Image registration reveals central lens thickness minimally increases during accommodation

Ronald A Schachar,1 Majid Mani,2 Ira H Schachar31Department of Physics, University of Texas at Arlington, Arlington, TX, 2California Retina Associates, El Centro, 3Byers Eye Institute of Stanford University, Palo Alto, CA, USAPurpose: To evaluate anterior chamber depth, central crystalline lens thickness and lens curvature during accommodation.Setting: California Retina Associates, El Centro, CA, USA.Design: Healthy volunteer, prospective, clinical research swept-source optical coherence biometric image registration study of accommodation.Methods: Ten subjects (4 females and 6 males) with an average age of 22.5 years (range: 20–26 years) participated in the study. A 45° beam splitter attached to a Zeiss IOLMaster 700 (Carl Zeiss Meditec Inc., Jena, Germany) biometer enabled simultaneous imaging of the cornea, anterior chamber, entire central crystalline lens and fovea in the dilated right eyes of subjects before, and during focus on a target 11 cm from the cornea. Images with superimposable foveal images, obtained before and during accommodation, that met all of the predetermined alignment criteria were selected for comparison. This registration requirement assured that changes in anterior chamber depth and central lens thickness could be accurately and reliably measured. The lens radii of curvatures were measured with a pixel stick circle.Results: Images from only 3 of 10 subjects met the predetermined criteria for registration. Mean anterior chamber depth decreased, −67 µm (range: −0.40 to −110 µm), and mean central lens thickness increased, 117 µm (range: 100–130 µm). The lens surfaces steepened, anterior greater than posterior, while the lens, itself, did not move or shift its position as appeared from the lack of movement of the lens nucleus, during 7.8 diopters of accommodation, (range: 6.6–9.7 diopters).Conclusion: Image registration, with stable invariant references for image correspondence, reveals that during accommodation a large increase in lens surface curvatures is associated with only a small increase in central lens thickness and no change in lens position.Keywords: swept-source biometry, accommodation, anterior chamber depth, crystalline lens thickness, image registration, lens curvature