CORNEAL REFRACTIVE SURGERY BY

FEMTO-SECOND LASER

Presented by:

Ajay Singh

Physics Department Indian Institute of Technology Delhi

Heating

Cooling

Imaging

Communicati

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ANATOMY OF THE EYE

HOW THE EYE WORK

Cornea = Lens Cover

Iris and Pupil = Aperture of

Camera

Lens = Camera’s Lenses

Retina = Camera’s Film

COMMON VISIONS PROBLEMS

Myopia

Nearsightedness

Nearby objects can be seen

perfectly while objects at distance

appear blurry

Light rays occur in front of retina

HYPEROPIA

Opposite of myopia

Farsightedness

Can see distant object more

clearly than nearby objects

Light rays focus behind

retina

ASTIGMATISM

People who suffer myopia

and hyperopia will suffer

astigmastism also

Object both far and near

appear blurry

Light entering the eyeball

focuses on multiple areas

rather than on retina

PRESBYOPIA

Common vision problem for

old age

Dependent with reading

glasses

Human eye loss flexibility of

the lens

Weakening in the muscle

NON-SURGICAL CORRECTION OPTIONS

Glasses

Contact Lenses

Orthokeratology

Refractive Eye Surgery

Refractive eye surgery is eye surgery used to improve the refractive

state of the eye and decrease or eliminate dependency on glasses or

contact lenses. This can include various methods of surgical remodelling

of the cornea or cataract surgery. The most common methods today use

excimer lasers to reshape the curvature of the cornea. Successful

refractive eye surgery can reduce or cure common vision disorders such

as myopia, hyperopia and astigmatism, as well as degenerative

disorders like keratoconus.

In Laser surgery surgery, the curvature of the cornea is altered by

removing a specific amount of corneal tissue with ultraviolet photo-

ablation from the excimer laser.

http://ildenaro.it/blog/2014/02/27/riparazione-della-cornea-al-monaldi-il-laser-supervoloce/

1950’s – Columbian Jose Barraquer developed Microkeratome

& keratomileusis techniques and discovered root causes for eye

trauma

1970’s – Russian Svyatoslav Fyodorov developed Radial

Keratotomy (and posterior chamber implantable contact lenses

in 1980)

1970’s – Development of Excimer Laser (origin of LASEK laser)

1982 – 3 Members of the IBM research team discovered the

laser could be used to remove biological tissue without heat

damage to surrounding tissue

1987 – Dr. Steven Trokel performed the 1st laser surgery on a

patients eye

1996 – Lasik Eye Surgery cecame officially approved by the

U.S. government

BRIEF HISTORY

CLASSIFICATION

REFRACTIVE SURGERIES

CORNEA BASED LENTICULAR BASED COMBINED(BIOPTICS)

-R.K.

-PRK

-LASIK/Intra

LASIK

-EPILASIK

-LASEK

-Conductive

Keratoplasty

-Corneal Inlays

and rings

-Clear Lens

extraction for

myopia

-Phakic IOL

- Prelex Clear

Lens Extraction

with use of

Multifocal IOL’s

Combination

of the two

A) Radial keratotomy (RK)

B) Excimer laser photorefractive keratectomy ( PRK )

C) Laser assisted in situ keratomiliuses (LASIK)

D) Laser assisted subepithelial keratomiliuses ( LASEK )

E) Laser thermokeratoplasty (LTK )

D) Intracorneal ring segments (ICRS)

G) Phakic intraocular lenses (IOLs )

Various types of laser surgery are used to treat refractive error:

LASIK : knife is used to cut a flap in the cornea, and a laser is used

to reshape the layers underneath, to treat refractive error.

IntraLASIK: a variant in which the flap is also cut with a laser

Photorefractive keratectomy (PRK, LASEK), in which the cornea is

reshaped without first cutting a flap

Laser thermal keratoplasty: in which a ring of concentric burns is

made in the cornea, which cause its surface to steepen, allowing

better near vision

Lasers are also used to treat non-refractive conditions, such as:

Phototherapeutic keratectomy (PTK), in which opacities and surface

irregularities are removed from the cornea

Laser coagulation, in which a laser is used to cauterize blood

vessels in the eye, to treat various conditions

Lasers can be used to repair tears in the retina.

Types of lasers used-

Excimer-Excited dimer of two atoms

-An inert gas(Argon)

-Halide(Fluoride)

which releases ultraviolet energy at193nm for corneal ablation

Non-Excimer solid state lasers-

210nm Q switched diode pumped laser

213 nm Q switched diode pumped laser(Pulsar)

Advantage of Non-Excimer solid state lasers-

No toxic excimer gases

Wavelength closer to absorption peak of corneal collagen—less

thermal and collateral damage

Better pulse to pulse stability

Not absorbed by air, water, tear fluid-so less sensitive to humidity or

room temperature

No purging with inert gases required.

PROCEDURE (FEMTOSECOND LASER SURGERY)

Step 1 : Corneal Flap Cutting Procedure

Step 2 : Femtosecond Laser Keratomileusis (FLK)

Step 3:Femtosecond Laser Intrastromal Vision Correction (FLIVC)

Source:www.ele.uri.edu/courses/bme281/F12/ColtonS_2.ppt

INTERACTION OF FEMTOSECOND LASER PULSES WITH CORNEAL TISSUE

Why femtosecond? Bubbles?/

EXAMPLES OF CORRECTION

Source:www.ele.uri.edu/courses/bme281/F12/ColtonS_2.ppt

The surgery is typically done within 30 minutes or less-quick & painless

Most people achieve 20/20 vision (or even better) afterwards (90% reachdesired vision after LASIK)

May still need glasses/contact lenses, but prescription is much lowerthan before

A small percentage of people have an enhancement (minor touch up)surgery later for further improved vision

Requires no bandages or stitches

Research conducted by the Magill Research Center for VisionCorrection, Medical University of South Carolina, showed that the overallpatient satisfaction rate after primary LASIK surgery was 95.4%. Theyfurther differentiated between myopic LASIK (95.3%) and hyperopicLASIK (96.3%). They concluded that the vast majority (95.4%) of patientswere satisfied with their outcome after LASIK surgery.

ADVANTAGES OVER NON-LASER SURGERIES

LASIK LASEK

Name Detail: Laser-Assisted In Situ Keratomileusis Laser Assisted Sub-Epithelial

Keratomileusis

Corrective Uses: Refractive error correction for

nearsightedness, farsightedness,

astigmatism and presbyopia.

Refractive error correction for

nearsightedness,

farsightedness, astigmatism

and presbyopia.

Procedure Length: Outpatient procedure. Laser treatment

requires less than one minute for each

eye; total procedure lasts about 15

minutes per eye.

Outpatient procedure. Laser

treatment requires less than

one minute for each eye; total

procedure lasts about 15

minutes per eye.

Procedural Notes: Uses a microkeratome knife and

excimer laser in procedure. The

epithelium and stroma are cut to a

thickness of 100-180 microns, then an

excimer laser ablates corneal tissue

under the epithelial/corneal tissue flap.

An alcohol solution helps lift the

epithelium.

The epithelium is cut to a

thickness of 50 microns while

the stroma is left uncut. Uses a

trephine, a finer blade than that

used in LASIK. An excimer

laser ablates corneal tissue

under the epithelial flap. An

alcohol solution helps lift the

epithelium.

Main difference Between LASIK and LASEK is thickness of the flap

which includes corneal stroma tissue in LASIK and only epithelial tissue

in LASEK.

Healing &

Recovery:

2 days – 1 week; faster than LASEK. Allowed to drive 1-3

days after surgery.

Flap edges heal within a day. Can drive in about

a week with crisp vision in about 6-8 weeks.

Recovery slightly longer than LASIK - about 4-7

days.

Benefits: Appropriate for people who have more corneal tissue, less

discomfort than LASEK, almost no pain, 20/20 vision or

better is typically achieved, corneal haze very rare,

immediate clear vision, follow-up enhancements are

easier if needed.

Better choice for poor LASIK candidates

including people with less corneal tissue, fewer

haze outcomes than LASIK, preserves more

corneal tissue than LASIK, less risk of dry eye

than LASIK.

Potential

Drawbacks:

Those with thinner corneas may suffer less than ideal

results, flap may dislodge with trauma, increases higher

order aberrations (HOA)**, uneven flap edges may lead to

astigmatism, flap may result in scars, ** Higher order

aberrations (HOA) affect the contrast sensitivity and fine

detail of vision, such as night vision, glare, contrast.

More discomfort than LASIK, takes longer to heal

than LASIK, medications, and conditions are

contraindications, trauma, such as being hit in

the eye may cause flap to dislodge, as a fairly

new technique, long-term outcomes are not well

established, increases HOA, blade can create

uneven flap edges leading to astigmatism.

Indications

for

Procedure:

Required thickness of corneal tissue achieved,

requirement for painless procedure and/or extremely fast

recovery, probably best for correcting over 6.00 diopters of

refractive error.

Corneas too thin or flat for LASIK.

For both of the procedures, extensive screening is required for qualification. Participants must be between

the ages of 18 and 40, vision must be less than -14.00 diopters of nearsightedness, less than +6.00 diopters

of farsigntedness, and less than 6.00 diopters of astigmatism, must not have a history of eye disease or

abnormality.

Contradiction

s to

Procedure:

Thin cornea, not within age limit,uncorrectable range of

vision, unstable prescription, eye disease or abnormality,

diabetic retinopathy, cataracts, glaucoma, ocular

hypertension, autoimmune disorders, contradictory

medication, pregnancy, nursing, large pupils, dry eye, prior

eye surgery, naturally elevated HOA.

Possible inability to maintain thin flap (resulting in

removal of epithelium), not within age limit,

uncorrectable range of vision, unstable

prescription, eye disease or abnormality, diabetic

retinopathy, cataracts, glaucoma, ocular

hypertension, dry eye, prior eye surgery, naturally

elevated HOA.

Acronyms not clarified in the chart include:

– BCV = Best Corrected Vision

– BCVA = Best Corrected Visual Acuity (same as BCV)

– DLK = Diffuse Lamellar Keratitis

– HOA = Higher Order Aberrations

– LOA = Lower Order Aberrations

– ASA =Advanced Surface Ablation (Used in PRK and LASEK)

– ICL = Implantable Contact Len

– IOL = Intra-Ocular Lens.

Per the Council for Refractive Surgery Quality Assurance (CRSQA)

Standards for refractive surgery:

– Minimum of 90% of patients achieve at least 20/40 uncorrected vision.

– Minimum of 50% of patients achieve at least 20/20 uncorrected vision.

– Minimum of 85% of patients achieve within 1± diopter of target.

– Minimum of 50% of patients achieve within 0.5± diopter of target.

– Maximum of 3% of patients experience complications unresolved by 6

months postop.

– Maximum of 0.5% of patients experience serious (vision-threatening)

complications at 6 months post op requiring extensive maintenance or

invasive intervention.

The surgery is typically done within 30 minutes or less-quick & painless

Most people achieve 20/20 vision (or even better) afterwards (90% reachdesired vision after LASIK)

May still need glasses/contact lenses, but prescription is much lowerthan before

A small percentage of people have an enhancement (minor touch up)surgery later for further improved vision

Requires no bandages or stitches

Research conducted by the Magill Research Center for VisionCorrection, Medical University of South Carolina, showed that the overallpatient satisfaction rate after primary LASIK surgery was 95.4%. Theyfurther differentiated between myopic LASIK (95.3%) and hyperopicLASIK (96.3%). They concluded that the vast majority (95.4%) of patientswere satisfied with their outcome after LASIK surgery.

RESULTS

Some patients lose vision.

Some patients develop debilitating visual symptoms.

You may still need eyeglasses after surgery.

Some patients may develop severe dry eye syndrome.

For some farsighted patients, results may diminish with age.

Long-term data is not available.

Potentials Risks

Also The LASER eye surgery is not for you if you are

You required a change in your contact lens or glasses prescription in the

past year. This is called refractive instability.

You have a disease or are on medications that may affect wound healing.

You actively participate in contact sports. You participate in boxing,

wrestling, martial arts or other activities in which blows to the face and

eyes are a normal occurrence.

But Still the success rate > 95%, further

improvements going on

http://en.wikipedia.org/wiki/Refractive_surgery

http://minecrafterfield.deviantart.com/art/Human-Eye-test-sketch-320704758

http://en.wikipedia.org/wiki/Refractive_surgery

http://www.worldoflasers.com/laserapplindustrial.htm

http://en.wikipedia.org/wiki/LASIK

http://en.wikipedia.org/wiki/Laser_surgery#Eye_surgery

http://www.powershow.com

http://www.allaboutvision.com/visionsurgery/lasik.htm

http://www.dlxguard.com/history-laser-eye-surgery

http://www.lasik-eye-surgery.info/history.htm

http://www.medicinenet.com/lasik_eye_surgery/article.htm

http://www.webmd.com/eye-health/lasik-laser-eye-surgery

Reference Links