DR. KUMAR J DOCTOR Title: Intra Operative Online Pachymetry in LASIK with Wavefront-Guided Ablation Optical Coherence Pachymetry with the ESIRIS DOCTOR EYE INSTITUTE ANDHERI MUMBAI drkumardr@vsnl.com NO FINANCIAL INTEREST

Purpose: To investigate Intraoperative Optical Coherence Pachymetry during various steps of LASIK while treating patient with Wavefront Guided Ablation

OCP-signal from Michelson Interferometer Online OCP Optical Coherence Pachymeter ESIRIS SCHWIND LASER mirror s(t) light source beam splitter eye detector OCP-signal from Michelson Interferometer

The direct integration of Online Pachymetry into the ESIRIS It comes with fiberglass coupling and through Automated measurements of changes in corneal thickness, allows continuous and real time values with 10 measurements per second, without having to interrupt the treatment. The reproducibility of current System is 1 to 2 microns.

Method 25 patients IN Aug. 09 Myopic Eyes Corneal Thickness Assessed During Various Steps CP Microkeratome 110 micron head – 50 eyes One Blade Used Per Eye Wave Front Guided Treatments done

Wavefront-Guided Ablation Every 3 micron distortion on the Cornea creates 1 micron of Wavefront Error “Corneal Wavefront is the component of eye refraction owed to the Cornea (or OPTICAL PATH DIFFERENCE OPD) Aberrations: “Ocular” = “Corneal” + “Internal”(or “Total”) From WA From TC (100%) (80%)

Results Mean Spherical Equivalent - 4.0 D,+/-3.0 D Mean Stromal Depth 80+/-22 microns Mean Flap Thickness of 110, +/- 9 microns Residual Stromal 300 microns & above in all eyes. All optical zones 6.00 mm

Table 2 Central corneal thickness measurements in Table 1 Central corneal thickness measurements in eyes PRE-OP laser in situ keratomileusis Devices Mean SD [M Range [M On Line Pachy 502.8 431-599 Table 2 Central corneal thickness measurements in eyes POST-OP laser in situ keratomileusis Devices Mean SD [M Range [M On Line Pachy 438 463-512

Advantages of Online Pachymetry. The greatest advantage of Online Pachymetry is indeed the improved quality assurance, objective monitoring of the complete LASIK procedure for the first time. The special feature of Online Pachy provides Extensive Diagnosis – Each step of the surgery can be checked during operation Contact Free measurement of Corneal Thickness online, hence no chances of infection Also the individual ablation depth and possible dehydration effects of the cornea were monitored continuously Improvement in Intraoperative Safety and Quality of LASIK

Conclusion Evaluation of residual corneal thickness is crucial to avoid the condition of excessive corneal thinning (ectasia) Important safety feature to monitor the thickness of each cut Assessment of flap and residual stromal thickness. Accurate Measurement of ablation depth during laser treatment. TO CHECK A WELL OPPOSED INTERFACE AFTER WASH