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An analysis to optimize the various aspects of micro incision phacoemulsification surgery on different grade of cataracts and the micro incision IOL implantation
Session Title: Phaco Techniques
Session Date/Time: Saturday 05/10/2013 | 08:30-10:30
Paper Time: 09:28
Venue: Main Lecture Hall (Ground Floor)
First Author: : A.Galli Lakshmi Narayanan INDIA
Co Author(s): : U. Srinivasan P. Sankara Adhi S. Subbaiah
To optimize the microincision phacoemulsification surgery and microincision intraocular lens implantation through1.8mm and 2.2mm incisions. Measurement and analysis performed on the active and passive wound size to study the corneal stretch factor. The immediate post-operative wound closure is studied with the optical coherence tomogram analysing the incisional integrity, Surgically Induced Astigmatism using corneal topography and post-operative cell density with the specular microscopy are also compared bilaterally for each patient in this study. The anterior chamber fluidics properties were also compared in both microincision categories using a Computational Fluid Dynamics(CFD) Analysis. Anterior chamber pressure contour mapping is also performed for a comparitive analysis.
Group I of 15 patients and Group II of 15 patients were considered for analysing the 1.8mm and 2.2mm Microcoaxial Phacoemulsification Surgery. The calibrated microblades measuring 1.8/2mm or 2.2/2.4mm were used to create an incision size optimum enough to suit the micro phaco and I/A probe tips. Trapezoidal blades of 1.8 mm and 2.2mm allow equilibrated fluid flow with minimal friction of the probe tip during the various steps of surgery. The outcome of active and passive wound size during the each step of micro co-axial phacoemulsification surgery is documented and the passive incision size measured followed on by microincision IOL implantation in a partially wound assisted manner in the left eyes and in the right eyes the cartridge tip is partially inserted within the micro incision after a prior extension of 2.0mm or 2.4mm respectively. Caliberated measuring gauges have been devised to exactly determine the size of the incision during each step of the surgical procedure and also the final incision size after implantation. Computational Fluid Dynamics Study analysis was compared for both microincisions of 1.8mm and 2.2mm with appropriate phaco tip sleeve dimensions along with inflow and outflow data as input parameters for this simulation.
Patients with bilaterally similar grade of cataract were chosen. Both eyes subjected to Micro Phacoemulsification Surgery. In this study, the left eye(OS) phacoemulsified under 1.8mm or 2.2mm incision size based on cataract grade and then microcartridge is introduced without extension of incision. For the same patient the other right eye(OD) cataract is phacoemulsified with similar microincisions of 1.8mm or 2.0mm but for IOL implantation the incision is extended to 2mm or 2.4mm in order to protect the wound integrity. Active and passive wound sizes were measured and analysed. Inspite of creating a corneal tunnel of more than 1.5mm the left eyes were stromally hydrated whereas the right eyes did not require any stromal hydration after the IOL implantation through the extended incision. Group I were implanted with Hydrophilic IOL and Group II were implanted with Hydrophobic IOL. A 3D model of a Human Eye Anterior Chamber was created for the fluidics study applied to a Computational Fluid Dynamics Software using the Reynolds Stress Equation for a turbulent model compared for the 1.8mm and 2.2mm incisions, by simulating a streamline flow pattern for randomly irrigated fluid particles and total surgical aspirated fluid turnover is fed as an input parameter.
All the left eyes of the patients in both the groups were observed for the incisional stretch factor which indicated passive incision size with the partially wound assisted implantation procedure stretching the incision by atleast 0.1mm on either side resulting the 1.8mm incision extending to 2mm and the 2.2mm extending to 2.4mm due to the cartridge tip maneuver. In case of the right eyes, there is minimal stress due to cartridge tip maneuver and incisional stretch factor observed was only 0.025mm on either side leading to an overall passive incision size of 2.05mm or 2.45mm only. OCT images indicate perfect wound closure within 24 hours for most of the right eyes as compared to the left eyes which had a distorted and partially closed wound during the short post-operative period. The Corneal Topography revealed the fact that the Surgically Induced Astigmatism for both eyes in both groups were less than -0.50D or observed even to be nil in few patients. Less surgical fluid turnover measured indicates minimal percentage of loss in endothelial cell density post-operatively. This also correlated with the CFD Study and revealed the fact that 1.8mm microco-axial phacoemulsification creates more anterior chamber pressure as compared to the 2.2mm.
Since most of the microcartridges deliver the IOL in wound assisted procedure, it is recommended to extend the micro phaco incision to appropriately suit the choice of the micro cartridge to be utilized in order to obtain the best wound integrity and also to optimize the passive wound size under surgeon’s control in order to facilitate a excellent wound closure within a very short post-operative period.
The Computational Fuid Dynamics revealed the fact that less aspirated particle flow in case of a 1.8mm phaco needle tip as compared to the 2.2mm phaco needle which leads to more positive pressure induced in the Simulated Anterior Chamber Model for a 1.8mm microco-axial phacoemulsification procedure. The pressure contour mapping also indicate a higher intraocular pressure induced in case of a 1.8mm incision as compared to a 2.2mm incision. It is observed that 2.2mm incision seems to be safer for the intraocular tissues as they are subjected to minimal trauma due to less positive pressure induced.
Considering this study for the optimization of the microincision phaco surgeries and post-operative results, we recommend an overall 0.2mm extension of the microphaco incisions in both the incision sizes - 1.8mm and 2.2mm for the implantation of any microincision IOL implantation post phacoemulsification. This leaves a hyper square corneal valve which provides a greater degree of incisional stability and better wound closure within a short post-operative period which in turn leading to patient safety in all aspects with an excellent visual outcome in the long run and a faster rehabilitation to normal life style.