Chiral terahertz wave emission from the Weyl semimetal TaAs

Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.

Study of Dosimetric Properties of Flattening Filter Free Photon Beam Passing through Cadmium Free Compensator Alloy

BACKGROUND

This study aims to investigate radiation beam geometry of Cyberknife beam and change in dosimetric characteristics of six megavoltage (6MV) flattening filter free (FFF) beam after passing through high density cadmium free compensator alloy.

MATERIAL AND METHODS

In this experimental study, changes in FFF beam dosimetric characteristics after passing through compensator alloy was measured. Transmitted intensity of FFF beam was measured in air by an ion chamber at a source to detector distance (SDD) of 800mm. Extended SDD measurement also has been performed at a distance of 1270mm to analyze scattering due to compensator. Linear attenuation coefficient (µ_eff) was measured for cadmium free compensator alloy using simple exponential attenuation model. Percentage depth doses (PDDs) have been measured by a radiation field analyzer with compensator material to observe the beam hardening and change in surface doses and depth doses.

RESULTS

Linear attenuation coefficient of compensator alloy was measured 0.042 (Standard Deviation ±0.00099) mm^-1 and it was found that there is no change with increase in collimator size. Even after increasing distance source from detector, µ_eff has no change. PDDs were found to increase with thickness of compensator. PDD from a 60mm collimator size increased by 5% and 6% at a depth of 100mm and 200mm, respectively in water. PDD also increased with collimator size less significantly. Surface dose was found to decrease with increase in compensator thickness.

CONCLUSION

Cyberknife beam has been found to be narrow beam geometry. FFF beam contains lesser scattered photons. Presence of high density compensator filters out the soft x-ray photon causes significant dosimetric changes.

Treatment outcomes and efficacy of pars plana vitrectomy-hyaloidotomy-zonulectomy-iridotomy in malignant glaucoma

AIM

To study the treatment outcomes and efficacy of pars plana vitrectomy-hyaloidotomy-zonulectomy-iridotomy in malignant glaucoma.

METHOD

A retrospective case series study of patients treated for malignant glaucoma between 2005 and 2017. The treatment included medical management as first-line in the form of cycloplegic with anti-glaucoma medications (AGM) or pars plana vitrectomy-hyaloidotomy-zonulectomy-iridotomy as second-line therapy. The resolution was defined as 'deepening of central anterior chamber' with intraocular pressure of ⩽ 21 mm Hg (minimum on two consecutive visits 1 week apart) with or without topical anti-glaucoma medications in the absence (complete success) or presence (qualified success) of systemic medications.

RESULTS

Twenty-three eyes of 22 patients were included. At the time of diagnosis of malignant glaucoma preceding surgeries were cataract surgery (13 eyes) and trabeculectomy (4 eyes). One eye each had phacotrabeculectomy, Yag capsulotomy and optical keratoplasty. Eighteen eyes were pseudophakic and two eyes were phakic. At presentation, mean intraocular pressure was 26.25 ± 14.78 mmHg which was decreased to 15.90 ± 8.12 mmHg (p < 0.0001) at final follow-up (median follow-up was 15.50 months). Fifteen (75%) eyes had complete success, 3 (15%) eyes had qualified success and 2 (10%) eyes had treatment failure. Of 15 eyes that had achieved complete success, 3 eyes had undergone medical management and 12 eyes undergone second-line procedure. There was no significant difference in visual acuity or number of anti-glaucoma medication at presentation and final follow-up (p > 0.05).

CONCLUSIONS

Though malignant glaucoma is highly refractory to treatment, appropriate management in the form of medical or vitrectomy-hyaloidotomy-zonulectomy-iridotomy could achieve 90% success in this series.

Intraocular pressure reduction in a spectrum of angle closure disease following cataract extraction

Purpose:

The purpose is to study the effect of cataract extraction on intraocular pressure (IOP) in patients with angle closure disease (ACD).

Methods:

In this retrospective study, patients with ACD including medically uncontrolled and advanced primary angle closure glaucoma (PACG) who underwent only cataract surgery were included. The IOP trend was analyzed at postoperative day 1, day 7, 1 month, 3 months, 6 months, 1 year, and final follow-up along with requirement of antiglaucoma medication (AGM)/surgery.

Results:

A total of 110 eyes of 79 patients [primary angle closure suspect (PACS): 21, PAC: 34, PACG: 55 eyes] were analyzed. Of these patients, 31 eyes had advanced PACG and 20 eyes had medically uncontrolled glaucoma. Best-corrected visual acuity >6/12 was seen in 51 eyes at baseline and 87 eyes at final follow-up. After cataract surgery alone, there was significant reduction (median) in IOP [19.1 ± 18.00% (18.8) in PACS (P < 0.01), 8.55 ± 17.9% (10) in PAC (P = 0.04), 22.82 ± 15.45%(14.3) in PACG (P < 0.01), 18.27 ± 15.99% (14.5) in advanced PACG (P = 0.01) and 36.56 ± 14.58% (28.57) in medically uncontrolled glaucoma (P < 0.01)] and AGM [51.85% (1) in PAC, 32.35% (2) in PACG, 17.71% (2) in advanced PACG, and 40.74% (1.5) in medically uncontrolled PACD] at median follow-up of 1, 2.5, 1, 1.3, and 1 year. Eleven PACG patients, who were on systemic medication preoperatively, were off systemic therapy at final follow-up, while six other PACG eyes (10.9%) required glaucoma surgery.

Conclusion:

Cataract surgery leads to significant drop in IOP across the spectrum of ACD with visually significant cataract. Cataract surgery may be considered initially for IOP control even in advanced or medically uncontrolled PACG followed by glaucoma surgery later if required.

Long-term outcome of low-cost glaucoma drainage device (Aurolab aqueous drainage implant) compared with Ahmed glaucoma valve

Purpose

To compare the long-term outcome of Aurolab aqueous drainage device (AADI) and Ahmed glaucoma valve (AGV).

Method

Retrospective analysis of patients with refractory glaucoma who underwent AGV (AGV-FP7) and AADI (AADI Model 350) implantation. The outcome measures were intraocular pressure (IOP), requirement of antiglaucoma medications (AGMs) and re-surgery for IOP control. The postoperative complications were classified as early (≤3 months), intermediate (>3 months to ≤1 year) or late (>1 year).

Results

173 patients (189 eyes) underwent AGV implantation (AGV Group) while 201 patients (206 eyes) underwent AADI implantation (AADI group). The IOP in AADI group was significantly lower than AGV group at all time points till 2 years and comparable at 3 years. AADI group had significantly higher number of AGM in preoperative period and significantly lower number in postoperative period till 3 years compared with AGV group. AADI group had more hypotony-related complications but statistically insignificant (p = 0.07). The surgical interventions were significantly higher in AGV (n = 18) compared with AADI group (n = 5) in late postoperative period (p = 0.01). At 3 years, overall success was seen in 58.18% in AGV and 73.08% in AADI group (p = 0.15). Complete success was seen in 7.27% patients in AGV and 25.00% patients in AADI group (p = 0.02).

Conclusion

Both AADI and AGV implant had comparable mean IOP at 3 years with lesser requirement of AGM in the AADI group. Both procedures appear to be safe with slight preponderance of hypotony-related complications in AADI group.

Iridocorneal endothelial syndrome: Evaluation of patient demographics and endothelial morphology by in vivo confocal microscopy in an Indian cohort

Purpose:

To evaluate the patient demographics and morphological characteristics of corneal endothelium by in vivo confocal microscopy (IVCM), in patients with Iridocorneal Endothelial (ICE) Syndrome.

Methods:

In this retrospective observational series, IVCM acquired endothelial images of patients with ICE syndrome were evaluated. ‘ICE cells’ morphology was classified as “−” or “+” if they were larger or smaller than contralateral normal endothelium. It was correlated with patient demographics and clinical manifestations.

Results:

IVCM was performed on 41 eyes of 21 patients, with 13 males (62%) and 8 females (38%). The disease was unilateral in 19 (90.5%) and bilateral but asymmetric in two (9.5%) patients. Total ICE was seen in 91% eyes. Eighty percent patients (12 out of 15) with ICE—cells were males while 83.3% (5 out of 6) patients with ICE + cells were females. Mean age of patients with ICE- cell type and ICE + cell type was 45.8 ± 17.8 years and 40.3 ± 9.2 years respectively (P = 0.02). Both ICE – and ICE + eyes had similar incidence (33.3%) of corneal edema. ICE + eyes had more severe (grades 2/3) glaucoma (n = 5/6 eyes, 83.3%) compared to ICE – eyes (n = 8/15 eyes, 53.3%).

Conclusion:

A male preponderance, predilection of ICE – and + cell variants for male and female gender respectively, lack of association of the endothelial cell morphology with corneal edema, and apparent association of ICE + phenotype with more severe glaucoma occurring at a relatively younger age, are some novel findings of the present study. In the clinical setting correlation of patient demographics with these IVCM findings may help in better long-term prognostication of eyes with ICE syndrome.

Phacolytic glaucoma: A nearly forgotten entity

PURPOSE

To report a case of phacolytic glaucoma with rupture of anterior lens capsule in a case of hypermature cataract.

METHODS

Case report and literature review.

RESULTS

An 80-year-old woman presented with cloudiness and pain in the left eye for 1 day. The patient had visual acuity limited to perception of light with raised intraocular pressure of 70 mm Hg. Careful slit-lamp evaluation revealed corneal epithelial edema in superior quadrant and a deep and turbid anterior chamber. Ultrasound biomicroscopy confirmed the presence of a deep anterior chamber, a hypermature cataractous nucleus with lax capsular bag, and ruptured anterior lens capsule. The patient underwent extracapsular cataract extraction. Cytological examination of the lenticular fluid revealed the presence of lens protein-laden macrophages. Post-operatively, the patient had best-corrected visual acuity of 6/60 with advanced glaucomatous optic neuropathy.

CONCLUSION

Phacolytic glaucoma can present with a cloudy cornea and a turbid anterior chamber mimicking endophthalmitis. Careful examination and ancillary investigations including ultrasound biomicroscopy was helpful in making an accurate diagnosis.

Perioperative Propranolol: A Useful Adjunct for Glaucoma Surgery in Sturge-Weber Syndrome

PURPOSE

Ocular manifestations of Sturge-Weber syndrome (SWS) include choroidal hemangioma and glaucoma. Intraocular pressure (IOP) reduction in these patients commonly is associated with sight-threatening choroidal effusions. Oral propranolol is the standard of care for infantile cutaneous hemangioma, but its role in choroidal hemangioma largely is unexplored. We studied the role of perioperative oral propranolol during glaucoma surgery in SWS.

DESIGN

Prospective, nonrandomized case series with historical controls.

PARTICIPANTS

Fourteen eyes of 12 patients with SWS scheduled for glaucoma surgery were included, and the outcomes were compared with those of historical controls without propranolol use (15 eyes of 14 patients).

METHODS

Patients in the prospective cohort received oral propranolol 2 mg/kg of body weight daily in 2 divided doses 1 week before surgery and continued for 6 weeks after surgery. There was no modification (e.g., posterior sclerotomy) in the existing surgical technique. The historical control group was identified from records and SWS diagnosis validated by chart review.

MAIN OUTCOME MEASURES

The incidence and extent of postoperative choroidal effusion, additional procedures required compared with the control group, and adverse effects of the drug in the prospective cohort.

RESULTS

Average follow-up was 25.7±12.1 months (95% confidence interval, 19.3-32.1 months). The intraocular pressure reduced from 25.2±9.7 mmHg at presentation to 16.25±6.2 mmHg, 14.6±4.5 mmHg, 13.7±6.4 mmHg, and 16.5±8.0 mmHg at 1 week, 1 month, 3 months, and 1 year after surgery, respectively. In the perioperative propranolol group, no patient demonstrated sight-threatening choroidal effusion within the vascular arcades. In the 2 patients with bilateral disease, both eyes of each patient showed peripheral choroidal effusion, which settled with medical treatment. Surgery was a repeat procedure in 3 of the 4 eyes. There were no adverse effects of propranolol in any patient. In the control group, 5 of 12 eyes showed peripheral choroidal effusion after primary glaucoma surgery, whereas 5 of 6 eyes that underwent repeat surgery failed demonstrated sight-threatening choroidal effusion requiring surgical intervention.

CONCLUSIONS

Oral propranolol seems to be an effective method to minimize the development of sight-threatening choroidal effusion after glaucoma surgery in SWS.

Predictors of visual impairment in primary and secondary glaucoma in a tertiary institute in North India

AIM

To find out and compare various predictors of glaucoma-related visual impairments in primary and secondary glaucoma.

METHODS

A prospective observational study of patients, who were above 30 years of age. They were diagnosed as primary/secondary glaucoma with visual acuity <20/200 Snellen's/visual field showing less than 20° isopter in at least one eye, with a minimum follow-up of one year at a tertiary center. Patients were classified into advanced and end-stage glaucoma and outcome was assessed according to visual acuity and visual fields to see predictors of visual impairments.

RESULTS

There were 169 (99 primary/70 secondary) glaucoma patients with mean age of 62.67 ± 11.9 and 54.65 ± 15.26 years, respectively. Trauma (21.4%), complicated cataract surgery (15.7%), and silicon oil tamponade (14.3%) were common causes of secondary glaucoma. There was significant delay in diagnosis in primary compared to secondary glaucoma (57.57% vs 32.85%) and non-compliance was significantly higher in primary glaucoma (34.3% vs 17.1%, p = 0.01). In univariate analysis, literacy, income status, locality, and delayed or missed diagnosis were found to be significant (p < 0.05) according to visual acuity criteria. Out of the 33 patients who had undergone glaucoma filtration surgery, 18 (54.5%) were in the end-stage group. While 105 (77.2%) of 136 patients who were not subjected to any glaucoma filtration surgery reached end-stage glaucoma as per visual fields criteria (p = 0.011).

CONCLUSION

Lack of awareness, delayed diagnosis, low literacy, and income were associated with poor visual outcome. Patients who underwent glaucoma filtration surgery had significantly better visual outcome in comparison to patients managed medically.

A prospective randomized controlled study of Aurolab aqueous drainage implant versus Ahmed glaucoma valve in refractory glaucoma: A pilot study

PURPOSE

To study the efficacy of the Aurolab aqueous drainage implant (AADI) compared to Ahmed glaucoma valve (AGV) in patients with refractory glaucoma.

METHODS

This was a prospective, randomized controlled trial. Thirty-eight adult patients (>18 years) scheduled for a glaucoma drainage device (GDD) were randomized into two groups to receive either AGV or AADI. Primary outcome measures: intraocular pressure (IOP) control and requirement of antiglaucoma medications; secondary outcome measures: final best correct visual acuity (log MAR), visual field (Visual field index [VFI], mean deviation [MD] and pattern standard deviation [PSD]), postoperative complications and additional interventions. Complete success was defined as IOP ≥5-≤18 mmHg without antiglaucoma medications/laser/additional glaucoma surgery or any vision threatening complications.

RESULTS

There were 19 age and sex-matched patients in each group. Both groups had comparable IOP before surgery (P = 0.61). The AGV group had significantly lower IOP compared to AADI group (7.05 ± 4.22 mmHg vs 17.90 ± 10.32 mmHg, P = <0.001) at 1 week. The mean postoperative IOP at 6 months was not significantly different in the two groups (13.3 ± 4.2 and 11.4 ± 6.8 mmHg respectively; P = 0.48). At 6 months, complete success rate according to antiglaucoma medication criteria was 78.94% in AADI and 47.36% in AGV groups. AGV group required 1.83 times more number of topical medications than AADI group. There was no significant difference in early (P = 0.75) and late (P = 0.71) postoperative complications in the AADI and AGV group. The complete success rate was higher in AADI group (68.42%) than AGV group (26.31%) (P = 0.034).

CONCLUSION

In this study, AADI appears to have comparable efficacy versus AGV implant with higher complete success rate at 6 months follow-up.