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- Lubrication approximation for fluids with shear-dependent viscosityPublication . Pereira, Bruno M. M.; Dias, Gonçalo A. S.; Cal, Filipe S.; Rajagopal, Kumbakonam R.; Videman, Juha H.We present dimensionally reduced Reynolds type equations for steady lubricating flows of incompressible non-Newtonian fluids with shear-dependent viscosity by employing a rigorous perturbation analysis on the governing equations of motion. Our analysis shows that, depending on the strength of the power-law character of the fluid, the novel equation can either present itself as a higher-order correction to the classical Reynolds equation or as a completely new nonlinear Reynolds type equation. Both equations are applied to two classic problems: the flow between a rolling rigid cylinder and a rigid plane and the flow in an eccentric journal bearing.
- Trapped modes in a fluid with three layers topped by a rigid lidPublication . Cal, Filipe; Dias, Gonçalo A. S.; Pereira, Bruno M. M.We consider trapping of linear water waves by a submerged horizontal cylinder in a three-layer fluid topped by a rigid lid. Trapped modes correspond to time harmonic oscillations with finite energy of the fluid surrounding a submerged structure and can be found as eigenfunctions of a certain spectral boundary-value problem. Our main result is a geometric condition relating the cross sections of the submerged parts of the obstacles and the line integrals along the parts of the interfaces pierced by the obstacles and guaranteeing the existence of trapped modes: This follows from variational techniques applied to a suitable operator formulation of the problem. Several examples of structures (piercing or not the interfaces between the fluid layers) satisfying the condition and supporting trapped modes are given.
- Neurodegeneration and choroidal vascular features on OCT in the progression to advanced age-related macular degenerationPublication . Costa, Inês; Carvalho, Ana; Andrade, Helton; Pereira, Bruno; Camacho, PedroAim: To quantify and compare longitudinal thickness changes of the ganglion cell complex (GCC) and the choroid in patients with different patterns of age-related macular degeneration (AMD) progression. Methods: Retrospective cohort analysis of anonymized data from participants aged 50y or more and diagnosed with early/intermediate AMD in at least one eye (with no evidence of advanced AMD). A total of 64 participants were included from the Instituto de Retina de Lisboa (IRL) study (IPL/2022/MetAllAMD_ESTeSL) and divided into 4 groups according to the Rotterdam classification for AMD. Spectral-domain optical coherence tomography (SD-OCT) was used to assess and quantify GCC and choroid thickness at two-time points (first visit vs last visit) with a minimum interval of 3y. Results: In the GCC inner ring, a thinner thickness (P=0.001) was observed in the atrophic AMD group (51.3±21.4 µm) compared to the early AMD (84.3±11.5 µm), intermediate AMD (77.6±16.1 µm) and neovascular AMD (88.9±16.3 µm) groups. Choroidal thickness quantification showed a generalized reduction in the central circle (P=0.002) and inner ring (P=0.001). Slight reductions in retinal thickness were more accentuated in the inner ring in the atrophic AMD (-13%; P<0.01). Conclusion: The variation of the analyzed structures could be an indicator of the risk of progression with neurodegenerative (GCC) or vascular (choroid) patterns in the intermediate and atrophic AMD. The quantification of both structures can provide important information about the risk of disease progression in the early and intermediate stages but also for the evolution pattern into late stages (atrophic or neovascular).
- DNA methyltransferase expression (DNMT1, DNMT3a, and DNMT3b) as a potential biomarker in age-related macular degenerationPublication . Camacho, Pedro; Ribeiro, Edna; Pereira, Bruno; Nascimento, João; Rosa, Paulo Caldeira; Henriques, José; Barrão, Sandra; Sadio, Silvia; Quendera, Bruno; Delgadinho, Mariana; Ginete, Catarina; Neves Delgadinho, Mariana Isabel; Honrado Ginete, Ana Catarina; Silva, Carina; Brito, MiguelBackground/Objectives: Age-related macular degeneration (AMD) is a global cause of vision loss, with limited therapeutic options highlighting the need for effective biomarkers. This study aimed to characterize plasma DNA methyltransferase expression (DNMT1, DNMT3A, and DNMT3B) in AMD patients and explore divergent expression patterns across different stages of AMD. Methods: Thirty-eight AMD patients were prospectively enrolled and stratified by disease severity: eAMD, iAMD, nAMD, and aAMD. Comprehensive ophthalmological assessments included best-corrected visual acuity, digital color fundus photographs, and Spectral Domain Optical Coherence Tomography. Peripheral blood samples were collected for RNA extraction and qRT-PCR to access epigenetic effectors’ transcriptional expression, namely DNMT1, DNMT3A, and DNMT3B genes. The collected data were analyzed using IBM SPSS 29. Results: DNMT1 expression was significantly downregulated in late AMD (−0.186 ± 0.341) compared to early/intermediate AMD (0.026 ± 0.246). Within late AMD, aAMD exhibited a marked downregulation of DNMT1 (−0.375 ± 0.047) compared to nAMD (0.129 ± 0.392). DNMT3A and DNMT3B showed similar divergent expression patterns, correlating with disease stage. Conclusions: This study identified stage-specific transcriptional differences in DNMT expression, emphasizing its potential as a biomarker for AMD progression and a target for future research into personalized therapeutic strategies.
- Comparative analysis of age-related macular degeneration progression in diabetic and non-diabetic patientsPublication . Pinto, Ana Filipa; Franco, Carolina; Gonçalves, Inês; Pereira, Bruno; Camacho, PedroABSTRACT: Introduction: With increasing life expectancy and the rising prevalence of Age-related Macular Degeneration (AMD), one of the leading causes of blindness, a deeper understanding of its pathophysiology is essential to enhance prevention, diagnosis, and treatment. Objective: To compare AMD progression in patients with and without Type 2 Diabetes Mellitus (T2DM) and evaluate vascular and neurodegenerative markers using spectral-domain optical coherence tomography (SD-OCT) during the follow-up period. Methods: In this retrospective cohort study, 67 AMD patients were included (13 with T2DM and 54 without T2DM). The progression patterns of AMD were analyzed and described. SD-OCT was employed to measure and quantify the thickness of the retina, ganglion cell complex (GCC), and choroid at two time points: the initial visit (V0) and the final visit (V1), with a minimum interval of three years. Results: In AMD patients without T2DM (mean age 82.81 ± 6.46 years), a reduction in total retinal thickness was observed across all three ETDRS rings. In contrast, AMD patients with T2DM exhibited no significant changes in retinal thickness during the follow-up period (p > 0.05). Regarding total GCC thickness, AMD patients without T2DM showed a significant decrease across all three ETDRS rings (p < 0.001), a change not observed in AMD patients with T2DM (p > 0.05). Conclusions: Both AMD patient groups, with and without T2DM, demonstrated significant variations in choroidal thickness over the study period. The distinct patterns of thickness variation between the groups suggest a possible influence of diabetes mellitus and its treatment on AMD progression.
- Trabalho por turnos em profissionais de saúde: como minimizar o impacto negativoPublication . Moreira, Ana Catarina; Silva, Ana Lúcia; Pereira, Bruno; Barrigas, Carlos; Ginete, Catarina; Belo, Joana; Mendes, Lino; Nunes, Patrícia Almeida; Camacho, Pedro; Pitta-Grós, Mónica; Santos, Zélia; Pinto, Ana BeatrizEbook desenvolvido no âmbito do projeto de investigação «Crononutrição e padrão de sono em profissionais de saúde com trabalho por turnos». Índice: ritmo circadiano; alimentação no trabalho por turnos noturnos; atividade física no trabalho por turnos noturnos; padrão de sono; influência da exposição a diferentes fontes de luz.
- Thickness profile of the ganglion cell complex and choroid in patients with persistent diabetic macular edemaPublication . Condelipes, Ana; Correia, Daniela; Fernandes, Inês; Silva, Tiago; Correia, Eduardo; Pereira, Bruno; Camacho, PedroPurpose: Approximately 40% of patients with diabetic macular edema (DME) do not respond optimally to first-line treatment with intravitreal injections of anti-vascular endothelial growth factor (VEGF). Evidence suggests that additional vascular and neurodegenerative mechanisms may be involved. This study aimed to characterise the thickness of the Ganglion Cell Complex (GCC) and investigate the Choroidal Vascularity Index (CVI) in patients with different patterns of therapeutic response to AVEGF DME. Methods: This cross-sectional study included 27 diabetic patients divided into three groups based on their response to AVEGF therapy: a control group, a responder DME group, and a persistent DME group. The study's approach to vascular and neurodegenerative imaging biomarkers involved three steps: (1) Automatic quantification of GCC thickness, with manual correction when necessary; (2) Semi-automatic measurement of choroidal thickness; and (3) Analysis of choroidal area and choroidal luminal area using ImageJ software to calculate the CVI. Results: In the overall characterization of the sample, a significant difference was observed only in the Best Corrected Visual Acuity (BCVA). There was a significant difference in Average Retinal Thickness (1 mm, 3 mm, and 6 mm) between the 3 groups and in GCC thickness at 1 mm. BCVA was negatively correlated with mean retinal thickness, while CVI showed a potential positive correlation with BCVA. Conclusions: While demographic and general clinical characteristics showed minimal differences across the groups, important differences in GCC and choroidal characteristics were observed. GCC (1 mm) may be interesting to explore in predicting visual outcomes after treatment, and CVI may impact visual gain.