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Femtosecond LASIK with novel settings improves vision in eyes with previous RK
No cases of postoperative inflammation or corneal haze were reported, and no patients needed flap refloating or repositioning.
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LASIK with unique femtosecond laser flap creation settings improved vision with no serious complications in patients who had previously undergone radial keratotomy, according to a study.
The settings helped surgeons avoid intraoperative and postoperative complications in eyes that had undergone RK.
“The significant findings were that, using the techniques that we described in the study, we were able to successfully lift the flap without causing the RK incisions to come undone, which is a well-described complication. What’s novel about the study is not that femtosecond lasers are being used for this purpose but the actual settings that are used. That’s what’s novel,” corresponding author Ryan B. Rush, MD, told Ocular Surgery News. “The femtosecond laser technique described in our paper can successfully provide LASIK with good outcomes and minimal complications in patients who have had previous RK.”
Rush said there are risks in performing femtosecond laser flap creation on eyes with previous RK.
“You can get opening of the RK incisions and loss of suction, neither of which were found in any of the patients during our study. Postoperatively, you can get interface inflammation and corneal haze, which can ultimately lead to loss of best corrected visual acuity. We did not have any subjects in our study who had that,” he said.
Patients and parameters
The retrospective study, published in the Asia-Pacific Journal of Ophthalmology, included 16 eyes of eight subjects who underwent femtosecond laser-assisted LASIK for consecutive hyperopia after previous RK. Mean patient age was 51.8 years.
Femtosecond laser flap creation was performed with the WaveLight FS200 femtosecond laser platform (Alcon). Ablation was performed with the Allegretto Wave Eye-Q 400 Hz excimer laser (Alcon).
Laser settings for flap creation were bed cut energy of 1.4 µJ, bed cut spot separation of 6 µm, bed cut line separation of 6 µm, side cut energy of 0.8 µJ, side cut spot separation of 5 µm and side cut line separation of 3 µm.
All flaps were 9 mm in diameter and were cut with a 70° side cut angle. Flap length varied according to preoperative OCT measurements of central corneal thickness and central epithelial thickness. Target flap depth was at least 100 µm thicker than the central epithelial thickness but thinner than that required to leave a residual stromal bed of at least 350 µm.
“I’m quite certain that if a different femtosecond laser was used that the settings would not be exactly the same as what was described in the paper,” Rush said. “[Settings] will vary if you use a different platform. This is only going to be effective for using this specific femtosecond [laser], but it is an extremely common one used, especially in the United States.”
Uncorrected and best corrected visual acuity and refractive parameters were measured 2 weeks, 2 months, 4 to 6 months, and 9 to 12 months after surgery. Mean follow-up was 318.1 days.
Results
UCVA significantly improved at 2 months (P = .0033), 4 to 6 months (P = .0120) and 9 to 12 months (P = .0142). Average logMAR UCVA was 0.13 at 9 to 12 months.
No significant refractive shifts or regression of more than 1 D were observed through follow-up. No eyes lost one or more lines of BCVA at final follow-up.
Average postoperative spherical equivalent was 0.23 D.
Mean intended flap depth was 192 µm. Intraoperative measurements showed that flaps were 11.9 µm thinner than expected, but the deviation from the targeted depth was not statistically significant.
No significant intraoperative or postoperative complications were reported, and no patients required postoperative refloating or repositioning of flaps.
Weaknesses of the study were its retrospective design, lack of a control group, small number of patients and relatively brief follow-up, the authors said. – by Matt Hasson
- Reference:
- Rush SW, et al. Asia Pac J Ophthalmol. 2015;doi:10.1097/APO.0000000000000131.
- For more information:
- Ryan B. Rush, MD, can be reached at Panhandle Eye Group, 7400 Fleming Ave., Amarillo, TX 79106; email: ryanbradfordrush21@hotmail.com.
Disclosure: Rush reports no relevant financial disclosures.