It involves cutting a flap in the cornea and pulling it back to expose the corneal bed, then using an excimer laser to ablate the exposed surface to the desired shape, and then replacing the flap. The name LASIK was coined in 1991 by University of Crete and the Vardinoyannion Eye. The patents related to so-called broad-beam LASIK and PRK technologies were granted to US companies including Visx and Summit during 1990–1995 based on the fundamental US patent issued to IBM (1983) which claimed the use of UV laser for the ablation of organic tissues. In 1991, J.T. Lin, Ph.D. (a Chinese Physicist) was granted a US patent for a new technology using a flying-spot for customized LASIK currently used worldwide. The first US patent using an eye-tracking device to prevent decentration in LASIK procedures was granted to another Chinese Physicist, Dr. S. Lai in 1993. Techniques
Flap procedures
Excimer laser ablation is done under a partial-thickness lamellar corneal flap. Automated lamellar keratoplasty (ALK): The surgeon uses an instrument called a microkeratome to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced. Laser-assisted in situ Keratomileusis (LASIK): The surgeon uses either a microkeratome or a femtosecond laser to cut a flap of the corneal tissue (usually with a thickness of 100–180 micrometres).
Genetics
Neu-Laxova syndrome is a heterogeneous metabolic disorder caused by homozygous or compound heterozygous mutations in one of three genes: PHGDH, PSAT1 and PSPH These genes are involved in the serine biosynthesis pathway and are essential for cell proliferation. Mutations in all three genes had been previously identified as the cause of serine-deficiency syndromes. Although there is some clinical overlap between NLS and these neurometabolic disorders, the phenotype in other serine-deficiency disorders is milder. Diagnosis
The diagnosis is usually based on clinical features present at birth. Ultrasound in the second trimester may show abnormalities associates with NLS, including polyhydramnios, intrauterine growth restriction, microcephaly, proptosis and decreased fetal motility. Treatment
Serine and glycine supplementation has shown tentative benefits in those with related serine biosynthesis defects and milder forms of NLS. Prognosis
The prognosis is poor; affected individuals are either stillborn or die shortly after birth. The longest survival reported in literature is of 134 days. This syndrome is transmitted as an autosomal recessive disorder and there is a risk for recurrence of 25% in future pregnancies. References


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