Abstract
BackgroundTo explore the possible causes of tomography suspect keratoconus (TSK) marked by Tomography in screening keratoconus in a Chinese cohort, and the reasonable range of corneal horizontal diameter and thickness for decreasing the proportion of TSK.MethodsNested case-control study from a single center prospective cohort. All subjects were selected from the Peking University Third Hospital Ectasia Cornea Disease Cohort Project database, which included myopic patients seeking corneal refractive surgical corrections since 2013. Demographic information, basic eye examination, and auxiliary equipment examination including refraction, IOL-master, Pentacam, Sirius, and Topolyzer were recorded. In this study, all cases were classified into two groups: TSK group and normal control (NC) group, and all of them were followed up at least 2 years. The former is consisted of those whose screening examinations of tomography are abnormal, the latter is those whose screening examinations are normal. All of them have already been followed up at least 2 years without abnormalities after excimer laser corneal refractive surgeries. Unpaired t tests and Chi-square tests were used to compare the differences of indices from the tomography between the two groups.ResultsOf 183 TSK eyes (109 patients) and 160 NC eyes (83 patients), the mean age is 28.0 and 26.3 years old respectively. The corneal horizontal diameter is 11.5–11.8 mm in TSK group and 11.8–12.0 mm in NC group. The central corneal thickness is nearly 520 μm in the former and 550 μm in the latter. For Sirius, the TSK ratio of indices of SIf and SIb is 41.5 and 39.9% respectively in TSK group. For Pentacam, the TSK ratio of index IHD is 59.0% and “final D” is 72.7%.ConclusionsCorneal horizontal diameter and central corneal thickness have great influences on the results of corneal tomography in detecting the suspect keratoconus.
Highlights
Keratoconus (KC), is one of the most important bilateral diseases of the cornea, in which the central portion of the cornea becomes thinner and bulges forward in a cone-shaped fashion resulting in myopia, irregular astigmatism, and eventually visual impairment [1]
This study explores the reasonable range of horizontal corneal diameter and pachymetry readings, based on the screening results which can be more accurate for Chinese refractive surgery candidates
In the Peking University Third Hospital Ectasia Cornea Disease Cohort Project, we found that the corneal shape is still stable for more than 2 years after the corneal refractive surgeries in some cases which had been suggested with abnormalities by tomography and there were no signs of ectasia in them
Summary
Keratoconus (KC), is one of the most important bilateral diseases of the cornea, in which the central portion of the cornea becomes thinner and bulges forward in a cone-shaped fashion resulting in myopia, irregular astigmatism, and eventually visual impairment [1]. It’s very important to screen suspect keratoconus preoperatively, as corneal refractive surgery becomes more and more popular in the world. More recent studies using corneal tomography provide more sensitive estimates of prevalence/incidence [8] with the advent of Scheimpflug technology, such as Pentacam and Sirius. The Sirius combined the Placido disc and Scheimpflug technique, final class of “normal / suspect / KC” was given through a proprietary process analysis. Both of the built-in automatic analysis programs are generated mainly based on the North and South American [11] and European cases. To explore the possible causes of tomography suspect keratoconus (TSK) marked by Tomography in screening keratoconus in a Chinese cohort, and the reasonable range of corneal horizontal diameter and thickness for decreasing the proportion of TSK
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