OCT-based crystalline lens topography in accommodating eyes

Abstract

Custom Spectral Domain Optical Coherence Tomography (SD-OCT) provided with automatic quantification and distortion correction algorithms was used to measure anterior and posterior crystalline lens surface elevation in accommodating eyes and to evaluate relationships between anterior segment surfaces. Nine young eyes were measured at different accommodative demands. Anterior and posterior lens radii of curvature decreased at a rate of 0.78 ± 0.18 and 0.13 ± 0.07 mm/D, anterior chamber depth decreased at 0.04 ± 0.01 mm/D and lens thickness increased at 0.04 ± 0.01 mm/D with accommodation. Three-dimensional surface elevations were estimated by subtracting best fitting spheres. In the relaxed state, the spherical term accounted for most of the surface irregularity in the anterior lens (47%) and astigmatism (70%) in the posterior lens. However, in accommodated lenses astigmatism was the predominant surface irregularity (90%) in the anterior lens. The RMS of high-order irregularities of the posterior lens surface was statistically significantly higher than that of the anterior lens surface (x2.02, p<0.0001). There was significant negative correlation in vertical coma (Z3 (-1)) and oblique trefoil (Z3 (-3)) between lens surfaces. The astigmatic angle showed high degree of alignment between corneal surfaces, moderate between corneal and anterior lens surface (~27 deg), but differed by ~80 deg between the anterior and posterior lens surfaces (including relative anterior/posterior lens astigmatic angle shifts (10-20 deg).

Keywords: (100.2960) Image analysis; (110.4500) Optical coherence tomography; (110.6880) Three-dimensional image acquisition; (120.6650) Surface measurements, figure; (330.7322) Visual optics, accommodation; (330.7323) Visual optics, aging changes; (330.7327) Visual optics, ophthalmic instrumentation.

Fig. 1

Illustration of the acquisition of an individual data collection of three volume acquisitions and merging to obtain a 3-D full anterior segment volume.

Fig. 2

Illustration of the effect of distortion correction on the anterior segment surfaces in S#1 (OS). Left data: from optical paths, without distortion correction; right data: distortion correction.

Fig. 3

(a) Examples of 3-D images in S#2 (OD) relaxed (left) and for 6 D of accommodative demand (right). (b) Corneal (up) and crystalline lens (down), anterior (left) and posterior (right) surface elevation maps in S#2 (OD) relaxed accommodation. Data are for 4 mm.

Fig. 4

Anterior and posterior crystalline lens elevation surface maps in the unaccommodated state (maps exclude tilt, defocus and astigmatism).

Fig. 5

Anterior and posterior crystalline lens surface Zernike coefficient (plots include astigmatism and high-order terms; pupil diameter is 4-mm).

Fig. 6

(a) Cornea and crystalline lens surface elevation Zernike terms (astigmatism and high-order) in the relaxed state (average over all subjects). (b) Cornea and crystalline lens individual Zernike coefficients (high-order) in the relaxed state.

Fig. 7

Natural vs phenylephrine conditions in the anterior crystalline lens surface (Zernike coefficients) for all accommodative demands.

Fig. 8

Biometric and geometrical changes with accommodation: (a) Anterior Chamber Depth, (b) Lens Thickness, (c) Anterior Lens Radius and (d) Posterior Lens Radius (e) Accommodative response vs Accommodative demand in all subjects.

Fig. 9

( Visualization 1) Example of the anterior segment segmented surfaces (corneal and lens) with accommodation (left) and the corresponding lens surface elevation maps for different accommodative demands (right). Data are for subject S#2 (OS). Pupil diameter in maps is 4-mm.

Fig. 10

Average RMS of high-order irregularities, astigmatism, coma, trefoil and spherical for different accommodative demands. Data are for 4-mm pupils.

Fig. 11

Power vector polar plot of astigmatism in anterior and posterior crystalline lens surfaces, for different accommodative demands. Each panel represents a different eye. Red lines stand for anterior lens and blue lines for posterior lens astigmatism. Each line type represents a different accommodative demand. The angle represents the axis of astigmatism and the length of the vectors represents the magnitude of the corresponding surface astigmatism.

Fig. 12

Astigmatism surface magnitude in all eyes for different accommodative demands.