Hermann D. Schubert

Postsurgical hypotony: relationship to fistulization, inflammation, chorioretinal lesions, and the vitreous☆

Hypotony is a natural occurrence, symptom, and complication of surgical treatment. With more sophisticated and aggressive techniques, postsurgical hypotony recently has been given increased attention as an obstacle to success of surgery for glaucoma and retinal detachment. Whereas two standard deviations below normal pressure (15.9-5.8 = 10.1 mm Hg) can be called hypotonous, most eyes, depending on scleral rigidity, lid pressure, eye rubbing, or corneal or retinal edema, will be symptomatic at < 5 mm Hg. Hypotony can be defined as the low pressure (whether acute, transient, chronic or permanent) which, in an individual eye, leads to functional changes (whether asymptomatic or symptomatic) and structural changes (whether reversible or irreversible). Depending on its duration and degree, postsurgical hypotony produces characteristic tissue changes that often are modified by, but separate from, the tissue changes caused by an underlying disease or its surgical treatment. This review summarizes the situations, variably associated with hypotony, that occur after such interventions as cataract extraction, filtering surgery, cyclodialysis, cyclodestruction, and vitreoretinal surgery, in addition to the reported pathomechanisms of hypotony and its proposed treatments.

Exogenous Na-hyaluronate in the anterior chamber of the owl monkey and its effect on the intraocular pressure.

Exogenous, ultrapure (sterile, pyrogen-free), non-inflammatory fraction of Na-hyaluronate (NIF-NaHA) was introduced into the anterior chamber of owl monkeys (Aotus trivirgatus), replacing approximately 48% or 77% of the aqueous humor and creating post-injection intraocular pressures (IOPs) below normal (5-10 mmHg) or above normal (40-60 mmHg), respectively. Five different molecular weight samples (MW 1.7, 3.4, 3.7, 4.5 and 4.9 X 10(6)) were used. All solutions contained 1% NIF-NaHA and, because of the varying molecular weights, the viscosities of the solutions ranged between 10 000 and 930 000 cSt. The IOP and the rate of export of the exogenous NIF-NaHA from the anterior chamber were measured. All solutions caused an increase in the IOP, and the maximum level occurred at 4 hr after injection. In all cases, the IOP returned to normal 24 hr after injection. The highest and most persistent increase in IOP was observed after the injection of the solution with the lowest viscosity (10 000 cSt). The smallest increases in IOP over the post-operative value were observed after replacement of the aqueous humor using those samples with viscosities of 10 0000 to 300 000 cSt. The turnover (export rate) of injected NIF-NaHA depends for the most part on the viscosity of the injected solution. With increasing viscosity the rate constant, and therefore the half-life, of the injected NIF-NaHA decreases. The volume fraction of the viscous solution replacing the aqueous humor is also a determining factor in establishing the turnover rate. The molecular weight of the injected NIF-NaHA did not change during that time (48 hr) in which a sufficient amount of sample for analysis could be obtained. No evidence was found for the presence of any kind of hyaluronic acid-degrading agent in the anterior chamber.

Varicella-zoster Virus Retrobulbar Optic Neuritis in a Patient With Human Immunodeficiency Virus

PURPOSE To determine the cause of bilateral retrobulbar optic neuritis followed by progressive outer retinal necrosis in a patient with human immunodeficiency virus (HIV). METHODS Extensive ophthalmologic, neurologic, infectious disease, rheumatologic, and radiologic examinations were performed. RESULTS Cerebrospinal fluid samples taken after the onset of bilateral retrobulbar optic neuritis and before the development of clinical progressive outer retinal necrosis disclosed varicella-zoster virus from polymerase chain reaction and viral culture. CONCLUSION Ophthalmologists and neurologists should consider varicella-zoster virus optic neuritis as a potential precursor of progressive outer retinal necrosis and as a cause of retrobulbar optic neuritis in patients infected with HIV.

STRUCTURAL ORGANIZATION OF CHOROIDAL COLOBOMAS OF YOUNG AND ADULT PATIENTS AND MECHANISM OF RETINAL DETACHMENT

PURPOSE In colobomatous eyes, the risk of retinal detachment increases with age. This study elucidates the anatomic conditions and pathologic process of retinal detachment associated with colobomas. METHODS The records, including histologic slides, of 14 children (1 day to 17 months old) and 7 adults (17 to 78 years old) with colobomas were examined. RESULTS In children, colobomas were associated with lethal malformations. The extracolobomatous inner retinal layers extended centrally, forming the intercalary membrane. Duplication of the outer retinal layers and a horizontal shift of Müllerian glia created a triangle and a locus minoris resistentiae adjacent to the laterally displaced pigment epithelium. Part of the locus was an incomplete layer of photoreceptors excluding Müllerian glia. In adults, atrophy of the intercalary membrane, manifested as central schisis, thinning of the neuroepithelium, and hole formation, was related to a paucity of blood vessels within and underneath the intercalary membrane and the size of colobomas. The margins featured blood vessels, pigment epithelial hypertrophy, and choroidal and scleral thickening in a compact, intertwined arrangement. CONCLUSIONS Glial atrophy, schisis, and hole formation in the intercalary membrane and separation of the locus minoris resistentiae from the pigment epithelium can disrupt barriers to fluid flow and set the stage for rhegmatogenous retinal detachment. That process is exacerbated by scleral ectasia, increasing vitreous traction at the margin, and retinovascular ischemia within the intercalary membrane. A vascularized, compact margin resembling a laser barrier, found predominantly in adults, may protect against retinal detachment.

Schisis-like rhegmatogenous retinal detachment associated with choroidal colobomas

Abstract• Background: The breaks that cause retinal detachments in colobomatous eyes are often hidden within the lesion and difficult to find. • Method: To elucidate the pathoanatomy and possible pathomechanism of such detachments, histological sections of eight choroidal colobomas were reviewed. • Results: Sections of the margin showed central continuation of the inner neuroblastic layer (the intercalary membrane) and eversion and separation of the outer neuroblastic layer. The opposite direction of continuity of the neuroblastic layers created a schisis-like configuration between the intercalary membrane and the everted outer retina. The zone of duplication was a point of retinal adhesion, but also a locus minoris resistentiae due to vitreous attachments and variable glial support at the margin. • Conclusion: The subset of coloboma-associated retinal detachments requires both a central break in the inner layer and a break in the outer layer at the margin of the coloboma. The inner layer break may be precipated by retinovascular ischemia or scleral stretching; that in the outer layer may be caused by vitreous traction on the margin of the coloboma or extension of the formerly isolated detachment through the outer marginal zone of decreased glial support.

A history of intraocular pressure rise with reference to the Nd:YAG laser

The rise in intraocular pressure after Nd:YAG laser capsulotomy is presently thought to be due to laser specific shockwaves and debris. Glaucoma has also been a frequent complication of mechanical discission as shown by a review of 84 cases from 1865-1932. Most authors have ascribed the pressure rise to vitreous or a quality of vitreous. Focusing on the disruption of the barrier between aqueous and vitreous as a common link between knife and laser discission, an attempt is made to combine the historical and recent views. It appears that apart from radiation effects, the Nd:YAG laser functions as a sharp knife and therefore shares the complications of mechanical discission, namely, glaucoma, injury to the vitreous and retinal detachment.

Retinotomy and Silicone Oil for Detachments Complicated by Anterior Inferior Proliferative Vitreoretinopathy

Aim: To describe a subset of patients with recurrent retinal detachments caused by anterior intraretinal and subretinal proliferative vitreoretinopathy (PVR), which required greater than 180° retinotomy and silicone oil tamponade. Methods: Interventional case series. Forty-one patients underwent >180° retinotomy, anterior retinectomy, removal of subretinal membranes, laser to the retinotomy edge and silicone oil tamponade. Risk factors for detachment, prior surgical history and PVR location were examined. Main outcomes included change in visual acuity, recurrent detachment and postoperative complications. Results: Cataract extraction (49%), high myopia (29%) and lattice degeneration (27%) were preoperative risk factors. The average number of prior procedures for retinal attachment was 2.3 (SD 0.9). The majority of detachments were inferior and related to anterior intraretinal and subretinal PVR. Twenty-four patients (59%) saw 20/200 or better. Eleven patients (27%) had poor vision (<20/400) at the end of follow-up. Thirty-seven retinas (90%) remained attached. Increased rates of postoperative corneal decompensation (p<0.0001) and silicone oil in the anterior chamber (p<0.0001) were statistically significant markers of poor visual outcome. Conclusions: Patients with complex PVR requiring a large retinotomy often had similar presurgical conditions. A large inferior retinotomy effectively addressed proliferations where they most frequently occur, and silicone oil was beneficial.

The Influence of Exposure Duration in Transscleral Nd:YAG Laser Cyclophotocoagulation

Transscleral cyclophotocoagulation was performed in human autopsy eyes by using three Nd:YAG lasers with different durations of exposure: a pulsed, contact laser with a duration of 0.75 millisecond and a range of one to ten pulses per burst (GLase 106, Sunrise Technologies, Fremont, California); a pulsed, noncontact laser with a duration of 20 milliseconds (Microruptor 2, Lasag Medical Lasers, Thun, Switzerland); and a continuous-wave, contact laser with durations of 700 and 2,000 milliseconds (Microruptor 3, Lasag Medical Lasers, Thun, Switzerland). Tissue responses were observed with a high-magnification videographic recording technique to analyze the immediate, real-time laser effects, and by light microscopy to characterize the laser-induced lesions further. Videographically, both pulsed lasers were noted to cause mild whitening of the pigment epithelium with frequent vaporization and explosive tissue disintegration. Histologically, the 0.75-milli-second pulse typically produced the most marked epithelial disruption, referred to as an explosive-like lesion, whereas the 20-milli-second pulse more often caused moderate tissue disruption with elevation of the epithelial layers in a blister-like lesion. In contrast, the continuous-wave laser was observed videographically to produce prominent tissue whitening and puckering, seen histologically as convolution of the epithelium and coagulation of stroma, which was called a shrinkagelike lesion. Our study suggests that exposure duration influences in vitro tissue response to transscleral Nd:YAG cyclophotocoagulation, although in vivo studies and clinical trials are needed to determine which tissue response is optimum for clinical use.

Endoscopy and biopsy of the orbit.

Summary Flexible endoscopes produce high-quality images, are small in size, and can deliver microsurgical instruments or laser probes. Early attempts at orbital endoscopy were limited by the relatively large size and poor visualization of rigid endoscopes. We performed endoscopie orbital exploration using the Olympus HYF flexible endoscope in four live dog orbits. We achieved excellent visualization of orbital structures including the globe, blood vessels, extraocular muscles, intermuscular septa, optic nerve, and fat. Visualization, hemostasis, and dissection were aided by the use of hyaluronic acid infused through the endoscope. We biopsied fat and extraocular muscle without complication using Olympus endoscopie cup biopsy forceps (confirmed by histopathologic examination). Our experience indicates that orbital endoscopy aided by viscoelastic hydrodissection may permit a less invasive approach to optic nerve sheath fenestration, tumor biopsy and treatment, and the removal of foreign bodies.

Concurrent sino-orbital aspergillosis and cerebral nocardiosis.

A 79-year-old man with myelodysplastic syndrome developed a right optic neuropathy with optic disc edema and intractable periocular pain, one month after undergoing removal of a gangrenous gallbladder. Although results of a temporal artery biopsy were negative, he was treated with prednisone for presumed temporal arteritis. Attempts at tapering the prednisone dose led to recurrence of periocular pain. On neuro-ophthalmologic evaluation six months after the prednisone treatment was begun, he had developed right fourth and sixth cranial nerve palsies, and magnetic resonance imaging demonstrated a right orbital apex mass. Trans-sphenoidal biopsy revealed Aspergillus fumigatus. During treatment of aspergillosis, the patient developed a left hemiparesis. Magnetic resonance imaging disclosed multiple ring-enhancing cerebral masses. Biopsy revealed Nocardia asteroides. The patient was successfully treated for both infections with recovery of neurologic function except for the right optic neuropathy. Although immunocompromised patients are known to be subject to multiple infections, this may be the first reported case of concurrent sino-orbital aspergillosis and cerebral nocardiosis.