New algorithm for corneal densitometry assessment based on anterior segment optical coherence tomography.

PURPOSE: To describe a new algorithm to measure corneal densitometry based on images obtained by swept source anterior segment ocular coherence tomography (SS-AS-OCT) and establish standard densitometry values in a group of normal eyes. METHODS: A total of 111 healthy participants (195 eyes) were enrolled in this study. Using a MATLAB designed algorithm, the cornea was segmented into three layers: anterior, posterior and mid-stroma, and it was divided into two concentric areas, 0-2 and 2-4 mm, resulting in nine areas for the analysis. The mean corneal densitometry values were calculated and expressed as grayscale units (GSU). RESULTS: The mean age was 57 years (range 22-87), with 100 (51.3%) right eyes and 95 (48.7%) left eyes. The total corneal densitometry was 86.9 ± 12.1 GSU. The mid-stroma layer had the highest densitometry values, 87.4 ± 12.1 GSU, and the anterior layer had the lowest values, 81.9 ± 14.2 GSU. Densitometry differences between the anterior layer and the mid-stroma layer (P < 0.001), as well as the anterior layer and the posterior layer (P < 0.05) were statistically significant. The 0-2 mm concentric area had higher mean densitometry values, 97.8 ± 12.7 GSU, and the differences were significant compared to the 2-4 mm concentric area (P < 0.001). No correlation was found between the corneal densitometry values and gender or age. CONCLUSIONS: The new MATLAB segmentation algorithm for the analysis of corneal SS-AS-OCT images is capable to objectively assess corneal densitometry. We provide standard and normal data for better clinical and research approach.

Tomographic and aberrometric assessment of first-time diagnosed paediatric keratoconus based on age ranges: a multicentre study.

PURPOSE: To describe paediatric keratoconus (KC) patients by tomographic and aberrometric characteristics at first diagnosis, in a multicentre study. METHODS: We included 278 eyes from 139 paediatric patients, with a first tomographic diagnosis (Pentacam® ) of KC prior to 18 years old. KC classification was based on the KC Index (≥ 1.07) and Topographic Keratoconus Classification (TKC ≥ 1). Patients were divided based on age ranges (14 and under and over 14 years) and gender. Statistical analysis was performed with SPSS statistics 25.0. ANOVA factor was carried out comparing to compare groups. RESULTS: 278 eyes were screened, and 230 eyes were diagnosed with paediatric KC. Mean age was 15.48 ± 2.33 (6 to 18) years. We found differences in terms of TKC (2.08 ± 0.89 and 2.38 ± 0.82, p < 0.05) and spherical aberration (-0.71 ± 0.97 and -1.07 ± 1.36, p < 0.05) among the 14 years old or under and above 14 years old groups, respectively. Overall, female paediatric KC patients presented a more severe TKC, Belin Ambrosio Display, maximum keratometry, asphericity and primary and secondary coma aberrations compared to male KC patients. We observed a correlation between CDVA and asphericity (r = 0.71, p < 0.01), as well as between CDVA and spherical aberration (r = 0.69, p < 0.01). CONCLUSION: Our findings revealed that the debut of KC is usually in a moderate to advanced stage in the paediatric population at first diagnosis, particularly in female patients. Corneal tomography should be systematically performed in children with recent onset of corneal astigmatism.

Assessment of lower tear meniscus measurements obtained with Keratograph and agreement with Fourier-domain optical-coherence tomography.

AIMS: To compare intraobserver repeatability and interobserver and intersession reproducibility of lower tear meniscus height measurements (LTMH) obtained with the new Keratograph 5M and a Fourier-domain optical-coherence tomography (OCT; Spectralis OCT) and to assess the agreement between the two devices. METHODS: This is a observational cross-sectional study. Thirty eyes of 30 normal subjects were randomly imaged twice with both devices in our setting. Two examiners randomly made LTMH measurements using the devices. To assess intraobserver repeatability and interobserver and intersession reproducibility within-subject SD (Sw), test-retest repeatability, coefficient of variation (CoV) and intraclass correlation coefficients (ICCs) were calculated. Agreement between both devices was also determined. RESULTS: Average LMTH for Keratograph was 235.46±57.61 µm, whereas the mean LTMH measured by OCT was 245.84±67.18 µm. Intraobserver repeatability and interobserver and intersession reproducibility were moderate with Keratograph (CoV ≥0.16%, ≥0.19%, ≥0.17% and ICC ≤0.83, ≤0.76, ≤0.83, respectively) and high for the Spectralis OCT (CoV ≤0.13%, ≤0.12%, ≤0.11% and ICC ≥0.9, ≥0.92, ≥0.92, respectively). No statistically significant difference was detected in mean LMTH measurements made with both devices, although correlation was low (CoV 0.25%, ICC 0.55). CONCLUSIONS: Spectralis OCT LTMH measurements were more reliable than the new Keratograph data. Agreement between the devices was poor.