Material and Methods: The study included 56 eyes of 56 healthy volunteers aged ?18 years in group 1, 35 eyes of 35 healthy volunteers aged 18-40 years in group 2 and 72 eyes of 72 healthy volunteers aged >40 years in group 3. Topical cyclopentolate hydrochloride 1 % was applied to all volunteers. The biometric measurements were performed by Lenstar LS900 before and after cycloplegia.

Results: The mean age was 12.1±3.6 years (5-17 years) in group 1; 24.6±3.9 years (20-35 years) in group 2; and 56.1±8.8 years (40-73 years) in group 3. Signifi cant differences were detected in lens thickness and anterior chamber depth in all groups after cycloplegia (p< 0.01). There were signifi cant differences in IOL power calculated using Olsen formula before and after cycloplegia: 0.13±0.33 D (-0.5 - 1.0 D) in group 1 and 0.21±0.32 D (-0.5 - 1.0 D) in group 2 (p< 0.01).

Conclusion: There was no signifi cant difference IOL power calculated using Hoffer Q, Haigis, Holladay 1, Barrett and SRK-T formulas in all groups while there was signifi cant difference in IOL power calculated using Olsen formula in subjects under 40 years old. Keywords : Biometry, Cycloplegia, IOL power