Edward W.D. Norton

Photocoagulation Treatment of Proliferative Diabetic Retinopathy: The Second Report of Diabetic Retinopathy Study Findings

Data from the Diabetic Retinopathy Study (DRS) show that photocoagulad inhibited the progression of retinopathy. These beneficial effects were noted to some degree in all those stages of diabetic retinopathy which were included in the Study. Some deleterious effects of treatment were also found, including losses of visual acuity and constriction of peripheral visual field. The risk of these harmful effects was considered acceptable in eyes with retinopathy in the moderate or severe retinopathy in the moderate or severe proliferative stage when the risk of severe visual loss without treatment was great. In early proliferative or severe nonproliferative retinopathy, when the risk of severe visual loss without treatment was less, the risks of harmful treatment effects assumed greater importance. In these earlier stages, DRS findings have not led to a clear choice between prompt treatment and deferral of treatment unless and until progression to a more severe stage occurs.

The Acute Retinal Necrosis Syndrome: Part 2: Histopathology and Etiology

The acute retinal necrosis syndrome is manifested by diffuse uveitis, vitritis, retinal vasculitis, and acute necrotizing retinitis (see Part 1). We studied the histopathology and electron microscopic findings of an eye enucleated from a 67-year-old man with typical acute retinal necrosis. Histology showed profound acute necrosis of the retina, retinal arteritis, and eosinophilic intranuclear inclusions in retinal cells. Electron microscopy demonstrated a herpes group virus in all layers of affected retina. The implications of these findings for antiviral and other treatments are discussed.

5-fluorouracil: new applications in complicated retinal detachment for an established antimetabolite.

Long-term reattachment of the retina following the development of proliferative vitreoretinopathy is often prevented by the occurrence of cellular reproliferation. 5-fluorouracil, a synthetic pyrimidine analog, is a potent inhibitor of fibroblast proliferation in cell culture and an animal model of tractional retinal detachment. Doses of up to 1.0 mg, when administered intravitreally to rabbits, result in no demonstrable retinal toxicity by microscopic and electrophysiologic criteria. The first 22 consecutive patients with advanced forms of proliferative vitreoretinopathy were treated with a combination of periocular and intraocular 5-fluorouracil, in addition to scleral buckling and vitrectomy. Retinal reattachment was achieved in 60% of patients at 6 months postoperatively. No serious systemic or ocular complications were observed although delayed healing of corneal epithelial defects occurred in 18% of cases and subtle subepithelial scarring in 31.8%. In combination with standard vitrectomy techniques, post-operative fluid gas exchange, and photocoagulation, periocular and subconjunctival 5-fluorouracil appears to improve the prognosis for longterm retinal reattachment following the development of proliferative vitreoretinopathy.

The Acute Retinal Necrosis Syndrome Part 1: Clinical Manifestations

The acute retinal necrosis syndrome is characterized by necrotizing retinitis, vitritis, and retinal vasculitis occurring in otherwise healthy patients. Experience with 11 cases and the review of 30 additional cases in the literature are presented. In this series, 50% of the affected eyes developed retinal detachments, and 64% had a final visual acuity of less than 20/200. The natural history, diagnosis, postulated etiology, and suggestions for management will be discussed.

Phaco-Ersatz: Cataract surgery designed to preserve accommodation

Phaco-Ersatz represents a new approach to cataract surgery and the correction of aphakia. The procedure involves the removal of the cataractous cortex and nucleus while preserving the lens capsule and its zonular attachments. The empty lens capsule is then refilled with biocompatible and optically suitable clear gel. A physiologic lens is recreated in situ. Experimental work with human cadaver eyes and rabbit and cat eyes in vivo demonstrates this surgical feasibility. A review of the literature reveals contradicting theories regarding the physical laws and lens properties governing accommodation. The accommodative potential of the ersatz lens has not been tested, but it may be speculated that this recreated lens may, in fact, possess some accommodative properties. Experimental investigations in this area represent the logical extension of intraocular lens implant development.

Retinal Detachment in Aphakia

As a retinal surgeon at a meeting where recent technical changes in cataract surgery are being enthusiastically discussed, I feel somewhat like a guest at a wedding who notices in a loud voice that the bride is somewhat pregnant.

Further Observations on the Diagnosis, Cause, and Treatment of Endophthalmitis

In our study of 54 suspected cases of endophthalmitis, vitreous aspiration was more sensitive in making a culture-proven diagnosis than anterior chamber paracentesis; Staphylococcus epidermidis was a more common cause of endophthalmitis than previously appreciated; and intraocular antibiotics in the recommended dosage are reasonably safe clinically and add a new dimension to the treatment of endophthalmitis.

Accommodation of an Endocapsular Silicone Lens (Phaco-Ersatz ) in the Nonhuman Primate

In owl monkeys, as a model of endocapsular cataract extraction, the lens material was removed through a small hole in the capsule and was replaced with a silicone polymeric gel. The ability of this endocapsular implant (Phaco-Ersatz) to accommodate was documented when pilocarpine produced an increase in the curvature of the lens surface and a decrease in the anterior chamber depth, just as occurs with the untouched natural lens. Refinements of the surgical technique are required to achieve a controlled degree of filling of the capsular bag and inhibit postoperative epithelial proliferation on the inner capsular surface.

Sulfur Hexafluoride in Owl Monkey Vitreous Cavity

Sulfur hexafluoride (SF6) gas, tested in the vitreous chamber of owl monkey eyes, remained in the vitreous cavity about twice as long as air (ten to 11 days vs. five to six days). Its volume expanded from the diffusion of other gases into the created gas pocket. Lens opacities developed when the lens was in continuous contact with SF6 or air. Sulfur hexafluoride appeared to be no more toxic to the retina than air, using electroretinographic, histologic, and electron microscopic criteria.

Ocular quinine toxicity.

A 25-year-old woman had no light perception in either eye 14.5 hours after ingesting 3.7 to 4.7 g of quinine. Fundus photographs showed mild venous distention and retinal haziness, but normal arteries. The electroretinogram, electrooculogram, and visual-evoked potential were all mildly abnormal. Two days after the patient ingested quinine, her visual acuity returned to 6/6 (20/20) with a markedly constricted visual field. The classic late fundus appearance of quinine toxicity, marked vascular narrowing, and disk pallor developed within six months. Visual fields remained constricted to 12 degrees with small temporal islands.