Retinopathy in the pregnant diabetic.
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
S H Sinclair
Publications and source records attributed to S H Sinclair.
Blood velocity and volumetric flow rate in human retinal vessels.
The distributions of blood velocity and volumetric flow rate in individual vessels of the normal human retina were determined as a function of vessel diameter. The mean velocity of blood, Vmean, was calculated from the centerline velocity measured by bidirectional laser Doppler velocimetry (LDV). Volumetric flow rate was determined from Vmean and the vessel diameter, D, measured from monochromatic fundus photographs. Diameter of the arteries and veins at the site of the LDV measurements ranged from 39 to 134 microns and 64 to 177 microns, respectively. Flow velocity correlated with D (P less than 0.001 for both arteries and veins). Volumetric flow rate varied with D at a power of 2.76 +/- 0.16 for arteries and 2.84 +/- 0.12 for veins, in close agreement with Murray's law. Calculated from 12 eyes, the average total arterial and venous volumetric flow rates were 33 +/- 9.6 and 34 +/- 6.3 microliters/min, respectively. The good agreement between both flow rates suggests that the technique and the assumptions for calculating flow yield results that satisfy mass conservation. Total arterial and venous volumetric flow rates correlated with total arterial and venous vessel cross-section. Volumetric flow rate in the temporal retina was significantly greater than in the nasal retina, but the difference is likely to be due to the larger area of the temporal retina. No difference in flow rate was observed between the superior and inferior retinal hemispheres. Finally, blood velocity in the major retinal vessels measured under normal experimental conditions appears remarkably constant over short (hours) and long (months) periods of time.
Blood Flow Velocity↗
Macular edema and pregnancy in insulin-dependent diabetes.
Seven women with insulin-dependent diabetes (mean age, 26 years; mean duration of diabetes, 15.4 years) had minimal or no retinopathy before becoming pregnant but developed severe macular edema associated with preproliferative or proliferative retinopathy during the course of their pregnancies. The edema was associated with significant macular capillary nonperfusion, and often with significant proteinuria and mild hypertension. Although proliferation was controlled with panretinal photocoagulation, the macular edema continued to worsen until delivery in all cases and was often aggravated by the photocoagulation. Macular edema and retinopathy both regressed after delivery in some patients but persisted in others, causing significant visual loss. Pregnant women with retinopathy, nephropathy, or hypertension should undergo ophthalmoscopy at least once a month. If proliferative retinopathy develops, panretinal photocoagulation should be applied even if the macular edema is aggravated.
Adult↗
Altered retinal vascular response to 100% oxygen breathing in diabetes mellitus.
The effect of 100% oxygen breathing on retinal blood flow was investigated using laser Doppler velocimetry in 19 normal eyes, and in 41 eyes of insulin treated diabetic patients. Of the diabetic eyes studied, nine had no retinopathy, 18 had background diabetic retinopathy, seven had proliferative diabetic retinopathy, and seven had proliferative diabetic retinopathy that had been previously treated by argon panretinal photocoagulation. Five minutes of 100% oxygen breathing produced an average decrease in blood flow of 61% (SD = 8) in normal eyes, 53% (SD = 10) in NR eyes, 38% (SD = 13) in background diabetic retinopathy eyes, 24% (SD = 18) in proliferative diabetic retinopathy eyes and 54% (SD = 8) in panretinal photocoagulation eyes. In six eyes with proliferative retinopathy measured before and after panretinal photocoagulation, a significant increase in vascular response to O2 was observed following photocoagulation (Wilcoxon signed rank test, P less than 0.05).
Adult↗
Effect of pure O2-breathing on retinal blood flow in normals and in patients with background diabetic retinopathy.
The noninvasive Laser Doppler velocimetry technique was applied in normal volunteers and in patients with background diabetic retinopathy to determine retinal blood flow during pure oxygen breathing at atmospheric pressure. In normal subjects, five minutes of oxygen breathing produced a 63 +/- 6% decrease in retinal blood flow. In the diabetic patients blood flow decreased by only 36 +/- 15%. A significant correlation between the decrease in blood flow and that of the diameter of the veins was found in the diabetic patients. This was not the case for the normal subjects.
Adult↗
Posterior epiretinal neovascularization associated with sectoral retinal ischemia.
Two cases of large, posteriorly located epiretinal neovascular membranes are presented that were associated with a nasal wedge of retinal ischemia of unknown cause in young Caucasian men without associated systemic disease. A technique of staged, argon laser scatter photocoagulation to the ischemic retina resulted in dramatic regression of the neovascular fronds in both cases.
Adult↗
Laser Doppler Velocimetry study of the effect of pure oxygen breathing on retinal blood flow.
The noninvasive Laser Doppler Velocimetry (LDV) technique was used in normal volunteers to determine retinal blood flow, F, during pure oxygen breathing at atmospheric pressure. Changes in blood flow were calculated based on Poiseuille relation, F = (pi D2/4) X Vmax, where Vmax is the red blood cell maximum or center-line velocity and D, the diameter of the vessel at the site of the LDV recordings. After five minutes of pure oxygen breathing, Vmax decreased by about 53%, vessel diameter by 12%, and retinal blood flow by about 60%. In arteries, pulsatility of red blood cell velocity (Vmax, systole/Vmax, diastole) during the cardiac cycle increased by about 10%. Decrease in red blood cell velocity was detectable within 1-1 1/2 min. From these LDV flow measurements and the changes in retinal mean circulation time (MCT) reported by other investigators, based on the relation F = v/MCT, a 45% decrease in retinal blood volume (v) during 100% O2 breathing was obtained.
Adult↗
A pars plana filtering procedure combined with lensectomy and vitrectomy for neovascular for neovascular glaucoma.
In 14 eyes undergoing a pars plana filtration procedure combined with pars plana lensectomy and vitrectomy, the most common complication was a severe sterile fibrinous vitritis. However, after a mean follow-up period of 6.3 months, intraocular pressure was controlled in five eyes (36%) after the procedure alone, in two (14%) after subsequent medical therapy, and in three (21%) after subsequent cyclocryotherapy. Preoperative visual acuity was maintained or improved in nine of the eyes (64%), whereas four eyes (28%) had no light perception.
Cryosurgery↗
Retinal vascular autoregulation in diabetes mellitus.
The blue field entoptic technique was used to study autoregulation of the macular retinal circulation in response to acute alterations of intraocular pressure in 71 diabetic eyes and 30 normals matched for age, systemic blood pressure, and ophthalmic artery diastolic pressure. IOPmax, the maximal intraocular pressure at which flow is maintained normal by autoregulation, was normal in eyes with no retinopathy (30 +/- 3.2 mm Hg) but decreased with progression of retinopathy, approaching the resting intraocular pressure in eyes with proliferative retinopathy. The hyperemia observed by normals to an acute reduction of intraocular pressure was not observed frequently in the diabetics with no retinopathy. The frequency of observation of the hyperemia decreased with progression of retinopathy and was uniformly absent in eyes with proliferative retinopathy. A group of eyes with minimal microangiopathy was found to have an abnormal IOPmax and no hyperemic response. The prognostic significance of these parameters remains to be established.
Adolescent↗
Laser Doppler measurement of relative blood velocity in the human optic nerve head.
The Doppler shift frequency spectrum (DSFS) of laser light scattered from red blood cells (RBCs) moving in the microcirculation of the optic nerve head has been recorded in normal volunteers by means of a fundus camera laser Doppler velocimeter. The width of the DSFS, which varies in proportion to the speed of the RBCs, has been characterized by a parameter alpha. With the use of a model for the scattering of light by tissue and RBCs and for the RBC velocity distribution, values of alpha recorded at normal intraocular pressure (IOP) suggest that the RBCs that contribute to the Doppler signal are flowing in capillaries. The parameter alpha was found to vary markedly with the IOP and with the phase of the ocular pressure pulse at elevated IOP. The return of the speed of RBCs toward normal, which is observed after a step increase of IOP above normal and after a step decrease below normal, has been attributed to an autoregulatory response of the optic nerve circulation.
Blood Flow Velocity↗
Autoregulation of the retinal circulation in response to decrease of intraocular pressure below normal.
The autoregulatory response of the retinal circulation to a short-term reduction in intraocular pressure (IOP) to hypotonic levels was studied in 15 normal subjects by means of the blue-field entoptic phenomenon. This phenomenon allows the perception of the leukocytes flowing in one's own retinal macular capillaries. Subjects were asked to compare the leukocyte speed in one eye with that in the fellow eye while a scleral suction cup was used to raise the IOP in one eye to levels above 25 mm Hg for approximately 12 min. The release of the suction cup caused a drop in IOP to levels between 4 and 7 mm Hg, at which time all subjects reported a higher leukocyte speed (hyperemia) in this eye than in the fellow eye. After an average of 4 min the speed was observed to be equal in both eyes. The average IOP at which the equalization occurred was 6.8 +/- 1.3 mm Hg. The retina can therefore normalize leukocyte capillary speed and presumably blood flow at IOPs at least as low as 6.8 mm Hg. The results of 16 experiments on the same eye of one subject suggest that under these experimental conditions, the lowest IOP for which the retina can fully autoregulate is around 6 to 7 mm Hg.
Adult↗
Blue field entoptic test in patients with ocular trauma.
The blue field entoptic test was applied to study macular function in 32 patients with severe ocular trauma and markedly reduced visual acuity (6/60 [20/200] or less) in whom fundus details could not be seen initially. This test is based on the entoptic phenomenon, whereby one can observe one's own leukocytes flowing in the perifoveal retinal capillaries. Twenty of the 21 patients (95%) with normal perception of the corpuscles regained a visual acuity of 6/12 (20/40) or better on follow-up, whereas ten of the 11 patients (91%) with abnormal test responses had, on follow-up, a visual acuity of counting fingers or less. The blue field entoptic test is therefore useful in prognosticating macular function in patients with reduced visual acuity due to media opacities secondary to ocular trauma.
Adolescent↗
Blue field entoptic phenomenon in amblyopia.
The blue field entoptic phenomenon allows the perception of leukocytes moving in the retinal capillaries of one's own retina. This phenomenon is not affected by media opacities provided that enough blue light reaches the retina. The phenomenon was investigated in 63 amblyopic patients to determine if the perception of the leukocytes in the amblyopic eye differs from that in the good eye. A difference in perception would provide a means of assessing amblyopic in eyes with opaque media. Ninety-four percent of the amblyopic eyes perceived less sharp particles, 83% perceived fewer particles and 60% perceived slower particles than in the good eyes. In 86% of the amblyopic eyes, the tails were shorter than in the good eyes or absent entirely. The degree of amblyopia correlated with the difference in the number of leukocytes observed in each eye. No differences in the perception of leukocytes were reported by 20 normal subjects.
Adolescent↗
Is the pulsating vascular tree entoptic phenomenon an indicator of ophthalmic artery pressure?
The relation between the intraocular pressure (IOP) at which the pulsating vascular tree (PVT) entoptic phenomenon is first observed and the ophthalmic artery diastolic pressure measured by ophthalmoscopic examination of the central retinal artery was determined in 25 normal volunteers. The PVT entoptic phenomenon consists in perceiving black stripes in the shape of branches of a tree appearing and disappearing synchronously with each heartbeat when the intraocular pressure is increased. The average IOP at which the entoptic phenomenon was first observed was 51.4 +/- 7.5 mm Hg, and the average ophthalmic artery diastolic pressure was 51.8 +/- 7.5. The correlation coefficient between both sets of numbers was r = 0.97 (p less than 0.01). These results show that the ophthalmic artery diastolic pressure can be measured accurately with the perception of the PVT phenomenon as an end point. Because the perception of the phenomenon is not disturbed by ocular media opacities, this method enables the determination of the ophthalmic artery diastolic pressure in eyes where an ophthalmoscopic examination is not possible.
Adult↗
Autoregulation of retinal circulation in response to decrease of perfusion pressure.
Autoregulation of the retinal circulation in response to an acute elevation of intraocular pressure was investigated in 17 subjects (23 eyes) with no ocular abnormalities, by means of the blue field entoptic phenomenon. This phenomenon allows a person to observe leukocytes flowing in his own macular capillaries. Subjects were instructed to compare the speed of their leukocytes in one eye with that in the other eye. All subjects perceived equal speed in both eyes. During their observation of the leukocytes, the intraocular pressure (IOP) was rapidly raised in one eye to a level at which autoregulation was not sufficient to maintain normal blood flow. At that level of IOP, subjects described the leukocytes moving slower in this eye than in the fellow eye. The IOP was then decreased in steps of 2 to 3 mm Hg until the subjects reported observing equal leukocyte speeds in both eyes. The IOP at which this occurred, IOPmax, represents the highest IOP (lowest mean perfusion pressure P min) at which the retina is able to maintain normal blood average IOPmax was 29.6 +/- 2.0 mm Hg, corresponding to an average of P min of 27 +/- 6 min Hg and demonstrating that a decrease of 36% or less in perfusion pressure is adequately compensated by retinal vascular autoregulation.
Adult↗
Mydriatic solution for outpatient indirect ophthalmoscopy.
A mydriatic used for outpatient indirect ophthalmoscopy should produce prompt, maximal, transient mydrasis after a single instillation. Cycloplegia or systemic side effects should be minimal. A solution of tropicamide with phenylephrine hydrochloride seems to achieve this most effectively. In a general retina clinic population, the percentage of pupils dilated, the degree of dilation, and the resistence of the dilation to intense illumination were used to evaluate various concentrations of the drugs. Eight-tenths percent tropicamide with 5% phenylephrine adequately dilated 98.8% of the eyes, among which 25% had dark irides and 9% were receiving miotic therapy. Reduction of the concentration of either component produced less adequate mydriasis; an increase of the tropicamide concentration resulted in a saturated solution with drug precipitate forming on storage and a less adequate dilation. With the optimal combination, 1 drop adequately dilates the general population; 2 drops appear on more effective than 1.
Administration, Topical↗
Blue field entoptic phenomenon in cataract patients.
The blue field entoptic phenomenon (BFE), which allows the observation of one's own leukocytes flowing in macular retinal capillaries, was used to predict postoperative macular function in 136 consecutive patients undergoing uncomplicated cataract operation. The results were compared to those obtained with three commonly used tests: two-light discrimination, color perception, and the Purkinje vascular entoptic phenomenon. All four tests identified a nearly equal number of the good maculae (visual acuity 20/40 of better) ranging from 87% for the two-light discrimination test to 94% for the BFE test. However, the tests varied greatly in predicting poor macular function (visual acuity 20/50 or worse). The BFE test identified more than 75% of the poor maculae; the Purkinje vascular entoptic test and the two-light discrimination test, only 22%; and the color perception test, 11%. A positive response to the BFE test indicated a .98 probability of good macular function; a negative response indicated a .82 probability of poor macular function, predictions that were better than the other three tests or their combination.
Cataract↗
Optical transmission of cataractous lens at 430 nm and blue field entoptoscopy.
Explore the source record for details and available documents.
Adolescent↗