The flap is lifted like a hinged door, but in contrast to ALK, the targeted tissue is removed from the corneal stroma with an excimer laser. The flap is subsequently replaced. When the flap is created using an IntraLase brand femtosecond laser, the method is called IntraLASIK; other femtosecond lasers such as the Ziemer create a flap similarly. Femtosecond lasers have numerous advantages over mechanical microkeratome based procedure. Microkeratome related flap complications like incomplete flaps, buttonholes or epithelial erosion are eliminated with femtosecond laser procedure. Absence of microscopic metal fragments from the blade will reduce the risk of lamellar keratitis also.Customized aspheric treatment zone (CATz) is a topography-guided LASIK treatment developed by NIDEK Co. Ltd which ablates the cornea based on patient-specific geometry to address certain disadvantages in conventional wavefront spherocylindrical ablation. The treatment is effective for myopia with astigmatism or otherwise irregular corneas, and reduces symptoms such as glare, halos, and night driving difficulty. Refractive Lenticule Extraction (ReLEx):
ReLEx "FLEx" (Femtosecond Lenticule Extraction): A femtosecond laser cuts a lenticule within the corneal stroma. Afterwards, a LASIK-like flap is cut which can be lifted to access the lenticule. This is removed through manual dissection using a blunt spatula and forceps. ReLEx "SMILE" (Small Incision Lenticule Extraction): A newer technique without a flap, a femtosecond laser cuts a lenticule within the corneal stroma. The same laser is used to cut a small incision along the periphery of the lenticlue about 1/5th the size of a standard LASIK flap incision.
Biotin deficiency is a nutritional disorder which can become serious, even fatal, if allowed to progress untreated. It can occur in people of any age, ancestry, or of either gender. Biotin is part of the B vitamin family. Biotin deficiency rarely occurs among healthy people because the daily requirement of biotin is low, many foods provide adequate amounts of it, intestinal bacteria synthesize small amounts of it, and the body effectively scavenges and recycles it in the kidneys during production of urine. However, deficiencies can be caused by consuming raw egg whites over a period of weeks to months. Egg whites contain high levels of avidin, a protein that binds biotin strongly. When cooked, avidin is partially denatured and binding to biotin is reduced. However one study showed that 30-40% of the avidin activity was still present in the white after frying or boiling. Genetic disorders such as biotinidase deficiency, multiple carboxylase deficiency, and holocarboxylase synthetase deficiency can also lead to inborn or late-onset forms of biotin deficiency. In all cases – dietary, genetic, or otherwise – supplementation with biotin is the primary method of treatment. Signs and symptoms
Rashes including red, patchy ones near the mouth (erythematous periorofacial macular rash)
Fine and brittle hair

Psychological
Hallucinations
Lethargy
Mild depression, which may progress to profound fatigue and, eventually, to somnolence
Generalized muscular pains (myalgia)
Paresthesias

Causes
Total parenteral nutrition without biotin supplementation: Several cases of biotin deficiency in patients receiving prolonged total parenteral nutrition (TPN) therapy without added biotin have been reported.