BIOMETRY, ASCAN, KERATOMETRY - Copy.pptx

THIS IS VERY ADVANCED KIND OF PPT WHICH HAS ONLY KEYWORDS NOT FULL SENTENCES WHICH IS PREPAIRED BY VERY HIGHLY EXPERIENCED OPTOMETRIST.
THIS PRESENTATION ONLY DISCUSSES ABOUT A SCAN AND KERATOMETRY.
THERE IS A PRESENTATION ABOUT BIOMETRY INSTRUMENT WHICH IS VERY USEFUL INSTRUMENT IN OPHTHALMOLOGY DEPT.

1. BIOMETRY PRESENTER -HEMANT KUMAR(TECH.OFFICER OPHTHAL).

2. AGENDA

3. KERATOMETRY

4. KERATOMETRY-INTRODUCTION

5. CLINICAL USES OF KERATOMETER

6. Keratometry is based on the fact that the anterior surface of cornea acts as a convex mirror & the size of image formed varies with its curvature. The greater the curvature of cornea ,lesser the image size. PRINCIPLE

7. TYPES OF KERATOMETER.

8. BAUSCH &LOMB KERATOMETER

9. PROCEDURE OF KERATOMETRY

10. INSTRUMENT ADJUSTMENTS(CALIBRATION )

11. PATIENT ADJUSTMENT

12. FOCUSING OF MIRE

13. FOCUSING OF MIRE

14. A-SCAN-INTRODUCTION

15. Continue ….

16. Explained with video. CALIBRATION & PROCEDURE

17. FORMULAE FOR CALCULATING IOL POWER

18. ARE YOU USING 5-G(GENERATION) MOBILE??

19. Where, P is the IOL power in dioptres . r is the average corneal radius in mm. a is the AL in mm. d is the assumed post –operative ACD +Corneal thickness. 1 ST G-THEORETICAL FORMULE 1).BINKHORST FORMULA p =1336(4r-a)/(a-d)(4r-d).

20. 1 ST G-THEORETICAL FORMULE 2).COLENBRANDER-HOFFER FORMULA p ={1336/a-d-0.05}-1336/(1336/K)-d-0.05 Where, P is the IOL power in dioptres . K is the average K in Dioptre . a is the AL in mm. d is the assumed post –operative ACD +Corneal thickness.

21. 1 ST G-THEORETICAL FORMULE 3). GILL’s FORMULA p =129.40+(108*K)+(-2.79-Leye)+(0.26*LCL)+(-0.38*Ref) Where, P is the IOL power in dioptres . K is refractive power of cornea in dioptres . Leye is the AL in mm. LCL is the distance of apex of anterior corneal surface to apex of IOL in mm. Ref is the desired post-operative refraction.

22. 1 ST G-THEORETICAL FORMULE 4).CLAYMAN’S FORMULA

23. 1 ST G-THEORETICAL FORMULE 5).FLODOROV’S FORMULA p =(1336-LK)/(L-C)-CK/1336 Where, P is the IOL power in dioptres . L is the AL in mm. K is refractive power of cornea in dioptres . C is the estimated post-operative ACD

24. PROS & CONS OF 1 ST G-THEORETICAL FORMULAE

25. 1 ST G-REGRESSION FORMULAE 1). SRK-1 FORMULA p =A-2.5L-0.9K Where, P is the IOL power in dioptres . A is the constant specific for each lens. L is the AL in mm. K is average keratometry in dioptres .

26. 2 ND G-THEORETICAL FORMULE 1). MODIFIED BINKHORST FORMULA Binkhorst in 1981 improved the prediction of effective lens position (ELP) by using a single variable predictor,the AL, as a scaling factor for ELP and presented a formula to predict better ACD.

27. 2 ND G-REGRESSION FORMULA 1). SRK2 FORMULA P=A-2.5L-0.9K If L is <20mm: A=A+3.00 If L is 20.00-20.99mm: A =A+2.00 If L is 21-21.99mm: A=A+1.00 If L is 22-24.50mm A=A If L is >24.50mm:A=A-0.50

28. 2 ND G-REGRESSION FORMULA 2).MODIFIED SRK 2 FORMULA P=A-2.5L-0.9K If L is <20mm: A=A+1.50 If L is 20.00-20.99mm: A =A+1.00 If L is 21-21.99mm: A=A+0.50 If L is 22-24.50mm A=A If L is 24.50mm -26.00mm:A=A-1.00 If L is >26.00mm:A=A-1.50

29. Most of the 3 rd generation formulae are a hybrid of both theoretical and regression formulae. 3 RD G- FORMULE

30. 4 TH G-FORMULE

31. 5TH G-FORMULE

32. NEWER IOL POWER CALCULATION FORMULAE

33. BARRETT TORIC CALCULATOR

34. CHOICE OF FORMULAE CIRCUMSTANCE HOLLADAY 2/HOFFER Q AL <20mm HOFFER Q AL 20-22mm SRK/T,HOFFER Q,HOLLADAY AL 22.00-24.50mm HOLLADAY 1 AL 24.50-26.00mm SRK/T AL >26.00mm USES OF DIFFERENT FORMULE

35. PAEDIATRIC IOL

36. Theory and practice of OPTICS and REFRACTION Fifth Edition by A.K khurana . Srishty sen ; koushik tripathy.Ultrasound Biometry –National library of Medicine. Dupe S.Ademola-popoola ;Comparison of ocular biometry measurements by immersion A-SCAN techniques-journal of current Ophthalmology. THANKS REFERENCES