Purpose: To determine the prevalence of relative anterior microphthalmos (RAM) and evaluate intraoperative performance and surgical outcome in eyes with RAM undergoing cataract surgery. Design: Nested case-control series. Participants: One thousand four hundred consecutive patients undergoing cataract surgery were evaluated to determine the prevalence of RAM. Relative anterior microphthalmos is defined as horizontal corneal diameter (HCD) ≤ 11 mm, anterior chamber depth (ACD) ≤ 2.2 mm, and axial length (AL)>20 mm, with no other morphologic malformation. Methods: Patients were examined preoperatively for HCD, ACD, and AL. Horizontal corneal diameter was measured with calipers. Anterior chamber depth and AL were measured with immersion shell with water. Associated ocular pathologic conditionswere recorded. Two control groupswere identified. Group I (normal eyes; n=84) had HCD >11 mm, ACD >2.2 mm, and AL >20 mm. Group II (eyes with small corneal diameter; n=84) had HCD ≤ 11 mm, ACD >2.2 mm, and AL >20 mm. Main Outcome Measures: Patients with RAM and controls were evaluated for intraoperative performance and postoperative outcome. The 2- tailed Fisher exact test was applied to compare the performance of RAM with each of the control groups. The odds ratio (OR) with 95% confidence intervals (95% CI) was determined. Results: The prevalence of RAM was 6% (84 of 1400 eyes; 95% CI, 0.048- 0.074). Relative anterior microphthalmos was associated with the presence of small pupil, 34 (40.48% ); corneal guttae, 31(36.9% ); glaucoma, 29(34.5% ); and pseudoexfoliation, 6(7.14% ). Intraoperatively, RAM was associated with overall surgical difficulty because of less working space in 59 eyes (70.24% ; OR, 63.7; 95% CI, 18.3- 221; P < 0.001) compared with control groups I and II; uveal trauma in 12(14.28% ); Descemet’s detachment in 5 (5.95% ); and posterior capsule rupture in 2 (2.38% ). Postoperatively, RAM was associated with transient corneal edema in 63 eyes (75% ; OR, 9.0; 95% CI, 4.4- 18.0; P < 0.001; OR, 5.4; 95% CI, 2.7- 10.5; P < 0.001) on the first postoperative day. Conclusions: The prevalence of RAM was 6% . Relative anterior microphthalmos with its associations posed significant intraoperative difficulties. The occurrence of transient corneal edema was frequent. Purpose: To determine the prevalence of relative anterior microphthalm (RAM) and evaluate intraoperative performance and surgical outcome in eyes with RAM undergoing cataract surgery. Design: Nested case-control series. Participants: One thousand four hundred consecutive patients undergoing cataract surgery were were to determine the prevalence of RAM. Relative anterior microphthalmos is defined as horizontal corneal diameter (HCD) ≤ 11 mm, anterior chamber depth (ACD) ≤ 2.2 mm, and axial length (AL)> 20 mm, with no other morphologic malformation. Methods: Patients were examined preoperatively for HCD, ACD, and AL. Horizontal corneal diameter was measured with calipers. Anterior chamber depth and AL were measured with immersion shell with water. Associated ocular pathologic conditionswere recorded. Two control groups identified. Group I (normal eyes; had HCD> 11 mm, ACD> 2.2 mm, and AL> 20 mm. Group II (eyes with small corneal diameter; n = 84) > 2.2 mm, and AL> 20 mm. Main Outcome Measures: Patients with RAM and controls were evaluated as intraoperative performance and postoperative outcomes. The 2-tailed Fisher exact test was applied to compare the performance of RAM with each of the control groups. The prevalence of RAM was 6% (84 of 1400 eyes; 95% CI, 0.048- 0.074). Relative anterior microphthalmos was associated with the Presence of small pupil 34 (40.48%); corneal guttae 31 (36.9%); glaucoma 29 (34.5%); and pseudoexfoliation 6 (7.14%). Intraoperatively, RAM was associated with overall surgical difficulty due to less working compared with control groups I and II; uveal trauma in 12 (14.28%); Descemet’s detachment in 5 (5.95%); and posterior capsule rupture in 2 (2.38%). Postoperatively, RAM was associated with transient corneal edema in 63 eyes (75%; OR, 9.0; 9 5% CI,P <0.001; OR, 5.4; 95% CI, 2.7-10.5; P <0.001) on the first postoperative day. Conclusions: The prevalence of RAM was 6%. Relative anterior microphthalmos with its associations posed significant intraoperative difficulties The occurrence of transient corneal edema was frequent.