Anterior chamber depth estimation by Scheimpflug photography

Purpose: To obtain a model suitable for evaluation of the anterior chamber depth (ACD) maintaining capacity of viscoelastic substances - a critical parameter in cataract surgery. Methods: ACD was estimated using an anterior segment analysis system (EAS-1000, Nidek Co Ltd, Japan). Variation was studied as an effect of batch number and eye within batch, storage, globe fixation, globe position, and repeated analyses of Scheimpflug images. Results: Considerable variation in ACD was found between eyes, batches, and as a result of prolonged storage (biological factors). Different IOPs before surgery caused significant alterations in ACD after overfilling with a viscoelastic substance. No significant differences were found when the globe position was altered or when the ACD was re-estimated repeatedly from the same photograph. Conclusion: Differences due to biological factors are more important than methodological errors caused by the Scheimpflug instrument. To reduce these variations when viscoelastics are evaluated, all measurements should be calculated as % of ACD before surgery and the anterior chamber should be overfilled with a viscoelastic solution.