Keratoconus, the most common corneal ectasia, is a progressive corneal Figure 8. Keratoconus on Pentacam. The anterior axial map shows. To assess the effect of age on elevation and pachymetric Pentacam keratoconus (KC) detection indices, and the need to adjust normative. Dr. Holladay says the changes ac-companying keratoconus are According to Dr. Holladay, the Pentacam, Galilei and Visante Omni all pick.
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To assess the effect of age on znd and pachymetric Pentacam keratoconus KC detection indices, and the need to adjust normative values accordingly.
Subjects were categorised into three groups according to their age: There were statistically significant differences among the three groups regarding many elevation indices: Age is an important determinant of elevation indices, significantly altering their normative values. The use of the more robust pachymetry, rather than elevation, indices is recommended in subjects below 21 or above 40 years of age.
Pentacam Analysis of Keratoconus Indices in Normal Patients | IOVS | ARVO Journals
As corneal refractive surgery evolves, professional expectations increase and require continuous refinements of preoperative screening and interpretation [ 1 ].
Currently, Scheimpflug tomography devices, such as the Pentacam OCULUS Optikgerate GmbH, Wetzlar, Germanyare the most popular techniques providing anterior and posterior corneal surface elevations, together with a detailed thickness profile [ 2 ]. keratoconuw
Early and accurate keratoconus KC detection using variable indices has been widely discussed, comparing the sensitivities and specificities of various parameters [ 3 — 5 ]. Furthermore, new algorithms and combined indices have been introduced, aiming at earlier and more precise KC detection [ 67 ].
Ageing can alter the human corneal topography, with penracam detected increase in aberrations [ 8 ] and an altered pattern of corneal astigmatism [ 9 ]. The possible effect of age on corneal elevation and pachymetric keeatoconus has been sparsely discussed [ 10 ]. Moreover, the spherical refractive kdratoconus effect on tomographic corneal values is an issue that deserves proper analysis.
Most of the topographic screening values were initially based on a predominantly myopic population [ 11 ], rendering it obviously inaccurate to apply the normative values on the hyperopic population, as emphasized in Kim et al. This study aims at assessing the effect of age on elevation and pachymetry-based KC diagnostic indices and at studying this age effect after controlling for the spherical refractive error, using the OCULUS Pentacam, and the possible need to adjust the normative values accordingly.
This is a retrospective study including 95 penyacam myopic normal corneas imaged in the time interval between June and Decemberusing the Pentacam branded as Allegro Oculyzer WaveLight, GmbH, Erlangen, Germany [ 12 ] with software version 1. The study adhered to the tenets of the Declaration of Helsinki keeratoconus was approved by the kratoconus institutional review board.
We excluded candidates with any detected corneal pathology, previous ocular surgery, contact lens wear within the last two weeks, or narrow palpebral fissure precluding proper imaging.
Effect of Age on Pentacam Keratoconus Indices
Moreover, the participants were followed up annually until December to confirm that no ectasia developed along the years, either in eyes that underwent laser refractive surgeries 88 eyes or in those who were unsuitable due to petacam myopic refractive error values 7 eyes. Hence, we made sure that any determined changes in index values were not due to forme fruste KC.
Corneal evaluation on follow-up included the evaluation of refraction stability penfacam, in query cases, by assessing the posterior elevation values, using the same Kerafoconus device. Subjective refraction and spherical equivalent SE calculation were performed.
All eyes were scanned at least thrice by Pentacam according to the recommendations of the device manual. Each scan included 25 Scheimpflug images. The investigated indices included: Subjects were then categorised into three groups according to their age on the day of Pentacam evaluation: The following tests were performed: Values were considered statistically significant if the value was less than 0.
The study included 95 participants, with an average age of Forty-nine right eyes and 46 left eyes were examined. The SE was evenly represented in the three age groups. The indices showing statistical significance among the three groups were then compared between pentacsm 2 groups Table 2.
The 2 and 3 SD limits of the indices showing statistical significance for each of the three age groups are shown in Table 3. Most keratoocnus indices were found correlated with SE alone when calculating the partial correlation controlling for age.
However, only the elevation indices from BFS were found correlated with age.
kefatoconus Age was not found correlated to any of the pachymetric indices. Higher expectations for corneal refractive surgeries mandate better screening strategies and data analysis to avoid inappropriately permitting or excluding candidates [ 2 ]. This necessitates continuous refinements for any parameter that can cause falsely positive or negative diagnosis. Although there is a consensus on the absence of a single index keratoconua detecting KC and that KC diagnosis requires multiple index interpretation, adjusting and comparing the accuracies of individual indices remain an issue that deserves proper investigation.
It would be highly valuable to highlight the indices to rely upon, in which cases, and their normal range. The human cornea, together with other parts of the eye, suffers age-related changes. Some corneal topographic age changes have been previously highlighted [ 89 ]. Likewise, the corneal tomographic parameters, pachymetric and elevation indices, need proper evaluation regarding their possible changes with age [ 10 ]. Most of the Pentacam normative database was obtained from refractive surgery candidates, with an age ahd of 21 to 40 years.
The present study evaluated many pachymetry and elevation indices not only for this age range, but also for the late teenagers below 21 and for older subjects above 40 years of age, hence including a wide age range, aiming at investigating the correlation between age and various KC detection indices.
To be sure that the observed difference is not a fallacy caused by the refraction as a covariant, we performed partial correlation keratooconus controlled for the SE effect. This confirmed that the observed changes in indices were caused by the age effect and not only a fallacy due to refractive variation among the recruited subjects. However, after controlling for the SE effect, pentscam latter index did not kfratoconus robust in correlation to age.
Catching Keratoconus: Making the Tough Calls
Thus, our results highlight a significant correlation between age and all the studied elevation indices kegatoconus hence the inaccuracy of relying upon them using usual cutoff values in evaluating refractive candidates. On evaluating elevation indices in late teenagers below 21 years, we detected a statistically significant decrease of most of the elevation indices: In the elevation indices petacam showed statistically significant differences among groups, the effect of age was most highlighted on comparing subjects below 21 years to those above 40 years, where all the elevation indices were statistically significant between them.
Therefore, extremes of age are the most sensitive cohorts to elevation index fallacies. Regarding the older age group, more than 40 years of age, there was a tendency for higher PE and lower AE compared with younger subjects.
However, this did not reach statistical significance in all cases. However, their study included a heterogeneous group of patients with KC and forme fruste KC together with healthy subjects. As the values of indices in KC and forme fruste KC are highly variable, and these conditions are a confounding factor on their own, we preferred to include normal corneas only. This declares the robustness of the mentioned indices. Moreover, after controlling for the SE keratocouns, all the pachymetric indices showed no statistical significance in correlation to age.
This important finding poses a recommendation of relying on pachymetric rather than elevation parameters in prerefractive surgery assessment for candidates below the age of 21 and those above 40 years of age.
Elevation-based indices were the parameters that showed a statistically significant difference across studied age groups. Values above 3 SD are suggestive of a probable pathology Table 3.
Although the primary aim of our study was not to evaluate the refractive error effect, our results revealed that after controlling for the SE effect, all the elevation indices, from either BFS or BFTE, were correlated with age. This finding reaffirmed our suggestion of relying on pachymetric indices rather than elevation indices for extremes of age.
The evaluation of KC indices in relation to the SE effect has been previously discussed. On the contrary, Hashemi et al. However, these studies analysed the SE effect between myopic and hyperopic cohorts. To the best of our knowledge, no studies analysed the effect of both age and refraction within the myopic range. In our study, we followed up the subjects for several years, either with or without performing laser refractive surgeries, aiming to absolutely exclude forme fruste KC, an issue that may lead to fallacies keraotconus results.
However, in other studies, including Kim et al.
Ajd believe that following up patients is more reliable. We recommend the use of pachymetry-based indices, or the elevation indices with altered normative data, when epntacam corneas of patients outside the usual 21—40 years range. Ramy Riad Fikry received travel support from Novartis.
Indexed in Science Citation Index Expanded. Subscribe to Table of Contents Alerts. Table of Contents Alerts. Introduction As corneal refractive surgery evolves, professional expectations increase and require continuous refinements of preoperative screening and interpretation [ 1 ]. Materials and Methods This is a retrospective study including 95 consecutive myopic normal corneas imaged in the time interval between June and Decemberusing the Pejtacam branded as Allegro Oculyzer WaveLight, GmbH, Erlangen, Germany [ 12 ] with software version 1.
Demographics The study included 95 participants, with an average age of Mean, standard deviation, and statistical significance of different indices among the three age groups. The significance value of comparing indices between every 2 groups. Correlation of age with other keratocons, partial correlation with SE after controlling for age effect, and partial correlation with age after controlling for SE effect.
Ambrosio Jr, and S. View at Google Scholar S. Holladay, Allegro Oculyzer User Manual.
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