupping with intraocular pressures of greater than 22 mm Hg. Ocular hypertension was defined as intraocular pressures greater than 22 mm Hg with no optic nerve changes. RESULTS: Nine of the 58 eyes had cataracts caused by persistent hyperplastic primary vitreous. The average age to the last intraocular pressure measurement was 19 years (range 5 to 48 years). Closed-angle glaucoma developed in two patients with persistent hyperplastic primary vitreous. Neither open-angle glaucoma nor ocular hypertension developed in any patients. CONCLUSION: Pediatric cataracts not of the persistent hyperplastic primary vitreous type were not associated with ocular hypertension or glaucoma in the absence of surgical cataract correction. In eyes with persistent hyperplastic primary vitreous cataracts, spontaneous closed-angle glaucoma developed in two of nine patients and open-angle glaucoma developed in none. Surgical cataract correction, or the aphakic state that follows such operations, may be responsible for pediatric aphakic glaucoma.

Baerveldt implant surgery in the treatment of advanced childhood glaucoma.

BACKGROUND: The efficacy of Baerveldt implant (Pharmacia & Upjohn, Inc., Kalamazoo, Mich.) surgery in the treatment of advanced childhood glaucoma is unknown. METHODS: We reviewed the results of 23 consecutive 350 mm Baerveldt implants in 20 eyes of 17 children. Results were classified as follows: (1) success; no further reoperation, no decrease in vision, and intraocular pressure at last follow-up less than 21 mm Hg with no medications; (2) qualified success; medication necessary to bring intraocular pressure to less than 21 mm Hg or complication not associated with tube failure; and (3) failure; intraocular pressure >20 mm Hg, tube failure complication or reoperation causing tube removal, phthisis, or enucleation. RESULTS: Original glaucoma types were bilateral aphakic (five), unilateral aphakic or persistent hyperplastic primary vitreous (four), primary infantile (four), juvenile (three), secondary(two), Peter syndrome (one), and Lowe syndrome (one). Patients had undergone a mean of 2.8 previous intraocular procedures. Mean preoperative intraocular pressure was 33.6 mm Hg; average number of preoperative glaucoma medications was 3.0. Mean follow-up was 19 months (range, 6 to 32 months). Eight procedures were considered successful (mean intraocular pressure 15.5 mm Hg), six were qualified successes (mean number of medications 0.8; mean intraocular pressure 16 mm Hg), and nine failed. Two eyes in the qualified success group do not have useful vision as a result of complications. Complications included retinal detachment (five), corneal decompensation (five), corneal graft rejection in five of six grafts; dislocated tubes (three), and recurrent uveitis (two). One of these eyes is phthisic and one has been enucleated. Only two of nine procedures in eyes with a history of one or no previous intraocular operations failed,whereas seven of 13 procedures in eyes with a history of three or more previous procedures failed. Only seven of 13 procedures in aphakic eyes were successes or qualified successes, whereas seven of 10 procedures in phakic eyes had good results. CONCLUSION: Baerveldt implants can produce good short-term results, especially in phakic eyes. Aphakic eyes and eyes that have undergone multiple procedures are at a much higher risk for devastating complications.

The psychosocial effects of amblyopia study.

PURPOSE: The purpose of this study was to assess the psychosocial effects of growing up with and living with amblyopia and to determine whether patients with amblyopia but without strabismus encounter psychosocial problems similar to those encountered by individuals with strabismus. METHODS: A 20-question survey focusing on medical background, education, self-image, history of amblyopia, treatment of amblyopia, and effects of amblyopia on work, school, friendships, and self-esteem was provided to patients with amblyopia but not strabismus at Saint Louis University Eye Institute and at the University of Iowa Department of Ophthalmology. In addition, patients were evaluated in terms of somatization, obsession-compulsion, interpersonal sensitivity, depression, and anxiety. Results for patients with amblyopia were compared with those of strabismic, normative, and psychopathologic groups using the Hopkins Symptom Checklist (HSC). RESULTS: Twenty-five patients with amblyopia but without strabismus or previous surgery responded. A significant number of patients felt that amblyopia interfered with school (52%) and work (48%) to some degree and were generally affected in their lifestyle (50%). Fewer were affected in their play of sports (40%) or were influenced as to their job choice (36%). Patients with amblyopia as a whole had a greater degree of somatization, obsessive-compulsive behavior, interpersonal sensitivity, depression, and anxiety than patients with strabismus and HSC control subjects. Differences between patients with amblyopia and those with strabismus were not statistically significant (P > .05), but differences between patients with amblyopia and HSC control subjects were significant (P < .05) in each category. Patients with amblyopia, however, were less symptomatic in these areas than HSC Anxious and HSC Depressed groups. CONCLUSION: Psychosocial difficulties related to amblyopia affect individuals' self-image, work, school, and friendships. Amblyopia has a significant effect on psychosocial functioning and warrants aggressive screening, prevention and treatment during the amblyogenic years.

Absent and anomalous superior oblique and superior rectus muscles.

Anomalous or absent superior oblique or superior rectus muscles have usually been reported in the context of craniofacial disorders. We report a case of absent superior oblique and superior rectus muscles in the right eye and anomalous superior oblique and superior rectus muscles in the left eye in an otherwise healthy 4-year-old boy. The possibility of anomalous or absent extraocular muscles should be considered in unusual and complex presentations of strabismus, and alternative surgical strategies should be considered preoperatively. The clinical triad of levator palpebrae superioris, superior rectus and superior oblique dysfunction should suggest embryologic abnormalities of these muscles.

Adjustable suture strabismus surgery for acquired vertical deviations.

Forty-seven patients undergoing 51 adjustable suture strabismus procedures for acquired vertical deviations were evaluated for preoperative and adjustment factors which might influence the postoperative alignment. The type of deviation, surgical procedure, previous surgery, immediate postadjustment alignment, and immediate postadjustment versions were assessed. Oblique muscle surgery in addition to an adjustable vertical rectus muscle significantly decreased the success rate (p = .0303). Other less important factors were a previous history of strabismus surgery and a moderate limitation of versions following the adjustment. A slight over- or undercorrection after adjustment did not affect the success.

The polarized three-dot test.

A new binocular sensory test was designed using polarizing filters. The polarized three-dot test (P3D) subtends the same visual angle as the Worth four-dot test (W4D). Sensory testing was performed at distance and near in 100 patients using the W4D and P3D tests. Every patient reliably completing the W4D test also completed the P3D test. Twelve patients failed to complete both tests. Fifteen patients could not reliably complete the W4D test but were able to perform the P3D, thus increasing the interpretable response rate from 73% for the W4D test to 88% for the P3D (chi square, p less than .0001). In every case but one, fusion by W4D testing was also found by the P3D test. In addition, the P3D identified 19 cases of fusion not found by W4D testing. The results suggest that the P3D test is superior to the W4D test in the clinical assessment of central and peripheral fusion.

Prevalence of glaucoma after surgery for PHPV and infantile cataracts.

The prevalence of glaucoma associated with pediatric aphakia has been reported to range from 0% to 27%. Few studies have included a significant number of patients with persistent hyperplastic primary vitreous (PHPV) cataracts. The purpose of this study was to evaluate the prevalence of glaucoma in young children undergoing surgery for PHPV and infantile cataracts. The charts of all of the patients who underwent lensectomy/vitrectomy for infantile and PHPV cataracts at the University of Iowa Hospitals and Clinics between 1975 and 1992 were reviewed. Patients with ocular abnormalities that might predispose to glaucoma and patients with less than 6 months follow up were excluded. A total of 72 patients (109 eyes) were identified: 25 patients (26 eyes) with PHPV cataracts and 47 patients (83 eyes) with infantile cataracts. Mean age at time of surgery for both groups was 3.5 months. Mean follow up was 84.5 months for those with PHPV, and 76.9 months for those with infantile cataracts. Glaucoma developed in eight (32%) of the 25 patients with PHPV and in 15 (32%) of the 47 with infantile cataracts. Mean time to onset of glaucoma was 64.6 months for those with PHPV and 47.5 months for those with infantile cataracts (P = .70). Although there was no significant difference between the prevalence of postoperative glaucoma in those with infantile and those with PHPV cataracts, the prevalence of glaucoma in these patients is high. Children with aphakia should be closely monitored for glaucoma throughout their lives.

The surgical overcorrection of intermittent exotropia.

Many strabismus surgeons recommend an initial surgical overcorrection for intermittent exotropia. Others caution against overcorrection because of possible nasal suppression and amblyopia in children, or because of possible diplopia in adults. We reviewed the records of 69 patients who were initially overcorrected following surgery for an intermittent exotropia. The mean postoperative follow-up was 3.1 years. Eight patients (11.6%) had a persistent overcorrection of 3 prism diopters or more and three patients (4.3%) had persistent diplopia. Patients with a persistent overcorrection had a greater mean age (P less than .02) and a greater mean initial overcorrection (P less than .005) compared with the patients who were not overcorrected 3 delta or more. No child lost stereoacuity or developed amblyopia due to the overcorrection.

Congenital nasolacrimal sac mucocele associated with respiratory distress.

Two newborn infants with mucoceles of the nasolacrimal sac presented with respiratory distress due to mucocele-induced nasal cavity obstruction. Nasolacrimal duct probings were performed and resulted in immediate and permanent relief of respiratory difficulties. This rare complication should be considered in the evaluation of infants with congenital nasolacrimal sac mucocele.

Upper age limit for the development of amblyopia.

The medical records of 64 patients between 1 and 11 years old with known onset of an amblyopia-inducing condition were retrospectively reviewed to determine the upper age limit for the development of amblyopia. Thirty seven patients (group 1) developed amblyopia and 27 patients (group 2) did not. The mean patient age at the onset of the amblyopia-inducing condition was 41.0 months (2.90 SE) for group 1 and 92.3 months (4.02 SE) for group 2. The difference was statistically significant (P = .0001). No patient developed amblyopia after 73 months of age. The duration of the amblyopia-inducing condition and the type of amblyopia-inducing condition were not significantly different between the two groups. The age of the patient when exposed to an amblyopia-inducing condition is the most important determinant for the development of amblyopia. Patients 6 years or older with a normal visual system have a low probability of developing amblyopia following the onset of an amblyopia-inducing condition.