Medical Hypothesis, Discovery & Innovation (MEHDI) Journals
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Schwann Cell-Mediated Preservation of Vision in Retinal Degenerative Diseases via the Reduction of Oxidative Stress: A Possible Mechanism
Full text linkAfter central nervous system (CNS) injuries, the regeneration process does not work out well except for remyelination process. This remyelination capacity in CNS can be mentioned as a worthy example of stem/precursor cell-mediated renewal process. Remyelination in CNS is mediated by Schwann cells which act mainly as remyelinating agents in peripheral nervous system (PNS) but several studies have shown their potential role in CNS too. Schwann cells have the capacity of supporting and saving retinal cells by secreting growth factors like: Brain-derived neurotrophic factor (BDNF), Glial cell-derived neurotrophic factor (GDNF), and Basic fibroblast growth factor (bFGF) in subretinal space. Retinal degenerative diseases are one of the most important debilitating concerns in modern countries which has encountered the problem of ageing population. One of the best examples of retinal degenerative disease which is a leading cause of permanent visual loss in Western world is age related macular degeneration (AMD). In United States it is believed that nearly 1.75 million, older than 40 years have end stages of this debilitating disease, and it is estimated that this number will progress to approximately 3 million people by year 2020. One of the most common pathways which is involved in initiation and development of retinal disease is called Oxidative stress. Schwann cells are capable of secreting high amounts of antioxidant enzymes which protect PNS in front of oxidative stress which is result of glucose fluctuation in diabetic patients. The antioxidant role of Schwann cells in PNS may be the possible mechanism which can make Schwann cells potent reconstructing agents in CNS and especially in retinal injuries and retinal degenerative disease
Rate of Parental Consanguineous Marriage among Patients with Visual Impairments in Turkey
Full text linkWe aimed to describe the causes, characteristics, and rate of parental consanguineous marriage associated with patients with visual impairments in Turkey. This study involved 236 patients with visual impairments. The 10th revision of the International Classification of Diseases was used to categorize the causes of visual impairments (based on the main cause in both eyes). The mean age of the patients was 38.5 ± 24.2 years (range, 6–95 years), and most were in the 15–30-year age group (35.6%). There were more male patients (65%) than female patients. Blindness, severe visual impairment, and mild to moderate visual impairment were observed in 30 (12.7%), 84 (35.6%), and 122 (51.6%) patients, respectively. Choroidal and retinal diseases were identified as the main underlying cause of visual impairment (62.7%), followed by nystagmus (23.7%), optic tract and nerve diseases (11.0%), congenital cataracts (0.8%), and glaucoma (1.7%). Parental consanguinity was present for 26.3% of the patients, and it was significantly more common in the 15–30-year age group (50%) compared to the other age groups. In Turkey, the main cause of visual impairment was choroid and retinal diseases in all the age groups above 14 years, while nystagmus was the most common cause in the age group below 15 years. Parental consanguinity was significantly higher among the patients with macular dystrophy and those with retinitis pigmentosa than with retinopathy of prematurity, optic nerve diseases, age-related macular degeneration, and diabetic retinopathy. Genetic factors are known to be involved in the development of these diseases, indicating that the issue of consanguineous marriage remains a problem in Turkey.
Full-ring Intrastromal Corneal Implantation for Correcting High Myopia in Patients with Severe Keratoconus
Full text linkThe aim of this study was to evaluate the effect of the mechanical implantation of a MyoRing in patients with severe keratoconus and high myopia. The study involved 32 eyes of 32 patients (14 men and 18 women; mean age: 29.6 ± 6.7; age range: 20 – 44). The patients underwent MyoRing implantation with mechanical dissection using a Pocket Maker microkeratome, and outcomes were assessedat3 months after surgery. The main outcome measures were uncorrected and corrected distance visual acuity (UDVA and CDVA, both in Logarithm of the Minimum Angle of Resolution [logMAR] units), manifest refraction, and keratometry readings. There was a significant improvement in the UDVA, from 1.14 ± 0.32 to 0.35 ± 0.24 (P ˂ 0.001), and in the CDVA, from 0.47 ± 0.20 to 0.22 ± 0.15 (P ˂ 0.001). There was also a significant improvement in the spherical equivalent refractive error (-10.51 ± 2.81 D to -1.32 ± 2.29 D) (P ˂ 0.001). There was a significant decrease of manifest refraction in the mean sphere and cylinder of 7.70 and 2.6 D, respectively (P < 0.001). Furthermore, with regard to corneal topography, there was a significant reduction of 3.55 D (P ˂ 0.001) in the mean keratometry reading. The results show that the mechanical implantation of a MyoRing is effective for the correction of myopia in patients with keratoconus and high myopia.
Photorefractive Keratectomy (PRK) is Safe and Effective for Patients with Myopia and Thin Corneas
Full text linkThe aim of this study was to evaluate the long-term safety and efficacy of photorefractive keratectomy (PRK) for patients with myopia and thin corneas. In this retrospective case series, we included 74 eyes of 38 patients with myopia and central corneal thickness (CCT) < 550 µm who underwent PRK and had a mean postoperative follow-up period of four years. The following factors were evaluated: CCT, refraction, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), ablation depth, safety and efficacy indices (i.e., the ratio of the mean postoperative BCVA to the mean preoperative BCVA, and the ratio of the mean postoperative UCVA to mean preoperative the BCVA, respectively), and evidence of corneal ectasia (based on Orbscan topography images).The patients were aged 20 – 46 years (mean ±SD age, 28.18± 6.82 years). The mean ± SD pre- and postoperative CCTwas485.92 ± 9.27 µm and 434.84 ± 20.48 µm, respectively. The mean ± SD pre- and postoperative myopia was -2.77 D ± 1.51 and -0.24 ± 0.39 D, respectively, and the mean ± SD pre- and postoperative astigmatism was -0.82 D ± 0.99 and -0.37 ± 0.37 D, respectively. The mean pre- and postoperative BCVA and postoperative UCVA was 0.011 ± 0.03 Logarithm of the Minimum Angle of Resolution (log MAR), 0.003 ± 0.01 log MAR, and 0.054 ± 0.09 log MAR, respectively. The mean ± SD ablation depth, safety index and efficacy index was 54.34 ± 16.28 µm, 0.02 ± 0.12, and 0.11 ± 0.50, respectively. Regarding the postoperative corneal clarity, 72 eyes (97.3%) had a clear cornea (grade 0) and the remaining two eyes of one patient (2.70%) had a trace haze (grade 1). There was no evidence of corneal ectasia on any of the Orbscan topography images. Thus, among patients with myopia and thin corneas (<500 µm), PRK seems to be acceptable in terms of both safety and efficacy 4 years after surgery, based on the stability of postoperative refraction, visual acuity, and topographic outcomes, and outcomes based on the safety and efficacy indexes.
Correlation between Macular Thickness and Visual Field in Early Open Angle Glaucoma: A Cross-Sectional Study
Full text linkThe aim of this study was to correlate macular thickness and visual field parameters in early glaucoma. A total of 104 eyes affected with early glaucoma were examined in a cross-sectional, prospective study. Visual field testing using both standard automated perimetry (SAP) and shortwave automated perimetry (SWAP) was performed. Global visual field parameters, including mean deviation (MD) and pattern standard deviation (PSD), were recorded and correlated with spectral domain optical coherence tomography (SD-OCT)-measured macular thickness and asymmetry. Average macular thickness correlated significantly with all measures of visual field including MD-SWAP (r = 0.42), MD-SAP (r = 0.41), PSD-SWAP (r = -0.23), and PSD-SAP (r = -0.21), with P-values <0.001 for all correlations. The mean MD scores (using both SWAP and SAP) were significantly higher in the eyes with thin than in those with intermediate average macular thickness. Intraeye (superior macula thickness – inferior macula thickness) asymmetries correlated significantly with both PSD-SWAP (r = 0.63, P < 0.001) and PSD-SAP (r = 0.26, P = 0.01) scores. This study revealed a significant correlation between macular thickness and visual field parameters in early glaucoma. The results of this study should make macular thickness measurements even more meaningful to glaucoma specialists.
The Role of Mitochondrial DNA (mtDNA) in the Development of Diabetic Retinopathy (DR): A Systematic Review
Full text linkDiabetic Retinopathy (DR) is the most prevalent health problem, which is influenced by environmental and genetic factors with an increasing prevalence. The current systematic review is focused on mtDNA modification, including polymorphism and mutation/deletion, with a direct effect on DR. This systematic search was initially done through PubMed, Cochrane, EMBASE, SCOPUS, and Web of Science without a restriction on the years of publication. The terms searched included ‘‘mtDNA’’, ‘‘mitochondrial DNA’’, ‘‘diabetes’’, ‘‘diabetic’’, ‘‘retina’’, and ‘‘diabetic retinopathy’’. Animal, cohort, cross-sectional, and in vitro studies, as well as case series, case reports, review articles, and Letters to Editor were excluded from this research. From 1528 resulting searched articles, only 12 papers were finally chosen as the case-control studies considering mtDNA gene and DR. Actually, of these 12 articles, 8 studies were concerned with mtDNA polymorphisms (UCP1, UCP2, ROMO-1, and Mn-SOD) and 4 articles were related to mtDNA mutation (A3243G mutation in tRNALeu(UUR) gene and mtDNA deletion (ΔmtDNA 4977)). Some conflicting results were found between the selected genetic modifications of mtDNA, such as Mn-SOD, UCP1, ΔmtDNA 4977, tRNALeu (UUR), and ROMO-1. Finally, A3243G mutation in the tRNALeu (UUR) gene and rs660339 and V16A polymorphisms of UCP2 and Mn-SOD genes were respectively considered as the most important factors in the pathogenesis of DR.
The Relationship of Body Mass Index and Blood Pressure with Corneal Biomechanical Parameters in Healthy Subjects
Full text linkThis study aimed to assess the possible relationship of body mass index (BMI) and blood pressure (BP) with corneal biomechanical parameters in healthy subjects. The study included 88 eyes of 88 healthy subjects aged 20–40 years. After a thorough medical history, a digital sphygmomanometer was used to measure the systolic blood pressure (SBP) and diastolic blood pressure (DBP). In addition, several hematological and biochemical parameters were determined to assess general health. Before the ophthalmic examination, the body height and weight were measured; then, the BMI was calculated. Finally, after comprehensive ophthalmic examination, all cases were evaluated with Pentacam (Oculus) in order to rule out corneal ectasia; then, the corneal biomechanical parameters of all individuals were measured using the Scheimpflug-based Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany). If the measurements of the hematological and biochemical parameters were within normal range, the results of the Corvis ST, BMI, and BP were included in the analysis carried out with SPSS software. The mean (± standard deviation [SD]) BMI, SBP, DBP, intraocular pressure (IOP), central corneal thickness (CCT), deformation amplitude, radius, and peak distance was 27.24 ± 4.80 kg/m2, 116.47 ± 11.21 mmHg, 80.51 ± 5.68 mmHg, 15.10 ± 1.70 mmHg, 533.10 ± 30.97 m, 1.03 ± 0.11 mm, 7.51 ± 0.86 mm, and 5.03 ± 0.30 mm, respectively. According to the World Health Organization’s classification of BMI, the results showed no significant difference in IOP, CCT, peak distance, radius, and deformation amplitude between different BMI subcategories (all P > 0.05). The results of the Corvis ST showed that corneal biomechanical parameters had no significant correlation with BMI, SBP, and DBP in three subgroups of BMI and all participants (all P > 0.05) but the results showed a positive correlation between CCT and IOP (P < 0.001, r = 0.504) in all participants. CCT and IOP had no correlation with BMI, SBP, and DBP (all P > 0.05). This study showed that BMI and BP had no correlation with corneal biomechanical parameters in healthy subjects using the Corvis ST. Our results can be used in clinical practice.
Comparison of Intravitreal Bevacizumab and Intravitreal Diclofenac in the Treatment of Diabetic Macular Edema: a 6-month Follow-up
Full text linkThe aim of this study was to compare the effect of intravitreal diclofenac, a non-steroidal anti-inflammatory drug (NSAID), with that of bevacizumab, a well-known anti-vascular endothelial growth factor (VEGF) drug, in the treatment of diabetic macular edema (DME). Diclofenac was chosen in this study because it has both features of NSAIDs and corticosteroids by inhibiting the cyclooxygenase (COX) and lipoxygenase pathways, respectively. In this non-randomized comparative interventional case series, 64 eyes from 32 patients with bilateral naïve DME were selected and every eye was randomly assigned to intravitreal injection of bevacizumab (IVB) or diclofenac (IVD). After exclusion of some patients because of short follow-up duration or less than two intravitreal injections, finally, 52 eyes from 26 patients were analyzed. Of those, 26 eyes received 500 µg/0.1 mL IVD and 26 eyes received 1.25 mg IVB. After 6 months of follow-up, the results indicated that visual acuity was significantly improved from 0.50 ± 0.13 in IVB and 0.52 ± 0.12 LogMAR in IVD at baseline to 0.2 ± 0.1 and 0.29 ± 0.07, respectively. Central macular thickness (CMT) and macular volume were measured based on spectral-domain optical coherence tomography (OCT) at month 1, 3, and 6. Both groups showed a significant reduction in CMT and macular volume from baseline but there was no significant difference between the IVB and IVD groups. Interestingly, IVD, but not IVB, decreased intraocular pressure (IOP), which is a desirable effect. There was no serious complication due to injections. This study sheds light into the long-term effects of NSAIDs and may support the idea that inflammation suppression by NSAIDs may have the same results as anti-VEGF administration.
Single Injection of Bupivacaine for Correction of Strabismus
Full text linkTo evaluate the effectiveness of a single injection of Bupivacaine (BPX) application for correction of eso/exodeviations this study has been performed. A retrospective review of 30 patients with eso/exodeviations less than 20 prism diopters (PD). Preoperative deviations were recorded in PD, using the alternate prism cover test. Postoperative angles at 1 and 3 months were measured in the same manner. The mean angle of deviation for near in all patients reduced significantly by 3.1 PD and 2.1 PD at 1 and 3 months. The mean angle of deviation for distance in all patients also decreased significantly by 2.3 PD and 1.9 PD at 1 and 3 months. As conclusions, single injection of BPX in a heterogeneous group of patients with horizontal strabismus caused a mild improvement in a qualitative success rate of 37%
Nodular Scleritis in Association with Panuveitis in Behçet’s Disease
Full text linkThis case report involves a 32-year-old man with Behçet’s disease who had simultaneous bilateral anterior uveitis, unilateral nodular scleritis, and occlusive vasculitis with retinal hemorrhages. Although scleritis is not a classical feature of Behçet’s disease, a diagnosis of Behçet’s disease should be considered in patients with scleritis