#Pixelstick images low registration

The Zeiss IOLMaster 700 (Carl Zeiss Meditec Inc.) was used for image acquisition. None were using any medications, supplements nor any recreational drugs that would affect accommodation. Each had best corrected visual acuity of 20/20 and a mean spherical equivalent refraction of −1.01 diopters (range: 0.125 to −4.50 diopters). This study complied with the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of the California Retina Associates.Īll subjects had normal ocular examinations. All subjects agreed to participate and executed an informed consent. They were healthy ophthalmic technicians from the staff of California Retina Associates. Ten subjects (4 females and 6 males) with an average age of 22.5 years (range: 20–26 years) participated in this prospective cohort study. 25 Since both the location of the pupil and shape of the iris change with accommodation, even during phenylephrine dilation, 26– 32 reliance on these unstable references ensured that compared images were not properly registered.

A recent study of accommodative lens changes used the location of the pupil and the shape of the iris to determine image correspondence for image registration. 1– 3 In contrast, the Schachar mechanism 4 states that during accommodation, the equatorial zonules increase in tension causing peripheral lens flattening and a small increase in central lens thickness (20 mm to measure the changes in central lens thickness during accommodation. The Helmholtz theory hypothesizes that during accommodation, the zonules relax causing the lens to round up with a large increase in central lens thickness (>35 μm/diopter of accommodation) and anterior movement of the lens.

Despite over 150 years of research, 2 theories remain. Keywords: swept-source biometry, accommodation, anterior chamber depth, crystalline lens thickness, image registration, lens curvatureĬontinued disagreement exists as to the fundamental mechanism of accommodation in humans. 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).Ĭonclusion: 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. 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). Results: Images from only 3 of 10 subjects met the predetermined criteria for registration. The lens radii of curvatures were measured with a pixel stick circle.

#Pixelstick images low registration

This registration requirement assured that changes in anterior chamber depth and central lens thickness could be accurately and reliably measured. Images with superimposable foveal images, obtained before and during accommodation, that met all of the predetermined alignment criteria were selected for comparison. 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. Methods: Ten subjects (4 females and 6 males) with an average age of 22.5 years (range: 20–26 years) participated in the study. Setting: California Retina Associates, El Centro, CA, USA.ĭesign: Healthy volunteer, prospective, clinical research swept-source optical coherence biometric image registration study of accommodation. Purpose: To evaluate anterior chamber depth, central crystalline lens thickness and lens curvature during accommodation. Ronald A Schachar, 1 Majid Mani, 2 Ira H Schachar 3ġDepartment of Physics, University of Texas at Arlington, Arlington, TX, 2California Retina Associates, El Centro, 3Byers Eye Institute of Stanford University, Palo Alto, CA, USA