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The recent study by Vega-Estrada et al highlights some of the challenges in diagnosing keratoconus in Down syndrome (DS). Previous studies have shown that the cornea of individuals with DS without evidence of keratoconus appear to be steeper and thinner than the general population, both being features characteristic of keratoconus. Vega-Estrada et al further identified that posterior keratometry was similar in DS to mild keratoconus, however, a lesser degree of posterior elevation was observed in the DS group. This may be related to the younger mean age of the cohort with DS, small sample size or diagnostic criteria. The authors concluded that the corneal features analysed in the DS cohort were in the range of normal to mild keratoconus.
We would like to further highlight some of the challenges associated with image acquisition when performing corneal topo/tomography in patients with DS. Some of the ophthalmic manifestations such as slanted and small palpebral apertures, nystagmus and strabismus can affect fixation. We have also observed additional common behavioural responses that affect fixation and alignment; patients squeezing the eyes shut in response to the examiner touching the eyelids or involuntarily opening the mouth when asked to keep the eyes wide open.
Misaligned fixation while acquiring corneal tomography images is known to result in false keratoconus features. In addition to the reported overlap in corneal features in DS and ke...
Misaligned fixation while acquiring corneal tomography images is known to result in false keratoconus features. In addition to the reported overlap in corneal features in DS and keratoconus, fixation misalignment combined with sub-optimal quality scans may affect the reliability and repeatability of corneal topo/tomography in this population and poses challenges in diagnosing and assessing progression of keratoconus. The latter is particularly pertinent when considering the indication for corneal collagen cross-linking in patients with DS. Vega-Estrada et al have very usefully highlighted the limitations in diagnosis of keratoconus in DS and contributed to the resolution of this important issue.
1. Vega-Estrada A, Fariselli C, Alio JL. Posterior corneal features in patients with down syndrome and their relation with keratoconus. Br J Ophthalmol Published Online First: 2 Mar 2020. doi:10.1136/bjophthalmol-2019-314939.
2. Alio JL, Vega-Estrada A, Sanz P, et al. Corneal morphologic characteristics in patients with down syndrome. JAMA Ophthalmol 2018;136:971-8.
3. Belin MW, Khachikian SS. An introduction to understanding elevation‐based topography: how elevation data are displayed–a review. Clin Exp Ophthalmol 2009;37:14-29.