Pachymetry.pptx thickness of cornea of the eye

Pachymetry it's about thickness of cornea

1. Pachymetry Henok B 1 10/14/2025

2. Outline Defn of pachymetry Types Principle Indication 10/14/2025 2

3. Objectives At the end of this lesson you are expected to: Define what pachymetry is List the types of pachymetry Explain the principle of pachymetry List indications of pachymetry 10/14/2025 3

4. brainstorming Layers of cornea Normal corneal thickness 10/14/2025 4

5. Pachymetry Pachymetry Pachos = Thick Metry = to measure Indicator of health status of the cornea specially corneal endothelial pump function 5 10/14/2025

6. Pachymetry Corneal pachymetry  is the process of measuring the thickness of the cornea Several methods are available to obtain reliable and reproducible measurements of corneal thickness.  Contact methods, such as ultrasound and confocal microscopy noncontact methods such as optical biometry with a camera or Optical Coherence Tomography (OCT) 6 10/14/2025

7. Principle: instrument functions by measuring the amount of time needed for the ultrasound pulse pass from the one end of transducer to the decrement membrane and back to the transducer. Corneal thickness= transit time *propagation velocity/2 Speed of sound in cornea= 1640m/sec 10/14/2025 7

8. Pachymetry The most commonly used approach is ultrasonic pachymetry . Ultrasonic pachymetry is an efficient and accurate way to measure corneal thickness; however, the probe must touch the corneal surface and topical anesthesia is thus required. Its accuracy is dependent on the perpendicularity of the probe's application to the cornea 8 10/14/2025

9. Component Probe handle: piezoelectric crystal that emit ultrasound wave Transducer: send and receive ultrasound to and from the cornea Tip. Not more than 2mm 9 10/14/2025

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11. Pachymetry The central corneal thickness measurements are higher with non contact than with contact ultrasonic pachymetry . This disparity between instruments can result from their distinct methodologies. The noncontact system measures the hydrated mucous component of the tear film over the cornea; contact ultrasonic pachymetry does not 11 10/14/2025

12. What is normal? Central 490µm to 560µm More than 700 µm indicates endothelial decompensation Peripheral 630 µm to 670 µm Peripheral corneal thickness is asymmetric the temporal thinnest at the temporal 12 10/14/2025

13. Pachymetry Corneal pachymetry medically necessary for the following indications: Bullous keratopathy ;  Corneal edema;  Corneal refractive surgery (pre- and post-operative evaluation) Corneal transplant (penetrating keratoplasty ) (pre- and post-operative evaluation) Evaluation of complications of corneal refractive surgery Evaluation of corneal rejection post penetrating keratoplasty Fuchs' endothelial dystrophy Persons with glaucoma or glaucoma suspects Posterior polymorphous dystrophy 13 10/14/2025

14. Factors affecting CCT Higher in young, male and diabetics Thinner in blacks than whites CCT does not correlate with refraction 14 10/14/2025

15. Thank you 10/14/2025 15