Background: Diabetic macular edema (DME) is a leading cause of vision impairment among individuals with diabetic retinopathy, primarily attributed to changes in the central macular thickness (CMT). This study aims to evaluate the impact of CMT changes on best corrected visual acuity (BCVA) in patients with DME. Materials and Methods: This descriptive observational study was conducted at the Department of Anatomy along with Dept. of Ophthalmology, S.M.S Hospital and Medical College, Jaipur, with a sample size of 100 eyes from treatment-naive patients with DME. The study utilized Spectral Domain Optical Coherence Tomography (SD-OCT) for measuring CMT and assessing the integrity of the outer retinal layer at the fovea. BCVA was evaluated using standard ophthalmic procedures. Statistical analyses were performed using Epi info version 7.2.1.0, with p ≤ 0.05 considered statistically significant. Results: The study found a statistically significant correlation between increased CMT and decreased BCVA. The average CMT was 226.40 μm with a standard deviation of 22.5063 μm. Changes in the CMT were significantly associated with variations in BCVA, highlighting the direct impact of macular edema on visual acuity. Conclusion: The findings suggest that changes in the central macular thickness directly affect the best corrected visual acuity in patients with diabetic macular edema. Prompt detection and appropriate management of DME are crucial in preserving visual function and preventing vision loss.