Introduction. Despite the achievements of modern pharmacology and laser surgery, traditional glaucoma surgery remains the main method of reducing intraocular pressure (IOP). After successful glaucoma surgery, some of the patients are observed to have a decrease in visual functions not associated with progression of the glaucomatous process. This phenomenon is explained by the effect glaucoma surgery can have on eye refraction; detailed understanding of such changes would significantly speed up functional rehabilitation of these patients. Purpose — to study the time course of clinical manifestations of aberrations of the ocular optical system in the surgical treatment of glaucoma and to assess the effectiveness of the method used to minimize them. Material and methods. The study included 32 patients (32 eyes), aged from 52 to 73 years. The patients were divided into 2 groups. Patients of the first group (20 eyes) were treated with standard non-penetrating deep sclerectomy (NPDS). In the second group (12 eyes), patients underwent a modified NPDS according to an original method proposed by us. All patients were examined before and monitored after the surgery including precision visometry and corneal topography. Results. A significant change in the studied parameters was observed in the first group in the early postoperative period (3rd day) — the average value of corneal astigmatism increased from 0.83±0.12 D to 2.86±0.07 D, while in the second group it increased from 0.86±0.20 D to 1.36±0.12 D. Conclusion. Non-penetrating deep sclerectomy according to the modified method proposed by us helps achieve higher functional results in the early postoperative period due to the reduction of induced changes in eye refraction.