Ocular axial length in homocystinuria patients with and without ocular changes: Effects of early treatment and biochemical control

Purpose: To establish whether myopia in homocystinuria could be due to increased ocular axial length. Methods. Measurement of ocular axial length by A-scan ultrasound in eyes of homocystinuria patients. Results. Patients were divided into three groups. Group 1, with no ocular pathology (28 eyes), had mean refractive error of -0.25 D (spherical equivalent) and mean axial length of 23.4 mm +/-0.9 ( +/-11 standard deviation) mm. Group 11, with phacodonesis or lens subluxation (12 eyes), had mean refractive error of -10.7 D and mean axial length of 23.8 mm +/-1.9 mm. Patients with phacodonesis had simple myopia whereas those with lens subluxation had marked myopic astigmatism. Group III included patients with complete lens dislocation in at least one eye (12 eyes) and were optically aphakic with a mean refractive error of +/-12.9 D and mean axial length of 24.9 mm +/- 0.9 mm. All Group I patients had good long-term metabolic control while those in Groups 11 and III did not. Group III eyes had significantly longer mean axial length than Group I (P = .0018) or normal eyes (P = .0163). There was no statistical difference in mean axial length between Group I and normal eyes. Conclusions: Ocular axial length is significantly increased in individuals with homocystinuria and lens dislocation. Increased axial length is a complication that has not been previously described in homocystinuria and may be preventable with early treatment and good biochemical control.