Back to Blog
Por 15 pellucid clear coat5/30/2023 ![]() ET mapping is increasingly recognized as a sensitive tool for the diagnosis of ocular surface disorders. Moreover, anterior segment optical coherence tomography (AS-OCT) creates cross-sections, which can be generated into a three-dimensional structure to produce corneal epithelial thickness (ET) measurements. Α confocal microscopy system, which is a novel clinical technique for the study of corneal cellular structure, could contribute effectively towards the same direction. A non-invasive air pulse tonometer in conjunction with an ultra-high-speed Scheimpflug camera complements tomographic findings by analysing biomechanical corneal properties. Moreover, Scheimpflug cameras (corneal tomographers) which analyze both, anterior and posterior corneal surface, curvatures, pachymetry, elevation data, higher order aberrations, Fourier analysis of keratometric data and corneal density became the most promising tools for diagnosis and follow-up of ectatic diseases. Corneal topography has been used in the last decades as the main tool for imaging in ectatic corneal diseases. Aim of this work is to discuss contemporary techniques and findings to assist physicians in finding the correct diagnosis. Biomicroscopic findings cannot always give all the information needed to distinguish KC from related ectatic corneal conditions. ![]() In severe cases, the extended area of corneal thinning also complicates the differentiation. In early cases, however, the differential diagnosis may be more challenging since the cornea may look relatively normal. In moderate cases of KC, the differentiation is typically possible based on slit-lamp examination and corneal tomography with evaluation of the location of the corneal thinning region. The most relevant corneal pathologies that may imitate the tomographic KC pattern are Pellucid Marginal Degeneration (PMD), Keratoglobus, Posterior Keratoconus and Fuchs Terrien’s Marginal Degeneration (FTMD). FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.ĭistinguishing Keratoconus (KC) from other corneal ectatic diseases and thinning disorders is essential for a stage-appropriate and suitable management of each condition. Asphericity and Avg NT((D))/IS((D)) were clinically relevant in discriminating PMD from other groups. CONCLUSIONS: The PMD index appeared to be highly sensitive and specific for diagnosing PMD. The PMD index (AROC curve, 0.935), with a cutoff of 3.45 or higher had 90% sensitivity and 93.7% specificity to distinguish PMD from keratoconus and had 100% sensitivity and 100% specificity to distinguish PMD from control eyes, with a cutoff of 2.46 or higher (AROC curve, 1.000). The highest area under the receiver-operating-characteristic (AROC) curve in discriminating PMD from keratoconus was for asphericity (0.974 cutoff ≥-0.07 sensitivity 93.3% specificity 90.6%) followed by the ratio of average power values of the nasal and temporal quadrants to the average power values of the inferior and superior quadrants (Avg NT((D))/IS((D))) (0.959 cutoff ≥1.005 sensitivity 96.7% specificity 90.6%). RESULTS: Of the indices, the mean values of anterior elevation (AE), ratio of the AE to the anterior best-fit sphere, ratio of the average power values of nasal quadrant to the average power values of inferior quadrant, and difference between maximum keratometry (K) and minimum K were significantly different between the 3 groups (P<.05). These values were analyzed and compared between PMD patients, keratoconus patients, and control subjects. METHODS: Anterior and posterior corneal elevations and thickness indices were obtained from the Orbscan IIz topographer. DESIGN: Initial model-building retrospective study. SETTING: LV Prasad Eye Institute, Hyderabad, India. PURPOSE: To determine and compare corneal elevation and thickness indices, thereby formulating a reliable index to distinguish eyes with pellucid marginal degeneration (PMD) from keratoconus eyes and normal (control) eyes.
0 Comments
Read More
Leave a Reply. |