Ophthalmology 2012 Pf. 김현승 / R4 신정아

Introduction Femtosecond lasers have been used successfully in ophthalmic surgery since 2001. The technology has been applied as a surgical tool in corneal incisions, wedge resections, tunnel creations, and penetrating and anterior lamellar keratoplasty. The benefits of femtosecond cataract surgery include reduced ultrasound power used during phacoemulsification and high precision of capsulorrhexis with fewer collateral tissue effect better intraocular lens centration. However, introduction of any new procedure into clinical practice involves a learning curve. The numbers reported are small and there is little published information about intraoperative complications, the surgical learning curve, and visual outcomes.

Purpose To describe the intraoperative complications and to evaluate the learning curve with femtosecond laser cataract surgery.

Patients and Methods Prospective, multicenter, nonrandomized study : 200 consecutive femtosecond laser cataract surgeries : between April 2011 and June 2011. : cataract surgeries performed at the Vision Eye Institute : 7 surgeons(M.L., G.S., T.V.R., Colin C., David N., Simon C., Mark J.) Exclusion criteria for femtosecond cataract surgery Presence of glaucoma, pseudoexfoliation, corneal opacity, poorly dilating pupils (7 mm), previous corneal surgery, blood or any other material in the anterior chamber, lens or zonular instability, hypotony Preoperative ocular biometry : axial length and biometry (IOL Master version 5), pachymetry, corneal topography and lens densitometry (Allegro Oculyzer), specular microscopy and OCT for macular thickness.

Patients and Methods Preoperative and postoperative evaluation : slit-lamp biomicroscopy, tonometry, manifest refraction, measurement of uncorrected and corrected distance visual acuity, Evaluation during surgery : performance of laser anterior capsulotomy, corneal incisions, lens phacofragmentation, : incidence of complications -Pupillary dilation was achieved before surgery with : 1% tropicamide, 10% phenylephrine, 1% cyclopentolate -Under topical anesthesia, Surgery was performed -Postoperative Regimen : 0.3% ciprofloxacin, ketorolac tromethamine, 0.1% dexamethasone ophthalmic suspension 4 times/day for 2 weeks -followed up at day 1, day 14, and 6 weeks after surgery

Procedure LenSx laser system(Alcon LenSx Lasers Inc., Aliso Viejo, CA) was used to perform all the femtosecond cataract procedures. -The initial steps for the procedure involve programming the lens, capsulotomy, primary incision, and secondary incision patterns. -After all pattern selections and parameter choices are complete, the system is ready to dock to the patient. -The delivery system is lowered until the patient interface makes contact with the patient’s eye. -Sensors in the delivery system detect the objective’s position and applanation force, which is indicated on the delivery system touch screen. -The surgeon observes applanation of the cornea using the video microscope and then applies suction when the cornea is properly applanated.

Procedure LenSx laser system(Alcon LenSx Lasers Inc., Aliso Viejo, CA) -The control point settings now include limbal centration, marking the corneal incision boundaries, pupil centration, and identification of the depth and position of the lens. -Using the OCT image, a selection is made with respect to capsulotomy peak and trough, lens offsets, corneal thickness, and wound tunnel length. -The laser treatment then is started by pressing the foot switch and the surgical progress is monitored on the video screen -The program delivers laser energy in a sequence of capsule, lens, and primary and secondary corneal incisions. -After the completion of the laser procedure, the patients were shifted to the operating room.

Procedure in OR After the completion of the laser procedure, the patients were shifted to the operating room. After careful sterile surgical preparation -laser-created corneal incisions were dissected bluntly with spatula -laser-created anterior capsulotomy flap was removed with forceps -lens segmentation was completed according to surgeon’s preference either with an Akahoshi chopper or by using a chop technique -Surgery then was completed with a standard phacoemulsification using the Infiniti Vision System. -After the removal of the lens cortex, an intraocular lens(IOL) was implanted in the capsular bag.

Results The initial 200 consecutive eyes were included in the study. The mean age of the patients was 69.2 ± 9.8 years. Of the 200 eyes, the laser procedure was completed successfully with respect to capsulotomy, lens fragmentation, and primary corneal and secondary corneal incisions in 153 eyes. Thus, the completion rate was 76.5%. In 9 eyes, the laser procedure included capsulotomy and lens segmentation without the corneal incisions because the incision capabilities were disabled(n=4) or could not be completed(n=5). 38 eyes electively underwent capsulotomy and corneal incision only with the femtosecond laser.

The mean number of docking attempts per eye was 1.5 The average number of attempts progressively decreased as the surgeons’ experience increased. (p=0.001)

5 eyes were seen to have a break in suction during the procedure 5 eyes were seen to have a break in suction during the procedure. In all case, no further femtosecond ablation was attempted and surgery had been completed successfully with a manual approach In all these cases, the treatment was stopped instantly by releasing the foot switch, and this led to no adverse events.

Of 191 eyes in which the corneal incisions were created using the femtosecond laser, 26 (13.6%) required a keratome either for primary or secondary incisions for entry into the anterior chamber. : This was attributed either to the site of placement of corneal incisions or to the angle of entry into the anterior chamber. A decreasing trend was noted with successive surgeries. however, the difference was not statistically significant.

After the patients were shifted to the operating room, the pupil was noted to decrease in 19 eyes (9.5%). Most of these incidents occurred in the initial set of cases. A change in the control point settings subsequently led to a significant decrease in these numbers. (p=0.001)

All capsulotomies were ranked according to ease of removal. Of the 200 eyes, 35 (17.5%) underwent free-floating capsulotomies requiring no manual detachment. The number of free-floating capsulotomies was noted to increase significantly as the study progressed. (p=0.001) All capsulotomies were ranked according to ease of removal. : score of 1 indicating great difficulty and 10 indicating a free-floating capsule All patients were ranked 8 or higher of 10, indicating relative ease.

After the laser-created anterior capsulotomy flap was removed, 21 (10 After the laser-created anterior capsulotomy flap was removed, 21 (10.5%) demonstrated the presence of anterior capsular tags In 8 eyes (4%), the geometry of the capsular tags led to extension and formation of radial anterior capsular tears. These tears extended to the posterior capsule in 4 eyes, with 3 eyes requiring anterior vitrectomy. Posterior capsular rupture was noted in 3 eyes additionally. (3.5%) 4 eyes were noted to have posterior dislocation of the nucleus or nuclear fragments. (2%)

Postoperative complications In 84.5% eyes, the corrected visual acuity was 20/30 or better at 2 weeks of follow-up. The difference in mean postoperative IOP at day 1 was +5.3 ± 7.3 mmHg and +3.8 ± 6.2 mmHg at 2 weeks after surgery. 4 eyes had mild corneal edema that resolved by 1 week after surgery In 1 case, cystoid macular edema developed that resolved with topical nonsteroidal anti-inflammatory agents. It was noted that surgeons who were well versed with the use of femtosecond laser had statistically fewer complications in the first 100 cases, with no significant difference in complications observed after the initial 100 cases

Adjustment of the capsule pattern secondary incision Capsulotomy lens primary incision Adjustment of the anterior capsule depth and posterior capsule depth

Although femtosecond lasers increase the ease and predictability of the steps involved in cataract surgery, there is a definite learning curve involved in carrying out this procedure. The initial intraoperative complication rate was unacceptably high but settled rapidly with experience. Experience with the use of a femtosecond laser also may help to flatten the learning curve.

Image-Guided Femtosecond Laser Cataract Surgery System The femtosecond laser and OCT beam share the same optical path, providing an exact co-registration of the OCT image with the laser segmentation patterns Femtosecond lasers - photodisruption - cause optical breakdown of the tissues - generating plasma - shock wave - cavitation - gas bubble formation Palanker DV et al. Femtosecond Laser–Assisted Cataract Surgery with Integrated Optical Coherence Tomography. Science Translational Medicine, 2010, 17, 1-9.

Limitations of Traditional Cataract Surgery Key Step Current Surgery Impact Safety Impact Corneal Incision Not Optimized Induced Cylinder Infection Capsulorhexis Variable Sized, Not Centered Variable IOL Position & Effective Lens Power Capsular Tears, Posterior Capsule Opacification Lens Fragmentation Excessive Ultrasound Power Delayed Visual Recovery Loss of Endothelial Cells, Capsule Rupture

Femtosecond Laser Cataract Surgery IOL Position Predictability Uniform Shape and Size Capsulotomy Corneal Astigmatism Reproducible Corneal Entry and Arcuate Incisions Early Wow Factor Reduced Phaco Power and Corneal Edema Devgan U, Current Opinions in Ophthalmology 2011;18:19–22. Norrby SJ, J Cataract Refract Surg 2008;34:368–376 Hill WJ, J Cataract Refract Surg 2008;34:364–367

Of the 200 eyes, 74.5% underwent a complete procedure of laser capsulotomy, lens fragmentation, and corneal incisions

Suction Breaks Anterior Radial Tear 5 eyes (2.5%) 0.06% and 0.27% during IntraLase (AMO) appearance of a meniscus, redundant conjunctiva halted immediately by releasing the foot switch Anterior Radial Tear 8 eyes (4%) 3.8% by Ng et al. and 4.7%–5.3% by Unal et al. (JSCRS 1998, JSCRS 2006) Anterior capsular tags in approximately 10% These notches are identified and guided manually with forceps to maintain the curvilinearity of the capsulotomy opening to prevent equatorial and posterior extension of these tears.

Posterior Capsule Tear & Lens Dislocation Posterior capsule tear 7 eyes (3.5%) Posterior dislocation of the nucleus or fragments 4 eyes (2%) 0.53%~1.9% during traditional phacoeumlsification Causes Posterior extension of anterior radial tear (Half of cases) manually checking the capsulotomy for completion stabilization of the eye by injection of viscoelastics through the side port before opening the main incision Tear in the posterior capsule during cortical removal (3 cases) Energy produced by the femtosecond laser has some effect on the cortical fibers and the posterior capsule Intraoperative capsular block (2 cases) Entrapped gases within the crystalline lens during photodisruption Subsequent hydrodissection further increases the pressure The heating and increased adherence of the cortex to the capsular edge

Although femtosecond lasers increase the ease and predictability of the steps involved in cataract surgery, there is a definite learning curve involved in carrying out this procedure. The initial intraoperative complication rate was unacceptably high but settled rapidly with experience. Experience with the use of a femtosecond laser also may help to flatten the learning curve.