Myopia is associated with increased axial length and a prolate shape. This prolate shape is consistent with the proposed idea that axial and transverse dimensions of the eye are regulated differently. The observations that ocular shape changes are larger but more symmetrical in Chinese eyes than in eyes of whites warrant further investigation.

Statistical analysis of data can be complex and different statisticians may disagree as to the correct approach leading to conflict between authors, editors, and reviewers.

During accommodation, mean crystalline lens thickness increased (F = 33.39, P < 0.001), whereas lens equatorial diameter (F = 24.00, P < 0.001) and surface radii both decreased (anterior surface, F = 21.78, P < 0.001; posterior surface, F = 13.81, P < 0.001). Over the same stimulus range, mean crystalline lens surface area decreased (F = 7.04, P < 0.005) with a corresponding increase in lens volume (F = 6.06, P = 0.005). These biometric changes represent a 1.82% decrease and 2.30% increase in crystalline lens surface area and volume, respectively. CONCLUSIONS; The results indicate that the capsular bag undergoes elastic deformation during accommodation, causing reduced surface area, and the observed volumetric changes oppose the theory that the lens is incompressible.

Measurements (autokeratometry, A-scan ultrasonography and video ophthalmophakometry) of ocular surface radii, axial separations and alignment were made in the horizontal meridian of nine emmetropes (aged 20-38 years) with relaxed (cycloplegia) and active accommodation (mean +/- 95% confidence interval: 3.7 +/- 1.1 D). The anterior chamber depth (-1.5 +/- 0.3 D) and both crystalline lens surfaces (front 3.1 +/- 0.8 D; rear 2.1 +/- 0.6 D) contributed to dioptric vergence changes that accompany accommodation. Accommodation did not alter ocular surface alignment. Ocular misalignment in relaxed eyes is mainly because of eye rotation (5.7 +/- 1.6 degrees temporally) with small amounts of lens tilt (0.2 +/- 0.8 degrees temporally) and decentration (0.1 +/- 0.1 mm nasally) but these results must be viewed with caution as we did not account for corneal asymmetry. Comparison of calculated and empirically derived coefficients (upon which ocular surface alignment calculations depend) revealed that negligible inherent errors arose from neglect of ocular surface asphericity, lens gradient refractive index properties, surface astigmatism, effects of pupil size and centration, assumed eye rotation axis position and use of linear equations for analysing Purkinje image shifts.

Ophthalmophakometric measurements of ocular surface radius of curvature and alignment were evaluated on physical model eyes encompassing a wide range of human ocular dimensions. The results indicated that defocus errors arising from imperfections in the ophthalmophakometer camera telecentricity and light source collimation were smaller than experimental errors. Reasonable estimates emerged for anterior lens surface radius of curvature (accuracy: 0.02-0.10 mm; precision 0.05-0.09 mm), posterior lens surface radius of curvature (accuracy: 0.10-0.55 mm; precision 0.06-0.20 mm), eye rotation (accuracy: 0.00-0.32 degrees; precision 0.06-0.25 degrees), lens tilt (accuracy: 0.00-0.33 degrees; precision 0.05-0.98 degrees) and lens decentration (accuracy: 0.00-0.07 mm; precision 0.00-0.07 mm).