Several metrics have been proposed in literature to assess the perceptual quality of two-dimensional images. However, no similar effort has been devoted to quality assessment of stereoscopic images. Therefore, in this paper, we review the different issues related to 3D visualization, and we propose a quality metric for the assessment of stereopairs using the fusion of 2D quality metrics and of the depth information. The proposed metric is evaluated using the SAMVIQ methodology for subjective assessment. Specifically, distortions deriving from coding are taken into account and the quality degradation of the stereopair is estimated by means of subjective tests.

https://hal.archives-ouvertes.fr/hal-00362891/document

Quality Assessment of Stereoscopic Images

Keratoconus (KC) is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.

/pdf/the-genetic-and-environmental-factors-for-keratoconus-1e06u9jxtq.pdf

The genetic and environmental factors for keratoconus.

We identified mutations in the VSX1 homeobox gene for two distinct inherited corneal dystrophies; posterior polymorphous dystrophy (PPD) and keratoconus. One of the mutation (R166W) responsible for keratoconus altered the homeodomain and impaired DNA binding. Two other sequence changes (L159M and G160D) were associated with keratoconus and PPD, respectively, and involved a region adjacent to the homeodomain. The G160D substitution, and a fourth defect affecting the highly conserved CVC domain (P247R), occurred in a child with very severe PPD who required a corneal transplant at 3 months of age. In this family, relatives with the G160D change alone had mild to moderate PPD, while P247R alone caused no corneal abnormalities. However, with either the G160D or P247R mutation, electroretinography detected abnormal function of the inner retina, where VSX1 is expressed. These data define the molecular basis of two important corneal dystrophies and reveal the importance of the CVC domain in the human retina.

VSX1: A gene for Posterior Polymorphous Dystrophy and Keratoconus

Keratoconus (KC) is a common degenerative
condition that frequently results in visual loss
with an onset typically in early adulthood.
It is the single most common reason for
keratoplasty in the developed world. The cause
and underlying pathological mechanism are
unknown, but both environmental and genetic
factors are thought to contribute to the
development of the disease. Various strategies
have been employed to address the gap in
our understanding of this complex disease,
with the expectation that over time more
sophisticated therapies will be developed.
In this review we summarise our current
knowledge of the aetiology and risk factors
associated with KC.

/pdf/the-pathogenesis-of-keratoconus-39unsovarp.pdf

The pathogenesis of keratoconus

Keratoconus has been classically defined as a progressive, non-inflammatory condition, which produces a thinning and steepening of the cornea. Its pathophysiological mechanisms have been investigated for a long time. Both genetic and environmental factors have been associated with the disease. Recent studies have shown a significant role of proteolytic enzymes, cytokines, and free radicals; therefore, although keratoconus does not meet all the classic criteria for an inflammatory disease, the lack of inflammation has been questioned. The majority of studies in the tears of patients with keratoconus have found increased levels of interleukin-6 (IL-6), tumor necrosis factor-α(TNF-α), and matrix metalloproteinase (MMP)-9. Eye rubbing, a proven risk factor for keratoconus, has been also shown recently to increase the tear levels of MMP-13, IL-6, and TNF-α. In the tear fluid of patients with ocular rosacea, IL-1α and MMP-9 have been reported to be significantly elevated, and cases of inferior corneal thinning, resembling keratoconus, have been reported. We performed a literature review of published biochemical changes in keratoconus that would support that this could be, at least in part, an inflammatory condition.

/pdf/keratoconus-an-inflammatory-disorder-3o40wp8fc3.pdf

Keratoconus: an inflammatory disorder?

Purpose: To determine the prevalence and associated factors for keratoconus in a college student population sample in Jerusalem.Methods: Volunteers participated in this cross-sectional study. Videokeratography was performed on both eyes of each subject who also completed an anonymous questionnaire. Keratoconus was defined by cone apex ≥ 50D, inferior-superior dioptric difference ≥ 3.5 diopters, as well as positive results from the software indices KISA, KCI and KSI. The association between independent predictors and keratoconus was analyzed using multivariate logistic regression analysis.Results: Of a total of 987 volunteers, 981 (mean age 24.4) were included. The prevalence of keratoconus among all subjects was 2.34% (95% confidence interval [CI] 1.4–3.3). It was significantly higher in men (4.91%, CI 2.6–7.3) than women (1.07%, CI 0.3–1.9) but not between Israeli Arabs (3.0%, CI 0.6–5.4) and Israeli Jews (2.2%, CI 1.2–3.3). Keratoconus was significantly associated with positive family history of the dis...

Prevalence and Associated Factors of Keratoconus in Jerusalem: A Cross-sectional Study

Keratoconus is a noninflammatory disorder characterized by ectasia of the central or inferior portion of the cornea. This review presents the scant epidemiological information known to date and the factors believed to cause the development of the disease. They are the genetic factors for which evidence come from family studies, twin studies and genetic loci. There appears to be multiple genes causing a keratoconus phenotype with variable penetration. However, the genetic predisposition might not be enough; environmental factors, such as eye rubbing, atopy and UV exposure, may have a role in generating the disease.

https://www.ijkecd.com/doi/pdf/10.5005/jp-journals-10025-1002

The Epidemiology and Etiology of Keratoconus

PurposeTo determine whether consanguinity is a risk factor for keratoconus (KC).MethodsA questionnaire was distributed to all patients presenting to St. John Eye Hospital, Jerusalem, Israel. Questionnaire included data on demographic characteristics and potential risk factors. Patients were

Is Consanguinity a Risk Factor for Keratoconus

Purpose. This study was designed to compare higher order aberrations of the cornea and of the eye with inferior-superior (I-S) corneal topographic values in keratoconic eyes. Methods. We studied 92 eyes from 78 subjects: 21 eyes of 14 subjects with suspected keratoconus, 23 eyes of 16 subjects with manifest keratoconus, and 48 eyes of 48 subjects without keratoconus using the L80 wave, an instrument which can measure corneal topography and aberrations simultaneously with a large dynamic range making it possible to evaluate higher order aberrations to the seventh order of the Zernike polynomial function series. Results. All ocular and corneal higher order aberrations were found to be significantly higher for keratoconic than normal eyes, but for suspected keratoconus the results were mixed. Corneal aberrations were higher than ocular aberrations due to compensation from the internal aberrations. For manifest keratoconus, the corneal and ocular vertical coma displayed the largest difference being 38.6 and 78.5 times higher, respectively, than normal eyes, while the largest differences for suspected keratoconus were only 5.3 and 4.0 times higher, respectively. On the other hand, inferior-superior dioptric asymmetry was 9.4 and 37.3 times higher for suspected keratoconus and keratoconic eyes, respectively, than normal eyes. The separation of normality curves between suspected keratoconus and normal eyes was 28.6% for I-S and 14.3% for both corneal vertical coma and corneal total coma. Conclusions. Although corneal vertical coma and, to a lesser extent, ocular vertical coma were found to be good indicators for the detection of keratoconic eyes, the traditional corneal topographic value such as the inferior-superior dioptric asymmetry remains an important predictor for identifying suspected keratoconus. However, ocular vertical coma and ocular higher order total root mean square also represent a good means of identifying suspected keratoconus. (Optom Vis Sci 2012;89:1–●●●)

Einat Shneor

Papers

The genetic and environmental factors for keratoconus.

Prevalence and Associated Factors of Keratoconus in Jerusalem: A Cross-sectional Study

The Epidemiology and Etiology of Keratoconus

Is Consanguinity a Risk Factor for Keratoconus

Aberrations and topography in normal, keratoconus-suspect, and keratoconic eyes.