Evaluation of femtosecond laser-assisted anterior capsulotomy in the presence of ophthalmic viscoelastic devices (OVDs)

Abstract

The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag’s arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.

Evaluation of the Optical Aspects of the Ophthalmic Viscosurgical Device During Femtosecond Laser-Assisted Cataract Surgery

“…The absorption coefficient is an intrinsic physical property of a material, aside from its refractive index or viscosity, and as 13.5% laser power attenuation is considerably large, absorption through OVDs must be considered. Although the probability of achieving a complete capsulotomy increases when 150% of energy is used, as indicated by results of the previous study, 21 an increase in laser energy can adversely affect capsulorhexis, such as capsular adhesion and an increased risk of anterior-capsular tags. 22 Therefore, it is important to increase laser energy appropriately through accurate calculations.…”

“… 19 In a recent study, an incomplete capsulotomy was observed more frequently when using a high-viscosity OVD than when using a low-viscosity OVD, suggesting that high-viscosity OVDs could reduce the efficacy of the femtosecond laser by prolonging the lifetime of the bubble and reducing the impact velocity. 20 , 21 Therefore, in addition to our results, the effect of cavitation bubbles should be considered; the relationship between the viscosity of OVD and bubble generation will be investigated through future studies using a streak camera with different laser powers.…”

“…In a previous study using porcine eyes, an incomplete capsulotomy occurred less when using 150% of energy compared to when using 90% of energy, and the efficiency of FLACS could be enhanced with high energy in the presence of OVDs. 21 The authors of the previous study mentioned the possibility of a detrimental effect on capsulotomy formation by cavitation bubbles; however, they did not count the absorption of laser by OVDs. The absorption coefficient is an intrinsic physical property of a material, aside from its refractive index or viscosity, and as 13.5% laser power attenuation is considerably large, absorption through OVDs must be considered.…”

Effects of Different Capsulotomy and Fragmentation Energy Levels on the Generation of Oxidative Stress Following Femtosecond Laser-Assisted Cataract Surgery

“…In the current study, we showed that FSL capsulotomy using a low-energy FSL system did not result in the increased generation of intracameral free radicals, and an increase in the capsulotomy energy level did not lead to further increases in free radicals. An increase in the capsulotomy energy level is useful in the case of capsulotomy formation in the presence of an OVD in the anterior chamber [ 25 , 26 ]. Increases in the FSL capsulotomy energy levels did lead to increased concentrations of pro-inflammatory IL-8 [ 11 ].…”

Recent developments in anterior capsulotomy for cataract surgery

“…A 2021 study compared the capsulotomy quality in low-energy versus high-energy FLACS, and found that in 200 eyes ( n = 100 for each group), a lower energy FLACS system provided significantly better results for completeness of the capsulotomy, intraoperative miosis, and subconjunctival hemorrhage [43 ▪ ]. However, another study comparing femtosecond laser energies in porcine eyes with different ophthalmic viscoelastic devices ( n = 96) found that higher energy settings improve capsulotomy results (circularity and tag-parameters) across all OVDs [44]. An analysis of 3834 FLACS capsulotomies found that anterior capsule tear rates are low, and can be reduced by an increase in vertical spacing; tear rates were 0.79, 0.35, and 0.09% respectively for the 10, 15, and 20 μm vertical spacing groups [45].…”