Risk Factors for Insufficient Fixation of Microkeratome During Laser in situ Keratomileusis

Options and results in managing suction loss during small-incision lenticule extraction

Suction loss is an intraoperative complication in small-incision lenticule extraction (SMILE) that presents a management challenge for the refractive surgeon. The purpose of this review is to evaluate the visual, refractive, and wavefront outcomes after suction loss across the different stages of SMILE with various respective surgical treatments. Surgical management options include immediate re-SMILE by redocking or delayed re-SMILE, with or without adjustment of the laser parameters, conversion to femtosecond laser in situ keratomileusis, transepithelial photorefractive keratectomy, refractive lenticule extraction, or pseudo-SMILE. The restart treatment module on VisuMax provides appropriate retreatment recommendation. Most retreatment options for suction loss, immediate or delayed, resulted in effective, safe, and predictable outcomes, and patients were satisfied with their outcomes. Based on available level II evidence, immediate re-SMILE with or without adjustment to the laser settings achieve favorable visual and refractive outcomes in handling this intraoperative complication across all stages of SMILE.

Three-Year Follow-Up of Laser In Situ Keratomileusis Treatments for Myopia: Multi-Center Cohort Study in Korean Population

This multi-center cohort study included 3401 myopic laser in situ keratomileusis (LASIK) procedures conducted in 1756 myopia patients between 2002 and 2005. Pre- and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and manifest refraction spherical equivalent (SE) were recorded. Factors predicting low postoperative efficacy (defined as a postoperative UCVA < 0.5) were identified using univariate and multivariate logistic regression analysis. Compared with 1 month postoperatively, logMAR UCVA at 3 months postoperatively was significantly decreased (p = 0.002) and that at 2 and 3 years was significantly increased (p < 0.001). LogMAR BCVA at 2 years postoperatively was significantly decreased compared with 1 month postoperatively (p = 0.008). Over the 3-year postoperative period, overall refractive predictability within ±1.00 D and ±0.50 D ranged from 69.0% to 86.2% and from 43.3% to 67.8%, respectively. This also decreased from 1 month to 6 months postoperatively (p < 0.005). Multivariate logistic regression analysis using generalized estimating equations, revealed that higher preoperative SE (odds ratio [OR], 2.58 and 7.23; p < 0.001) and lower preoperative BCVA (OR, 2.44; p = 0.003) were predictive of a low postoperative efficacy. In summary, myopic LASIK can be effective and safe with a high refractive predictability in a Korean population, but myopic regression occurs over time. Higher preoperative SE and lower preoperative BCVA are predictive of a low postoperative efficacy.

Dry eye after LASIK: Comparison of outcomes for Asian and Caucasian eyes

BACKGROUND

Dry eye is a common complication of LASIK surgery. Our clinical impression was that post-LASIK dry eye was more problematic for our Asian patients. The aim of this study was to determine if dry eye after LASIK is more prevalent, more sustained and more severe in Asian eyes compared with Caucasian eyes.

METHODS

This study was based on a retrospective analysis of a clinical database. Data (n = 932 eyes, 932 patients) was collected before and after (week 2 and months 1, 3 and 6) LASIK surgery. Patients were defined as Asian if both parents were of East Asian ethic origin. Assessments included dry eye symptoms, ocular surface staining, tear volume, tear secretion, tear film stability and corneal sensation.

RESULTS

Asian eyes had greater ocular surface staining, poorer tear film stability and lower tear volume before LASIK and at all times after LASIK. Dry eye symptoms occurring 'often or constantly' were more prevalent at all time points after LASIK in Asian eyes. Chronic dry eye persisting six months or more after LASIK was diagnosed in 28 per cent of Asian eyes and 5 per cent of Caucasian eyes (p < 0.001). Asian patients with chronic dry eye were predominantly female, reported dry eye symptoms, had greater ocular surface staining and lower tear secretion, stability and volume before surgery. After LASIK, Asian eyes had a slower return to pre-operative values for ocular surface staining, tear volume and corneal sensation.

DISCUSSION

The risk of chronic dry eye after LASIK was significantly higher in Asian eyes. Contributing factors could include racial differences in eyelid and orbital anatomy, tear film parameters and blinking dynamics and higher attempted refractive corrections in Asian eyes.

Microkeratome complications

PURPOSE OF REVIEW

Complications from laser in-situ keratomileusis surgery are extremely rare. However, most of the complications involve construction of the corneal flap, which is fashioned using various mechanical or femtosecond laser microkeratomes. Here, we review and discuss complications of microkeratome flaps.

RECENT FINDINGS

Several large studies of microkeratome laser in-situ keratomileusis cases report a similar set of complications: partial or irregular flaps, buttonholes, and free flaps. Risk factors for these complications include increased age, preoperative hyperopia, and years of contact lens wear. Numerous animal and clinical studies have shown that the femtosecond platform produces flaps with greater stability with more consistent and accurate dimensions than the mechanical microkeratome. However, there is no significant difference in final visual outcome.

SUMMARY

The aim of this review is to report complications associated with mechanical microkeratomes in the construction of laser in-situ keratomileusis flaps and to see whether there is a significant disadvantage compared with the femtosecond laser.

Five-Year Outcome of LASIK for Myopia

PURPOSE

To investigate the efficacy and safety of LASIK over a 5-year postoperative period.

DESIGN

Observational case series.

PARTICIPANTS

We examined 779 eyes in 402 patients with myopia or myopic astigmatism who underwent LASIK to correct their refractive errors and received regular postoperative assessments for 5 years.

METHODS

Postoperative examinations were performed 1 day; 1 week; 1, 3, and 6 months; and 1, 2, 3, 4, and 5 years after LASIK surgery.

MAIN OUTCOME MEASURES

We evaluated changes in uncorrected visual acuity (UCVA) (logarithm of the minimum angle of resolution [logMAR]), manifest refraction, best-corrected visual acuity (BCVA) (logMAR), intraocular pressure, corneal thickness, corneal endothelial cell counts, and complications.

RESULTS

Preoperative UCVA of 1.27 improved to -0.03 at 1 day after surgery and -0.08 at 1 month and revealed minimal but significant decreases thereafter. Postoperative manifest refraction was also improved by surgery, showing minimal but significant regression after 1 year. Final BCVA loss was seen in 10 eyes of 7 patients; in 7 cases, there were obvious reasons such as the progression of cataracts in 3 eyes, epithelial disintegrity due to dry eye in 2 eyes, irregular astigmatism due to flap striae in 1 eye, and age-related macular dystrophy in 1 eye. Intraocular pressure and corneal thickness decreased by 4.0 mmHg and 76.9 microm, respectively, due to surgery, but remained stable throughout the follow-up period. Corneal endothelial cell counts (2689.0+/-232.9 cells/mm(2) before surgery) showed a statistically significant decrease at 5 years after surgery (2658.0+/-183.1 cells/mm(2); 1.2% loss for 5 years), likely within the range due to physiological age-related loss. No serious, vision-threatening, irreversible complication such as keratectasia or progressive endothelial cell loss was observed.

CONCLUSION

LASIK surgery is an effective and safe procedure for correcting myopia/myopic astigmatism as long as inclusion and exclusion criteria are strictly respected. However, minimal regression occurred during the 5-year investigative period.

LASIK Flap Characteristics Using the Moria M2 Microkeratome With the 90-µm Single Use Head

PURPOSE

To evaluate the accuracy and consistency of corneal flap thickness, horizontal diameter, and hinge size with the Moria M2 90-microm single use head.

METHODS

Fifty-two myopic patients (104 eyes), mean age 32.6 years, underwent bilateral LASIK with a superior hinged flap using the Moria M2 microkeratome (90-microm single use head). Prospective evaluation included flap thickness (subtraction method), diameter, hinge size, interface particles, intraoperative complications, and visual recovery.

RESULTS

The mean preoperative spherical equivalent refraction was -5.72 +/- 2.59 diopters (D) (range: -2.88 to -10.75 D) and -5.84 +/- 2.73 D (range: -3.13 to -9.38 D) for right and left eyes, respectively. The mean preoperative central corneal thickness was 548 +/- 24 microm and 547 +/- 25 microm for right and left eyes, respectively. The mean preoperative steepest K was 44.12 +/- 1.28 D and 44.41 +/- 1.27 D for right and left eyes, respectively. Corneal diameter (white-to-white) was 12 +/- 0.4 mm and 11.9 +/- 0.4 mm for right and left eyes, respectively. The mean postoperative flap thickness was 109 +/- 18 microm (range: 67 to 152 microm) and 103 +/- 15 microm (range: 65 to 151 microm) for right and left eyes, respectively. The mean postoperative flap diameter was 9.4 +/- 0.3 mm (expected mean according to the nomogram given by the company was 9.5 mm). The mean postoperative hinge chord was 4.4 +/- 0.4 mm (expected mean 4.2 mm). No interface particles were detected on slit-lamp examination.

CONCLUSIONS

The Moria M2 90-microm single use head is safe with reasonable predictability for LASIK flap creation.

Risk factors and retreatment results of intraoperative flap complications in LASIK

PURPOSE

To evaluate the incidence, type, and risk factors of intraoperative complications leading to abandonment of laser in situ keratomileusis (LASIK), and to compare the safety and efficacy of retreated LASIK with uncomplicated primary LASIK.

SETTING

Refractive surgery centers in Tokyo, Yokohama, Nagoya, Osaka, and Fukuoka, Japan.

METHODS

A total of 3751 eyes of 2033 patients who were followed for 6 months after primary LASIK, of which 15 eyes were retreated after intraoperative flap complications, were reviewed. In most of the cases, retreatments were performed by recutting a new flap.

RESULTS

Intraoperative flap complications occurred in 25 eyes, of which 15 eyes had retreatment at a later date. The overall incidence of complications was independent of the surgeons' experience, although incomplete flaps, in particular, occurred at a higher rate in the hands of inexperienced surgeons. No patient profile was detected as a risk factor for intraoperative flap complications. No flap-related complications occurred at retreatment. Refractive and visual outcomes were comparable to those in the uncomplicated cases within 6 months postoperatively.

CONCLUSIONS

Retreatment after microkeratome flap complications by recutting the cornea is safe and effective.

Outcome of second surgery in LASIK cases aborted due to flap complications

PURPOSE

To describe the technique and timing of second refractive surgery after aborted laser in situ keratomileusis (LASIK) due to intraoperative flap complication and determine the final visual outcome.

SETTING

Outpatient ambulatory laser vision correction centers.

METHODS

This retrospective noncomparative case series included 16 patients (16 eyes) who had a second refractive surgery after initial LASIK surgery was aborted because of a flap complication. Charts were reviewed with attention to initial preoperative data, intraoperative details of the aborted LASIK, postoperative examination, possible causes of the flap complication, timing and technique of second refractive surgery, and final visual outcome.

RESULTS

Causes of the aborted LASIK were identified in 13 of 16 eyes (81.2%) and included eye squeezing (5 eyes), loss of suction or machine failure (5 eyes), steep corneas (2 eyes), and learning curve of the surgeon (1 eye). The mean time until the second surgery was 135 days (range 49 to 372 days). Repeat flaps were created deeper and larger than the initially attempted flaps when possible. No patient had a final uncorrected visual acuity (UCVA) worse than 20/30 after the second surgery. Two eyes (12.5%) lost 1 line of best spectacle-corrected visual acuity.

CONCLUSION

A planned delayed reoperation after sufficient corneal healing following an intraoperative flap complication can result in satisfactory recovery of UCVA.