Researcher:
Şahin, Afsun

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Afsun

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Şahin

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Şahin, Afsun

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2017 - 2019132020 - 202369

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    Peripapillary choroidal vasculature in pediatric eyes with type 1 diabetes mellitus
    (Kare Yayıncılık, 2022) N/A; N/A; Hasanreisoğlu, Murat; Kesim, Cem; Uzunay, Nur Sena; Taş, Ayşe Yıldız; Karslıoğlu, Melisa Zişan; Şahin, Afsun; Faculty Member; Teaching Faculty; Undergraduate Student; Faculty Member; Doctor; Faculty Member; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); School of Medicine; School of Medicine; School of Medicine; School of Medicine; N/A; School of Medicine; N/A; N/A; N/A; N/A; Koç University Hospital; N/A; 182001; 387367; N/A; 200905; N/A; 171267
    Objectives: choroidal vasculature change in children with diabetes mellitus is not investigated enough although it could reflect clinical outcome. Methods: pediatric Type 1 diabetes mellitus (T1DM) patients and healthy controls were retrospectively evaluated. Peripapillary retinal nerve fiber layer optical coherence tomography (OCT) images of the right eyes were analyzed. Choroidal parameters including total choroidal area, luminal area, stromal area, and choroidal vascularity index were measured through image binarization. Results: twenty eyes of 20 patients were compared with 46 eyes of 46 healthy controls. Mean total choroidal area, luminal area, and stromal area were 1.59±0.35, 1.10±0.24, and 0.50±0.13 mm2 in patients’ eyes and 1.52±0.49, 1.05±0.34, and 0.47±0.17 mm2 in healthy eyes. No difference was found in choroidal vascularity indices between patients and healthy eyes (68.8±3.9% vs. 69.4±4.4%, p=0.521). Temporal choroidal vascularity index was significantly higher than its nasal counterpart in healthy eyes (71.8±5.0% vs. 68.6±4.9%, p<0.001) which was not significant in patients’ eyes (70.7±4.0% vs. 68.9±5.1%, p=0.067). Temporal quadrant had the highest choroidal vascularity index score among all quadrants in healthy controls (all p<0.05), whereas no choroidal vascularity index difference between quadrants was detected in patients (p=0.75). Conclusion: peripapillary choroidal vasculature has shown subtle sectoral changes which did not reflect the overall peripapillary OCT section in pediatric T1DM patients when compared with healthy controls.
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    The effect of thyroid eye disease on corneal biomechanical properties
    (Kare Yayıncılık, 2022) N/A; Cömert, Melis Cansu; Yılmaz, Sezen Güçlü; Taş, Ayşe Yıldız; Şahin, Afsun; Undergraduate Student; Undergraduate Student; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; N/A; N/A; 200905; 171267
    Objectives: the aim of this study was to identify corneal biomechanical parameters measured by ORA in patients with TED compared to the healthy group. The NOSPECS classification of patients is used to assess the relation between biomechanical changes and disease severity. Methods: we included 22 TED patients, diagnosed with TED for more than five years, and 43 healthy participants. The NOSPECS classification was assessed as mild (grade 1-3) and severe (grade 4-6) disease. For each group, corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), Goldmann-correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) parameters were measured by ORA. Results: the mean age was 38.8±11.6 years for the TED patients and 42.9±15.58 years for the control group. For TED patients and healthy volunteers, the mean levels of CRF, CH, and CCT were measured as follows: 10.43±2.04 vs 10.28±1.91mmHg, p=0.67; 10.18±1.81 vs 10.21±1.68 mmHg, p=0.90; 550.31±35.73 vs 545.23±37.91 µm, p=0.47, respectively. These values were not significant between groups, but they were significantly higher in females compared to males in TED patients [CRF;10.68 (IQR: 9.49-12.14) vs 8.96 (IQR: 8.04-9.92) mmHg, p=0.002, CH; 10.43 (IQR: 9.48-11.25) vs 8.58 (IQR: 7.90-9.95) mmHg, p=0.003 and CCT; 554.25 (IQR: 536.05-579.52) vs 527.40 (IQR: 492.25-545.90) μm, p=0.014]. CRF values were negatively correlated with NOSPECS score (r=-0.317, p=0.036) and significantly higher CRF was observed in mild patients compared to severe disease (11.43 (IQR: 10.14-12.87) vs 9.46 (IQR: 8.75-10.28) mmHg, p=0.008). Conclusion: we found a significant gender effect on corneal biomechanical parameters of TED patients. CRF, CH and CCT values were significantly higher in females compared to males with TED. The clinical severity score of TED showed negative correlation with CRF. CRF value might be a useful parameter in follow-up of TED patients in clinical practice.
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    Noninvasive optical coherence tomography imaging correlates with anatomic and physiologic end-organ changes in healthy normotensives with systemic blood pressure variability
    (Lippincott Williams & Wilkins, 2020) Afşar, Barış; Sağ, Alan A.; N/A; Dağel, Tuncay; Derin, Gözde; Kesim, Cem; Taş, Ayşe Yıldız; Şahin, Afsun; Dinçer, Neris; Kanbay, Mehmet; Doctor; Undergraduate Student; Teaching Faculty; Faculty Member; Faculty Member; Undergraduate Student; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; N/A; N/A; 387367; 200905; 171267; 349025; 110580
    Objective: Blood pressure variability (BPV) is considered as a novel risk factor for cardiovascular disease including left ventricular hypertrophy, vascular stiffness, and renal dysfunction. In this study, we aimed to determine the relationship between ambulatory BPV with subclinical organ damage and vascular stiffness parameters in normotensive healthy subjects. Methods: A total of 100 healthy subjects over 18 years of age were included in this cross-sectional study. We divided the participants into two groups according to the median value of the SD of mean 24-h blood pressure (BP) (Group 1: SD of mean 24-h BP 10.15). BPs of these subjects were recorded over a 24-h period using ambulatory BP monitoring. Mobil-O-Graph device was used to estimate the augmentation index (AIx), pulse wave velocity (PWV), and ambulatory BP measurement. The choroidal thickness was measured by using optical coherence tomography device. Results: The mean age of the patients was 25.4 +/- 5.0 years. Choroidal thickness was correlated with PWV, AIx, protein excretion, and SD of systolic and diastolic BP (P < 0.05). Additionally, participants with higher BP variability have lower choroidal thickness and higher AIx. Conclusion: We showed that even in normotensive subjects, BPV correlates with choroid thickness. Thus, BPV can be an early prognostic parameter for pathologic vascular changes.
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    Meibomian gland dysfunction in primary and secondary sjogren syndrome
    (Karger Publishers, 2018) Sullivan, David A.; Dana, Reza; Sullivan, Rose M.; Krenzer, Kathleen L.; Arica, Beril; Liu, Yang; Kam, Wendy R.; Papas, Athena S.; Cermak, Jennifer M.; Şahin, Afsun; Faculty Member; School of Medicine; 171267
    Purpose: We hypothesized that women with primary (pSS) and secondary Sjogren syndrome (sSS; with systemic lupus erythematosus [SLE] or rheumatoid arthritis [RA]) have meibomian gland dysfunction (MGD). We sought to test our hypothesis. Methods: Subjects with pSS, sSS + SLE, sSS + RA, and non-SS-related MGD were recruited from the Sjogren's Syndrome Foundation or outpatient clinics at Tufts University School of Dental Medicine or Brigham and Women's Hospital. The control population was recruited from the Greater Boston area. After providing written informed consent, the subjects underwent an eye examination and/or completed two questionnaires that assess symptoms of dry eye disease (DED). Results: Our results demonstrate that pSS and sSS patients have MGD. These subjects had meibomian gland orifice metaplasia, an increased number of occluded meibomian gland orifices, and a reduced quality of meibomian gland secretions. Further, patients with pSS, sSS + SLE, sSS + RA, and MGD had significant alterations in their tear film, lid margin, cornea, and conjunctiva. Symptoms of DED were increased similar to 10-fold in all pSS, sSS, and MGD groups relative to controls. Conclusions: Our findings support our hypothesis and show that individuals with pSS, sSS + SLE, and sSS + RA have MGD. In addition, our study indicates that patients with pSS and sSS have both aqueous-deficient and evaporative DED.
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    Visual acuity, defocus curve and patient satisfaction of a new hybrid EDOF-multifocal diffractive intraocular lens
    (Sage Publications Ltd, 2022) Özturkmen, Cem; Karadeniz, Pınar Günel; N/A; Kesim, Cem; Şahin, Afsun; Doctor; Faculty Member; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); School of Medicine; School of Medicine; 387367; 171267
    Purpose: To evaluate the visual acuity, defocus curve and visual quality of life following bilateral implantation of a new hybrid extended depth of focus (EDOF)-multifocal diffractive intraocular lens (IOL). Methods: Patients who underwent cataract surgery with bilateral implantation of Tecnis Synergy IOL were enrolled in this study. The main outcomes were defined as uncorrected distant, intermediate and near visual acuities (UDVA, UIVA and UNVA, respectively), defocus curve and VF-14 questionnaire aimed for visual performance. Results: The mean +/- SD values for binocular UDVA, UIVA and UNVA were -0.01 +/- 0.04, 0.05 +/- 0.03 and 0.03 +/- 0.05 logMAR, respectively. Defocus curve showed a continuous vision above 0.16 logMAR between +0.50 D and -2.50 D. Patients had good visual performance with mean VF-14 scores above 3 points. Driving at night (3.47 +/- 0.64) was found to be the most difficult task to perform. Spectacle independence was 100% for both distant and near vision. Conclusion: Bilateral implantation of Tecnis Synergy IOL in cataract patients shows good visual acuity and performance, covering a good visual range without any need of spectacles.
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    Generative adversarial network based automatic segmentation of corneal subbasal nerves on in vivo confocal microscopy images
    (Association for Research in Vision and Ophthalmology, 2021) Arslan, Abdullah Taha; Demir, Sertaç; Barkana, Duygun Erol; Şahin, Afsun; Taş, Ayşe Yıldız; Yıldız, Erdost; Acer, Ali Faik; Faculty Member; Faculty Member; PhD Student; Undergraduate Student; School of Medicine; School of Medicine; Graduate School of Health Sciences; N/A; 171267; 200905; N/A; N/A
    Purpose: In vivo confocal microscopy (IVCM) is a noninvasive, reproducible, and inexpensive diagnostic tool for corneal diseases. However, widespread and effortless image acquisition in IVCM creates serious image analysis workloads on ophthalmol-ogists, and neural networks could solve this problem quickly. We have produced a novel deep learning algorithm based on generative adversarial networks (GANs), and we compare its accuracy for automatic segmentation of subbasal nerves in IVCM images with a fully convolutional neural network (U-Net) based method. Methods: We have collected IVCM images from 85 subjects. U-Net and GAN-based image segmentation methods were trained and tested under the supervision of three clinicians for the segmentation of corneal subbasal nerves. Nerve segmentation results for GAN and U-Net-based methods were compared with the clinicians by using Pearson’s R correlation, Bland-Altman analysis, and receiver operating characteristics (ROC) statis-tics. Additionally, different noises were applied on IVCM images to evaluate the perfor-mances of the algorithms with noises of biomedical imaging. Results: The GAN-based algorithm demonstrated similar correlation and Bland-Altman analysis results with U-Net. The GAN-based method showed significantly higher accuracy compared to U-Net in ROC curves. Additionally, the performance of the U-Net deteriorated significantly with different noises, especially in speckle noise, compared to GAN. Conclusions: This study is the first application of GAN-based algorithms on IVCM images. The GAN-based algorithms demonstrated higher accuracy than U-Net for automatic corneal nerve segmentation in IVCM images, in patient-acquired images and noise applied images. This GAN-based segmentation method can be used as a facilitat-ing diagnostic tool in ophthalmology clinics. Translational Relevance: Generative adversarial networks are emerging deep learning models for medical image processing, which could be important clinical tools for rapid segmentation and analysis of corneal subbasal nerves in IVCM images.
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    Automated diagnosis of keratoconus from corneal topography
    (Assoc Research Vision Ophthalmology Inc, 2021) N/A; N/A; N/A; Department of Industrial Engineering; N/A; Taş, Ayşe Yıldız; Hasanreisoğlu, Murat; Balım, Haldun; Gönen, Mehmet; Şahin, Afsun; Faculty Member; Faculty Member; Master Student; Faculty Member; Faculty Member; Department of Industrial Engineering; School of Medicine; School of Medicine; Graduate School of Sciences and Engineering; College of Engineering; School of Medicine; 200905; 182001; N/A; 237468; 171267
    Purpose: Although visual inspection of corneal topography maps by trained experts can be powerful, this method is inherently subjective. Quantitative classification methods that can detect and classify abnormal topographic patterns would be useful. An automated system was developed to differentiate keratoconus patterns from other conditions using computer-assisted videokeratoscopy. Methods: This system combined a classification tree with a linear discriminant function derived from discriminant analysis of eight indices obtained from TMS-1 videokeratoscope data. One hundred corneas with a variety of diagnoses (keratoconus, normal, keratoplasty, epikeratophakia, excimer laser photorefractive keratectomy, radial keratotomy, contact lens-induced warpage, and others) were used for training, and a validation set of 100 additional corneas was used to evaluate the results. Results: In the training set, all 22 cases of clinically diagnosed keratoconus were detected with three false-positive cases (sensitivity 100%, specificity 96%, and accuracy 97%). With the validation set, 25 out of 28 keratoconus cases were detected with one false-positive case, which was a transplanted cornea (sensitivity 89%, specificity 99%, and accuracy 96%). Conclusions: This system can be used as a screening procedure to distinguish clinical keratoconus from other corneal topographies. This quantitative classification method may also aid in refining the clinical interpretation of topographic maps.
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    Effect of biphalin on corneal epithelial wound healing
    (Wiley, 2018) Gedar, M.; Mollica, A.; N/A; N/A; N/A; Yıldız, Erdost; Özer, Berna; Şahin, Afsun; PhD Student; Researcher; Faculty Member; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Health Sciences; N/A; School of Medicine; N/A; N/A; 171267
    After physical or surgical damage of corneal epithelium, most of analgesic drugs, like non-selective opioid agonists and non-steroid anti-inflammatory drugs, cannot be used because of their negative effects on wound healing process. Biphalin is selective µ and Δ opioid receptor agonist which has proven analgesic effects on rodents. Our purpose of study is finding effects of biphalin on wound healing of corneal epithelium. We used primary culture of human corneal epithelial cells (HCECs) for examining effects of biphalin on wound healing. Firstly, we measured toxicity of Biphalin in various concentrations with MTT assay and we showed biphalin has no toxic effects on HCECs in lower concentrations than 100 µM in various incubation times. After MTT assay, we administered 1 µM and 10 µM biphalin at in vitro scratch assay of HCECs, biphalin increased wound closure process significantly at 1 µM concentration (p < 0.05). Then we tested effects of biphalin on cell migration and proliferation separately. Bifalin increased migration of HCECs significantly (p < 0.01) at transwell migration assay. But we did not observe any significant difference between groups in Ki67 proliferation assay. In all these experiments, we also used naloxone to inhibiting effects of biphalin. In biphalin plus naloxone groups, effects of biphalin decrease partially. Our study results suggest, biphalin has positive effects on epithelial wound healing via opioid receptors. This effect because of increased migration of HCECs under influence of biphalin. With these findings, we propose biphalin as a new analgesic agent for post-surgical and post-traumatic care of corneal epithelial wounds.
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    Astigmatic vectorial analysis in pediatric keratoconus after unilateral cross-linking treatment
    (Lippincott Williams & Wilkins, 2022) Öztürkmen, Cem; N/A; N/A; Kesim, Cem; Şahin, Afsun; Doctor; Faculty Member; School of Medicine; School of Medicine; 387367; 171267
    Purpose: The aims of this study were to evaluate the treatment response of pediatric keratoconus (KC) patients to unilateral corneal collagen cross-linking (CXL) in treated eyes, disease progression in untreated eyes, and define the predictive value of astigmatic parameters by astigmatic vectorial analysis. Methods: Pediatric patients with KC with CXL-treated progressive eye and untreated fellow eye were included. Patients with other ocular conditions and a history of previous ocular surgery were excluded. Astigmatic changes in anterior and posterior corneal surfaces were evaluated with vectorial analysis. The receiver operating characteristic curves were analyzed to detect the best parameter that discriminates treated and untreated groups. Results: Thirty-two eyes of 16 patients with at least 2-year follow-up were analyzed. The maximum keratometry (K) in CXL-treated eyes remained stable (from 53.51 +/- 2.86-53.41 +/- 2.84 diopter (D), P = 0.84) while the steepest K increased in untreated eyes (from 47.82 +/- 1.71-49.59 +/- 3.32 D, P = 0.03). The oblique components of corneal astigmatism in CXL-treated eyes were higher than those of fellow eyes (all P < 0.05), which significantly decreased in the anterior 3-mm zone after treatment (P = 0.048). The mean differential astigmatism magnitudes were significantly higher in treated eyes (all P < 0.05). The refractive centroid remained unchanged in treated eyes (P = 0.553) and shifted in the oblique direction in untreated eyes (P = 0.04). The oblique differential astigmatism in the anterior 7-mm zone showed the highest area under the curve value in predicting treatment efficacy (0.813, 95% confidence interval: 0.646-0.981, P < 0.001). Conclusions: Astigmatic vectorial analysis is an objective tool for longitudinal assessment of clinical outcomes in KC. Changes in the oblique components of corneal astigmatism might predict progression and treatment efficacy.
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    Investigation of mitophagy biomarkers in corneal epithelium of keratoconus patients
    (Taylor and Francis Inc, 2022) Gumus, Koray; Sarac, Ozge Ilhan; Cagil, Nurullah; N/A; N/A; N/A; N/A; N/A; N/A; Yıldız, Erdost; Aydemir, Dilara; Zibandeh, Noushin; Ünlü, Eda Kuşan; Karslıoğlu, Melisa Zişan; Şahin, Afsun; PhD Student; PhD Student; Researcher; Researcher; Doctor; Faculty Member; Graduate School of Health Sciences; Graduate School of Health Sciences; N/A; Graduate School of Health Sciences; N/A; School of Medicine; N/A; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); N/A; Koç University Hospital; N/A; N/A; N/A; N/A; N/A; N/A; 171267
    Purpose: The pathological mechanisms of keratoconus (KC) have not been elucidated yet. Mitophagy is an important mechanism that eliminates damaged mitochondria under oxidative stress, and it could be one of the leading pathological causes of KC. This study aimed to find out the role of mitophagy in the keratoconic corneal epithelium. Methods: The corneal epithelia were collected from the 103 progressive KC patients and the 46 control subjects. The real-time quantitative PCR was performed for PTEN-putative kinase-1 (PINK1), PARKIN, p62, and BNIP3 gene expressions in 31 KC and 9 control subjects. Western blot analyses were performed to investigate the protein expressions of PINK1, PARKIN, LC3B, ATG5, and BECLIN in the remaining 109 corneal epithelium samples from 72 patients and 37 control subjects. Results: mRNA and protein expressions of PINK1 decreased significantly in the corneal epithelium of KC patients compared to the control subjects. No significant change was found in mRNA levels of PARKIN, p62, and BNIP3 in KC patients. The protein expression of PARKIN, LC3B, ATG5, and Beclin did not significantly differ between KC patients and control subjects. Gene expression levels of mitophagy biomarkers were not affected by the KC grade. Conclusions: PINK1/PARKIN-dependent mitophagy is affected in the keratoconic corneal epithelium. We found significant decreases in both mRNA and protein expressions of PINK1 in the keratoconic corneal epithelium. However, we did not observe any other significant change in mitophagy markers. Mitochondrial stress-related mitophagy pathways could be interrupted by the decreased levels of PINK1 in the keratoconic corneal epithelium, but solely PINK1 dysregulation is not likely to induce KC pathogenesis.