Femtosecond Laser In Implantation Of Intracorneal Rings Segments

The purpose of this study is to analyze the topographic, refractive and aberrometric effect, as well as the complications secondary to surgery during the follow-up of patients who have had a surgical intervention with intrastromal rings segment by femtosecond laser.

Follow-up was carried out at 24 hours, 1 month, 3 months and 6 months of a total of 74 patients with surgical implantation of intrastromal rings segment in 2022 assisted by femtosecond laser in a Spanish public health hospital as part of the treatment for keratoconus.

An epidemiological study is carried out based on general characteristics of the patient such as the patient's age, sex and laterality, comparing the number of rings implanted, the optical zone, the arc length, whether they are symmetrical or asymmetrical, and the thickness of the ring, relating them to the grade and topographic phenotype of each case.

We also analyze the characteristics and parameters used of the femtosecond laser, as well as the axis of the incision, the positioning axis of the ring and the planned depth of the implant.

Corneal topographies are performed before and after the intervention in order to compare Km, astigmatism and high order aberrations (spherical aberration and coma) before and after surgery.

The mean age was 35 years. 59.5% (n=44) were male. 52.7% (n=39) right eyes.

64.9% (n=48) were a single implant. Only 10.8% (n=8) were progressive rings. 52.7% (n=39) of the rings had a 5 mm optical zone, while 47.3% (n=35) 6 mm. 2 had an arc of 120º, 11 of 140º, 21 of 150º, 26 of 160º and 11 of 210º. According to the thickness, 3 had a thickness of 150 mc, 23 of 200 mc, 29 of 250 mc and 9 of 300 mc. Finally, the mean tunnel depth was 373 mc with a standard deviation of 24.5 mc.

The global results were an average reduction of 2.36 Km, 1.13 astigmatism and 0.770 coma. In the analysis by phenotype and grade, a greater effect on astigmatism is observed in symmetrical implants, while the reduction of coma is greater in asymmetrical implants.

The introduction of the femtosecond laser as the gold standard for the implantation of intracorneal segments has meant a great advance in the hospital environment, which has made it possible to considerably reduce surgical time, thus allowing to double the number of patients who undergo surgery in the same operating room session. In addition, in our experience it offers similar or better results than the manual corneal ring implantation technique, without increasing the rate of surgical complications and reducing some such as epithelial alterations and shortening the recovery time of patients, which has allowed us to reduce the number of postoperative reviews.