Glaucoma filtration surgeries remain the cornerstone of management for patients with primary open-angle glaucoma (POAG) who exhibit inadequate intraocular pressure (IOP) control despite maximal medical therapy. Among the commonly performed procedures, sub-scleral trabeculectomy (SST) and non-penetrating deep sclerectomy (NPDS) are widely utilized for their proven efficacy in lowering IOP. However, beyond IOP reduction, these surgical interventions may induce structural and biomechanical alterations in the cornea due to scleral flap creation, tissue manipulation, suturing techniques, and postoperative wound healing responses. Such changes can influence corneal curvature and induce surgically related astigmatism, thereby affecting visual quality and refractive stability in the postoperative period. Despite the clinical importance of these refractive alterations, the magnitude and pattern of corneal topographic changes following different glaucoma surgical techniques remain incompletely understood. A clearer understanding of these changes is essential to optimize surgical planning, improve postoperative visual outcomes, and provide accurate patient counseling : The present study aimed to evaluate and compare corneal topographic changes following sub-scleral trabeculectomy (SST) and non-penetrating deep sclerectomy (NPDS) in patients diagnosed with primary open-angle glaucoma (POAG). Specifically, the study sought to quantify surgically induced alterations in keratometric parameters and corneal astigmatism using computerized corneal topography, and to determine whether one surgical technique results in greater refractive impact than the other.This prospective comparative study enrolled 30 eyes of 30 patients diagnosed with primary open-angle glaucoma. Participants were equally allocated into two groups according to the surgical technique performed. Group A comprised patients who underwent sub-scleral trabeculectomy (SST) with intraoperative application of Mitomycin C (MMC) at a concentration of 0.2 mg/ml for 2 minutes. Group B included patients who underwent non-penetrating deep sclerectomy (NPDS), also with intraoperative application of MMC at a concentration of 0.2 mg/ml for 2 minutes. All patients underwent a comprehensive preoperative ophthalmic evaluation, including measurement of best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure assessment, gonioscopy, and fundus examination. Computerized corneal topography was performed preoperatively and repeated at 3 months postoperatively to assess corneal curvature changes. The primary outcome measures included changes in keratometric parameters: flat keratometry (K1), steep keratometry (K2), average keratometry (Avg K), corneal astigmatism (magnitude and axis), and apical keratometry front (AKf). Surgically induced changes were calculated by subtracting preoperative values from postoperative measurements. The collected data were statistically analyzed to compare topographic changes between the two surgical groups. The study was conducted at the Ophthalmology Department of Mother Theresa University Hospital Center between April 2025 and November 2025. A highly statistically significant increase (p < 0.001) was observed in keratometric changes in Group A (SST) compared with Group B (NPDS). Specifically, the mean change in flat keratometry (ΔK1) was 0.47 ± 0.09 D in Group A versus 0.22 ± 0.09 D in Group B. Similarly, the mean change in steep keratometry (ΔK2) was 0.86 ± 0.18 D in Group A compared to 0.46 ± 0.08 D in Group B. Surgically induced corneal astigmatism was also significantly greater in Group A (1.32 ± 0.13 D) than in Group B (0.69 ± 0.10 D). In contrast, no statistically significant differences were detected between the two groups with respect to changes in average keratometry (ΔAvg K) or apical keratometry front (ΔAKf), indicating comparable overall corneal curvature stability in these parameters. Glaucoma filtration surgery is associated with measurable corneal topographic alterations that may influence postoperative refractive outcomes. Surgically induced astigmatism appears to contribute to reduced unaided visual acuity during the early postoperative period. Sub-scleral trabeculectomy demonstrated a significantly greater impact on corneal astigmatism compared to non-penetrating deep sclerectomy. These findings suggest that NPDS may offer a relative refractive advantage in terms of minimizing surgically induced astigmatism.
Keywords: corneal topography, deep sclerectomy, primary open-angle glaucoma, surgically induced astigmatism, trabeculectomy
