Simone Beheregaray

Age-Related Changes in Anterior, Posterior, and Total Corneal Astigmatism

PURPOSE To evaluate age-related changes in anterior, posterior, and total corneal astigmatism by comparing simulated keratometric astigmatism to total corneal astigmatism. METHODS Corneal topography of the anterior and posterior surfaces was evaluated using three-dimensional optical coherence tomography in 419 patients with normal eyes (218 men and 201 women) with ages ranging from 8 to 93 years (mean ± standard deviation: 49.5 ± 23.1 years). Keratometric astigmatism was calculated using the keratometric index (1.3375) and radius of the anterior corneal curvature; anterior and posterior corneal curvature measurements were used to calculate total corneal astigmatism. RESULTS The keratometric and total astigmatism were 1.08 ± 0.71 diopters (D) and 1.03 ± 0.69 D, respectively. Vector analysis revealed a mean difference between keratometric and total astigmatism of 0.24 ± 0.09 D, which showed a significant correlation to age (P < .0001). In eyes with with-the-rule astigmatism, keratometric astigmatism overestimated total astigmatism. In eyes with against-the-rule astigmatism, keratometric astigmatism underestimated total astigmatism. CONCLUSIONS The anterior corneal surface shifts from with-the-rule to against-the-rule astigmatism with aging, whereas the posterior corneal surface remains as against-the-rule astigmatism in most cases. The variation in the anterior astigmatism is the most important factor contributing to this change. Total corneal astigmatism is a better predictor than keratometric astigmatism for selecting toric intraocular lenses.

Keratoconus Diagnosis Using Anterior Segment Polarization-Sensitive Optical Coherence Tomography

PURPOSE To investigate the tissue properties of keratoconic and normal corneas in vivo by using polarization-sensitive optical coherence tomography (PS-OCT), and to evaluate early keratoconus by the area under the receiver operating characteristic curve (AUROC) and Mahalanobis distance analysis. METHODS Thirty-one eyes of 20 patients with keratoconus, 7 eyes of 7 patients with keratoconus suspect, and 25 eyes of 25 normal subjects were investigated by PS-OCT and corneal and anterior segment (CAS)-OCT. Average of en face phase retardation of the posterior surface of the cornea, curvature, videokeratographic parameters, regular and irregular astigmatism, pachymetry map, and elevation were measured. The AUROC of each parameter was calculated to evaluate the diagnostic power to detect keratoconus and keratoconus suspect. RESULTS While in normal controls, the center of the en face phase retardation map showed low and homogeneous birefringence, in keratoconic corneas the birefringence increased with disease severity. Some keratoconus suspects had apparent high birefringence values without displaying morphologic signs of keratoconus in the anterior surface. The phase retardation values for normal, keratoconus suspect, and keratoconus subjects were, respectively, 0.20 ± 0.06, 0.35 ± 0.06, and 0.50 ± 0.14 radians in 3 mm diameter and 0.29 ± 0.22, 0.33 ± 0.13, and 0.74 ± 0.45 radians in 6 mm diameter. Outer morphological parameters such as curvature, videokeratographic parameters, regular and irregular astigmatism, and elevation showed high AUROCs for discriminating keratoconus from normal controls. On the other hand, using Mahalanobis distance, the AUROC of phase retardation, which represents microstructural properties of tissue, showed high value (0.989-1.000) for discriminating between keratoconus suspects and normal controls. CONCLUSIONS Average of en face phase retardation of the posterior surface of the cornea was increased in keratoconus patients due to changes in the lamellar structure of collagen fibers. Phase retardation was sensitive with regard to discriminating keratoconus suspect and might be useful for detecting very early or even subclinical keratoconus.

Noninvasive evaluation of phase retardation in blebs after glaucoma surgery using anterior segment polarization-sensitive optical coherence tomography.

PURPOSE Evaluation of bleb morphology using anterior segment optical coherence tomography (OCT) can offer important information regarding bleb function after glaucoma surgery. However, analysis of tissue properties, such as scar fibrosis of blebs, is difficult with conventional OCT. The birefringence of the blebs as susceptible measure of fibrosis scar was evaluated using polarization-sensitive OCT (PS-OCT) and its relation with bleb function was assessed. METHODS One hundred and fifty-three blebs of 122 patients that had undergone trabeculectomy or an Ex-Press tube shunt were examined. Also, in 14 blebs of 12 patients, consecutive measurements were performed for 2 months after surgery. The birefringence of blebs was evaluated by measuring alteration of phase retardation using PS-OCT. Functionality of the bleb was classified according to IOP and medication. The bleb morphology in terms of size and characteristics was evaluated using three-dimensional (3D) cornea and anterior segment OCT. RESULTS The alteration of phase retardation of blebs had the largest impact on bleb functionality than bleb morphology as shown by multiple regression analysis. In consecutive measurements, no blebs showed abnormal phase retardation until 1 week after surgery. Some blebs showed partial increase of phase retardation at 1 month after surgery. CONCLUSIONS Intrableb fibrosis can be noninvasively evaluated with PS-OCT. Evaluation of birefringence by measuring phase retardation alterations using PS-OCT suggests new approaches for the postoperative management of glaucoma blebs regarding antifibrotic treatment for preventing IOP increases.

Comparison of three-dimensional optical coherence tomography and combining a rotating Scheimpflug camera with a Placido topography system for forme fruste keratoconus diagnosis

Objective To evaluate the ability of parameters measured by three-dimensional (3D) corneal and anterior segment optical coherence tomography (CAS-OCT) and a rotating Scheimpflug camera combined with a Placido topography system (Scheimpflug camera with topography) to discriminate between normal eyes and forme fruste keratoconus. Methods Forty-eight eyes of 48 patients with keratoconus, 25 eyes of 25 patients with forme fruste keratoconus and 128 eyes of 128 normal subjects were evaluated. Anterior and posterior keratometric parameters (steep K, flat K, average K), elevation, topographic parameters, regular and irregular astigmatism (spherical, asymmetry, regular and higher-order astigmatism) and five pachymetric parameters (minimum, minimum–median, inferior–superior, inferotemporal–superonasal, vertical thinnest location of the cornea) were measured using 3D CAS-OCT and a Scheimpflug camera with topography. The area under the receiver operating curve (AUROC) was calculated to assess the discrimination ability. Compatibility and repeatability of both devices were evaluated. Results Posterior surface elevation showed higher AUROC values in discrimination analysis of forme fruste keratoconus using both devices. Both instruments showed significant linear correlations (p<0.05, Pearsons correlation coefficient) and good repeatability (ICCs: 0.885–0.999) for normal and forme fruste keratoconus. Conclusions Posterior elevation was the best discrimination parameter for forme fruste keratoconus. Both instruments presented good correlation and repeatability for this condition.

Influence on visual function of forward light scattering associated with subsurface nanoglistenings in intraocular lenses

Purpose To quantitatively assess the impact of subsurface nanoglistenings on forward light scattering and visual function. Setting University of Tsukuba, Tsukuba, Japan. Design Case‐control study. Methods Eyes with subsurface nanoglistenings and increased intraocular lens (IOL) surface light scattering and control eyes without subsurface nanoglistenings were evaluated. Forward light scattering was assessed with a double‐pass device (Optical Quality Analysis System II) using the objective scatter index (OSI) as a quantitative parameter. Backward light scattering in the IOL surface was evaluated using Scheimpflug imaging (EAS‐1000). The contrast sensitivity function was assessed as the area under the log contrast sensitivity function (AULCSF) measured with the Optec 6500 device. Correlations between the OSI, visual function, age, time after surgery, IOL power, and backward light scattering were analyzed. Results In the study group, logMAR corrected distance visual acuity (CDVA) ranged from −0.176 to 0.045 (−0.06 ± 0.07 [SD]); no patient had a CDVA worse than 20/25. The OSI was significantly higher than in the control group (P=.0074) and correlated with CDVA (P=.0021), AULCSF photopic without glare (P=.0002) and with glare (P<.0001), and AULCSF mesopic without glare (P=.0038) and with glare (P=.0008). Multivariate analysis showed OSI was the only variable that correlated with CDVA and contrast sensitivity with glare. The OSI and age correlated with contrast sensitivity without glare (P<.05). Conclusions Eyes with subsurface nanoglistenings had increased forward light scattering but no deterioration in CDVA. Increases in forward light scattering correlated with reductions in visual acuity and contrast sensitivity, although both remained within their normal range. Financial Disclosures No author has a financial or proprietary interest in any material or method mentioned.

Repeatability of corneal phase retardation measurements by polarization-sensitive optical coherence tomography.

PURPOSE Polarization-sensitive optical coherence tomography (PS-OCT) can evaluate internal tissue structures of the cornea, such as collagen fibers, by phase retardation measurement. In this study, we assessed the repeatability of corneal phase retardation measurements using anterior segment PS-OCT. METHODS A total of 173 eyes of 173 patients were measured using PS-OCT. In total, 58 eyes of young subjects with normal corneas, 28 eyes of old subjects with normal corneas, 26 eyes with corneal dystrophy or degeneration, 37 eyes with corneal transplantation, and 24 eyes with keratoconus were evaluated. The 3-mm diameter average of en face phase retardation of the posterior corneal surface was examined using PS-OCT. To evaluate the repeatability, intraclass correlation coefficients (ICCs) were calculated for intraobserver repeatability and interobserver repeatability analysis. RESULTS Polarization-sensitive OCT showed good repeatability for corneal measurements. Intraclass correlation coefficients of intraobserver and interobserver repeatability of all the subjects were 0.989 and 0.980, respectively. Intraclass correlation coefficients of the intraobserver for each group, that is, young and old subjects with normal cornea, cornea dystrophy/degeneration, corneal transplantation, and keratoconus, were 0.961, 0.975, 0.984, 0.978, and 0.996, respectively. Interobserver ICCs for the above-mentioned respective groups were 0.952, 0.964, 0.988, 0.959, and 0.975, respectively. CONCLUSIONS Polarization-sensitive OCT showed good repeatability for phase retardation measurements of central corneas not only for normal corneas, but also for various diseased corneas. Polarization-sensitive OCT might be useful for evaluating corneal phase retardation, which is one of the parameters that defines birefringence.

Quantitative Evaluation of Phase Retardation in Filtering Blebs Using Polarization-Sensitive Optical Coherence Tomography.

Purpose Polarization-sensitive optical coherence tomography (PS-OCT) can detect and evaluate scar fibrosis of the filtering blebs after glaucoma surgery. Although the change in phase retardation reportedly reflects bleb function, quantitative assessment of phase retardation in ocular tissues has not been conducted. We aimed to establish quantitative methods to investigate changes in phase retardation in the blebs after surgery using PS-OCT. Methods Twenty-two blebs of 22 patients who had undergone glaucoma filtration surgery were consecutively examined for 4 months. Phase retardation was measured by PS-OCT and quantitatively analyzed to evaluate its relationship with bleb function based on intraocular pressure and medication use. Cross-sectional re-evaluation was also performed for a previous data set of 153 blebs of 122 patients. Results In consecutive measurements, all blebs showed a low phase retardation value and good bleb function until 2 weeks. One month postoperatively, the phase retardation value was significantly increased, whereas bleb function was still good. The phase retardation value at 1 month postoperatively was significantly correlated with bleb function at 4 months postoperatively. While 55.6% of blebs with a high phase retardation value at 1 month subsequently lost function, only 7.7% with a low phase retardation value had bleb failure. In the cross-sectional re-evaluation, the quantitatively evaluated phase retardation value was highly correlated with bleb function (β = 0.770, P < 0.001). Conclusions An increase in phase retardation preceded deterioration of bleb function. The change in phase retardation may provide a prognostic metric for bleb function in the early stage after surgery.

In vivo retinal and choroidal hypoxia imaging using a novel activatable hypoxia-selective near-infrared fluorescent probe.

PurposeRetinal hypoxia plays a crucial role in ocular neovascular diseases, such as diabetic retinopathy, retinopathy of prematurity, and retinal vascular occlusion. Fluorescein angiography is useful for identifying the hypoxia extent by detecting non-perfusion areas or neovascularization, but its ability to detect early stages of hypoxia is limited. Recently, in vivo fluorescent probes for detecting hypoxia have been developed; however, these have not been extensively applied in ophthalmology. We evaluated whether a novel donor-excited photo-induced electron transfer (d-PeT) system based on an activatable hypoxia-selective near-infrared fluorescent (NIRF) probe (GPU-327) responds to both mild and severe hypoxia in various ocular ischemic diseases animal models.MethodsThe ocular fundus examination offers unique opportunities for direct observation of the retina through the transparent cornea and lens. After injection of GPU-327 in various ocular hypoxic diseases of mouse and rabbit models, NIRF imaging in the ocular fundus can be performed noninvasively and easily by using commercially available fundus cameras. To investigate the safety of GPU-327, electroretinograms were also recorded after GPU-327 and PBS injection.ResultFluorescence of GPU-327 increased under mild hypoxic conditions in vitro. GPU-327 also yielded excellent signal-to-noise ratio without washing out in vivo experiments. By using near-infrared region, GPU-327 enables imaging of deeper ischemia, such as choroidal circulation. Additionally, from an electroretinogram, GPU-327 did not cause neurotoxicity.ConclusionsGPU-327 identified hypoxic area both in vivo and in vitro.

Comparison of intensity, phase retardation, and local birefringence images for filtering blebs using polarization-sensitive optical coherence tomography

Polarization-sensitive optical coherence tomography (PS-OCT) allows the recording of depth-resolved polarimetric measurements. It has been reported that phase retardation and local birefringence images can noninvasively detect fibrotic area in blebs after glaucoma surgery. Evaluation of scar fibrosis in blebs is important not only for predicting bleb function, but also for planning revision trabeculectomy. Herein, we characterize the intensity, phase retardation, and local birefringence images of blebs using PS-OCT. A total of 85 blebs from 85 patients who had undergone trabeculectomy were examined. Both phase retardation and local birefringence images detected fibrotic changes in blebs after glaucoma surgery. Phase retardation images detected slight fibrotic change during the early stage after surgery, whereas local birefringence images showed localized fibrotic tissue. There are two main patterns of local birefringence image changes in blebs: plate-like birefringence changes and diffuse changes. The area of plate-like birefringence change was significantly larger in poorly functioning blebs and is thus correlated with bleb function. These data suggest that the plate-like fibrotic change evaluation by PS-OCT may be useful not only for noninvasive evaluation of fibrotic scar tissue in blebs, but also for developing strategies for revision trabeculectomy.