What Is The Real Benefit Of Femto- Lasik Compared To Microkeratome Lasik?

Transcription

1 What Is The Real Benefit Of Femto- Lasik Compared To Microkeratome Lasik? M. Sameh El-Agha, MD, FRCS(Ed) Cairo University 2 nd Annual EFCRG Course and Meeting April 30-May 1, What s wrong with microkeratome lasik? Excellent results in the overwhelming majority of cases Much better safety features as years progressed (ACS, Hansatome, M2) Most of us are comfortable with one or more time-tested microkeratomes (Moria M-2 and/or SBK) 2 1

2 Is that always the case? Buttonhole:- Ks > 45 D Free cap:- Ks < 41 D 3 Pre-op K s not an issue with femto 4 2

3 Flap thickness: intended versus achieved (courtesy of Dr. Noha Khaleel, Cairo Univ.) Intended flap thickness 90µ in both cases Microkeratome : actual thickness 121 µ Femto: actual thickness 93 µ 5 Flap architecture 6 3

4 What are the implications of flap architecture More predictable central flap thickness ensures greater safety in borderline corneas Planar flap causes less loss of biomechanical strength A thin planar flap causes less severing of nerves (less dry eye) SBK is an exception! عشان خاطر د/يحيى صالح! Green: Femto cut Red: Microkeratome cut 7 What are the implications of flap architecture Vertical side cut:- Man-hole cover effect Less chance of flap slippage Less chance of striae Green: Femto cut Red: Microkeratome cut 8 4

5 The inverted flap edge Allows even tighter fit of the flap Studies have shown greater preservation of biomechanical strength of the cornea compared to the vertical side cut (?) 9 Flap diameter (and centration) Too small: Inadvertent ablation of epithelium or hinge Undercorrection with hyperopic and astigmatic ablations May stimulate epithelial ingrowth Too large: Injury of limbal blood vessels (bleeding, DLK) More severe dry eye Larger flaps may be more tricky to reposit 10 5

6 Flap control with Femto Ability to modify: Flap diameter Flap location DURING APPLICATION OF SUCTION Eliminates:- Oversized/undersized flaps Decentered flaps 11 Flap shape Ability to customize flap shape An ovoid flap may be useful in Hyperopia With-the-rule astigmatism 12 6

7 Loss of suction Must abort procedure Reposit flap as best as possible Place CTL Cannot repeat procedure before at least 6 weeks (optimum 3 months) GREAT DISAPPOINTMENT! 13 Loss of suction not an issue with femto Loss of suction not an issue Wait for air bubbles to disappear May repeat procedure on the same day 14 7

8 Use of femto in retreatments May customize flap diameter/depth based on corneal OCT To completely avoid disturbing the old flap:- Cut deeper Plan a larger flap than the old one Practically not feasible due to limitations of residual corneal thickness 15 More practical approach:- New side cut WITHIN the old flap Eliminates the difficulty of finding the old edge Allows a clean entry into the original plane of cleavage Less chance of epithelial ingrowth:- No epithelial disturbance Tighter flap adherence 16 8

9 To summarize Microkeratome LASIK is fine for:- Thick corneas with no biomechanical issues Normal K-readings (41-45 D) Normal corneal diameter Adequate tear film (i.e. younger patients, no ocular surface issues) 17 When is femto clearly better? Borderline corneal thickness (thin planar flaps ± inverted flap edge) K s flatter than 41 D (eliminates free cap) K s steeper than 45 D (eliminates button holes) Dry eye (use smaller diameter, thinner flap) Hyperopia (predictably large flap eliminates inadvertent ablation of epithelium around flap) High astigmatism (same as hyperopia) Small corneas (white-to-white less than 11mm) Retreatments after old LASIK 18 9

10 Is there still a place for microkeratome? YES, YES, YES Cheaper Works very well in a majority of cases Microkeratome flaps are much easier to lift than femto flaps Superior to femto in the presence of old incisions in the cornea (post-pkp, post-rk) Microkeratomes create a smoother flap bed with:- Quicker visual rehabilitation Less postoperative inflammation Less need for postoperative steroids 19 Conclusion Femto Advantages:- Greater safety Greater control over flap dimensions and edge configuration Femto Disadvantages:- Some intraoperative difficulty in lifting the flap Some delay in visual recovery Expense 20 10

11 Conclusions THE CHOICE BETWEEN FEMTO AND MICROKERATOME ULTIMATELY DEPENDS ON THE SURGEON S JUDGEMENT, EXPERIENCE, AND COMFORT 21 11