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    Cyclotorsion measurement using scleral blood vessels
    (Elsevier Ltd, 2017) Kaya, Aydın; Keçeli, Ali Seydi; Can, Ahmet Burak; Çakmak, Hasan Basri
    Background and Objectives Measurements of the cyclotorsional movement of the eye are crucial in refractive surgery procedures. The planned surgery pattern may vary substantially during an operation because of the position and eye movements of the patient. Since these factors affect the outcome of an operation, eye registration methods are applied in order to compensate for errors. While the majority of applications are based on features of the iris, we propose a registration method which uses scleral blood vessels. Unlike previous offline techniques, the proposed method is applicable during surgery. Methods The sensitivity of the proposed registration method is tested on an artificial benchmark dataset involving five eye models and 46,305 instances of eye images. The cyclotorsion angles of the dataset vary between ?10° and +10° at 1° intervals. Repeated measurements and ANOVA and Cochran's Q tests are applied in order to determine the significance of the proposed method. Additionally, a pilot study is carried out using data obtained from a commercially available device. The real data are validated using manual marking by an expert. Results and Conclusions The results confirm that the proposed method produces a smaller error rate (mean = 0.44 ± 0.41) compared to the existing method in [1] (mean = 0.64 ± 0.58). A further conclusion is that feature extraction algorithms affect the results of the proposed method. The SIFT (mean = 0.74 ± 0.78), SURF64 (mean = 0.56 ± 0.46), SURF128 (mean = 0.57 ± 0.48) and ASIFT (mean = 0.29 ± 0.25) feature extraction algorithms were examined; the ASIFT method was the most successful of these algorithms. Scleral blood vessels are observed to be useful as a feature extraction region due to their textural properties. © 2017 Elsevier Ltd
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    Long-Term Clinical Outcomes of Myopic Patients Having Thin Residual Corneal Thickness after Excimer Laser Surface Ablation
    (Taylor and Francis Ltd, 2017) Kocamış, Sücattin İlker; Çakmak, Hasan Basri; Gerçeker, Sıdıka; Çağıl, Nurullah
    Purpose: To investigate and compare the long-term safety, efficacy, and accuracy of PRK (photorefractive keratectomy) and LASEK (laser epithelial keratomileusis) in myopic corneas having residual corneal thickness less than 400 micron meters (µm). Methods: The medical reports of the patients who had undergone excimer laser surface ablation between 2007–2011 and had a residual corneal thickness less than 400 µm were retrospectively reviewed. Results: Forty-two eyes of 42 patients with a mean age of 28.79±7.76 years were enrolled into the study. Twenty-two PRK and 20 LASEK procedures were performed. The mean follow-up time was 45.00±11.80 months. At the end of follow-up, no ectasia was detected. Nineteen percent of eyes had trace haze. No eyes lost any lines in corrected distance visual acuity. Eighty-one percent of the patients had an uncorrected distance visual acuity better than 20/40. The regression rate was 16.7%. Sixty-two percent of eyes were within ±1.00 D. The safety and efficacy indexes were 1.19±0.42 and 1.00±0.40, respectively. There was not any difference between LASEK and PRK regarding achieved spherical equivalent refraction, haze ratio, visual acuity, safety, efficacy, and regression. Conclusions: Both PRK and LASEK are safe and effective in myopic corneas having thin residual thickness. © Taylor & Francis.
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    The evaluation of the risk factors for capsular complications in phacoemulsification
    (Springer Netherlands, 2018) Berk Ergun, Şule; Kocamış, Sücattin İlker; Çakmak, Hasan Basri; Çağıl, Nurullah
    PurposeTo determine and quantify the risk factors for disruption of lens capsule integrity during phacoemulsification.MethodsThe medical records of the patients who had undergone phacoemulsification cataract surgery and had a complication associated with lens capsule were reviewed. Consecutive cases were also reviewed in reverse chronological order as a control group. The exclusion criteria were pediatric cataracts, traumatic cataracts and lens dislocation. As a result, 403 uncomplicated and 83 complicated eyes were analyzed. The differences between the complication group and the group without complications regarding the risk factors were shown by employing the Chi-square test and Fischer's exact test. The variables having the level of significance (p<0.25) after the Chi-square test and Fischer's exact test were enrolled into the multiple stepwise logistic regression analysis.ResultsAge (60-69/80) (p=0.017), male gender (p=0.006), pupil size 3mm (p=<0.001), mature-brunescent cataract (p=<0.001), anterior chamber depth <2.5mm (p=0.001), posterior polar cataract (p=0.006), diabetic retinopathy(p=<0.001), coronary artery disease (p=0.098) and surgeon factor (junior resident/senior resident, p=0.015; senior resident/specialist in ophthalmology, p=0.026; junior resident/specialist in ophthalmology, p=0.020) were among the factors significantly related to a capsule complication. An Excel program has been developed according to these results to predict the probability of capsule complication.Conclusions Higher-risk cases can be predicted preoperatively, thus allowing surgeons to take appropriate precautions, better informing the patient and better selecting the cases especially for trainee surgeons.
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    Transscleral delivery of bevacizumab-loaded chitosan nanoparticles
    (American Scientific Publishers, 2019) Uğurlu, Nagihan; Aşık, Mehmet Doğan; Çakmak, Hasan Basri; Tuncer, Sema; Türk, Mustafa; Çağıl, Nurullah; Denkbaş, Emir Baki
    Purpose: The aim of this study was to synthesize bevacizumabloaded nanoparticles and evaluate their effects on the treatment of posterior segment diseases via subtenon injections. Methods: Bevacizumabloaded chitosan nanoparticles (BLCNs) were synthesized by the ionic gelation method, and their physicochemical characteristics and in vitro release profile were studied. The BLCNs were characterized using atomic force microscopy (AFM), FTIR spectroscopy, dynamic light scattering, and scanning electron microscopy. The BLCNs were delivered into rabbits eyes via posterior subtenon injections. An immunohistochemical evaluation of the ocular tissues was performed, and the vitreous humor and serum bevacizumab levels were measured by ELISA. Results: Bevacizumabloaded chitosan nanoparticles with a diameter of 80 to 380 nm were prepared and characterized. In vitro studies showed that after the first 5 days of the experiment, a significant increase in the drug release maintained the desired drug dosage for 3 weeks. Immunohistochemical in vivo studies revealed that there were BLCNs penetrating through the sclera. Furthermore, the intravitreal bevacizumab concentration reached a maximum concentration of 18 gml, and it decreased to 6 gml after only a week. Conclusion: The results revealed that subtenon injection of BLCNs is a promising alternative to intravitreal injections. In addition to the ELISA studies, immunohistochemical experiments confirmed that BLCNs enable transscleral bevacizumab penetration, and BLCN usage may provide the required bevacizumab levels for the treatment of posterior segment diseases. © 2019 American Scientific Publishers