The effect of pregnancy on mild diabetic retinopathy.

PURPOSE: To study microaneurysm (MA) formation and disappearance rates during pregnancy and postpartum in diabetic women with mild diabetic retinopathy. METHODS: Red-free photographs were taken at the 12th, 24th and 32nd-36th weeks of pregnancy and 3 and 6 months postpartum from 21 type 1 diabetics with mild diabetic retinopathy. In a subset of 13 patients follow-up was continued until 1 year after pregnancy. Fundus photographs were analysed using a computer-assisted fundus lesion localization system. RESULTS: In the whole material the total MA count was 3.1 +/- 3.6 (mean +/- SD) at the 12th week, 3.4 +/- 3.1 at the 24th week, 4.1 +/- 4.9 at the 32nd-36th week, 5.4 +/- 6.2 at 3 months postpartum and 5.2 +/- 5.8 at 6 months postpartum. We found that MA count increased during pregnancy, but it was highest 3 months postpartum. Both the rate of MA formation and the rate of MA disappearance increased during pregnancy, with the disappearance rate exceeding the formation rate 6 months postpartum. In patients having mean HbA1c levels below the median value of 6.38 mmol/l there was a flare-up of MAs during pregnancy, levelling by 3 months postpartum. Patients with a higher than the median (0.76 mmol/l) decrease in HbA1c level compared to pre-pregnancy HbA1c also developed more MAs during the course of pregnancy. CONCLUSIONS: These data suggest that there is continuous turnover of MAs during pregnancy. MA count increases during pregnancy but the MA count was highest 3 months postpartum, after which the formation rate started to decline. Temporary aggravation of mild retinopathy occurs in diabetic patients after normalization of blood glucose levels.

Contrast sensitivity in diabetic pregnancy.

PURPOSE: To evaluate the correlation between the changes in contrast sensitivity and retinopathy throughout pregnancy in diabetic women with mild background diabetic retinopathy. METHODS: Contrast sensitivity (Vistech 6500 Contrast Test System) was measured in 22 type I diabetic women with mild background retinopathy [0-16 microaneurysms (MAs)/eye and occasional small intraretinal hemorrhages] and 10 healthy pregnant women at the 12th and 32nd weeks of pregnancy and 3 months after delivery. Red-free fundus photography was also performed at all visits. RESULTS: Throughout pregnancy contrast sensitivity was lower in the diabetics than in the controls at 1.5, 3.0, and 6.0 cycles per degree (cpd). During the course of pregnancy, contrast sensitivity decreased at 1.5 and 6.0 cpd in patients with more than five new MAs compared to those with fewer than five new MAs during pregnancy. Likewise, contrast sensitivity decreased at 6 cpd in patients with an increase in MA count during pregnancy and at 6 and 12 cpd in patients with a baseline MA count of two or more MAs. CONCLUSIONS: Contrast sensitivity, especially at low to mid-range spatial frequencies, is decreased in diabetic women with mild retinopathy. Even small changes in retinopathy are reflected in a decrease in contrast sensitivity during and after pregnancy. Thus, contrast sensitivity seems to be a sensitive indicator of changes in minimal background retinopathy.

Early versus late staining of microaneurysms in fluorescein angiography.

PURPOSE: To analyze the appearance and disappearance of microaneurysms in different phases of fluorescein angiography. METHODS: Three fluorescein angiograms were taken at 13-month intervals during a 26-month follow-up period from 13 patients with type I diabetes and mild background retinopathy. Two frames of the angiogram were analyzed: one from the transit phase and the other from the late phase of the angiogram. Individual microaneurysms were identified and localized from each frame using a computerized system for retrieval of the coordinates for each microaneurysm. Microaneurysms identified by their location then were analyzed in relation to the phase of the angiogram in which they were visualized and their disappearance during follow-up study. RESULTS: Thirty-three percent of the microaneurysms were visualized only in the early phase, 31% in only the late phase, and 36% in both phases of the fluorescein angiogram. The microaneurysms frequently changed their phase of appearance in the angiogram during follow-up study. CONCLUSION: During the 26-month follow-up period, between 55% and 80% of the microaneurysms present at baseline disappeared. The phase of the baseline angiogram in which the microaneurysms were visualized did not determine their disappearance rate.

Macular blood flow during pregnancy in patients with early diabetic retinopathy measured by blue-field entoptic simulation.

PURPOSE: To study macular capillary blood flow velocity during pregnancy and postpartum in diabetic women with minimal diabetic retinopathy. METHODS: Macular capillary blood velocity was measured using the blue-field entoptic simulation technique in 17 type I diabetic pregnant women with minimal background retinopathy and 10 healthy pregnant women at the 12th and 32nd-36th weeks of pregnancy and 3 months after delivery. Red-free fundus photography was also performed at all visits. RESULTS: Capillary blood velocities at the 12th week of pregnancy were 1.09 +/- 0.37 mm/s in the diabetic women and 0.81 +/- 0.21 mm/s in the controls(P = 0.017), at the 32nd week 0.93 +/- 0.19 mm/s and 0.94 +/- 0.24 mm/s (P = 0.880), and 3 months postpartum 0.98 +/- 0.25 mm/s and 0.75 +/- 0.17 mm/s (P = 0.016), respectively. Analysis of variance indicated that there was a significant difference in leukocyte velocities during the course of pregnancy, with the flow being constantly elevated in diabetic women, but increasing by term in nondiabetic women (P = 0.039). Capillary flow velocity showed a statistically non-significant tendency to be higher in patients with HbA1c levels > 6.4%. Capillary flow velocity levels were not connected with changes in the number of microaneurysms. Capillary leukocyte density in the pregnant diabetic women did not differ from that of nondiabetic pregnant women. CONCLUSIONS: These data suggest that during pregnancy there is a difference in retinal capillary blood flow between diabetic women with minimal background retinopathy and normal women. The lack of increase in blood flow in macular capillaries during diabetic pregnancy may reflect redistribution of retinal capillary flow during diabetic pregnancy or be due to altered rheological properties of blood components in diabetic pregnancy.

Identification of individual microaneurysms: a comparison between fluorescein angiograms and red-free and colour photographs.

PURPOSE: To evaluate how often a microaneurysm (MA) seen in a fluorescein angiogram (FAG) is visualized in colour or red-free photographs, and conversely how often a red dot seen in a colour photograph or a red-free photograph is found in an FAG as an MA. METHOD: Sixty-degree FAGs, colour photographs and red free fundus photographs of 24 patients with mild background retinopathy were analysed using a computer-assisted fundus lesion localization system. Only lesions identified similarly in two separate sessions were processed further. The presence of lesions identified by their position was compared in FAGs and colour and red-free photographs. RESULTS: In the whole material 394 MAs were detected in FAGs, 95 in red-free and 62 in colour photographs. Of the MAs in FAGs 26 (6.6%) were seen as a red dot in a colour photograph and 52 (13%) were found in red-free photographs. Of the 95 MAs found in red-free images 52 (55%) were detected in FAGs. Of the 62 MAs in colour photographs, 26 (42%) were seen as a MA in a FAG. A significant correlation existed between MA counts in FAGs and red dot counts in colour or red-free photographs of individual patients. CONCLUSIONS: Although MAs in FAG and red spots in colour or red-free photographs all reflect the degree of retinopathy, about half of the red dots in photographs do not represent open MAs in FAGs.

Disappearance and formation rates of microaneurysms in early diabetic retinopathy.

AIM: To analyse the formation and disappearance rates of individual microaneurysms in mild background retinopathy. METHODS: Three fluorescein angiograms were taken at 1 year intervals during a 2 year follow up from 24 type 1 diabetics with mild background retinopathy. Microaneurysms were identified and localised twice from each angiogram using a computerised system for retrieval of the coordinates for each microaneurysm. Microaneurysms identified similarly in both sessions were then processed further to obtain rates of microaneurysm formation and disappearance, and microaneurysm count changes. RESULTS: In the whole material the total number of microaneurysms increased from 298 to 436 from baseline to 2 years. During the 2 year follow up 395 new microaneurysms formed and 258 microaneurysms disappeared. Of the microaneurysms present at baseline 174 (58%) were still present at the 1 year and 142 (48%) at the 2 year follow up. In patients with good glucose control (HbA1c < or = 7.5 mmol) microaneurysm formation showed a trend of being decreased whereas microaneurysm disappearance did not correlate with glucose control. CONCLUSION: Background diabetic retinopathy is a dynamic process. A significant proportion of microaneurysms present disappear within 2 years. This is compensated for by formation of new microaneurysms, the resultant net changes in microaneurysm counts being small. Microaneurysm formation and disappearance rates are new variables of diabetic retinopathy and may prove to be more sensitive indicators of the progression patterns of background diabetic retinopathy than microaneurysm count changes.

A computerized system for localization of diabetic lesions from fundus images.

A computerized system for the localization of diabetic lesions from fundus photographs is described. The coordinates for each lesion in relation to reference points are determined from fundus images projected on a digitizing table. The program accepts some variation in coordinates for a single lesion, still to be recorded as the same lesion in a series of photographs, and the magnitude of this variation is adjustable. The data obtained from the localization program are transferred to a register program yielding the following parameters: number of lesions, new lesions, lost lesions, variable lesions, time of presence for lost lesions. These data can be further exported into Microsoft Excel 4, for analysis of large patient materials. An intra-observer error of 0% and an inter-observer error of 1.1% was found in localization of lesions from fundus images. The program was insensitive to small variations in the fundus pictures, but comparisons of 30 degrees and 60 degrees photographs of the same fundus, or 20 degrees deviation of gaze, induced identification errors in 2.9% and 11.9% of localizations, respectively. With this system new parameters on diabetic fundus images can be obtained. The significance of these parameters in the progression of diabetic retinopathy will be analyzed in further studies.