فهرست مطالب بهزاد برازنده

Thickness evaluation and analysis of corneal layers are important for diagnosis and treatments considering corneal disease. Optical Coherence Tomography (OCT) can produce micron-scaled cross-sectional images in a non-invasive and non-contacting manner. Since manual segmentation and layer detection within such images are time-consuming, physicians prefer automatic/semi-automatic methods. This paper reviewed main and important methods of corneal layer segmentationsapplied to OCT images. The methods are compared and described in three categories: preprocessing, segmentation, and thickness mapping (layers’ topography). The purpose of preprocessing was to remove noise and artifacts from such OCT images. Studies show that methods based on Hough transform, which are consistent with the corneal arc structure when compared to graph and threshold methods, are able to extract accurate boundaries in a reasonable time. Meanwhile, artificial intelligence and the deep learning approach has opened new horizons in segmentation and analysis of such images. In studies, generally the aim was to extract and present OCT image information in a form that would help ophthalmologists better diagnose and treat corneal abnormalities; therefore it can be concluded thatlayer topography and its related issues that require automatic processing of a set of cross-sectional images, isan important output that is not addressed in many research.

To compare the efficacy of adding an opposite clear corneal incision (OCCI) on the steep axis during phacoemulsification in reducing the pre-existing corneal astigmatism. This randomized clinical trial was performed on 120 eyes with corneal astigmatism of >1D undergoing phacoemulsification. Incisions were made based on the type of astigmatism as follows: superior or superior+OCCI in the with-the-rule and temporal or temporal+OCCI in the against-the-rule astigmatism. Patients were followed with refraction, keratometry and topography. Statistical analyses were done using one and two ways ANOVA and Tukey-a test. Mean corneal astigmatism was 1.82±0.86 D in the superior+OCCI group and 1.74±0.86 D in the temporal+OCCI group preoperatively which respectively decreased to 1.31±0.59 (P= 0.013) and 1.19±0.64 (P= 0.009) postoperatively. No significant changes occurred in the amount of astigmatism in none of the two single incision groups. Paired OCCI on steep axis is a useful technique to correct mild to moderate pre-existing astigmatism with no need to extra skill or instrumentation.

To compare the efficacy and safety of two local anesthetic methods; retrobulbar anesthesia and parabulbar anesthesia using PTFE intravenous cannula without needle in extracapsular cataract surgery. A randomized prospective partially blind study was conducted on 66 eyes of 66 patients with senile cataract who were scheduled for ECCE and PC IOL surgery. After randomization, 35 patients received retrobulbar anesthesia and 31 received parabulbar anesthesia. IOP was measured preoperatively and 1, 5, 15, and 30 min after injection. Akinesia was measured 1, 5, 15, and 30 min after injection. Akinesia was graded as 0, 1, 2, in which zero means complete absence of movement or minimal movement around primary position; 1 means relative akinesia: residual movement of one muscle or relative reduction of muscle movement in all directions; and 2 means no akinesia. Pain was measured using a 10 point visual analog scale immediately after injection. Parabulbar anesthesia was performed with an IV cannula, gauge 22, 25 mm length, made from PTFE (poly tetra fluoro ethylene). The IV cannula sheath was used and its needle was discarded. Patients included 47% female and 53% male subjects. Mean age was 68 yr. There was no significant difference in the age and sex distribution and preinjection intraocular pressure between two groups. Akinesia was significantly more complete at all times after injection in group with parabulbar anesthesia. IOP was significantly higher at all times after injection in eyes with parabulbar anesthesia. Pain sensation was not significantly different between two groups. Major complications were not seen in any groups. Minor complications including chemosis (32%) and hemorrhage at site of peritomy (95%) were seen in parabulbar group. Parabulbar anesthesia produces better and faster akinesia than retrobulbar anesthesia but it can cause more IOP elevation that should be considered in patients with compromised ocular circulation. This needle-free variation of parabulbar anesthesia in an effective and safe technique for local anesthesia in cataract surgery.