1. Microkreratome – Related LASIK complications Farid Karimian M.D 2002

2. Thin flaps & Buttonholes Causes: - The most common cause: Inadequate suction - Corneal anatomy: despite IOP>65 mmHg during pass Steeper (>46D) corneas: buckling of cornea tissue Flat (<41D) cornea Previous PKP High Astigmatism - Poor blade quality: irregular cuts with thin areas - Microkeratome malfunctions, pass must be continuous regular

4. Thin- flaps & Buttonholes …Results - Inability to perform laser ablation - Risk of epithelial ingrowth - Risk of irregular astigmatism - If LASIK performed later flap must be recut

5. Thin flaps & Buttonholes … prevention - Do not make the microkeratome pass if adequate IOP not verified - Advise the patients with unusually high or low KR of increased risk - Consider using deeper depth plate on steep corneas ( with low corrections) - Provide gentle downward support on the microkeratome handle during pass - Check the microkeratome prior to each use - Use a sharp, new blade for each patient

6. Thin flaps … management - Replace the thin ( or bottonholed ) flap - Carefully manage the epithelial edge - Inspect the flap meticulously, check adherence - Laser ablation may not be done - Recut the flap with a thicker depth plate later ( 2-3 mo)

7. Free Cap Causes: - Failure to advance the stopper sufficiently on ACS - Corneal anatomy: large and flap (KR < 41. OD ): smaller area of cornea presentation - Loss of suction during pass - Inform the patient with flat cornea risk of flap complications - Results: - Free cap - Keep the cap in anti- desiccation chamber ablation can be done

8. Free cap … Prevention - Check the entire microkeratome assembly - Put corneal marks to aid in proper cap replacement - Warn patients with large, flat corneas

10. Free cap … Management - Place the free cap in anti- desiccation chamber do ablation - Carefully replaced the cap stromal side down adjust preop corneal marks - Assure flap adherence by waiting 3-5 min after replacement - In most cases sutures are not necessary - If there is CED; bandage CL may be placed

11. Incomplete Pass Causes: - poor exposure: abstruction by drapes, lid or speculum - Debris or conjunctiva on suction ring tracks - Improper assembly or cleaning of the microkeratome: Intolerable friction Results: - Inability to proceed with the ablation if the pass stops within the central 6 to 7 mm zone - If the flap edge is within central 5 mm, the ablation cannot be performed Reposition the flap

13. Prevention of Incomplete pass Use proper techniques to ensure adequate exposure, including lateral canthotomy in rare cases Careful assembly, cleaning and inspection of microkeratome and suction ring prior to each use surgeon and nurses must be familiar

14. Run the microkeratome through a complete forward and reverse cycle prior to each eye to ensure proper functioning Avoid excess fluid prior to microkeratome use BSS crystals lead to motor head dysfunction in subsequent cases Restart forward movement with the Hanstome. Never reverse and forward or stop - and - start with ACS

15. Incomplete pass … Management If proceeding with laser ablation shield the hinge with a sponge If unable to perform ablation ( if the pass stops within the central 5 mm) replace the flap and recut at a later date ( e.g. 3 mo)

16. Corneal perforation - Rare, but devastating complication Cause: - Improper microkeratome assembly: missed depth plate into ACS - Severe trauma to cornea, iris and lens Prevention: Careful checking the depth plate by surgeon

17. Corneal perforation… Management: - Dependent on depth of cut - Lost depth plate may lead to PK and IOL implantation - Patients must be informed preoperatively about this rare sight- threatening complication