bluuebunny/crossref_metadata_2025 huggingface dataset:
Dealing with Our Climate
Authors: van Santen Rutger , Khoe Djan , Vermeer Bram
Published: November 2020

We’re standing by the observatory at the top of the Telegrafenberg (Telegraph Hill) in the German city of Potsdam. The neoclassical building towers over its surroundings. The hill is situated in the former German Democratic Republic, close to the place where the Berlin Wall once stood. Through the slight haze, we can make out the contours of Berlin and the smoking chimneys of power stations. To our right is another hill, the Teufelsberg, with an American listening post as a relic of the cold war. Successive kaisers developed the Telegraph Hill in the nineteenth century, building a community of leading scientists there. Karl Schwarzschild used the telescope to produce his star catalog, the first in the world, while in the basement of the same building some 30 years earlier, Albert Michelson had studied light, measuring its speed and identifying certain inexplicable characteristics in the process. Albert Einstein worked here, too, basing his special theory of relativity on Michelson’s discoveries. “Fundamental natural phenomena have been isolated at this place,” says Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research, which now occupies the brow of the Telegraph Hill. “For many years, scientists have withdrawn to the quiet of this hill to develop their ideas. My task today is to reverse that movement: Rather than isolating it, we want to bring knowledge together. And instead of withdrawing from the world, we have to engage with it—to make clear to people just where our climate is headed.” Schellnhuber has thrown himself into that task with considerable verve. He has been discussing scientific issues with German chancellor Angela Merkel, for instance. He knows that his climate message is a complex one, which is why Schellnhuber avoids statistically detailed predictions and focuses instead on a number of crucial “tipping points.” “How much change can the earth sustain? Can we afford to allow the West African monsoon to collapse? Or the Himalayan glaciers to melt away? Will we be able to preserve the ice in the Antarctic? What happens if the Amazon rainforest disappears?”
Improving Energy Effi ciency
Authors: van Santen Rutger , Khoe Djan , Vermeer Bram
Published: November 2020

Imminent climate change is indeed an “inconvenient truth” that will oblige us to alter our energy use long before we begin to experience any shortage of crude oil or natural gas. Warnings about our climate come at a time when nothing would otherwise appear to stop us from using fossil energy sources for several more decades. Indeed, never before in the history of our civilization has the outlook for our continuing use of mineral oil looked so comforting. In the early 1970s, there were only 25 years’ worth of known oil reserves at the consumption levels of the time. Now, at the end of the first decade of the twenty-first century, we can look forward to 42 more years of oil, even though consumption rates have almost doubled in comparison to the 1970s. Newly discovered oilfields and technologies have more than compensated for increasing demand. Known reserves are now at their highest level since we began to keep systematic statistics. That doesn’t mean that progress with regard to our energy supply will be smooth; changes come in shocks, as we will see in this chapter. We are likely to witness crisis after crisis in the years ahead. And the tangible heating of our Earth will make the crises worse. There has been a passionate worldwide debate for decades now about the precise timing of peak oil—the moment when oil production hits its maximum level and then begins to decline until there is no longer any left that is economically viable to extract. Yet peak oil predictions invariably prove incorrect. Each time, it turns out we can extract more oil from the ground than we previously thought. One alarming calculation after another has fallen by the wayside, as we also showed in the introduction to this book (chapter 0.2). Outbreaks of panic well up with each new wave in energy prices. Just before the credit crisis of 2008, oil prices were at a record high, and prophecies of the end of the oil era were abundant.
Our Assistants
Authors: van Santen Rutger , Khoe Djan , Vermeer Bram
Published: November 2020

Canadian media guru Marshall McLuhan predicted the rise of the “global village” back in 1962. Time and space, he said, would cease to be barriers to communication, enabling people to form relationships on a worldwide basis. In the past 10 years, rapid growth in communication opportunities has validated much of his analysis. All the same, the world has not turned into one great village. Whole regions of our planet have been excluded, as we can see from the map of the world’s Internet connections. The major links bypass the continent of Africa. From the Atlantic Ocean, they touch the Cape of Good Hope before arcing onward to the Pacific, with just the occasional minor branch to the African coast. They look much like the trade routes of the old Dutch and English East India Companies, in fact. A cable running through Africa would be far too vulnerable, even assuming that any local people or businesses could afford fast Internet connections in the first place. So it is that an entire continent can miss out on the communication revolution, causing it in turn to be shunned by the business world. Software firms develop their programs in China and India rather than in Cameroon. A denser network of communications could give people a greater opportunity to participate in the global economy. It might also give them more control over their water supplies or provide them with early signals of global change. Many other problems that humans face are technical in nature, as are the tools we need to confront them. Microelectronics offers tools to better monitor our health. And more flexible, error-aware computers could steer us away from crises. We need tools that are responsive and ubiquitous. We need to measure and control larger areas on a shorter timescale and with much greater accuracy than is currently possible. We still don’t have enough sensors to monitor our climate or imminent earthquakes. We consume too much energy and too many raw materials in our manufacturing plants because we don’t know how to control the processes more accurately.
Prospects of Cities
Authors: van Santen Rutger , Khoe Djan , Vermeer Bram
Published: November 2020

There’s a greater than 50 percent chance that when you look through your window, what you see is a landscape of concrete, asphalt, and cars. More than half the world’s population lives in cities, and the proportion is increasing—as are the problems associated with progressively denser and more aggregated communities. As we move further into the twenty-first century, the urban transition will gradually draw to a close after two centuries that transformed the human population from an agrarian society scattered over the surface of the earth to the highly compressed life of the city. The growth of urban living is one of the greatest paradoxes of our age. New technologies offer companies and individuals an unprecedented degree of locational freedom and mobility. We are increasingly able to see, hear, and sense one another, even when we are thousands of kilometers apart. More than ever people choose to live in close vicinity of each other, as if there were no other possibility to communicate. Once most people live in cities the urban landscape will have become the dominant habitat for human beings and explosive urbanization will inevitably come to an end. We will then enter an era of posturbanization in which the city will have to find a new dynamic. Growth will no longer come by drawing people in from outside. Will cities maintain their scale? Or will urbanization go into reverse, turning downtown Shanghai, Mumbai, and Chicago into wastelands as the twenty-first century progresses? Detroit offers a glimpse of what happens when a city ceases to breathe. What used to be a theater is now a parking lot; the residual population grows vegetables on former city squares; empty office blocks gradually succumb to the weather; the car industry has collapsed, and nothing has emerged to replace it. How can we prevent cities from falling apart under their own weight? Everywhere in a city, you’ll probably hear the growling and snarling of an urban street. You feel its heartbeat. The city’s hunger never wanes: It eats up its surroundings and excretes a constant flow of waste.
Late Bleb Failure
Authors: Chang Peter T.
Published: November 2020

The goal of filtering surgery is to create a filtering bleb to lower intraocular pressure (IOP). A successful bleb can be characterized by subconjunctival elevation, moderate avascularity, and microcystic appearance of the bleb. Failure of the filtering bleb may occur in the late postoperative period, leading to inadequate control of glaucoma. (Figure 15.1) Prevention and management of late postoperative bleb failure are important in maintaining the success of the trabeculectomy. Bleb failure may occur months to years following an initial filtering surgery. Some risk factors for bleb failure include young age, high preoperative IOP, African or Hispanic ethnicity, multiple prior conjunctival procedures, long-term therapy with topical glaucoma medications, and secondary glaucomas, such as uveitic and neovascular glaucoma. Male gender and aphakia also increase the risk of late bleb failure. Structurally, bleb failure may be due to numerous causes, including obstruction of the internal ostium, episcleral fibrosis, and conjunctival scarring. Evaluation of the etiology of the failure requires careful slit-lamp biomicroscopy and gonioscopy. Although obstruction of the internal ostium typically occurs during the early postoperative period, materials such as blood and fibrin may block the ostium years after the surgery. Therefore, gonioscopy should be performed in all suspected cases of late bleb failure. Retained lens material and ophthalmic viscoelastic devices can occlude the ostium following a cataract surgery in a previously filtered eye. In cases of Axenfeld-Rieger syndrome and iridocorneal endothelial (ICE) syndrome, iris or other aberrant tissue may also cause obstruction of the internal ostium, leading to a higher rate of bleb failure. Physical manipulation using a 30-gauge needle, laser contracture (with argon or diode) or obliteration (with Nd:YAG), or topical pharmacological intervention with pilocarpine and phenylephrine may be attempted to dislodge incarcerated iris from the internal ostium. Blood clots or fibrin can be dissolved with intracameral injection of tissue plasminogen activator (tPA) (see Chapter 5). Despite the use of adjunctive antimetabolites with filtration surgeries, conjunctival scarring and episcleral fibrosis around the scleral flap remain the primary causes of late bleb failure. Histopathology of a scarred filtration site shows abundant fibroblasts with contractile intracellular proteins and deposition of new collagen fibers.
Dysesthetic Blebs
Authors: Goldsmith Jason A.
Published: November 2020

Mild, chronic ocular irritation following trabeculectomy is common and can manifest as a constant annoyance of bleb awareness with blinking; however severe debilitating discomfort can also occur. Bleb-related dysesthesia is an ocular surface disorder where a glaucoma filtering bleb interferes with lid function and tear film distribution such that signs and symptoms similar to dry eye syndrome may result. Proper prevention and management of dysesthetic blebs is crucial for success of a trabeculectomy. Utilizing a self-report questionnaire, Budenz et al found that chronic ocular discomfort exists in a majority of patients with filtering blebs ; however, many patients do not disclose mild bleb dysesthesia unless specifically questioned because they have either adapted to the symptoms or because of ascertainment bias. Additionally, the symptoms associated with bleb dysesthesia may be attributed to other common ocular surface disorders. Treatment directed at those disorders may effectively relieve symptoms of dysesthesia, so that the physician underestimates prevalence of the true etiology. More symptomatic and disabling forms of bleb-related dysesthesia are generally associated with larger, dysmorphic blebs, including 1) markedly elevated, anteriorly located (Figure 18.1), and thin-walled, ischemic blebs limited in their lateral and posterior flow by circumferential conjunctival scarring (“ring of steel”); 2) large and exuberant filtering blebs that extend into the interpalpebral fissure (Figure 18.2) and occasionally circumferentially; and 3) blebs that overhang the cornea (Figure 18.3) . These bleb dysmorphologies typically develop slowly over time as the result of scarring and tissue remodeling. Blebs that extend into the interpalpebral fissure generally occur in the early postoperative period and may or may not be related to overfiltration. Other factors that contribute to bleb-related dysesthesia include chronic irritation of the palpebral conjunctiva and exposure of the bulbar conjunctiva protruding between the eyelids and rubbing on the lid margins. Breakdown of the epithelium on the surface of ischemic blebs may result from altered tear film composition as aqueous passes across the bleb. The formation of a semicircular wall of scar tissue limiting posterior flow may result in a high, dysesthetic bleb due to inflation, expansion, and thinning of the roof of the bleb.
Hyphema
Authors: Wollan Peter T.
Published: November 2020

One of the most common complications of filtering surgery is postoperative anterior chamber bleeding, or hyphema. Rates of postoperative hyphema in the literature vary, but have been reported to be up to 53%. However, recent data from the Tube Versus Trabeculectomy Study found that postoperative hyphema occurred in only 8% of eyes (8 of 105 eyes), possibly a sign of improving surgical technique. The severity of hyphema after trabeculectomy varies greatly. Bleeding in the anterior chamber may be so mild that visual acuity and surgical outcome are unaffected. On the other hand, a total hyphema may obstruct the visual axis and potentially result in fibrosis and failure of the filtering procedure. Furthermore, some patients with glaucoma who require surgical intervention also have visual impairment or blindness in the fellow eye. Loss of vision from hyphema in the operated eye, even if only temporary, can be functionally, and possibly psychologically, debilitating to the patient. The first step in reducing the risk for hyphema is obtaining a good medical history. Does the patient have any bleeding disorders, such as hemophilia or thrombocytopenia? Is the patient taking any medications that interfere with clotting or platelet aggregation, such as aspirin, clopidogrel, and/or warfarin? The use of antiplatelet and anticoagulation therapy is associated with a higher incidence of hyphemas. Platelets stop bleeding by plugging the hole in the broken vessel wall. Alternatively, antiplatelet medications inhibit platelet aggregation and therefore prolong bleeding time. Aspirin permanently alters developing platelets, and therefore its antiplatelet effect lasts until the complete cohort of affected platelets is turned over, approximately 2 weeks. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit platelet aggregation in a manner similar to aspirin, but the effect is to existing circulating platelets only and wears off in 2–3 days. Ticlopidine (i.e., Ticlid; Roche Laboratories, Inc., Nutley, New Jersey) and clopidogrel (i.e., Plavix; Bristol-Myers Squibb/Sanofi Pharmaceuticals Partnership, Bridgewater, New Jersey) also affect platelet aggregation by binding to the P2Y , resulting in irreversible platelet inhibition.
Scleral Perforation
Authors: Rivera-Velez Jorge L.
Published: November 2020

Scleral perforation during tube shunt implantation is a rare complication. In a recent publication of the Tube Versus Trabeculectomy Study, 3 out of 107 patients in the tube shunt group had scleral perforation during placement of a device. Merino-de-Palacios et al reported scleral perforation during tube shunt surgery in 1 of 86 eyes. The type of device used does not seem to be important in the incidence of scleral perforation. In the Tube Versus Trabeculectomy Study, Baerveldt® devices (Abbott Medical Optics, Inc., Santa Ana, California) were used exclusively, and Ahmed™ Glaucoma Valves (New World Medical, Inc., Rancho Cucamonga, California) and Molteno® implants (Molteno Ophthalmic, Ltd., Dunedin, New Zealand) were used in the study by Merino-de-Palacios et al. Serious sequelae, such as endophthalmitis or retinal detachment, have not been reported in recent literature following scleral perforation during tube shunt placement; nonetheless, this complication should be prevented and, if it does occur, managed promptly. Patients who are believed to have an increased risk for scleral perforation are myopic patients (>-6.00 D) and patients with previous extraocular muscle surgery. Patients with previous scleral buckle surgery, autoimmune diseases, scleritis, or any other conditions that cause or perpetuate thinning of the sclera potentially increase the risk. Patients with previous scleral buckling procedures who require tube shunt surgery will benefit from having the device anchored behind the buckle or directly over the buckle. No attempt should be made to dissect under the buckling device, as dissection may lead to the buckle anchoring sutures perforating the eye. The most common site for tube shunt implantation is the superotemporal quadrant, between the superior and lateral rectus muscles. This location offers the benefit of having the implant hidden under the superior eyelid, no oblique muscles in the region, and better intraoperative exposure, allowing the surgeon to place the implant farther from the limbus. The plate of the implant is usually attached to the sclera approximately 8–10 mm posterior to the limbus. This is also the thinnest portion of the sclera. Exposure when implanting the tube shunt is probably the most important factor in avoiding scleral perforation.
Inadequate Conjunctival Coverage
Authors: Lawrence Scott D. , Netland Peter A.
Published: November 2020

Successful tube shunt surgery requires adequate coverage of the implant with conjunctiva. When a patient’s conjunctiva is tight or scarred, preventing exposure of the large plate and tube becomes difficult. In these challenging cases, the glaucoma surgeon must modify the surgical approach and apply surgical techniques that may be more familiar to cornea and oculoplastic surgeons than glaucoma surgeons. Any patient who has undergone ocular surgery involving the conjunctiva (e.g., cataract extraction through a scleral tunnel, guarded filtration surgery, pars plana vitrectomy, penetrating keratoplasty, pterygium excision, strabismus surgery) is likely to have conjunctival scarring. Additionally, patients with a history of inflammation of the conjunctiva may have thin, friable tissue that is difficult to manipulate. Other conditions that may lead to inadequate conjunctiva for coverage are chronic conjunctivitis, chemical burns, ocular cicatricial pemphigoid, Stevens-Johnson syndrome, and rheumatoid arthritis. In cases with marginal conjunctiva, the required conjunctival incisions and dissection for implantation of the device are performed, followed by assessment of the amount and viability of tissue. Only when adequate tissue is found should the shunt be placed. If adequate tissue is not available, the procedure may be aborted for an alternate choice. When a careful slit-lamp exam reveals conjunctival scarring to be localized, one may choose, preoperatively, to insert the tube shunt in an unaffected quadrant. However, in some instances, this approach is not possible due to diffuse scarring. Previous glaucoma surgery or posterior segment surgery (e.g., pars plana vitrectomy with silicone oil) may necessitate placement of the implant in a specific quadrant. When scarring affects the limbus, it may be difficult to initiate dissection of a fornix-based conjunctival flap without creating conjunctival buttonholes. Alternatives include making a more posterior limbus-based conjunctival flap, creating a superficial partial-thickness scleral flap, or even removing the scarred conjunctiva/Tenon’s layers and covering the defect with a conjunctival advancement flap. If upon examination the conjunctiva at the limbus cannot be easily mobilized with a sponge or blunt forceps, a limbus-based flap may be fashioned by making the initial incision 4–8 mm posterior to the limbus.
Elevated IOP and Intentional Tube Occlusion
Authors: Gross Ronald L.
Published: November 2020

Intrinsic to glaucoma surgery using a tube shunt is the management of early postoperative hypotony. This consideration is unavoidable in all cases when using a tube shunt without an intrinsic valve and must still be considered in tube shunts that contain a valve, as the valve may not function as anticipated. Unfortunately, in the attempt to avoid hypotony and its associated complications, we are faced with elevated intraocular pressure (IOP) and its associated difficulties. However, the attempt to control IOP is not the only consideration when anticipating intentional tube occlusion. Additional factors such as technical complexity of the procedure, predictability of IOP in the early postoperative period, potential to reverse occlusion either partially or completely, and the impact on the long-term function of the tube shunt must be considered. The desired endpoint when occluding a tube intentionally is the complete prevention of flow to the tube shunt reservoir. The standard ways to occlude the tube are an external encircling ligature or an internal occluding suture, otherwise known as an “obturator” or a “ripcord,” or some combination thereof. With the external suture technique, prior to placing the reservoir, a 7–0 or 8–0 polyglactin 910 (Vicryl™ , Ethicon, Inc., Somerville, New Jersey) suture is tightly tied around the tube approximately 4–6 mm from the reservoir (Figure 35.1). It is anticipated that this suture will dissolve in about one month, opening the tube. However, the timing of opening may be highly variable between individuals, and that variability may be problematic. Alternatively, a 9–0 polypropylene suture can be placed around the tip of an anterior chamber tube with release performed by laser lysis. To prevent the polypropylene suture from floating freely in the anterior chamber after release, a pass should be made through the wall of the tube during placement. Alternatively, with the “ripcord” technique, the end of a 3–0 polypropylene suture without the needle is threaded into the distal opening of the tube at the reservoir for a distance of 4–6 mm.
Late Hypotony
Authors: McMenemy Matthew G.
Published: November 2020

As with all surgeries, numerous complications can occur with tube shunts; one particular complication is hypotony. Early hypotony is defined as intraocular pressure (IOP) of less than 6 mm Hg and occurs before maturation of the fibrotic capsule around the tube shunt plate. The physiologic development of the capsule typically occurs during the first postoperative 4–6 weeks after implantation. Late hypotony can be defined as IOP of less than 6 mm Hg that occurs after the plate is encysted. Hypotony in and of itself may not require treatment unless secondary complications develop (see Chapter 10 and 34). Untreated, hypotony can result in shallowing or flattening of the anterior chamber, corneal decompensation (see Chapter 40), peripheral anterior synechiae, cataract, maculopathy (see Chapter 22), optic nerve edema, choroidal effusion or hemorrhage (see Chapter 6), and even endophthalmitis (see Chapter 42). Although hypotony is common in the early postoperative period, it is less common as a late complication. Knowing how to prevent and manage late hypotony is essential for long-lasting surgical success. Persistent hypotony is less common with tube shunts than with trabeculectomy. In the Tube Versus Trabeculectomy Study, of the 107 eyes in the tube group, none had persistent hypotony, whereas of the 105 eyes in the trabeculectomy group, 3 developed persistent hypotony. A pediatric population study comparing trabeculectomy with mitomycin-C (24 eyes) with Ahmed™ (New World Medical, Inc., Rancho Cucamonga, California) or Baerveldt® (Abbott Medical Optics, Inc., Santa Ana, California) shunts (46 shunts total) had one eye in the trabeculectomy group with late hypotony, while no eyes in shunt group developed persistent hypotony. WuDunn et al implanted 250 mm Baerveldt® devices in 108 patients, with 5 failing due to persistent hypotony. In all likelihood, late hypotony in the WuDunn et al study was due to either progression of underlying disease resulting in less aqueous production or secondary to another complication of shunt surgery. However, across the different types of shunts, the incidences of early and late hypotony are not significantly different.
Axial Length Changes
Authors: Oram Osman
Published: November 2020

The biometric changes of the human eye with lowered intraocular pressure (IOP), like those observed after glaucoma surgery, have been investigated by in vivo studies. Leydolt et al demonstrated IOP-dependent axial eye length changes in human eyes. An axial eye length decrease of 2 μm/mm Hg with short-term reduction of IOP was observed. They suggested that this concomitant shortening of axial length and IOP reduction could be a result of a decrease in scleral length owing to the reduced IOP or an increase in choroidal blood flow compensating the reduced ocular fundus pulsations during the increased IOP phase. In another in vivo study, Read et al showed that axial length underwent significant variation over a 24-hour period in normal human eyes, and a significant association existed between the change in axial length and the change in IOP, as measured by dynamic contour tonometry. The association observed between IOP and axial length was found to be consistent with the hypothesis of passive expansion and contraction of the globe in response to IOP. Studies on trabeculectomy patients, performed with or without cataract extraction, have shown a significant decrease of axial length after surgery, correlated with IOP reduction. Similarly, IOP lowering after tube shunt surgery may produce a decrease in axial length that is dependent on the amount of IOP lowering. Understanding how axial length changes impact clinical decisions, such as lens power choice for cataract surgery, is important for treating patients after glaucoma surgery or patients who have had previous glaucoma surgery. Table 41.1 summarizes reported axial length changes following different types of trabeculectomy procedures. Nemeth and Horoczi noted decreased axial length and increased thickness and volume of the ocular wall 4 days after trabeculectomy. In a retrospective study, Cashwell and Martin found a significant decrease in axial length (mean: 0.423 mm, range: 2.8 to +0.5 mm) after successful initial trabeculectomy in 62 patients using ultrasound biometry. Preoperative factors found to be associated with a greater decrease in axial length were young age, myopia, exposure to an antimetabolite, and a post-trabeculectomy IOP drop greater than 30 mmHg.
Tube Shunt Related Complications of the Orbit
Authors: Criden Marc R.
Published: November 2020

Orbital complications during or after glaucoma filtering or tube shunt surgery are relatively rare but may pose a significant treatment challenge or threat to vision. The incidence of complications is highly variable, and transient events may not be reported as frequently as those that persist. A variety of orbital complications occur following glaucoma surgery. Complications may be categorized as mechanical, infectious, neurogenic, or myogenic. However, each complication may be multimodal and fall into more than one category. Mechanical complications are the most frequent type of orbit complication related to glaucoma surgery and more specifically to tube shunt implantation. Mechanical complications include ptosis, lid retraction, strabismus, and proptosis. Several theories address why ptosis may occur after ocular surgery and why it may be either transient or permanent. The levator muscle may be damaged or dehisced by an eyelid speculum, leading to a lid droop. Bridle sutures, which are often used during glaucoma surgery, have also been implicated as they apply counter traction against the superior rectus muscle. Prolonged eyelid edema and local anesthesia have each been more strongly associated with postoperative ptosis. For more information on ptosis, see Chapter 25. Strabismus after tube shunt implantation is most commonly related to either the device itself or to scarring and fibrosis that develop postoperatively. Transient strabismus may be related to swelling or edema of local tissues and may also follow retrobulbar injection. The strabismus is usually incomitant and does not present with a characteristic pattern of deviation; thus, prisms and other nonsurgical treatments are seldom adequate. Although strabismus following tube shunt surgery is usually transient, persistent diplopia may occur. The type of implant, size, location, and material each play a role. Implants with larger surface areas have a higher incidence of motility disturbance due to mass effect. Tube shunt plates that require placement below the rectus muscles risk direct muscle injury or adhesion scarring to the implant. In addition, a pseudo-Brown’s syndrome may be created by a superonasal implant due to interference with the superior oblique muscle function. The bleb that develops around the tube shunt reservoir can also act as a mass.
Complications Specifically Related to Trabectome® Surgery (Trabeculotomy Internal Approach)
Authors: Francis Brian A.
Published: November 2020

Current surgical therapy for open-angle glaucoma can be divided into procedures directed at decreasing aqueous inflow (such as cyclophotocoagulation) or increasing aqueous outflow. The latter group can be further subdivided into external filtering surgery (such as trabeculectomy and aqueous tube shunt implantation) and internal filtering surgery designed to enhance existing aqueous outflow pathways. Internal approaches provide an alternative to standard external filtering surgery and possibly reduce the complications, including hypotony, hypotony maculopathy, bleb leaks, blebitis, choroidal effusion and hemorrhage, bleb-related endophthalmitis, peripheral anterior synechiae (PAS) formation, posterior synechiae, cataract formation, diplopia, tube obstruction, conjunctival erosion, tube migration, corneal decompensation, and plate encapsulation. Anterior chamber angle surgery techniques include procedures performed by an internal approach (e.g., goniotomy, Trabectome® [NeoMedix Corporation, Tustin, California], trabecular stent [iStent®; Glaukos® Corp., Laguna Hills, California], excimer laser trabeculotomy) or by an external approach (e.g., canaloplasty [see Chapter 51] and viscocanalostomy). Trabeculotomy by internal approach with the Trabectome® is designed to create a direct pathway from the anterior chamber to Schlemm’s canal (SC) and the aqueous collector channels by using electrocautery to selectively ablate a portion of trabecular meshwork (TM) tissue and the inner wall of SC in order to increase aqueous outflow. The Trabectome® surgical device received FDA approval for clinical use in 2004. The system consists of 3 major components: a mobile stand with a gravity-fed bottle of balanced salt solution; a handpiece console with automated irrigation, aspiration, and microbipolar electrocautery; and a foot pedal to control these functions. The intraocular disposable handpiece (see Figure 50.1) tip contains a 19.5-gauge infusion sleeve and a 25-gauge irrigation and aspiration (I/A) port with a coupling for the ablation unit at the tip. The instrument incorporates a specially designed insulated triangular footplate that is bent at 90° at the end and is pointed in order to allow proper insertion through the TM into SC. The insulation on the footplate is made of a multilayered polymer coating that allows the instrument to glide along within the canal and protects the outer wall of SC from thermal and electrical injury.
Why Harlem Is Not a Ghetto
Authors: Zukin Sharon
Published: November 2020

It’s noon on a warm Saturday in the middle of June, and a bright sun is shining on Settepani Bakery’s sidewalk café at 120th Street and Lenox Avenue. You didn’t think to bring sunscreen to eat brunch in Harlem, so you choose a table under the red awning, put on your dark glasses, and settle down to read the menu. The small, square, white tables and lightweight aluminum chairs remind you of cafés in Italy or Greenwich Village, and the dishes on the menu also inspire dreams of other places. Smoked turkey panini with brie on pumpernickel bread. Mozzarella, tomatoes, and basil on rosemary focaccia. Bucatini pasta with an almond, basil, and tomato pesto. Cappuccino and latte, of course, but also decaf Masala chai. You understand why Settepani is popular among Harlem’s new movers and shakers. You’ve heard that Maya Angelou, the distinguished poet, playwright, and actor, who lives in a restored brownstone townhouse nearby, often has lunch here. The famous basketball champion and author Kareem Abdul-Jabbar has been seen walking by. The restaurant’s website lists former president Bill Clinton, whose office is on 125th Street, as a corporate customer. And when your graduate students stop in for coffee while doing a research project for your class, they meet Daniel Tisdale, the founder and publisher of Harlem World magazine, who is having a business meeting a few tables away, and Eric Woods, the chief financial officer of Uptown magazine and cofounder of Harlem Vintage, the neighborhood’s first wine store. Harlem has other well-known restaurants: the venerable Sylvia’s, the soul food restaurant that is on every tourist itinerary and sells its own bottled sauces; M&G Diner, known for its smothered pork chops, collard greens, and candied yams; and Amy Ruth’s, offering dishes named for local celebrities, like the waffles and bacon that honor retired police chief Joseph Leake and the chicken and waffles that pay tribute to the Rev. Al Sharpton, a friend of the former owner.
Cornea and Lens Problems in Aniridia
Authors: Holland Edward J. , Gupta Mayank
Published: November 2020

The corneal epithelium is a rapidly regenerating, stratified squamous epithelium. Homeostasis of corneal epithelial cells is an important prerequisite, not only for the integrity of the ocular surface, but also for the visual function. The maintenance of a healthy corneal epithelium under both normal and wound-healing conditions is achieved by a population of stem cells located in the basal layer of limbal epithelium. The Limbus represents the transition zone between the peripheral cornea and the bulbar conjunctiva. The stem cells from the limbus generate the transient amplifying cells that migrate, proliferate, and differentiate to replace lost or damaged corneal epithelial cells. In patients with aniridia, there is a primary dysfunction of these limbal stem cells (see Figure 6.1). The cornea is affected clinically in 90 percent of the patients with aniridia. In most cases, the cornea in aniridic patients appears normal and transparent during infancy and childhood. However, during the early teens, the cornea begins to show changes. The early changes are marked by the in-growth of opaque epithelium from the limbal region into the peripheral cornea, which represents conjunctival epithelial cells, goblet cells, and blood vessels in the corneal epithelium. These changes gradually progress toward the central cornea and may cause corneal epithelial erosions and epithelial abnormalities that eventually culminate in opacification of the corneal stroma, which leads to vision loss. With the gradual loss of limbal stem cells, the entire cornea becomes covered with conjunctival cells. Eventually, many patients develop total limbal stem cell deficiency. These abnormalities usually become more pronounced with aging. The corneal abnormalities seen in aniridia are collectively termed “aniridic keratopathy”. Significant corneal opacification may occasionally be the initial manifestation of aniridia. Abnormal tear film stability and meibomian gland dysfunction are also observed in patients with aniridia. This can lead to dry eyes, aggravating corneal erosion and ulceration observed in aniridic patients. Sometimes, aniridia is associated with “Peter’s anomaly,” in which central corneal opacity is present at birth along with defects in the corneal endothelium and Descemet’s membrane.
Teachers’ and School Administrators’ Guide
Authors: Otis Jessica J. , Nerby Jill Ann
Published: November 2020

A child with aniridia is being placed in your classroom, and you may be wondering whether their needs are different from those of your other students. This information has been written to answer any questions or concerns about this new teaching experience. When a child with a visual disability is enrolled in a regular class, careful consideration is given to assess whether he or she can compete both academically and socially. Although he or she may need to cope with visual and emotional stresses usually not encountered by non-disabled children, he or she will soon become a fully participating member of the class. In order to ensure that the child with aniridia has the opportunity to reach their full academic potential, the child and you will hopefully receive the supportive services of a special teacher of the visually impaired (VI teacher) to discuss classroom situations. A child with aniridia is generally considered eligible for special services of a resource and/or VI teacher if their measured visual acuity is 20/70 or less in the better eye with corrective lenses (in other words, if what he or she can see at twenty feet is no more than what a person with normal vision sees at seventy feet). Children who have a measured visual acuity of 20/200 or less in the better/corrected eye or who have a visual field of no greater than twenty degrees are classified as legally blind. Aniridia is a partial or complete absence of the iris, and it may be associated with other ocular defects such as macular and optic nerve hypoplasia, cataract, corneal surface abnormalities that lead to decreased vision, and nystagmus. The vision may fluctuate, depending on lighting conditions and glare. Glaucoma is a secondary problem causing additional visual loss over time. Because of poor visual acuity and nystagmus, low-vision aids are very helpful. Lifelong regular follow up care is necessary for early detection of any new problem so that timely treatment is given.
Other Support Services
Authors: Otis Jessica J.
Published: November 2020

Besides the support of Aniridia Foundation International, there are several other services for the blind and visually impaired. Parent Training and Information Centers and Community Parent Resource Centers can help parents with children who are blind or visually impaired. These centers are located all over the United States, and they help families of children and young adults with disabilities (from birth to age 22). Also, they help families obtain appropriate education and services for their children with disabilities, train and inform parents and professionals on a variety of topics, resolve problems between families and schools, and connect children with disabilities to community resources that address their needs. For more information on a center located in your state, please visit http://www.ilru.org/html/publications/directory/index.html. All websites mentioned in this chapter will be listed at the end of this chapter along with several other websites for other services and organizations that may assist you. The Lighthouse International has been helping visually impaired people since 1905. It strives to help visually impaired individuals live better lives and to be in independent. It is also dedicated to preventing disabilities. To accomplish this it has research studies, prevention efforts, advocacy initiatives, education programs, and vision rehabilitation services. For more information, please visit the Lighthouse International website at www.lighthouse.org. The Lions International began to dedicate services to the visually impaired in 1925 when Helen Keller challenged the Lions Club to be “knights of the blind in the crusade against darkness.” Today Lions is successful in helping those who are blind and visually impaired. A very important program Lions has is called SightFirst. This program was started in 1989 to help prevent blindness. Just a few of the services are helping to construct or expand eye hospitals and clinics, contributing to cataract surgeries, and providing sight-saving medication. This program is also striving to eliminate preventable childhood blindness, and to control river blindness and trachoma. For more information, please visit the Lions International website at www.lionsclubs.org.
Automated Perimetry in Glaucoma
Authors: Mayer Hylton R. , Weitzman Marc L.
Published: November 2020

Clinical experience and multiple prospective studies, such as the Collaborative Normal Tension Glaucoma Study and the Los Angeles Latino Eye Study, have demonstrated that the diagnosis of glaucoma is more complex than identifying elevated intraocular pressure. As a result, increased emphasis has been placed on measurements of the structural and functional abnormalities caused by glaucoma. The refinement and adoption of imaging technologies assist the clinician in the detection of glaucomatous damage and, increasingly, in identifying the progression of structural damage. Because visual field defects in glaucoma patients occur in patterns that correspond to the anatomy of the nerve fiber layer of the retina and its projections to the optic nerve, visual functional tests become a link between structural damage and functional vision loss. The identification of glaucomatous damage and management of glaucoma require appropriate, sequential measurements and interpretation of the visual field. Glaucomatous visual field defects usually are of the nerve fiber bundle type, corresponding to the anatomic arrangement of the retinal nerve fiber layer. It is helpful to consider the division of the nasal and temporal retina as the fovea, not the optic nerve head, because this is the location that determines the center of the visual field. The ganglion cell axon bundles that emanate from the nasal side of the retina generally approach the optic nerve head in a radial fashion. The majority of these fibers enter the nasal half of the optic disc, but fibers that represent the nasal half of the macula form the papillomacular bundle to enter the temporal-most aspect of the optic nerve. In contrast, the temporal retinal fibers, with respect to fixation, arc around the macula to enter the superotemporal and inferotemporal portions of the optic disc. The origin of these arcuate temporal retinal fibers strictly respects the horizontal retinal raphe, temporal to the fovea. As a consequence of this superior-inferior segregation of the temporal retinal fibers, lesions that affect the superotemporal and inferotemporal poles of the optic disc, such as glaucoma, tend to cause arcuateshaped visual field defects extending from the blind spot toward the nasal horizontal meridian.
Lumping and Splitting
Authors: Baldwin Peter
Published: November 2020

It Is Often Said That America is an economically more unequal society than Europe, with greater stratification between rich and poor. On average, the United States is a wealthier society than most European countries. The median American income—that earned by the recipient at the center of the income distribution—is higher than equivalent figures for all European nations other than Luxembourg (figure 189). Americans also earn higher per capita incomes, adjusted for purchasing power variations, than any Europeans other than the Norwegians. That is, of course, easily compatible with widespread poverty and inequality. If incomes are distributed unequally, a high average could hide disproportionate wealth at the top and bitter poverty at the bottom. Americans do appear to tolerate a higher degree of inequality than Europeans. True, proportionately fewer Americans believe that income differences are necessary as an incentive than do Germans, Spaniards, or the Portuguese. Fewer Americans consider it fair that the rich buy better health care and education than do the British. But a smaller proportion of Americans than any Europeans rejects existing income differences as too large. And Americans do not agree, as many Europeans do, that the government should act to narrow income inequality. On a number of measures, high inequality does, in fact, appear to hold true for the United States—though rarely as starkly as is oft en presumed. For one thing, more billionaires per capita live in America than in any European country except Switzerland, with over twice that rate (figure 190). The American market is not inherently bloodier than the European. By itself, it does not produce more inequality than across the Atlantic. Pretax income inequalities in the United States lie within the European range. But after taxes and transfers, American inequalities appear starker. One measure of this defines poverty as 60% of the national median income. By this standard, the United States has a larger percentage of poor citizens than any European country, though the figures are broadly comparable to those of the UK, Ireland, Spain, and Greece (figure 191).
A Meeting of the Twain?
Authors: Baldwin Peter
Published: November 2020

So Where Does This Leave Us? There are, of course, differences between America and Europe. But in almost all cases, they are no greater, and oft en smaller, than the differences among European nations. The span of European circumstance is such that the United States tends to fall comfortably within it. Therefore, either no coherent Europe exists, or the United States is a European nation. Formulated in a more sensible way, the similarities across the North Atlantic are at least as salient as the divergences. Yes, there are differences between Europe and America: murder and incarceration rates, as well as gun ownership and, more arguably, relative poverty rates on the one hand; the strength of civil society, assimilatory abilities, and some aspects of religious belief on the other. Other differences are ones of degree rather than kind: social policy, taxation, labor regulation, inequality, environmental policies. Other much-remarked Atlantic divides can easily be exaggerated—the death penalty, for example. Popular opinion probably does not diverge across the Atlantic as much as official policy. A joint YouGov/Economist poll found almost identical responses between Americans and the British, with about one-fifth of respondents always in favor of death for murder and about the same number always opposed. The United States still enforces the death penalty, and most Americans support it under some circumstances. Yet, 12 states do not have it, and another five have not carried it out for the last 30 years. If we add those states that have executed only five or fewer people since 1976, we find that over half the states, in effect, do not have capital punishment. It could, in theory, be revoked tomorrow. Would America then be radically different? Did France change profoundly when it abolished the death penalty in 1981? Did the UK in 1998, Belgium in 1996, Spain in 1995, Italy in 1994, or Greece in 2004? Did they only then become truly European?