Thomas A. Weingeist

Central Retinal Artery Occlusion and Retinal Tolerance Time

Transient central retinal artery occlusion (CRAO) was produced in 63 eyes of rhesus monkeys by lateral orbitotomy and temporary clamping of the central retinal artery (CRA) for between 15 and 270 minutes. Thirty-three eyes were examined at regular intervals for 12 to 22 weeks. Color fundus photography, fluorescein fundus angiography, electroretinography (ERG) and visual evoked response (VER) were performed before and during clamping of the CRA as well as periodically after unclamping. All the eyes were examined by light and/or electron microscopy. This study revealed that the retina suffered irreparable damage after ischemia of 105 minutes, but recovered well after ischemia of 97 minutes. As a general rule, the monkey retina can tolerate up to 100 minutes of ischemia but not more.

Experimental occlusion of the central artery of the retina. IV: Retinal tolerance time to acute ischaemia.

Ophthalmoscopic, fluorescein angiographic, electrophysiological, and morphological studies on 63 eyes of rhesus monkeys with acute transient experimental occlusion of the central artery of the retina (OCAR) showed that the retina suffered irreparable damage after ischaemia of 105 minutes but recovered well after ischaemia of 97-98 minutes. The tolerance time of the brain to acute transient ischaemia is many times shorter than that of the retina. The metabolism of ischaemic neurones (in the retina and brain) is discussed with a view to explaining this difference, and also the various factors possibly responsible for the retinas longer tolerance to ischaemia, as compared to the brain.

Endophthalmitis after Pars Plana Vitrectomy

Purpose: To describe the clinical course and incidence of culture-proven Postvitrectomy endophthalmitis in 18 patients from five academic centers and three private practices. Methods: Patients undergoing pars plana vitrectomy for recent trauma or endophthalmitis were excluded. The average age was 58 years (range, 21–85 year). Sixty-one percent of the patients (11/18) had diabetes mellitus. The indication for initial vitrectomy was vitreous hemorrhage (n = 10), macular epiretinal membrane (n = 3), recurrent retinal detachment with proliferative vitreoretinopathy (n = 2), retinal detachment with retinoschisis (n =1), proliferative diabetic retinopathy with tractional retinal detachment (n =1), and dislocated intraocular lens (n =1). None of these eyes received prophylactic intraocular antibiotics during the vitrectomy. Results: All eyes were treated with intraocular antibiotics after the diagnosis of Postvitrectomy endophthalmitis was made. Final visual acuity ranged from 20/20 to no light perception and included five eyes with 20/50 or better visual acuity and 11 eyes with less than 5/200 visual acuity. Nine eyes had a final visual acuity of no light perception. Of the 16 eyes infected with a single organism, 71 % (5J7) of eyes infected with coagulasenegative staphylococci retained 20/50 or better final visual acuity compared with no eyes (0/9) infected with other organisms ( P = 0.005). Two eyes infected with both coagulase-negative Staphylococcus and Streptococcus had a final visual acuity of 20/ 400. Three eyes with a total hypopyon later had enucleation or evisceration. Based on the data from four medical centers, the incidence of endophthalmitis after pars plana vitrectomy performed over the last 10 years was 9/12,216 (0.07%). Conclusion: Endophthalmitis after vitrectomy is rare. Postvitrectomy bacterial endophthalmitis caused by organisms other than coagulase-negative staphylococci has a poor visual prognosis.

Combined Hamartomas of the Retina and Retinal Pigment Epithelium

Combined hamartomas of the retina and retinal pigment epithelium are rare fundus lesions. By combining cases seen by members of The Macula Society, clinical data was collected on 60 patients with combined hamartomas. We reviewed the clinical presentations, ophthalmoscopic, and fluorescein angiographic features and differential diagnosis of this tumor. Of 41 patients with adequate follow-up information, 10 (24%) lost at least two lines of visual acuity, usually due to tractional distortion of the fovea, and four (10%) had improved visual acuity following either amblyopia therapy or vitreous surgery for macular traction.

Experimental occlusion of the central artery of the retina. I. Ophthalmoscopic and fluorescein fundus angiographic studies.

Transient experimental occlusion of the central artery of the retina (OCAR), lasting from 15 to 270 minutes, was produced by clamping the artery in the orbit in 63 eyes of rhesus monkeys. Ophthalmoscopic and fluorescein angiographic studies were performed before and during clamping of the artery, as well as periodically after unclamping, for periods of up to 22 weeks. The effects of transient retinal ischaemia on the retina, optic disc, and retinal vascular bed were studied. 89% of the eyes showed a variable amount of residual retinal circulation on angiography during CAR clamping, but this did not exercise any protective action against ischaemic damage. Duration of the ischaemia was the principal factor determining severity of damage. OCAR for up to 98 minutes produced no significant permanent neural damage, but OCAR for 105 minutes or longer produced irreversible permanent neural damage. There was no significant permanent damage to the retinal vascular bed, though a transient fluorescein leakage was seen after OCAR for 2 1/2-3 hours or longer. The findings revealed that the normal red colour of the optic disc represents retinal vascular filling in the surface layer of the disc and not deeper vascular filling. The various factors influencing the retinal circulation and neural damage in OCAR are discussed.

Long-term visual outcome in patients with optic nerve pit and serous retinal detachment of the macula.

Serous detachment of the macula is a well-known complication in patients with an optic nerve pit. Despite the many descriptions of this condition and possible treatment options, the long-term natural history is not well known. The authors identified 15 eyes of 15 consecutive patients seen over 21 years who were diagnosed with a serous detachment of the macula arising from an optic nerve pit. Average length of follow-up was 9 years. Twelve eyes lost three or more lines of vision, two eyes remained unchanged, and only one eye improved. All of the 12 eyes losing three or more lines of vision experienced this decrease within the first 6 months of follow-up. Although only two patients had a visual acuity of 20/200 or less initially, 12 of 15 patients had a visual acuity of 20/200 or less at the time of their last examination. The appearance of the macula at last examination included cystic changes of the neurosensory retina, full-thickness hole formation, retinal pigment epithelial mottling, and lamellar hole formation in the outer retinal layer. The long-term visual prognosis in patients with optic nerve pit and untreated serous retinal detachment of the macula is poor, and visual loss occurs within 6 months of the serous detachment.

Long-term Visual Outcome in Terson Syndrome

The presentation and long-term visual outcome in 30 eyes with Terson syndrome is evaluated. In 25 of 30 eyes (83%), visual acuity of 20/50 or better was attained. This occurred in 12 of 16 eyes (75%) managed by observation alone and 12 of 14 eyes (86%) treated by pars plana vitrectomy. The most common long-term sequelae in all eyes studied was the formation of an epiretinal membrane. These occurred in 14 of 18 eyes (78%) followed for 3 or more years but accounted for significant visual loss in only 2 eyes. There was no difference in final visual outcome between those patients undergoing vitrectomy and those managed conservatively. However, visual recovery was more rapid in eyes undergoing vitrectomy despite the fact that vitrectomy was reserved for eyes with more dense vitreous hemorrhage.

Results and Complications of Pneumatic Retinopexy

Fifty-one patients with primary rhegmatogenous retinal detachment (RD) were treated by pneumatic retinopexy. The overall success rate for reattachment with one operation was 63%. Of the 34 phakic eyes, 25 (74%) were reattached; of the 17 aphakic or pseudophakic eyes, seven (41%) were reattached (P less than 0.05). Postoperative complications included the development of new tears (22%), inadequate closure of the original tear, shifting and delayed absorption of subretinal fluid, and opening of previously closed tears. Pneumatic retinopexy is a valuable new technique; however, careful patient selection and postoperative management is required.

Terson's Syndrome: Clinicopathologic Correlations

In seven cases of Tersons syndrome, an elevated, dome-shaped, membrane was detected in the posterior pole by ophthalmoscopy, echography, or during pars plana vitrectomy. Light and electron microscopic examination of two additional eyes obtained postmortem from an acute case of Tersons syndrome revealed that the posterior vitreous face was elevated by blood and that the internal limiting membrane of the retina was intact and in its normal position. In two chronic cases, a dome-shaped epiretinal membrane was excised from the macula during vitrectomy. Light and ultrastructural studies demonstrated that the membranes consisted of glial cells and basement membrane material. The dome-shaped structure observed in eyes with Tersons syndrome is due to the formation of a subhyaloid hemorrhage. The partially detached posterior hyaloid face created by this hemorrhage provides a scaffold for cellular proliferation and the development of an elevated epiretinal membrane in long-standing cases. Echographically, this membrane resembles a retinal detachment in B-scans, but can be clearly distinguished from retina with standardized A-scan.

Management of Siderosis Bulbi due to a Retained Ironcontaining Intraocular Foreign Body

The authors report their experience in managing 14 cases of siderosis bulbi secondary to a retained iron-containing intraocular foreign body (IOFB). The IOFB was removed in 12 of the 14 eyes. The IOFB was removed with a sclerotomy and external magnet (5 eyes), a pars plana vitrectomy (PPV) and intraocular forceps (5 eyes), a PPV and intraocular magnet (1 eye), and a PPV with aspiration using the suction mode of the vitrectomy instrument (1 eye). A siderotic cataract developed in 11 eyes and cataract extraction resulted in postoperative visual acuity ranging from 20/15 to 20/40. The most recent siderotic cataracts have been managed with cataract extraction and posterior chamber intraocular lens (PC IOL) implantation. No patient in this series experienced visual deterioration after receiving medical attention. The current management of siderosis bulbi is discussed.