Mechanisms of proteinuria in diabetic nephropathy. II. A study of the size-selective glomerular filtration barrier.

We evaluated the size-selective properties of the glomerular barrier in 30 patients in whom diabetic nephropathy was associated with urinary IgG losses. Neutral dextrans of graded size were used to characterize glomerular membrane-pore structure. A fractional IgG clearance (relative to freely permeable inulin) smaller or greater than 0.001 was used to distinguish patients with minor (group 1, N = 14) and major (group 2, N = 16) urinary IgG leakage, respectively. Fractional clearances of dextrans (theta D) of smaller size (radii 20-40 A) were similar, but those of larger dextrans (radii 42-60 A) were elevated in group 2 relative to group 1 patients. When plotted on log-normal probability coordinates, the correlation between theta D and radius in healthy subjects is linear, suggesting that glomerular pores form one population with a normal distribution. In diabetic nephropathy with urinary IgG leakage, however, theta D for large molecules was elevated and departed from linearity, suggesting a bimodal pore size distribution within the glomerular membrane. A pore model of solute transport revealed (1) the upper pore mode was highly permeable to large dextrans equivalent in size to IgG and (2) the fraction of glomerular filtrate permeating the large pores was greater in group 2 than in group 1 patients with diabetic nephropathy, 6% versus 3%, respectively. We conclude that urinary IgG leakage in diabetic nephropathy is determined by the development of a subpopulation of enlarged pores. The magnitude of urinary IgG losses appears to be a function of the membrane area-fraction occupied by the enlarged pores.

Intensive plasmapheresis in the treatment of diabetic retinopathy.

Two insulin-dependent diabetic patients with advanced nonproliferative and early proliferative retinopathy showed regression of diabetic retinopathy after three weeks of intensive plasmapheresis. Because of the sudden unexplained death in one patient, the study was stopped. However, these observations in this pilot study suggest that factors mediated through plasma contribute to the pathogenesis of diabetic microangiopathy.

The effect of pan-retinal photo-coagulation on rubeosis iridis.

Fifteen eyes of 11 patients with rubeosis iridis and angle neovascularization associated with retinal vascular disorders were treated with pan-retinal photocoagulation. In seven of the 15 eyes, the new vessels on the surface of the iris and in the angle regressed after pan-retinal photocoagulation therapy for disk neovascularization; five of the remaining eight eyes that were treated prospectively demonstrated similar involution of the rubeosis iridis. In three of the five preexisting peripheral anterior synechiae regressed and angle structures previously obscured became visible. Three to 36 months after therapy, three eyes developed a few new abnormal iris and angle vessels.

Techniques of argon laser photocoagulation of diabetic disk new vessels.

Four argon laser techniques have been evaluated in the eradication of diabetic disk neovascularization: focal (nonfeeder) photocoagulation, feeder-frond photocoagulation alone, panretinal photocoagulation alone, and feeder-frond treatment combined with panretinal photocoagulation. Focal photocoagulation was dangerous and the least effective technique in preventing recurrence of neovascularization. Feeder-frond photocoagulation was effective initially, but was associated with a high incidence of recurrent neovascularization. Panretinal photocoagulation and panretinal photocoagulation combined with feeder-frond treatment produced results superior to those obtained with the two earlier techniques. The best results were obtained with combined feeder-frond and panretinal photocoagulation done concurrently. Early diagnosis, aggressive photocoagulation therapy, and close follow-up were essential in order to obtain good results.

Subretinal fibrous membrane following argon laser photocoagulation of presumed histoplasmic maculopathy.

Following an initial improvement after argon laser slit-lamp photocoagulation of histoplasmic choroiditis, progressive visual loss occurred. Histopathological examination showed a dense fibrous membrane between Bruch's membrane and the sensory retina. There was no recurrence of hemorrhage or subretinal fluid. This case report provides an explanation for visual loss in the absence of recurrent inflammation or vascular leakage.

Complications of argon laser retinal photocoagulation: a five-year study.

The operator must become familiar with the dangers involved with argon laser photocoagulation. The hazards in the use of the argon laser slit-lamp photocoagulator derive from the same properties of the instrument that make it advantageous for the treatment of retinal vascular diseases: the wavelengths are highly absorbed by blood, and the beam can be focused to a small diameter. Of course complications can be avoided entirely by using applications so light the virtually no effect is obtained; but such an approach, although safe, cannot be therapeutic.

Argon laser photocoagulation in the treatment of presumed histoplasmic choroiditis.

Our experience with the evolving techniques we have reported has not resulted in significant increases in visual acuity over pretreatment levels. However, argon laser photocoagulation, properly given, does destroy subretinal neovascularization. The most significant points of technique are (1) heavy treatment of the entire frond; (2) accomplishment of this usually by a 200-mu spot size, 0.2 to 0.5 second, at 300 to 400 mW. power; (3) the eye under retrobulbar anesthesia, and (4) following the case at intervals of three to five days until the neovascular frond is destroyed. If the edge of the neovascular frond is within 200 mu of the fovea, treatment presents a very definite hazard to foveal vision and should be attempted only in the most experienced hands and on only the best-informed patients.