[Femtosecond laser in cataract surgery. A critical appraisal]

Correlations of Immediate Corneal Tomography Changes with Preoperative and the Elapsed Phaco Parameters

Purpose

The ability to predict corneal edema and understand its relationship with imaging parameters enables optimization of decision-making in terms of cataract surgery. Therefore, we aimed to elucidate the immediate tomographic alterations after phacoemulsification.

Patients and Methods

In this prospective study, we evaluated clinical and corneal tomographic data of 30 patients with cataracts, obtained using a rotating Scheimpflug tomographic system before and after cataract surgery with a phacoemulsification system. Corneal thickness and volume were measured, and Pentacam Nucleus Staging, keratometry, and specular microscopy were performed preoperatively and immediately postoperatively. The Wilcoxon signed-rank test was used to compare pre-and postoperative values. We calculated the correlations between the changes in these values and multiple parameters related to phacodynamics, including “ultrasound (US) elapsed” (phaco time), “US average” (average power used), and “US absolute” (energy effectively dissipated, a product of the other two parameters).

Results

There were increases in corneal volume (p<0.0001) and pachymetry (p<0.0001), and a decrease in endothelial cell count (p<0.0001) after surgery. The mean differences in pre- and postoperative specular microscopy, corneal volume, and pachymetry were −335.13±236.21 cells/mm³, 1.33±0.56 mm³, and 61.33±23.73 microns, respectively. The difference in pre-and postoperative corneal volume in patients with US elapsed ≥40 s was 0.75 mm³ greater than that in patients with US elapsed <40 s (95% confidence interval [CI]: 0.24–1.25; p=0.005); that of pachymetry in patients with US elapsed ≥40 s was 31.76 microns greater than that in patients with US elapsed <40 s (95% CI: 9.55–53.97; p=0.007). Spearman correlation revealed that, for every 1% increase in cataract density, the US average value increased by 0.31% (coef.: 0.3110; 95% CI: 0.0741–0.5490; p=0.012).

Conclusion

Knowledge of Pentacam Nucleus Staging and the effect of US elapsed on differences in corneal volume and pachymetry before and after cataract surgery should be of particular value for surgeons who routinely encounter patients with hard cataracts.

[Posterior YAG capsulotomy: selection of the application pattern]

BACKGROUND

The posterior neodymium-yttrium-aluminum-garnet laser capsulotomy is an established and simple method with a low complication rate for the treatment of secondary cataracts; however, the risk of intraocular pressure elevation, pit marks of the intraocular lens (IOL), anterior hyaloid damage, cystoid macular edema and retinal detachment may increase with high pulse number, pulse energy, and total energy.

PURPOSE

The optimization potential of the method through a rational choice of the laser pattern and the strategy, taking into account the mechanical properties of the posterior capsule and the anatomical features of the retrolental region, is shown.

MATERIAL AND METHODS

The article provides a literature review with own clinical observations and a geometric representation.

RESULTS

The efficiency of a laser pattern is examined with a constant capsulotomy length: The largest opening can be reached with the U‑pattern, which is followed by the +, T, H, V, O and spiral patterns in decreasing order. When estimating the size of the opening, its incircle is of particular functional importance. If the ability of the posterior capsule to tear spontaneously, which is predetermined by its anatomical and mechanical properties, is taken into account when choosing the application pattern and the laser strategy, the efficiency of the method increases.

CONCLUSION

An efficient technique is not only determined by an adapted defocusing and a minimum possible individual pulse energy setting but also characterized by the lowest possible total energy consumption if the necessary opening size is achieved by the smallest number of pulses. Taking into account the individual retrolental anatomical conditions and the mechanical properties of the NS membrane can contribute to the gentle implementation of a YAG capsulotomy.

Transzonular capsulo-hyaloidal hydroseparation with optional triamcinolone enhancement: A technique to detect or induce anterior hyaloid membrane detachment for primary posterior laser capsulotomy

Primary posterior laser capsulotomy (PPLC) requires adequate visualization and spacing of the posterior lens capsule (PLC) and anterior hyaloid membrane (AHM). After intraocular lens implantation and watertight incision hydration, the laser is redocked for optical coherence tomography reimaging. If the PLC and AHM are not imaged or interspaced adequately, transzonular capsulo-hyaloidal hydroseparation is attempted by rinsing the zonular fibers with fluid. If the PLC or AHM are still not detected or discernable, an attempt follows to mark the Berger space using diluted triamcinolone acetate. Before hydroseparation, the AHM or PLC are often invisible or variably attached. If structures cannot be defined, triamcinolone-added hydroseparation is often effective in defining the AHM and Berger space. Transzonular capsulo-hyaloidal hydroseparation with an optional triamcinolone acetate addition can initiate or complete AHM detachment and improve visibility and patency of Berger space for augmenting control and feasibility of PPLC.

Which intraocular lens would ophthalmologists choose for themselves?

PURPOSE

Contemporary cataract surgery is increasingly customizable with the advent of presbyopia-correcting intraocular lenses (IOLs) and the femtosecond laser. The purpose of this study was to determine the types of IOLs ophthalmologists choose for themselves and whether demographic characteristics, surgical experience, and attitudes of ophthalmologists might influence their decision-making. Additional goals included evaluating the use of femtosecond laser use in cataract surgery and investigating surgeon IOL preferences for their patients.

METHODS

We distributed a 29-question Survey Monkey survey to senior ophthalmology residents and practicing ophthalmologists and received 347 responses during a 1-month period. We analyzed 328 surveys using chi-square tests and Fisher's exact tests.

RESULTS

Main outcome measures included surgeons' personal preferences for choice of IOL, femtosecond laser-assisted cataract surgery, and IOL preference for patients. In the setting of no astigmatism, 61.3% of respondents would choose a monofocal IOL set for either distance or monovision for their own surgery. For corneal astigmatism >1.25 D, 60.3% of respondents would choose a toric monofocal lens and only 6.9% would want a femtosecond laser or manual LRI for their own surgery. Of the respondents, 34.6% perform femtosecond laser-assisted cataract surgery, but only 15.3% would want femtosecond cataract surgery performed on themselves. Also, 67.7% implant presbyopia-correcting IOLs (diffractive echelette, multifocal, or accommodative). When correcting for patients' corneal astigmatism >1.25 D, 65.7% of respondents preferred a toric monofocal IOL.

CONCLUSION

Ophthalmologists value quality of vision and are risk averse. Overall, a surgeons' personal preference for their own surgery is correlated with past surgical experience with patients.

Femtosecond laser-assisted cataract surgery, technology, outcome, future directions and modern applications

Since its introduction in 2009 femtosecond laser-assisted cataract surgery (FLACS) has promised to revolutionize cataract surgery. Despite its promise, the assessment of FLACS's perceived benefits has proven to be far more complicated than initially might have been thought. Most studies to date have not provided validation of FLACS technology as a clinically significant advancement on our current techniques. We review FLACS technology and outcomes including detailed analysis of safety, efficacy, cost effectiveness and future prospects using data from the literature and our own published clinical experience.

Effect of femtosecond laser-assisted lens surgery on posterior capsule opacification in the human capsular bag in vitro

PURPOSE

To compare posterior capsule opacification (PCO) by observing lens epithelial cell growth in the human capsular bag in vitro between conventional lens surgery using phacoemulsification (Phaco) technique and femtosecond laser-assisted lens surgery (FLACS).

METHODS

For the in vitro human capsular bag model, 18 cadaver eyes from nine human donors underwent three types of lens surgery. Three groups consisting of six capsular bags were established, that is FLACS, Phaco and extracapsular lens extraction (ECCE). The capsular bag was transferred into equal cell culture conditions after using one of the defined surgical approaches. Cellular growth of lens epithelial cells was observed and photo-documented. The time until full cell-coverage of the capsular bag was measured.

RESULTS

The human capsular bag model can be successfully prepared using FLACS. There was no statistically significant difference in time until cell-coverage of the human donor capsular bag in vitro in all three surgical settings (ECCE versus Phaco p = 0.6; ECCE versus FLACS p = 1.0; Phaco versus FLACS p = 1.0).

CONCLUSIONS

In our in vitro human capsular bag model, we could not observe a statistically significant difference in PCO formation using different surgical approaches of lens extraction. Therefore, PCO formation might not be attributed to the type of surgery. Furthermore, this study shows that FLACS can be used for the human capsular bag model preparation and validates the human capsular bag model for future research.

Standard manual capsulorhexis / Ultrasound phacoemulsification compared to femtosecond laser-assisted capsulorhexis and lens fragmentation in clear cornea small incision cataract surgery

Background

Femtosecond-laser assisted clear cornea cataract surgery may hold promise in safer and more effective procedures. We decided to perform a comparative study to standard manual incision phacoemulsification surgery.

Methods

This is a single-center, single-intervention, and prospective comparative data evaluation of 133 consecutive cases subjected to cataract surgery. Group-A (Phaco), manual capsulorhexis & ultrasound phacoemulsification (n = 66); Group-B femtosecond-laser assisted capsulorhexis and lens fragmentation (n = 67), employing the LenSx laser (Alcon Surgical, Ft. Worth, TX). All cases were evaluated for refraction, visual acuity, keratometry, tomography, pachymetry, endothelial cell counts, intraocular pressure, and type of intraocular lens (IOL) implanted. The groups were matched for age, gender, pre-operative vision metrics, and cataract grade, and were followed up to 1 year.

Results

In group-A post-operative uncorrected distance visual acuity (UDVA) was 20/20 or better in 61.5 % and 20/25 or better in 78.5 % of the eyes. The femtosecond laser group-B had improved outcomes (p = 0.075 and p = 0.042, respectively): post-operative UDVA was 20/20 or better in 62.7 % of the eyes and 20/25 or better in 85.1 %.

Linear regression scatterplots of achieved versus attempted spherical equivalent had excellent regression coefficients (r² = 0.983 in group-A and 0.979 in group-B). There were 75.2 % cases in group-A and 80.6 % in group-B (p = 0.8732) within ±0.50 D of targeted refractive equivalent. Slight trend of under-correction was noted in group-A. Average residual manifest cylinder in the toric subgroup-A was -0.50 D (95 % Limit-of-Agreement (LoA) = -0.78 D), and in toric subgroup-B -0.45 D (LoA = -0.45 D).

Conclusions

Mean spherical equivalent refraction and visual acuity are comparable with laser cataract surgery compared with manual capsulorhexis & ultrasound phacoemulsification. Improved astigmatism correction may be among the benefits of femtosecond laser–assisted cataract surgery. Transient corneal edema may be a first day transient disadvantage in femtosecond laser–assisted cataract surgery.