Bowman’S Layer Stromal Transplantation In Advanced Keratoconus: Five-Year Clinical Outcomes In 54 Eyes

To evaluate the long-term clinical and topographic outcomes of Bowman’s layer stromal transplantation (BLST) in advanced keratoconus cases unsuitable for corneal cross-linking due to advanced thinning.

Single-center tertiary cornea referral practice.

This prospective interventional case series included 54 eyes with advanced keratoconus and preoperative pachymetry between 250–350 µm, deemed unsuitable for corneal cross-linking. A donor Bowman’s layer graft with approximately 100 µm of anterior stroma was transplanted into a manually created mid-stromal pocket.

The stromal pocket was fashioned using guarded-depth keratomes and lamellar dissectors at an intended implant depth of approximately 150 µm, with an average graft diameter of 7.0–7.5 mm.

Primary outcomes included change in Kmax, pachymetry, higher-order aberrations (HOA), and best-corrected visual acuity (BCVA). Patients were followed for 5 years.

At 3 months postoperatively:

• Kmax reduction: 2–6 diopters (mean reduction approximately 3.8 ± 1.2 D)

• Corneal thickness increase: 80–100 µm centrally

• Higher-order aberrations: Reduced by 40–60%

Visual outcomes:

• BCVA improved to 6/12 in 42 eyes (77.8%)

• BCVA improved to 6/9 with contact lens correction in 12 eyes (22.2%)

At 5-year follow-up:

• Stabilization achieved in 100% of cases

• No cases required keratoplasty

• No intraoperative perforations or sight-threatening complications were noted

Bowman’s layer stromal transplantation using a manually dissected mid-stromal pocket with a 100 µm anterior stromal augmentation provides significant corneal flattening, thickness augmentation, HOA reduction, and sustained stabilization in advanced keratoconus unsuitable for CXL.

This technique may serve as an effective keratoplasty-delaying strategy in severely thinned corneas, offering structural reinforcement and long-term biomechanical stability.