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Cataract is the leading cause of blindness worldwide. Epidemiological studies revealed up to a fivefold increased prevalence of cataracts in diabetic subjects. Metabolomics is nowadays frequently implemented to understand pathophysiological processes responsible for disease occurrence and progression. It has also been used recently to study the metabolic composition of aqueous humor (AH). AH is a transparent fluid which fills the anterior and posterior chambers of the eye. It supplies nutrients and removes metabolic waste from avascular tissues in the eye. The aim of this study was to use metabolomics to compare the AH of diabetic and non-diabetic patients undergoing cataract surgery. Several antioxidants (methyltetrahydrofolic acid, taurine, niacinamide, xanthine, and uric acid) were found decreased (-22 to -61%, p-value 0.05-0.003) in AH of diabetics. Also amino acids (AA) and derivatives were found decreased (-21 to -36%, p-value 0.05-0.01) while glycosylated AA increased (+75-98%, p-value 0.03-0.009) in this group of patients. Metformin was detected in AH of people taking this drug. To our knowledge, this is the first metabolomics study aiming to assess differences in AH composition between diabetic and non-diabetic patients with cataract. An increased oxidative stress and perturbations in amino acid metabolism in AH may be responsible for earlier cataract onset in diabetic patients.

BackgroundWe studied the association between (1) the retinal thickness, volume and structure assessed by optical coherence tomography (OCT), and (2) vascular changes around the fovea in FA to define the role of these methods in the detection of ischemic diabetic maculopathy.MethodsThis retrospective observational study included 51 eyes of 51 patients with severe non-proliferative and proliferative diabetic retinopathy, considering that they present advanced ischemic retinal changes. Based on the clinical examination and presence of leakage on FA, patients with clinically significant macular edema were excluded.On FA, foveal avascular zone (FAZ) corresponds to capillary loss and reflects ischemic processes. Its outline and size were assessed according to the ETDRS standards. Patients were divided in two groups according to the severity of damage of the FAZ outline: ≤ grade 2 (n = 28) and ≥ grade 3 (n = 23).As we expected ischemia-related damage, SD-OCT images were evaluated for retinal structure, volume, total thickness with division into the outer and inner retina (to assess the influence of two, non-overlapping blood sources) and ganglion cell layer thickness.ResultsThe comparisons revealed that at least currently with described methods:1. There is no significant association between FAZ outline and retinal volume, total thickness, and thickness of the outer and inner retina and ganglion cell layer.2. There is no significant association between FAZ outline and following retinal structure characteristics: continuity of the external limiting membrane and inner segment/outer segment junction, and identification of the inner/outer retina boundary.3. The identification of ganglion cell layer boundaries was significantly more difficult in more advanced FAZ outline grades.4. FAZ size is not correlated with the retinal thickness and volume.ConclusionsIn patients with severe non-proliferative and proliferative diabetic retinopathy, it is not possible to predict FAZ outline/size based solely on the measurements assessing volume and thickness or retinal structure evaluation on OCT. Consequently, at present OCT cannot replace FA in the detection of ischemic diabetic maculopathy.

Aqueous humor (AH) is a transparent fluid which fills the anterior and posterior chambers of the eye. It supplies nutrients and removes metabolic waste from avascular tissues in the eye. Proper homeostasis of AH is required to maintain adequate intraocular pressure as well as optical and refractive properties of the eye. Application of metabolomics to study human AH may improve knowledge about the molecular mechanisms of eye diseases. Until now, global analysis of metabolites in AH has been mainly performed using NMR. Among the analytical platforms used in metabolomics, LC-MS allows for the highest metabolome coverage. The aim of this study was to develop a method for extraction and analysis of AH metabolites by LC-QTOF-MS. Different protocols for AH preparation were tested. The best results were obtained when one volume of AH was mixed with one volume of methanol : ethanol (1 : 1). In the final method, 2 µL of extracted sample was analyzed by LC-QTOF-MS. The method allowed for reproducible measurement of over 1000 metabolic features. Almost 250 metabolites were identified in AH and assigned to 47 metabolic pathways. This method is suitable to study the potential role of amino acids, lipids, oxidative stress, or microbial metabolites in development of ocular diseases.

Background. Evaluation of efficacy of the iStent trabecular bypass implant in reducing intraocular pressure (IOP) depending on the value pretreatment IOP and number of medications used before surgery in patients with primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PXG) and coexisting cataract. Methods. A prospective, uncontrolled, interventional case series. 72 patients, on a mean age of 72.42 ± 9.17, were divided into two groups depending on baseline IOP: group I < 26 mmHg and group II ≥ 26 mmHg. All subjects underwent ab interno implantation of a single iStent together with cataract surgery. Best-corrected visual acuity (BCVA), IOP, number of antiglaucoma medications, visual field, and number and type of complications were examined before and after surgery. Postoperative patients were followed up at 1, 7, and 30 days and 3, 6, 12, and 24 months. All the patients were washed out preoperatively as well as postoperatively. Results. The mean observation time was 20 months. The mean preoperative IOP was 21.03 ± 1.44 mmHg in group I and reduced to mean 15.60 ± 2.12 mmHg after operation. In group II, mean IOP reduced from 26.00 ± 0.00 to 18.56 ± 1.81 (p=0.003). Mean glaucoma medications decreased from 1.35 ± 0.65 to 0.29 ± 0.52 in group I (p<0.001) and from 2.89 ± 1.18 to 1.33 ± 1.50 in group II (p<0.001). At 24 months, medication reduction was significantly greater in group I than group II (p=0.026). Conclusions. Combined cataract surgery with implantation of iStent seems to be an effective procedure in patients with mild-to-moderate open-angle glaucoma and cataract. In patients with baseline IOP < 26 mmHg, surgery reduced IOP and medication use significantly declined to 2 years, with greater reductions achieved versus patients with baseline IOP ≥ 26 mmHg. This trial is registered with NCT03807869.

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(1) Flow disturbances within the ocular blood vessels of patients with type 2 diabetes were associated with atherogenic changes of coronary arteries. (2) In patients with type 2 diabetes and concomitant coronary artery disease, impaired blood flow within the ophthalmic and short posterior ciliary arteries was not related to diabetic retinopathy, but diabetic retinopathy was related to additional blood flow impairment within the central retinal artery.