Force decomposition and toughness estimation from puncture experiments in soft solids.

Several medical applications, like drug delivery and biosensing, are critically preceded by the insertion of needles and microneedles into biological tissue. However, the mechanical process of needle insertions, especially at high velocities, is currently not fully understood. Here, we explore the insertion of hollow needles into transparent silicone samples with an insertion velocity v ranging from 0.1 mm s-1 to 2.3 m s-1 (with needle radius R = 101.5 µm, thus strain rates ∼v/R ranging from 1 s-1 to 2.3 × 104 s-1). We use a double-insertion method, where the needle is inserted and re-inserted at the same location, to estimate the fracture properties of the material. The deflection of the specimen's free surface is found to be different between insertion and re-insertion experiments for identical needle positions, which is associated with different force magnitudes between insertion/reinsertion. This aspect was previously neglected in the original double-insertion method, thus here we develop a method based on imaging, image analyses and force measurements to decompose the measured force into individual force components, including deflection force Fd, frictional and spreading force Ff + Fs, and cutting force Ft. We estimate that the toughness Γ of our silicone samples, calculated using the cutting force Ft and the crack dimensions, increases with needle velocity, and ranges within observed values in previous literature for the same material and for some soft biological materials. In addition to toughness Γ, other parameters, such as critical force Fc and mechanical work Wc, also show strain-rate dependence, suggesting tissue stiffening, due to accumulated strain energy, at high speeds.

Surgeries and Outcomes in Subluxated and Dislocated Lens in Eastern Nepal.

INTRODUCTION: Many ocular or systemic conditions can cause weakening of the zonules, leading to subluxation or complete dislocation of lens into the anterior chamber or vitreous cavity. OBJECTIVES: To evaluate the outcome of surgery in cases with subluxated and dislocated lens. MATERIALS AND METHODS: Retrospective chart review of all cases with subluxated and dislocated lens who underwent surgery in a one-year period from 2019 January to 2019 December was conducted. Demographic profile, systemic comorbidities, initial and final best corrected visual acuity (BCVA), surgical procedure were recorded along with all the intraoperative and post-operative complications. RESULTS: A total of 62 eyes of 60 patients with mean age of 50.18 ± 15.18 years (18 to 87 years) were included with the modal duration of presentation of one week. Among these, trauma was found to be the most common etiology. Subluxation was present in 55 eyes and seven eyes had dislocation. Intracapsular Cataract Extraction (ICCE) was performed in 41 while 21 underwent Extracapsular Cataract Extraction (ECCE); and surgical intervention elicited a statistically significant (p < 0.05) improvement in the visual acuity. The BCVA was statistically better among the pseudophakic patient. Most common complication encountered intraoperatively was vitreous loss and post operatively was significant corneal edema. CONCLUSION: Cataract extraction in cases with subluxated and dislocated lens due to different etiology results in the improvement in the visual acuity of the patient. In cases where ECCE cannot be performed, ICCE also results in comparable visual improvement.

Outcomes of Fungal Corneal Ulcer with Impending Perforation after Temporary Suture Tarsorrhaphy.

INTRODUCTION: This study aims to evaluate outcomes and complications of temporary suture tarsorrhaphy (TST) in cases of impending corneal ulcer perforation. MATERIALS AND METHODS: Case records of patients who underwent temporary suture tarsorrhaphy at Mechi Eye Hospital during a period of 18 months were retrospectively evaluated. All the smear positive fungal keratitis with more than 5mm infiltration involving central and/or paracentral cornea with impending corneal perforation were included. Demographic and clinical profile including - visual acuity, indication for temporary suture tarsorrhaphy, duration of signs and symptoms were noted. The outcomes were evaluated after 1 month and 3 months post tarsorrhaphy, in relation with time to epithelial healing, anatomical success rate, best corrected visual acuity, complications associated with non-healing corneal ulcer, number of temporary suture tarsorrhaphy needed and complications of TST. RESULTS: The study included 119 cases of smear positive fungal keratitis with mean age of 51.34 + 15.56 years. In this study, 56.30% of the patients developed epithelial healing at 2 - 4 weeks with mean duration of 23.24 + 12.09 days of temporary suture tarsorrhaphy. Out of 119 patients, the corneal ulcer healed in 84 patients (70.6%), whereas 35 (29.4%) did not heal. Among those with non-healing ulcers, 15 patients (12.6%) had to undergo evisceration. The anatomical success rate was 87.39% which was statistically significant (P = 0.001). Regarding visual outcome, in 62 patients (52.10%) BCVA improved by 2 or more lines, which was statistically significant (P<0.05) resulting in a functional success of 26.89%. CONCLUSION: This study concludes that temporary suture tarsorrhaphy could be a useful option for management of corneal ulcers with impending perforation in eye centers with limited resources settings and high disease burden with good anatomical and functional outcome.

Clinical Assessment and Etiological Evaluation of Optic Nerve Atrophy.

INTRODUCTION: Optic atrophy results from the disease process that cause irreversible damage to the ganglion cells and the anterior visual pathway, but may also result from posterior visual pathway involvement. The etiology causing this condition is vast and regardless of underlying cause it carries bad visual prognosis and at times may be life threatening. The study aims to assess patients with optic nerve atrophy presenting to B.P. Koirala lions centre for ophthalmic studies and identify the underlying etiology. MATERIALS AND METHODS: This is a descriptive study conducted at B.P. Koirala Lions Centre for Ophthalmic studies. All cases of optic atrophy who presented to our outpatient department from March 2016 to March 2017 were included in the study. In addition to detailed evaluation, assessment of visual acuity, color vision, contrast sensitivity and visual field were done if feasible. Other relevant investigations were conducted to establish the underlying etiological cause. RESULTS: A total of 62 patients were included in the study, with 35 patients having bilateral disease and 27 having unilateral disease accounting for 97 eyes with optic atrophy. The mean age of the affected was 40.63±17.36 years with male to female ratio of 1.2:1. The most common etiology for optic atrophy was traumatic neuropathy (n=16, 25.8%). Majority of eyes had pale disc (n=70, 72.2%) and the rest had temporal pallor (n=27, 27.8%). CONCLUSION: Traumatic optic neuropathy was the most common etiological cause of optic nerve atrophy.

Vogt-Koyanagi-Harada Disease: A Case Series in a Tertiary Eye Center.

PURPOSE: To study the clinical spectrum of Vogt-Koyanagi-Harada (VKH) disease in a tertiary eye center in Nepal. METHODS: Baseline demographic details and clinical features of six patients diagnosed as VKH in a tertiary eye center were retrospectively reviewed. Examinations included best corrected visual acuity, intraocular pressure, and slit lamp examination of anterior and posterior segments. Baseline blood investigations, chest X-ray, fundus photography, and fundus fluorescent angiography (FFA) were performed on all the patients. RESULTS: The mean age at presentation was 46 ± 8.43 years with female predominance (83.3%). The disease was complete in 16.7%, incomplete in 16.7%, and probable in 66.7% of the patients. Most cases presented in acute uveitis stage (66.7%). The most common finding in acute cases was serous retinal detachment (66.7%), followed by disc edema (58.3%), whereas in chronic cases, depigmented fundus was the most common. All cases had bilateral presentation. CONCLUSION: VKH is an important cause of bilateral loss of vision and has a good visual prognosis if aggressive treatment is initiated during the early stages.

Psychological Reactions among Staffs of a Tertiary Eye Hospital in Eastern Nepal during COVID-19 Pandemic.

INTRODUCTION: Eye examination and different procedures performed in close contact with eye and face, put medical and non medical staff of an eye hospital at higher risk for COVID-19. This causes increased psychological burden. The objective of this study was to find out depression, anxiety, stress and insomnia among Mechi Eye Hospital staff. MATERIALS AND METHODS: A web based cross-sectional study among Mechi Eye Hospital staff was done from 1st to 20th July 2020. Insomnia Severity Scale and DASS-21 were used. RESULTS: Out of 220, 190 (86.6%) participated, 63.2% were female and 61.05% were medical staff with an overall mean age of 31.1±8.4 years. Overall prevalence of anxiety, depression, insomnia and stress were 20.5%, 18.9%, 16.3% and 12.6% respectively and those were common in female with 63.9% (p value <0.02), 64.1% (p value 0.5), 58.4% (p value 0.2) and 100% (p value <0.01) respectively. Depression, anxiety and insomnia were common in the age group 30-39 years (50%, p value< 0.02), 20-29 years (56.4%, p value 0.1) and 20-29 years (70.9%, p value 0.8) respectively. Stress was common in 20-29 years and 30-39 years, 45.8% each (p value <0.03). Depression (75%, p value 0.2), anxiety (71.7%, p value 0.9) and stress (70.8%, p value 1.0) were common in medical staff. Insomnia was present in medical staff only (p value<0.01). CONCLUSION: Mechi Eye Hospital staff had greater prevalence of psychological reaction than the national baseline during the pandemic which was more common in female, younger age and medical staff.

Comparison of Ocular Biometry between Primary Open Angle Glaucoma Patients and Normal subjects.

INTRODUCTION: Glaucoma is one of the major causes of irreversible blindness. In Nepal, the most common type of Glaucoma seen is Primary Open Angle Glaucoma. There are many risk factors associated with Primary Open Angle Glaucoma. The main objective of the study was to compare ocular biometric parameters in patients diagnosed with Primary Open Angle Glaucoma and age matched controls. MATERIAL AND METHODS: This is a hospital based cross sectional study done at Mechi Eye Hospital. The study included 137 cases of Primary Open Angle Glaucoma and 75 normal individuals as control. Axial length (AL), anterior chamber depth (ACD), Keratometry 'K' value and Central Corneal Thickness (CCT) were measured. Mann - Whitney U test was used for statistical analysis. RESULTS: Mean age in Primary Open Angle Glaucoma group was (55.25 ± 10.16 years) and in the control group was (60.96 ± 10.91 years). Axial length in the Primary Open Angle Glaucoma group (23.16 ±1.19 mm) was deeper as compared to the control group (22.69 ±0.89 mm), the difference was statistically significant (p<0.001). Anterior chamber depth (ACD) was statistically deeper in the Primary Open Angle Glaucoma group (3.05 ±0.51 mm) as compared to the control group (2.86 ±0.46 mm), (p<0.01). Central corneal thickness (CCT) was thinner in the Primary Open Angle Glaucoma group (519.5 ±36.25 um) as compared to the control group (525.40 ±37.77 um) but the difference was not found to be statistically significant (p<0.19). K value in Primary Open Angle Glaucoma (7.54 ±0.41mm) was higher than age-matched controls (7.58 ± 0.33mm) but the difference was not statistically significant (p<0.79). CONCLUSION: Patients with Primary Open Angle Glaucoma had longer Axial length (AL) and deeper Anterior chamber depth (ACD) as compared to normal individuals.

Orbital Lipoma as an Uncommon Cause of Unilateral Proptosis: A Case Report.

A 36 year old male presented with a two-month history of a progressively increasing proptosis of the right eye associated with redness. MRI of brain and orbit revealed a mass in the intraconal compartment in the lateral aspect of the right orbit that had T1, T2, and FLAIR high signal intensity and was completely suppressed in the STIR image. Excisional biopsy of the mass resolved the proptosis, and histology revealed encapsulated tumor composed of lobules of mature adipocytes along with fibro collagenous septa. Thus, diagnosis of lipoma was established that has uncommon occurrence in the orbital region.

Fluid absorption by skin tissue during intradermal injections through hollow microneedles.

Hollow microneedles are an emerging technology for delivering drugs and therapeutics, such as vaccines and insulin, into the skin. Although the benefits of intradermal drug delivery have been known for decades, our understanding of fluid absorption by skin tissue has been limited due to the difficulties in imaging a highly scattering biological material such as skin. Here, we report the first real-time imaging of skin tissue at the microscale during intradermal injections through hollow microneedles, using optical coherence tomography. We show that skin tissue behaves like a deformable porous medium and absorbs fluid by locally expanding rather than rupturing to form a single fluid filled cavity. We measure the strain distribution in a cross section of the tissue to quantify local tissue deformation, and find that the amount of volumetric expansion of the tissue corresponds closely to the volume of fluid injected. Mechanically restricting tissue expansion limits fluid absorption into the tissue. Our experimental findings can provide insights to optimize the delivery of drugs into skin for different therapeutic applications, and to better model fluid flow into biological tissue.