A 32-year-old man suffering from keratoconus was treated with radial keratotomy. Twenty weeks later, he presented visual deterioration, edema and corneal perforation. A penetrating keratoplasty was required. The postoperative course was regular, but after 9 months, the patient presented kerato-uveitis. Subsequent phlogistic relapses occurred approximately every 6 months during the following 5 y...

Radial keratotomy is a refractive surgical technique, widely used in the 80s and early 90s to correct myopia and astigmatism, but now overcome by more recent laser techniques. Important consequences, often in patients with more than 45 years of age, are progressive hyperopic shift and/or an increase in corneal astigmatism, whose main cause seems to be an increase in the curvature radius of the ...

An optical vortex (phase singularity) with a high topological strength resides on the axis of a high-order light beam. The breakup of this vortex under elliptic perturbation into a straight row of unit-strength vortices is described. This behavior is studied in helical Ince-Gauss beams and astigmatic, generalized Hermite-Laguerre-Gauss beams, which are perturbations of Laguerre-Gauss beams. App...

The energy scaling up of pulse postcompression is still an open issue. In this work we analyze the use of astigmatic focusing to improve the output pulses in a filamentation based postcompression setup. Unlike spherical conditions, astigmatic focusing enhances the output energy and the spectral broadening of the filament. This is due to the increase of critical power, allowing a considerable im...

The article investigated conditions for shaping astigmatic-invariant structured Laguerre-Gaussian (LG) beams in the case of simple astigmatism. We have theoretically and experimentally confirmed that astigmatic invariance are q-phase parameter LG (sLG) beam is equal to arctangent ratio Rayleigh length z0 focal fcyl a cylindrical lens single amplitude epsilon;=1. For rest values, epsilon;NotEqua...

BACKGROUND The visual system adjusts to changes in the environment, as well as to changes within the observer, adapting continuously to maintain a match between visual coding and visual environment. We evaluated whether the perception of oriented blur is biased by the native astigmatism, and studied the time course of the after-effects following spectacle correction of astigmatism in habitually...

Three hundred consecutive cases of radial keratotomy performed between 1985 and 1990 were reviewed. There were no sight threatening complications of surgery and no patient lost one or more lines of corrected Snellen acuity. Overall 78.7% saw 6/12 or better unaided postoperatively and 51.7% saw 6/6 or better. Refraction showed 61.3% to be within 1 dioptre of emmetropia and 86.7% were within 2 di...

OBJECTIVE To compare postoperative astigmatic change and graft stability using 2 different donor button diameters in endothelial lamellar keratoplasty to treat corneal endothelial failure. METHODS A 200- micro m-thick corneal flap keratectomy was performed in human donor corneoscleral rims (n = 20; 10 donors and 10 recipients) using an artificial anterior chamber and a manual microkeratome (A...

PURPOSE We performed a prospective study of the changing profile of astigmatism in white school children in Northern Ireland. METHODS Of the 399 6- to 7-year-old and 669 12- to 13-year-old participants in Phase 1 of the Northern Ireland Childhood Errors of Refraction (NICER) study, 302 (76%) of the younger and 436 (65%) of the older cohort were re-examined three years later (Phase 2). Stratif...