Long-term changes in corneal structure and tear inflammatory mediators after orthokeratology and LASIK.

PURPOSE: To monitor changes in corneal structure and level of inflammatory mediators in tears of myopic patients following orthokeratology (OK) and laser in situ keratomileusis (LASIK). METHODS: Sixty-two myopic subjects were analyzed in this prospective study. Thirty-two had worn Paragon CRT contact lenses and 30 underwent standard LASIK. Thirty-two control subjects were also recruited. Pachometry and corneal topography were performed 12 months after both interventions. Tears were collected and assayed using ELISA for IL-6, IL-8, matrix metalloproteinase-9 (MMP-9), and epidermal growth factor (EGF). RESULTS: Corneal power decreased in the central area and increased in the paracentral area. Simultaneously, there was a central corneal thinning with mid-peripheral thickening for OK. No changes were observed for LASIK. In comparison with controls, IL-6, IL-8, MMP-9, and EGF levels were increased significantly for OK (P < 0.01). Only MMP-9 (P < 0.01) and EGF (P < 0.01) were increased for LASIK. Pro-inflammatory response was found to be associated with the degree of myopia in the OK group. The MMP-9 and EGF upregulation was linked to the presence of iron deposition in both groups, whereas increased levels of EGF were connected with the presence of myopic regression after LASIK. CONCLUSIONS: Both interventions involved important tissue reshaping. The physical presence of a reverse geometry contact lens caused certain markers to change significantly in comparison with no lens wear or LASIK in the long-term response. MMP-9 was significantly higher in tears of subjects presenting iron deposition after OK or LASIK, and EGF levels seemed to play an important role in postoperative refractive outcomes after LASIK.

Central corneal thickness measured with three optical devices and ultrasound pachometry.

PURPOSE: To evaluate the reliability of three noninvasive pachometry methods against the ultrasound pachometer considered the gold standard. METHODS: Central corneal thickness (CCT) was measured using a Paxis ultrasound (US) pachometer, Orbscan II, Pentacam, and Topcon SP-3000 specular microscope in 22 right eyes of 22 healthy adults (7 men, 15 women). Three repeated measures were obtained and then compared to obtain the repeatability of each instrument and the agreement between pachometers. RESULTS: Pentacam is the optical system that renders values of CCT closer to those obtained with US pachometry. Conversely, a specular microscope shows a poorer agreement with US measures, and differences depend on the thickness being measured. The Orbscan system shows a consistent trend toward underestimation of CCT compared with US and Pentacam irrespective of the value measured. CONCLUSION: Different optical methods used to measure CCT showed significantly different results compared with US pachometry except for the Pentacam system. Clinicians should take into account the fact that specular microscopy might either underestimate or overestimate values of CCT, whereas Orbscan systematically overestimates CCT compared with US and Pentacam.