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51-405: SLT may refer to: Medicine [ edit ] Selective laser trabeculoplasty , an eye surgery Speech and language therapy Technology [ edit ] For vehicles, see § Transportation . Compaq SLT , a laptop computer line of the 1980s and 1990s Sony SLT camera , a 1990s digital camera type IBM Solid Logic Technology ,

102-418: A bleb from which it is slowly absorbed. Filtering procedures are typically divided into either penetrating or non-penetrating types depending upon whether an intraoperative entry into the anterior chamber occurs. Penetrating filtering surgeries are further subdivided into guarded filtering procedures, also known as protected, subscleral, or partial thickness filtering procedures (in which the surgeon sutures

153-649: A 1960s hybrid integrated circuit design Sri Lanka Telecom , a telephone company Transportation [ edit ] Harriet Alexander Field , an airfield in Colorado, US (IATA code) Mercedes-Benz SLT-Class , a car model (built 1996–2020) South Lancs Travel , an English bus operator Sprinter Lighttrain , a Dutch electric train class (built 2007–2012) Other uses [ edit ] Slovenian tolar , defunct currency Situational leadership theory , of organizations Les Soulèvements de la Terre , French environmental collective Social learning theory ,

204-446: A dark ring encircling the iris on some individuals, but is a result of the optical properties of the region between the cornea and sclera , not of pigments in the iris. Iris color is a highly complex phenomenon consisting of the combined effects of texture, pigmentation, fibrous tissue, and blood vessels within the iris stroma , which together make up an individual's epigenetic constitution in this context. An organism's "eye color"

255-446: A laser, it is typically used to decrease intraocular pressure in patients with angle-closure glaucoma. A laser peripheral iridotomy (LPI) is the application of a laser beam to selectively burn a hole through the iris near its base. LPI may be performed with either an argon laser or Nd:YAG laser. There is currently no sufficient evidence to show any benefit on the use of iridotomy versus no iridotomy to slow down visual field loss. This

306-472: A laser. Cyclodiathermy uses heat generated from a high frequency alternating electric current passed through the tissue, while cycloelectrolysis uses the chemical action caused by a direct current . A systematic review seeking to assess the safety and effectiveness of diode transscleral cyclophotocoagulation found one study in Ghana comparing patients who received low-energy versus high-energy variations of

357-432: A peripheral iridectomy is the removal of iris tissue at the periphery; and a sector iridectomy is the removal of a wedge-shaped section of iris that extends from the pupil margin to the iris root, leaving a keyhole-shaped pupil. Clear lens extraction , a surgical procedure in which clear lens of the human eye is removed, may be used to reduce intraocular pressure in primary angle closure glaucoma. A study found that CLE

408-469: A psychological explanation for behaviour Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title SLT . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=SLT&oldid=1215301854 " Category : Disambiguation pages Hidden categories: Short description

459-520: A scleral flap over the sclerostomy site ), and full thickness procedures. Trabeculectomy is a guarded filtering procedure that removes of part of the trabecular meshwork. Full thickness procedures include sclerectomy, posterior lip sclerectomy (in which the surgeon completely excises the sclera on the area of the sclerostomy ), trephination, thermal sclerostomy (Scheie procedure), iridenclesis, and sclerostomy (including conventional sclerostomy and enzymatic sclerostomy). Anterior chamber paracentesis

510-401: A sterile, gel-like material called viscoelastic. The catheter is then removed and a suture is placed within the canal and tightened. By opening the canal, the pressure inside the eye can then be relieved. Canaloplasty has two main advantages of over more traditional glaucoma surgeries. The first of these advantages is an improved safety profile over trabeculectomy. As canaloplasty does not require

561-507: Is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing subconjunctival filtration without actually entering the anterior chamber. In order to prevent wound adhesion after deep scleral excision and maintain good filtering results, it is sometimes performed with a variety of biocompatible spacers or devices, such as the Aquaflow collagen wick, ologen Collagen Matrix, or Xenoplast glaucoma implant. Viscocanalostomy

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612-410: Is a penetrating surgical procedure done to reduce intraocular pressure of the eye. Non-penetrating filtering surgeries do not penetrate or enter the eye's anterior chamber . There are two types of non-penetrating surgeries: Bleb-forming and viscocanalostomy. Bleb forming procedures include ab externo trabeculectomy and deep sclerectomy. Ab externo trabeculectomy (AET) involves cutting from outside

663-404: Is a rarely used procedure that aims to separate the ciliary body from the sclera to form a communication between the suprachoroidal space and the anterior chamber. A cyclogoniotomy is a surgical procedure for producing a cyclodialysis, in which the ciliary body is cut from its attachment at the scleral spur under gonioscopic control. A ciliarotomy is a surgical division of the ciliary zone in

714-470: Is actually the color of one's iris, the cornea being transparent and the white sclera entirely outside the area of interest. Melanin is yellowish to dark hazel in the stromal pigment cells, and black in the iris pigment epithelium , which lies in a thin but very opaque layer across the back of the iris. Most human irises also show a condensation of the brownish stromal melanin in the thin anterior border layer, which by its position has an overt influence on

765-472: Is also an ab externo, major ocular procedure in which Schlemm's canal is surgically exposed by making a large and very deep scleral flap. In the VC procedure, Schlemm's canal is cannulated and viscoelastic substance injected (which dilates Schlemm's canal and the aqueous collector channels). Surgical adjuvants Where wound modulation is needed to prevent closure of surgically created drainage channels, adjuvants such as

816-403: Is based on analysing four studies with a sample of 3,086 eyes of 1,543 participants; iridotomy seems to improve gonioscopic findings, but does not show to be clinically significant. An iridectomy , also known as a corectomy or surgical iridectomy , involves the removal of a portion of iris tissue. A basal iridectomy is the removal of iris tissue from the far periphery, near the iris root;

867-429: Is connected to a sphincter muscle ( sphincter pupillae ), which contracts the pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ), which pull the iris radially to enlarge the pupil, pulling it in folds. The sphincter pupillae is the opposing muscle of the dilator pupillae. The pupil's diameter, and thus the inner border of the iris, changes size when constricting or dilating. The outer border of

918-401: Is different from Wikidata All article disambiguation pages All disambiguation pages Glaucoma surgery#Laser trabeculoplasty A trabeculoplasty is a modification of the trabecular meshwork . Laser trabeculoplasty (LTP) is the application of a laser beam to burn areas of the trabecular meshwork, located near the base of the iris, to increase fluid outflow. LTP is used in

969-444: Is even more effective than laser peripheral iridotomy in patients with angle closure glaucoma. Filtering surgeries are the mainstay of surgical treatment to control intraocular pressure. An anterior sclerotomy or sclerostomy is used to gain access to the inner layers of the eye in order to create a drainage channel from the anterior chamber to the external surface of the eye under the conjunctiva, allowing aqueous to seep into

1020-415: Is seen; if not, they will remain blue or gray. All the contributing factors towards eye color and its variation are not fully understood. Autosomal recessive/dominant traits in iris color are inherent in other species, but coloration can follow a different pattern. Heterochromia (also known as a heterochromia iridis or heterochromia iridum) is an ocular condition in which one iris is a different color from

1071-406: The depth of field . Very few humans possess the ability to exert direct voluntary control over their iris muscles, which grants them the ability to dilate and constrict their pupils on command. However, there is no clear purpose or advantage to this. The iris is usually strongly pigmented , with the color typically ranging between brown, hazel, green, gray, and blue. Occasionally, the color of

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1122-529: The First was dubbed dikoros (having two irises) for his patent heterochromia since his right iris had a darker color than the left one. In contrast, heterochromia and variegated iris patterns are common in veterinary practice. Siberian Husky dogs show heterochromia, possibly analogous to the genetically determined Waardenburg syndrome of humans. Some white cat fancies (e.g., white Turkish Angora or white Turkish Van cats) may show striking heterochromia, with

1173-484: The anterior chamber angle. Although an endoscopic goniotomy, which employs an endoscope to view the anterior chamber angle, may be performed, a trabeculotomy which accesses the angle from the exterior surface of the eye, thereby eliminating the need for a clear cornea, is usually preferred in these instances. A specially designed probe is used to tear through the trabecular meshwork to open it and allow fluid flow. Tube-shunt surgery or drainage implant surgery involves

1224-443: The anterior ciliary body provide a secondary pathway for aqueous humour to drain from the eye. The iris is divided into two major regions: The collarette is the thickest region of the iris, separating the pupillary portion from the ciliary portion. The collarette is a vestige of the coating of the embryonic pupil. It is typically defined as the region where the sphincter muscle and dilator muscle overlap. Radial ridges extend from

1275-619: The blood vessels, collagen in the vessel and stroma) is the most important element. Rayleigh scattering and Tyndall scattering , (which also happen in the sky) and diffraction also occur. Raman scattering , and constructive interference , as in the feathers of birds, do not contribute to the color of the eye, but interference phenomena are important in the brilliantly colored iris pigment cells ( iridophores ) in many animals. Interference effects can occur at both molecular and light-microscopic scales, and are often associated (in melanin-bearing cells) with quasicrystalline formations, which enhance

1326-497: The creation of a bleb, significant long-term risks such as infection and hypotony (extremely low eye pressure) are avoided. The second main advantage is that when combined with cataract surgery, the IOP is reduced even further than when done alone. Long term (three year) results have been published both in the US and Europe demonstrating a significant and sustained reduction in both eye pressure and

1377-492: The eye inward to reach Schlemm's canal , the trabecular meshwork, and the anterior chamber. Also known as non-penetrating trabeculectomy (NPT), it is an ab externo (from the outside), major ocular procedure in which Schlemm's canal is surgically exposed by making a large and very deep scleral flap. The inner wall of Schlemm's canal is stripped off after surgically exposing the canal. Deep sclerectomy, also known as nonpenetrating deep sclerectomy (PDS) or nonpenetrating trabeculectomy,

1428-411: The iris does not change size. The constricting muscle is located on the inner border. The back surface is covered by a heavily pigmented epithelial layer that is two cells thick (the iris pigment epithelium), but the front surface has no epithelium. This anterior surface projects as the dilator muscles. The high pigment content blocks light from passing through the iris to the retina, restricting it to

1479-405: The iris is due to a lack of pigmentation, as in the pinkish-white of oculocutaneous albinism , or to obscuration of its pigment by blood vessels, as in the red of an abnormally vascularised iris. Despite the wide range of colors, the only pigment that contributes substantially to normal iris color is the dark pigment melanin . The quantity of melanin pigment in the iris is one factor in determining

1530-502: The iris is the diaphragm . Eye color is defined by the iris. The word "iris" is derived from the Greek word for " rainbow ", also its goddess plus messenger of the gods in the Iliad , because of the many colours of this eye part. The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, behind the stroma, pigmented epithelial cells. The stroma

1581-419: The layers of the iris are: The stroma and the anterior border layer of the iris are derived from the neural crest , and behind the stroma of the iris, the sphincter pupillae and dilator pupillae muscles, as well as the iris epithelium, develop from optic cup neuroectoderm. The iris controls the size of the pupil by means of contracting the iris sphincter muscle and/or the iris dilator muscle . The size of

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1632-452: The most common pattern being one uniformly blue, the other copper, orange, yellow, or green. Striking variation within the same iris is also common in some animals, and is the norm in some species. Several herding breeds, particularly those with a blue merle coat color (such as Australian Shepherds and Border Collies ) may show well-defined blue areas within a brown iris, as well as separate blue and darker eyes. Some horses (usually within

1683-483: The number of glaucoma medications required for glaucoma control. Certain cells within the eye's ciliary body produce aqueous humor. A ciliary destructive or cyclodestructive procedure is one that aims to destroy those cells in order to reduce intraocular pressure. Cyclocryotherapy , or cyclocryopexy, uses a freezing probe. Cyclophotocoagulation , also known as transscleral cyclophotocoagulation, ciliary body ablation, cyclophotoablation, and cyclophototherapy, uses

1734-406: The ologen collagen matrix implants may be used to facilitate healthy tissue regeneration. Scar formation at the site of excision or operation may block aqueous humor circulation, while healthy tissue regeneration will keep newly created drainage channels functional. Goniotomy and trabeculotomy are similar simple and directed techniques of microsurgical dissection with mechanical disruption of

1785-446: The optical effects. Interference is recognised by characteristic dependence of color on the angle of view, as seen in eyespots of some butterfly wings , although the chemical components remain the same. White babies are usually born blue-eyed since no pigment is in the stroma, and their eyes appear blue due to scattering and selective absorption from the posterior epithelium. If melanin is deposited substantially, brown or black color

1836-410: The other iris (complete heterochromia), or where the part of one iris is a different color from the remainder (partial heterochromia or sectoral heterochromia). Uncommon in humans, it is often an indicator of ocular disease, such as chronic iritis or diffuse iris melanoma, but may also occur as a normal variant. Sectors or patches of strikingly different colors in the same iris are less common. Anastasius

1887-414: The other stromal components. Sometimes, lipofuscin , a yellow "wear and tear" pigment, also enters into the visible eye color, especially in aged or diseased green eyes. The optical mechanisms by which the nonpigmented stromal components influence eye color are complex, and many erroneous statements exist in the literature. Simple selective absorption and reflection by biological molecules ( hemoglobin in

1938-510: The overall color. The degree of dispersion of the melanin, which is in subcellular bundles called melanosomes , has some influence on the observed color, but melanosomes in the iris of humans and other vertebrates are not mobile, and the degree of pigment dispersion cannot be reversed. Abnormal clumping of melanosomes does occur in disease and may lead to irreversible changes in iris color (see heterochromia , below). Colors other than brown or black are due to selective reflection and absorption from

1989-455: The periphery to the pupillary zone, to supply the iris with blood vessels. The root of the iris is the thinnest and most peripheral. The muscle cells of the iris are smooth muscle in mammals and amphibians, but are striated muscle in reptiles (including birds). Many fish have neither, and, as a result, their irises are unable to dilate and contract, so that the pupil always remains of a fixed size. From anterior (front) to posterior (back),

2040-413: The phenotypic eye color of an organism. Structurally, this huge molecule is only slightly different from its equivalent found in skin and hair . Iris color is due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes. More of the former is found in brown-eyed people and of the latter in blue- and green-eyed people. The limbal ring appears as

2091-398: The placement of a tube or glaucoma valves to facilitate aqueous outflow from the anterior chamber. Trabeculopuncture uses a Q switched Nd:YAG laser to punch small holes in the trabecular meshwork. Goniocurretage is an "ab interno" (from the inside) procedure that used an instrument "to scrape pathologically altered trabecular meshwork off the scleral sulcus". A surgical cyclodialysis

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2142-478: The procedure to treat glaucoma. Overall, the review found that 47% of eyes treated with transscleral cytophotocoagulation saw an IOP decrease of at least 20%. There were no differences between the low-energy and high-energy variations of the procedure in all reported outcomes, such as IOP control, and number of medications used after treatment. Another Cochrane Systematic Review explored whether cyclodestructive procedures are better than other glaucoma treatments for

2193-494: The pupil. The outer edge of the iris, known as the root, is attached to the sclera and the anterior ciliary body . The iris and ciliary body together are known as the anterior uvea . Just in front of the root of the iris is the region referred to as the trabecular meshwork , through which the aqueous humour constantly drains out of the eye, with the result that diseases of the iris often have important effects on intraocular pressure and indirectly on vision. The iris along with

2244-401: The pupils is dependent on many factors (including light, emotional state, cognitive load, arousal, stimulation), and can range from less than 2 mm in diameter, to as large as 9 mm in diameter. However, there is considerable variation in maximal pupil diameter by individual humans, and decreases with age. The irises also contract the pupils when accommodation is initiated, to increase

2295-480: The structure of the trabecular meshwork (based on electron microscopy) to the same extent, so retreatment may be possible if the effects from the original treatment should begin to wear off, although this has not been proven in clinical studies. ALT is repeatable to some extent with measurable results possible. An iridotomy involves making puncture-like openings through the iris without the removal of iris tissue. Performed either with standard surgical instruments or

2346-442: The trabecular meshwork and create less thermal damage than ALT. SLT shows promise as a long-term treatment. In SLT a laser is used to selectively target the melanocytes in the trabecular meshwork. Though the mechanism by which SLT functions is not well understood, it has been shown in trials to be as effective as the older ALT. However, because SLT is performed using a laser with much lower power than ALT, it does not appear to affect

2397-402: The trabecular meshwork. Goniotomy procedures include surgical goniotomy and laser goniotomy. A surgical goniotomy involves cutting the fibers of the trabecular meshwork to allow aqueous fluid to flow more freely from the eye. Laser goniotomy is also known as goniophotoablation and laser trabecular ablation . In many patients with congenital glaucoma, the cornea is not clear enough to visualize

2448-408: The treatment of glaucoma. Canaloplasty is a nonpenetrating procedure utilizing microcatheter technology. To perform a canaloplasty, an incision is made into the eye to gain access to Schlemm's canal in a similar fashion to a viscocanalostomy. A microcatheter will circumnavigate the canal around the iris, enlarging the main drainage channel and its smaller collector channels through the injection of

2499-400: The treatment of refractory glaucoma; however, the evidence was inconclusive. Iris (anatomy) The iris ( pl. : irides or irises ) is a thin, annular structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil , and thus the amount of light reaching the retina . In optical terms, the pupil is the eye's aperture , while

2550-404: The treatment of various open-angle glaucomas. The two types of laser trabeculoplasty are argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). As its name suggests, argon laser trabeculoplasty uses an argon laser to create tiny burns on the trabecular meshwork. Selective laser trabeculoplasty is newer technology that uses a Nd:YAG laser to target specific cells within

2601-446: The white, spotted, palomino, or cremello groups of breeds) may show amber, brown, white and blue all within the same eye, without any sign of eye disease. One eye with a white or bluish-white iris is also known as a "walleye". Iridology (also known as iridodiagnosis) is an alternative medicine technique whose proponents believe that patterns, colors, and other characteristics of the iris can be examined to determine information about

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