OPTICAL COHERENCE TOMOGRAPHY IN GLAUCOMA Presentation.pptx

Optical Coherence Tomography

1. OPTICAL COHERENCE TOMOGRAPHY BY NDUKWE OLUCHI 1 5 / 9 6 7 4 5 IBEH ANGELA CHIDINMA 1 5 / 9 7 6 4 6 DEPARTMENT OF OPTOMETRY FACULTY OF HEALTH SCIENCE ABIA STATE UNIVERSITY , UTURU DECEMBER 2 2 1

2. TABLE OF CONTENTS • Introduction • Applications of OCT in Glaucoma • Monitoring of Glaucoma progression using OCT • O C T Interpretation • P r e c i s i o n of early diagnosis of Glaucoma • Management of Glaucoma progression using OCT • Conclusion

3. INTRODUCTION • Optical coherence tomography (OCT) is a non-invasive diagnostic technique that renders an in vivo cross-sectional view of the retina. • I t utilizes a concept known as interferometry to create a cross-sectional map of the retina that is accurate to within at least 10-15 microns. • With an OCT, doctors can see a cross-section or 3D image of the retina and detect the early onset of various eye conditions and eye diseases such as macular degeneration, glaucoma, and diabetic retinopathy (the top three diseases known to cause blindness). • It could detect problems in the eye prior to any symptoms being present in the patient.

4. O P T I C A L C O H E R ENCE T O M O G RAPHY

5. • Glaucoma is an optic neuropathy with characteristic optic nerve appearance and visual field loss. Elevated intraocular pressure (IOP) is one of the main risk factors. • This characteristic optic nerve appearance results from glaucomatous structural changes, usually preceding functional deterioration (visual field loss). • Glaucoma is the most common cause of irreversible blindness and the second leading cause of blindness worldwide. •Glaucoma is a progressive disease that causes irreversible damage to the retinal ganglion cells and their axons, altering both structure and function.

6. APPLICATIONS OF OCT IN GLAUCOMA R N F L t h i c kness m e a s u r e ment : T h i s i s g r a p h e d i n T I S N T o r i e ntation a n d c o m p a r e d t o a g e m a t c h e d n o r m a t i v e d a t a . D e c r e a s e i n R N F L thickness r e p r e s ent g l a u c oma . O N H a n a l y sis : D i s k m a r g i n s a r e o b j e c t i v e l y i d e n t ified b y u s i n g signal f r o m a n d o f R P E . M a c u l a r t h i c k ness a n a l y sis : T h i n n i ng o f m a c u l a r m a y r e f l ect g l a u c o m a t o u s l o s s . G l a u c o m a p r o g r e s s ion a n a l y s i s u s e d t o e v a l uate t h e association b e t ween t h e a v e r a g e R N F L thickness a n d a g e . I

7. MONITORING OF GLAUCOMA PROGRESSION USING OCT • T h i s relied heavily on clinical assessment of the optic nerve, comparison of disc photos over time and visual field analysis , although these remain critical elements of glaucoma evaluation they are still subjective and qualitative , limiting their ability to detect progression . • Checking the structural changes and damages which become evident earlier than the functional changes . • Thorough assessment a n d a n a l y s i s of p a t i e n t data or result by looking at the superior and inferior temporal quadrants , look for changes greater than 1 microns . • Checking for loss of tissue due to ageing .

8. • M o n i t o r the arcuate shaped changes in macular thickness . • Check if there is any sudden change in the thickness of the RNFL , if there is then look out for schisis cavities ie hollow areas . • Checking through the circumpapillary scan • This help to detect glaucoma and how it progresses . The link between the RNFL and the ganglion cells with the extension of the ganglion cells into the inner plexiform layer , the inner retinal layers are combined when analyzing the thickness .

9. I N T E R P R E T A T I O N O F O C T I N G L A U COMA R E P O R T OCT provides a wealth of information; therefore, a systematic approach to interpretation of the outcome reports is required to make the most from its utilisation. Across manufacturers, the common element of reporting data is the use of statistical comparison of thickness measures to a normal population database and representing this with green, yellow and red backgrounds. Thickness measures falling within 95% of normal limits are shown in green, measures occurring within 5% of normal limits are i n yellow, and those occurring in ≤1% are highlighted in red. When interpreting reports, it is important to initially assess whether the data you have captured are corrupted by any errors or artefacts. while interpreting the OCT reports , the following should be consider • Signal strength : Low signal strength causes artificial thinning of the RNFL and affect the diagnostic and monitoring ability of the OCT .

10. • Accuracy of segmentation : If not accurate , it will cause the OCT to be unable to distinguish the retinal layers . • Presence of artefacts : Th e s e ( h e a d t i l t , b l i n k i n g , e y e m o v e m e n t s a n d s c a n c e n t r a t i o n i s d u e s ) will cause false identification of abnormal scans . • The common element to any macular thickness analysis is a comparison between inferior and superior hemispheres between the eyes . In macular assessment by OCT for glaucoma diagnosis , Sung et al concluded that ganglion cells layers measures are generally inferior to RNFL measures in diagnostic capability but can be useful in specific cases .

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12. The A part is the fundus image with RNFL segmentation and sectoral eye asymmetry . • The B part shows RNFL thickness profile . • The C part is the pie charts that shows the average RNFL thickness compared with the normative data

13. The precision of Oct in Early Diagnosis of Glaucoma V arious studies on OCT (Tarek et al. 2009, Schuman 1998, Leung et al. 2009) have shown that : Measurement of RNFL thickness with OCT has been reliable in discriminating normal from glaucomatous eyes. OCT has good sensitivity and specificity for differentiating normal from glaucomatous eyes. A study by Chang et al. showed Stratus OCT sensitivity and specificity for average RNFL abnormal at the 5% level and at 1% level a l s o Cirrus OCT s h o w e d sensitivity and specificity for average RNFL abnormal at the 5% level and at the 1% level (Chang 2009)

14. THINGS TO AVOID WHILE DOING OCT IN GLAUCOMA PATIENTS • Make sure all the scan are of similar quality . • Beware of false positive • Look at raw OCT images to avoid being fooled by artefacts . • Beware of thickness changes caused by Uveitis • Do not be fooled if visual field changes but OCT does not change

15. Oct in Glaucoma Management Clinical examination of the optic nerve, and achromatic automated perimetry is the gold standard for the management of glaucoma. B y evaluation of the optic nerve structure, particularly for preperimetric glaucoma. Although each OCT platform has its specific scan protocols and analyses that are not directly comparable with each other, at a bare minimum. Circumpapillary retinal nerve fiber layer (RNFL), and macular scans must be performed to confirm that a patient has glaucoma and to understand the extent and topographical distribution of structural damage present.

16. C O N C L U SION Medicine and technology are advancing hand in hand to provide quality health care. Technology innovation, and improvement will continue to impact health services.OCT is a new technology w h i c h ntroduces both difficulties and opportunities.The lack of a large-scale normative database is perhaps the most significant issue in interpreting OCT results at this point. These issues must be resolved before OCT can be accepted for widespread clinical use in glaucoma.Apart from this note of caution, the potential utility of OCT as a glaucoma diagnostic tool is extremely high as adequate data exist to evaluate the patients in conjunction with other clinical parameters. A patient can be followed over time, using his or her baseline. The patient's two eyes can be compared for asymmetry, and a single eye can be examined for focal or sectoral NFL thinning.