Asser AE Abdel-Meguid

AIM: To compare intraocular pressure (IOP) measurements before and after laser keratomileusis (LASIK) with a femtosecond laser for flap creation using ocular response analyzer (ORA) and Goldmann applanation tonometry, and to identify factors that may influence the preoperative and postoperative IOP.

METHODS: A prospective study conducted on myopic patients who underwent LASIK using a femtosecond laser for flap fashioning. Enrolled patients were evaluated preoperatively, 6wk and 3mo postoperatively for manifest refraction (MR), keratometric (K) readings and central corneal thickness (CCT) using a scheimpflug-based topography. Corneal resistance factor (CRF), corneal hysteresis (CH), Goldmann correlated IOP (IOPg) and corneal compensated IOP (IOPcc) were measured using ORA besides IOP assessment by Goldman applanation tonometry (GAT).

RESULTS: There was a statistically significant decrease in measures of IOPg by 3.35±0.83 mm Hg, followed by GAT which decreased by 2.2±0.44 mm Hg, and the least affected by operation was IOPcc which decreased only by 0.87±0.1 mm Hg after 6wk. After 3mo follow up there was a statistically significant decrease in IOPcc which decreased only by 0.76±0.4 mm Hg, followed by IOP GAT by 1.6±0.5 mm Hg, and the most affected by operation was IOPg which decreased by 2.3±0.3 mm Hg. Correspondingly, there was a statistically significant decrease in CH and CRF after 6wk and 3mo. At 3mo, the preoperative MR and preoperative GAT were prominent significant predictors of the postoperative GAT changes. The prediction equation was subsumed.

CONCLUSION: IOP measurements and corneal biomechanical factors reduce significantly after LASIK with a femtosecond laser for flap creation. The IOPcc values are less influenced by changes in corneal properties than IOPg and GAT, indicating that IOPcc may provide the most reliable measurement of IOP after this procedure.

To compare equal concentrations (0.5%) of moxifloxacin and gatifloxacin ophthalmic solutions with regard to conjunctival bacterial reduction as well as anterior chamber penetration. One hundred patients were divided into 2 groups. Group A received moxifloxacin 0.5% ophthalmic solution and group B received gatifloxacin 0.5% ophthalmic solution 4 times a day for 3 days before surgery and 5 times with 30 min intervals on the day of surgery. Two conjunctival swabs were obtained: one before instillation of antibiotic and the second 30 min after instillation of the last antibiotic drop. Specimens were sent for culture and susceptibility testing. At the time of surgery, 0.1 mL of aqueous fluid was aspired, and aqueous concentration of fluoroquinolones was identified using reverse-phase high-pressure liquid chromatography assay technique. The most common flora isolated was coagulase-negative (32.9%), followed by (24.8%) and (19.1%). Moxifloxacin aqueous concentration was higher compared with gatifloxacin [1.75 ± 0.98 standard deviation (SD) and 0.75 ± 0.22 SD, respectively]. This 2.3-fold difference in aqueous humor antibiotic concentrations was statistically significant ( ≤ 0.001). There was significant difference between the means of conjunctival colony-forming unit after antibiotic administration in both the study groups (2.17 ± 1.54 SD in group A and 1.56 ± 1.09 SD in group B). Moxifloxacin 0.5% was found to penetrate anterior chamber more than gatifloxacin 0.5%, enforcing its use for prophylaxis before intraocular surgeries. However, gatifloxacin 0.5% eye drops were able to reduce conjunctival bacterial load, more supporting its use before extraocular and refractive surgeries.