Corneal Eccentricity as a Tool for the Diagnosis of Keratoconus

Dao, C L; Kok, J. H. C.; Brinkman, C. J. J.; Mil, C J van

doi:10.1097/00003226-199407000-00009

Cited by 16 publications

(18 citation statements)

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“…In this study, the relationship between corneal shape and thickness may have lacked significance on account of excluding cases with keratoconus and abnormal corneas. In other words, contrary to keratoconus corneas, where there is steeping and increased eccentricity as the cornea becomes thinner, 3 no relation exists between thickness and eccentricity in normal corneas. In fact, these parameters may be related in cases when the cornea changes, but they are independent from each other in the normal cornea.…”

Section: Discussionmentioning

confidence: 87%

“…5 According to previous studies, eccentricity can be a diagnostic factor for the early diagnosis of keratoconus in its primary stages, and it has been suggested that eccentricity increases before slit-lamp signs appear. 3 Some studies suggest that the eccentricity value in normal adult population is from 0.4 to 0.6, 6 , 7 , 8 , 9 but it can be greater than 0.8 in keratoconus patients. 3 According to the available literature, this index also has significant implications for refractive surgery.…”

Section: Introductionmentioning

confidence: 99%

“… 3 Some studies suggest that the eccentricity value in normal adult population is from 0.4 to 0.6, 6 , 7 , 8 , 9 but it can be greater than 0.8 in keratoconus patients. 3 According to the available literature, this index also has significant implications for refractive surgery. 10 Induced astigmatism as a result of cataract surgery is related to several factors; however, the highest amount of induced astigmatism is seen in corneas with high anterior eccentricity.…”

Section: Introductionmentioning

confidence: 99%

“…Knowledge of normal eccentricity values at different ages has implications for identifying corneal abnormalities such as keratoconus, contact lens fitting, refractive surgery, cataract surgery, and IOL power calculation. 2 , 3 , 4 In contact lens fitting, the corneal shape determines the relationship between the cornea and the lens. Corneas with the same keratometry readings may be different in terms of eccentricity.…”

Section: Introductionmentioning

confidence: 99%

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The normal distribution of corneal eccentricity and its determinants in two rural areas of north and south of Iran

Heydarian

Hashemi

Shokrollahzadeh

et al. 2018

Journal of Current Ophthalmology

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PurposeThe aim of this study was to determine the distribution of corneal eccentricity (E-value) in a normal population and to examine related factors.MethodsIn this cross-sectional study, two villages were selected in Iran using multistage cluster sampling. Selected persons were invited to have a comprehensive eye examination. Examinations in each village were performed at a specific location under standard conditions. After testing for vision and refraction and conducting the slit-lamp exam, E-value was measured with Pentacam.ResultsOf the 3851 selected individuals, 3314 participated in the study. After applying the exclusion criteria, data from 2610 subjects was used in the analysis for this report. Mean E-value was 0.53 [95% confidence interval (CI): 0.52 to 0.54]. E-value was not significantly different between males and females. Mean E-value reduced with age from 0.60 in subjects aged 6–20 years to 0.47 in subjects older than 70 years. The hyperopic group of participants had significantly lower E-value than myopic and emmetropic ones (P < 0.001). The relationship of E-value with age, gender, and other anterior segment variables and spherical equivalent was examined in a multiple linear regression model. In multiple linear regression model, age (coef = −0.003), spherical equivalent refraction (coef = −0.005), pupil diameter (coef = 0.018), anterior chamber volume (coef = −0.001), and anterior chamber angle (coef = 0.003) significantly correlated with E-value.ConclusionsThe results of this study showed that the cornea in normal populations is prolate, and the degree of prolateness varies by age, such that older age is associated with a less prolate cornea. This study showed that factors such as age and refractive errors and anterior chamber indices influence the E-value.

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Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The normal distribution of corneal eccentricity and its determinants in two rural areas of north and south of Iran

Heydarian

Hashemi

Shokrollahzadeh

et al. 2018

Journal of Current Ophthalmology

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“…Computerized corneal topographers provide full knowledge of the anterior corneal curvature, information that is applicable to current clinical practice (ie, contact lens fitting and management, 1,2 eye modeling and ocular aberration analysis, 3,4 corneal refractive surgery, 5,6-8 and detection and follow-up of corneal pathological conditions [9][10][11].…”

mentioning

confidence: 99%

Asphericity of the anterior human cornea with different corneal diameters

González-Meijóme¹,

Villa-Collar²,

Montés‐Micó³

et al. 2007

Journal of Cataract and Refractive Surgery

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There were differences in sagittal corneal height calculations considering constant or variable models of Q. Concern arises when surgical interventions depend on corneal Q-values to predict the outcomes. Surgeons should be aware which procedure is behind Q computing by different corneal topographers and that a constant Q-value cannot reflect the actual shape of the cornea as significant departures from the actual sagittal height can arise depending on which Q-value is assumed.

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An evaluation of the keratoconic cornea using computerised corneal mapping and ultrasonic measurements of corneal thickness

Owens

Watters

1996

Ophthalmic and Physiological Optics

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Reports indicate the presence of up to three independent cone shapes in keratoconus (round/oval/global) but the preponderance of one cone over another is unclear. This work evaluates keratoconic corneal topography and corneal thickness using videokeratoscopy and ultrasound pachometry, respectively. An EyeSys videokeratoscope (VKS) (EyeSys Laboratories, Houston, TX, USA) was used to assess the topography of 54 keratoconic eyes (27 subjects) and 27 age-matched normals. In addition, ultrasonic pachometry measurements were made over 14 known areas in normal and keratoconic eyes. Corneal thinning was significant for all keratoconic areas measured except for the far temporal cornea. A correlation between corneal radius and thickness was evident. Analysis of cone shape revealed a potential fourth variety: the asymmetric bow-tie cone. Further topographic evaluation of this cone entity using the VKS revealed its dependence on gaze direction which may account for apparent differences in progression patterns between round and bow-tie cones.

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Corneal Eccentricity as a Tool for the Diagnosis of Keratoconus

Cited by 16 publications

References 0 publications

The normal distribution of corneal eccentricity and its determinants in two rural areas of north and south of Iran

The normal distribution of corneal eccentricity and its determinants in two rural areas of north and south of Iran

Asphericity of the anterior human cornea with different corneal diameters

An evaluation of the keratoconic cornea using computerised corneal mapping and ultrasonic measurements of corneal thickness

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