From Ectasia To Regularization: Early Outcomes Of Femtosecond Laser–Assisted Annular Keratectomy In Advanced Keratoconus

To describe the surgical technique, early clinical and tomographic outcomes, and selection criteria for femtosecond laser–assisted annular keratectomy in two young patients with Grade IV nipple type keratoconus intolerant to rigid gas-permeable lenses and inadequately corrected with spectacles.

Advanced keratoconus remains challenging in young patients unsuitable for conservative optical management who seek to delay or avoid corneal transplantation. Annular keratectomy redistributes corneal biomechanics by removing a mid-peripheral stromal ring, inducing flattening and partial regularization of the ectatic cornea. We report two cases demonstrating early visual and tomographic changes and discuss key aspects of patient selection.

Retrospective interventional case report conducted at a tertiary corneal referral center. Both patients underwent full ophthalmic evaluation including UDVA, CDVA, pinhole, manifest refraction, and Scheimpflug tomography. Femtosecond laser–assisted annular keratectomy was performed, creating a customized mid-peripheral stromal ring to induce controlled flattening and corneal regularization. Follow-up at 24 hours included slit-lamp exam, repeat tomography, and visual assessment.

Case 1
A 25-year-old female with Grade IV keratoconus, RGP intolerance, and poor spectacle correction presented with counting fingers (CF) at 50 cm, improving to 20/100 with pinhole. Tomography showed advanced ectasia: K1 61.93 D, K2 64.21 D, Km 63.05 D, cylinder −2.28 D @151°, Q +0.84, and vertical coma 1.62 µm.

Femtosecond laser–assisted annular keratectomy was performed uneventfully. At 24 hours, vision improved to CF at 3 m (20/100 with pinhole). Tomography revealed marked flattening: K1 27.09 D, K2 35.82 D, Km 30.85 D, cylinder −8.74 D, Q −1.56. Coma decreased to 0.98 µm. The patient reported improved clarity and reduced distortion.

Case 2
A 25-year-old male with Grade IV keratoconus and RGP intolerance had CF at 3 m without pinhole improvement. Preoperative tomography showed severe steepening (K1 69.43 D, K2 71.24 D, Km 70.32 D).

After the same procedure, uncorrected vision improved to 20/150 (20/100 with pinhole) at 24 hours. Tomography demonstrated significant flattening (K1 23.18 D, K2 41.30 D, Km 29.69 D) with 18.3 D cylinder in the central 3 mm.

In both cases, substantial early corneal flattening and functional visual improvement were observed. Benefit appears related to biomechanical redistribution and partial optical regularization rather than refractive correction alone.

Femtosecond laser–assisted annular keratectomy may be an alternative for selected patients with advanced nipple-type keratoconus intolerant to RGP lenses and poorly corrected with spectacles. In these cases, it achieved early corneal flattening, reduced higher-order aberrations (notably coma), and meaningful visual improvement within 24 hours. Despite residual irregular astigmatism, subjective quality improved, supporting a biomechanical effect. Careful selection is essential, particularly in advanced nipple phenotype patients seeking to delay or avoid keratoplasty.