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The newly developed laser Doppler technique was used to measure retinal blood flow characteristics in patients with forms of central retinal venous occlusive disease. The measurements were consistent with the expected reduced retinal blood flow in these disease processes.

A 14-year-old Iranian girl was referred for evaluation of bilateral elevation of the peripapillary retina. Fluorescein angiography was consistent with bilateral peripapillary exophytic retinal hemangioblastomas as seen in angiomatosis retinae (von Hippel's disease). Argon laser photocoagulation of the more severely affected left eye was performed with minimal effect upon the tumor.

Relative merits of different laser wavelengths for macular photocoagulation are analyzed in terms of light scattering and light absorption in hemoglobin, melanin, and macular xanthophyll. Disadvantages of inner retinal damage in the macula caused by the blue-green argon photocoagulators in standard clinical use are discussed, along with advantages of argon green and krypton yellow light. Results of treatment of subretinal neovascularization in disciform macular degeneration are presented. A repetitive treatment, close follow-up protocol was employed with the objectives of closing neovasculature and preserving central visual field. In 74 successive patients treated with monochromatic argon green radiation, neovasculature was closed in 93%, central visual field loss was reduced or stabilized in 76%, and visual acuity was improved or stabilized in 70%. Results were analyzed in terms of location and size of the neovascular membrane, and it was found that best results were obtained with neovascularization farther than 600 microns from the foveola and smaller than 2 mm2. In 17 patients with neovascular membranes more than 600 microns from the foveola, neovasculature was closed in 100%, central visual field loss was reduced or stabilized in 94%, and visual acuity was improved or stabilized in 88%. Similar results were obtained with monochromatic krypton yellow radiation.

The laser Doppler technique was used to measure the pulsatile characteristics of the retinal arterial blood flow in diabetic patients with severe retinopathy immediately before argon laser panretinal photocoagulation (PRP) and again one to two months after PRP. In each measurement the relative variation of the maximum red blood cell velocity, Vmax, in a major branch retinal artery was determined throughout the cardiac cycle. Flow pulsatility was defined as the ratio of Vmax at maximum systole to Vmax at minimum diastole. Following PRP, each eye showed a decrease in flow pulsatility as well as a decrease in retinal arterial and venous diameters. The measurements are consistent with an autoregulatory response of the retinal circulation to increased inner retinal oxygen concentration following PRP. Laser Doppler measurements may be a useful means of assessing the effectiveness of a particular PRP treatment.

(1) In owl monkeys, where no yellow staining of the media is present, there are clear-cut ophthalmoscopic and histologic differences in the lesions produced by equal amounts of argon green and blue light. (2) The yellow staining of the macula causes differences in lesion intensity and depth when different wavelengths are used for photocoagulation. (3) In humans the influence of age on this difference is apparent.

When using an argon laser photocoagulator it is often advantageous and sometimes indispensable to treat the patient in a supine position. Stabilization of the laser beam requires the use of a microscope equipped with a beam manipulator (joystick) that maintains the orientation of the laser beam wherever it is placed, without the operator having to hold the joystick. A low-vacuum contact lens or a three-mirror lens, and a microscope suspended from a floor stand are used. The patient is placed in the supine position on a stretcher of adjustable height with his head in a foam rubber conformer. Local anesthesia may not be necessary, but if indicated, the patient should not be treated in an upright position. A lid block is rarely required. General anesthesia is used with patients who cannot cooperate. There are 4 main indications for treatment in the supine position: (1) cases in which great accuracy is needed, such as treatment near the macula; (2) all cases in which retrobulbar anesthesia is necessary, with or without a lid block; (3) cases in which the patient is unable to cooperate; and (4) cases that require prolonged photocoagulation.

Communication between the retinal and the choroidal circulation occurred in one case of proliferative diabetic retinopathy and one case of Leber's disease (multiple miliary aneurysms) after argon laser photocoagulation treatment to eliminate abnormal retinal vasculature. In both instances rapid-sequence fluorescein angiography documented the choroidal origin of the anastomoses. Such anastomoses developed in areas where an excessively dense laser beam aimed at occluding retinal vessels presumably destroyed the underlying Bruch's membrane and permitted invasion of the retina by fibrovascular growth from the choriod. The occurrence of such growths is a potential complication of argon laser photocoagulation directly related to the power density used.