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Tools to provide the best possible image quality to eyes

with low vision

Jörgen Gustafsson, Professor II, PhDUniversity of Southeast Norway

Product and development manager, Multilens

Jorgen Gustafsson

AcknowledgmentsPeter Unsbo and Linda Lundström at the Royal Institute of Technology, Stockholm, Sweden

Peter Lewis and Kartik Baskaran on Linnaeus University, Sweden

The authors have no commercial interests or financial relationships to disclose.

Jorgen Gustafsson

Central visual Field Loss (CFL)• Common cause: age related macular

degeneration (AMD)• Other hereditary retinal diseases• Symptom: Low visual acuity, absolute CFL,

lower VA than logMAR 1.0 (20/200, 6/60, 0.1)

Jorgen Gustafsson

When macula is not working

• Eccentric Viewing

• Preferred Retinal Location (PRL)

Jorgen Gustafsson

Peripheral vision compared to central vision

• Retina: low resolution capacity– The primary limitation– Help: magnifying devices

• Optics: poor image quality– Important when eccentric aberrations are large– Additional help: eccentric correction

Jorgen Gustafsson

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Measuring the peripheral optics of the eye

AimTo find and correct the aberrations in the preferred retinal location (PRL) of subjects with large central field loss.

Methods• Photorefraction with the PowerRefractor• Peripheral wavefront aberrations with a

Hartmann-Shack (HS) sensor.

Jorgen Gustafsson

Raytracing in eye model

Raytracing eye-model ofLiou & Brennan

Image (spotdiagram) on the retina without and with eccentric correction: sphere and cylinder

PowerRefractor

• Photorefraction and fixation target

• The first results showed that the residual vision could be improved when the oblique astigmatism was corrected

Jorgen Gustafsson

©Certec

PowerRefractor

Jorgen Gustafsson ©CertecJorgen Gustafsson

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Hartmann-Shack sensorHS sensor (lenslet array)

CCD

Relay lenses

Flat wavefront Aberrated wavefront

Jorgen Gustafsson

Hartmann-Shack sensor• Wavefront aberrations• Calculation of refraction

– RMS (root mean square) optimization not useful because of the large aberrations

– Optimization of the point spread function of the eye

Jorgen Gustafsson

COAS with open field

• Open field wavefront sensor

• Complete Ophthalmic Analyzing System –High Definition / Vision Research Tool

• COAS – HD / VR

Jorgen Gustafsson

Case Margareta

• Stargarts Syndrome• Visual impaired

since about 15 years age, now 60 years old.

• Eccentric fixation about 18°off-axis to the right

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Eccentric fixation 18°to the right with O.S.

Central correction Sph. –3.75 D VA: 0,04 LogMar 1.4 20/400

Jorgen Gustafsson

Eccentric fixation 18°to the right with O.S.

Eccentric correction Sph. –2 Cyl. –3 ax 90°VA: 0.063 LogMar 1.2 20/320

Jorgen Gustafsson

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Peripheral Visual Evaluation (PVE)

• Resolution:Lea Numbers

High and low contrast

• Detection:Gratings

High and low contrast

Jorgen Gustafsson

Eccentric refraction – Visual function measurements

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1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8Ecc corrFov corr

DV100% DH100% DV25% DH25% R100% R25%

LogM

AR

Jorgen Gustafsson

Healthy eyes compared with CFL high contrast number resolution

• Comparison of resolution acuity with the eccentric refractive correction and the habitual central refractive correction for seven subjects with central visual field loss (A-G) and the four control subjects (C1 – C4)

Jorgen Gustafsson

Healthy eyes compared with CFL low contrast number resolution

Comparison of resolution acuity with low contrast optotypes

(10% for all subjects except A, D and E where 25% was used)

Jorgen Gustafsson

Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus

• Aim: To examine the effect of off-axis optical error correction on resolution acuity at the PRL of a subject with central visual field loss.

Baskaran, K., Rosén, R., Lewis, P., Unsbo, P., & Gustafsson, J. (2012). Optometry and Vision Science. 89, 1417-1423.

Fundus Image of the subject

Damaged macula

25°

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Methodology• Peripheral optical errors were measured & corrected using

an custom-built adaptive optics system

• Grating resolution acuity HOA

Refractiveerrors

(Sphere+cylinder)100% 25% 10%

Optical correction conditions

Full spectaclecorrection

-2.00 / -3.50 x 90

Full spectacle correction

+ Aberrationcorrection

Also measured with habitual correction (OS: -3.25 / -1.75 x 80)

Visual acuity with different corrections

1. Better acuitywith AO thanspectaclecorrection2. 10% contrastacuity measureablewith AO correction

0.89

1.06

1.30

1.04

1.34

Improving

acuity

1.14

1.51

1.06

1.00

0.92

Results• The most noticeable difference between the

central and the eccentric refraction was an induced astigmatism of about 2 - 4 DC

• For the CFL subjects the resolution thresholds varied between individuals due to different preferred retinal locations and cause of central visual field loss

• The CFL seven subjects showed improvements in resolution acuity with eccentric correction compared to central correction. In the healthy eyes improvements were only found in low contrast

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Clinical implications

• If eccentric viewing is used over or under the CFL → minus cylinder ~ 180º

• If eccentric viewing is used to the right or left of the CFL → minus cylinder ~ 90º

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Conclusions

• These results show that optical eccentric correction for the used PRL can be beneficial for subjects with long standing CFL

• The benefit of correcting higher order (HOA) aberrations in the PRL give better VA

• Practical methods to correct HOA need to be developed

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Publications• Lewis, P., K. Baskaran, R. Rosen, L. Lundstrom, P. Unsbo and J. Gustafsson (2014). Optometry and

Vision Science 91(7): 740-746. Objectively Determined Refraction Improves Peripheral Vision• Baskaran, K., Rosén, R., Lewis, P., Unsbo, P., & Gustafsson, J. (2012). Optometry and Vision

Science. 89, 1417-1423. Benefit of Adaptive Optics Aberration Correction at Preferred Retinal Locus

• Lewis, P., Rosén, R., Unsbo, P., & Gustafsson, J. (2011). Vision Research. 51, 1829-34.• Resolution of static and dynamic stimuli in the peripheral visual field• L. Lundström , J. Gustafsson, and P. Unsbo, (2007) Visual Evaluation of Eccentric Refractive

Correction, Optometry & Vision Science Vol. 84, NO 11 PP, 1046-1052• Linda Lundström, Silvestre Manzanera, Pedro M. Prieto, Diego B. Ayala, Nicolas Gorceix, Jörgen

Gustafsson, Peter Unsbo, and Pablo Artal (2007), Effect of optical correction and remaining aberrations on peripheral resolution acuity in the human eye, Opt. Express, 15(20):12654-12661, 2007.

• Lundstrom, L. Gustafsson, J. Unsbo, P. (2005) Assessment of Objective and Subjective Eccentric Refraction, Optometry & Vision Science 82 (4): 298-306

• Lundstrom, L. Gustafsson, J. Unsbo, P. (2005) Off-axis wavefront measurements for optical correction in eccentric viewing, Journal of Biomedical optics Vol. 10, No. 3

• Gustafsson, J. (2004) Optics for Low Vision Enabling, doctoral thesis, Lund University, ISBN 91-628-6241-3

• Gustafsson, J., Unsbo, P. (2003) Eccentric correction for off-axis vision in central visual field loss, Optometry & Vision Science. Vol. 80, No. 7, pp. 535-541 .

• Gustafsson, J. (2002). The first successful eccentric correction, Visual Impairment Research -2001. Vol.3, No. 3, pp. 147-155.

• Gustafsson, J., Terenius E., Buchheister, J., Unsbo, P. (2001). Peripheral Astigmatism in Emmetropic Eyes, Ophthalm. Physiol. Opt. Vol 21, No. 5, pp 393 – 400

Jorgen Gustafsson

Thank you

Jorgen Gustafsson