Lasing modes in ZnO nanowires coupled to planar metals.

Semiconductor nanowire lasers can be subject to modifications of their lasing threshold resulting from a variation of their environment. A promising choice is to use metallic substrates to gain access to low-volume Surface-Plasmon-Polariton (SPP) modes. We introduce a simple, yet quantitatively precise model that can serve to describe mode competition in nanowire lasers on metallic substrates. We show that an aluminum substrate can decrease the lasing threshold for ZnO nanowire lasers while for a silver substrate, the threshold increases compared with a dielectric substrate. Generalizing from these findings, we make predictions describing the interaction between planar metals and semiconductor nanowires, which allow to guide future improvements of highly-integrated laser sources.

Laser stabilization to a cryogenic fiber ring resonator.

The frequency stability of lasers is limited by thermal noise in state-of-the-art frequency references. Further improvement requires operation at cryogenic temperature. In this context, we investigate a fiber-based ring resonator. Our system exhibits a first-order temperature-insensitive point around 3.55K, much lower than that of crystalline silicon. The observed low sensitivity with respect to vibrations (<5⋅10-11m-1s2), temperature (-22(1)⋅10-9K-2), and pressure changes (4.2(2)⋅10-11mbar-2) makes our approach promising for future precision experiments.

External levator resection for involutional ptosis: is intraoperative suture adjustment necessary for good outcomes?

Purpose: To directly compare an algorithmic external levator resection technique with the choice of intraoperative adjustment to the same technique without intraoperative adjustments. Methods: A sequential controlled prospective comparative cohort study. Two cohorts were compared: a historical control adjustment, and an experimental non-adjustment group. Fourteen patients, 25 eyelids, were in the historical cohort; and 15 patients, 23 eyelids, were in the non-adjustment cohort. Primary acquired ptosis patients who met inclusion criteria were considered. All patients underwent a standardized external levator resection technique. Intraoperative adjustments were performed only in the historical cohort. Age, follow-up time, surgical time, and marginal reflex distance 1 (MRD1) were collected. Statistical analysis was performed using the Mann-Whitney U test. Statistical significance was p < 0.05. Primary and secondary outcome measures were postoperative MRD1 minus goal MRD1, and surgical time, respectively. Results: Twenty-five historical eyelids were compared with 23 non-adjusted eyelids. The average patient age was 68.4 years (range 19-84) and 59.3 years (range 24-83) for the adjusted and non-adjusted groups. Six-month postoperative (postoperative minus goal) MRD1 was -0.1 mm (95% CI -0.3-0.1) and -0.2 mm (95% -0.5-0.0) (p = 0.33), and surgical time was 13.8 min (95% CI 12.6-15.1) and 9.5 min (95% CI 9.0-10.1) (p < 0.001) for the adjusted and non-adjusted cohort, respectively. Conclusions: The external levator resection, utilizing a standardized algorithm approach, is an efficacious technique for involutional eyelid ptosis. With sound technique, this method can be performed without the need for intraoperative adjustment, thereby saving operative time and achieving similar results.

Blepharoplasty Effect on a Described Algorithmic Approach to External Ptosis Repair: Is It Time for Unbundling?

PURPOSE: To investigate the effects of performing a previously described algorithmic levator resection for involutional ptosis with a blepharoplasty instead of through a small incision. METHODS: Eyelids with involutional ptosis and normal levator function were included in the study. An upper blepharoplasty was performed first. An external levator resection was then performed based on a described technique involving 2 mm resection of aponeurosis for 1 mm of desired lift, consistent tension on the aponeurosis between surgical cases, and standardized suture placement. RESULTS: Forty-one eyelids of 25 patients were included. Mean postoperative margin to reflex distance 1 (MRD1) was 2.98 mm, which was significantly higher than preoperative MRD1 (0.67 mm), but lower than the predetermined goal MRD1 (3.35 mm). Eight eyelids did not meet primary outcome of MRD1 within 1 mm of goal MRD1, with 5 undercorrections. There was no difference between the postoperative MRD1 compared with the same ptosis technique performed through a small incision only, but there were more intraoperative suture adjustments and fewer eyelids meeting the primary outcome when a concurrent blepharoplasty was performed. CONCLUSIONS: The addition of blepharoplasty with a previously described algorithmic approach external levator resection has an 80% success rate in achieving the primary outcome. When compared with a small-incision ptosis repair, concurrent blepharoplasty results in a less predictable outcome and an increased need for intraoperative adjustment. Performing an algorithmic technique for external levator resection with a blepharoplasty has less predictable outcomes, which raises the question of separating the procedures to improve patient care.

Biomechanics of the Levator Aponeurosis.

PURPOSE: To investigate biomechanical properties of the levator aponeurosis. METHODS: Patients undergoing external levator resection for primary or revision correction of acquired ptosis were analyzed as primary and revision groups. Immediately postoperatively, the resected segments of the levator aponeurosis were stressed by adding sequential masses to the tissue. Specimen length was recorded at each stress level. Stress-strain diagrams were used to summarize how the tissue elongated in response to the external forces, because these diagrams correct for differences in specimen size. Representative specimens were analyzed histologically. RESULTS: Twenty-two specimens from 14 patients in the primary group and 10 specimens from 7 patients in the revision group met inclusion criteria. In the primary group, the mean age was 66 years; 8 patients were women. In the revision group, the mean age was 69 years; 6 patients were women. Levator aponeurosis specimens in both the primary and revision group demonstrated proportional increases in length with increasing stress, demonstrating that the levator aponeurosis is extensile. Given the same amount of stress, the levator aponeurosis from primary specimens elongated more than revision specimens. Histologically, revision specimens exhibited increased collagen and haphazard, tangled elastin fibers. CONCLUSIONS: The levator aponeurosis obtained during surgical correction of acquired ptosis elongates in response to nominal external forces. This biomechanical property is important because the length of the aponeurosis may vary intraoperatively if variable forces are applied to the eyelid. This property might be related to connective tissue architecture and, specifically, fibrosis. Surgeons performing levator aponeurosis resection should be mindful to maintain a consistent amount of force on the levator aponeurosis when performing the resection to maximize intercase consistency.

Fuchs' endothelial corneal dystrophy: subjective grading versus objective grading based on the central-to-peripheral thickness ratio.

PURPOSE: To assess interobserver agreement between 2 corneal specialists grading Fuchs' dystrophy clinically and to determine if the corneal central-to-peripheral thickness ratio (CPTR) may be an alternative and objective metric of disease severity. DESIGN: Cross-sectional study. PARTICIPANTS: Forty-five eyes (26 subjects) with mild and moderate Fuchs' dystrophy, 73 eyes (60 subjects) with advanced Fuchs' dystrophy, and 267 eyes (142 subjects) with normal corneas. METHODS: Corneas with Fuchs' dystrophy were graded by 2 corneal specialists based on the confluence and area of guttae and the presence or absence of edema. Central corneal thickness (CCT) and peripheral corneal thickness at 4 mm from the center (PCT4) were measured by using scanning-slit pachymetry. The value of CPTR4 was the quotient of CCT and PCT4. MAIN OUTCOME MEASURES: Interobserver agreement for clinical grade and CPTR4. RESULTS: Interobserver agreement for clinical grading of Fuchs' dystrophy was moderate (κ = 0.32; 95% confidence interval, 0.19-0.45). In normal corneas, CCT was not correlated with age (r = -0.10; P = 0.28; n = 267), PCT4 decreased with age (r = -0.33; P<0.001; n = 254), and CPTR4 increased with age (r = 0.59; P<0.001; n = 254). Central corneal thickness was higher in Fuchs' dystrophy (652 ± 61 µm; n = 118) than in normal corneas (559 ± 31 µm; n = 267; P<0.001). Also, PCT4 was higher in Fuchs' dystrophy (650 ± 51 µm; n = 107) than in normal corneas (643 ± 43 µm; n = 254; P<0.001 after adjusting thickness for age). Furthermore, CPTR4 was higher in advanced Fuchs' dystrophy (1.03 ± 0.07; n = 65) than in mild and moderate Fuchs' dystrophy (0.95 ± 0.07; n = 42; age-adjusted P<0.001), which in turn was higher than in normal corneas (0.87 ± 0.05; n = 254; age-adjusted P<0.001). Finally, CPTR4 was highly correlated with clinical grade of Fuchs' dystrophy (r = 0.77; P<0.001; n = 361), was repeatable (median coefficient of variation, 1.3%), and provided excellent discrimination between Fuchs' dystrophy and normal corneas (area under the receiver operator characteristic curve, 0.93). CONCLUSIONS: Agreement between corneal specialists for the subjective and morphologic clinical grading of Fuchs' dystrophy is only moderate. The corneal CPTR is an objective, repeatable, and possibly functional, metric of severity of Fuchs' dystrophy that warrants further investigation to determine its role in monitoring disease progression and predicting the need for keratoplasty.

Photothermomechanical Nanopump: A Flow-Through Plasmonic Sensor at the Fiber Tip.

Optical fibers equipped with plasmonic flow sensors at their tips are fabricated and investigated as photothermomechanical nanopumps for the active transport of target analytes to the sensor surface. The nanopumps are prepared using a bottom-up strategy: i.e., by sequentially stacking a monolayer of a thermoresponsive polymer and a plasmonic nanohole array on an optical fiber tip. The temperature-dependent collapse and swelling of the polymer is used to create a flow-through pumping mechanism. The heat required for pumping is generated by exploiting the photothermal effect in the plasmonic nanohole array upon irradiation with laser light (405 nm). Simultaneous detection of analytes by the plasmonic sensor is achieved by monitoring changes in its optical response at longer wavelengths (∼500-800 nm). Active mass transport by pumping through the holes of the plasmonic nanohole array is visualized by particle imaging velocimetry. Finally, the performance of the photothermomechanical nanopumps is investigated for two types of analytes, namely nanoscale objects (gold nanoparticles) and molecules (11-mercaptoundecanoic acid). In the presence of the pumping mechanism, a 4-fold increase in sensitivity was observed compared to the purely photothermal effect, demonstrating the potential of the presented photothermomechanical nanopumps for sensing applications.

Lacrimal excretory system concretions: canalicular and lacrimal sac.

PURPOSE: To characterize the demographics of patients with dacryolithiasis and to compare patients who have canalicular concretions with patients who have lacrimal sac and duct dacryoliths. DESIGN: Comparative case series study and literature review. PARTICIPANTS: A total of 327 consecutive patients undergoing external dacryocystorhinostomy (DCR) between 1998 and 2008 at the University of Wisconsin-Madison. Fifteen consecutive patients with the diagnosis of canaliculitis during this period were also included. METHODS: The charts of all patients were reviewed for age, sex, laterality, duration of symptoms, history of dacryocystitis, history of lacrimal system intervention, history of smoking, examination findings, result of canalicular probing and irrigation, and histopathologic evaluation of the dacryolith or canalicular concretion. If applicable, the canaliculus involved was noted, as was any history of purulent canalicular drainage or canalicular injury. MAIN OUTCOME MEASURES: Patient demographics, duration of symptoms, history of dacryocystitis, history of smoking, presence of fungi, or Actinomyces on histopathologic evaluation. Findings were compared with prior studies reported in the literature. RESULTS: Of the 327 patients undergoing DCR, 22 (6.7%) had dacryoliths; 11 of 15 patients (73.3%) with canaliculitis had canalicular concretions. Patients with canalicular concretions were older than those with dacryoliths at DCR: 70.6 years versus 51.1 years (P = 0.003). Women made up the majority of both groups: 9 of 11 patients (81.8%) with canalicular concretions and 13 of 22 patients (59.1%) with dacryoliths at DCR (P = 0.26). The mean duration of symptoms was 20.2 months among patients with canalicular concretions and 30.5 months in patients with dacryoliths at DCR (P = 0.66); 1 of 11 patients (9.1%) with canalicular concretions smoked, compared with 9 of 21 patients (42.9%) with dacryoliths at DCR (P = 0.11). Actinomyces was isolated from 10 of 11 canalicular concretions (90.9%) and only 3 of 22 dacryoliths (13.6%) from DCR (P<0.001). In none of the 11 canalicular concretions were fungi identified, compared with 2 of 22 dacryoliths (9.1%) from DCR (P = 0.54). CONCLUSIONS: The demographics of patients with dacryoliths and the histopathology of their concretions vary with the location of the dacryolith in the lacrimal excretory system.

Role of Algorithm-Based Levator Aponeurectomy in Small-Incision External Ptosis Surgery for Involutional Ptosis.

IMPORTANCE: External surgical treatment of involutional ptosis with normal levator function is challenging owing to lack of an established algorithm. Developing an algorithm-based technique could improve postoperative results while limiting intraoperative inefficiencies. OBJECTIVE: To investigate the postoperative success of an algorithmic external levator aponeurosis resection technique for aponeurotic ptosis with good levator function. DESIGN, SETTING, AND PARTICIPANTS: This retrospective cohort study included patients with involutional ptosis and normal levator function who were treated from July 1, 2015, through November 30, 2016, at a private ophthalmic plastic surgery clinic. INTERVENTIONS: The technique involved a small incision in the eyelid crease, with dissection through the orbital septum to expose the levator aponeurosis. The leading edge of the aponeurosis was then clamped to a medical-grade spring scale to standardize the stress on the eyelid between patients. Two millimeters of aponeurosis were resected for every 1 mm of desired ptosis correction. Two sutures were then placed to connect the aponeurosis to the tarsus at predetermined locations. MAIN OUTCOMES AND MEASURES: Preoperative predicted (goal) vs actual margin reflex distance-1 (MRD1). RESULTS: Twenty-six eyelids of 15 patients (6 men and 9 women; mean [SD] age, 65 years [range, 17-84 years]) met inclusion criteria. The mean follow-up was 189 days (range, 63-343 days). The mean preoperative MRD1 was 0.44 mm (range, -0.5 to 2 mm; 95% CI, 0.18-0.70 mm) compared with the final mean MRD1 of 3.2 mm (range, 2.5-4.0 mm; 95% CI, 3.1-3.4 mm; P < .001). The mean predicted goal MRD1 was 3.4 mm (range, 2.5-4.0 mm; 95% CI, 3.2-3.5 mm). The final MRD1 of all eyelids was within 1 mm of the goal MRD1. The mean surgical time per eyelid was 14.6 minutes (range, 10.5-34.0 minutes). Twelve eyelids (46%) did not have intraoperative suture adjustments. CONCLUSIONS AND RELEVANCE: In correcting aponeurotic ptosis, a small-incision levator aponeurectomy incorporating an algorithm and consistent stress on the aponeurosis during resection achieves the goal MRD1 efficiently. The algorithm closely estimates the desired height intraoperatively such that only small intraoperative suture height revisions, if any, are needed. No intraoperative adjustments were made in 12 eyelids, necessitating future studies to determine whether any adjustments are needed. LEVEL OF EVIDENCE: 3.