Purpose: To assess the occurrence and magnitude of corneal topographic changes in phakic eyes undergoing Transconjuctival Cannulated 20 gauge Vitrectomy (TC20V) without scleral buckling or silicone oil tamponade. Setting: Prospective randomized controlled study done at Egyptian Eye Academy. Methods: Forty eyes of 40 patients underwent TC20V for a variety of vitreo-retinal conditions over a 1 year follow-up period. Corneal keratometric readings were obtained using Oculus Pentacam before surgery, 1 week after, and 1 month after surgery; neither scleral buckling nor silicone oil tamponade were used in order to not affect the final corneal changes. Cases with postoperative hypotony were excluded. Results: The mean preoperative K1 (vertical keratometry) was 44.87 ± 3.55, the mean preoperative K2 (horizontal keratometry) was 44.57 ± 3.68; the mean postoperative K1 after 1 week was 45.1 ± 6.82 while the mean postoperative K2 after 1 week was 45.7 ± 3.97. Using paired t-test analysis, the P-value of the K1 change was 0.01 and P-value of the K2 change was 0.02. Both indicate minimally significant differences. One month postoperative the mean K1 was 45.2 ± 2.53 and the mean K2 was 45.1 ± 1.56 and P-values of both K1 and K2 changes after 1 month were .0.05, which indicates insignificant changes. Conclusion: The results showed that minimal corneal topographic changes were encountered with the use of TC20V owing to the tunnel configuration of the wound, and these changes also decrease within the first month.