Archives: Projects/Publication

New instrumentation for blood-retinal barrier permeability analysis.

Bernardes R., Lobo C., Dias J., Cunha-Vaz J.

The aim of the work herein presented is to assess the blood-retinal barrier (BRB) of the human eye in vivo. In order to quantitatively evaluate the BRB function, a confocal scanning laser ophthaimoscope instrument was used. The instrument was changed from the basic instrument to increase confocality and to change the starting plane of acquisition after focusing on the patient retinal surface. After a complete scan, a volumetric image of 32 confocal planes of 256 by 256 pixels of 1 byte in width is processed in four steps. The full procedure described permits us to compute the total amount of fluorescein that penetrates into the human vitreous after intravenous administration of dye. A single scan is required for the whole procedure. This new system allows for better identification of the central leaking sites in diabetes, showing well their relationship with the retinal vasculature.

The 2nd European Medical & Biological Engineering Conference (EMBEC’02), Vienna, Austria, December 4-8, 2002, Proc Vol 2, 994-995.

2002

Reproducibility of HRF.

Ludovico J., Pires I., Bernardes R., Lobo C., Cunha-Vaz, J.

Objectivos: Avaliar a reproductibilidade intra-observador das medicões do fluxo sanguíneo da retina com o “Scanning Laser Doppler Flowmeter” (SLDF) (Heidelberg Engineering. Heidelberg, Germany) nas fases iniciais da retinopatia diabética e em sujeitos normais, com diferentes janelas de medicão, na área macular. Medições do fluxo sanguíneo foram feitas em três sessões independentes, em 8 olhos de 8 doentes com retinopatia diabética (Wisconsin 10), e em 8 olhos do indivíduos normais. A quantificação do volume, fluxo e velocidade sanguíneos foi realizada em áreas seleccionadas da macula, utilizando uma janela de 10 x 10 (em três pontos diferentes) em varrimento completo. O coeficiente de variação foi determinado pelo quociente entre o desvio padrão e a média.

Resultados: o coeficiente de variação com o “software” original do HRF (janela 10 x 10) foi: volume – 10,74%, fluxo – 13,69%, velocidade – 12.14%. Com a versão 3.4.0 do HRF (janela de 10 x 10) foi: volume – 14.29%, fluxo – 29.64%,
velocidade – 28,14%. Com a análise do varrimento completo os resultados foram: volume – 4,87%, fluxo – 6,3%, velocidade – 5.05%.

Conclusões: o SLDF permite medicões reproductíveis da perfusão sanguínea do tecido retiniano utilizando a avaliação do varrimento com composto.

Exp. Ophtalmol. 2001, 27/1- 2, 7-11.

2001

Measuring retinal fluorescein leakage into the human vitreous with a modified confocal scanning laser ophthalmoscope.

Bernardes R., Isidoro J., Simões P., Lobo C., Cunha-Vaz J.

A method is described to quantify blood-retinal barrier permeability to fluorescein. Data is collected from the vitreous of the human eye at two elapsed time intervals after intravenous fluorescein administration, using a modified confocal scanning laser ophthalmoscope. Data processing includes fundus image enhancement, image alignment, profile construction, profile filtering and interpolation, exponential fit and integration. Automatic determination of the center of fovea is obtained by a correlation process. Grid overlapping on fundus images and permeability maps allows for matching chorioretinal morphological structures with alterations of blood -retinal barrier permeability to fluorescein.

Proceedings of the European Society of Engineering and Medicine. 1999, 5: 181-182.

1999

Retinal leakage analyzer.

Lobo C., Cunha-Vaz, J., Bernardes R.

Int. J. Metabol. 1999; 2:87-88.

1999

Measuring retinal fluorescein leakage into the human vitreous with a modified confocal scanning laser ophthalmoscope.

Bernardes R., Lobo C., Cunha-Vaz J.

Revista do DETUA. 2000; 3: 180-186.

2000

Evaluation of blood-retinal barrier function from fourier domain high definition optical coherence tomography.

Bernardes R., Santos T., Cunha-Vaz J.

Proceedings of 25/XI IFMBE 2009, World Congress on Medical Physics and Biomedical Engineering, September 7-12, 2009, Munich, Germany.

2009

Computer-assisted microaneurysm turnover in the early stages of diabetic retinopathy.

Bernardes R., Nunes S., Pereira I., Torrent T., Rosa A., Coelho D., Cunha-Vaz J.

Purpose: To assess the reliability of microaneurysm turnover, computed from color fundus photographs, in evaluating diabetic retinopathy in patients with type 2 diabetes and nonproliferative retinopathy.

Methods: A new method (MA-Tracker) was developed to count microaneurysms by mapping their locations through image co-registration. To compute the reliability of microaneurysm turnover, 3 different graders were asked to earmark microaneurysms on the same set of color fundus photographs.

Results: The total numbers of microaneurysms earmarked in each of 5 visits suggest that microaneurysms remain stable over time (p 0.138). However, an analysis of each microaneurysm showed that only 29.4% remained at the same location. By computing the formation and disappearance rates of microaneurysms (2.3 and 1.7 microaneurysms/year, respectively), a significant turnover of microaneurysms was found.

Conclusions: The formation and disappearance rates of microaneurysms obtained from color fundus photographs using MA-Tracker show very good agreement between different graders, and can be used as indicators of microaneurysm turnover in the initial stages of diabetic retinopathy.

Ophtalmologica, 2009; 223(5):284-291.

2009
http://content.karger.com/ProdukteDB/produkte.asp?Doi=213638

Microaneurysm Turnover Is a Biomarker for Diabetic Retinopathy Progression to Clinically Significant Macular Edema: Findings for Type 2 Diabetics with Nonproliferative Retinopathy.

Nunes S., Pires I., Rosa A., Duarte L., Bernardes R., Cunha-Vaz J.

Purpose: To examine the relationship between microaneurysm turnover (formation rate), using a new semi-automatic method (MA-Tracker) based on color fundus photographs, and diabetic retinopathy (DR) progression to clinically significant macular edema (CSME).

Methods: In total, 113 patients/eyes with nonproliferative DR (NPDR) were followed up every 6 months for 2 years as controls of the DR clinical trials, and by conventional general and ophthalmological care for the next 8 years (over a total of 10 years’ follow-up). Microaneurysm turnover for the 2 first years was computed using the MA-Tracker.

Results: The 17 patients that developed CSME over the 10 years of follow-up presented a microaneurysm formation rate of 9.2 ± 18.2 microaneurysms/year (mean ± SD) during the first 2 years, which was statistically higher than the eyes that did not develop CSME (0.5 ± 1.2 microaneurysms/year, p < 0.001). These 17 patients also presented higher HbA_1C levels at baseline (8.5 ± 1.2%) compared to the patients who did not develop CSME (7.3 ± 1.2%, p = 0.001).

Conclusions: A high microaneurysm formation rate on color fundus photographs appears to be a good biomarker for DR progression to CSME in type 2 diabetic patients with NPDR.

Opthalmologica 2009; 223(5):292-297.

2009
http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=000213639