1. Anatomy and Topography Devices www.medsalesacademy.co.uk www.medsalesacademy.co.uk
Welcome to Anatomy & Topography Devices Emma Deighan ๏ Trainer in Ophthalmology for 20 Years ๏ Please ask questions! ๏ Email emma@medsalesacademy.co.uk ๏ www.medsalesacademy.co.uk
Today we will learn Anatomy - Anterior Segment ๏ Pathology - Keratoconus, scars, PMD, Dry Eye ๏ History of Topography ๏ Placido ๏ Statistics and Indices scales ๏ Scanning Slit, Scheimpflug ๏ www.medsalesacademy.co.uk
Anatomy www.medsalesacademy.co.uk
Cornea ๏ Epithelium - Protects eye from outside Epithelial cells - Regenerates every 7 days Bowman’s Membrane ๏ Bowman’s Membrane - Strong boundary layer - Prevents objects penetrating stroma ½ mm Stroma ๏ Stroma - Main body of cornea - Gives transparent properties to cornea ๏ Decemet’s Membrane Decemet’s Membrane - Basement membrane for endothelium Endothelium ๏ Endothelium - Controls water flow in and out of cornea www.medsalesacademy.co.uk
Dua’s Layer ๏ Posterior-most 10 - 20 μ m of the stroma ๏ provides a plane of cleavage in DALK. 1, 2 Dua HS, Faraj LA, Said DG, Gray T, Lowe J. Human corneal anatomy redefined: a novel pre Descemet's layer (Dua's layer). 1. Ophthalmology 2013; 120: 1778–1785. [PubMed] [Google Scholar] Dua HS, Mastropasqua L, Faraj L, Nubile M, Elalfy MS, Lanzini M et al. Big bubble deep anterior lamellar keratoplasty: the collagen 2. layer in the wall of the big bubble is. unique. Acta Ophthalmol 2015; 93: 427–430. [PubMed] [Google Scholar] www.medsalesacademy.co.uk
Cornea Dimensions ๏ Dimensions - Width ( White to White) 11.5-12.5mm - Depth (Central Corneal Thickness) 550 microns - Curvature (K readings) 43-46 D ๏ Associated Structures - Limbus - Connection between the Sclera (White of the Eye) and the Cornea www.medsalesacademy.co.uk
Anterior Chamber ๏ Made up of - Aqueous, Iris, Pupil ๏ About 2.75mm deep (3.25 if measured including the cornea) ๏ Aqueous flows to maintain eye pressure (IOP) www.medsalesacademy.co.uk
Anterior Chamber Dimensions ๏ ACD epi - from Anterior Surface of Cornea to lens Ave 3.25 • ๏ ACD endo - From Posterior Surface cornea to Lens Ave 2.75 www.medsalesacademy.co.uk
Pathology ๏ Keratoconus ๏ Scarring ๏ Graft ๏ Fuchs Dystrophy ๏ Dry eye www.medsalesacademy.co.uk
Corneal Curvature K readings ๏ K1 & K2 ๏ Only measured at specific point ๏ Today we will look at corneal curvature over the ๏ whole surface Front and Back!! ๏ www.medsalesacademy.co.uk
Topography First described by Christopher Schiener ๏ in 1619 Discovered reflecting images in a marble ๏ gave an idea of their shape Theodore Scheimpflug expanded on an ๏ idea from an Englishman to develop the Scheimpflug principle to photograph mountains www.medsalesacademy.co.uk
Topographer vs Topographer ๏ Topography - Reflected Image eg Placido ๏ Tomography - Slice images built into 3 D image eg Schiempflug www.medsalesacademy.co.uk
Placido ๏ Measures anterior surface only ๏ Reflected Image in tear film ๏ Assumes centre of pupil in the same place as fixation ๏ Assumes curvature there is zero ๏ Watch out for big noses www.medsalesacademy.co.uk
Placido ๏ However - Good for astigmatism and axis - Measuring curvature in di ff erent points www.medsalesacademy.co.uk
Placido www.medsalesacademy.co.uk
Indices www.medsalesacademy.co.uk
Pentacam Indices ISV IHA Index of surface variance Index of Height Asymmetry Variance in curvature from mean anterior Anterior Surface height compared upper corneal curvature and lower area IVA IHD Index of Vertical Asymmetry Anterior Index of Height Decentration Corneal vertical curvature compared to Value of decantation of anterior surface upper and lower areas height data in vertical meridian KI/ CKI Keratoconus Index www.medsalesacademy.co.uk
Scheimpflug vs Placido Pentacam Topographer www.medsalesacademy.co.uk
What is Scheimpflug ๏ Camera used to image the anterior segment - It is based on the Scheimpflug principle - Allows a cross sectional view of the structures - Various reports and analysis are linked to the sw www.medsalesacademy.co.uk
Scheimpflug - Scheimpflug allows greater depth of focus - Uses camera in di ff erent plane to object www.medsalesacademy.co.uk
Why is it good for the eye? Cross Section of Anterior Chamber and Lens ๏ www.medsalesacademy.co.uk
Edge Detection - Anterior surface of Cornea to posterior surface of Lens www.medsalesacademy.co.uk
3-D ๏ 3D model computed using ray tracing ๏ Eyetracker corrects small saccadic movements www.medsalesacademy.co.uk
4 Maps Refractive www.medsalesacademy.co.uk
Today we have learnt Anatomy - Anterior Segment ๏ Pathology - Keratoconus, scars, PMD, Dry Eye ๏ History of Topography ๏ Placido ๏ Statistics and Indices scales ๏ Scanning Slit, Scheimpflug ๏ www.medsalesacademy.co.uk
Thank you! We will email you some questions. ๏ Please send your questions and comments to ๏ emma@medsalesacademy.co.uk We look forward to seeing you on the next course ๏ Interpreting Basic Reports www.medsalesacademy.co.uk
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