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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.

The authors prospectively studied 106 consecutive phakic eyes with acute posterior vitreous detachment to determine the correlation between anterior vitreous pigment granules and retinal breaks. Pigment granules were identified in 15 eyes (14.1%), all of which had either a flap or an operculated retinal break. A retinal tear was found in only one eye without pigment granules ( P = 0.000). Other factors demonstrating a statistically significant association with retinal breaks included grossly visible preretinal or vitreous blood ( P = 0.039) and male gender ( P = 0.000). In the absence of other ocular pathology, the presence of vitreous pigment granules identifies a very high-risk group of acute posterior vitreous detachment patients.

An unusual case of severe head trauma is reported with postoperative 'total' ophthalmoplegia of the right eye. Subsequent recovery led to an apparent transposition of right medial and right lateral rectus function. Optokinetic stimulation induced convergence nystagmus when the target was moved to the patient's left, and a divergence nystagmus when the target was moved to the patient's right. In addition, attempted lateral gaze induced ipsilateral pupillary constriction. Aberrant regeneration involving the right abducens and right oculomotor nerves is proposed as the underlying mechanism.

• In a prospective evaluation of 154 consecutive retinal detachment procedures, the incidence of choroidal detachment was 39.6%. The age of the patient, drainage of subretinal fluid, and vortex compression by the explant seem to be the most important correlative factors. Scleral explantsup to one quadrant in circumferential length produced a minimal incidence (7.7%) of choroidal detachment. Posterior positioning of the explant also affected the incidence of choroidal detachment. After follow-up, ranging from six to 48 months, postoperative visual acuity was recorded for "macula-on" as well as "macula-off" retinal detachments. In the macula-on group, 78.6% of the patients with choroidal detachment retained a visual acuity of 20/50 or better compared with 82.8% of the patients without choroidal detachment. In the macula-off group, 43.2% of the patients with choroidal detachment achieved a visual acuity of 20/50 or better compared with 55.1% of the patients without choroidal detachment. The final anatomic success rate was 86.5% for eyes with choroidal detachment and 92.3% for eyes without choroidal detachment.

For Raman scattering studies of absorbing samples, e.g., in resonance Raman spectroscopy, it is frequently important to optimize the concentration and to correct for self-absorption effects on the observed intensities. These question are explored for 90° “transverse” scattering in a 0.1-cm capillary through intensity measurements of resonance Raman bands of ferro-cytochrome c and tris(1,10-phenanthroline) iron (II). It is found that a simple log intensity vs concentration plot provides the extrapolation needed to eliminate self-absorption effects. The optimum concentration is found to correspond to an absorbance per 1 cm of path length of 13 (average of values for the incident and scattered wavelengths) and is independent of absorptivity and of refractive index of the medium. The data are adequately reproduced by a point-scattering model, although different values of the effective light path through the sample are required to fit the self-absorption and intensity vs concentration curves.

A procoagulant effect was reported previously after injection of 0.50 to 0.75 ml of sodium hyaluronate (Healon) into the vitreous cavity at the end of phakic diabetic vitrectomies. A multicenter, randomized, prospective trial was done to study this effect. In the treatment group the media was clear in 50% of eyes in the immediate postoperative period compared with only 8% in the control group. At 2 to 6 weeks, there was no statistically significant difference between the two groups. The authors conclude that such sodium hyaluronate injection provides clear media in a significant number of eyes in the immediate postoperative period, potentially allowing thorough postoperative evaluation and early retinal photocoagulation if needed.

Ten moderately myopic women had blurred vision, light flashes, or paracentral scotomas associated with small yellow-white lesions of the inner choroid and pigment epithelium. Most lesions had an overlying serous detachment, were hyperfluorescent, and leaked fluorescein during the acute phase. The lesions healed into atrophic scars and became progressively more pigmented with time. Subretinal neovascular membranes later developed from scars in six patients. Vision was usually only minimally affected unless the lesions were subfoveal or unless choroidal neovascular membranes subsequently occurred. Extensive laboratory studies were noncontributory.

About 55% of the acyl groups of dog and human vitreous are unsaturated fatty acids. The major components are oleate (18:1, n-9) and arachidonate (20:4, n-6) with moderate amounts of linoleate (18:2, n-6) and docosahexaenoate (22:6, n-3). Palmitate (16:0) and stearate (18:0) are the major saturated fatty acids. There are no significant changes between ages 37-82 years in the fatty acyl group content and composition of human vitreous. In vitreous from Irish setters with hereditary rod-cone dysplasia (RCD) the levels of oleate are decreased with a concomitant increase in arachidonate. [1-14C]Arachidonic acid was actively incorporated into canine vitreous glycerolipids both in vitro and in vivo. The incorporation was mainly into phosphatidylinositol, triacylglycerol, phosphatidylcholine and phosphatidylethanolamine. There were some differences in the pattern of incorporation between human and dog and between in vivo and in vitro incubations of canine vitreous. Glycerolipid acylation was significantly increased in phosphatidylinositol and phosphatidylcholine in RCD canine vitreous. The pattern of incorporation of [U-14C]docosahexaenoic acid into vitreous glycerolipids was different from arachidonic acid incorporation. Although vitreous did not produce any measurable enzymatic synthesis of cyclooxygenase and lipoxygenase products from [1-14C]-arachidonic acid in vitro, there was significant generation of autooxidation products. These results suggest an active lipid metabolism in vitreous.

In seven cases of Terson's 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 Terson's 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 Terson's 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 13scans, but can be clearly distinguished from retina with standardized A-scan.

Sympathetic ophthalmia isa specific bilateral granulomatous inflammation of the uvea usually following surgical or accidental penetrating trauma to the globe. While generally considered rare, its true incidence is difficult to ascertain. One recent report noted an incidence of approximately two cases per 1,000 accidental perforations, and approximately one case per 10,000 intraocular surgical procedures. 1 Another recent clinical review of cases of sympathetic ophthalmia at one center over the past 20 years showed a decrease in the number of such cases following purely accidental or purely surgical injury, and an increase in the number of cases in which accidental injury was followed by surgical intervention in addition to primary repair. 2 Five cases of sympathetic ophthalmia following trauma and vitrectomy have been reported.3 It has been suggested by some that as more attempts at secondary reconstructive surgery (ie, vitrectomy) in severely traumatized eyes are made, a higher incidence of sympathetic uveitis may be expected. 2 However, it is also possible that a single primary or early secondary repair, including vitrectomy or len sectomy if indicated, may be less likely to incite sympathetic ophthalmia than mUltiple secondary procedures. The importance of early removal of lens material after trauma in the prevention of phacoanaphylaxis (phacogenic uveitis) has been stressed. 4 This report presents an additional case of sympathetic ophthalmia following scleral buckling, vitrectomy, and cataract extraction.

Resonance Raman spectra have been obtained from dilute solutions of ferri-hemoglobin fluoride, using several Ar+ laser lines, as well as the 6328 A He Ne line, for excitation. Several modes (including some with inverse polarization) correspond to vibrations which mix the first two π – π* porphyrin transitions, and their excitation profiles confirm the assignment of the lower of these transitions to a band, at 5280 A, which is unresolved in the room-temperature absorption spectrum. Resonance enhancement of porphyrin modes with 6328 A excitation suggests substantial mixing of the lower π – π* transition with porphyrin-metal charge transfer transitions, which presumably account for the low energy visible bands. Totally symmetric modes are observed which come into resonance with the intense near-ultraviolet (Soret) transition. The most intense of these, at 1373 cm−1 accurately obeys the frequency dependence expected for a mode which couples to a single electronic transition.

Retinal periphlebitis appeared as an early sign of bacterial endophthalmitis in three patients, a 36-year-old man with bilateral Terson's syndrome who underwent vitrectomy for dense vitreous hemorrhage, a 78-year-old woman who had had intracapsular cataract extraction and penetrating keratoplasty after repair of a wound leak and pars plana anterior membranectomy, and an 18-year-old man who suffered an accidental penetrating ocular injury. Staphylococcus organisms were recovered from vitreous samples in all three cases. Although recovery of useful vision is rare after postvitrectomy endophthalmitis, the first patient attained a final visual acuity of 20/50. The visual acuities of the second and third patients returned to 20/25 and 20/20 respectively. In an experimental primate (cynomolgus monkey) model of bacterial endophthalmitis, retinal periphlebitis developed early and closely resembled the clinical findings in humans. Histopathologic studies confirmed the presence of inflammatory cells that infiltrated the retinal venules.

The proliferative activity of a number of intraocular fluids, bovine retinal extract, and normal serum (from humans and cynomolgus monkeys) was investigated by in vitro tissue culture studies, with the use of tritiated thymidine incorporation by the cultured endothelial cells of human umbilical veins. There was increased tritiated thymidine incorporation by (1) the aqueous, vitreous, and intraocular fluid (IOF) (which filled the eye after lensectomy and vitrectomy) removed from cynomolgus monkey eyes with iris neovascularization or with neovascular glaucoma (NVG) that developed after experimental retinal vein occlusion, (2) by aqueous and vitreous removed from human eyes with NVG or proliferative diabetic retinopathy; (3) by the serum, and (4) by the bovine retinal extract. However, tritiated thymidine incorporation was not increased by the normal aqueous, vitreous, or IOF.

Diabetic retinopathy is a leading cause of blindness. The two forms of retinopathy are background (nonproliferative) and proliferative. Risk for retinopathy increases with the duration of diabetes. Therefore, diabetics need to have regular eye examinations, including specific techniques, to detect subtle retinal changes. Timely ophthalmologic referral is crucial to maximize potential visual results. Patients with macular edema may be candidates for focal laser therapy. Those with proliferative retinopathy may be treated with panretinal laser photocoagulation, which causes regression of neovascularization, or vitrectomy to remove vitreous hemorrhage and repair complicated retinal detachments.

• A small group of eyes with proliferative diabetic retinopathy develop progressive macular traction characterized by partial vitreous detachment with vitreoretinal traction along the arcades and disc, retinal traction lines extending through the fovea, and progressive visual loss. Vitrectomy may be helpful in stabilizing selected eyes and actually improving visual acuity.

Elevated intraocular pressure (IOP) early after cataract extraction with alpha-chymotrypsin is a well-described, common occurrence. To study the incidence of pressure increase and the efficacy of medical therapy, IOP was monitored every 12 hours beginning on the first postoperative day in 68 patients after otherwise uncomplicated intracapsular cataract extraction performed with one milliliter of alpha-chymotrypsin and wound closure with multiple sutures. Patients were randomly assigned to one of three groups: treatment with oral acetazolamide, treatment with topical timolol, or no treatment. Without prophylactic treatment, the prevalence of pressure elevation at 24 hours postoperatively was 69% with IOP greater than or equal to 25 mm Hg; 29% with IOP greater than or equal to 40 mm Hg. This was independent of the type of sutures used (10--0 nylon or 9--0 silk). The patients of four different surgeons had similar rates of occurrence of postoperative glaucoma. Both timolol and acetazolamide were essentially equally effective in lowering IOP in these patients. No adverse side effects were observed. With these effective treatments available if needed, we believe that routine monitoring of the IOP by applanation tonometry during the early postoperative course provides a good opportunity for reducing the risk of complications from excessive intraocular pressure.

We measured a 15 +/- 2-mm displacement of the illuminating element of the coaxial operating microscope from the true optical center of the microscope. We further calculated the displacement of the image of the illuminating element of the operating microscope on the retina of the simplified schematic eye and found that the "coaxial" operating microscope would focus the light between 1.3 and 1.8 mm superior to the fovea of the eye, depending on the theoretical refractive status of the simplified eye. Actual measurements on a simulated retina (35-mm camera) confirmed the calculated displacements. The deviation varied with eye tilt and microscope position. We also found that the maneuvers commonly used by anterior segment surgeons of tilting the microscope and rotating the eye downward tended to displace the image of the illuminating element closer to the fovea, increasing the chance for symptomatic retinal damage. A combination of such maneuvers may reduce the potential for clinically significant retinal phototoxicity by displacing the light further inferior to the fovea.

To the Editor. —Stereo-pair photographs and diagrams can be viewed as three-dimensional images by chiastopic (ie, cross-eyed) observation without using any stereoscopic viewing devices. We found that the majority of a test group of adults could learn this skill in less than 30 minutes in supervised practice sessions. The acquisition of this skill should have practical application in viewing stereo-pairs of fundus photographs. It is well known that stereopsis can be attained by viewing a pair of pictures of a solid object at two slightly different angles. In the common application of this phenomenon, one of the two pictures is presented exclusively to the right eye and the other exclusively to the left eye by one of several available techniques (eg, red/green glasses, polarizing filters, prisms). It is not widely known, however, that it is possible to achieve stereopsis by looking directly at stereo-pairs without resorting to the use

Standardized Echography studies were performed on 11 eyes of 6 patients with Terson’s syndrome prior to pars-plana vitrectomy. In each case either a total or subtotal posterior vitreous detachment was observed in association with a dense vitreous hemorrhage. In addition, a very thin and smooth, minimally mobile, preretinal membrane extended over the posterior pole. All vitreous structures were extremely mobile. The preretinal membrane, though suggestive of retinal detachment in B-scans, was clearly less reflective and thinner than detached retina when evaluated with Standardized A-scan. This membrane appeared to be dome-shaped in some cases, but was less elevated in others.

We determined the site of the focal illumination from the Zeiss OPMI-6 operating microscope on the retina of the phakic and aphakic human cadaver eye by directly observing the illuminating element image on the posterior scleral surface of the globe. With the eye straight ahead and the operating microscope level, the focal oval area of retinal illumination was located superior to the foveola in both the phakic and aphakic eye. Tilting the operating microscope 10 degrees toward the surgeon displaced the entire illuminating element image 0.50 mm below the foveola in the phakic eye and 0.25 mm below the foveola in the aphakic eye. Rotating the eye inferiorly 10 degrees displaced the entire illuminating element image 1.0 mm below the foveola in the phakic eye and 1.25 mm below the foveola in the aphakic eye. Centering the field of view superiorly (viewing the superior limbus) paradoxically displaced the illuminating element image inferiorly, resulting in central foveal illumination. Foveal light exposure was avoided in most eye positions by tilting the microscope at least 10 degrees toward the surgeon.

The use of the neodymium (ND) YAG laser in ophthalmology is a new and exciting development, providing a noninvasive surgical tool for the lysis of intraocular membranes. The editor is one of the true pioneers in the field, having used the mode-locked ND YAG laser to treat thousands of eyes. The fundamental physical properties of the YAG laser are concisely explained in the early chapters, most of them comprehensible even to those who have not studied physics for 20 or more years. The clinical chapters are somewhat sketchy and lack precise references to the literature. Despite this shortcoming, the book does serve as the most comprehensive volume yet published on the use of YAG lasers in ophthalmology. The "before and after" clinical photographs (more than 50 color photographs) are particularly helpful in demonstrating the scope of usefulness of the YAG laser, aiding the novice YAG surgeon in case selection. Although

• Photoradiation therapy is a new technique currently under clinical investigation for the treatment of a variety of solid malignant tumors. The technique involves intravenous (IV) administration of hematoporphyrin derivative, a photosensitizing compound that is preferentially retained by malignant cells, and photoactivation of a neoplasm with red light (630 nm) to obtain selective destruction of cancer cells. A modification of this technique was used to treat iris neovascularization produced in a primate model of retinal vein occlusion. Following IV injection of hematoporphyrin derivative, the anterior surface of the iris was exposed to red light for 30 to 45 minutes. In the four eyes treated, there was a marked reduction of fluorescein leakage from the neovascular tissue within 24 hours following treatment. Histologic examination of two eyes demonstrated a selective response of the iris neovascularization to this therapy, with apparent preservation of surrounding tissue.

In Reply. —According to the Dictionary of Visual Science , 1 chiastopic fusion is "fusion obtained by voluntarily converging to fixate directly two fusible targets, laterally separated in space, such that the right eye directly fixates the left target and the left eye the right target." However, we respectfully defer to the expertise of the classics scholar from Houston, because, in matters etymological, all we can say is "It's Greek to us."