comparison of pupillometer with pupillometry function of binocular free-viewing autorefractor

Comparison of Pupillometer With Pupillometry Function of

Binocular Free-Viewing Autorefractor

Charles D Cohn, MD; Jay C Bradley, MD; Peter W Wu, BS; Sandra M. Brown, MD

The authors have no financial interest in the subject matter of this poster

Background• Accurate measurement of the dark-adapted pupil

diameter (DAPD) has become a standard element of the pre-operative assessment for corneal and intraocular refractive surgery

• Most pupillometers in clinical use occlude one eye, which theoretically enlarges pupil size by halving the total retinal light flux

• No independent clinical data have been presented comparing a monocular device to a binocular free-viewing device

Purpose

To assess the performance of a binocular free-viewing autorefractor with pupillometry function against a monocular occlusion pupillometer (Neuroptics Pupillometer or NOP) of known clinical performance.

Note: The NOP has been validated in previous studies to be reliable under our test conditions.1

Devices Used

NeurOptics pupillometer (NOP)WAM-5500 Binocular Accommodation Instrument (FVAR)

Methods• All subjects were volunteers without strabismus, prior

intraocular surgery, or trauma affecting pupillary shape• Device test order and eye test order were randomized• All subjects were dark-adapted prior to testing• 50 patients, divided evenly into groups by age, were

tested under 1 lux and 7 lux ambient illumination with controlled distance fixation at 20 feet

• Testing with the FVAR was done with both eyes open (binocular) and repeated with one eye occluded (monocular)

• Testing with the NOP was repeated until a standard deviation <0.07 mm was obtained

Results

• FVAR had clinically unacceptable outliers of ≥ 0.5 mm in DAPD at both illumination levels tested

• At all age decades, FVAR underestimates DAPD

• Right or left eye testing order and which device was tested first did not affect results

Results

• The FVAR is quite sensitive to small degrees of parallax and decentration and significant effort was required to obtain measurements even in fully cooperative subjects.

• The FVAR takes only one measurement of pupil size instead of averaging several measurements and providing a standard deviation (SD)

• Pupil size is larger when occluding one eye when testing with the FVAR

ResultsMean DAPD (in mm) as a function of age for the NOP & FVAR at 1 & 7 lux

Results

NeurOptics vs Binocular FVAR

-0.4-0.2

00.20.40.60.8

11.21.41.6

0 10 20 30 40 50

Subject Number

NO

P m

inus

FVA

R (m

m)

Right eyeLeft eye

Difference in DAPD (in mm) between NOP & Binocular FVAR

Results

FVAR

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 10 20 30 40 50

Subject Number

Mon

oc m

inus

Bin

oc D

APD

(m

m) 1 lux

7 lux

Difference (in mm) between right eye DAPD with left eye occluded and with both eyes open using FVAR

Conclusions• The WAM 5500 pupillometry function frequently

disagreed with the NOP by ≥ 0.5 mm in DAPD.• Testing the first eye with the NOP does not induce

sustained pupillary constriction that biases the result of the second eye.

• The FVAR is technically more difficult to operate than the NOP

• FVAR accuracy may suffer since the device obtains only a single measurement instead of averaging several

• FVAR measurements suggest pupil size is larger with one eye occluded

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infrared monocular pupillometer for measurement of the dark-adapted pupil diameter. J CataractRefract Surg 2010;36:277-81.

2. Boxer Wachler BS. Effect of pupil size on visual function under monocular and binocularconditions in LASIK and non-LASIK patients. J Cataract Refract Surg 2003;29:275-8.

3. Kurz S, Krummenauer F, Pfeiffer N, Dick HB. Monocular versus binocular pupillometry. JCataract Refract Surg 2004;30:2551-6.

4. Scheffel M, Kuehne C, Kohnen T. Comparison of monocular and binocular infraredpupillometers under mesopic lighting conditions. J Cataract Refract Surg 2010;36:625-30.

5. Brown SM. Monocular versus binocular pupillometry. J Cataract Refract Surg 2006;32:374-5.

6. Ettinger ER, Wyatt HJ, London R. Anisocoria. Variation and clinical observation withdifferent conditions of illumination and accommodation. Invest Ophthalmol Vis Sci 1991;32:501-9.

7. Lam BL, Thompson HS, Corbett JJ. The prevalence of simple anisocoria. Am J Ophthalmol1987;104:69-73.