ohm effect of low-to-moderate degrees of refractive astigmatism on contrast sensitivity and reading...

OHMEffect of low-to-moderate degrees

of refractive astigmatism onContrast sensitivity and Reading

speed in pseudophakic eyes

Shetal M. Raj, DO, MS, Abhay R. Vasavada, MS, FRCS, Vaishali Vasavada, MS, Viraj A. Vasavada, MS, M.R. Praveen, DO

The authors have received travel expense reimbursement from Alcon Laboratories, USA

Iladevi Cataract and IOL Research Center, Ahmedabad,

India

To evaluate effect of low to moderate degrees of refractive astigmatism (0.5 to 0.75 diopters (D)) on low and high contrast sensitivity and reading speed in pseudophakic eyes.

Purpose

• Prospective, controlled, observational study

Materials and Methods

Study Population

• 40 eyes of 40 pseudophakic patients with single-piece monofocal hydrophobic acrylic IOL

• Monofocal IOL• BCVA of 20/20 • Refractive astigmatism of 0.5 and 0.75D

Inclusion criteria

Study Design-

1. ETDRS acuity using CSV- 3000 chart 100%, 25% , 10% contrast.

2. Contrast sensitivity using the Vector Vision chartsphotopic, mesopic and glare conditions

3. Reading acuity on Radner reading chartsLogRAD scoreMean reading speedMaximum reading speed

Observations

All observations were done monocular with - spherical equivalent (uncorrected cylinder) and - with sphere and cylinder correction (corrected cylinder)

1. Distance contrast acuity

Results

0.5 cyl (n=21) 0.75 cyl (n=19)

S.E. Corr. P value

S.E. Corr. P value

100% -0.14 + 0.1 -0.08 + 0.11 0.0 -0.15 + 0.09 -0.07 + 0.1 0.0

25% -0.06 + 0.13 0.00 + 0.13 0.0 -0.06 + 0.13 0.05 + 0.12 0.0

10% 0.05 + 0.12 0.11 + 0.10 0.1 0.06 + 0.10 0.17+ 0.14 0.0

S.E. = Spherical equivalent (uncorrected cylinder)Corr. = Corrected sphere and cylinder (Corrected cylinder)

P = Paired sample T test

2. Contrast sensitivity: photopic

Results

3 cpd 6 cpd 12cpd 18 cpd

S.E. Corr S.E. Corr. S.E. Corr. S.E. Corr.

0.5 cyl (n=21)

1.54 + 0.14

1.6 + 0.15

1.79 + 0.18

1.91 + 0.16

1.46 + 0.27

1.58 + 0.20

0.96 + 0.22

1.15 + 0.17

P value 0.1 0.01 0.03 0.00.75 cyl (n=19)

1.55 + 0.14

1.62 + 0.12

1.79 + 0.23

1.93 + 0.21

1.31 + 0.3

1.52 + 0.26

0.78 + 0.37

1.02 + 0.32

P value 0.01 0.01 0 0.01

S.E. = Spherical equivalent (uncorrected cylinder)Corr. = Corrected sphere and cylinder (Corrected cylinder)

P = Wilcoxon signed ranks paired test

Contrast sensitivity: mesopic

Results

3 cpd 6 cpd 12cpd 18 cpd

S.E. Corr S.E. Corr S.E. Corr S.E. Corr

0.5 cyl (n=21)

1.39 + 0.17

1.45 + 0.19

1.41 + 0.3

1.55 + 0.27

0.87 + 0.31

1.01 + 0.33

0.45 + 0.29

0.57 + 0.31

P value 0.13 0.0 0.06 0.15

0.75 cyl (n=19)

1.4 + 0.25

1.48 + 0.21

1.41 + 0.23

1.52 + 0.29

0.85 + 0.34

0.84 + 0.31

0.42 + 0.32

0.47 + 0.34

P value 0.05 0.03 0.89 0.29

S.E. = Spherical equivalent (uncorrected cylinder)Corr. = Corrected sphere and cylinder (Corrected cylinder)

P = Wilcoxon signed ranks paired test

Contrast sensitivity: glare conditions

Results

3 cpd 6 cpd 12cpd 18 cpd

S.E. Corr S.E. Corr S.E. Corr S.E. Corr

0.5 cyl (n=21)

1.3 + 0.22

1.45 + 0.19

1.34 + 0.33

1.43 + 0.31

0.88 + 0.24

0.99 + 0.33

0.33 + 0.29

0.40 + 0.27

P value 0.0 0.02 0.17 0.17

0.75 cyl (n=19)

1.31 + 0.2

1.41 + 0.24

1.21 + 0.31

1.4 + 0.32 0.74 + 0.28

0.81 + 0.26

0.22 + 0.14

0.39 + 0.29

P value 0.02 0.01 0.09 0.01

S.E. = Spherical equivalent (uncorrected cylinder)Corr. = Corrected sphere and cylinder (Corrected cylinder)

P = Wilcoxon signed ranks paired test

3. Reading acuity on Radner reading charts

Results

LogRAD Score Mean Reading Speed

Max Reading Speed

S.E. Corr. S.E. Corr. S.E. Corr.

0.5 cyl (n=19)

-0.28 + 0.34

-0.29 + 0.39

117.08 + 29.42

120.42 + 25.53

142.08 + 31.63

155.14 + 34.67

P value 0.33 0.05 0.3

0.75 cyl (n=21)

-0.2 + 0.01 -0.2 + 0.0 115.32 + 25.44

126.32 + 24.53

145.16 + 33.29

161.22 + 35.11

P value 0.33 0.01 0.0

S.E. = Spherical equivalent (uncorrected cylinder)Corr. = Corrected sphere and cylinder (Corrected cylinder)

P = paired sample t test

• The performance of eyes with 0.5 diopter cylindrical error fully corrected resulted in significantly better: – Distance contrast acuity at 100% and 25%– Photopic contrast at 6, 12, 18 cpd– Mesopic contrast at 6 cpd– Glare contrast at 3, 6 cpd– Mean reading speed

Summary

• The performance of eyes with 0.75 diopter cylindrical error fully corrected resulted in significantly better: – Distance contrast acuity at 100% , 25% and 10%– Photopic contrast at 3, 6, 12, 18 cpd– Mesopic contrast at 3, 6 cpd– Glare contrast at 3, 6, 18 cpd– Mean and maximum reading speed

• Correction of astigmatism as low as 0.50 and 0.75 diopters improves the visual performance

• Surgeons must strive to adopt techniques and IOLs that eliminate the pre-existing

astigmatism, such as microincision phacoemulsification approach and using Toric IOLs

Implications

High and Low contrast acuity, contrast sensitivity, Reading acuity was significantly better when correcting 0.5 and 0.75 dioptres of refractive astigmatism as compared to correcting with spherical equivalent and not giving cylindrical correction in the spectacles.

Conclusion