Clinical Histologic Correlation of Human Peripapillary Anatomy

The various types of peripapillary crescents which are observed clinically are generally interpreted to represent misalignments of the edges of the neural retina, retinal pigment epithelium (RIPE), choroid, and sclera at the disc margin. In order to test the validity of conventional assumptions about the anatomic basis for each type of crescent, the authors compared histologic sections to previously obtained clinical photographs and fluorescein angiograms of 21 eyes enucleated for choroidal melanomas. The authors' results define several configurations of peripapillary tissue, but also show that there can be more than one anatomic basis for some appearances. A scleral lip, which consists of an anterior extension of sclera to separate the choroid from the optic nerve head, is nearly always present, and ophthalmoscopically appears as a white rim that marks the disc margin and accumulates fluorescein after the vascular transit in an angiogram. A chorioscleral crescent occurs when the RPE is retracted from the disc margin, most prominent when associated with a tilted exit canal for the axon bundles through the sclera. In such a crescent, the choroid may be thinned or absent next to the disc, exposing to view some of the underlying sclera. Malposition of the embryonic fold occurs when the boundary between the neural retina and the RIPE does not coincide with the embryologically formed fold in the neuroectoderm that occurs at the disc. When this occurs, there is either a double layer RIPE (forming a very dark pigment crescent) or a double layer of incompletely formed neural retina adjacent to the disc. Irregular pigmentation occurs when the RPE adjacent to the disc lacks pigment or is hyperpigmented, mimicking misalignment of the layers when viewed by ophthalmoscopy

The Response of Retinal Vasculature to Angiotensin

A retinal arterial constriction was produced in anesthetized cats with a continuous transvitreal infusion of angiotensin I or antiotensin II (Ile-5). Constriction of vessels near the infusion cannula tip occurred over a range of angiotensin II concentrations from 10~9 to 10~4 molar, and was reversibly blocked by a ten-fold excess of the competitive antagonist saralasin. Constriction did not occur in response to angiotensin I if angiotensin-converting enzyme was blocked with Captopril. Control infusions of saline did not elicit a contraction of the retinal arteries. Severe axonal and inner retinal damage and necrosis occurred when angiotensin II produced a prolonged vasospasm, but not after infusion with control solutions, or whenconstriction caused by angiotensin was brief. Invest Ophthalmol Vis Sci 28: [676][677][678][679][680][681][682] 1987 While studying the effects of elevated intraocular pressure on the physiology of the optic nerve head, Sossi and Anderson 1 found that the blockage of axonal transport by elevated intraocular pressure was augmented when angiotensin was used to elevate the systemic arterial blood pressure. These findings suggested that angiotensin is capable of constricting the vessels of the optic nerve head, or at least capable of preventing autoregulatory dilation of the vessels when the adequacy of blood flow is challenged by elevation of intraocular pressure. There are interesting potential clinical correlations and implications if such a pathophysiologic mechanism participates in the optic nerve damage of glaucoma. 2 Constriction of vessels in the central nervous system (CNS), including the retina and optic nerve, 3 ' 4 might be expected as an autoregulatory response to elevated blood pressure. Such an indirect autoregulatory response (not due to angiotensin acting on receptors of the vessels) should not incapacitate the autoregulatory system, or produce constriction that is excessive to the point of interfering with neuronal physiology. Thus the interference with axonal transport suggests that angiotensin may be exerting direct vasoconstrictive action on the vessels of the optic nerve head, with the muscular tone preventing their redilation as an autoregulatory response to tissue ischemia. Such a direct effect on CNS vessels (including the retina and optic nerve) is unexpected, because the tight junctions of the endothelium should preclude access of circulating octapeptide angiotensin II (MW: 1067 Daltons) to the muscular coat of the vessels. Thus, the vessels should not have a direct response to angiotensin, unless either there are angiotensin receptors on the endothelium, which in turn transmit a message to the muscular coat, or else there is access to the muscular coat through a breach in the blood-brain barrier. We are attracted to the latter explanation for our experimental result, because the axonal transport abnormalities were localized at the optic nerve head, where there exists a breach in the blood-brain barrier by virtue of unimpeded diffusion of substances from the choroid. 5 Although our experiments indicated that these vessels may constrict in response to extravasated angiotensin, there is reason to doubt that the exterior wall of CNS vessels would have receptors for a circulating hormone to which they are not exposed under normal circumstances. Therefore, experiments were conducted to determine whether or not CNS vessels (specifically those of the retina and optic nerve head) exhibit a specific direct response to angiotensin when it bathes the exterior surface of the vessel. Materials and Methods All applicable federal and ARVO guidelines for care and use of animals for experimentation were followed. Cats of either sex (weight 1.5-5.0 Kg) were anesthetized with intraperitoneal nembutal (30 mg/kg) and atropine (0.035 mg/kg). Animals with signs of ocular trauma, inflammation, synechiae, or retinal scarring were not used. Some animals were given intravenous indo

Topical Fluorouracil: Pharmacokinetics in Normal Rabbit Eyes

• Postoperative subconjunctival fluorouracil injections may be a useful adjunct to standard glaucoma filtering surgery in eyes that are at high risk of failure. Topical administration would be perferable to subconjunctival administration; however, there are no data on the ocular penetration of topically applied fluorouracil. Consequently, we investigated the pharmacokinetics of topically administered fluorouracil labeled with carbon 14 in normal rabbit eyes. One drop (approximately 2.4 mg) of fluorouracil resulted in the following concentrations at 0.5 and six hours, respectively: 17.3 and 0.9 μg/g of conjunctiva; 24.3 and 1.3 μg/g of cornea; 14.6 and 0.2 μg/mL of aqueous; 0.8 and 0.5 μg/g of lens; 1.1 and 0.3 μg/g of vitreous; and 0.2 and less than 0.1 μg/mL of serum. Three drops (approximately 7.2 mg) of fluorouracil resulted in the following concentrations at 0.5 and eight hours, respectively: 589.8 and 1.3 μg/g of conjunctiva; 502.9 and 1.8 μg/g of cornea; 199.6 and 0.8 μg/mL of aqueous; 6.2 and 0.5 μg/g of lens; 6.8 and 0.5 pg/g of vitreous; and 1.3 and 0.2 μg/mL of serum. Since a fluorouracil concentration of 0.2 μg/mL inhibits rabbit conjunctival fibroblast proliferation in cell culture by 50%, these data suggest that topically applied fluorouracil achieves sufficient levels in the ocular compartments and tissues to have potential therapeutic applications

Corneal graft survival and intraocular pressure control after penetrating keratoplasty and glaucoma drainage device implantation

To investigate corneal graft survival rates and intraocular pressure (IOP) control in eyes after penetrating keratoplasty (PK) and glaucoma drainage device (GDD) implantation. Retrospective, comparative, consecutive case series. All patients who underwent PK and GDD implantation at the Bascom Palmer Eye Institute between January 1, 1993 and October 31, 1998. Graft clarity and IOP control. Of the 72 eyes in 72 patients identified, 47 (65%) underwent combined PK and GDD implantation, and 25 (35%) underwent GDD placement after PK (2–30 months after PK; median, 13 months). The GDD type was Baerveldt 350 mm 2 in 57 eyes, Ahmed in 9, Krupin in 2, and other in 4 eyes. The GDD was placed in the anterior chamber in 54 eyes (75%) and in the vitreous cavity in 18 eyes (25%). Preoperative IOP was 11 to 53 mmHg with or without antiglaucoma medications in 16 eyes (30%) with the GDD implanted in the anterior chamber and in 4 eyes (22%) with the GDD placed in the vitreous cavity ( P = 0.76). At 1 year after GDD implantation, the graft was clear in 26 eyes (48%) with the GDD in the anterior chamber compared with 15 eyes (83%) with the GDD in the vitreous cavity ( P = 0.013). Forty-eight eyes (89%) with the GDD in the anterior chamber and 18 eyes (100%) with the GDD in the vitreous cavity had IOP between 5 and 21 mmHg with or without antiglaucoma medications ( P = 0.33). The mean reduction in IOP, 1 year after surgery, was 12 mmHg among eyes with the GDD in the anterior chamber, compared with 17 mmHg among eyes with the GDD in the vitreous cavity ( P = 0.13) Corneal graft survival at 1 year is significantly higher among eyes with the GDD implanted in the vitreous cavity compared with those in which the GDD is implanted in the anterior chamber. The IOP was significantly lower at 1 year after surgery compared with before surgery in both groups, and there was no significant difference between the groups in IOP control and amount of IOP reduction. There was no significant difference in corneal graft survival or IOP control between eyes with the GDD implanted concurrently with the PK versus after the PK

Characteristics of optic nerve head drusen on optical coherence tomography images

To describe the characteristics of optic nerve head drusen in optical coherence tomography (OCT) images. Cross-sectional images of the optic nerve were obtained in seven patients with optic nerve head drusen with Stratus and spectral-domain OCT (Carl Zeiss Meditec, Dublin, CA). These were compared to optic disc photographs, autofluorescence, and echography images. For comparison, these tests were performed on four patients with papilledema and three patients with small optic discs. Optic nerve head drusen typically elevated the disc surface and appeared as an optically empty cavity, sometimes with a perceptible reflection from the posterior surface. The disc surface was also elevated in cases of papilledema, but had a strong anterior reflectance behind which there was no visible structure. The surface of the small optic nerves was slightly elevated, but with less anterior reflectance. Optic nerves with drusen showed features in these OCT images that were distinct from cases of papilledema or small optic discs

<title>Hydrophilic treatment of porous PTFE for intractable glaucoma implant devices</title>

Intractable glaucoma results from hindrances in the eyeball aqueous humor pathways that increase the intraocular pressure above normal physiological levels (over 20 mmHg). In this study porous PTFE membranes were made hydrophilic with a photochemical method that use ethyl alcohol and water for the chemical solution

Combined pars plana vitrectomy and glaucoma drainage implant placement for refractory glaucoma

PURPOSE: To report visual acuity and intraocular pressure outcomes among patients who have undergone combined pars plana vitrectomy and placement of a glaucoma drainage implant. METHODS: The medical records of all patients who underwent combined pars plana vitrectomy and placement of a glaucoma drainage implant at the Bascom Palmer Eye Institute by one of the authors between January 1, 1990, and February 28, 1998, were reviewed. Forty patients (40 eyes) were identified, including 14 patients with neovascular glaucoma secondary to proliferative diabetic retinopathy or central retinal vein occlusion, 15 patients with other posterior segment disease, seven patients with secondary angle-closure glaucoma, and four patients with aphakia with ruptured anterior hyaloid face. Main outcome measures included visual acuity and intraocular pressure at 1 year postoperatively. RESULTS: At 1 year postoperatively, 31 (77.5%) of 40 patients had stable or improved visual acuity; three eyes (7.5%) had a final visual acuity of no light perception and three additional eyes (7.5%) were enucleated (because of chronic pain in two eyes and endophthalmitis in one eye). Mean preoperative intraocular pressure was 34 mm Hg and the median number of preoperative antiglaucoma medications was two. At 1 year postoperatively, mean intraocular pressure was 13 mm Hg and the median number of antiglaucoma medications was zero. Twenty-two patients (55.0%) achieved an intraocular pressure greater than 5 mm Hg and less than or equal to 21 mm Hg without antiglaucoma medication, and an additional seven patients (17.5%) achieved this level of intraocular pressure control with medication. Only one patient (2.5%) underwent further glaucoma surgery for uncontrolled intraocular pressure. CONCLUSIONS: Although combined pars plana vitrectomy and placement of a glaucoma drainage implant is often a successful management option in selected patients with refractory glaucoma, visual outcome may be poor because of severe underlying ocular disease and postoperative complications

Asymmetries and visual field summaries as predictors of glaucoma in the ocular hypertension treatment study

PURPOSE. To evaluate whether baseline visual field data and asymmetries between eyes predict the onset of primary open-angle glaucoma (POAG) in Ocular Hypertension Treatment Study (OHTS) participants. METHODS. A new index, mean prognosis (MP), was designed for optimal combination of visual field thresholds, to discriminate between eyes that developed POAG from eyes that did not. Baseline intraocular pressure (IOP) in fellow eyes was used to construct measures of IOP asymmetry. Age-adjusted baseline thresholds were used to develop indicators of visual field asymmetry and summary measures of visual field defects. Marginal multivariate failure time models were constructed that relate the new index MP, IOP asymmetry, and visual field asymmetry to POAG onset for OHTS participants. RESULTS. The marginal multivariate failure time analysis showed that the MP index is significantly related to POAG onset (P &lt; 0.0001) and appears to be a more highly significant predictor of POAG onset than either mean deviation (MD; P = 0.17) or pattern standard deviation (PSD; P = 0.046). A 1-mm Hg increase in IOP asymmetry between fellow eyes is associated with a 17% increase in risk for development of POAG. When threshold asymmetry between eyes existed, the eye with lower thresholds was at a 37% greater risk of development of POAG, and this feature was more predictive of POAG onset than the visual field index MD, though not as strong a predictor as PSD. CONCLUSIONS. The MP index, IOP asymmetry, and binocular test point asymmetry can assist in clinical evaluation of eyes at risk of development of POAG.</p