Photonic Crystal Fiber-Based Reconfigurable Biosensor Using Phase Change Material.

A reconfigurable biosensor with different spectral sensitivities could provide new opportunities to increase the label-free selectivity and sensitivity for biomolecules. Here, we propose and numerically demonstrate a phase change chalcogenide material (Ge2 Sb2 Te5)-based photonic crystal fiber (PCF) sensor for tunable and enhanced refractive index sensing at near infrared (NIR) wavelengths. In order to achieve this, we integrate a thin hybrid sensing layer of Au/Ge2 Sb2 Te5 with D-shaped PCF. By switching the structural phase of Ge2 Sb2 Te5 from amorphous to crystalline, we realize tunable and enhanced refractive index sensing with a large figure of merit (FOM) for the sensing range from 1.35 to 1.40, which covers most known analytes such as proteins, cancer cells, glucose and viruses or DNA/RNA. The obtained average bulk refractive index sensitivity is 17,600 nm/RIU and 8,000 nm/RIU for crystalline and amorphous phase, respectively. The observed large tunable differential response of the proposed sensor offers a promising opportunity to design an assay for the selective detection of higher and lower molecular weight biomolecules through future artificial intelligence-based sensing.

Controllable pulse width of bright similaritons in a tapered graded index diffraction decreasing waveguide.

We obtain the bright similariton solutions for generalized inhomogeneous nonlinear Schrödinger equation (GINLSE) which governs the pulse propagation in a tapered graded index diffraction decreasing waveguide (DDW). The exact solutions have been worked out by employing similarity transformations which involve the mapping of the GINLSE to standard NLSE for the certain conditions of the parameters. By making use of the exact analytical solutions, we have investigated the dynamical behavior of optical similariton pairs and have suggested the methods to control them as they propagate through DDW. Moreover, pulse width of similariton is controlled through various profiles. These results are helpful to understand the similaritons in DDW and can be potentially useful for future experiments in optical communications which involve optical amplifiers and long-haul telecommunication networks.

Surgical strategies to improve visual outcomes in corneal transplantation.

The recent years have brought about a sea change in the field of corneal transplantation with penetrating keratoplasty being phased to newer lamellar keratoplasty techniques for a variety of corneal pathology. Improved and innovative surgical techniques have allowed selective replacement of diseased host corneal layers with pre-prepared healthy donor corneal lamellae for anterior corneal disorders such as keratoconus and posterior corneal disorders such as Fuch's corneal endothelial dystrophy. The results of lamellar techniques are encouraging, with rapid visual rehabilitation and vastly reduced risk of immune-mediated transplant rejection. The techniques of deep anterior lamellar keratoplasty and Descemet's stripping endothelial keratoplasty (DSAEK) continue to evolve with advent of femtosecond lasers and newer concepts such as pre-conditioned donor corneas for Microthin DSAEK and Descemet's membrane keratoplasty. This review describes the current developments in lamellar keratoplasty, including the futuristic approach using cell therapy to restore vision in corneal blindness.

Antioxidant Effect of Tinospora cordifolia Extract in Alloxan-induced Diabetic Rats.

Many plants are claimed to possess antidiabetic and antioxidant activity. In practice, it is being increasingly recognized to be an alternative approach to modern medicine. This study assess the antioxidant capacity of Tinospora cordifolia stem methanol extract in daily oral administration of 500 mg/kg of body weight for 40 days in alloxan induced diabetic rats. The erythrocytes membrane lipid peroxide and catalase activity was increased where as the activities of superoxide dismutase, glutathione peroxidase were found to be decreased significantly (P<0.01) in alloxan-induced diabetic rats. The levels of lipid peroxide in liver of diabetic rats increased significantly (P<0.01) and catalase, superoxide dismutase, glutathione peroxidase in liver was significantly decreased in alloxan-induced diabetic rats, when compared to normal rats. After treatment of methanol Tinospora cordifolia stem extract brings back to normal (P<0.01) in the erythrocytes membrane and liver cell enzymes activities.

Pupil perimetry in the diagnosis of functional visual field loss.

The diagnosis of functional visual loss-reduced visual performance in the absence of an organic cause-is usually made by exclusion. We conducted a pilot study to evaluate pupil perimetry in three patients (aged 14, 43 and 50) with visual field loss presumed to be functional on clinical grounds and having no cause identified by visual electrophysiology or magnetic resonance imaging. A modified automated perimeter was used to examine visual and pupil responses to a light stimulus (size 1.7 degrees ) presented at five locations in the visual field (fixation and in each of the four quadrants). In each patient, the pupil responses were normal in those test quadrants which showed apparent visual field loss. Pupil perimetry provides objective evidence for a diagnosis of functional visual field loss in selected patients and may circumvent the need for other investigations.

Partial coherence laser interferometry vs conventional ultrasound biometry in intraocular lens power calculations.

AIMS: The purpose of the study was to compare optical biometry based on partial coherence laser interferometry (PCLI) principle to conventional ultrasound biometry in the accuracy of intraocular lens (IOL) power calculations. The role of partial coherence laser interferometry in pseudophakic axial length measurement was analysed in the study. METHODS: In a prospective randomised clinical trial, 100 patients undergoing phacoemulsification cataract surgery were randomised to undergo biometry by either partial coherence laser interferometry (IOL Master) or the applanation ultrasound technique. The IOL material, design and the IOL formula were standardized. The mean error and mean absolute error were calculated and compared using paired t-tests. RESULTS: One hundred patients were included in this prospective randomised trial, of whom 50 patients underwent optical biometry and 50 patients had biometry by applanation ultrasound. The mean age of patients in the PCLI group was 67 +/- 6 yrs as compared to 71 +/- 8 yrs in the ultrasound group (P > 0.05). The preoperative mean axial length was 23.47 +/- 1.1 mm in the PCLI group (range 20-27.6 mm) and 23.43 +/- 1.2 mm in the ultrasound group with a range of 20.1-27 mm (P > 0.05). The mean absolute error (MAE) in the PCLI group was 0.52 +/- 0.32 D (upper and lower 95% CI 0.62 and 0.42 respectively). The MAE in the ultrasound group was 0.62 +/- 0.4 D (upper and lower CI 0.73 and 0.50 D respectively). Eighty-seven per cent of patients were within +/- 1 D in the PCLI group as compared to 80% in the ultrasound group (P = 0.24). The MAE of axial length difference with optical biometry was 0.13 mm +/- 0.13 SD (range -0.42 to 0.78 mm) in the PCLI group and 0.19 +/- 0.13 mm in the ultrasound group. There was a mean shortening of the eye length in the PCLI group postoperatively. Optical biometry improved the post op refraction by 16% on retrospective IOL power calculations. Eight per cent failed biometry with IOL Master (dense cataracts (4%) and fixation instability due to macular degeneration (4%)). CONCLUSION: The non contact optical biometry using the partial coherence laser interferometry principle improves the predictive value for postoperative refraction and is a reliable tool in the measurement of intraocular distances in pseudophakic eyes.

Focal myositis of the neck with idiopathic orbital myositis.

Focal myositis (of Heffner) in the right trapezius and paraspinal muscles accompanied by a pseudotumour of the left orbit has not been reported previously. The clinical, pathological and radiological features of these unusual benign pseudotumours of the head and neck are discussed. Computerized tomography (CT) scan of the neck and orbital ultrasound were suggestive of an inflammatory process without an abscess formation. This was followed by fine needle aspiration cytology (FNAC), which confirmed the diagnosis. The patient was treated with intravenous steroids and antibiotics, that led to complete resolution of symptoms, and there was no recurrence at six months follow-up. This report highlights the importance of imaging in inflammatory neck swellings.