Steven B. Cohen

Magnetic Resonance Imaging in the Evaluation and Differentiation of Uveal Melanoma

We evaluated 39 patients with intraocular disease by magnetic resonance imaging (MRI). Malignant uveal melanoma was considered the likely diagnosis in 25 patients. Seventeen patients underwent surgery, and the histopathologic diagnosis of melanoma was confirmed. The authors observed that uveal melanomas had characteristic MRI features consisting of a relatively high-signal intensity in T1-weighted images and a relatively low-signal intensity in T2-weighted images. These images reflected their inherently relative short T1 and T2 relaxation times. Choroidal lesions elevated more than 3 mm were well visualized on MRIs. MRI also proved valuable for differentiating uveal melanoma from associated subretinal effusion, choroidal hemangioma, choroidal metastasis, and hemorrhagic and serous choroidal detachments.

Ab interno resection of uveal melanoma

Uveal melanomas located 1 to 2 disc diameters from the disc are difficult to manage. An internal resection approach (retinochoroidectomy ab interno) for the removal of melanomas has been developed and used to remove tumors in four patients. In five additional patients this procedure was combined with external resection to remove residual suspicious tissue from the resected margins.

Displaying electrocorticographic findings on gyral anatomy

Human electrocorticographic findings recorded from subdural arrays of electrodes were topographically mapped directly onto magnetic resonance images of gyral anatomy. With this technique gyri involved in generating somatosensory evoked potentials and epileptic phenomena are easily identified. Regions of the cortex which exhibit local spectral changes associated with cognitive tasks can also be visualized. These composite images of structure and function can provide insight regarding the functional organization of human cortex in relation to gyral anatomy and localized pathologic rhythms.

Effect of Intravitreal Silicone Oil on Intraocular Pressure

We analyzed data obtained prospectively on 48 consecutive patients treated with intravitreal silicone oil. Forty percent were diabetic. Follow-up ranged from three to eight months. An increase in intraocular pressure (IOP) (defined as a rise 10 mmHg above the preoperative level) developed in 56% of the eyes in the postoperative period (range, 10 to 53.4 mmHg; mean rise, 21.63 mmHg). There was no significant difference in mean pressure rise between diabetic and non-diabetic eyes. The increase in IOP was transient in 78% of the patients. In 70% the IOP rose to a level greater than 22 mmHg. All of these patients required medical treatment, and some silicone oil was removed in six. Only 22% of those requiring treatment still received medication at follow-up. No patient in this series had uncontrolled IOP.

A Randomized Clinical Trial of Feeder Vessel Photocoagulation of Sickle Cell Retinopathy: A Long-term Follow-up

Long-term follow-up of patients enrolled in a randomized prospective trial of feeder vessel photocoagulation for proliferative sickle retinopathy has been completed. Of the 44 patients enrolled in Chicago, nearly a decade follow-up has been achieved on 29 patients (45 eyes). There were 20 control untreated eyes and 25 argon laser-treated eyes. Prolonged loss of visual acuity was rare in both groups. Argon laser photocoagulation has had a sustained effect on reducing the incidence of vitreous hemorrhage and visual loss from vitreous hemorrhage. Nine (45%) of 20 control eyes had vitreous hemorrhage, and it was recurrent in six (66%) of these nine eyes. A single episode was the only hemorrhagic event in the treated eyes. The laser-induced complications of choroidal neovascularization or retinal detachment were not associated with long-term visual sequelae. New sea fan evolution in 47% of study eyes suggests that these patients require long-term surveillance.

Diagnosis and Management of Ocular Complications of Sickle Hemoglobinopathies: Part II

Sickle cell retinopathy in its advanced form is complicated by preretinal neovascularization, vitreous hemorrhage, and retinal detachment. Treatment of neovascularization can be performed with photocoagulation. Complications such as retinal breaks, retinal detachments, and choroidally fed neovascularization may result from such treatment. The risks vs. the benefits of various types of photocoagulation are currently being evaluated. Cryotherapy also may be used to treat neovascularization. It is currently being used in eyes with media that are too hazy to permit photocoagulation. It is used commonly during scleral buckling and vitrectomy procedures. In eyes with decreased visual acuity secondary to prolonged vitreous hemorrhage, pars plana vitrectomy can be utilized to produce optically clear media. Complications (including erythrocyte-induced glaucoma), however, may be severe. Retinal detachment can be treated by scleral buckling, but the markedly increased risk of anterior segment ischemia in patients with sickle cell hemoglobin necessitates preoperative, intraoperative, and postoperative prophylactic measures to minimize the risk of this potentially devastating complication. In eyes with retinal detachment with cloudy media and severe vitreous traction, combined scleral buckling and vitrectomy may be necessary. These eyes are extremely fragile, and a successful result is currently obtained in only about 50% of such cases. Hyphemas in patients with sickle cell hemoglobinopathies, whether traumatically or surgically induced, may have devastating effects on the eye. If elevated IOP results decreased vascular perfusion of the eye may cause irreversible damage to the retina and optic nerve. Most antiglaucoma medications, when used in the sickle cell patient, have a narrow margin of safety. Therefore, early surgical intervention for the treatment of sickle cell hyphemas is currently being evaluated.

Morphometry and flow dynamics of conjunctival microcirculation in sickle cell disease

Although the bulbar conjunctiva has been extensively studied in the sickle cell hemoglobinopathies, most of these studies have not been quantitative.’,’ To fill this void, we have applied stereologic techniques to analyze the microvascular density of the bulbar conjunctiva in normal control subjects and patients with genetic variants of sickle cell disease. Furthermore, we have applied intravital video microscopy to record and analyze the blood flow dynamics of the bulbar conjunctiva.