C-TEN is sometimes referred to as Advanced Surface Ablation (ASA)

Corneal incision procedures
Radial keratotomy (RK), developed by Russian ophthalmologist Svyatoslav Fyodorov in 1974, uses spoke-shaped incisions, always made with a diamond knife, to alter the shape of the cornea and reduce myopia or astigmatism; this technique is, in medium to high diopters, usually replaced by other refractive methods. Arcuate keratotomy (AK), also known as Astigmatic keratotomy, uses curvilinear incisions at the periphery of the cornea to correct high levels of non-pathological astigmatism, up to 13 diopters. AK is often used for the correction of high post-keratoplasty astigmatism or post-cataract surgery astigmatism. Limbal relaxing incisions (LRI) are incisions near the outer edge of the iris, used to correct minor astigmatism (typically less than 2 diopters). This is often performed in conjunction with an Intraocular Lens implantation. Other procedures
Radial Keratocoagulation, also known as Radial Thermokeratoplasty, was invented in 1985 by Svyatoslav Fyodorov and is used to correct hyperopia by putting a ring of 8 or 16 small burns surrounding the pupil, and steepen the cornea with a ring of collagen constriction. It can also be used to treat selected types of astigmatism. It is now generally replaced by laser thermal keratoplasty/laser thermokeratoplasty. Laser thermal keratoplasty (LTK) is a non-touch thermal keratoplasty performed with a Holmium laser, while conductive keratoplasty (CK) is thermal keratoplasty performed with a high-frequency electric probe. Thermal keratoplasty can also be used to improve presbyopia or reading vision after age 40.
Classification
Sarcoidosis may be divided into the following types:

Treatment
Treatments for sarcoidosis vary greatly depending on the patient. At least half of patients require no systemic therapy. Most people (>75%) only require symptomatic treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin. For those presenting with lung symptoms, unless the respiratory impairment is devastating, active pulmonary sarcoidosis is observed usually without therapy for two to three months; if the inflammation does not subside spontaneously, therapy is instituted.Major categories of drug interventions include glucocorticoids, antimetabolites, biologic agents especially monoclonal anti-tumor necrosis factor antibodies. Investigational treatments include specific antibiotic combinations and mesenchymal stem cells. If drug intervention is indicated, a step-wise approach is often used to explore alternatives in order of increasing side effects and to monitor potentially toxic effects.Corticosteroids, most commonly prednisone or prednisolone, have been the standard treatment for many years. In some people, this treatment can slow or reverse the course of the disease, but other people do not respond to steroid therapy. The use of corticosteroids in mild disease is controversial because in many cases the disease remits spontaneously. Antimetabolites
Antimetabolites, also categorized as steroid-sparing agents, such as azathioprine, methotrexate, mycophenolic acid, and leflunomide are often used as alternatives to corticosteroids. Of these, methotrexate is most widely used and studied. Methotrexate is considered a first-line treatment in neurosarcoidosis, often in conjunction with corticosteroids. Long-term treatment with methotrexate is associated with liver damage in about 10% of people and hence may be a significant concern in people with liver involvement and requires regular liver function test monitoring.