Pachymetry and immunohistochemistry of LASIK flap created by different femtosecond lasers in eye-bank corneas

Abstract

 

Purpose

 

The aim of this study was to compare the corneal cell viability and thickness of the LASIK flap created by three femtosecond lasers in eye-bank human corneas.

 

Methods

 

Forty five eye-bank human cornealscleral buttons (15 corneas in each group) were examined after the creation of 120 mm thickness laser assisted keratomileusis (LASIK) flaps with the150kHz iFS IntraLase™ (IL), the Z6 Femto LDV™ (LDV) or the 200kHz Wavelight™ FS200 (FS200). The anterior segment optical coherence tomography (ASOCT - Visante™) was used to measure the thickness of the flaps vertically and horizontally at +0.5 mm; +1.0 mm; +2.0 mm and +3.0 mm, and at -0.5 mm; -1.0 mm; -2.0 mm and -3.0 mm from the corneal vertex, and at +0.5 mm and -0.5 mm from the flap edge. Cellular viability was blinded evaluated with immunohistochemistry for keratocyte apoptosis using anti-caspase 3 antibdy. Statistical analyzes were performed with Prism 5 software (GraphPad Software Inc., San Diego, CA, USA) and was considered a significance level set at p <0.05. Kruskal-Wallis test with Dunn's post-test was used to evaluate statistical difference in the thickness of the flaps and keratocyte apoptosis.

 

Results

 

There was a statistically significant difference in the corneas treated by LDV and IL between the flap thickness horizontally and vertically at +0.5 mm, +1.0 mm, +2.0 mm, +3.00 mm, -0.5 mm, -1.00 mm, showed in table 1. There was a statistically significant difference in the stromal keratocyte apoptosis in corneas treated by LDV, FS200 and IL, showed in table 1. Figure 1 shows corneal stromal keratocyte apoptosis.

 

Conclusions

 

In this study, the flaps created with the IL were more predictable than those with the LDV, but all the 3 groups showed a low deviation from the intended flap thickness as described in the literature. Keratocyte apoptosis was higher in corneas treated with the LDV followed by those treated with the FS200 and with the IL. Femtosecond laser technology has the advantage of producing LASIK flap with good thickness predictability. Different keratocyte apoptosis occurs with different femtosecond lasers equipments.

 

 

Table 1. Comparison of LASIK flap thickness and keratocyte apoptosis between groups

 

 

Figure 1. Corneal stromal keratocytes apoptosis in the retroablation zone of LASIK. Immunofluorescence in 40x.

 

Keywords: 683 refractive surgery: LASIK • 578 laser • 426 apoptosis/cell death