Myron Yanoff

Pathology of human cystoid macular edema

The light and electron microscopic findings are reviewed in two patients who had eyes enucleated for peripheral choroidal malignant melanomas. Preoperatively, cystoid macular edema was documented by fluorescein angiography in the melanoma-containing eye in both patients. Intracytoplasmic swelling (edema) of the Müller (glial) cells is the anatomical basis for the macular edema. Intercellular (extracellular) collections of fluid probably are late, endstage results of the process that result form prolonged, excessive, intracellular edema, cell death and disruption. The process probably rests on an ischemic basis, as evidenced by severe changes in the microvasculature. In the one patient in whom the optic nerve was available for study, marked intracellular swelling (edema) of glial cells in the lamina choroidalis of the optic nerve head was present, associated with compression of the adjacent axons. The nearby temporal, parapapillary retina also showed edema of Müller cells, and compression of the nerve fibers (ganglion cell axons), suggesting a more widespread process than was clinically evident. Again, severe changes were present in the microvasculature, both in the optic nerve and parapapillary retina. The underlying cause of the microvasculature changes that lead to ischemia, perhaps an intrinsic pharmacologic agent, is yet to be found.

Intravitreal Injection of Erythropoietin Protects both Retinal Vascular and Neuronal Cells in Early Diabetes

PURPOSE To explore and evaluate the protective effect of erythropoietin (EPO) on retinal cells of chemically induced diabetic rats after EPO was injected intravitreally at the onset of diabetes. METHODS Diabetes was induced in Sprague-Dawley rats by intraperitoneal injection of streptozotocin (STZ). At the onset of diabetes, a single intravitreal injection of EPO (0.05-200 ng/eye) was performed. In the following 6 weeks, the blood retinal barrier (BRB) was evaluated by Evans blue permeation (EBP). Retinal cell death in different layers was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The retinal thickness and cell counts were examined at the light microscopic level. Electron microscopy (EM) was used to scrutinize retinal vascular and neuronal injury. Neurosensory retinas of normal and diabetic rats were used as the sources of reverse transcription-polymerase chain reaction (RT-PCR) and Western blot for the detection of EPO, EPO receptor (EpoR), and products of the extracellular signal-regulated kinase (ERK) and the signal transducers and activators of transcription 5 (STAT5) pathways. The distribution of EpoR in retinal layers was demonstrated by immunohistochemistry (IHC). RESULTS In the diabetic rats, BRB breakdown was detected soon after the onset of diabetes, peaked at 2 weeks, and reached a plateau at 2 to 4 weeks. The number of TUNEL-positive cells increased in the neurosensory retina, especially, the outer nuclear layer (ONL) at 1 week after diabetes onset and reached a peak at 4 to 6 weeks. The retinal thickness and the number of cells in the ONL were reduced significantly. EM observations demonstrated vascular and photoreceptor cell death starting soon after the onset of diabetes. All these changes were largely prevented by EPO treatment. Upregulation of EpoR in the neurosensory retina was detected at both the transcriptional and protein levels 4 to 8 weeks after the onset of diabetes, whereas, the endogenous EPO levels of neurosensory retinas were essentially unchanged during the same period observed. In EPO-treated diabetic groups, EpoR expression remained at upregulated levels. Within 2 weeks of the onset of diabetes, activation of the ERK but not the STAT5 pathway was detected in the diabetic retina treated with EPO. CONCLUSIONS These data demonstrate that apoptosis is an major contributor to neuronal cell death in the early course of diabetic retinopathy (DR). The upregulation of EpoR may be a compensatory response of retinal cells and tissue to diabetic stresses. The EPO/EpoR system as a maintenance-survival mechanism of retinal neurons responds to the insults of early diabetes other than ischemia. The protective function of EPO/EpoR at the least acts through the EpoR-mediated ERK pathway. Exogenous EPO administration by intravitreal injection in early diabetes may prevent retinal cell death and protect the BRB function. Therefore, this is a novel approach for treatment of early DR.

Histogenesis of malignant melanomas of the uvea. II. Relationship of uveal nevi to malignant melanomas

Many theories concerning the histogenesis of uveal melanomas have been advanced. While much clinical as well as histopathologic evidence is available to support the belief that most malignant melanomas of the iris have their origin in pre‐existing nevi, the histogenesis of melanomas of the choroid and ciliary body is much more controversial. A histopathologic study of 100 consecutive malignant melanomas of the choroid and ciliary body was undertaken in an effort to ascertain the frequency with which benign‐appearing cells (nevus cells) might be found within or along the edges of the tumors. Such cells, cytologically identical with the cells constituting nevi of the uveal tract, were found in considerable numbers in 73 of the 100 melanomas. The authors conclude that most malignant melanomas, perhaps all such neoplasms, have their origin in pre‐existing nevi.

Intraocular Pressure Status in 100 Consecutive Patients with Exfoliation Syndrome

An evaluation of 100 consecutive patients in whom the exfoliation syndrome was detected as an incidental finding revealed the incidence of glaucoma to be lower than previously reported. There were 75 women and 25 men in the study. Seventy-six patients had unilateral and 24 patients had bilateral involvement. The mean age of the unilateral group was 70 years and that of the bilateral group, 71 years. Of 124 eyes having the exfoliation syndrome, 78% had normal intraocular pressure, 15% had ocular hypertension (intraocular pressure greater than 22 mm Hg but no cupping or field loss), and 7% had glaucoma. Women out-numbered men in normotensive and ocular hypertensive groups, but no sex difference was apparent in the group with glaucoma. In the 76 patients in the unilateral group, 13 eyes having the exfoliation syndrome had ocular hypertension, and three had glaucoma. In five of the 16 patients with ocular pressure abnormalities in the eye with exfoliation syndrome, the fellow eye had ocular hypertension.

Cultured retinal capillary pericytes die by apoptosis after an abrupt fluctuation from high to low glucose levels : a comparative study with retinal capillary endothelial cells

SummaryA number of clinical observations concerning cases of glycemic fluctuation have prompted us to study whether or not a rapid change in blood glucose concentration can aggravate retinal microvascular pathology during the early stage of diabetic retinopathy. We conducted a comparative study of retinal capillary pericytes and endothelial cells in vitro. Both types of cells, either in single culture or in co-culture, were initially incubated in medium with high glucose (20–40 mmol/l), followed by a rapid reduction of glucose to 3.5, 1, or 0.5 mmol/l. This type of reduction of extracellular glucose resulted in depletion of intracellular glucose, occurring much faster in pericytes than in endothelial cells. The abrupt reduction in glucose caused pericyte cell shrinkage and nuclear condensation associated with DNA fragmentation, followed by loss of cell viability. All of these pericyte changes are apoptosis-like characteristics. This apoptotic process was prevented by the addition of cycloheximide, a protein synthesis inhibitor, or by platelet-derived growth factor BB, which is a known competent factor for pericyte growth. In analysis of signalling pathways during the abrupt fluctuation of glucose, the occurrence of pericyte apoptosis was an intracellular calcium-dependent, protein kinase C and protein kinase A mediated, and poly (ADP-ribose) synthetase-dependent process. Interestingly, a larger degree of DNA fragmentation was observed with a higher magnitude and a longer duration of pre-existing hyperglycaemia. These results suggest that the magnitude and duration of pre-existing hyperglycaemia prime the apoptotic responsiveness of pericytes. Retinal capillary endothelial cells, after an identical glucose fluctuation treatment did not undergo an apoptotic process.

ERK- and Akt-dependent neuroprotection by erythropoietin (EPO) against glyoxal-AGEs via modulation of Bcl-xL, Bax, and BAD.

PURPOSE To characterize the neuroprotective mechanisms of erythropoietin (EPO) against the stress of glyoxal-advanced glycation end products (AGEs) in retinal neuronal cells. METHODS Rat retinal organ culture, primary retinal neuron culture, and retinal cell line (R28 cell) culture under glyoxal-AGEs insult were used as in vitro models. Exogenous EPO was applied to these models. Retinal neuronal cell death was assessed by TUNEL, ethidium bromide/acridine orange staining, and cell viability assay. R28 cell proliferation was evaluated by BrdU incorporation and propidium iodide staining. Real-time RT-PCR and Western blot analysis were used to detect Bcl-xL, Bcl-2, Bax, BAD, and products of extracellular signal regulated kinase (ERK) and Akt pathways. Specific inhibitors and plasmids were used to pinpoint the roles of ERK and Akt pathways. Results. EPO protected the retinal cells from glyoxal-AGE-induced injury in a time- and dose-dependent fashion. The protective function of EPO was proved to be antiapoptotic, not pro-cell proliferative. Glyoxal upregulated Bax expression but suppressed Bcl-xL expression and BAD phosphorylation. In contrast, EPO enhanced BAD phosphorylation and Bcl-xL expression but downregulated Bax. The regulation of these apoptosis-related proteins by EPO was through ERK and Akt pathways. CONCLUSIONS These data demonstrate that exogenous EPO significantly attenuates the retinal neuronal cell death induced by glyoxal-AGEs by promoting antiapoptotic and suppressing apoptotic proteins. EPO/EPO receptor signaling through ERK and Akt pathways is pivotal in EPO neuroprotective mechanisms.

Conjunctival Biopsy as an Aid in the Evaluation of the Patient with Suspected Sarcoidosis

Conjunctival biopsy is an underused but simple technique in the evaluation of the patient with sarcoidosis and occasionally other systemic diseases. In 55% of patients with biopsy-proven sarcoidosis from other sites, a blind conjunctival biopsy was positive. Bilateral conjunctival biopsies and the examination of multiple sections of each biopsy were essential to obtain this high of a yield. There was no relationship between an anterior uveitis and a positive conjunctival biopsy.

A clinicopathologic study of four cases of primary open-angle glaucoma compared to normal eyes.

Eight eyes obtained at autopsy from four patient who had chronic open-angle glaucoma were compared to eyes with normal aging changes. Three cases were characterized by early and pronounced abnormalities in the uveal portion of the drainage angle. The findings consisted of formation of an exaggerated scleral spur upon the scleral roll by accretion and compaction of the overlying uveal meshwork, hyalinization and atrophy of the adjacent ciliary muscle, and atrophy of the iris root. The fourth case showed widespread proliferation of endothelium into the lumen of Schlemms canal. We concluded that the predominant histologic findings in eyes with open-angle glaucoma consists of an exaggeration of normal aging processes, ranging in a spectrum from excessive involvement of the uveal pathway to excessive involvement of the canal of Schlemm pathway.

Subconjunctival Anesthesia: An Alternative to Retrobulbar and Peribulbar Techniques

We present a method of anesthesia for intraocular surgery of the anterior segment of the eye that avoids the risks of the potential complications associated with retrobulbar and peribulbar anesthesia. The method consists of topical anesthesia plus 0.5 cc of lidocaine (with hyaluronidase and epinephrine) injected beneath the superior conjunctiva. We have demonstrated the safety and effectiveness of this technique in 431 consecutive cases.

Invasive Keratoacanthoma of the Eyelid and Ocular Adnexa

PURPOSE To report three patients with superficially invasive crateriform squamous proliferations of periocular tissue. METHODS The authors identified three patients with superficially invasive periocular tumors that had clinical features of keratoacanthoma. Clinical histories, radiographs, and surgical pathologic specimens were reviewed. RESULTS All three tumors arose over several weeks, had a crateriform configuration, and exhibited superficial invasion of underlying tissues, including perineural invasion and infiltration into skeletal muscle. All three tumors were classified as invasive keratoacanthoma. One tumor exhibited late perineural extension into the cavernous sinus and convincing histologic features consistent with squamous cell carcinoma. CONCLUSION The clinical importance of recognizing invasive keratoacanthoma is that although the tumor has the potential for spontaneous involution, locally aggressive behavior with deep perineural invasion is possible. This tumor is considered to represent a variant of squamous cell carcinoma. The authors recommend complete surgical excision of crateriform squamous proliferations with frozen section control of margins of resection.