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  5. FP607 : Comparative Evaluation of Nucleotomy Patterns in Femtosecond Laser Assisted Cataract Surgery

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Dr. Manpreet Kaur, K18920, Dr. Falera Ruchita Clara, Dr. Jeewan S Titiyal

Abstract

Purpose: To evaluate intraoperative and postoperative outcomes with chop or matrix nucleotomy patterns during femtosecond laser assisted cataract surgery (FLACS).

Methods: Randomised control trial of 66 eyes with grade III-IV nuclear sclerosis that underwent nucleotomy using matrix (Group I, n=33) or chop (Group II, n=33) pattern during FLACS. Intraoperative phacoemulsification parameters, postoperative visual acuity and specular counts were evaluated.

Results: Cumulative dissipated energy (CDE) [Group I=6.2±5.1, Group II=9.4±4.5; p=0.008] and total phacoemulsification time (PT) [27.7±20.5, Group II=43.3±17.6; p=0.001] was significantly less in group I. No difference was observed in one month postoperative visual acuity; specular counts were significantly less in group II (Group I=2570.8 ±226.9, Group I=2426.2±221.8 cells/mm2; p=0.01).

Conclusion: Matrix pattern decreases CDE and PT and causes less endothelial cell loss than chop pattern in grade III-IV nuclear sclerosis. 

Introduction

Femtosecond laser technology has continuously evolved since its initial use in cataract surgery in 2008 by Nagy et al.1 Since then, the superiority of femtosecond laser assisted cataract surgery over conventional phacoemulsification has been demonstrated in terms of incision construction, lens fragmentation and capsulotomy creation.2-4 Currently four different femtosecond laser platforms are available for clinical use- the LenSx (Alcon LenSx, Fort Worth, Texas), the Catalys (Optimedica Catalys, Santa Clara, CA, USA), the LensAR (LensAR Inc., Orlando, FL, USA) and the Victus (Technolas Perfect Vision and Bausch and Lomb, Rochester, NY, USA).

The LenSx system was the first laser platform to be FDA approved for use in cataract surgery in 2010 for corneal incisions, lens fragmentation, capsulotomy and arcuate incions. The initial versions included the chop and cylinder pattern of nucleotomy, and the matrix phacofragmentation pattern was introduced in the upgraded version 2.23.The matrix pattern of phacofragmentation divides the nucleus into microfragments which can be easily aspirated by the phacoemulsification tip, and is expected to further reducethe phacoemulsification time and collateral tissue inflammation.

We herein conducted a prospective randomised study to evaluate the intraoperative and postoperative outcomes with chop or matrix nucleotomy patterns during femtosecond laser assisted cataract surgery (FLACS).

Methods:

A prospective randomised control trial of 66 patients undergoing FLACS was conducted at an apex tertiary care ophthalmic centre. Informed consent was obtained from all patients. Ethical clearance was obtained from the institutional review board and the study adhered to the tenets of the Declaration of Helsinki.

All eyes with grade III-IV nuclear sclerosis posted to undergo FLACS were included in the study. The cataract was graded according to the Lens Opacities Classification System III (LOCS III). Eyes with maximum pupil dilation < 6 mm, pseudoexfoliation syndrome, glaucoma, posterior pole pathology and prior ocular surgery were excluded from the study. The cases were randomized into two groups- Group I (n=33) underwent nucleotomy using matrix pattern and group II (n=33) underwent nucleotomy using chop pattern during FLACS. Randomisation was done using a computer generated random number table. The patients were not age or gender matched.

The preoperative detailed examination included uncorrected distance visual acuity (UDVA), anterior segment evaluation, slitlamp biomicroscopy, applanation tonometery and biometry (Tonoref III, Nidek Co., Ltd. And OcuScan RxP, Alcon Laboratories, Inc.).

Surgical technique

The preoperative planning of the corneal incisions, capsulotomy and nucleotomy was done on LenSx version 2.23 femtosecond laser system (Alcon LenSx, Inc., Aliso Viejo, California). A 4.9 mm capsulotomy was planned, with a 2.2 mm temporal clear corneal incision and two 1.1 mm side ports at 90° and 240°. In group I, the chop pattern of nucleotomy was selected, with three chops of length 6 mm each. In group II, the matrix pattern of nucleotomy was selected (4 mm grid with 350 micron fragments, two horizontal cuts and 8 radial spokes of 1 mm length each). The anterior offset was kept at 500 µm and the posterior offset was kept at 800 µm. The energy was kept at 6 µJ for corneal incisions, 8 µJ for capsulotomy and 12 µJ for nucleotomy. The spot and layer separation was 5 microns for the side port incisions, 6 microns for 2.2 mm corneal incision and 14 microns for the nucleotomy. For capsulotomy, the spot separation was 5 microns, the layer separation was 4 microns and the anterior and posterior delta value was 350 µm each. Successful dock was achieved using a SoftFitTM applanating patient interface.  The anterior segment structures were imaged with intraoperative optical coherence tomography (OCT) and the planned treatment was verified.

After femtosecond laser application, the corneal incisions were opened with the help of flap lifter. Sodium hyaluronate 1% was injected to maintain the anterior chamber and the capsulotomies were lifted and removed with the microcapsulorhexis forceps. Hydrodissection was performed, followed by phacoemulsification (CENTURION Vision System, Alcon Laboratories,Inc.), irrigation-aspiration and implantation of single-piece hydrophobic acrylic IOL in the bag. For phacoemulsification, 20 gauge microtip with external diameter of 0.9mm and internal diameter of 0.66 mm was employed. The corneal wounds were hydrated at the end of the procedure.

Intraoperatively, the total surgical time, cumulative dissipated energy (C.D.E.), total ultrasound time and total aspiration time were noted. Intraoperative complications such as anterior capsular tears/extension, posterior capsular tears, vitreous loss, need for anterior vitrectomy and inability to implant IOL were noted. Postoperatively, UDVA and corrected distance visual acuity (CDVA) were noted. Anterior segment evaluation and specular microscopy were performed. All cases were followed up on the first postoperative day and after one month.The primary outcome measures were intraoperative phacoemulsification parameters including the cumulative dissipated energy (CDE) and the total phacoemulsification time. The secondary outcome measures were the intraoperative complications, postoperative visual acuity and the postoperative specular counts. Masking was not done.

Results:

The mean age of the patients was 62.9 ± 9.1 years in group I and  64.8 ± 8.3 years in group II (p=0.34). Group I consisted of 15 males and 18 females; group II had 19 males and 14 females. All cases had grade III-IV nuclear sclerosis (LOCS III).

Cumulative dissipated energy (CDE) in Group I was 6.2±5.1 and 9.4±4.5 in group II; p=0.008. Totalultrasonic time (PT) was 27.7±20.5 seconds in group I and 43.3±17.6 seconds in group II; p=0.001. Total aspiration time was 3.9 ± 0.9 minutes in group I and 4.3 ± 1.3 minutes in group II; p=0.116. Total duration of phacoemulsification was 6.3 ± 1.9 minutes in group I and 6.7 ± 2.2 minutes in group II; p=0.4.

No case had posterior capsular rent or vitreous loss in either group. Slit lamp examination on postoperative day 1 revealed central corneal edema in 21.2% cases (7/33) in group I and 33.3% cases (11/33) in group II; p=0.4. The corneal edema was mild and self-resolving in all cases, and no case had persistent corneal edema at day 30.

The mean logMAR UDVA was 0.072 ± 0.123 in group I and 0.124 ± 0.143 in group II (p=0.123) on POD 1. The mean logMAR CDVA was 0.015 ± 0.036 in group I and 0.018 ± 0.053 in group II (p=0.787) on POD 1. At 1 month, mean logMAR UDVA was 0.03 ± 0.06 in group I and 0.039 ± 0.07 in group II (p=0.364), and the mean logMAR CDVA was 0.009 ± 0.029 in group I and 0.015 ± 0.044 in group II (p=0.513).

The postoperative specular counts on day 30 were 2570.8 ±226.9 in group I and 2426.2±221.8 cells/mm2 in group II; p=0.01.

Discussion:

Femtosecond laser assisted nucleotomy has been shown to result in a decreased effective phacoemulsification time when compared with conventional phacoemulsification.4,5Decreased phacoemulsification time and energy are beneficial to preserve endothelial cell count and prevent corneal decompensation, and we examined the effect of two femtosecond nucleotomy patterns on these parameters in grade III-IV nuclear sclerosis.

In our study, the CDE and total ultrasonic time were significantly less in the group undergoing matrix pattern of nucleotomy. The 350 micron nuclear fragments could be easily aspirated in the lumen of the phacoemulsification tip without need for further fragmentation or emulsification. The eight peripheral 1 mm spokes provided planes for segmentation of the remnant nucleus and epinucleus into small fragments, thus enabling easier emulsification with minimum energy. The chop pattern allowed easy segmentation of the lens into six segments, however further emulsification was required before aspiration of the lens matter. These differences accounted for a lesser CDE as well as total ultrasonic time with the matrix pattern.

This is the first study comparing nucleotomy patterns of the LenSx laser platform. Previous studies have studied the effects of the Catalys laser fragmentation patterns on the intraoperative phacoemulsification parameters. Abell et al compared the 500 micron softening grid pattern with the 400/200 micron segmentation and softening grid pattern available on the Catalys laser platform. They reported a 28.6% reduction in the effective phacoemulsification time within the femtosecond group using improved lens fragmentation algorithms.5 Hyseynova et al evaluated 71 eyes undergoing FLACS with either the ‘quadrant’ or ‘complete’ nucleotomy pattern on the Catalys laser system. They reported that the smaller fragmentation pattern (Complete) of the femtosecond laser was more beneficial, with a 44.7% reduction in EPT and a 40.9% reduction in phaco power when compared with the larger fragmentation pattern (Quadrant).6

The central corneal edema was more on the first postoperative day with the chop pattern, however, the difference was not statistically significant. The edema was self-resolving and mild, and did not persist in any case after one month. The endothelial cell density as assessed by specular microscopy after one month was significantly higher in the group of cases undergoing matrix pattern of nucleotomy. To our knowledge, no study in literature has compared the endothelial cell densities with different phacoemulsification patterns. The lesser endothelial cell loss as observed with the matrix pattern holds more significance for cases with compromised endothelium, such as Fuchs’ endothelial dystrophy, glaucoma and pseudoexfoliation syndrome. Although this group of patients was excluded from our present study, using the new matrix pattern of nucleotomy in these cases may help preserve the endothelial cell counts. Further studies may be undertaken to evaluate the benefit of matrix pattern in such cases and compare them with conventional phacoemulsification. The visual outcomes in both groups were comparable.

To conclude, matrix pattern of nucleotomy decreases the CDE and PT as compared to the chop pattern. The endothelial cell loss is less in cases with the matrix pattern, and this may be especially beneficial in cases with pre-existing compromised endothelium.

References:

  1. Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Refract Surg 2009;25:1053– 60
  2. Masket S, Sarayba M, Ignacio T, Fram N. Femtosecond laser-assisted cataract incisions: architectural stability and reproducibility. J Cataract Refract Surg 2010; 36:1048–1049.
  3. Kránitz K, Takacs A, Miháltz K, et al. Femtosecond laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg 2011;27:558–63.
  4. Conrad-Hengerer I, Hengerer FH, Schultz T, Dick HB. Effect of femtosecond laser fragmentation on effective phacoemulsification time in cataract surgery. J Refract Surg 2012; 28:879–883.
  5. Abell RG, Kerr NM, Vote BJ. Toward zero effective phacoemulsification time using femtosecond laser pretreatment. Ophthalmology. 2013 May;120(5):942-8.
  6. Huseynova T, Mita M, Corpuz CC, Sotoyama Y, Tomita M. Evaluating the differentlaser fragmentation patterns used in laser cataract surgeries in terms ofeffective phacoemulsification time and power. Clin Ophthalmol. 2015 Nov6;9:2067-71.

 

 

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