Rawlings.arvo09

Assessment of Age-Related Macular Degeneration With a Radial Deformation Acuity Chart N Rawlings, AF Cruess, PH Artes Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia

Radial deformation acuity (RDA) is a hyperacuity which may be reduced in macular pathologies with distortion of the macular photoreceptor layer. We examined the correlation of RDA with severity of age-related macular degeneration (AMD), the test-retest reliability, and practice effects with a set of 6 handheld RDA charts, in patients with AMD and healthy controls.

Methods

Case Examples

Results There was a strong correlation between log RDA and severity of AMD (AREDS category, Spearman r=0.75, p<0.001), which was similar or higher than that obtained with VA (r=0.62) or CS (r=-0.48) (Figure 2). The widths of the 95% limits of test-retest variability (Bland-Altman analysis) were 0.49 log for RDA, 0.34 logMAR for VA, and 0.51 log for CS (Figure 3). A learning effect was evident with RDA (0.12 log, p<0.001, Wilcoxon) but not with VA (p=0.14) or CS (p=0.54). Fig 2) Correlation with AREDS. RDA Spearman analysis

RDA Bland-Altman Analysis 0.6

Difference log RDA

log RDA

-1.5

-2.0

-2.5

0.4 0.2 0.0

AMD status (AREDS)

-2.0

-1.5

Fig 5: Fundus photograph of right eye reveals numerous drusen and pigmentary changes. This patient had a large deficit in shape discrimination (logRDA, -2.20) with only a minor reduction in VA (logMAR= +0.1). SD-OCT shows foveal drusen and photoreceptor irregularities.

Average log RDA

VA Spearman analysis

VA Bland-Altman Analysis

1.5

0.3

1.0 0.5

5

4

3

2

1

0.0

AMD status (AREDS)

-0.5

0.2 0.1 -0.5

0.5

1.0

1.5

-0.1 -0.2 -0.3

Average logMAR

CS Spearman analysis CS Bland-Altman Analysis

1.8 0.4

Difference log CS

1.6 log CS

1.4 1.2

AMD status (AREDS)

5

4

3

2

1

1.0

0

Fig 1: RDA charts. Stimuli are arranged in groups of 5. Four of the 5 are perfectly circular, while one is distorted sinusoidally. The patientʼs task is to point out the “odd one out” (see FIgs 4-6). There are 6 charts with different combinations to prevent learning.

-2.5

-0.2

5

4

3

2

1

0

-3.0

logMAR

Twenty patients with AMD (mean age 72 yrs, range 47 86 yrs; mean logMAR +0.28, range -0.08 to 1.52) and 5 controls (mean age 71 yrs, mean logMAR +0.12) were examined with visual acuity (VA), contrast sensitivity (CS, Pelli-Robson chart), Fourier domain optical coherence tomography (SD-OCT), and fundus photography. Thirty of 40 eyes (75%) had non-exudative AMD with drusen and abnormalities of the retinal pigment epithelium. Ten eyes (25%) had foveal geographic atrophy (n=7) or exudative AMD (n=3). Shape discrimination was assessed with 6 RDA charts (Figure 1). The psychophysical tests were completed on 2 occasions separated by 2 weeks.

Fig 4: Fundus photograph of right eye displays extensive drusen and pigment abnormalities. Despite nearnormal visual acuity (logMAR= +0.22), this patient had a severe deficit in RDA (logRDA= -2.00, compared to a normal value of approximately -2.80). This correlated with ultrastructural changes seen with SD-OCT.

Fig 3) Retest repeatability

Difference logMAR

Purpose

0.2 0.0

1.2

1.4

1.6

1.8

-0.2 -0.4

Average log CS

Conclusions

Fig 6: Fundus photograph and SD-OCT of healthy control eye. VA (+0.02 logMAR) and RDA (-2.85 log) were within normal limits.

Deficits in Radial Deformation Acuity in AMD patients correlated with the stage of disease (AREDS category). In some eyes, RDA appeared to be reduced out of proportion to VA or CS. This suggests that RDA may be useful for assessing and monitoring AMD.

Dr Rawlings is supported by a Resident Research Grant from the Capital Health Research Fund and an ARVO International Travel Grant.