Do Biometric Readings Change Significantly over Time in Phakic Eyes? A Cohort Study

Background: Precise biometric assessment is crucial in achieving desirable refractive outcomes following cataract surgery. The current evidence for longitudinal biometric changes is lacking. We have performed a cohort study of phakic patients undergoing cataract surgery to help demonstrate whether biometric parameters change over time. Methods: We performed a single-centre, historic cohort study of patients who attended a "two-stop" pre-assessment clinic for consideration of cataract surgery between November 2002 and March 2015. Data were collected retrospectively. Four biometric measurements were recorded: axial length, horizontal (K1) readings, vertical (K2) readings and dioptric power of lens (AR40). Patients were allocated to three groups according to the time interval between initial and latest biometric assessment: Group 1: up to 12 months; Group 2: 12-24 months; Group 3: over 24 months. Results: Data were obtained for 109 eyes from 62 patients. Mean patient age at first biometry was 78 (range: 49-95; S.D.:10). Thirty-eight patients (61.3%) were female. Paired t-tests were performed per biometric measurement per group. No statistically significant changes were observed in Group 1 (n = 9). In Group 2, a statistically significant change was observed in K1 readings (median change: -0.12 mm, range: -0.65 mm to 0.64 mm; P = .002). In Group 3, statistically significant changes were observed in K1 readings (median change: 0.06 mm, range: -0.59 mm to 1.29 mm, P = .03), K2 readings: (median change: 0.33 mm, range: -0.50 mm to 1.09 mm, P < .001) and no change in AR40 readings (median change: 0.00, range -2.00 to 3.00, P = .02). Conclusion: Statistically significant biometric changes were observed over time in this cohort. We recommend considering repeat biometric assessment in patients who have had an interval of longer than 24 months between initial biometric assessment and surgery for optimal refractive outcomes. Further research is required to identify more precisely when to expect changes in the various biometric parameters and which patient characteristics may contribute.