The benefits and drawbacks of femtosecond laser-assisted cataract surgery

Comparative analysis of changes in retinal layer thickness following femtosecond laser-assisted cataract surgery and conventional cataract surgery

BACKGROUND

To investigate the influence of femtosecond laser-assisted cataract surgery (FLACS) on macula by examining changes in retinal layers after FLACS and to compare these changes with those after conventional cataract surgery (CCS).

METHODS

This study included 113 unrelated Korean patients with age-related cataract who underwent CCS or FLACS in Severance Hospital between September 2019 and July 2021. Optical coherence tomography was performed before and 1 month after surgery. The total retinal layer (TRL) was separated into the inner retinal layer (IRL) and outer retinal layer (ORL); moreover, the IRL was subdivided into the retinal nerve fiber layer, ganglion cell layer, inner plexiform layer, inner nuclear layer (INL), outer plexiform layer, and outer nuclear layer. We performed between-group comparisons of the postoperative thickness in each retinal layer and the postoperative differences in retinal thickness. The average retinal thickness of the four inner macular ring quadrants was used for comparative analysis.

RESULTS

Compared with the CCS group, the FLACS group exhibited a thicker ORL (P = 0.004) and a thinner INL (P = 0.007) after surgery. All retinal layer thickness values showed significant postoperative changes regardless of the type of surgery (P < 0.05). The postoperative increase in TRL and IRL thickness was significantly smaller in the FLACS group than in the CCS group (P = 0.027, P = 0.012).

CONCLUSIONS

The 1-month postoperative retinal changes were less pronounced in the FLACS group than in the CCS group.

Intraoperative quantitative crystalline lens nuclear opacities analysis based on crystalline lenSx platform

PURPOSE

The main objective is to quantify the lens nuclear opacity using spectral-domain optical coherence tomography (SD-OCT) and to evaluate its association with Lens Opacities Classification System III (LOCS-III) system, lens thickness (LT), and surgical parameters. The secondary objective is to assess the diagnostic model performance for hard nuclear cataract.

METHODS

This study included 70 eyes of 57 adults with cataract, with 49 (70%) and 21 (30%) in training and validation cohort, respectively. Correlations of the average nuclear density (AND) /maximum nuclear density (MND) with LOCS-III scores, LT, and surgical parameters were analyzed. Univariate and multivariate logistic regression analysis, receiver operating characteristic curves and calibration curves were performed for the diagnostic of hard nuclear cataract.

RESULTS

The pre-operative uncorrected distance visual acuity (UDVA), intraocular pressure (IOP), mean axial length (AL), and LT were 1.20 ± 0.47 log MAR, 15.50 ± 2.87 mmHg, 27.34 ± 3.77 mm and 4.32 ± 0.45 mm, respectively. The average nuclear opalescence (NO) and nuclear colour (NC) scores were 3.61 ± 0.94 and 3.50 ± 0.91 (ranging from 1.00 to 6.90), respectively. The average AND and MND were 137.94 ± 17.01 and 230.01 ± 8.91, respectively. NC and NO scores both significantly correlated with the AND (rNC = 0.733, p = 0.000; rNO = 0.755, p = 0.000) and MND (rNC = 0.643, p = 0.000; rNO = 0.634, p = 0.000). In the training cohort, the area under the curve (AUC) of the model was 0.769 (P < 0.001, 95%CI 0.620-0.919), which had a good degree of differentiation (Fig. 2a). The calibration curve showed good agreement between predicted and actual probability.

CONCLUSION

The nuclear density measurement on SD-OCT images can serve as an objective and reliable indicator for quantifying nuclear density.

Risk Factors for Corneal Monochromatic Aberrations and Implications for Multifocal and Extended Depth-of-Focus Intraocular Lens Implantation

PURPOSE

To discuss factors influencing corneal aberrations that might influence the optical quality after intraocular lens (IOL) implantation.

METHODS

PubMed and Scopus were the main resources used to search the medical literature. An extensive search was performed to identify relevant articles concerning factors influencing the level of corneal aberrations as of August 27, 2023. The following keywords were used in various combinations: corneal, aberrations, defocus, astigmatism, spherical aberration, coma, trefoil, quadrafoil, intraocular lens, and IOL.

RESULTS

Conclusive evidence is lacking regarding the correlation between age and changes in corneal aberrations. Patients with astigmatism have greater corneal higher-order aberrations than those with minimal astigmatism, particularly concerning trefoil and coma. Increased levels of corneal higher-order aberrations are noted following contact lens wear, in patients with dry eye disease, and with pterygium. Increased higher-order aberrations have been reported following corneal refractive surgery and for 3 months following trabeculectomy; regarding intraocular lens surgery, the results remain controversial.

CONCLUSIONS

Several factors influence the level of corneal higher-order aberrations. Multifocal and extended depth-of-focus IOLs can share similarities in their optical properties, and the main difference arises in their design and performance with respect to spherical aberration. Preoperative evaluation is critical for proper IOL choice, particularly in corneas with risk of high levels of aberrations. [J Refract Surg. 2024;40(6):e420-e434.].

Comparison of short-term clinical outcomes of a diffractive trifocal intraocular lens with phacoemulsification and femtosecond laser assisted cataract surgery

PURPOSE

To evaluate short-term visual and refractive outcomes after implantation of a diffractive trifocal intraocular lens (IOL) in cataract patients with phacoemulsification (PHACO) and femtosecond laser assisted cataract surgery (FLACS).

SETTING

Department of Ophthalmology, Shanghai Aier Eye Hospital, China.

DESIGN

A retrospective, observational study.

METHODS

Patients who underwent cataract surgery combined with Acrysoft IQ PanOptix trifocal IOL implantation were enrolled and divided into three groups: PHACO group, LAstig-FLACS group (astigmatism less then 1D) and HAstig-FLACS group (astigmatism more than 1D). Logarithm of the minimum angle of resolution (logMAR) visual acuity of uncorrected distance (UDVA), intermediate (UIVA), near visual (UNVA), defocus curve, surgically induced astigmatism (SIA) were evaluated in 1 months postoperatively and wavefront aberrations were evaluated in 6 months.

RESULTS

101 eyes of 60 patients were included with 31 eyes in PHACO group, 45 eyes in LAstig-FLACS group and 25 eyes in HAstig-FLACS group. Significant difference was found of internal Strehl Ratio (SR) between PHACO and LAstig-FLACS group (P = 0.026). In PHACO group, 79.31%, 86.21%, 72.41% of eyes gain visual acuity LogMAR 0.1 or more in UDVA, UIVA and UNVA, while 83.72%, 93.02%, 93.02% of those in LAstig-FLACS group and 92.00%, 84.00%, 76.00% in HAstig-FLACS group.

CONCLUSIONS

Panoptix diffractive trifocal IOL provides satisfied visual outcome in no matter FLACS or PHACO. Besides, trifocal IOL implantation via FLACS can provide a better accumulative visual acuity outcome at all distance than PHACO in 1 month. Femtosecond laser assisted limbal relaxing incisions (FLLRIs) is an excellent way to reduce a patient's corneal astigmatism.

Comparing the time efficiency of two lasers used in FLACS: real-world observational study

PURPOSE

To evaluate time efficiencies in the laser room for 2 different femtosecond laser systems.

SETTING

1 private practice in Atlanta, Georgia, and 1 private practice in Los Angeles, California.

DESIGN

Prospective, observational, single-masked study.

METHODS

Patients scheduled to receive femtosecond laser-assisted cataract surgery (FLACS) included those who were not pregnant, had no previous eye surgeries, and were not scheduled to undergo additional surgical procedures at the time of treatment; patients who received a standard, monofocal lens without undergoing arcuate incisions were excluded. Patients taking Flomax or any tamsulosin were also excluded from the study. Each comparable step in the LenSx and CATALYS workflow was identified and clearly defined. Time for each step was evaluated and compared using t tests and regression analyses to control for patient and site-specific differences between the 2 groups.

RESULTS

Time data were collected for 89 patients (89 eyes). The overall procedure was 2.86 minutes shorter for the LenSx system when compared with the CATALYS system ( P < .05). Per patient, the LenSx system had significantly shorter time for patient positioning (57.26 vs 122.00 seconds; P < .05), imaging (33.23 vs 42.17 seconds; P < .05), laser treatment (21.57 vs 39.67 seconds; P < .05), and undocking/transition (67.13 vs 185.30 seconds; P < .05) compared with the CATALYS system. Regression analyses yielded similar results, with the LenSx system being over 35% (3.21 minutes; P < .05) shorter overall than the CATALYS system controlling for location, age, sex, lens thickness, cataract grade, fragmentation pattern, and arcuate incisions.

CONCLUSIONS

LenSx procedures were significantly shorter than the CATALYS procedures overall, which can enable ophthalmology practices to increase efficiency.

Modified Technique of Setting Capsulotomy Thickness in Reducing Capsulotomy-Related Complications During Femtosecond Laser-Assisted Cataract Surgery: A Prospective, Comparative Cohort Study

INTRODUCTION

Although uncommon, incomplete capsulotomy, anterior capsule tags and anterior capsule tears are still encountered during femtosecond laser-assisted cataract surgery (FLACS), resulting in surgical complications. This highlights the need to improve femtosecond laser-assisted capsulotomy technique to reduce capsulotomy-related complications. Therefore, the purpose of this study was to investigate the efficacy of a newly developed, modified technique of setting capsulotomy irradiation thickness in lowering the incidence of capsulotomy-related complications in FLACS.

METHODS

This open-label prospective, comparative cohort study included 440 eyes (220 patients) treated with FLACS using the LenSx laser system (Alcon Laboratories, Inc. Fort Worth, TX, USA). Varying capsulotomy irradiation thicknesses were applied in each eye of the same patient. In Group 1, capsulotomy irradiation thickness was set between the upper edge of the highest point of the anterior capsule and the lower edge of the lowest point of the anterior capsule (modified technique). In Group 2, this was set between the center of the highest point of the anterior capsule and the center of the lowest part of the anterior capsule (conventional technique). Incidence rates of incomplete capsulotomy, anterior capsule tags and tears, and posterior capsule tears were compared.

RESULTS

Preoperative baseline characteristics showed no significant differences. Mean total of the irradiation thicknesses was 877.1 ± 81.9 µm in Group 1 and 808.9 ± 80.0 in Group 2, with a statistically significant difference (P < 0.001). Incidences of incomplete capsulotomy were 1.8% and 7.7%, anterior capsule tags were 2.3% and 8.6%, and anterior capsule tears were 0% and 3.2% in Groups 1 and 2, respectively. These differences were statistically significant (P = 0.006, 0.005, and 0.015, respectively). No posterior capsule tears were reported in either group.

CONCLUSION

The modified technique for capsulotomy in FLACS may significantly reduce the occurrence of capsulotomy-related complications, maximizing the benefits of FLACS.

Cataract Grade and Pupil: Comparison Between Conventional Phacoemulsification and Low-Energy Femtosecond Laser Assisted Cataract Surgery

Purpose

This study presents a comparison of pupil changes according to cataract grade between low-energy femtosecond laser-assisted cataract surgery (FLACS) and conventional phacoemulsification (CP) in the same patient.

Patients and Methods

Data from surgical records from patients submitted to cataract surgery with CP in one eye and FLACS in the other were retrospectively reviewed. The inclusion criterion was both eyes of the same patient having the same cataract grade in accordance with Lens Opacity Classification System (LOCS) III. Total pupil variation (TPV) was measured after recorded images, with intraindividual comparison between techniques, according to cataract grade (≤3 and >3), age and cumulative dissipated energy (CDE).

Results

The study included a total of 124 eyes of 62 patients (mean age 72.65 ± 7.64 years). Analysis showed a statistically significant difference in TPV between techniques in the grade ≤3 cataract group (0.08 ± 0.22 mm²; p=0.034), with less pupil narrowing with FLACS, but not in the grade >3 group (0.01 ± 0.23 mm²; p=0.849). Regarding CDE, a significant difference (p<0.001) was found between techniques in both softer and harder cataracts, with lower values for FLACS. Correlation between CDE and TPV was significant for CP (p=0.021) but not for FLACS (p=0.922). TPV was significantly lower in older patients (age >74 years) for both techniques (p<0.001).

Conclusion

There was a statistically significant difference between techniques (although of mild clinical relevance), with less reduction of pupil area with FLACS in softer cataracts (grade ≤3), as compared to CP. Higher levels of CDE are associated with more pupil narrowing in CP.

TFOS Lifestyle: Impact of elective medications and procedures on the ocular surface

The word "elective" refers to medications and procedures undertaken by choice or with a lower grade of prioritization. Patients usually use elective medications or undergo elective procedures to treat pathologic conditions or for cosmetic enhancement, impacting their lifestyle positively and, thus, improving their quality of life. However, those interventions can affect the homeostasis of the tear film and ocular surface. Consequently, they generate signs and symptoms that could impair the patient's quality of life. This report describes the impact of elective topical and systemic medications and procedures on the ocular surface and the underlying mechanisms. Moreover, elective procedures performed for ocular diseases, cosmetic enhancement, and non-ophthalmic interventions, such as radiotherapy and bariatric surgery, are discussed. The report also evaluates significant anatomical and biological consequences of non-urgent interventions to the ocular surface, such as neuropathic and neurotrophic keratopathies. Besides that, it provides an overview of the prophylaxis and management of pathological conditions resulting from the studied interventions and suggests areas for future research. The report also contains a systematic review investigating the quality of life among people who have undergone small incision lenticule extraction (SMILE). Overall, SMILE refractive surgery seems to cause more vision disturbances than LASIK in the first month post-surgery, but less dry eye symptoms in long-term follow up.

Posterior capsule dynamics during femtosecond laser lens fragmentation

PURPOSE

The dynamics of the posterior capsule during femtosecond laser lens fragmentation has received little attention in the literature. We analysed the movements of the posterior capsule to identify the rupture risk factors, if any, and to suggest possible modification of the laser spot energy pattern during fragmentation.

MATERIALS AND METHODS

Posterior capsule ruptures during fragmentation were identified over a 10-year period of femtosecond laser use. In addition, the dynamics of the posterior capsule were identified through the real-time swept-source OCT lateral view available during the surgeries.

RESULTS

Out of the 1465 laser cataract procedures performed, we recorded 1 case of posterior capsule rupture during lens fragmentation, which was caused by eye movement that was detected but ignored by the surgeon. Three types of posterior capsule dynamics were identified, all related to a gas bubble formation during the first part of the lens fragmentation. In eyes with a hard nucleus, the concussion of the posterior capsule was evident, however, with no capsule rupture.

DISCUSSION

Maintaining good docking throughout the whole procedure seems important in avoiding a posterior capsule cut by the femtosecond laser. In addition, a Gaussian pattern of spot energy is suggested when fragmenting hard cataracts.

Comparison of endothelial cell loss in diabetic patients after conventional phacoemulsification and femtosecond laser-assisted cataract surgery

PURPOSE

This study aims to comparatively evaluate the morphological changes of the cornea after phacoemulsification (PHACO) and femtosecond laser-assisted cataract surgery (FLACS) without intercurrences in patients with type 2 diabetes mellitus.

METHODS

A total of 95 diabetic patients with moderate cataracts (N2 + and N3+), 47 undergoing PHACO and 48 undergoing FLACS, were selected randomly for the study. Surgeries were performed by a single surgeon between July 2021 and December 2021. Cumulative dissipated energy (CDE) and total balanced saline solution (BSS) data were obtained at the end of each surgery. Changes in corneal endothelial cell density (ECD) and central corneal thickness (CCT) at three months postoperatively were investigated.

RESULTS

After three months, evidence is lacking between groups in the CCT measures; the difference was neither statistically nor clinically relevant. However, for ECD, a significant and clinically significant difference was found; if all patients were treated with laser, the mean ECD would be 423.55 greater (RSE: 86.09; p-value < 0.001; 95% CI: 254.81-592.29) than the ECD potential means of 1656.423 among the conventional group (RSE: 74.90; p-value < 0.001; 95% CI: 1509.62-1803.23).

CONCLUSIONS

Diabetic patients under treatment with moderate cataracts may predispose themselves to a more significant loss of endothelial cells after conventional phacoemulsification than femtosecond laser-assisted cataract surgery.

TRIAL REGISTRATION

It was registered at The Brazilian Registry of Clinical Trials (ReBEC) with the code RBR-6d8whb5 (UTN code: U1111-1277-6020) on 17/05/2022.

Mechanical protective effect of lens anterior capsule disc on corneal endothelial cells during femtosecond laser-assisted cataract surgery in a rabbit model

PURPOSE

To evaluate the effects of a novel technique using an isolated lens anterior capsule disc (LACD) to protect corneal endothelial cells in rabbit eyes during femtosecond laser-assisted cataract surgery.

METHODS

Experimental study. 40 rabbits were divided into endothelium-protected (experimental) and control groups, with 20 rabbits in each group. In the experimental group, after femtosecond laser capsulotomy, the isolated capsule disc was lifted to the corneal endothelium by an ophthalmic viscosurgical device. The endothelium was damaged for 1 min with an ultrasonic probe. The control group underwent the same surgery, except that the disc was removed immediately after capsulorhexis. Corneal endothelioscopy was performed preoperatively and on postoperative days (PODs) 3 and 7 to observe endothelial cell counts (ECC) and endothelial cell loss rate. Central corneal thickness (CCT) was measured before and at PODs 1, 3 and 7.

RESULTS

There were 3.59%±1.88% (p < 0.001) and 2.92%±2.14% (p < 0.001) loss of ECC in experimental group at POD3 and POD7, respectively, while those in the control group were 11.62%±7.43% and 10.34%±5.77%, respectively. On POD 1, the difference in central corneal thickness was significant(P = 0.019) between the two groups. At POD 3 and POD 7, CCT was not significantly different (P = 0.597;0.913) between the two groups.

CONCLUSIONS

The isolated LACD technique significantly reduced damage to the endothelium caused by ultrasonic energy and protects corneal endothelial cells during phacoemulsification.

Comparison of Conventional and Femtosecond Laser-Assisted Cataract Surgery Regarding Macula Behavior and Thickness

Background: The aim of the study was to compare macular thickness behavior and clinical outcomes after femtosecond laser-assisted cataract surgery (FLACS) versus phacoemulsification conventional surgery (PCS). Methods: Macular Optical Coherence Tomography OCT was analyzed in 42 patients preoperatively, 1 day, 12 days, 4 weeks and 6 weeks postoperatively according to the 9-field Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Clinical findings were collected in both the FLACS group and the PCS group. Results: There was no significant difference in macular thickness between the FLACS and PCS groups (p > 0.05). However, from postoperative day 12 onwards, there was a significant increase in macular thickness observed in both groups (p < 0.001). In the FLACS group, a significant increase in visual acuity was observed on the first postoperative day, as compared to the PCS group (p = 0.006). Conclusions: The use of a low-energy high-frequency femtosecond laser has potentially no effect on postoperative macular thickness. In the FLACS group, visual rehabilitation was significantly faster as compared to the PCS group. No complications occurred intraoperatively in either group.

Cataract surgery astigmatism incisional management. Manual relaxing incision versus femtosecond laser-assisted arcuate keratotomy. A systematic review

PURPOSE

This systematic review aims to compare corneal astigmatism correction in cataract surgery through corneal relaxing incision, manually and femtosecond laser assisted.

METHODS

The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. We used PubMed, Scopus, and Web of Science (WOS) as databases from January 2010 to March 30, 2021. Patients with keratoconus, corneal ectasia, and a previous history of eye surgery were excluded because our aim was to analyze only healthy eyes.

RESULTS

A total of 1025 eyes were evaluated from 946 patients (mean age was 68.90 ± 5.12) in manual incision group articles, while 1905 eyes of 1483 patients (mean age was 65.05 ± 4.57) were evaluated in femtosecond laser arcuate keratotomy (FLAK) articles. The mean uncorrected distance visual acuity (UDVA) was 0.19 ± 0.12 and 0.15 ± 0.05 logMAR for manual incision and FLAK articles, respectively (p = 0.39). The mean correction index (CI) was similar in both groups: 0.77 ± 0.18 in manual incision and 0.79 ± 0.17 in femtosecond laser assisted incision (p = 0.70). Refractive stability was found after 3 months and no serious complications were reported during the follow-up in any group.

CONCLUSION

Both techniques are safe and moderately effective in corneal astigmatism correction in cataract surgery. FLAK represents a more precise and predictable approach. However, since visual and refractive outcomes appear to be similar in both cases, the cost-benefit analysis is controversial.

Portable femtosecond laser assisted cataract surgery in a child with bilateral ectopia lentis with microspherophakia

Purpose

The purpose of this case report is to describe the utility of portable femtosecond laser platform in a child with bilateral isolated microspherophakia and ectopia lentis performed under general anesthesia.

Observation

An appropriately sized and well centered capsulotomy with well centered PCIOL could be achieved in both eyes of the patient.

Conclusion & Importance

The advent of mobile femtosecond laser assisted cataract surgery might prove a useful and convenient platform for surgeries in pediatric patients with subluxated cataracts even under general anesthesia. It may circumvent the need for an additional laser suite and reduce surgical time by eliminating the need for patient movement.

Lens capsule-related complications in femtosecond laser-assisted cataract surgery: a study based on video analysis

PURPOSE

To analyse the occurrence and potential causes of lens capsule-related complications during femtosecond laser-assisted cataract surgery (FLACS).

METHODS

This prospective consecutive cohort study included the first 1600 eyes (from 1140 consecutive patients) who received FLACS performed by the same surgeon from May 2015 to December 2018. The potential causes and characteristic signs of capsulotomy-related complications, including incomplete capsulotomies and radial anterior capsule (AC) tears, were summarised based on the agreement of two ophthalmologists after they analysed the surgical videos. Subgroup analysis was conducted to characterise the capsulotomy learning curve.

RESULTS

Of the 1600 eyes, 52 (3.25%) had incomplete capsulotomies and 22 (1.38%) had radial AC tears. The most common causes of incomplete capsulotomies were eye tilt (16 eyes, 30.77%), air bubbles or ocular secretions at the interface (14 eyes, 26.92%) and white cataracts (7 eyes, 13.46%). Additionally, 54.55% (12/22) of AC tears were due to incomplete capsulotomy and secondary capsulorhexis. A significant difference was noted between the first 200 eyes and subsequent groups in terms of the incidence of incomplete capsulotomies. No difference was observed in the incidence of AC tears after the initial 100 procedures.

CONCLUSION

The most common causes of incomplete capsulotomies were eye tilt and air bubbles or ocular secretions at the interface. Secondary capsulorhexis after incomplete capsulotomy is the main risk factor for AC tears. There was a steep learning curve for laser capsulotomy in the first 100 operated eyes, as evidenced by the higher complication rate, but this stabilised after 200 procedures.

CONTEMPORARY PRACTICES IN CATARACT SURGERY - SUBJECTIVE PREFERENCES OF CZECH CATARACT SURGEONS

AIMS

The aim of the work was to find out the current subjective preferences of Czech cataract surgeons in terms of individual procedures, techniques and materials used during cataract surgery.

MATERIAL AND METHODS

This study was conducted in the form of a questionnaire (online, a total of 44 questions). The survey respondents were members of the Czech Society of Refractive and Cataract Surgery. Questions 1-10 concerned the characteristics of the respondent (age, number of operations performed, type of workplace, etc.). Questions 11-20 focused on the surgical procedure used by the specific surgeon (anaesthesia, viscomaterial, position of the main incision, use of antibiotics at the end of the operation, etc.). Questions 21-34 concerned the type of intraocular lens used. Lastly, in questions 35-44, respondents were asked about their individual preferences if cataract surgery were to be performed on them.

RESULTS

The questionnaire was fully or partially completed by 72 surgeons (26% of the originally approached subjects). Most of the respondents were experienced surgeons, 74.5% of them have been performing surgeries for more than 10 years, out of which 55.5% perform more than 500 operations per year. The average age of the respondents was 50 years. 65.3% of surgeons use hydroxypropylmethylcellulose during surgery, 74% do not use a femtosecond laser for surgery, 50% never perform posterior circular capsulorhexia, and 98% apply antibiotics to the anterior chamber at the end of surgery. Surgeons predominantly use hydrophobic (80.8%), aspherical (72.3%), clear (54.3%), single-focal (97.9%) and non-preloaded (78.3%) lenses. However, if they were not limited or restricted in any way in their choice, they would prefer aspherical lenses (94.6%), multifocal or extended-focus lenses (78%) and preloaded lenses (96.8%).

CONCLUSION

The subjective preferences of Czech cataract surgeons are relatively variable regarding the individual steps. Often the procedures used do not always correspond with the actual preferences of the surgeon. On the contrary, there is almost complete unity in the steps recommended by professional societies (intracameral antibiotics at the end of the operation).

Flap Thickness and the Risk of Complications in Mechanical Microkeratome and Femtosecond Laser In Situ Keratomileusis: A Literature Review and Statistical Analysis

INTRODUCTION

A recent Cochrane review found no difference in visual acuity outcomes between femtosecond-assisted laser in situ keratomileusis (LASIK) and LASIK using mechanical microkeratomes (MMKs). This study compares the flap thickness and risk of complications related to flap creation using femtosecond lasers and MMKs.

METHODS

PubMed and the Web of Science are used to search the medical literature. An extensive search is performed to identify the flap thickness and complications of LASIK as reported up to 15 July 2021. The following keywords are used in various combinations: Corneal flap, femtosecond laser, laser in situ keratomileusis, laser-assisted in situ keratomileusis, LASIK, mechanical microkeratome.

RESULTS

After removing duplicates and irrelevant studies, 122 articles were included for review. Pooled differences for intended vs. postoperative flap thickness using MMKs and femtosecond laser were -4.07 μm (95% CI: -19.55, 3.24 μm) in studies on the MMK and 5.43 μm (95% CI: 2.30, 7.84 μm; p < 0.001), respectively. After removing the studies evaluating outcomes of the old generation Hansatome MMKs (which had a significantly greater variation of flap thickness), the pooled difference for newer MMKs was 4.97 μm (95% CI: 0.35, 9.58 μm; p < 0.001), but the results still favored the femtosecond laser. Uncommon and mild complications unique for the femtosecond LASIK are epithelial gas breakthrough, opaque bubble layer, transient light sensitivity syndrome, and rainbow glare. A single study reported a very low, but stastically different risk of postoperative flap slippage (0.033% for MMK LASIK, and 0.003% for femtosecond LASIK, respectively).

CONCLUSION

In both manual microkeratome and femtosecond LASIK, intra- and postoperative complications were uncommon. The evidence of the superiority of one technique in terms of complications over another cannot be indisputably stated.

Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept

This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled.

Ocular surgery after herpes simplex and herpes zoster keratitis

PURPOSE

The recurrence of herpetic stromal keratitis (HSK) and herpes zoster ophthalmicus (HZO) has been reported after a variety of ocular surgeries. The aim of this study was to review the evidence on the preventive methods employed in the perioperative period in patients having undergone HSK/HZO.

METHODS

The PubMed and Web of Science databases were the main resources used to conduct the medical literature search. An extensive search was performed to identify relevant articles concerning the prophylaxis against and risk of HSK/HZO recurrence in patients undergoing ocular surgery up to December 31, 2019.

RESULTS

The disturbance of the corneal nerve plexus occurs during several ocular surgeries including penetrating keratoplasty, lamellar keratoplasty, corneal cross-linking, cataract surgery, as well as photorefractive and phototherapeutic procedures. Such trauma, as well as modulation of the ocular immunological response caused by steroids applied postoperatively, might engender the HSK/HZO reactivation which is not uncommon. There is strong evidence that oral prophylaxis should be recommended just after surgery in patients undergoing penetrating keratoplasty and having suffered from HSK/HZO. For other types of surgeries, the evidence is less compelling; nevertheless, a period of disease quiescence and oral prophylaxis should still be considered.

CONCLUSIONS

Within the article, we discuss the available evidence for HSK/HZO prophylaxis in ocular surgery. Additional studies would be required to define the real risk of HSK/HZO recurrence following eye surgeries, and particularly cataract surgery, and to confirm the utility of perioperative HSK/HZO prophylaxis.

Effects of Combinations of Ophthalmic Viscosurgical Devices and Suction Flow Rates on the Corneal Endothelial Cell Damage Incurred during Phacoemulsification

We examined the effects of different ophthalmic viscosurgical devices (OVDs) and suction flow rates during phacoemulsification on the amount of ultrasound power used and damage to the corneal endothelium. In total, 48 eyes of 24 patients who underwent phacoemulsification and intraocular lens insertion with different OVD settings in the left and right eye between February and August 2018 were examined retrospectively from medical records. Each of the following types of OVDs was used in either the right or left eye of each patient: a viscoadaptive OVD (V group) or a combination of dispersive and cohesive OVDs (soft-shell technique; S group). There was no significant difference in the lens nucleus hardness between the two groups. A 2.4 mm transconjunctival scleral incision was made, and phacoemulsification was performed by the same surgeon. The cumulative dissipated energy (CDE) and ultrasound time intraoperatively were compared between the two groups. The CDE was significantly larger in the V group (9.9 ± 4.6) than the S group (6.4 ± 3.0; p=0.006). The reduction rate of the endothelial cell density at the center of the cornea was significantly higher in the V group (4.1% ± 6.7%) than the S group (0.3% ± 4.5%; p=0.03) at 1 week postoperatively. Both groups had a good postoperative course. There was less corneal endothelial damage with the soft-shell technique combined with a normal flow setting than the viscoadaptive OVD combined with a low flow setting.