| Scleral reinforcement surgery | |
|---|---|
 Schematic diagram of the human eye. (Sclera labeled on left.) | |
| Specialty | ophthalmology |
Scleral reinforcement is a surgical procedure used to reduce or stop further macular damage caused by high myopia, which can be degenerative.
Myopia is one of the leading causes of blindness in the world. [1] [2] It is caused by both genetic [3] and environmental factors, [4] such as mechanical stretching, excessive eye work and accommodation, as well as an elevated intraocular pressure. It affects both children and adults. In many cases, myopia will stabilize once the growth process has been completed, but in more severe chronic cases, loss of vision can occur.
Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies. In this, distances vary for individuals from the far point—the maximum distance from the eye for which a clear image of an object can be seen, to the near point—the minimum distance for a clear image.
Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmHg).
Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by posterior sclera elongation and thinning (at least 25.5 mm to 26.5 mm) and high refractive errors of at least -5 to -7.5 diopters with an increase per year. [1] There may also be changes in the fundus, including posterior staphyloma, caused by the eye growing posteriorly and losing its spherical shape. [2] Since enlargement of the eye does not progress at a uniform rate, abnormal protrusions of uveal tissue may occur through weak points in the eye. Staphyloma is marked by a thinning of sclera collagen bundles and decreased number of collagen striations. It correlates with a large posterior temporal bulge. Curtin described five varieties, based on size, shape, and change in appearance of the optic nerve and retinal vessels, but the posterior pole type is the most common. [5] As the posterior staphyloma enlarges, choroidal tissue becomes thin and Bruch's membrane begins to break, creating lesions called lacquer cracks. Neovascularization may occur, causing blood vessels to protrude through the cracks and leak in the space underneath the photoreceptor cell layer. This hemorrhaging can lead to scarring and macular degeneration, causing vision to gradually deteriorate. [2] If left untreated, high myopia can cause retinal detachment, glaucoma, and a higher risk of cataracts.
The sclera, also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some elastic fiber. In humans, the whole sclera is white, contrasting with the coloured iris, but in other mammals the visible part of the sclera matches the colour of the iris, so the white part does not normally show. In the development of the embryo, the sclera is derived from the neural crest. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, fatty deposits on the sclera can make it appear slightly yellow. Many people with dark skin have naturally darkened sclerae, the result of melanin pigmentation.
The fundus of the eye is the interior surface of the eye opposite the lens and includes the retina, optic disc, macula, fovea, and posterior pole. The fundus can be examined by ophthalmoscopy and/or fundus photography. The term fundus may also be inclusive of Bruch's membrane and the choroid.
A staphyloma is an abnormal protrusion of the uveal tissue through a weak point in the eyeball. The protrusion is generally black in colour, due to the inner layers of the eye. It occurs due to weakening of outer layer of eye by an inflammatory or degenerative condition. It may be of 5 types, depending on the location on the eyeball.
The condition of posterior staphyloma in high myopia was first described by Scarpa in the 1800s. [6] Speculation about reinforcement of the eye began in the 19th century, when Rubin noted that sclera reinforcement “is probably the only one of all the surgical techniques [for myopia] which attempts to correct a cause, rather than an effect”. [7] Procedures in early literature aimed at shortening the length of the eyeball by resecting a ring of sclera from the equator of the eye. [2] Later procedures focused on modifying the axial length of the eye, by preventing elongation and staphyloma progression by placing grafts over the posterior part of the eye. In 1930, Shevelev proposed the idea of transplantation of fascia lata for sclera reinforcement. [8] Curtin promoted the use of donor-sclera grafting for reinforcement. [9] In 1976, Momose first introduced Lyodura, a material derived from processed cadaver dura mater. [10] At this point, many different surgeons made alterations to existing techniques. Snyder and Thompson modified reinforcement techniques and had positive outcomes, [11] while others, like Curtin and Whitmore, expressed dissatisfaction with their negative conclusions. [12]
The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by intermuscular septa. The fascia lata is thickened at its lateral side where it forms the iliotibial tract, a structure that runs to the tibia and serves as a site of muscle attachment.
Lyodura was a medical product used in neurosurgery that has been shown to transmit Creutzfeldt–Jakob disease, a degenerative neurological disorder that is incurable, from affected donor cadavers to surgical recipients. Lyodura was introduced in 1969 as a product of B. Braun Melsungen AG, a leading hospital supply company based in Germany.
The surgery aims to cover the thinning posterior pole with a supportive material to withstand intraocular pressure and prevent further progression of the posterior staphyloma. The strain is reduced, although damage from the pathological process cannot be reversed. By stopping the progression of the disease, vision may be maintained or improved.
There are three basic techniques, referred to as X-shaped, Y-shaped, and single strip support. [10] In X-shaped and Y-shaped, the arms run the risk of the being pulled medially, which would press on the optic nerve and could result in optic nerve atrophy. In single strip support, the material covers the posterior pole vertically between the optic nerve and insertion of the inferior oblique muscle. Often, this method is preferred, since it is the easiest method for placement, provides the widest area of support, and reduces the risk of optic nerve interference. [2]
The optic nerve, also known as cranial nerve II, or simply as CN II, is a paired nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
Many different materials have been used in the past, including fascia lata, [8] Lyodura (lyophilized human dura), [10] Gore-Tex, [2] Zenoderm (porcine skin dermis), [13] animal tendons, and donor's or cadaver’s sclera. [9] [14] [15] Human sclera is thought to offer the best support, as well as Lyodura, which is biologically compatible with the eyeball and has sufficient tensile strength. Artificial materials, such as nylon or silicone, are not suggested. [10] Sclera from cadaver’s or animal tendons run the risk of being rejected.
While there have been many modifications, Thompson’s procedure has often been used as a basis. [16] First, the conjunctiva and Tenon's capsule are incised about 6 mm from the corneal limbus. The lateral, superior, and inferior recti muscles are separated using a strabismus hook. The connecting tissue is then separated from the posterior pole, as well as the inferior oblique muscle. The strip of material is passed under the separated muscles, and pushed down deeply towards the posterior pole. Both ends of the material strip are crossed over the medial rectus muscle and sutured to the sclera on the medial side of the superior and inferior recti muscles. The conjunctiva and Tenon's capsule are then closed together.
Long-term complication rates are usually low, but short-term complications may include chemosis, choroidal edema or hemorrhage, damage to the vortex vein, and transient motility problems. [16]
Scleral reinforcement surgery is not presently popular in the United States, and there has been a scarcity of published clinical studies. Donor sclera material is also difficult to acquire and store, and artificial materials are still being tested. This procedure is much more popular in other countries, such as the former Soviet Union and Japan. [2] There is also controversy regarding in what developmental stage this procedure should be performed. [2] Some feel efforts should be made as soon as possible to arrest progression in children. Others feel that the procedure should only be done in cases where high myopia is indicated with macular changes. Furthermore, different surgeons have particular criteria that must be met by patients in order to receive surgery.
Glaucoma is a group of eye diseases which result in damage to the optic nerve and vision loss. The most common type is open-angle glaucoma with less common types including closed-angle glaucoma and normal-tension glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Peripheral vision may begin to decrease followed by central vision resulting in blindness if not treated. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, blurred vision, mid-dilated pupil, redness of the eye, and nausea. Vision loss from glaucoma, once it has occurred, is permanent.
Near-sightedness, also known as short-sightedness and myopia, is an eye disorder where light focuses in front of, instead of on, the retina. This causes distant objects to be blurry while close objects appear normal. Other symptoms may include headaches and eye strain. Severe near-sightedness increases the risk of retinal detachment, cataracts, and glaucoma.
Vitrectomy is surgery to remove some or all of the vitreous humor from the eye.
Eye surgery, also known as ocular surgery, is surgery performed on the eye or its adnexa, typically by an ophthalmologist. The eye is a very fragile organ, and requires extreme care before, during, and after a surgical procedure to minimise or prevent further damage. An expert eye surgeon is responsible for selecting the appropriate surgical procedure for the patient, and for taking the necessary safety precautions. Mentions of eye surgery can be found in several ancient texts dating back as early as 1800 BC, with cataract treatment starting in the fifth century BC. Today it continues to be a widely practiced type of surgery, having developed various techniques for treating eye problems.
Refractive eye surgery is an eye surgery used to improve the refractive state of the eye and decrease or eliminate dependency on glasses or contact lenses. This can include various methods of surgical remodeling of the cornea (keratomileusis), lens implantation or lens replacement. The most common methods today use excimer lasers to reshape the curvature of the cornea. Successful refractive eye surgery can reduce or cure common vision disorders such as myopia, hyperopia and astigmatism, as well as degenerative disorders like keratoconus.
Phacoemulsification is a 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 to maintain the anterior chamber.
The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit which abducts, depresses and internally rotates the eye. It is the only extraocular muscle innervated by the trochlear nerve.
This is a partial list of publishes a classification of known diseases and injuries, the International Statistical Classification of Diseases and Related Health Problems, or ICD-10. This list uses that classification.
ICD-10 is an international statistical classification used in health care and related industries.
Trabeculectomy is a surgical procedure used in the treatment of glaucoma to relieve intraocular pressure by removing part of the eye's trabecular meshwork and adjacent structures. It is the most common glaucoma surgery performed and allows drainage of aqueous humor from within the eye to underneath the conjunctiva where it is absorbed. This outpatient procedure was most commonly performed under monitored anesthesia care using a retrobulbar block or peribulbar block or a combination of topical and subtenon anesthesia. Due to the higher risks associated with bulbar blocks, topical analgesia with mild sedation is becoming more common. Rarely general anesthesia will be used, in patients with an inability to cooperate during surgery.
The fascia bulbi is a thin membrane which envelops the eyeball from the optic nerve to the limbus, separating it from the orbital fat and forming a socket in which it moves.
Hypertropia is a condition of misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye. Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye. Dissociated Vertical Deviation is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive.
An ocular prosthesis, artificial eye or glass eye is a type of craniofacial prosthesis that replaces an absent natural eye following an enucleation, evisceration, or orbital exenteration. The prosthesis fits over an orbital implant and under the eyelids. Though often referred to as a glass eye, the ocular prosthesis roughly takes the shape of a convex shell and is made of medical grade plastic acrylic. A few ocular prostheses today are made of cryolite glass. A variant of the ocular prosthesis is a very thin hard shell known as a scleral shell which can be worn over a damaged or eviscerated eye. Makers of ocular prosthetics are known as ocularists. An ocular prosthesis does not provide vision; this would be a visual prosthesis. Someone with an ocular prosthesis is totally blind on the affected side and has monocular vision.
Optic pit, optic nerve pit, or optic disc pit is a congenital excavation of the optic disc, resulting from a malformation during development of the eye. Optic pits are important because they are associated with posterior vitreous detachments (PVD) and even serous retinal detachments.
The nerve fibers forming the optic nerve exit the eye posteriorly through a hole in the sclera that is occupied by a mesh-like structure called the lamina cribrosa. It is formed by a multilayered network of collagen fibers that insert into the scleral canal wall. The nerve fibers that comprise the optic nerve run through pores formed by these collagen beams. In humans, a central retinal artery is located slightly off-center in nasal direction.
Ocular surgery may be performed under topical, local or general anesthesia. Local anaesthesia is more preferred because it is economical, easy to perform and the risk involved is less. Local anaesthesia has a rapid onset of action and provides a dilated pupil with low intraocular pressure.
Glued IOL or Glued Intraocular lens is a new Surgical technique for implantation of a posterior chamber IOL with the use of biological glue in eyes with deficient or absent posterior capsules. A quick-acting surgical fibrin sealant derived from human blood plasma, with both hemostatic and adhesive properties is used.
IOL Scaffold or Intraocular lens Scaffold technique is a surgical procedure in Ophthalmology. In cases where the lens bag is ruptured and the cataract of the eye is not yet removed one can inject an artificial lens or Intraocular lens (IOL) inside the eye under the cataract. This way the IOL acts as a scaffold and prevents the cataract pieces from falling inside the eye. One can then remove the cataract pieces safely by emulsifying it with ultrasound. This technique is called IOL Scaffold and was started by Dr. Amar Agarwal from Chennai, India at Dr. Agarwal's Eye Hospital.