title: Comparison of visual acuity in macular degeneration patients measured with snellen and early treatment diabetic retinopathy study charts.
abstract: OBJECTIVE
  To compare the measurements of visual acuity (VA) results measured with Snellen and Early Treatment Diabetic Retinopathy Study (ETDRS) charts in eyes with and without age-related macular degeneration (AMD).
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  One hundred four participants (190 eyes) selected from a university retina practice; 80 participants (142 eyes) had some degree of AMD.
  
  
  METHODS
  Visual acuity was measured in each patient using standard procedure with both Snellen and ETDRS charts in random order. Statistical analysis of the results was performed.
  
  
  METHODS
  Difference in VA measured by both charts in logarithm of minimal angle of resolution (logMAR) notations.
  
  
  RESULTS
  Overall, the mean Snellen VA was 0.78 logMAR (= 20/120), and the mean ETDRS VA in the same eye was 0.54 logMAR (= 20/70; P<0.001). In the low vision group (<20/200), represented by patients with AMD, the average difference in number of lines was considerably larger than in the good vision range (>20/30). On average, 20/200 on Snellen was 20/95 on ETDRS (>3 lines difference), and 20/30 on Snellen was 20/25 on ETDRS (<1 line difference).
  
  
  CONCLUSIONS
  Our results show poor agreement between the Snellen and ETDRS charts, and it was more pronounced in the group with poor vision. The ETDRS measurements yielded better VA, particularly in participants with vision <20/200 (representing more advanced AMD patients). We suggest taking these findings into consideration when comparing outcomes in clinical practices (which typically measure VA using standard Snellen charts) with outcomes from clinical trials (which typically measure VA using ETDRS charts).
authors: Joan and Irwin Jacobs Retina Center, Department of Ophthalmology, Shiley Eye Center, University of California, La Jolla, California 92037, USA.
authors: Iryna A
authors: IA
authors: Falkenstein
authors: Denine E
authors: DE
authors: Cochran
authors: Stanley P
authors: SP
authors: Azen
authors: Laurie
authors: L
authors: Dustin
authors: Ajay M
authors: AM
authors: Tammewar
authors: Igor
authors: I
authors: Kozak
authors: William R
authors: WR
authors: Freeman
mesh_terms: D003430:Cross-Sectional Studies; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology*; D015203:Reproducibility of Results; D014787:Vision Tests / Q000295:instrumentation / Q000592:standards*; D014792:Visual Acuity / Q000502:physiology*
references: BMJ. 2000 Oct 21;321(7267):990-2
references: 11039964
references: Invest Ophthalmol Vis Sci. 2006 Mar;47(3):1236-40
references: 16505064
references: Invest Ophthalmol Vis Sci. 2001 May;42(6):1226-31
references: 11328731
references: Am J Ophthalmol. 2003 Feb;135(2):194-205
references: 12566024
references: Ophthalmol Clin North Am. 2003 Jun;16(2):155-70, v
references: 12809155
references: Invest Ophthalmol Vis Sci. 2003 Aug;44(8):3294-300
references: 12882773
references: Br J Ophthalmol. 2003 Oct;87(10):1232-4
references: 14507755
references: Graefes Arch Clin Exp Ophthalmol. 2003 Dec;241(12):968-74
references: 13680248
references: Am J Optom Physiol Opt. 1976 Nov;53(11):740-5
references: 998716
references: Br J Ophthalmol. 1980 Jun;64(6):457-60
references: 7387972
references: Adv Ophthalmol. 1980;41:103-48
references: 7001873
references: Am J Ophthalmol. 1982 Jul;94(1):91-6
references: 7091289
references: J Am Optom Assoc. 1984 May;55(5):359-61
references: 6725833
references: Am J Optom Physiol Opt. 1984 Sep;61(9):595-600
references: 6507580
references: Lancet. 1986 Feb 8;1(8476):307-10
references: 2868172
references: Arch Ophthalmol. 1988 Jan;106(1):55-7
references: 3337707
references: Ophthalmic Physiol Opt. 1988;8(4):363-70
references: 3253626
references: Ophthalmic Physiol Opt. 1988;8(4):397-401
references: 3253632
references: Br J Ophthalmol. 1989 Jun;73(6):457-60
references: 2751979
references: Retina. 1989;9(3):163-9
references: 2480626
references: Ophthalmology. 1992 Jun;99(6):969-75; discussion 975-6
references: 1630786
references: Doc Ophthalmol. 1993;84(2):135-44
references: 8299504
references: BMJ. 1994 Nov 26;309(6966):1408
references: 7755711
references: Optom Vis Sci. 1998 May;75(5):342-8
references: 9624699
references: Am J Ophthalmol. 1959 Dec;48:807-13
references: 13831682
references: Acta Ophthalmol Scand. 2005 Jun;83(3):328-32
references: 15948786
references: Optom Vis Sci. 2005 Nov;82(11):946-54
references: 16317369
references: Clin Experiment Ophthalmol. 2006 Jan-Feb;34(1):6-8
references: 16451251
references: Br J Ophthalmol. 2001 Apr;85(4):432-6
references: 11264133