PHACO SURGERY
Phacoemulsification refers to modern cataract surgery in which the eye's internal lens is emulsified with an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with irrigation of balanced salt solution, thus maintaining the anterior chamber, as well as cooling the handpiece.
Preparation and Precautions
Being a delicate organ, the eye requires extreme care before, during and after a surgical procedure. An ophthalmologist must diagnose a cataract and conduct or appropriately supervise the conduction of the operation. University programs typically allow patients to specify if they want to be operated upon by the consultant or the resident or fellow.
Proper anesthesia is a must for ocular surgery. Topical anesthesia is most commonly employed, typically by the instillation of a local anesthetic such as tetracaine or lidocaine. Alternatively, lidocaine and/or longer-acting bupivacaine anesthestic may be injected into the area surrounding (peribulbar block) or behind (retrobulbar block) the eye muscle cone to more fully immobilize the extraocular muscles and minimize pain sensation. A facial nerve block using lidocaine and bupivacaine may occasionally be performed to reduce lid squeezing.General anesthesia is recommended for children, traumatic eye injuries with cataract, for very apprehensive or uncooperative patients and animals. Cardiovascular monitoring is preferable in local anesthesia and is mandatory in the setting of general anesthesia. Proper sterile precautions are taken to prepare the area for surgery, including use of antiseptics like povidone-iodine. Sterile drapes, gowns and gloves are employed. A plastic sheet with a receptacle helps collect the fluids during phacoemulsification. An eye speculum is inserted to keep the eyelids open.
Surgical Technique
Before the phacoemulsification can be performed, one or more incisions are made in the eye to allow the introduction of surgical instruments. The surgeon then removes the anterior face of the capsule that contains the lens inside the eye. Phacoemulsification surgery involves the use of a machine with microprocessor-controlled fluid dynamics. These can be based on peristaltic or a venturi type of pump.
The phaco probe is an ultrasonic handpiece with a titanium or steel needle. The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract while the pump aspirates particles through the tip. In some techniques, a second fine steel instrument called a "chopper" is used from a side port to help with chopping the nucleus into smaller pieces. The cataract is usually broken into two or four pieces and each piece is emulsified and aspirated out with suction. The nucleus emulsification makes it easier to aspirate the particles. After removing all hard central lens nucleus with phacoemulsification, the softer outer lens cortex is removed with suction only.
An irrigation-aspiration probe or a bimanual system is used to aspirate out the remaining peripheral cortical matter, while leaving the posterior capsule intact. As with other cataract extraction procedures, an intraocular lens implant (IOL), is placed into the remaining lens capsule. For implanting a PMMA IOL, the incision has to be enlarged. For implanting a foldable IOL, the incision does not have to be enlarged. The foldable IOL, made of silicone or acrylic of appropriate power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL.
It is then inserted and placed in the posterior chamber in the capsular bag (in-the-bag implantation). Sometimes, a sulcus implantation may be required because of posterior capsular tears or because of zonulodialysis. Because a smaller incision is required, few or no stitches are needed and the patient's recovery time is usually shorter when using a foldable IOL.
Preparation and Precautions
Being a delicate organ, the eye requires extreme care before, during and after a surgical procedure. An ophthalmologist must diagnose a cataract and conduct or appropriately supervise the conduction of the operation. University programs typically allow patients to specify if they want to be operated upon by the consultant or the resident or fellow.
Proper anesthesia is a must for ocular surgery. Topical anesthesia is most commonly employed, typically by the instillation of a local anesthetic such as tetracaine or lidocaine. Alternatively, lidocaine and/or longer-acting bupivacaine anesthestic may be injected into the area surrounding (peribulbar block) or behind (retrobulbar block) the eye muscle cone to more fully immobilize the extraocular muscles and minimize pain sensation. A facial nerve block using lidocaine and bupivacaine may occasionally be performed to reduce lid squeezing.General anesthesia is recommended for children, traumatic eye injuries with cataract, for very apprehensive or uncooperative patients and animals. Cardiovascular monitoring is preferable in local anesthesia and is mandatory in the setting of general anesthesia. Proper sterile precautions are taken to prepare the area for surgery, including use of antiseptics like povidone-iodine. Sterile drapes, gowns and gloves are employed. A plastic sheet with a receptacle helps collect the fluids during phacoemulsification. An eye speculum is inserted to keep the eyelids open.
Surgical Technique
Before the phacoemulsification can be performed, one or more incisions are made in the eye to allow the introduction of surgical instruments. The surgeon then removes the anterior face of the capsule that contains the lens inside the eye. Phacoemulsification surgery involves the use of a machine with microprocessor-controlled fluid dynamics. These can be based on peristaltic or a venturi type of pump.
The phaco probe is an ultrasonic handpiece with a titanium or steel needle. The tip of the needle vibrates at ultrasonic frequency to sculpt and emulsify the cataract while the pump aspirates particles through the tip. In some techniques, a second fine steel instrument called a "chopper" is used from a side port to help with chopping the nucleus into smaller pieces. The cataract is usually broken into two or four pieces and each piece is emulsified and aspirated out with suction. The nucleus emulsification makes it easier to aspirate the particles. After removing all hard central lens nucleus with phacoemulsification, the softer outer lens cortex is removed with suction only.
An irrigation-aspiration probe or a bimanual system is used to aspirate out the remaining peripheral cortical matter, while leaving the posterior capsule intact. As with other cataract extraction procedures, an intraocular lens implant (IOL), is placed into the remaining lens capsule. For implanting a PMMA IOL, the incision has to be enlarged. For implanting a foldable IOL, the incision does not have to be enlarged. The foldable IOL, made of silicone or acrylic of appropriate power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL.
It is then inserted and placed in the posterior chamber in the capsular bag (in-the-bag implantation). Sometimes, a sulcus implantation may be required because of posterior capsular tears or because of zonulodialysis. Because a smaller incision is required, few or no stitches are needed and the patient's recovery time is usually shorter when using a foldable IOL.
DCR SURGERY
DCR or Dachryocystorhinostomy is a procedure that is performed to create a new tear drain when your current tear drain between the eye and the nose becomes blocked.
Anatomy
The tear drain start at two tiny openings called punctum that are located in inner aspect of both the upper and lower lids. Each of these is connected to the tear sac by very fine tubes called canaliculus. The tear sac is located in the inner corner of the eye next to the nose. A bony canal called the nasolacrimal duct drains the tears from this sac in to the nasal cavity.
Tear drainage
With every blink, the eyelids spread tears evenly across the eye to keep it moist and the remaining tears are then pumped in to the puncta and lacrimal sac. From the lacrimal sac the tears are drained in to the tear duct and the nose. If the tear duct is blocked , the tears spill over your eyelids on to you cheeks. Stagnant tears can result in an infection in the tear sac. External or endoscopic DCR can be performed to correct this problem.
Features of blocked tear duct
Excessive watering is the most common symptom but recurrent conjunctivitis or a painful swelling in the inner aspect of the eyelid can also occur. A careful history and examination help exclude other causes of a watery eye (such as hay fever, allergy, blepharitis, etc)
Treatment options
When other causes of a water eye have been ruled out and the surgeon has confirmed a blocked tear duct, the most successful solution is dachryocystorhinostomy or DCR surgery. Depending on the precise area of obstruction and nasal anatomy the surgery can either be carried out inside the nose using an endoscope so there is no skin incision (Endonasal DCR) or a small skin incision may have to be made on the skin to carry out the surgery (External DCR). A new tear drain is created to by-pass the obstruction and open directly in to the nose. A fine silicone stent is temporarily inserted in to the new tear drain (for 8 to 12 weeks) to keep it open during the healing process.
DCR surgery can be performed under general anaesthesia but can also be performed under local anaesthesia with sedation. Most patients go home the same day after the surgery and are advised to use antibiotic drops and ointment for a week after surgery.
Risks and complications
Some patients experience minor bleeding from the nose for the first day or 2 after surgery. Minor bruising and swelling can be expected on the side of the nose (external DCR) that settles within a week or two. The small skin scar for patients undergoing external DCR usually fades within six months. Scar tissue may occasionally block the drain, which may require additional surgery to clear.
Significant bleeding and infection are potential risks but are uncommon.
Anatomy
The tear drain start at two tiny openings called punctum that are located in inner aspect of both the upper and lower lids. Each of these is connected to the tear sac by very fine tubes called canaliculus. The tear sac is located in the inner corner of the eye next to the nose. A bony canal called the nasolacrimal duct drains the tears from this sac in to the nasal cavity.
Tear drainage
With every blink, the eyelids spread tears evenly across the eye to keep it moist and the remaining tears are then pumped in to the puncta and lacrimal sac. From the lacrimal sac the tears are drained in to the tear duct and the nose. If the tear duct is blocked , the tears spill over your eyelids on to you cheeks. Stagnant tears can result in an infection in the tear sac. External or endoscopic DCR can be performed to correct this problem.
Features of blocked tear duct
Excessive watering is the most common symptom but recurrent conjunctivitis or a painful swelling in the inner aspect of the eyelid can also occur. A careful history and examination help exclude other causes of a watery eye (such as hay fever, allergy, blepharitis, etc)
Treatment options
When other causes of a water eye have been ruled out and the surgeon has confirmed a blocked tear duct, the most successful solution is dachryocystorhinostomy or DCR surgery. Depending on the precise area of obstruction and nasal anatomy the surgery can either be carried out inside the nose using an endoscope so there is no skin incision (Endonasal DCR) or a small skin incision may have to be made on the skin to carry out the surgery (External DCR). A new tear drain is created to by-pass the obstruction and open directly in to the nose. A fine silicone stent is temporarily inserted in to the new tear drain (for 8 to 12 weeks) to keep it open during the healing process.
DCR surgery can be performed under general anaesthesia but can also be performed under local anaesthesia with sedation. Most patients go home the same day after the surgery and are advised to use antibiotic drops and ointment for a week after surgery.
Risks and complications
Some patients experience minor bleeding from the nose for the first day or 2 after surgery. Minor bruising and swelling can be expected on the side of the nose (external DCR) that settles within a week or two. The small skin scar for patients undergoing external DCR usually fades within six months. Scar tissue may occasionally block the drain, which may require additional surgery to clear.
Significant bleeding and infection are potential risks but are uncommon.
SQUINT SURGERY
Squint Surgery
The adjustment of the muscles of the eye to correctly align the eyes is the most common eye operation performed in children.
Eyes can be straightened virtually at any age- from as early as 4-5 months and whenever necessary in adulthood. A squint operation may take from 15-40 minutes.
The procedure is relatively straightforward and the results are good but not perfect. In most patients there is an 80-90% chance of the eyes being correctly aligned postoperatively. This means more than one operation will sometimes be required. The phases of the operation are-
The adjustment of the muscles of the eye to correctly align the eyes is the most common eye operation performed in children.
Eyes can be straightened virtually at any age- from as early as 4-5 months and whenever necessary in adulthood. A squint operation may take from 15-40 minutes.
The procedure is relatively straightforward and the results are good but not perfect. In most patients there is an 80-90% chance of the eyes being correctly aligned postoperatively. This means more than one operation will sometimes be required. The phases of the operation are-
- Preoperative Assessment It is extremely important to accurately measure the angle of deviation preoperatively. This is performed using prisms to neutralise the turn. It is also necessary to know preoperatively whether there is any paralysis or restriction of function of the eye muscles as this can affect the outcome and limit chance of correction.
- Anaesthetic In children a General Anaesthetic is employed.
- Operation a.The loose lining (skin) of the eye is opened to allow the anterior end of the eye muscles to be viewed.
- Post-operative Care When fully awake the patient is allowed to go home. Eye-drops are normally prescribed. Some medication is also prescribed to minimise pain and discomfort. Severe pain is rare following these operations but the eye will be sore for 24hours and remain red for several days. Nausea and vomiting occasionally occurs but is minimised with appropriate pre-operative medication.
- Review
Adults can in certain circumstances have the procedure performed under Local Anaesthetic. This makes it possible to optimise alignment in the course of the procedure.
If this is not possible, in older children or cooperative adults an "adjustable suture" technique can be combined with a General Anaesthetic so that alignment can be optimised postoperatively.
b.The eye muscles are approached, with the eye in place, at the anterior end. The muscle may be tightened by removing a small segment (resection) and reattaching it to the eye or conversely loosened by reattaching the muscle further posteriorly on the globe (recession). Other procedures may be utilised to vary the muscle's effect on movement- (eg transposing the muscle to affect rotation).
b.The eye muscles are approached, with the eye in place, at the anterior end. The muscle may be tightened by removing a small segment (resection) and reattaching it to the eye or conversely loosened by reattaching the muscle further posteriorly on the globe (recession). Other procedures may be utilised to vary the muscle's effect on movement- (eg transposing the muscle to affect rotation).
c. The lining is reapplied and sutured into place.
PTERYGIUM SURGERY
Pterygium (Surfer's Eye) most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is usually present in the palpebral fissure. It is associated with, and thought to be caused by ultraviolet-light exposure (e.g., sunlight), low humidity, and dust. The predominance of pterygia on the nasal side is possibly a result of the sun's rays passing laterally through the cornea, where it undergoes refraction and becomes focused on the limbic area. Sunlight passes unobstructed from the lateral side of the eye, focusing on the medial limbus after passing through the cornea. On the contralateral (medial) side, however, the shadow of the nose medially reduces the intensity of sunlight focused on thelateral/temporal limbus.
Pterygium in the conjunctiva is characterized by elastotic degeneration of collagen (actinic elastosis) and fibrovascular proliferation. It has an advancing portion called the head of the pterygium, which is connected to the main body of the pterygium by the neck. Sometimes a line of iron deposition can be seen adjacent to the head of the pterygium called Stocker's line. The location of the line can give an indication of the pattern of growth.
The exact cause is unknown, but it is associated with excessive exposure to wind, sunlight, or sand. Therefore, it is more likely to occur in populations that inhabit the areas near the equator, as well as windy locations. In addition, pterygia are twice as likely to occur in men than women.
Some research also suggests a genetic predisposition due to an expression of vimentin, which indicates cellular migration by the keratoblasts embryological development, which are the cells that give rise to the layers of the cornea. These cells also exhibit an increased P53 expression likely due to a deficit in the tumor suppressor gene. These indications give the impression of a migrating limbus because the cellular origin of the pterygium is actually initiated by the limbal epithelium.
The pterygium is composed of several segments:
Today a variety of options are available for the management of pterygium, from irradiation, to conjunctival auto-grafting or amniotic membrane transplantation, along with glue and suture application. As it is a benign growth, pterygium typically does not require surgery unless it grows to such an extent that it covers the pupil, obstructing vision or presents with acute symptoms. Some of the irritating symptoms can be addressed with artificial tears. However, no reliable medical treatment exists to reduce or even prevent pterygium progression. Definitive treatment is achieved only by surgical removal. Long-term follow up is required as pterygium may recur even after complete surgical correction.
If there is recurrence after surgery or if recurrence of pterygium is thought to be vision threatening, it is possible to use strontium (90Sr) plaque therapy. 90Sr is a radioactive substance that produces beta particles, which penetrate a very short distance into the cornea at the site of the operation. It suppresses the regrowth of blood vessels that occur with return of the pterygium. The treatment requires some local anaesthetic in the eye and is best done at the time of, or on the same day as the pterygium excision.
The 90Sr plaque is a concave metal disc about 1-1.5 cm in diameter that is hollow and filled with an insoluble strontium salt. The side placed on the eye is a very thin and delicate silver film that will contain the strontium but allow the beta particles to escape. The dose of radiation to the conjunctiva is controlled by the time that the plaque is left in contact with the surface. The integrity of the plaque surfaces is paramount to prevent exposure to patients and so is wipe tested to see if radioactive matter is escaping. Obviously this test must be done very very gently.
Conjunctival auto-grafting is a surgical technique that is effective and safe procedure for pterygium removal. When the pterygium is removed, the tissue that covers the sclera known as the conjunctiva is also extracted. Auto-grafting replaces the bare sclera with tissue that is surgically removed from the inside of the patients’ upper eyelid. That “self-tissue” is then transplanted to the bare sclera and is fixated using sutures, tissue adhesive, or glue adhesive.
Amniotic membrane transplantation is an effective and safe procedure for pterygium removal. Amniotic membrane transplantation offers practical alternative to conjunctival auto graft transplantation for extensive pterygium removal. Amniotic membrane transplantation is tissue that is acquired from the innermost layer of the human placenta and has been used to replace and heal damaged mucosal surfaces including successful reconstruction of the ocular surface. It has been used as a surgical material since the 1940s, and has been shown to have a strong anti-adhesive effect. Using an amniotic graft facilitates epithelialization, and has anti-inflammatory as well as surface rejuvenation properties. Amniotic membrane transplantation can also be fixated to the sclera using sutures, or glue adhesive. Amniotic membrane transplantation with Tisseel glue application and Mitomycin-C has shown excellent cosmetic outcomes with a surface free of redness, stitching, or patches, which makes the ocular surface suitable for vision correction surgery sooner.
Pterygium in the conjunctiva is characterized by elastotic degeneration of collagen (actinic elastosis) and fibrovascular proliferation. It has an advancing portion called the head of the pterygium, which is connected to the main body of the pterygium by the neck. Sometimes a line of iron deposition can be seen adjacent to the head of the pterygium called Stocker's line. The location of the line can give an indication of the pattern of growth.
The exact cause is unknown, but it is associated with excessive exposure to wind, sunlight, or sand. Therefore, it is more likely to occur in populations that inhabit the areas near the equator, as well as windy locations. In addition, pterygia are twice as likely to occur in men than women.
Some research also suggests a genetic predisposition due to an expression of vimentin, which indicates cellular migration by the keratoblasts embryological development, which are the cells that give rise to the layers of the cornea. These cells also exhibit an increased P53 expression likely due to a deficit in the tumor suppressor gene. These indications give the impression of a migrating limbus because the cellular origin of the pterygium is actually initiated by the limbal epithelium.
The pterygium is composed of several segments:
- Fuchs' Patches (minute gray blemishes that disperse near the pterygium head)
- Stocker's Line (a brownish line composed of iron deposits)
- Hood (fibrous nonvascular portion of the pterygium)
- Head (apex of the pterygium, typically raised and highly vascular)
- Body (fleshy elevated portion congested with tortuous vessels)
- Superior Edge (upper edge of the triangular or wing-shaped portion of the pterygium)
- Inferior Edge (lower edge of the triangular or wing-shaped portion of the ptyerygium).
Today a variety of options are available for the management of pterygium, from irradiation, to conjunctival auto-grafting or amniotic membrane transplantation, along with glue and suture application. As it is a benign growth, pterygium typically does not require surgery unless it grows to such an extent that it covers the pupil, obstructing vision or presents with acute symptoms. Some of the irritating symptoms can be addressed with artificial tears. However, no reliable medical treatment exists to reduce or even prevent pterygium progression. Definitive treatment is achieved only by surgical removal. Long-term follow up is required as pterygium may recur even after complete surgical correction.
If there is recurrence after surgery or if recurrence of pterygium is thought to be vision threatening, it is possible to use strontium (90Sr) plaque therapy. 90Sr is a radioactive substance that produces beta particles, which penetrate a very short distance into the cornea at the site of the operation. It suppresses the regrowth of blood vessels that occur with return of the pterygium. The treatment requires some local anaesthetic in the eye and is best done at the time of, or on the same day as the pterygium excision.
The 90Sr plaque is a concave metal disc about 1-1.5 cm in diameter that is hollow and filled with an insoluble strontium salt. The side placed on the eye is a very thin and delicate silver film that will contain the strontium but allow the beta particles to escape. The dose of radiation to the conjunctiva is controlled by the time that the plaque is left in contact with the surface. The integrity of the plaque surfaces is paramount to prevent exposure to patients and so is wipe tested to see if radioactive matter is escaping. Obviously this test must be done very very gently.
Conjunctival auto-grafting is a surgical technique that is effective and safe procedure for pterygium removal. When the pterygium is removed, the tissue that covers the sclera known as the conjunctiva is also extracted. Auto-grafting replaces the bare sclera with tissue that is surgically removed from the inside of the patients’ upper eyelid. That “self-tissue” is then transplanted to the bare sclera and is fixated using sutures, tissue adhesive, or glue adhesive.
Amniotic membrane transplantation is an effective and safe procedure for pterygium removal. Amniotic membrane transplantation offers practical alternative to conjunctival auto graft transplantation for extensive pterygium removal. Amniotic membrane transplantation is tissue that is acquired from the innermost layer of the human placenta and has been used to replace and heal damaged mucosal surfaces including successful reconstruction of the ocular surface. It has been used as a surgical material since the 1940s, and has been shown to have a strong anti-adhesive effect. Using an amniotic graft facilitates epithelialization, and has anti-inflammatory as well as surface rejuvenation properties. Amniotic membrane transplantation can also be fixated to the sclera using sutures, or glue adhesive. Amniotic membrane transplantation with Tisseel glue application and Mitomycin-C has shown excellent cosmetic outcomes with a surface free of redness, stitching, or patches, which makes the ocular surface suitable for vision correction surgery sooner.
GLAUCOMA SURGERY
Glaucoma is a group of diseases affecting the optic nerve that results in vision loss and is frequently characterized by raised intraocular pressure (IOP). There are many glaucoma surgeries, and variations or combinations of those surgeries, that facilitate the escape of excess aqueous humor from the eye to lower intraocular pressure, and a few that lower IOP by decreasing the production of aqueous.
Laser trabeculoplastyA 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 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 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 Argon Laser Trabeculoplasty. However, because SLT is performed using a much lower power laser, it does not appear to affect 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 wear off, although this has not been proven in clinical studies. ALT is repeatable to some extent with measurable results possible.
IridotomyAn iridotomy involves making puncture-like openings through the iris without the removal of iris tissue. Performed either with standard surgical instruments or 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.
IridectomyAn 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; 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.
Filtering procedures: penetrating vs. non-penetratingFiltering 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 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 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).
Non-penetrating filtering surgeries do not penetrate or enter the eye's anterior chamber. There are two types of non-penetrating surgeris: Bleb-forming and viscocanalostomy. Bleb forming procedures include ab externo trabeculectomy and deep sclerectomy. Ab externo trabeculectomy (AET) involves cutting from outside 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 is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing subconjunctival filtration without actually entering the anterior chamber; it is commonly performed with the Aquaflow collagen wick. Viscocanalostomy 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).
Other surgical proceduresGoniotomy and trabeculotomy are similar simple and directed techniques of microsurgical dissection with mechanical disruption of the trabecular meshwork. Gonotomy 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 suffering from congenital glaucoma, the cornea is not clear enough to visualize 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 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 with. 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 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 the treatment of glaucoma.
CanaloplastyCanaloplasty 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 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. Long-term results are available, published in May 2009 in the Journal of Cataract and Refractive Surgery.
Laser trabeculoplastyA 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 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 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 Argon Laser Trabeculoplasty. However, because SLT is performed using a much lower power laser, it does not appear to affect 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 wear off, although this has not been proven in clinical studies. ALT is repeatable to some extent with measurable results possible.
IridotomyAn iridotomy involves making puncture-like openings through the iris without the removal of iris tissue. Performed either with standard surgical instruments or 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.
IridectomyAn 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; 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.
Filtering procedures: penetrating vs. non-penetratingFiltering 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 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 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).
Non-penetrating filtering surgeries do not penetrate or enter the eye's anterior chamber. There are two types of non-penetrating surgeris: Bleb-forming and viscocanalostomy. Bleb forming procedures include ab externo trabeculectomy and deep sclerectomy. Ab externo trabeculectomy (AET) involves cutting from outside 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 is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing subconjunctival filtration without actually entering the anterior chamber; it is commonly performed with the Aquaflow collagen wick. Viscocanalostomy 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).
Other surgical proceduresGoniotomy and trabeculotomy are similar simple and directed techniques of microsurgical dissection with mechanical disruption of the trabecular meshwork. Gonotomy 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 suffering from congenital glaucoma, the cornea is not clear enough to visualize 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 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 with. 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 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 the treatment of glaucoma.
CanaloplastyCanaloplasty 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 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. Long-term results are available, published in May 2009 in the Journal of Cataract and Refractive Surgery.
