“REFRACTIVE SURGERY BASICS”

Michael Duplessie, MD

The Preoperative Visit

• REFRACTION:– Manifest with binocular balance    – Cycloplegic Refraction

• Tropicamide vs. cyclogel

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

Topography

Pupils

• Historically, smaller ablation zones resulted in significant spherical aberration following surgery

Ablation Zone6.0 mm

Pupil Size7 mm

Pupils

• Current technology reduces the problems associated with pupil size– larger ablation zones– blend zones

a.    8 mm with myopes on VISXb.    9 mm with hyperopes on VISX

• Glare/halos results from induced HOA’s regardless of pupil size

• Still considered standard of care

Pachymetry

• Ultrasound is standard– Central readings necessary– Utilize intraoperative stromal bed

measurements• Orbscan tends to be thinner

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 

General eye health

• Dry eye• Lid disease: Blepharitis, Meibomian gland

dysfunction• Corneal scars/ABMD/neovascularization• Acne Rosecea• Glaucoma with or without field defects

     

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

Consent form

• Legal document which describes risks and benefits of the procedure.

• We do this for all patients at the preoperative visit.

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

Making the flap

• Microkeratomes have come a long way since the ACS– 3 parts– Track

• Problematic incision– Blind incision (some exceptions)

Disadvantages to Traditional Microkeratomes

• Irregular flap thickness• Irregular flap diameter• Free flaps• “Track marks” in stromal bed• Epithelial ingrowth

Flap Tear

Superficial Scarring

Flap complications Using Traditional Microkeratomes

• Button-hole flaps• Thin flaps• Torn flaps• Decentered flaps• Incomplete flaps

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

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.

Tailoring the flap to each patient

• Unlike traditional microkeratomes, the Intralase allows the surgeon to specify the architecture of the flap

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

Complications using Intralase

• Thin flaps• Torn flaps; flaps are incompletely cut by

laser on every case• Decentered flaps• Incomplete flaps• Prolonged vacuum time

Resurface the eye

• Typical limits :– Myopia 10D– Hyperopia 4D– Astigmatism 4D

• Wavefront or no wavefront????

Custom ParametersWaveScan Hyperopia Myopia

Sphere +3.75 -6.50

Cyl +2.75 -3.50

WaveScan SE

+3.75 -6.50

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 

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 

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

 

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

 

Flap Dislocation

Fibers

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 destruction2.      Distortion of vison and loss of BVA3.      Hyperopia shift

• Monitor closely in patients with abrasions, flap trauma 

DLK

Central DLK

Epithelial Ingrowth

Epithelial Ingrowth

Epithelial Ingrowth

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

Custom Enhancements

WaveScan Hyperopia Myopia

Sphere +1.00 +1.00

Cyl -1.00 -1.00

WaveScan SE +1.00 +1.00

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