Tomography-based definition of keratoconus for Down syndrome patients

Abstract

Background To assess the diagnostic ability of Pentacam HR (Oculus Optikgeräte, GmbH, Wetzlar, Germany) tomographic indices in discriminating keratoconus (KC) and KC suspect (KCS) in 10- to 30-year-old patients with Down syndrome (DS). Methods In this study, DS patients were enrolled through special needs schools, the National Down Syndrome Society, and relevant non-profit organizations. Diagnoses were made independently by two experienced specialists. Forty Pentacam indices related to corneal thickness, volume, density, keratometry, power, shape, aberration, and elevation were extracted. For each index, the accuracy for KC and KCS diagnosis was evaluated using discriminant analysis and the area under receiver operating characteristic curve (AUROC). From each enrolled case, data from only one eye was entered in the analyses. Results Analyses were performed on data from 25 KC, 46 KCS, and 154 non-ectatic DS eyes. The best discriminants for KC were anterior higher order aberrations (HOA) (cutoff > 0.643, AUROC = 0.879), posterior vertical coma (cutoff > 0.0702 μm, AUROC = 0.875), anterior vertical coma (cutoff > 0.4124 μm, AUROC = 0.868), and total HOA (cutoff > 0.608, AUROC = 0.867). The difference between AUROCs were not statistically significant (all P > 0.05). For KCS, the best discriminants were minimum corneal thickness (cutoff ≤ 480.0 μm, AUROC = 0.775), corneal volume (cutoff ≤ 55.3 μm, AUROC = 0.727) and Belin Ambrosio display-total deviation (BAD-D) (cutoff > 2.23, AUROC = 0.718) with no significant difference between AUROCs (all P > 0.05). Conclusions In this sample of DS patients, best KC discriminators were HOA and coma which showed good diagnostic ability. For KCS, best predictors were minimum corneal thickness, corneal volume, and BAD-D with relatively good diagnostic ability. Defining a new set of KC diagnostic criteria for DS patients is suggested.

Corneal biomechanical changes in allergic conjunctivitis

“…The 30 AC patients in our study could not be diagnosed with KC because none had the typical clinical signs specific for KC. However, according to the tomographic criteria for KC diagnosis as described by Asgari [ 29 ], including Kmax > 48.0 D, ART-max < 339 μm, I-S value > 1.4 D, BAD-D > 1.6, and posterior elevation, 8 patients in our study met the tomographic criteria for KC. Among them, 1 patient met three criteria (ART-max, I-S value and BAD-D), 2 patients met two criteria, and the other 5 patients met one criterion.…”

Corneal characteristics in Down syndrome patients with normal and keratoconic cornea

“…In fact, due to these similarities, it is very difficult to discriminate mild KC from the normal pattern in DS patients. In a previous report (13), we showed that among corneal indices, MCT, corneal volume, and BAD-D had a relatively good diagnostic ability in DS patients and the diagnostic power of these indices for detecting KC was not as excellent as their power in non-DS subjects. Also, HOA and coma were the best discriminators.…”

Down syndrome: a review of ocular manifestations

“…In particular, these patients have thinner and steeper corneas than healthy individuals, which likely contributes to the development of keratoconus in this population. 71 , 84 , 85 Haugen and Hovding 40 previously examined a young adult population of patients with Down syndrome and found a reduced corneal thickness (0.48 ± 0.04 mm; range 0.40–0.57) compared to the general population (0.55 ± 0.03 mm; range 0.49–0.64). Furthermore, they found higher keratometry values, thinner lenses, and weaker lens power compared to controls.…”

“…The authors also proposed that topographical tools may be of import in developing diagnostic criteria for Down syndrome patients. 84 …”

“…91 Topographical screening tools New screening techniques and three-dimensional methods have been shown to accurately quantify and diagnose keratoconus, leading to earlier identification and treatment. 84,92,93 Because there are few to no signs or symptoms of early keratoconus, enhanced diagnosis is important in the Down syndrome population. By utilizing corneal topography and detection metric parameters, tools such as TMS-4N (Tomey) and Pentacam HR (Pentacam HR, Oculus, Wetzlar, Germany) tomography have demonstrated potential in diagnosing and screening for keratoconus.…”