Refractive Surgery In the Military LTC Jeff Rabin, OD, PhD Center for Refractive Surgery Walter Reed...

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Refractive Surgery In the Military

LTC Jeff Rabin, OD, PhD

Center for Refractive SurgeryWalter Reed Health Care System

Washington, DC

In the past we had…

Radial Keratotomy (RK)

Deep spoke-like incisions

Central cornea flattens

For mild to moderate myopia

Good results Weakens cornea

Now we have…

Laser Procedures

• PRK

• LASIK

Photorefractive Keratectomy (PRK)

Excimer laser reshapes cornea

Very precise For myopia,

hyperopia, astigmatism

Good results & safety

LASIK Microkeratome flap Excimer laser

removes precise amount corneal tissue

For myopia, astigmatism and hyperopia

Rapid popularity worldwide

PRK vs. LASIK

PRK• Day one: “Oowww!”• Less surgical risk• Slower recovery• 80% 20/20• Haze possible• No flap

LASIK• Day one: “Wow!”• Greater surgical risk• Quicker recovery• 80% 20/20• No haze• Flap

Center for Refractive Surgery

Do we need refractive surgery in the military…

OPERATIONAL VISION CORRECTIONOPERATIONAL VISION CORRECTION

Over 1/2 million soldiers, sailors and airmen

40% require optical correction

Annual cost of optical corrective devices…vast

OPERATIONAL VISION OPERATIONAL VISION CORRECTIONCORRECTION

Traditional way to correct all forms of refractive error

Relatively inexpensive Few complications Very precise

GLASSESGLASSES

• Disadvantages:Disadvantages:

GLASSESGLASSES

• Disadvantages:Disadvantages:

GLASSESGLASSES

Disadvantages:Disadvantages: Limit range of vision Fogging, scratched Broken or lost Compatibility problems--

with night vision goggles, protective mask inserts, etc.

GLASSESGLASSES

Advantages:Advantages: Cosmesis Increased FOV Less minification—

better vision in myopia

CONTACT LENSESCONTACT LENSES

Disadvantages:Disadvantages: Difficult to clean in field

environment May lead to infection Problematic in chemical

environments Dislodge with G-forces

CONTACT LENSESCONTACT LENSES

REFRACTIVE SURGERYREFRACTIVE SURGERY All-weather 24/7 correction Compatible with equipment Increased soldier confidence

(no broken or fogged glasses) Increased survivability

(lost glasses = casualty) Improved quality of life---

higher retention

ARMY POLICYARMY POLICY AR 40-501 prohibits entry with history

of refractive surgery, but… Waiver policy (OTSG May 2000)

allows for PRK or LASIK if--- At least 6 months since surgery Meet AR 40-501 vision standards

No visual side effects affecting daily activities

Refractive error stability Post-LASIK: excluded from HALO,

Flight, Diving and SF training Post-PRK: excluded from Aviation

ARMY POLICYARMY POLICY

WRESPWarfighter Refractive Eye Surgery Program

• WRESP -- limited resource available to commanders to enhance mission readiness

• MEDCOM establishing WRESP Laser Eye Centers in MTFs designated by the DCSOPS

• WRESP Centers: Operational -- Ft. Bragg Planned -- Ft Campbell, Ft Hood, Tripler AMC, Landstuhl RMC

• WRESP Centers: Operational -- Ft. Bragg Planned -- Ft Campbell, Ft Hood, Tripler AMC, Landstuhl RMC,

• DHS allocates appointments to supported units

• WRESP Centers: Operational -- Ft. Bragg Planned -- Ft Campbell, Ft Hood, Tripler AMC, Landstuhl RMC,

• DHS allocates appointments to supported units • Unit commands maintain by-name 3-month list

Center for Refractive Surgery WRESP Soldier Selection Criteria

Warfighter Refractive Eye Surgery Program• Assigned to unit with mission at line-of-battle or

behind hostile lines

behind hostile lines• 1st priority -- SOC; Infantry, Armor, Field Artillery

behind hostile lines• 1st priority -- SOC; Infantry, Armor, Field Artillery • 2nd priority-- CSS assigned to Division or Separate

Brigade

Brigade• Other service members -- space available

Brigade• Other service members -- space available• At least 18 mo remaining on AD or with reenlistment

Brigade• Other service members -- space available• At least 18 mo remaining on AD or with reenlistment• At least 12 mo remaining with same/similar unit

Brigade• Other service members -- space available• At least 18 mo remaining on AD or with reenlistment• At least 12 mo remaining with same/similar unit• Must return for follow-up as specified

• AD Army, Navy and Marines at Ft Bragg• To benefit Warfighter

(USASOC, 18th Airborne)

• 1500 pts/year (3000 procedures); 125/month • USASOC—PRK only• All others—LASIK or PRK• LASIK disqualifying for SOC schools

(HALO, scuba, SFQC, SERE)• Aviators—not eligible

Womack Army Medical CenterWarfighter Refractive Eye Surgery Program

NAVY POLICYNAVY POLICY

• Similar to ARMY for PRK• Excludes LASIK unless in

research protocol• WRESP Centers at San Diego,

Portsmouth, Bethesda• Four others planned

AIR FORCE POLICYAIR FORCE POLICY

• Waiver for PRK only• Aviation and special duty• Includes 200 rated aviators and

100 student aviators per year• WRESP Center at Wilford Hall;

planned for AF Academy and Wright-Patterson

•80% -- 20/20 UCVA

•60% -- 20/16 UCVA

•>90% -- 20/20 on re-treatment

•Overall -- safe and effective

Completed Navy ResearchInitial Evaluation of PRK

Bottom line…

• How long before 20/20 uncorrected VA?- 40% at 1 week- 81% at 4 weeks- 81% at 12 weeks

• Prolonged recovery, transient CS loss

• Stable refraction in 6 weeks to 3 months

• Extended recovery period in PRK

Completed Navy ResearchVisual Recovery in PRK

Bottom Line…

• No correlation: pupil size & symptoms

• No correlation: pupil size & pre- / post-op visual performance differences

• Symptoms correlated with degree of myopia

Completed Navy ResearchPupil Size, Glare and Halos In PRK

Bottom line…

• Overall: 92% happy with outcome

• The greater the depression before PRK-- less happy and more regret after PRK

• Older patients: less happy, more regret

Completed Navy ResearchPsychiatric Factors and Patient

Satisfaction After PRKBottom line…

• Slight VA and CS decrease at 2 weeks

• Returned to normal at 4 weeks

• Transient loss of NVG performance

Completed Navy ResearchNVG Performance and PRK

Bottom line…

• RK, PRK, LASIK groups

• All: slight corneal swelling (12-34 microns)

• Hyperopic shift large in RK, slight in PRK/LASIK (0.2 – 0.3 D)

• Slight decrease in uncorrected and best corrected vision

Completed Navy ResearchQuality of Vision & Prolonged Exposure

to AltitudeBottom line…

• Distance for detection of road signs

• Detection distances decreased in symptomatic eyes & those with greater light scatter

• Promising functional approach

Completed Navy ResearchNight Driving Simulation After PRK

Bottom line…

• 20/20 UCVA in 73%

• Slight undercorrection of astigmatism common

• Induced cylinder—rare

Completed Navy ResearchVector Analysis Outcome of Astigmatic PRK

Bottom line…

• 92% -- 20/20 UCVA at 12 months

• 70% -- 20/16 UCVA

• Slight decrease in CS, resolved 3 months

• 1 displaced flap at I day post-op

• Rapid return to duty

Completed Navy ResearchInitial Evaluation of LASIK In Navy

Bottom line…

Center for Refractive SurgeryOngoing/Future Naval Research

• Visual performance after PRK and LASIK

• Initial evaluation of (INTACS)

• Hyperopic PRK

• Normative values for contrast sensitivity

• Wavefront sensing

• Cyclogyl vs tropicamide in refractive surgery

• NEI refractive surgery questionnaire

• PRK to retain ametropic Naval aviators

• 80 non-aviators, 20 controls; 30 months

• Comprehensive ophthalmological baseline

• Unique operational testing

• Contrast sensitivity, color vision, NVGs, glare disability, corneal haze detection

• Subsets: PRK at altitude PRK under high Gz loads PRK and cockpit visual simulation

USAF PRK Study

• Nearly 100 subjects; all myopic

• Safe and effective thus far

• Mean values at 6 months:UCVA 20/16BSCVA 20/14BSC SLCT 1.21

• Loss BSCVA and CS in some

Ongoing Air Force ResearchEvaluation of PRK In Air Force

Bottom line…

• Pre-op BSC vs post-op UC

• Decrease on each chart—high contrast VA – 2 letterslow contrast VA – 5 lettersSLCT – 11 letters

• 24% require Rx for 20/20 in one eye

Ongoing Air Force ResearchHigh & Low Contrast Vision In PRK

Bottom line…

• Post-op decrease for middle/low SFs

• More marked decrease with glare and dilation which persisted up to 1 year

• Likely due to refractive transition zone

Ongoing Air Force ResearchContrast Sensitivity & Glare in PRK

Bottom line…

Refractive Surgery InMilitary Aviation

Washington, DC

• PRK and LASIK authorized without waiver, provided that…

• Post-operative condition has stabilized

• No significant adverse effects or complications

• Pilot meets FAA vision standards(Primary standard—corrected to 20/20 each eye)

FAA Policy onRefractive Surgery

• Ongoing study--PRK in rated aviators with promising results thus far

• Initiating study of pilots trainees at least three months post-op to PRK

Naval Aviation PRK Research

• 80 non-aviators, 20 controls; 30 months• Basic vision and operational testing• Altitude, high Gz loads, cockpit simulation• Promising results thus far

Air Force PRK Research

• Effective 2 Aug 00• Includes Aviation & Special Duty• Strict clinical criteria & follow-up• 200 rated aviators/year; 100 pilot candidates• Must have PRK done at approved DoD site• Myopia only: -1 to –5.5; up to 3D astigmatism

Air Force Waiver for PRK

No Current Navy or Army Aviation Waiver for PRK or LASIK Unless In Research Protocol

• Initiated Feb 01

• Visual & flight performance of flight school applicants who had laser surgery

• Enrollment criteria—3 months post-op, stable refraction, class 1 flight standards

• 100 LASIK, 100 PRK, 100 controls

• Goal—determine if PRK/LASIK waiverable

Refractive Surgery & Army AviationUSAARL Accession Study

• To begin Mar 02

• Prospective study of visual & flight performance of pilot trainees

• Refractive surgery at WRAMC Center • 40 PRK, 40 LASIK—matched for degree of pre-

operative refractive error

• Goals--determine if PRK/LASIK waiverable; expand applicant pool; identify factors to minimize risk and maximize performance

Refractive Surgery & Army AviationWRAMC/USAARL Accession Study

• Study approved Jan 02

• UH-60 Black Hawk rated aviators

• Refractive surgery at WRAMC Center • 40 PRK, 40 LASIK—matched for degree of pre-

operative refractive error

• Comparison between flight performance before surgery (with spectacle Rx) and performance after surgery (without Rx)

• LASIK vs. PRK

Refractive Surgery & Army AviationUSAARL/WRAMC Rated Aviator Study

Current Results

D V N Z RH N F V D

F U P V EP E R Z UF H P V E

Z R F N UP R Z E U

F V P Z DU P N H F

High Contrast Visual Acuity

Night Vision Performance and Visual Acuity After Photorefractive

KeratectomyBarbara O’Kane, PhD, Raymond Stefanik,

James Stevens, Prem Subramanian, MD, PhD,Jeff Rabin, OD, PhD, Robert Bauer, MD, PhD,

and Kraig Bower, MD

Center for Refractive SurgeryWalter Reed Army Medical Center

Washington, DCUS Army CECOM RDEC

Night Vision & Electronic Sensors Directorate Fort Belvoir, VA

•Vision often returns tonormal after refractive surgery(eg, PRK or LASIK).

•Despite reports of decreasednight vision…

•Tests of night vision are lacking.

Introduction

•Military operations--at night

•Evaluation of efficacy & safety of refractive surgery for combat…

•Must include night vision performance testing.

Introduction

Research Purpose

To evaluate visual acuity through

night vision gogglesand

detection of low contrast targets

before and after PRK.

• 19 Special Operations soldiers received PRK.

• All near-sighted before PRK (uncorrected VA: 20/40 to 20/400).

• VA evaluated through NVGs(before & 3 months after PRK).

• Detection of low contrast targets(before & 3 months after PRK).

Summary of Methods

•Before PRK— NVG VA was decreased when tested without glasses.

•After PRK — NVG VA without glasses as good or better than pre-operative VA with glasses.

Results (next slide)

Night sky condition

Fullmoon

1/4moon

Starlight OvercastStarlight

Visual acuity(20/...)

NVG Acuity and PRK

mean + 1SEn = 19

binocular data

Pre-op: no correctionPre-op: with correctionPost-op: no correctionPost-op: with correction

better

Results (next slide)Acuity at Low Contrast

• Decrease in VA with decreasing letter contrast.

• No difference between pre- and post-op VA.

• Relation between VA & contrast remained the same in all conditions.

.1 1 10 100

160RE/Pre-opRE/Post-opLE/Pre-opLE/Post-op

Contrast (%)

Acuity and Contrast In PRK

mean + 1SEn = 19

All valueswith best correction

Visual acuity(20/...)

better

• After PRK, NVG performance(without glasses) as good or betterthan performance before surgery(with glasses).

• May translate to improved performance for soldiers unable to wear glasses in combat.

Conclusions

Visual Performance In Soldiers:One Year After PRKPreliminary Results

•VA tested across range of contrasts (1.25 - 100%)

•Small target CS•Spatial and temporal CS

(sine-wave; 2 alternative forced choice)

•Photopic and mesopic testing

•With/without glare

Methods

D V N Z RH N F V D

F U P V EP E R Z U

F H P V EZ R F N U

P R Z E U

F V P Z DU P N H F

Logarithmic progression in

letter size

D V N Z RH N F V D

F U P V EP E R Z U

F H P V EZ R F N U

P R Z E U

F V P Z DU P N H F

Low Contrast Visual Acuity

Rendition of 10% contrast

D V N Z RH N F V D

F U P V EP E R Z U

F H P V EZ R F N U

P R Z E U

F V P Z DU P N H F

Rendition of 2.5% contrast

D V N Z RH N F V D

F U P V EP E R Z U

F H P V EZ R F N U

P R Z E U

F V P Z DU P N H F

Rendition of 1.25% contrast

Small Letter Contrast Sensitivity1 D R E Z U F V N H P

2 R P F D U N Z E V H

3 H R P E D V Z N F U

4 Z E D H P U V R N F

5 H P F D N V R E U Z

6 R Z F D P N U E V H

7 V D H P E N R H U Z

8 U R N E D Z H F V P

9 N V Z F H E P R D U

10 D V N Z R H F U P E

11 P H V D F U E Z N R

12 R V U N D P H Z E F

13 F R E U P Z H D V R

14 E R P D N Z F U V H

.1 1 10 100

1.2MesopicPhotopicGlare

Visual Acuity and Contrast

Letter contrast (percent)

Visual acuity

(logMAR)

20/200

Photopic(daytime)

Mesopic(nighttime)

better

Spatial Contrast Sensitivity:One Year After PRK

(minimum contrast to detect pattern as a function of pattern fineness)

0.1 1 10 100Spatial frequency (cycles/deg)

Contrast sensitivity

(minimum contrastfor detection)

(coarse ---------- pattern fineness ------------------ fine)

Photopic(daytime)

Mesopic(nighttime)

0.1 1 10 100

Temporal frequency (cycles/sec)

Contrast sensitivity

Temporal Contrast Sensitivity:

Photopic(daytime)

Mesopic(nighttine)

One Year After PRK(minimum contrast to detect flicker as a function of flicker rate)

(minimum contrastfor detection)

(slow ---------- flicker frequency ------------------ fast)

Washington, DC

A New Test for Measuring Glare Disability in Refractive Surgery

•LASIK and PRK-- effective for correction of refractive error

•Despite efficacy of refractive surgery

•Many patients complain of glare…

•Particularly at night

Introduction

•Conventional glare testing--bright glare source under photopic conditions

•Paradoxical improvement in vision

•Due to constriction of the pupil

•Which decreases effects of peripheral aberrations

Introduction

•New approach to quantify glare disability

•Which overcomes problems of conventional tests

•By using contrast-modulated stimulus

•Under reduced luminance to encourage pupil dilation

New Test of Glare Disability

•Small letter contrast test(20/25 letters varied in contrast)

•Viewed at low luminance (3 cd/m2)

•With and without diffuse surrounding glare

•Chart luminance remains constant with/without glare

•Minimal (<1mm) change in pupil size

New Test of Glare Disability

1 D R E Z U F V N H P

Viewed at low luminance

Without glare

Viewed at low luminance

With glare

•Shift from photopic to mesopic...8-line decrease in CS

•Addition of glare...further decrease 3-lines

ResultsGlare Disability & Mesopic CS

1-Year After PRK

Photopic Mesopic Mes+Glare

1.5Glare Disability 1-Year After PRK

Test condition

Log small letter

contrast sensitivity

8 lines

3 lines

mean+2SE, n=18 eyes

• Infrared pupillometry under mesopic conditions...

•Larger pupils--lower CS,both with/without glare

•Suggests adverse effect of peripheral aberrations

ResultsGlare Disability & Mesopic CS

1-Year After PRK

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5-0.2

Mesopic CS, Glare & Pupil Size:1-Year After PRK

Mesopic pupil size (mm)

Log small letter

contrast sensitivity

MesopicMes+Glare

Future Research

Video C am era

F ixation Target(adjustable focus)

W avefront Sensor

Probe Laser

• Performance with night vision devices

Future research will assess the impact of refractive surgery on…

• Performance with night vision devices• Night firing

• Performance with night vision devices• Night firing• Land navigation

• Performance with night vision devices• Night firing• Land navigation• Helmet-mounted displays

• Performance with night vision devices• Night firing• Land navigation• Helmet-mounted displays• Flight training

• Performance with night vision devices• Night firing• Land navigation• Helmet-mounted displays• Flight training• Night flight

• Performance with night vision devices• Night firing• Land navigation• Helmet-mounted displays• Flight training• Night flight• Performance of experienced aviators

Beyond 20/20

In Pursuit ofSuper-Normal Vision

Small Letter Contrast Sensitivity

D V N Z RH N F V D

F U P V EP E R Z UF H P V E

Z R F N UP R Z E U

F V P Z DU P N H F

• In standard eye exam, we test for--near-sightedness, far-sightedness, astigmatism

• Additional optical aberrations(e.g., coma, spherical aberration)

• Also have a significant impact on vision.

Beyond 20/20In Pursuit of Super-Normal Vision

• Objective technique now exists for comprehensive measurement of the optics of the eye…

• Shack-Hartmann wavefront aberrometry

• Based on the shape of the wavefront of light reflected from the eye.

• Beam of light is reflected from the eye

• Through a micro-lens array producing a spot image array of reflected light.

• Computer analysis determines relative displacement of each spot image

• Used to compute local slope & character of the wavefront of light.

• The analyzed wavefront is used to derive a correction profile

• Which can be used to—guide laser eye surgery.

• FDA studies nearly complete verifying the efficacy & safety of this approach.

• Our research & development includes…

• State-of-the-art laser with eye tracking

• Coupled with wavefront technology

• Unique measures of visual performance

• To achieve optimal vision for soldier & civilian alike.

• A correction which minimizes optical aberrations will improve….

• Visual acuity—as much as 2x.

• Small target contrast sensitivity(as much as 7x).

• And performance at night when pupil becomes large.

What will Super-Normal Vision look like??

Before correctionof aberrations

After correctionof aberrations

Refractive Surgery In the Military LTC Jeff Rabin, OD, PhD Center for Refractive Surgery Walter Reed...

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