Albrecht v. Graefes Arch. kIin. exp. Ophchal. 207, 71-76 (1978)
Graefes Archiv Ophthalmologie for klinische Und expericv~entene
(C~)by Springer-Verlag 1978
Vitreous Fluorophotometry and Retinal Blood Flow Studies in Proliferative Retinopathy* Jose G. Cunha-Vaz**, Jose R. Fonseca, and Jose F. Abreu The Department of Ophthalmology, University Hospital, Coimbra, Portugal
Summary. The permeability of the blood-retinal barrier and retinal blood flow were evaluated by two new fluorophotometric methods in a series of patients with proliferative retinopathy, due either to retinal vein occlusion or to diabetes. A breakdown of the blood-retinal barrier and a decrease in retinal blood flow were observed in these patients. The breakdown of the blood-retinal barrier could be quantitated by vitreous fluorophotometry, which revealed very high concentrations of fluorescein in the vitreous after intravenous administration. The decrease in retinal blood flow appeared to be due mainly to appreciable narrowing of the retinal arteriolar vessels.
The recent development of vitreous fluorophotometry [I ], a clinical quantitative method for the study of the permeability of the blood-retinal barrier and of a direct method for estimation of retinal blood flow [2], prompted us to examine the features o f retinal neovascularization so that we might contribute to a better definition o f this finding.
Materials and Methods Vitreous fluorophotometry and measurement of the segmental retinal blood flow were performed using a basically similar slit-lamp fluorophotometer, The apparatus consisted of a model 360 Haag-Streit slit
lamp adapted for a new source of illumination (i 50 W unit), appropriate filters, and a photometric detection system that included photomultiplier tubes, photometers, and a double-beam oscilloscope with storage and camera, which was connected to specialtymodified eyepiecescontaining fiberoptic probes [1, 2]. Addressjbr offprint requests: Dr. Cunha-Vaz, Department of Ophthalmology, University of Itlinois Eye and Ear Infirmary, 1855 West Taylor St., Chicago, Ill. 60612, USA * This study was supported by grants from Instituto National de Investigar Cientifica, Portugal ** International research scholar of Research to Prevent Blindness, Inc., and visiting Professor of Ophthalmology, University of Illinois Eye and Ear Infirmary, Chicago, Illinois
0065-6100/78/0207/0071/$01.20
72
J.G. Cunha-Vaz et al.
Vitreous Fluorophotometry For vitreous fluorophotometry, the modified eyepiece contained a fiberoptic probe 75 x 2,500 Ix in size, with a slit-shaped aperture which was designed so that it could be superimposed on any area of the image of the optical cross section, thus allowing for the measurement of fluorescein concentration in all parts of the eye visible in the ocular of the slit lamp. The recordings were performed one hour after a 5 ml intravenous injection of 20 % sodium fluorescein was administered to the patient. The technique used has been described previously at some length [1].
Measurement of Segmental Retinal Blood Flow For segmental retinal blood flow measurements, the modified eyepiece contained two 150 IXfiberoptic probes that may be superimposed on any area of the image of the optical cross section and connected to two photomultiplier tubes, two photometers, and the double-beam oscilloscope. The sensor tips of the optic probes were at a fixed distance of 0.188 cm in focus simultaneously with the optical section. This distance between the optic probes corresponded to a distance of approximately 0.09 cm on the retina, taking into account the optical effect of the contact lens and the optical power of the objective of the slit lamp used. The time base used was 0.1 s/division. All the measurements were made after proper application of a low-vacuum contact lens on the eye to be examined. The technique involves two steps: the measurement of the blood mean transit time between two points in a retinal arterial branch and the determination of the internal diameter of that retinal arterial branch. To measure the blood mean transit time, the eyepiece with the fiberoptics is rotated so that the two sensor tips are focused on the arterial branch. One milliliter of 20 ~ fluorescein is then injected rapidly through a cannula previously placed in a forearm vein. The passage of fluorescein through the two sites of the arterial branch in focus with the fiberoptic is automatically registered. The mean transit time of the blood between the fixed 0.09 cm in the superior temporal retinal artery is twice the time delay between the responses to the impulse of fluorescein light, which corresponds to the distance between the front edges of the pulses obtained in the storage scope. Fundus fluorescein angiography is performed after a second fluorescein injection. The maximum diameter of the fluorescein column is measured using an ordinary light microscope with a micrometer scale in one ocular.
Measurement of Mean Blood Pressure The patient's blood pressure was recorded by sphygmomanometer and the estimated mean pressure calculated (systolic pressure, plus x 2 diastolic pressure, divided by three).
Supers Only patients with a well-defined diagnosis of proliferative retinopathy, established by ophthalmoscopy, slit-lamp biomicroscopy, and fundus fluorescein angiography, were accepted for this study. Seventeen patients were included in the study and divided in two groups. Group 1 contained 6 patients who had retinal vein occlusion and no evidence of diabetes; g r o u p 2 w a s c o m p o s e d o f 11 d i a b e t i c p a t i e n t s .
Controls Data obtained from normal volunteers and diabetic patients showing various d e g r e e s o f r e t i n a l i n v o l v e m e n t , w h i c h h a v e b e e n p r e v i o u s l y r e p o r t e d [1,3], w e r e u s e d as c o n t r o l s .
Proliferative Retiuopathy
73
Vitreous f l u o r o p h o t o m e t r y values in normal patients increase with age, but the highest value recorded in the posterior vitreous f r o m a series o f 45 n o r m a l patients is 1.5 • 10 -8 g/ml [4]. Retinal blood flow measurements performed in a series o f t e n normal volunteers showed a mean segmental retinal blood flow o f 4.2+_ 0.5 gl/min, a mean arterial transit time o f 0.35+ 0.05 seconds, and a mean arterial diameter o f 184_+ 15 ~t. Diabetic patients showing advanced b a c k g r o u n d retinopathy and m a c u l o p a t h y had a mean segmental retinal blood flow o f 6.4__+ 1.1 gl/min, a mean arterial transit time o f 0.23 + 0.06 seconds, and a mean arterial diameter o f 183 + 18 la. Ten patients were studied.
Results
Vitreous Fluorophotometry All o f the 17 patients examined by vitreous f l u o r o p h o t o m e t r y showed appreciable b r e a k d o w n o f the blood-retinal barrier (Table 1). The values o f fluorescein concentration in the posterior vitreous extended from 3 8 • to 350 • 10- ~ g/ml. Diabetic patients, in general, had higher vitreous f l u o r o p h o t o m etry values than the non diabetic patients. New vessels originating from the optic disc region gave rise to higher values o f fluorescein concentration in the vitreous than peripheral new vessels. The average vitreous f l u o r o p h o t o m e t r y value for optic disc new vessels was 1 8 4 x 1 0 - S g / m l in contrast to that o f 75 x a 0 - S g / m l for patients with only perimacular and peripheral new vessels. The increased vitreous
Table 1. Vitreous fluorophotometry measurements in the posterior vitreous of patients with proliferative retinopathy
Patient No.
Age/Sex
Disease
Fundus fluorescein angiography
Vitreous fluorophotometry ( x 10- 8g/ml)
Vein occlusion Vein occlusion Vein occlusion Vein occlusion Vein occlusion Vein occlusion Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes
Peripheral new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Optic disk new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Optic disk new vessels
40 45 180 38 55 150 80 150 48 200 220 40 70 145 110 120 350
l
47/M
2
41/M
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
52/M 66/M 54/M 64/M 73/F 70/F 55/F 46/M 60/M 63/F 55/F 65/M 38/M 56/F 54/F
74
J.G. Cunha-Vaz et al.
Table 2. Comparison among study groups and controls No.
Mean flow (gl/min) -+ S.D.
Mean arterial transit time(s) _+S.D.
Mean arterial Mean blood diameter (~tm) pressure (mmHg) -+ S.D. _+S.D.
Age (yrs) mean
NormaP
10
4.2+_ 0.5
0.35_+ 0.05
184_+ 15
80_+ 7
23
Advanced diabetic background retinopathy"
10
6.4_+ 1.1
0.23_+ 0.06
183+_ 18
104_+ 19
60
Diabetic proliferative retinopathy
6
4.2_+ 1.1
0.29-+ 0.06
166_+ I4
102_+ 9
61
Nondiabetic proliferative retinopathy
6
3.6+ 0.4
0.35+- 0.05
165_+ 10
112_+ 19
54
Values referred to in previous papers [2, 3]
fluorophotometry values appeared to be related mainly to the extension of the new vessel formation and site of the neovascularization. Some relation was also apparent between higher vitreous fluorophotometry readings and associated hypertension.
Measurements of Segmental Retinal Blood Flow Although optic disc neovascularization can cause problems to the measurement of segmental retinal blood flow by covering the arterial branches near the disc, this study was performed in six diabetic and six non diabetic patients with proliferative retinopathy (Table 2). Non diabetic patients with proliferative retinopathy had a mean segmental arteriolar blood flow of 3.6+0.4gl/min, a mean arteriolar transit time of 0.35_+ 0.05 seconds, and a mean arteriolar diameter of 165_+ 10 ix (Table 2). Using the Student t test to evaluate the significance of the differences between the mean values and those of the normal controls, the following were obtained: mean segmental retinal blood flow, t(14)=2.5; mean transit time, t(14)=0; and mean arterial diameter, t(14)=2.8. Significant differences were found between the mean values of flow (P < 0.025) and arterial diameter (P < 0.01) between normal subjects and patients with non diabetic proliferative retinopathy. No difference was observed in the arteriolar transit times. The six diabetic patients with proliferative retinopathy showed a mean segmental retinal blood flow of 4.2+ 1.1 ~tl/min, a mean transit time of 0.29+__0.06 seconds, and a mean arterial diameter of 166_+ 14 ix(Table 2). Using Student's t test to know the significance of the differences between these mean values and those of the normal controls, the following were obtained: mean segmental retinal blood flow, t(1~)=0.05; mean transit time, tur and mean arterial diameter, t(,+) = 2.3, No significance was found between the mean values of flow in normal subjects and those of patients with proliferative diabetic retinopathy. There were, however, highly significant differences between the values of transit time (P < 0.001) and arterial diameter (P < 0.025).
ProliferativeRetinopathy
75
Using the Student t test to determine the significance of the differences between the mean values obtained in patients with diabetic proliferative retinopathy and those of diabetic patients showing advanced background retinopathy but without neovascularization, as previously referred to in the controls, the following values were obtained: mean segmental retinal blood flow, t~14~= 3.9; mean transit time, t~l4~= 2; and mean arterial diameter, t(1~ = 1.97. A significant difference was found between the values of segmental retinal blood flow (P< 0.025) between diabetic patients with advanced retinopathy but without neovascularization. The difference in retinal blood flow appeared to be due to a decrease in transit time and arterial occlusion. Comment
Evidence of retinal neovascularization in human diseases has been described in retinal vein occlusion, sickle cell disease, Eales' disease, diabetic retinopathy, sarcoidosis, pulseless disease, and retrolental fibroplasia [5]. Proliferative retinopathy appears, therefore, to be associated with diseases showing an apparent impediment to blood flow. Another important feature of retinal neovascularization is the abnormal permeability of the vessels, a feature that has been well demonstrated with fluorescein angiography. The application of vitreous fluorophotometry in proliferative retinopathy showed very high concentrations of fluorescein in the vitreous as a result of the associated alteration of the blood-retinal barrier. In general, the higher vitreous fluorophotometry values registered in diabetic eyes, as compared with non diabetic eyes, appeared to be the result of more extensive areas of neovascularization and related widespread retinal vascular disease, which is associated with breakdown of the blood-retinal barrier. Vitreous fluorophotometry, therefore, appears capable of quantitating the fluorescein leakage that is associated with retinal new vessel formation. This opens interesting possibilities for evaluating the treatment of this much dreaded complication of retinal vascular disease. Further studies are being pursued, whereby patients with proliferative retinopathy who are being considered for photocoagulation treatment are having vitreous fluorophotometry examinations before and after treatment. Retinal blood flow studies in proliferative retinopathy were performed in six diabetic patients, and the results compared with values obtained from normal volunteers and from patients with advanced diabetic retinopathy but without neovascularization. Retinal blood flow was shown to be significantly decreased in non diabetic patients with proliferative retinopathy as compared with normal individuals. This decrease in retinal blood flow could be related to a profound decrease in retinal arteriolar diameter, for the transit times are similar. Proliferative retinopathy, therefore, appears to be clearly associated with an impediment to blood flow due to progressive occlusion of the retinal arterial vessels. The diabetic patients with proliferative retinopathy showed apparently normal values for retinal blood flow. These values, however, acquired particular meaning when compared to those obtained in diabetic patients with advanced background retinopathy but without new vessel formation. This comparison showed significant
76
J.G. Cunha-Vaz et al.
differences in retinal blood flow, arterial transit time, and arterial diameter. Diabetic patients with proliferative retinopathy exhibited an appreciable decrease in retinal blood flow that was associated with some decrease in transit time and an even more p r o n o u n c e d alteration in arterial diameter, which appeared m u c h narrowed. These results show that in proliferative diabetic retinopathy there is a decrease in blood flow that appears to be due mainly to narrowing o f the retinal arterial vessels. These studies are very m u c h in agreement with the findings reported by K o h n e r in diabetic patients [6]. Her results similarly showed that in the most severe forms of diabetic retinopathy or proliferative retinopathy, the volume flow is relatively decreased. This change was considered to be due to the inability of the diseased vessels to respond to autoregulatory demand.
References Cunha-Vaz, J.G., Abre~, J.R.F., Campos, A.J., Figo, G.: Early breakdown of the blood-retinal barrier in diabetes. Br. J. Ophthalmol. 59, 649-656 (1975) Cunha-Vaz, J.G., Lima, J.J.P. : Studies on retinal blood flow. I. Estimation of human retinal blood flow by slit-lamp fluorophotometry. Arch. Ophthalmol. 96, 893-897 (1978) Cunha-Vaz, J.G., Fonseca, J.R., Abreu, J.R., Lima, J.J.P. : Studies on retinal blood-flow. II. Diabetic retinopathy. Arch. Ophthalmol, 96, 809-811 (1978) Cunha-Vaz, J.G., Fonseca, J.R., Abreu, J.R., Ruas, M.A.: Detection of early retinal involvement in diabetes by vitreous fluorophotometry. Diabetes (submitted for publication) Wise, G.N., Dollery, C.T., Henkind, P.: In the Retinal Circulation. New York: Harper & Row 1977 Kohner, E.: Retinal blood flow in diabetes mellitus. In Diabetic Retinopathy, Lynn, J.R., Snyder, W.B., and Vaiser, A. (eds)., p 71, New York: Grune and Stratton 1974 Received April 4, 1978
Graefes Archiv Ophthalmologie for klinische Und expericv~entene
(C~)by Springer-Verlag 1978
Vitreous Fluorophotometry and Retinal Blood Flow Studies in Proliferative Retinopathy* Jose G. Cunha-Vaz**, Jose R. Fonseca, and Jose F. Abreu The Department of Ophthalmology, University Hospital, Coimbra, Portugal
Summary. The permeability of the blood-retinal barrier and retinal blood flow were evaluated by two new fluorophotometric methods in a series of patients with proliferative retinopathy, due either to retinal vein occlusion or to diabetes. A breakdown of the blood-retinal barrier and a decrease in retinal blood flow were observed in these patients. The breakdown of the blood-retinal barrier could be quantitated by vitreous fluorophotometry, which revealed very high concentrations of fluorescein in the vitreous after intravenous administration. The decrease in retinal blood flow appeared to be due mainly to appreciable narrowing of the retinal arteriolar vessels.
The recent development of vitreous fluorophotometry [I ], a clinical quantitative method for the study of the permeability of the blood-retinal barrier and of a direct method for estimation of retinal blood flow [2], prompted us to examine the features o f retinal neovascularization so that we might contribute to a better definition o f this finding.
Materials and Methods Vitreous fluorophotometry and measurement of the segmental retinal blood flow were performed using a basically similar slit-lamp fluorophotometer, The apparatus consisted of a model 360 Haag-Streit slit
lamp adapted for a new source of illumination (i 50 W unit), appropriate filters, and a photometric detection system that included photomultiplier tubes, photometers, and a double-beam oscilloscope with storage and camera, which was connected to specialtymodified eyepiecescontaining fiberoptic probes [1, 2]. Addressjbr offprint requests: Dr. Cunha-Vaz, Department of Ophthalmology, University of Itlinois Eye and Ear Infirmary, 1855 West Taylor St., Chicago, Ill. 60612, USA * This study was supported by grants from Instituto National de Investigar Cientifica, Portugal ** International research scholar of Research to Prevent Blindness, Inc., and visiting Professor of Ophthalmology, University of Illinois Eye and Ear Infirmary, Chicago, Illinois
0065-6100/78/0207/0071/$01.20
72
J.G. Cunha-Vaz et al.
Vitreous Fluorophotometry For vitreous fluorophotometry, the modified eyepiece contained a fiberoptic probe 75 x 2,500 Ix in size, with a slit-shaped aperture which was designed so that it could be superimposed on any area of the image of the optical cross section, thus allowing for the measurement of fluorescein concentration in all parts of the eye visible in the ocular of the slit lamp. The recordings were performed one hour after a 5 ml intravenous injection of 20 % sodium fluorescein was administered to the patient. The technique used has been described previously at some length [1].
Measurement of Segmental Retinal Blood Flow For segmental retinal blood flow measurements, the modified eyepiece contained two 150 IXfiberoptic probes that may be superimposed on any area of the image of the optical cross section and connected to two photomultiplier tubes, two photometers, and the double-beam oscilloscope. The sensor tips of the optic probes were at a fixed distance of 0.188 cm in focus simultaneously with the optical section. This distance between the optic probes corresponded to a distance of approximately 0.09 cm on the retina, taking into account the optical effect of the contact lens and the optical power of the objective of the slit lamp used. The time base used was 0.1 s/division. All the measurements were made after proper application of a low-vacuum contact lens on the eye to be examined. The technique involves two steps: the measurement of the blood mean transit time between two points in a retinal arterial branch and the determination of the internal diameter of that retinal arterial branch. To measure the blood mean transit time, the eyepiece with the fiberoptics is rotated so that the two sensor tips are focused on the arterial branch. One milliliter of 20 ~ fluorescein is then injected rapidly through a cannula previously placed in a forearm vein. The passage of fluorescein through the two sites of the arterial branch in focus with the fiberoptic is automatically registered. The mean transit time of the blood between the fixed 0.09 cm in the superior temporal retinal artery is twice the time delay between the responses to the impulse of fluorescein light, which corresponds to the distance between the front edges of the pulses obtained in the storage scope. Fundus fluorescein angiography is performed after a second fluorescein injection. The maximum diameter of the fluorescein column is measured using an ordinary light microscope with a micrometer scale in one ocular.
Measurement of Mean Blood Pressure The patient's blood pressure was recorded by sphygmomanometer and the estimated mean pressure calculated (systolic pressure, plus x 2 diastolic pressure, divided by three).
Supers Only patients with a well-defined diagnosis of proliferative retinopathy, established by ophthalmoscopy, slit-lamp biomicroscopy, and fundus fluorescein angiography, were accepted for this study. Seventeen patients were included in the study and divided in two groups. Group 1 contained 6 patients who had retinal vein occlusion and no evidence of diabetes; g r o u p 2 w a s c o m p o s e d o f 11 d i a b e t i c p a t i e n t s .
Controls Data obtained from normal volunteers and diabetic patients showing various d e g r e e s o f r e t i n a l i n v o l v e m e n t , w h i c h h a v e b e e n p r e v i o u s l y r e p o r t e d [1,3], w e r e u s e d as c o n t r o l s .
Proliferative Retiuopathy
73
Vitreous f l u o r o p h o t o m e t r y values in normal patients increase with age, but the highest value recorded in the posterior vitreous f r o m a series o f 45 n o r m a l patients is 1.5 • 10 -8 g/ml [4]. Retinal blood flow measurements performed in a series o f t e n normal volunteers showed a mean segmental retinal blood flow o f 4.2+_ 0.5 gl/min, a mean arterial transit time o f 0.35+ 0.05 seconds, and a mean arterial diameter o f 184_+ 15 ~t. Diabetic patients showing advanced b a c k g r o u n d retinopathy and m a c u l o p a t h y had a mean segmental retinal blood flow o f 6.4__+ 1.1 gl/min, a mean arterial transit time o f 0.23 + 0.06 seconds, and a mean arterial diameter o f 183 + 18 la. Ten patients were studied.
Results
Vitreous Fluorophotometry All o f the 17 patients examined by vitreous f l u o r o p h o t o m e t r y showed appreciable b r e a k d o w n o f the blood-retinal barrier (Table 1). The values o f fluorescein concentration in the posterior vitreous extended from 3 8 • to 350 • 10- ~ g/ml. Diabetic patients, in general, had higher vitreous f l u o r o p h o t o m etry values than the non diabetic patients. New vessels originating from the optic disc region gave rise to higher values o f fluorescein concentration in the vitreous than peripheral new vessels. The average vitreous f l u o r o p h o t o m e t r y value for optic disc new vessels was 1 8 4 x 1 0 - S g / m l in contrast to that o f 75 x a 0 - S g / m l for patients with only perimacular and peripheral new vessels. The increased vitreous
Table 1. Vitreous fluorophotometry measurements in the posterior vitreous of patients with proliferative retinopathy
Patient No.
Age/Sex
Disease
Fundus fluorescein angiography
Vitreous fluorophotometry ( x 10- 8g/ml)
Vein occlusion Vein occlusion Vein occlusion Vein occlusion Vein occlusion Vein occlusion Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes Diabetes
Peripheral new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Optic disk new vessels Peripheral new vessels Optic disk new vessels Peripheral new vessels Peripheral new vessels Optic disk new vessels Optic disk new vessels
40 45 180 38 55 150 80 150 48 200 220 40 70 145 110 120 350
l
47/M
2
41/M
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
52/M 66/M 54/M 64/M 73/F 70/F 55/F 46/M 60/M 63/F 55/F 65/M 38/M 56/F 54/F
74
J.G. Cunha-Vaz et al.
Table 2. Comparison among study groups and controls No.
Mean flow (gl/min) -+ S.D.
Mean arterial transit time(s) _+S.D.
Mean arterial Mean blood diameter (~tm) pressure (mmHg) -+ S.D. _+S.D.
Age (yrs) mean
NormaP
10
4.2+_ 0.5
0.35_+ 0.05
184_+ 15
80_+ 7
23
Advanced diabetic background retinopathy"
10
6.4_+ 1.1
0.23_+ 0.06
183+_ 18
104_+ 19
60
Diabetic proliferative retinopathy
6
4.2_+ 1.1
0.29-+ 0.06
166_+ I4
102_+ 9
61
Nondiabetic proliferative retinopathy
6
3.6+ 0.4
0.35+- 0.05
165_+ 10
112_+ 19
54
Values referred to in previous papers [2, 3]
fluorophotometry values appeared to be related mainly to the extension of the new vessel formation and site of the neovascularization. Some relation was also apparent between higher vitreous fluorophotometry readings and associated hypertension.
Measurements of Segmental Retinal Blood Flow Although optic disc neovascularization can cause problems to the measurement of segmental retinal blood flow by covering the arterial branches near the disc, this study was performed in six diabetic and six non diabetic patients with proliferative retinopathy (Table 2). Non diabetic patients with proliferative retinopathy had a mean segmental arteriolar blood flow of 3.6+0.4gl/min, a mean arteriolar transit time of 0.35_+ 0.05 seconds, and a mean arteriolar diameter of 165_+ 10 ix (Table 2). Using the Student t test to evaluate the significance of the differences between the mean values and those of the normal controls, the following were obtained: mean segmental retinal blood flow, t(14)=2.5; mean transit time, t(14)=0; and mean arterial diameter, t(14)=2.8. Significant differences were found between the mean values of flow (P < 0.025) and arterial diameter (P < 0.01) between normal subjects and patients with non diabetic proliferative retinopathy. No difference was observed in the arteriolar transit times. The six diabetic patients with proliferative retinopathy showed a mean segmental retinal blood flow of 4.2+ 1.1 ~tl/min, a mean transit time of 0.29+__0.06 seconds, and a mean arterial diameter of 166_+ 14 ix(Table 2). Using Student's t test to know the significance of the differences between these mean values and those of the normal controls, the following were obtained: mean segmental retinal blood flow, t(1~)=0.05; mean transit time, tur and mean arterial diameter, t(,+) = 2.3, No significance was found between the mean values of flow in normal subjects and those of patients with proliferative diabetic retinopathy. There were, however, highly significant differences between the values of transit time (P < 0.001) and arterial diameter (P < 0.025).
ProliferativeRetinopathy
75
Using the Student t test to determine the significance of the differences between the mean values obtained in patients with diabetic proliferative retinopathy and those of diabetic patients showing advanced background retinopathy but without neovascularization, as previously referred to in the controls, the following values were obtained: mean segmental retinal blood flow, t~14~= 3.9; mean transit time, t~l4~= 2; and mean arterial diameter, t(1~ = 1.97. A significant difference was found between the values of segmental retinal blood flow (P< 0.025) between diabetic patients with advanced retinopathy but without neovascularization. The difference in retinal blood flow appeared to be due to a decrease in transit time and arterial occlusion. Comment
Evidence of retinal neovascularization in human diseases has been described in retinal vein occlusion, sickle cell disease, Eales' disease, diabetic retinopathy, sarcoidosis, pulseless disease, and retrolental fibroplasia [5]. Proliferative retinopathy appears, therefore, to be associated with diseases showing an apparent impediment to blood flow. Another important feature of retinal neovascularization is the abnormal permeability of the vessels, a feature that has been well demonstrated with fluorescein angiography. The application of vitreous fluorophotometry in proliferative retinopathy showed very high concentrations of fluorescein in the vitreous as a result of the associated alteration of the blood-retinal barrier. In general, the higher vitreous fluorophotometry values registered in diabetic eyes, as compared with non diabetic eyes, appeared to be the result of more extensive areas of neovascularization and related widespread retinal vascular disease, which is associated with breakdown of the blood-retinal barrier. Vitreous fluorophotometry, therefore, appears capable of quantitating the fluorescein leakage that is associated with retinal new vessel formation. This opens interesting possibilities for evaluating the treatment of this much dreaded complication of retinal vascular disease. Further studies are being pursued, whereby patients with proliferative retinopathy who are being considered for photocoagulation treatment are having vitreous fluorophotometry examinations before and after treatment. Retinal blood flow studies in proliferative retinopathy were performed in six diabetic patients, and the results compared with values obtained from normal volunteers and from patients with advanced diabetic retinopathy but without neovascularization. Retinal blood flow was shown to be significantly decreased in non diabetic patients with proliferative retinopathy as compared with normal individuals. This decrease in retinal blood flow could be related to a profound decrease in retinal arteriolar diameter, for the transit times are similar. Proliferative retinopathy, therefore, appears to be clearly associated with an impediment to blood flow due to progressive occlusion of the retinal arterial vessels. The diabetic patients with proliferative retinopathy showed apparently normal values for retinal blood flow. These values, however, acquired particular meaning when compared to those obtained in diabetic patients with advanced background retinopathy but without new vessel formation. This comparison showed significant
76
J.G. Cunha-Vaz et al.
differences in retinal blood flow, arterial transit time, and arterial diameter. Diabetic patients with proliferative retinopathy exhibited an appreciable decrease in retinal blood flow that was associated with some decrease in transit time and an even more p r o n o u n c e d alteration in arterial diameter, which appeared m u c h narrowed. These results show that in proliferative diabetic retinopathy there is a decrease in blood flow that appears to be due mainly to narrowing o f the retinal arterial vessels. These studies are very m u c h in agreement with the findings reported by K o h n e r in diabetic patients [6]. Her results similarly showed that in the most severe forms of diabetic retinopathy or proliferative retinopathy, the volume flow is relatively decreased. This change was considered to be due to the inability of the diseased vessels to respond to autoregulatory demand.
References Cunha-Vaz, J.G., Abre~, J.R.F., Campos, A.J., Figo, G.: Early breakdown of the blood-retinal barrier in diabetes. Br. J. Ophthalmol. 59, 649-656 (1975) Cunha-Vaz, J.G., Lima, J.J.P. : Studies on retinal blood flow. I. Estimation of human retinal blood flow by slit-lamp fluorophotometry. Arch. Ophthalmol. 96, 893-897 (1978) Cunha-Vaz, J.G., Fonseca, J.R., Abreu, J.R., Lima, J.J.P. : Studies on retinal blood-flow. II. Diabetic retinopathy. Arch. Ophthalmol, 96, 809-811 (1978) Cunha-Vaz, J.G., Fonseca, J.R., Abreu, J.R., Ruas, M.A.: Detection of early retinal involvement in diabetes by vitreous fluorophotometry. Diabetes (submitted for publication) Wise, G.N., Dollery, C.T., Henkind, P.: In the Retinal Circulation. New York: Harper & Row 1977 Kohner, E.: Retinal blood flow in diabetes mellitus. In Diabetic Retinopathy, Lynn, J.R., Snyder, W.B., and Vaiser, A. (eds)., p 71, New York: Grune and Stratton 1974 Received April 4, 1978
