John Hill

　　Hill Vision Institute

　　Goal:Eye positioning，alignment and treatment centration are among the most important factors in laser refractive surgery，yet grossly under discussed.Procedures such as LASIK often subject the cornea to severe interference by the generation and disposition of the corneal flap，worsening the integrity of the alignment of the cornea under surgery.This paper presents a technology called IWEAR that allows for proper positioning and alignment such that the treatment center is preserved。

　　Method:Eye positioning and alignment is most accurate and convenient when the eye is intact and without the corneal flap lifted in the case of LASIK procedure.An undisturbed pre-surgical reference matrix is acquired and used as a reference and alignment framework–called registration.The acquisition of the registration matrix is assisted by computerized imaging and image processing，but mainly by the skills of the surgical staff.During surgery，after the corneal flap is lifted in the case of LASIK，the patient eye is positioned to align to the reference image with multi-dimensional reference features，duplicating the pre-surgical alignment of the cornea.A high-speed eye tracker is then engaged to track the motion of the eye during the surgery。

　　Results:This in-situ whole eye alignment technique is facilitated by the use of computerized imaging and image processing technology.It is intuitive，accurate and convenient to use.It eliminates or minimizes the alignment error，and allows the surgeon to monitor the alignment during ablation process while a high-speed eye tracker tracks the motion of the eye for active and precise ablation，thus eliminating ablation error caused by the alignment error。

　　Conclusions:Alignment error is more rampant than recognized;and ironically，it is more so in the age of high-speed eye tracking technology.Without proper alignment aid，even the best eye tracking system can cause decentered ablation and/or other irregular ablation.This paper presents a technology that allows for in-situ whole eye alignment and registration，enabling proper alignment with minimal interference and multi-dimensional registration for accurate alignment and registration.