Archives: Projects/Publication

One-year follow-up of blood retinal barrier and retinal thickness alterations in patients with type 2 diabetes mellitus and mild nonproliferative retinopathy

Lobo C., Bernardes R., Faria de Abreu J., Cunha-Vaz J.

Objective: To examine the 1-year alterations of the blood-retinal barrier and changes in retinal thickness occurring in the macular region in patients with type 2 diabetes mellitus and mild nonproliferative retinopathy.

Methods: We classified 12 eyes of 12 patients with type 2 diabetes mellitus and mild nonproliferative retinopathy by 7-field stereoscopic fundus photography, levels 20 and 35 of Wisconsin grading, and examined them 3 times, at 6-month intervals, by fluorescein angiography, retinal leakage analyzer (RLA) ( modified confocal scanning laser ophthalmoscope), and retinal thickness analyzer. The maps of retinal leakage and retinal thickness were aligned and integrated into one image. Data from the group of individuals with diabetes were compared with those from a healthy control population (n=14; mean age, 48 years; age range, 42-55 years) to establish reference maps for the RLA and the retinal thickness analyzer.

Results: Areas of abnormally increased fluorescein sodium leakage and increased thickness were detected in all eyes examined at baseline. The sites of increased fluorescein leakage reached values as high as 483% above normal, but in 10 of the total 36 examinations performed, fluorescein leakage returned to normal levels. A statistically significant correlation was found between changes in hemoglobin A1c values and variations in percentage of abnormal fluorescein leakage between the 6- and 12-month examinations (P<.001). When comparing the RLA-leaking sites among the 3 examinations, a good correlation was seen among the location of these sites of maximumleakage, but there was a clear fluctuation in the percentage of increases. A correlation was noted between the location of the RLA-leaking sites and the location of areas
of increased retinal thickness in subsequent examinations, either 6 or 12 months later. Microaneurysms showed relatively little leakage and leaked progressively less in successive examinations.

Conclusions: The dominant alteration in the retina of patients with type 2 diabetes mellitus and mild nonproliferative retinopathy is the presence of RLA-leaking sites, indicating spotty retinal vascular damage characterized by alteration of the blood-retinal barrier. This damage appears to be reversible and directly associated with variations in glycemic metabolic control. Retinal edema appears to develop mainly as a result of retinal vascular leakage.

Arch. Ophthalmol. 2001; 119: 1469-1474.

2001
http://cat.inist.fr/?aModele=afficheN&cpsidt=14102170

Alterations of the blood-retinal barrier and retinal thickness in preclinical retinopathy in subjects with type 2 diabetes.

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

Objective: To identify alterations of the blood-retinal barrier by mapping retinal fluorescein leakage into the vitreous and changes in retinal thickness occurring in the macular region in preclinical diabetic retinopathy.

Methods: Ten eyes from 10 patients with type 2 diabetes and no lesions visible on fundus photography (level 10 of Wisconsin grading) were examined with the retinal leakage analyzer (RLA) (Confocal Scanning Laser Ophthalmoscope [modified]; Carl Zeiss Inc, Thornwood, NY) and the retinal thickness analyzer (RTA) (Talia Technology, Mevaseret Zion, Israel). The maps of retinal leakage and retinal thickness were aligned and integrated in the same image to correlate leakage with thickness. Data from the group of individuals with diabetes were compared with those of a healthy control population (N = 14; mean age, 48 years; range, 42-55 years) and used to establish reference maps for the RLA and RTA.

Results: Areas of abnormally increased fluorescein leakage were detected in 9 of 10 eyes examined. The increased leakage in 6 (67%) of 9 eyes reached values higher than 40% more than the mean +2 SD RLA control value. Areas of abnormally increased thickness were found in 7 of 10 eyes examined. For the most part, the increases in retinal thickness were not severe (ie, <15% increase in 5 eyes and an 18% increase in 1 eye). The eyes with the most extensive leakage (cases 1, 3, and 9) showed relatively good coincidence between the location of the areas of increased leakage and the location of the areas of increased thickness. In 4 eyes (cases 2, 5, 7, and 8), no such correlation was apparent. The 3 remaining eyes showed little coincidence between these locations. Characteristically, the latter 3 eyes had areas of abnormally increased thickness that were much larger than the areas of increased fluorescein leakage, which were relatively moderate or absent of any leakage.

Conclusions: Localized sites of increased fluorescein leakage and zones of increased retinal thickness were found in most eyes in a series of 10 eyes in the preretinopathy stage from 10 patients with type 2 diabetes. Increases in retinal thickness may be observed that do not coincide with sites of retinal leakage. Two types of increased retinal thickness may, therefore, be present in the preretinopathy stage of diabetic retinopathy, one directly associated with an alteration of the blood-retinal barrier, and another occurring without apparent breakdown of blood-retinal barrier.

Arch. Ophthalmol. 2000; 118: 1364-1369.

2000
http://archopht.ama-assn.org/cgi/content/abstract/118/10/1364?ck=nck

Mapping retinal fluorescein leakage with confocal scanning laser fluorometry of the human vitreous.

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

Objective: To demonstrate an objective, quantitative, and sensitive method of mapping retinal fluorescein leakage into the vitreous while simultaneously imaging the retina.

Methods: A prototype Zeiss confocal scanning laser ophthalmoscope was modified to obtain fluorometric measurements from 18 optical planes across the retina and cortical vitreous, separated from each other by 150 µm, and parallel to the retinal surface. After intravenous administration of fluorescein, an axial graphic of equivalent fluorescein concentration in the vitreous may be obtained from any region of interest. After correcting for fluorescence levels in the retina and choroid and plasma levels of free fluorescein, permeability values of the blood-retinal barrier to fluorescein were obtained from 1512 regions measuring 75 x 75 µm, from a total 3150 x 2700-µm area of the fundus, generating a detailed map of retinal fluorescein leakage. The method was assessed in vitro and in 7 healthy subjects who underwent scans during separate visits. Depth resolution and influence of chorioretinal fluorescence were further tested in 2 patients with multiple drusen and in 2 eyes after vitrectomy. Fourteen eyes from 7 patients with diabetes and nonproliferative retinopathy were also examined. Lateral resolution was tested in 3 diabetic eyes that underwent focal photocoagulation. Four eyes from 2 patients with diabetes and minimal retinopathy were examined at 3-month intervals. All eyes examined had less than 2 diopters of astigmatism.

Results: Characteristics of the modified confocal scanning laser fluorometer included a lower limit of detection equal to 0.40 Eq ng/mL and depth precision of ±15 µm. Values for the blood-retinal barrier permeability index in healthy subjects, measured 30 minutes after a single intravenous pulse of fluorescein (14 mg/kg), ranged from 1.3 ± 0.4 x 10^-6 cm/s over the foveal avascular zone to 2.2 ± 0.6 x 10^-6 cm/s over vessels in the retina. Diabetic eyes with retinopathy showed higher values, ranging from 1.4 to 15.0 x 10^-6 cm/s. Vitrectomized eyes and eyes with multiple drusen showed the validity of the correction algorithm demonstrating that measurements of fluorescence in the vitreous are not influenced by the chorioretinal fluorescence level. Argon laser photocoagulation burns placed in the diabetic retina demonstrated a lateral resolution on the order of 75 to 100 µm. Intravisit and intervisit reproducibility was ±10.2% and ±13%, respectively.

Conclusions: This new method measures localized alterations of the blood-retinal barrier and allows for direct correlation with retinal anatomy. Its most interesting feature is the ability to map retinal fluorescein leakage while simultaneously imaging the retina. This capability is expected to improve our understanding and management of retinal disease.

Arch. Ophthalmol. 1999; 117: 631-637.

1999
http://archopht.ama-assn.org/cgi/content/abstract/117/5/631

Novel imaging techniques for diabetic macular edema.

Lobo C., Bernardes R., Faria de Abreu J., Cunha-Vaz J.

Retinal edema should be defined as any increase of water of the retinal tissue resulting in an increase in its volume. It may be of cytotoxic or vasogenic origin. Development of vasogenic macular edema is dependent on a series of factors such as blood pressure, blood-retinal barrier permeability, retinal cell damage, retinal tissue osmotic pressure and retinal tissue compliance. Objective measurements of retinal thickness are now possible using the Retinal Thickness Analyser. Localised measurements of blood-retinal barrier permeability may also be obtained using the Retinal Leakage Analyser, a modified confocal scanning laser fluorometer, while obtaining simultaneously angiographic images of the choroid and retina. These new imaging techniques show that cytotoxic and vasogenic retinal edema may occur independently in the early stages of diabetic retinopathy. These findings offer new perpectives for designing novel therapeutic strategies.

Doc. Ophthalmol. 1999, 97: 341-347.

1999
http://www.springerlink.com/content/j312550q01605608/