Fabrication of infrared linear arrays of InAs planar avalanche photodiodes.

We report a, to the best of our knowledge, new device fabrication process for 128-pixel linear arrays of InAs planar avalanche photodiodes, utilizing selective area implantation of Beryllium ions into epitaxially-grown InAs wafers. The pixels exhibited uniform avalanche gain and responsivity. Room temperature responsivity values at 1550 and 2004 nm wavelengths are 0.49 ± 0.017 and 0.89 ± 0.024 A/W, respectively. Reverse dark current-voltage and avalanche gain measurements were carried out at different temperatures (from room temperature to 150 K). At 200 K at -15 V reverse bias, the pixels exhibited an avalanche gain of 22.5 ± 1.18 and dark current density of 0.68 ± 0.48 A/cm2.

Simulation of Al0.85Ga0.15As0.56Sb0.44 avalanche photodiodes.

Al0.85Ga0.15As0.56Sb0.44 is a promising avalanche material for near infrared avalanche photodiodes (APDs) because they exhibit very low excess noise factors. However electric field dependence of ionization coefficients in this material have not been reported. We report a Simple Monte Carlo model for Al0.85Ga0.15As0.56Sb0.44, which was validated using reported experimental results of capacitance-voltage, avalanche multiplication and excess noise factors from five APDs. The model was used to produce effective ionization coefficients and threshold energies between 400-1200 kV.cm-1 at room temperature, which are suitable for use with less complex APD simulation models.

Precautions in ophthalmic practice in a hospital with a major acute SARS outbreak: an experience from Hong Kong.

Many new infectious diseases in humans have been derived from animal sources in the past 20 years. Some are highly contagious and fatal. Vaccination may not be available and antiviral drugs are not effective enough. Infectious control is important in clinical medicine and in Ophthalmology. Severe acute respiratory syndrome (SARS), as an example, is a highly contagious respiratory disease that has recently been reported in Asia, North America, and Europe. Within a matter of weeks, the outbreak has evolved to become a global health threat and more than 30 countries have been afflicted with a novel Coronavirus strain (SARS-CoV) that is the aetiologic agent of SARS. The primary route of transmission of SARS appears involving close person-to-person contact through droplets. Ophthalmologists may be particularly susceptible to the infection as routine ophthalmic examinations like direct ophthalmoscopy and slit-lamp examination are usually performed in a setting that has close doctor-patient contact. Being the Ophthalmology Department of the only hospital in the world that has just gone through the largest outbreak of SARS, we would like to share our strategy, measures, and experiences of preventing contracting or spreading of SARS infection as an infection control model. SARS is one of the many viruses against which personnel will need protecting in an ophthalmic setting. The experiences attained and the measures established might also apply to other infectious conditions spreading by droplets such as the avian influenza with H5N1.

Long-term results of autogenous palmaris longus frontalis sling in children with congenital ptosis.

PURPOSE: To investigate the long-term outcome of using autogenous palmaris longus tendon (PLT) sling for correcting congenital ptosis in children. METHODS: This is an observational case series involving 15 eyelids of 14 consecutive children with congenital ptosis who underwent frontalis suspension surgery using PLT in a university teaching hospital. RESULTS: One child had bilateral ptosis and the other children had unilateral ptosis. The age of patients at the time of surgery ranged from 2 to 7 years, with an average of 4.7 years. At a mean follow-up of 92 months (range, 80-104 months), all eyelids were successfully corrected with good lid height. No recurrence or other postoperative complications were encountered except one patient who developed a small skin fold over the PLT harvest site. CONCLUSION: Long-term lid position is remarkably stable after surgical correction using PLT. PLT sling appears to be a safe and effective treatment for children with congenital ptosis requiring frontalis sling operation. It could be a good alternative to autogenous fascia lata, and further studies, to compare these two sling materials seem warranted.

Oncoprotein profiles of primary peritoneal malignant mixed müllerian tumors.

Primary peritoneal malignant mixed müllerian tumors (MMMTs) are extremely rare and highly aggressive malignancies associated with poor clinical prognoses. We present a clinicopathologic review of three cases of this rare tumor by examining expression of selected oncoproteins by immunohistochemistry. Three consecutive cases of primary peritoneal MMMT were examined by paraffin immunohistochemistry for expression of p53, p16, BCL2, CerbB2, and classical cadherins E-cadherin, P-cadherin, and N-cadherin. All three cases expressed p16, but showed less consistent expression of other markers, with one case expressing p53 and one expressing BCL2. All cases were negative for membrane expression of Cerb-B2. The three classical cadherins were expressed in two cases with one case showing only weak N- and P-cadherin expression. No difference in antigen expression was seen in the epithelial compared to sarcomatous components. We conclude that p16 may be a common tumor suppressor gene expressed in peritoneal MMMT. P53 overexpression may be of lesser frequency in peritoneal MMMT compared to MMMT from the ovary and the uterus. We did not observe any difference in antigen expression between areas of epithelial or sarcomatous differentiation, which would support a single pluripotential malignant clone in the histogenesis of these tumors.

Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study.

BACKGROUND: We investigated the temporal progression of the clinical, radiological, and virological changes in a community outbreak of severe acute respiratory syndrome (SARS). METHODS: We followed up 75 patients for 3 weeks managed with a standard treatment protocol of ribavirin and corticosteroids, and assessed the pattern of clinical disease, viral load, risk factors for poor clinical outcome, and the usefulness of virological diagnostic methods. FINDINGS: Fever and pneumonia initially improved but 64 (85%) patients developed recurrent fever after a mean of 8.9 (SD 3.1) days, 55 (73%) had watery diarrhoea after 7.5 (2.3) days, 60 (80%) had radiological worsening after 7.4 (2.2) days, and respiratory symptoms worsened in 34 (45%) after 8.6 (3.0) days. In 34 (45%) patients, improvement of initial pulmonary lesions was associated with appearance of new radiological lesions at other sites. Nine (12%) patients developed spontaneous pneumomediastinum and 15 (20%) developed acute respiratory distress syndrome (ARDS) in week 3. Quantitative reverse-transcriptase (RT) PCR of nasopharyngeal aspirates in 14 patients (four with ARDS) showed peak viral load at day 10, and at day 15 a load lower than at admission. Age and chronic hepatitis B virus infection treated with lamivudine were independent significant risk factors for progression to ARDS (p=0.001). SARS-associated coronavirus in faeces was seen on RT-PCR in 65 (97%) of 67 patients at day 14. The mean time to seroconversion was 20 days. INTERPRETATION: The consistent clinical progression, shifting radiological infiltrates, and an inverted V viral-load profile suggest that worsening in week 2 is unrelated to uncontrolled viral replication but may be related to immunopathological damage.

Efficacy of lignocaine 2% gel in chalazion surgery.

BACKGROUND/AIMS: To determine whether topical 2% lignocaine (lidocaine) gel is an effective anaesthetic agent for chalazion surgery. METHODS: In a randomised controlled clinical trial, 57 subjects aged 12 years or over requiring incision and curettage for chalazion were recruited over an 8 month period. Patients were randomised into two groups. One group received 1.5 ml of lignocaine 2% injection and the other 1.5 ml of lignocaine 2% gel topically. Standard incision and curettage was then performed. The primary outcome of interest was the total pain experienced during the entire procedure including anaesthetic administration as well as incision and curettage. The pain from the local anaesthetic administration and during incision and curettage was assessed independently using a visual analogue scale (0-100). The sum of these two scores would be the total pain score out of 200. "Fear of injection" score (0-100) was also assessed. RESULTS: There was a statistically significant difference in the mean total pain scores between the injection and the gel groups (95.6 v 57.0) (p <0.001) (alpha = 0.05) (1 - beta = 0.9394). There was a statistically significant difference in the mean scores on "pain of anaesthetic administration" (47.0 v 5.5) (p <0.000). There was no statistically significant differences in the mean scores on "fear of injection" (43.9 v 47.7) (p = 0.668) and "pain during incision and curettage" (48.28 v 51.4) (p=0.679). CONCLUSIONS: Lignocaine 2% gel is effective in chalazion surgery especially in lowering the pain caused by anaesthetic administration.

Ophthalmopathy in childhood Graves' disease.

AIMS: To study the ocular manifestations and their severity in children with Graves' disease. METHODS: All patients with Graves' disease having regular follow up in a paediatric endocrine clinic were recruited for the study. A comprehensive ophthalmic assessment including ocular motility, exophthalmometry, intraocular pressure (IOP), slit lamp, and fundus examinations was performed. RESULTS: 83 patients (72 female, 11 male) aged 16 years or below were examined. All are Chinese. Ocular symptoms occurred in 12 patients. Ocular signs of ophthalmopathy were documented in 52 patients (62.7%). Most of them presented with eyelid abnormalities such as lid oedema, lid lag, and lagophthalmos, whereas lower lid retraction was the commonest clinical sign noted (38.6%). Diffuse conjunctival injection was found in four patients (4.8%). 10 patients (12.0%) had mild proptosis of less than 3 mm. Only one patient (1.2%) had limited extraocular motility in extreme gaze. Punctate epithelial corneal erosions were reported in 11 patients (13.3%). CONCLUSIONS: This is the largest series on the ocular complications of childhood Graves' disease in the literature. Although 52 patients (62.7%) were identified with positive ocular changes, none of them had visual threatening complications or debilitating myopathy.

Topical chloramphenicol for eye infections.

Topical chloramphenicol has been widely used in the treatment and prevention of superficial eye infections due to its broad spectrum of activity and low cost. The use of this drug has decreased considerably in the United States since the first case of aplastic anaemia associated with topical chloramphenicol was reported in the 1960s. This medication, however, is still widely used in many other countries. This paper evaluates the evidence for and against the use of topical chloramphenicol in ocular diseases.

Observation of plasma focusing of a 28.5 GeV positron beam.

The observation of plasma focusing of a 28.5 GeV positron beam is reported. The plasma was formed by ionizing a nitrogen jet only 3 mm thick. Simultaneous focusing in both transverse dimensions was observed with effective focusing strengths of order tesla per micron. The minimum area of the beam spot was reduced by a factor of 2.0+/-0.3 by the plasma. The longitudinal beam envelope was measured and compared with numerical calculations.

A prospective study on ocular hypertensive and antiinflammatory response to different dosages of fluorometholone in children.

OBJECTIVE: To investigate the ocular hypertensive and antiinflammatory response to different dosages of fluorometholone (FML). DESIGN: Prospective clinical trial with randomization of fellow eyes to different postoperative treatment. PARTICIPANTS: Thirty-one consecutive children undergoing bilateral symmetrical strabismus operation. INTERVENTION: Among 31 children who received bilateral squint operations, one eye was randomized to receive topical FML six times daily (group 1), whereas the other eye received topical FML three times daily (group 2), both for 4 weeks. Intraocular pressure (IOP) and antiinflammatory response were measured serially in the postoperative period for 8 weeks. MAIN OUTCOME MEASURES: Intraocular pressure was measured on the day before surgery and on postoperative days 1, 3, 6, 13, 20, 27, 41, and 55. The antiinflammatory response was also assessed subjectively and objectively at days 6, 13, 20, and 27 after the operations. Peak IOP, net increase in IOP, and antiinflammatory responses in the two study groups were analyzed. RESULTS: Thirty-one children, age 3 to 9 years, (mean +/- standard deviation [SD], 5.52 +/- 1.81) participated in the study. Intraocular pressure increased significantly in both groups compared with the preoperative values (P < 0.001). The peak IOP ranged from 12.00 to 31.00 mmHg and 12.30 to 25.00 mmHg in groups 1 and 2, respectively. The mean peak IOP (19.00 +/- 5.06 mmHg vs. 17.13 +/- 3.32 mmHg) was significantly higher in group 1 (P < 0.001). The net increase in IOP was similar (mean +/- SD, 4.37 +/- 4.79 vs. 2.57 +/- 3.32 mmHg; P = 0.005). Ranges of the net IOP increase were -1.00 to 16.00 mmHg and -2.50 to 10.30 mmHg in groups 1 and 2, respectively. Children in group 1 reached the peak IOP earlier than those in group 2 (median, 6 vs. 13 days; P = 0.033). However, there was no significant difference in antiinflammatory response between the two groups. CONCLUSIONS: Ocular hypertension occurs in a dose-dependent manner in children treated with FML. Children in group 1 had a quicker onset and more severe ocular hypertensive response than those in group 2. It would be desirable to monitor the IOP regularly when FML is used with a high frequency and for a long duration in children.

Ocular complications of paediatric patients with nephrotic syndrome.

PURPOSE: To investigate ocular complications arising from nephrotic syndrome and/or its treatments in children. METHODS: A cross-sectional study was conducted in a teaching hospital. A total of 31 paediatric patients with nephrotic syndrome were studied. Comprehensive ophthalmic assessments on best-corrected visual acuity, intraocular pressure, slit-lamp and fundus examination were taken. Information regarding histological diagnosis of nephrotic syndrome and its treatment regimen in each patient was reviewed and analysed. RESULTS: Bilateral posterior subcapsular cataracts were detected in three of 29 patients (10.3%) who received steroid therapy. Two had normal vision while one had visual acuity reduced to 6/15 in both eyes. The age of onset of the nephrotic syndrome in these three patients was 2 years, which was significantly younger than those without cataract (5.4 +/- 3.2 years, P < 0.001). Three patients (9.7%) had isolated asymptomatic fundal findings of tortuous and dilated retinal vessels. Hypertensive retinopathy was found in one patient (3.2%). No steroid-induced glaucoma, uveitis, ocular infection, or other eye complications related to the use of steroids or other immunosuppressive agents were noted. CONCLUSIONS: Children who have nephrotic syndrome often require prolonged, intermittent high dose of systemic corticosteroid therapy. Paediatricians should be aware of the potential risk of developing steroid-related complications, especially posterior subcapsular cataract. It appears to have a higher risk when steroid therapy is used in very young patients. Early detection would help to prevent amblyopia development, particularly in the group of immature eyes.

Uterine papillary serous carcinoma presenting as distant lymph node metastasis.

BACKGROUND: Uterine papillary serous carcinomas are highly aggressive malignancies that often present with high-stage disease. We report two cases that presented initially as distant metastatic disease. One case was found incidentally at the time of axillary dissection for breast cancer and the second case in the workup of a neck mass. CASES: Clinicopathologic review of the patient material including review of routine H&E pathology and immunohistochemical studies of the patients tumors was performed. Both cases showed high-grade papillary carcinomas with psammoma bodies metastatic to lymph nodes in the axilla or neck. Sampling of the endometrium in these patients confirmed primary uterine papillary serous carcinoma. Patients were treated with adjuvant chemotherapy. CONCLUSIONS: Metastatic uterine papillary serous carcinoma presenting initially in distant sites is an unusual manisfestation of this highly aggressive tumor. This tumor should be considered in the differential diagnosis when patients present with metastatic high-grade papillary serous carcinomas and the primary site is unknown.