Femtosecond Laser-assisted Penetrating Keratoplasty

Mohammad Zare MDProfessor of OphthalmologyLabbafinejad Medical Center

Shaheed beheshti Medical University

18-10-2012

One hundred years after the first successful penetrating keratoplasty (PK) by Zirm in 1905, corneal transplantation has become the most commonly performed transplant in the world.

The invention of femtosecond laser technology has allowed great advances in the field of penetrating keratoplasty (PKP).

Combining advanced LASIK technology with current transplantation concepts has taken cornea grafting to the next plane.

In penetrating keratoplasty, misalignment of the anterior surface of the donor and host, are major sources of optical distortion and limit visual outcomes due to:

1- Rotational misalignment, where the tissue is not precisely distributed, 2- excess and uneven suture tension, 3- postoperative slow and uneven wound healing,

Femtosecond laser (IntraLase) 1- Provides a safe and predictable means of

performing a customised cut in PK procedures, 2- Is a very sophisticated device that allows for

greater precision to match the exact shape of the removed and donated tissue segments.

3- Any cut configuration and angulation can be chosen,

4- The cut quality is excellent5- The prepared donor transplant nestles

perfectly in the recipient eye.

5- Other theoretical benefits include: greater biomechanical stability, better wound healing, reduction in induced astigmatism faster visual rehabilitation.

This is usually not the case when we perform traditional penetrating keratoplasty with a cylindrical trephine.

Evaluation and Surgery proper patient selection criteria should be met. Potential candidates should be suitable for full-thickness penetrating

keratoplasty. Relative contraindication

severe peripheral neovascularization and scarring in some cases. contraindication

Previous glaucoma filtering surgery in the form of an active bleb or aqueous drainage device

Patients with very narrow palpebral fissures should be carefully evaluated preoperatively to make sure that the suction ring can be fitted and suction maintained.

During preoperative evaluation specific attention is paid to corneal diameter, especially vertical, to determine the required graft diameter.

A preoperative pachymetry map is performed to adequately assess and program depth settings for the femtosecond laser incision.

Informed patient consent is mandatory.

• Donor corneas can be cut by the femtosecond laser with preprogrammed parameters set by the surgeon.

• This is done with the donor tissue mounted on an artificial anterior chamber or alternatively 'precut' with the same parameters by the eyebank.

There are numerous patterns that can be programmed for femtosecond laserassisted PKP.

• Figure 2 Various shapes used in laser assisted keratoplasty. Standard cut (A) Top hat (B) Mushroom (C) Zig-zag (D) Christmas tree (E)

'zig-zag' incision

Max: 9mm

0.50 mm320µm

70µ

Identical parameters are used for the donor cornea and the host incision.

a bridge of uncut corneal tissue is left

That side-cut bridges are stronger than lamellar bridges

Evaluation and Surgery

• Generally, for the laser cut, topical anesthesia is used.

• It is important to ensure proper centration of the patient interface to allow for centration of the graft.

•

• After the femtosecond laser incision is performed, the eye is treated with prophylactic antibiotic drops and

shielded. The patient is then transferred to the operating suite where

either retrobulbar or general anesthesia is administered. The host corneal button is separated by blunt dissection

with a Sinskey hook to reveal the incisions made by the laser.

In most cases the laser incisions separate cleanly. In areas of dense corneal scarring, limited sharp dissection

with a surgical blade or scissors may be required. After the 360-degree blunt dissection of the laser incision,

the anterior chamber is entered with a blade and the posterior cut is completed using corneal scissors.

The donor cornea is then sutured into place using whatever suturing style the surgeon prefers

• Top hat shaped corneal graft. IntraLase software used.

Table 1: Corneal top hat parameters of host and donor corneas.

Recipient cornea Donor cornea

Lamellar depth 300 microns 300 microns

Outer diameter 9.1 mm 9.3mm

Inner diameter 6.5 mm 7.6mm

Anterior side cut posterior depth

250 microns, diameter 7.5mm

330 microns, 7.7mm

Posterior side cut anterior depth

270 microns, diameter 9.0mm

270 microns, 9.2mm

Laser Assisted Keratoplasty: Key Points•When to consider laser assisted keratoplasty? •Any patient who requires a full-thickness corneal transplant

•Patients in whom a faster time to visual rehabilitation is desirable

•Consider the top hat shape for patients with underlying endothelial pathology, such as Fuchs

•Traditional PKP •Lengthy visual rehabilitation

•Potential wound leakage due to shape of traditional corneal button

•Increased suture tension in order to approximate donor and recipient wound edges

•High incidence of irregular astigmatism post-operatively

•Increased length of time to suture removal due to decreased wound surface area and increased healing time

•Decreased endothelial cell counts due to a lesser number of transplanted endothelial cells as compared with top hat PKP

Advantages of Laser Assisted Keratoplasty over traditional PK

•Increased wound surface area leads to faster healing and decreased time to suture removal•Decreased visual rehabilitation time•A variety of precise, complex corneal cuts and shapes can be made•Increased endothelial cell counts due to greater surface area of transplanted endothelium in top hat shape•Greater wound strength and watertight seal•Decreased wound dehiscence•Better fit of donor cornea as compared with manual dissection•Potential for decreased post-op astigmatism, however further studies must be conducted

Am J Ophthalmol. 2007 May;143(5):737-742. Epub 2007 Mar 19.

The use of the femtosecond laser in penetrating keratoplasty.Buratto L, Böhm E.SourceCentro Ambrosiano di Microchirurgia Oculare (C.A.M.O. S.p.A.), Milan, Italy. office@burratto.com

AbstractPURPOSE: To evaluate a new technique for penetrating keratoplasty (PK) with the use of a new software algorithm for a femtosecond

laser that is designed to create penetrating cuts for PK in the treatment of a number of corneal diseases. DESIGN: Prospective, interventional case series. METHODS: All eyes were treated at the Ospedale Civile di Mestre, Umberto, Italy. Seven eyes of seven patients underwent surgery for

PK using a 15-kHz femtosecond laser (IntraLase, Irvine, California, USA) and a new software specifically developed for corneal surgery. Of the seven patients, five were keratoconus patients and two had bullous keratopathy. New software was used to create penetrating cuts in a top hat or mushroom configuration. After surgery, all patients were evaluated with pachymetry, corneal topography, refraction, intraocular pressure measurement, and corneal optical coherence tomography (Visante; Carl Zeiss, Oberkochen, Germany).

RESULTS: On postoperative day one, all seven eyes had nearly clear corneas with a good graft of the donor corneas to the patients'

corneas. At three months, all eyes had clear corneas with good endothelial cell counts and quiet anterior chambers. Normal corneal thickness was achieved in each case. At the three-month visit, suture removal was performed in five eyes to adjust for astigmatism.

CONCLUSIONS: Although this is a small number of eyes, early indications are that the use of the new IntraLase software for corneal surgery creates a more favorable environment for PK as a result of a better fit of the donor cornea and a quicker visual recovery for patients

American Journal of Ophthalmology, Volume 145, Issue 5, May 2008, Pages 772–774.e2Original article

Outcomes of Femtosecond Laser–Assisted Penetrating KeratoplastyYong M. Pora, b, Jacob Y. Chuan Chenga, b, Anand Parthasarathya, b, Jodhbir S. Mehtaa, b, Donald T.H. Tana, b, c, ,

a Singapore National Eye Centre, Singaporeb Singapore Eye Research Institute, Singaporec Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.

PurposeTo evaluate outcomes from the use of a femtosecond laser to trephine both donor and recipient corneas during penetrating

keratoplasty (PK).

DesignProspective interventional case series.

MethodsPatients were recruited from the cornea clinic of the Singapore National Eye Centre. We used a 10-kHz Femtec (20/10 Perfect

Vision, Heidelberg, Germany) femtosecond laser to perform trephination of the donor cornea on an artificial anterior chamber, followed by trephination of the recipient cornea. Trephination cuts were straight and performed 90 degrees to the corneal surface. Tissue bridges were bluntly separated with a Barrett phaco chopper. The donor button was then sutured to the recipient with double continuous sutures, or interrupted sutures if significant host corneal vascularization was present. Postoperatively, visual acuity, refraction, intraocular pressures, and optical coherence tomography (Visante; Carl Zeiss, Jena, Germany) were evaluated.

ResultsEight eyes of eight patients underwent PK for conditions ranging from bullous keratopathy to corneal scarring from herpetic

stromal keratitis. Patients were followed up for a mean of 9.5 months. Best-corrected visual acuities of patients with no ocular comorbidity ranged from 20/20 to 20/80. Mean cylindrical refractive error at last review was 2.56 diopters [D] (range, 0.50 to 4.00 D). Tissue bridges were bluntly dissected except for one case that required scissors completion of trephination. No complications were encountered related to use of the Femtec laser.

ConclusionThe Femtec laser reliably trephines both donor and recipient corneas for PK, with good visual outcomes and relatively low

degrees of astigmatism.

Am J Ophthalmol. 2008 Jul;146(1):50-55. Epub 2008 Apr 24.

Short-term results of penetrating keratoplasty performed with the Femtec femtosecond laser.Hoffart L, Proust H, Matonti F, Ridings B, Conrath J.SourceDepartment of Ophthalmology, Hopital de la Timone, 264 rue Saint-Pierre, Marseille cedex 05, France. louis.hoffart@ap-hm.fr

AbstractPURPOSE: To evaluate the use of the Femtec femtosecond (fs) laser for penetrating keratoplasty (PK) in the treatment of corneal

diseases. DESIGN: Prospective, nonrandomized clinical study. METHODS: Nine eyes of nine patients underwent surgery for PK. Five had pseudophakic bullous keratopathy, three had Fuchs

dystrophy, and one presented in a keratoconus patient. A Femtec (20/10 PerfectVision; GmbH, Heidelberg, Germany) fs laser was used to create penetrating cuts on donor and recipient corneas. All patients were evaluated for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), pachymetry, topography, and endothelial cell density (ECD). Scanning electron microscopy (SEM) was performed on corneal tissue after surgery.

RESULTS: All eyes were treated successfully without intraoperative complications. The mean follow-up was 6 +/- 3 months. At the last

postoperative examination mean BSCVA was 20/69 and there was a significant improvement (P = .08) in both UCVA and BSCVA. Mean astigmatism was 2.9 +/- 1.2 diopters. Mean ECD was 1194 +/- 465 cells/mm(2) with a mean cell loss after surgery of 49.8% +/- 19.8%. SEM displayed smooth rectilinear cut margins and minor remaining tissue bridges. One patient presented a retinal detachment three months after surgery that was successfully treated and two subjects showed an allograft rejection.

CONCLUSION: Use of the Femtec fs laser was effective and safe to perform PK. Short-term visual results and refractive results are analogous to conventional PK or other fs laser-assisted PK studies. Longer-term follow-up of additional cases is necessary to precisely quantify the endothelial cell loss after fs surgery.

PMID:18439558[PubMed - indexed for MEDLINE

Br J Ophthalmol. 2009 Jan;93(1):73-8. Epub 2008 Oct 16.

Femtosecond laser versus manual dissection for top hat penetrating keratoplasty.

Bahar I, Kaiserman I, Lange AP, Levinger E, Sansanayudh W, Singal N, Slomovic AR, Rootman DS.SourceDepartment of Ophthalmology, Toronto Western Hospital, 399 Bathurst Street, Ontario, Canada.

iritbahar@yahoo.com

AbstractAIM: To compare the outcomes of IntraLase-enabled top hat penetrating keratoplasty (IEK) versus retrospective

results of manual top hat penetrating keratoplasty (TH-PKP) and conventional PKP. Patients/methods: This non-randomised prospective study included 94 eyes: 23 eyes underwent IEK, 36 TH-PKP and 35 conventional PKP. Preoperative and postoperative manifest refraction, uncorrected and best-spectacle corrected visual acuity (BSCVA), high-order ocular aberrations (HOA), endothelial cell counts and complications were analysed.

RESULTS: At 12 months of follow-up, the mean log MAR BSCVA was 0.32 (SD 0.31) in the IEK group, 0.53 (0.36) in

the TH PKP group (p = 0.03) and 0.39 (0.30) in the conventional PKP group (p = 0.4). The mean spherical equivalent was similar between the groups and was less than -2.2 dioptres. The mean cylinder was similar in the IEK and conventional PKP group (3.6 (1.9) dioptres and 4.1 (1.8) dioptres, respectively), and was significantly lower than the TH-PKP group (5.1 (3.2) dioptres, p = 0.04). The complications rate and high-order ocular aberrations were similar between the three groups studied. The mean endothelial cell loss was significantly lower at 12 months of follow-up in the IEK and the TH-PKP groups versus conventional PKP (32.4% and 22.3% vs 40.8%, respectively) (p = 0.05). The mean time to suture removal was 4.1 (1.2) months in the IEK group and 3.9 (1.5) months in the TH-PKP group versus 9.7 (1.1) months in the conventional PKP group (p<0.0001).

CONCLUSIONS: IEK is a safe and stable procedure. It results in higher endothelial counts and faster suture removal in comparison with the conventional PKP, and has less astigmatism and better BSCVA in comparison with the manual TH-PKP

Cornea. 2009 Aug;28(7):795-800.

Top-hat shaped corneal trephination for penetrating keratoplasty using the femtosecond laser: a histomorphological study.

Kook D, Derhartunian V, Bug R, Kohnen T.Source; Department of Ophthalmology, Johann Wolfgang Goethe University, 60590 Frankfurt am Main, Germany.

AbstractPURPOSE: To evaluate a novel technique for penetrating keratoplasty (PK) with the use of a new software algorithm for the femtosecond laser,

designed to create penetrating cuts in a top hat configuration.DESIGN: Consecutive histomorphological case series.PATIENTS AND METHODS: Twelve eyes of 12 patients underwent penetrating keratoplasty by means of a 60-kHz femtosecond laser (IntraLase, Irvine, California) with a

software specifically developed for corneal surgery. Of the 12 patients, the reason for keratoplasty was keratoconus in 4 patients, bullous keratopathy in 6 patients, keratotorus in 1 patient, and status post chemical burn in 1 patient. A new software was used to create penetrating cuts in a top-hat-shaped configuration. In all cases, cutting parameters were identical in all donor and corresponding host corneas: 7.0 mm diameter of the anterior side cut, 8.5-8.7 mm diameter of the posterior side cut, and a depth of 300 microm for the lamellar cut. In all cases, a complete penetrating cut with the laser in the host cornea was not intended intraoperatively. Complete penetration was performed subsequently and manually with a diamond knife because of logistic conditions. Trephined corneoscleral rings and button corneas were analyzed macroscopically and histologically to determine cut quality.

RESULTS: All procedures were performed without any complications. With application of appropriate combinations of pulse energy and spacing,

trephination took less than 200 seconds. Macroscopic examination and histology of donor and recipient specimens showed a straight, smooth cut with perpendicular edges in all donor buttons. No corneal edema and no visible damage to the keratocyte nuclei were found. At the region of manual dissection, a small stromal tissue-tag was present in parts of the circumference in all donor buttons. No evidence of any cut complication was noted.

CONCLUSIONS: Top-hat-shaped penetrating keratoplasty using the IntraLase femtosecond laser enables a quick and sufficient

trephination of both human donor and host corneas. It creates favorable histomorphological results with regard to cut quality of the donor and host corneas.

PMID: 19574905 [PubMed - indexed for MEDLINE]

Graefe's Archive for Clinical and Experimental Ophthalmology 2012, DOI: 10.1007/s00417-012-2054-0 Cornea

Clinical results of 123 femtosecond laser-assisted penetrating keratoplasties

Florian Birnbaum, Antonia Wiggermann, Philip C. Maier, Daniel Böhringer and Thomas Reinhard

Abstract

Background Postoperative astigmatism following penetrating keratoplasty is a major problem after corneal transplantation. The

main goal of new trephination techniques such as femtosecond laser or excimer-laser trephination is to improve refractive and visual outcomes. The femtosecond laser technique makes profiled corneal trephinations such as the top hat or mushroom profile possible. We present the postoperative outcome of femtosecond laser-assisted penetrating keratoplasties.

Methods We performed 123 femtosecond laser-assisted penetrating keratoplasties in 119 patients. The main outcome

measures were intraoperative specifics, astigmatism, and irregularity in Orbscan corneal topography, as well as the occurrence of immune reactions and side-effects.

Results All sutures have been removed in 49 of these 123 eyes. Their mean follow-up was 13.9 ± 4.5 months. Time to

complete suture removal (n = 49) was 12.0 ± 3.7 months in the mushroom group and 9.8 ± 2.1 months in the top hat group. Mean astigmatism in Orbscan topography was 6.4 ± 3.0 diopters in the mushroom and 5.8 ± 4.6 diopters in the top hat group (all sutures out).

Conclusions Femtosecond laser-assisted penetrating keratoplasty is a safe surgical technique. Due to the steps in profiled

trephinations, the wound area is larger and theoretically the wound healing is, thus, faster and more stable. Complete suture removal is possible at an earlier time point compared to conventional penetrating keratoplasty. However, refractive results are not superior to those following conventional trephination.

Invest Ophthalmol Vis Sci. 2012 May 4;53(6):2571-9. Print 2012 May.

Manual suction versus femtosecond laser trephination for penetrating keratoplasty: intraocular pressure, endothelial cell damage, incision geometry, and wound healing responses.

Angunawela RI, Riau A, Chaurasia SS, Tan DT, Mehta JS.Source; Singapore National Eye Centre, 11 Third Hospital Avenue, Singapore.

AbstractPURPOSE: To measure real-time intraocular pressure (IOP) during trephination with a manual suction trephine (MST) and the

femtosecond laser (FSL), and to assess endothelial cell damage, incision geometry, and wound healing response with these procedures.

METHODS: IOP was monitored with an intracameral sensor. Eight rabbits underwent manual suction trephination. Eight rabbits had

FSL trephination (FSL-T). Slit lamp photography, confocal microscopy, and anterior segment optical coherence tomography (AS-OCT) were performed at baseline and postoperatively. Animals were sacrificed at 4 hours and 3 days. Tissue was examined with scanning electron microscopy (SEM) and immunohistochemistry for an array of wound-healing markers. Separately, 6 human corneas had MST (3) and FSL-T (3). Incision geometry was imaged with high resolution Optovue AS-OCT.

RESULTS: The average IOP during MST and FSL-T was similar (37 mm Hg). There was wider IOP fluctuation during the MST cutting

phase (60 mm Hg maximum). There were 1-2 rows of endothelial loss on either side of the incision for FSL-T and 2-5 rows deep for MST. Immune cell responses at 4 hours (CD11b) were comparable, greater apoptosis with FSL-T (TUNEL) occurred at 4 hours, and there was increased keratocyte proliferation at 3 days (Ki67) with FSL-T. There was significantly greater undercutting of the cornea with MST (46.86 degrees versus 16.72 degrees).

CONCLUSIONS: There is more IOP variation during MST. Average IOP is 37 mm Hg for both

techniques. More endothelial damage and undercutting of the cornea occurs with MST. The wound healing response to FSL-T appears greater at 3 days.

PMID: 22427557 [PubMed - indexed for MEDLINE]

Br J Ophthalmol doi:10.1136/bjophthalmol-2012-301662 Clinical science

Penetrating keratoplasty using femtosecond laser-enabled keratoplasty with zig-zag incisions versus a mechanical trephine in patients with keratoconus

Ronald N Gaster, Oanna Dumitrascu, Yaron S Rabinowitz + Author AffiliationsCornea Eye Institute, Beverly Hills, California, USA Correspondence to Dr Yaron Rabinowitz, Cornea Eye Institute, Cedars Sinai, 50 N. La Cienega Blvd., Suite 340, Beverly Hills, CA 90211, USA;

rabinowitzy@cshs.orgContributors All authors contributed to the writing, editing and data collection for this paper. Accepted 9 June 2012 Published Online First 11 July 2012

AbstractBackground/aims This paper will compare the visual outcomes of two different penetrating keratoplasty (PKP)

techniques in patients with keratoconus. It is a retrospective comparative surgical case series of 116 keratoconus patients (137 eyes) who had PKP at the Cornea Eye Institute, Beverly Hills, California, USA.

Methods 56 keratoconus patients (66 eyes) underwent femtosecond laser-enabled keratoplasty (FLEK) with a zig-zag incision configuration. Their visual parameters were compared with those of 60 patients (71 eyes) who had traditional blade mechanical trephination PKP. The range of follow-up was between 3 and 6 months. The main outcome measures included uncorrected visual acuity and best spectacle-corrected visual acuity (BSCVA), manifest refractive spherical equivalent and topographically determined astigmatism.

Results BSCVA was significantly better as early as 3 months postoperatively (p=0.001) in the FLEK group. Visual recovery to 20/40 after 3 months was significantly better in the FLEK group (p<0.001). Topographic astigmatism was lower in the FLEK group, but the difference between the two groups reached significance only at 3 months of follow-up (p=0.001). Postoperative complications noted were not different between the two groups.

Conclusions Faster visual recovery and better long-term outcomes were observed in keratoconus patients who had FLEK compared with those who had the mechanical PKP procedure with 6 months of postoperative follow-up.

Fibrin Sealant and Femtosecond Laser Assisted Keratoplasty: Initial ResultsTatiana MB Prazeres1*, Elissandro MS Lindoso1, Leon Grupenmacher2 and Luciene B Sousa31Clinical Fellow, Cornea and External Diseases Division, Department of Ophthalmology, Sorocaba Eye Bank, Sorocaba, Sao Paulo, Brazil2Attending Physician, Department of Ophthalmology, Sorocaba Eye Bank, Sorocaba, Sao Paulo, Brazil3Head Professor of the Department of Ophthalmology, Sorocaba Eye Bank, Sorocaba, Sao Paulo, Brazil

AbstractPurpose: To evaluate whether the use of a sealant combined with interrupted suture would provide better visual

outcomes and better post-operative recovery to keratoconic patients compared to interrupt and running sutures without the use of sealants using femtosecond laser assisted keratoplasty.

Methods: A prospective, randomized study of 12 patients (12 eyes) with keratoconus was conducted, randomized into two treatment groups. The no glue group (6 eyes) underwent penetrated keratoplasty (PK) with femtosecond laser assisted keratoplasty shaped (mushroom) and combined suture (8 interrupted suture and 8 running sutures) while the glue group (6 eyes) underwent the same procedure but their incisions were closed with 8 interrupted sutures and sealant.

Results: The no glue group had a mean BCVA of 0.2 (LogMar). The glue group had a mean BCVA of 0.3 (LogMar). p=0.028 Transplants with glue were well positioned showing good healing but presented more inflammation in the first week post-surgery. Regarding refractive outcomes, there was no difference between the groups.

Conclusions: There were no statistical difference between the two groups regarding BCVA and refractive errors. The use of sealants produced more inflammation. Further studies with a larger number of patients and longer follow up would be needed to confirm these findings.

*Corresponding author: Tatiana Prazeres MB, Rua Conselheiro Correa deMenezes, n266, Apt 701, Salvador, Bahia, Brazil, Tel: 55-71-3334-3084/ 55-71-8799-3084; E-mail: tatianaprazeres@hotmail.comCopyright: © 2012 Prazeres TMB, et al Keywords: Fibrin sealant; Penetrating keratoplasty; Femtosecond laser; Interrupted sutures; Running sutures

Ophthalmology. 2009 Sep;116(9):1638-43. Epub 2009 Jul 31.

Comparison of penetrating keratoplasty performed with a femtosecond laser zig-zag incision versus conventional blade trephination.

Farid M, Steinert RF, Gaster RN, Chamberlain W, Lin A.SourceDepartment of Ophthalmology, The Gavin Herbert Eye Institute, University of California-Irvine, CA 92697, USA.

AbstractPURPOSE: To evaluate visual outcomes and astigmatism in patients who underwent penetrating keratoplasty (PK) with 2 different incision techniques.DESIGN: Retrospective comparison of a consecutive surgical series.PARTICIPANTS: Fifty-seven consecutive patients who underwent PK at the University of California, Irvine, academic referral practice.METHODS: A comparison of 49 eyes of 43 patients that underwent femtosecond laser zig-zag incision pattern PK versus 17 eyes of 14 patients that

underwent conventional Barron suction trephination PK performed contemporaneously. All PKs were closed with an identical, 24-bite running nylon suture technique.

MAIN OUTCOME MEASURES: Topographically determined astigmatism, best spectacle-corrected visual acuity (BSCVA), and recovery of full visual potential.RESULTS: The postoperative follow-up ranged from 1 to 12 months. There was a significant difference in average astigmatism between the groups at

postoperative month 1 (P = 0.013) and 3 (P = 0.018). By month 3, the average astigmatism was 3 diopters (D) in the zig-zag group and 4.46 D in the conventional group. Of the patients with normal macular and optic nerve function (n(ZZ) = 32; n(con) = 14), a significant difference in BSCVA was seen at month 1 (P = 0.0003) and month 3 (P = 0.006) with 81% of the zig-zag group versus 45% of the conventional group achieving BSCVA of > or =20/40 by month 3 (P = 0.03).

CONCLUSIONS: The femtosecond laser generated zig-zag-shaped incision results in a more rapid

recovery of BSCVA and induces less astigmatism compared with conventional blade trephination PK.

FINANCIAL DISCLOSURE(S): Proprietary commercial disclosure may be found after the references.