Refractive surgery basics . review of the basics of refractive surgery including exam, pupil, lasik , optics

1. “REFRACTIVE SURGERY
BASICS”
Michael Duplessie, MD

2. The Preoperative Visit
• REFRACTION:
–Manifest with binocular balance
–Cycloplegic Refraction
• Tropicamide vs. cyclogel

3. Keratometry/Topography
• Not to flat and not to steep
• Plan: MR*0.6 = anticipated change in
myopic refraction with excimer treatment
(less than 36 is contraindication)
• Plan: MR*1.0 = anticipated change in
hyperopic excimer treatment (more than 50
is contraindication)
• Rule out corneal distortion/KC/CL warpage

4. Topography

5. Pupils
• Historically, smaller ablation zones resulted
in significant spherical aberration following
surgery
Ablation Zone
6.0 mm
Pupil Size
7 mm

6. Pupils
• Current technology reduces the problems
associated with pupil size
– larger ablation zones
– blend zones
a. 8 mm with myopes on VISX
b. 9 mm with hyperopes on VISX
• Glare/halos results from induced HOA’s
regardless of pupil size
• Still considered standard of care

7. Pachymetry
• Ultrasound is standard
–Central readings necessary
–Utilize intraoperative stromal bed
measurements
• Orbscan tends to be thinner

8. Munnerlyn’s Formula
• 11 microns*MR (at 6 mm) = ablation depth
• Pachymetry – ablation depth – flap
thickness = GREATER THAN 250
MICRONS
• Larger ablation zones (6.5 or 7 mm) will
remove MORE tissue

9. General eye health
• Dry eye
• Lid disease: Blepharitis, Meibomian gland
dysfunction
• Corneal scars/ABMD/neovascularization
• Acne Rosecea
• Glaucoma with or without field defects

10. Systemic Disease
• Diabetes with or without DR
• Arthritis
• Thyroid (tendancy for dry eye)
• Medications: more than one psychiatric
med? Watch out
• Personality: more than two drug allergies
or more than three rings

11. Consent form
• Legal document which describes risks and
benefits of the procedure.
• We do this for all patients at the
preoperative visit.

12. Day of surgery
• Bring meds: Antibiotic, Steriod and
Valium
• Valium (0.5 mg PO taken 30 minutes prior
to surgery)
• Dress in layers (Suite is cold)
• No perfume or scented lotion
• Testing performed: Machines, consent
discussion and meet with Dr. Duplessie

13. Making the flap
• Microkeratomes have come a long way
since the ACS
– 3 parts
– Track
• Problematic incision
– Blind incision (some exceptions)

14. Disadvantages to Traditional
Microkeratomes
• Irregular flap thickness
• Irregular flap diameter
• Free flaps
• “Track marks” in stromal bed
• Epithelial ingrowth

15. Flap Tear

16. Superficial Scarring

17. Flap complications Using
Traditional Microkeratomes
• Button-hole flaps
• Thin flaps
• Torn flaps
• Decentered flaps
• Incomplete flaps

18. The All-Laser Method
• The Intralase FS laser combined with
excimer laser
• CDRH CFR1040 class IIIb ophthalmic laser
• Long wavelength 1053 nm not absorbed by
tissue
• Indicated for the use in patient’s requiring
lamellar resection of the cornea

19. Mechanism of Action
• The laser defines resection
planes through femtosecond
laser pulses that photodisrupt
tissue with micron-scale
precision.
• Resection is achieved by precise
placement of
microphotodisruptions scanned
at high repetition rates controlled
by computer.

20. Tailoring the flap to each patient
• Unlike traditional
microkeratomes,
the Intralase allows
the surgeon to
specify the
architecture of the
flap

21. Tailoring the flap to each patient
• Flap diameter: range of 0.1-10.00 mm
• Flap thickness: range of 0-400 µm
• Hinge angle: 45-90 degrees
• Hinge position: 360 degrees
• Side cut angle: 30-90 degrees

22. Complications using Intralase
• Thin flaps
• Torn flaps; flaps are incompletely cut by
laser on every case
• Decentered flaps
• Incomplete flaps
• Prolonged vacuum time

23. Resurface the eye
• Typical limits :
– Myopia 10D
– Hyperopia 4D
– Astigmatism 4D
• Wavefront or no wavefront????

24. Custom Parameters
WaveScan Hyperopia Myopia
Sphere +3.75 -6.50
Cyl +2.75 -3.50
WaveScan
SE
+3.75 -6.50

25. Review Post-op instructions
• Steriod/Antibiotic: Tobradex 4x/day x 5
days
– Artificial tears FREQUENTLY – Q15min
while awake week #1, Q30 min week#2 then
hourly
• Gel QHS as needed for AM dryness

26. Common Side Effects
• Dry eye
• Night glare (warn Custom patients)
• Hyperopia treatment within first month:
• Soft CL EW with Acular (NOT Acular LS)
QID
– RTO 2 weeks

27. Light Sensitivity
• Onset: first weeks to several months later
• It will resolve with further healing but if
patient complain, treat it
• Topical steroids “4/3/2/1 x 1 week”
• Acular QID x 1 week

28. Slow healing/Persistent Edema
• Steroids 4/3/2/1 x 1 week
– Maxidex (Dex
– Pred Forte (prednisilone acetate)
– Lotemax (loteprednal acetate)
• Muro 128 solution QID
• Acular LS QID x 1 week

29. Flap Dislocation

30. Fibers

31. Diffuse lamellar keratitits
• Typically at edge, moves centrally
• Treat immediately! Heavy steroids – Pred
preferred
• May require relifting and cleaning
• If stria develop, long term visual importance
1. Tissue destruction
2. Distortion of vison and loss of BVA
3. Hyperopia shift
• Monitor closely in patients with abrasions, flap
trauma

32. DLK

33. Central DLK

34. Epithelial Ingrowth

35. Epithelial Ingrowth

36. Epithelial Ingrowth

37. Enhancements
“Touch ups”
• 20/40 or less
• Significant improvement subjectively?
• Warn low myopes about loss of vision at
near if over 40
• Rule out ectasia in high myopes/thin
pachemetry
• Warn patient they may be more
uncomfortable after numbing drops wear off

38. Custom Enhancements
WaveScan Hyperopia Myopia
Sphere +1.00 +1.00
Cyl -1.00 -1.00
WaveScan SE +1.00 +1.00

39. Monovision
• Patients who have worn it in the past are
most successful
• Trial frame: if like trial, will be successful
• If don’t like TF, go distance OU
• Deep monovison causes anisometropia in
spectacles