Influence of tomographic and biomechanical corneal indexes on myopic refractive surgery indications: A multicenter study

2021 ◽  
pp. 112067212110547
Author(s):  
Francesc Duch ◽  
Ignacio López-Marín ◽  
Federico Alonso-Aliste ◽  
Mariano Hernández-Barahona-Campos ◽  
Santiago C Manito ◽  
...  
Keyword(s):  
Multicenter Study ◽  
Refractive Surgery ◽  
Ablation Depth ◽  
Corneal Biomechanics ◽  
Photorefractive Keratectomy ◽  
Cross Sectional ◽  
Biomechanical Parameters ◽  
Tomographic Data ◽  
Corneal Tomography

Purpose To evaluate the influence of corneal tomographic and biomechanical indexes on the refractive technique indication. Methods A total of 251 eyes from 251 patients interested in refractive surgery were enrolled in this cross-sectional and multicenter study. Previous to the surgeon decision, a preoperative protocol was performed by refractive optometrists, containing four sections: refraction, biometry, corneal tomography and biomechanics. The refractive surgeons made a first decision based only on refraction, biometric and tomographic information. Biomechanical indexes were revealed, and refractive surgeons made a second indication. Additionally, for Laser-Assisted in-situ Keratomileusis cases, the percent tissue altered were calculated. Possible indications were no refractive surgery, photorefractive keratectomy, Laser-Assisted in-situ Keratomileusis or intraocular Collamer lens. Results After the first surgery indication, the distribution was photorefractive keratectomy (47.4%), Laser-Assisted in-situ Keratomileusis (48.2%) while intraocular Collamer lens achieved 2.8%. This proportion changed significantly after the second indication regarding corneal biomechanics and photorefractive keratectomy and Laser-Assisted in-situ Keratomileusis decreased by 24% while intraocular Collamer lens increased 19%. A total of 69 eyes changed the indication (27.5%) and 182 eyes (72.5%) remained unchanged. All indications changes were from photorefractive keratectomy or Laser-Assisted in-situ Keratomileusis to intraocular Collamer lens or no surgery. Indication changes to intraocular Collamer lens were observed in 49 eyes (71%). Tomographic, biomechanical indexes, ablation depth and percent tissue altered achieved statistically significant differences between eyes without and with indication changes (all, P < .01). Conclusion New corneal biomechanical indexes could change the indication decision regarding biometric and tomographic data alone. Intraocular Collamer len was the preferred indication for eyes at risk of ectasia or with subclinical keratoconus due to corneal biomechanical parameters.

scholarly journals The Incidence of Central Serous Chorioretinopathy after Photorefractive Keratectomy and Laser In Situ Keratomileusis

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Majid Moshirfar ◽  
Maylon Hsu ◽  
Julia Schulman ◽  
Joseph Armenia ◽  
Shameema Sikder ◽  
...  
Keyword(s):  
Central Serous Chorioretinopathy ◽  
Refractive Surgery ◽  
Chart Review ◽  
Previous History ◽  
Laser In Situ Keratomileusis ◽  
Photorefractive Keratectomy ◽  
Causal Association ◽  
History Of ◽  
Low Incidence

Purpose. To assess the incidence of central serous chorioretinopathy (CSCR) following laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).Methods. A chart review was performed to identify all patients with CSCR and a previous history of LASIK or PRK.Results. Over the 6-year study period, 1 of 4,876 eyes which had LASIK or PRK at the Moran Eye Center was diagnosed with CSCR. One other patient was referred from an outside center, developed CSCR symptoms one month after PRK. Both patients were managed conservatively with a final visual acuity of 20/20 or better. All other patients presented 4 or more years after refractive surgery.Conclusions. We report the first 2 CSCR cases developing within one month after PRK. The low incidence argues against a causal association. Topical corticosteroids or anxiety may elevate cortisol levels presenting therapeutic challenges for the management of CSCR after PRK or LASIK.

scholarly journals Laser Assisted In Situ Keratomileusis (Lasik) Versus Trans Epithelial Photorefractive Keratectomy (T-Prk) In Astigmatic Patients

2021 ◽  
Vol 38 (1) ◽  
Author(s):  
Mahar Safdar Ali Qasim ◽  
Muhammad Suhail Sarwar ◽  
Maher Mustansar Ali Qasim
Keyword(s):  
Refractive Surgery ◽  
Corneal Thickness ◽  
Photorefractive Keratectomy ◽  
P Value ◽  
Cylinder Axis ◽  
P Values ◽  
Parametric Data ◽  
Quasi Experimental ◽  
The Difference

Purpose:  To compare the results of LASIK versus Trans Epithelial Photorefractive Keratectomy (T-PRK) in correcting astigmatic refractive error. Study Design:  Quasi experimental study. Place and Duration of Study:  Lahore Medicare Hospital from January to October 2018. Methods:  One hundred and twenty six eyes of 63 patients, age 18 to 35 years, either gender, presenting with astigmatism were enrolled in this study. Myopes with spherical equivalent (SE) ? -13.0 diopter sphere (DS), hyperopes with SE ? +5.0 DS and astigmatism ? 1.5 D with visual acuity better or equal to 0.3 LogMAR were included. Astigmatic eyes with < 1.5D and with any other ocular pathology were excluded. Refractive status was assessed by Canon Autorefractor and Heine Retinoscope. Average reading of both methods was taken. Patients were divided into two groups (31: LASIK; 32: trans-PRK) by spin of a coin method. Refractive surgery was done in both groups. Data was analyzed by SPSS 20. Normality of quantitative data was checked by Shapiro Wilk test. Mann Whitney-U test was used for non-parametric data. P-value ? 0.05 was taken as significant. Results:  Mean age of the patients was 25.83 ± 3.09 years. The difference in residual sphere, amount of cylinder, axis of cylinder and CCT (central corneal thickness) after surgery in two groups was insignificant. P values were as follows; for sphere p = 0.85, amount of cylinder p = 0.22, axis of cylinder P = 0.46 and CCT p = 0.07. Conclusion:  Both techniques are equally good in correcting astigmatism (p = 0.22). LASIK or T?PRK can be done alternatively in patients with astigmatism. Key Words:  LASIK, Trans epithelial PRK, Astigmatism.

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus – Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year

2021 ◽  
Author(s):  
Sonia Razafimino ◽  
Elias Flockerzi ◽  
Elena Zemova ◽  
Christian Munteanu ◽  
Berthold Seitz
Keyword(s):  
Thyroid Dysfunction ◽  
Resistance Factor ◽  
Ocular Response Analyzer ◽  
Longitudinal Analyses ◽  
Longitudinal Assessment ◽  
Corneal Resistance Factor ◽  
Cross Sectional ◽  
Gender And Age ◽  
Biomechanical Parameters ◽  
Corneal Tomography

Abstract Background and Purpose The etiology of keratoconus (KC) is probably multifactorial but remains essentially unknown. Previous scientific observations have suggested that hypothyroidism might play a role in the development and progression of KC. The purpose of this study was to analyze the tomographic and biomechanical parameters in KC patients with or without hypothyroidism. Methods Twenty-eight patients with KC and hypothyroidism (HT group) and fifty-six KC patients without thyroid dysfunction (WHT group) with matching gender and age were analyzed. Mean age was 40.3 years (range 14 – 57) in the HT group and 40.3 years (range 14 – 57) in the WHT group. Routine ophthalmic examinations consisted of corneal tomography and biomechanical parameters. We extracted the following KC parameters from the Pentacam (Pentacam HR, Oculus, Wetzlar, Germany): Keratoconus Index (KI), maximum keratometry (Kmax), astigmatism, and thinnest pachymetry (TP). From the ocular response analyzer (ORA, Reichert Ophthalmic Instruments, Depew, NY, USA), we extracted corneal hysteresis (CH), corneal resistance factor (CRF), and KC match index (KMI). Results The comparison of the tomographic and biomechanical values from cross-sectional and longitudinal analyses showed no significant differences between the HT and WHT groups. Conclusion The severity of KC based on tomographical and biomechanical parameters does not seem to depend on the presence of hypothyroidism.

scholarly journals Prevalence of Keratoconus in a Refractive Surgery Population

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Abdulrahman Mohammed Al-Amri
Keyword(s):  
Saudi Arabia ◽  
Retrospective Study ◽  
High Altitude ◽  
High Myopia ◽  
Refractive Surgery ◽  
Private Hospital ◽  
Saudi Arabian ◽  
Common Reason ◽  
Cross Sectional ◽  
Corneal Tomography

Objective. This study examined the prevalence of keratoconus among patients who were interested in undergoing refractive surgery. Corneal tomography measurements were used to help detect keratoconus.Methods. Adult subjects who presented to the private hospital Cataract and Refractive Surgery Unit (Abha, Saudi Arabia) for refractive surgery evaluation were considered for inclusion in this cross-sectional, retrospective study. All subjects were from the Aseer province, a southern, high-altitude region in Saudi Arabia, and presented between January and December 2017. The incidence of keratoconus and other refractive surgery contraindications were examined.Results. A total of 2931 patients were considered for inclusion in analyses. Of these, 2280 patients (77.8%) were not candidates for refractive surgery. These 2280 patients had a mean age of 24.1 ± 6.6 years and 1231 patients (54.0%) were male. Of the subjects who did not undergo refractive surgery, 548 (24%) had keratoconus, 400 (17.5%) were keratoconus suspects, 344 (15.1%) had thin corneas, 321 (14.1%) had high myopia, and 52 (2.3%) had a high astigmatism. An additional 479 subjects (21%) were candidates for refractive surgery, but chose not to undergo a procedure.Conclusion. The incidence of keratoconus in Saudi Arabian refractive surgery prospects was 18.7%. Keratoconus was the most common reason for not performing refractive surgery and accounted for 24.0% of cases in which surgery was not performed.

Refractive ophthalmology

2018 ◽  
pp. 925-1009
Keyword(s):  
Refractive Error ◽  
Contact Lens ◽  
Refractive Surgery ◽  
Photorefractive Keratectomy ◽  
Small Incision Lenticule Extraction ◽  
Small Incision ◽  
Lenticule Extraction

‘Refractive ophthalmology’ provides the reader with an introduction to the causes and treatment of refractive error. This chapter covers the use of spectacles, contact lens, and refractive surgery, including laser stromal in situ keratomileusis (LASIK), laser-assisted subepithelial keratomileusis (LASEK), photorefractive keratectomy (PRK), small-incision lenticule extraction (SMILE), incisional refractive surgery, collagen shrinkage procedures, and lens-based techniques.

The reaction of amorphous Ni-Nb films with Si in the presence of a native SiO2 layer

1990 ◽  
Vol 48 (4) ◽  
pp. 664-665
Author(s):  
N. Rozhanski ◽  
A. Barg
Keyword(s):  
High Temperature ◽  
Crystallization Temperature ◽  
Diffusion Barriers ◽  
Sio2 Layer ◽  
Si Substrate ◽  
Cross Sectional ◽  
Plan View ◽  
Temperature Range ◽  
Sputter Deposited

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.

A New Method of Wafer Level Plan View TEM Sample Preparation by DualBeam

2008 ◽  
Author(s):  
Hyoung H. Kang ◽  
Michael A. Gribelyuk ◽  
Oliver D. Patterson ◽  
Steven B. Herschbein ◽  
Corey Senowitz
Keyword(s):  
Sample Preparation ◽  
Ex Situ ◽  
Wafer Level ◽  
Cross Sectional ◽  
Plan View ◽  
Manufacturing Line ◽  
Transmission Electron ◽  
Thin Lamella ◽  
Preparation Techniques

Abstract Cross-sectional style transmission electron microscopy (TEM) sample preparation techniques by DualBeam (SEM/FIB) systems are widely used in both laboratory and manufacturing lines with either in-situ or ex-situ lift out methods. By contrast, however, the plan view TEM sample has only been prepared in the laboratory environment, and only after breaking the wafer. This paper introduces a novel methodology for in-line, plan view TEM sample preparation at the 300mm wafer level that does not require breaking the wafer. It also presents the benefit of the technique on electrically short defects. The methodology of thin lamella TEM sample preparation for plan view work in two different tool configurations is also presented. The detailed procedure of thin lamella sample preparation is also described. In-line, full wafer plan view (S)TEM provides a quick turn around solution for defect analysis in the manufacturing line.

scholarly journals Incidence, Characteristics and Outcomes of Large Vessel Stroke in COVID-19 Cohort: An International Multicenter Study

Neurosurgery ◽  
2021 ◽  
Author(s):  
Priyank Khandelwal ◽  
Fawaz Al-Mufti ◽  
Ambooj Tiwari ◽  
Amit Singla ◽  
Adam A Dmytriw ◽  
...  
Keyword(s):  
African Americans ◽  
Multicenter Study ◽  
Large Vessel ◽  
Vessel Occlusion ◽  
Cross Sectional ◽  
Younger Age ◽  
The Us ◽  
The Usa ◽  
Rehabilitation Facilities ◽  
International Multicenter Study

Abstract BACKGROUND While there are reports of acute ischemic stroke (AIS) in coronavirus disease 2019 (COVID-19) patients, the overall incidence of AIS and clinical characteristics of large vessel occlusion (LVO) remain unclear. OBJECTIVE To attempt to establish incidence of AIS in COVID-19 patients in an international cohort. METHODS A cross-sectional retrospective, multicenter study of consecutive patients admitted with AIS and COVID-19 was undertaken from March 1 to May 1, 2020 at 12 stroke centers from 4 countries. Out of those 12 centers, 9 centers admitted all types of strokes and data from those were used to calculate the incidence rate of AIS. Three centers exclusively transferred LVO stroke (LVOs) patients and were excluded only for the purposes of calculating the incidence of AIS. Detailed data were collected on consecutive LVOs in hospitalized patients who underwent mechanical thrombectomy (MT) across all 12 centers. RESULTS Out of 6698 COVID-19 patients admitted to 9 stroke centers, the incidence of stroke was found to be 1.3% (interquartile range [IQR] 0.75%-1.7%). The median age of LVOs patients was 51 yr (IQR 50-75 yr), and in the US centers, African Americans comprised 28% of patients. Out of 66 LVOs, 10 patients (16%) were less than 50 yr of age. Among the LVOs eligible for MT, the average time from symptom onset to presentation was 558 min (IQR 82-695 min). A total of 21 (50%) patients were either discharged to home or discharged to acute rehabilitation facilities. CONCLUSION LVO was predominant in patients with AIS and COVID-19 across 2 continents, occurring at a significantly younger age and affecting African Americans disproportionately in the USA.

Workplace violence towards emergency nurses: A cross-sectional multicenter study

2021 ◽  
Author(s):  
Abdalkarem F. Alsharari ◽  
Hana M. Abu-Snieneh ◽  
Fuad H. Abuadas ◽  
Nahed E. Elsabagh ◽  
Abdulellah Althobaity ◽  
...  
Keyword(s):  
Multicenter Study ◽  
Workplace Violence ◽  
Emergency Nurses ◽  
Cross Sectional
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