The contribution of the posterior surface to the coma aberration of the human cornea

Dubbelman, M.; Sicam, Victor Arni D. P.; Heijde, Rob G.L. van der

doi:10.1167/7.7.10

Cited by 49 publications

(52 citation statements)

References 24 publications

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“…In agreement with prior work by Dubbelman et al [45,46] we found that on average the posterior corneal surface compensated part of the irregularities of the anterior cornea, in particular astigmatism (31% [45] / 18% in the current study) and coma (from 3.5% [46] / 12% in the current study). As in the cornea, our study also revealed a high correlation between the magnitude of the irregularities of the anterior and posterior lens surfaces in coma and trefoil terms, indicating coordinated development.…”

Section: Discussionsupporting

confidence: 94%

OCT-based crystalline lens topography in accommodating eyes

Pérez-Merino¹,

Velasco-Ocaña²,

Martinez-Enriquez³

et al. 2015

Biomed. Opt. Express

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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. Threedimensional 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 (Z 3 1 ) and oblique trefoil (Z 3 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).

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Section: Discussionsupporting

confidence: 94%

OCT-based crystalline lens topography in accommodating eyes

Pérez-Merino¹,

Velasco-Ocaña²,

Martinez-Enriquez³

et al. 2015

Biomed. Opt. Express

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“…Chen and Yoon 11 found mean compensations of 21% for astigmatism, 6% for coma, and 18% for spherical aberration. Yamaguchi et al 15 wrote that compensation for higher-order aberrations was approximately 10%, Dubbelman et al 12 found approximately 4% compensation for coma, and Sicam et al 13 reported variable compensation of 10% to À26% for spherical aberration. In our study, the mean compensations of the anterior cornea by the posterior cornea were approximately one-third for the major higherorder aberrations of horizontal astigmatism, horizontal coma, and spherical aberrations, and the RMS values of the posterior cornea were also approximately one-third of those of the anterior cornea.…”

Section: Discussionmentioning

confidence: 99%

“…Meanwhile, other studies have found much higher aberrations at the anterior surface than at the posterior surface using different instruments, including, the scanning slit Bausch & Lomb (Houston, TX, USA) Orbscan, 10,11 a laboratory Scheimpflug imager, 12,13 the Pentacam, 14 and anterior segment optical coherence tomography (SS-1000; Tomey, Nagoya, Japan). 15 These studies used different analyses including Fourier decomposition of the surfaces, 10 raytracing through surfaces, 12,13,15 and comparing the surface shapes with ideal (aberration-free) shapes. 11,14 A potential problem with the latter approaches arises if the object for the posterior cornea is set at infinity rather than that corresponding to refraction by the anterior cornea, as the choice of object position affects aberration estimates.…”

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confidence: 99%

Anterior Corneal, Posterior Corneal, and Lenticular Contributions to Ocular Aberrations

Atchison

Suheimat

Mathur

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. To determine the corneal surfaces and lens contributions to ocular aberrations.METHODS. There were 61 healthy participants with ages ranging from 20 to 55 years and refractions À8.25 diopters (D) to þ3.25 D. Anterior and posterior corneal topographies were obtained with an Oculus Pentacam, and ocular aberrations were obtained with an iTrace aberrometer. Raytracing through models of corneas provided total corneal and surface component aberrations for 5-mm-diameter pupils. Lenticular contributions were given as differences between ocular and corneal aberrations. Theoretical raytracing investigated influence of object distance on aberrations.RESULTS. Apart from defocus, the highest aberration coefficients were horizontal astigmatism, horizontal coma, and spherical aberration. Most correlations between lenticular and ocular parameters were positive and significant, with compensation of total corneal aberrations by lenticular aberrations for 5/12 coefficients. Anterior corneal aberrations were approximately three times higher than posterior corneal aberrations and usually had opposite signs. Corneal topographic centers were displaced from aberrometer pupil centers by 0.32 6 0.19 mm nasally and 0.02 6 0.16 mm inferiorly; disregarding corneal decentration relative to pupil center was significant for oblique astigmatism, horizontal coma, and horizontal trefoil. An object at infinity, rather than at the image in the anterior cornea, gave incorrect aberration estimates of the posterior cornea.CONCLUSIONS. Corneal and lenticular aberration magnitudes are similar, and aberrations of the anterior corneal surface are approximately three times those of the posterior surface. Corneal decentration relative to pupil center has significant effects on oblique astigmatism, horizontal coma, and horizontal trefoil. When estimating component aberrations, it is important to use correct object/image conjugates and heights at surfaces.

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“…139 Using Scheimpflug 3D-reconstruction and ray-tracing in normal eyes, Dubbelman et al found that the posterior cornea compensated for 3.5% of the anterior corneal coma aberration. 32 In a wavefront study of keratoconus eyes, Chen et al found that the posterior cornea compensated for 14-24% of the coma aberration of the anterior cornea. 24 Yamaguchi et al developed a surface parallelism index (SPI) to quantify changes in parallelism, 139 with a lower SPI indicating a greater degree of parallelism between the anterior and posterior corneal surfaces.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Determinants of visual quality after endothelial keratoplasty

Turnbull

Tsatsos

Hossain

et al. 2016

Survey of Ophthalmology

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Endothelial keratoplasty is now favored over full-thickness penetrating keratoplasty for corneal decompensation secondary to endothelial dysfunction. Although endothelial keratoplasty has evolved as surgeons strive to improve outcomes, fewer patients than expected achieve best corrected visual acuity of 20/20 despite healthy grafts and no ocular comorbidities. Reasons for this remain unclear, with theories including anterior stromal changes, differences in graft thickness and regularity, induced high order aberrations, and the nature of the graft-host interface. Newer iterations of endothelial keratoplasty such as thin manual DSEK, ultrathin DSAEK, and DMEK have achieved rates of 20/20 acuity of approximately 50%, comparable to modern cataract surgery , and it may be that a ceiling exists, particularly in the older age group of patients. Establishing the relative contribution of the factors that determine visual quality following endothelial keratoplasty will help drive further innovation, optimising visual and patient-reported outcomes while improving surgical efficacy and safety.

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The contribution of the posterior surface to the coma aberration of the human cornea

Cited by 49 publications

References 24 publications

OCT-based crystalline lens topography in accommodating eyes

OCT-based crystalline lens topography in accommodating eyes

Anterior Corneal, Posterior Corneal, and Lenticular Contributions to Ocular Aberrations

Determinants of visual quality after endothelial keratoplasty

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