Flap creation is a critical step in laser in situ keratomileusis (LASIK). Efforts to improve the safety and predictability of the lamellar incision have fostered the development of femtosecond lasers. Several advantages of the femtosecond laser over mechanical microkeratomes have been reported in LASIK surgery. In this article, we review common considerations in management and complications of this step in femtosecond laser-LASIK and concentrate primarily on the IntraLase laser because most published studies relate to this instrument.
The cornea is the major refractive element in the eye; even minor surface distortions can produce a significant reduction in visual acuity. Standard clinical methods used to evaluate corneal shape include keratometry, which assumes the cornea is ellipsoidal in shape, and photokeratoscopy, which images a series of concentric light rings on the corneal surface. These methods fail to document many of the corneal distortions that can degrade visual acuity. Algorithms have been developed to reconstruct the three dimensional shape of the cornea from keratoscope images, and to present these data in the clinically useful display of color-coded contour maps of corneal surface power. This approach has been implemented on a new generation video keratoscope system (Computed Anatomy, Inc.) with rapid automatic digitization of the image rings by a rule-based approach. The system has found clinical use in the early diagnosis of corneal shape anomalies such as keratoconus and contact lens-induced corneal warpage, in the evaluation of cataract and corneal transplant procedures, and in the assessment of corneal refractive surgical procedures. Currently, ray tracing techniques are being used to correlate corneal surface topography with potential visual acuity in an effort to more fully understand the tolerances of corneal shape consistent with good vision and to help determine the site of dysfunction in the visually impaired.
In a randomized, double-blind clinical trial conducted at 13 medical centers, meropenem (1,000 mg given iv every 8 hours) was compared with the combination of clindamycin (900 mg every 8 hours) plus tobramycin (5 mg/[kg · d] in three divided doses) given iv for the treatment of intra-abdominal infections that required surgery and parenteral antibiotic therapy. At the end of treatment, efficacy data on patients who met study inclusion criteria (intent-to-treat) were available for 132 of 215 patients in the meropenem group and 134 of 212 patients in the clindamycin/tobramycin group; 120 (91%) of 132 intent-to-treat patients in the meropenem group were cured, 115 (86%) of 134 intent-to-treat patients in the clindamycin/tobramycin group were cured (P value, not significant). Of the patients treated with meropenem and considered evaluable according to the study protocol, 89 (92%) of 97 were cured, and 81 (86%) of 94 patients treated with clindamycin/tobramycin and considered evaluable were cured. Bacteriologic response rates for all evaluable patients (n = 191) were 96% (93 of 97 patients) among those randomized to the meropenem arm and 93% (87 of 94) among those randomized to the clindamycin/tobramycin arm. Adverse events occurred with similar frequency in both treatment groups; neither seizures nor deaths related to treatment were reported for any patients in either group. The results of this trial demonstrated that meropenem, together with appropriate surgical intervention, was safe and effective in the treatment of patients who had bacterial intra-abdominal infections, most of which were secondary to complicated appendicitis.
ABSTRACT BACKGROUND: Anterior stromal keratocyte cells undergo programmed cell death (apoptosis) in response to corneal epithelial injury. Keratocyte apoptosis may be an initiator of the corneal wound healing response that includes keratocyte proliferation and activation, as well as changes to the overlying epithelium, occurring following refractive surgical procedures such as photorefractive keratectomy (PRK). This study compares the effect of laser-scrape and transepithelial PRK on keratocyte apoptosis. METHODS: Photorefractive keratectomy was performed in both eyes of 10 New Zealand white rabbits using the Summit Apex excimer laser. Surgery was performed using transepithelial PRK in one eye and laser-scrape PRK in the other. The central cornea was analyzed at 4 hours after surgery using a quantitative TUNEL assay that detects fragmented DNA characteristic of apoptosis. Hepatocyte growth factor (HGF) production by keratocytes was detected by immunocytochemistry. RESULTS: Average apoptotic cells per 400X microscopic field determined by 2 independent masked observers were 0.9 ± 0.5 (scanning electron microscopy) and 0.2 ± 0.2 in the transepithelial PRK group compared with 5.1 ± 2.9 and 4.1 ± 3.2 in the laser-scrape group. The difference between the two groups was statistically significant for both observers (P < .05, ANOVA). HGF was detected within keratocytes throughout the corneal stroma. Less HGF was detected in the anterior stroma in the laser-scrape group at 4 hours after surgery, consistent with more anterior keratocyte apoptosis in this group. CONCLUSIONS: Transepithelial PRK induced less anterior keratocyte apoptosis in rabbbits than laser-scrape PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and subepithelial scarring. [J Refract Surg 1998;14:526-533]
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)