Non-cycloplegic spherical equivalent refraction in adults:comparison of the double-pass system,retinoscopy,subjective refraction and a table-mounted autorefractor

AIM:To evaluate the accuracy of spherical equivalent(SE) estimates of a double-pass system and to compare it with retinoscopy,subjective refraction and a table mounted autorefractor.METHODS:Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults(age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy,subjective refraction,autorefraction(Auto kerato refractometer TOPCON KR-8100,Japan) and a double pass system(Optical Quality Analysis System,OQAS,Visiometrics S.L.,Spain).Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability.To evaluate the trueness of the OQAS instrument,the SE laboratory bias between the double pass system and the other techniques was calculated.RESULTS:The SE mean coefficient of repeatability obtained was 0.22D.Significant correlations could be established between the OQAS and the SE obtained with retinoscopy(r=0.956,P【0.001),subjective refraction(r=0.955,P【0.001) and autorefraction(r=0.957,P【0.001).The differences in SE between the double-pass system and the other techniques were significant(P【0.001),but lacked clinical relevance except for retinoscopy;Retinoscopy gave more hyperopic values than the double-pass system-0.51±0.50D as well as the subjective refraction-0.23±0.50D;More myopic values were achieved by means of autorefraction 0.24±0.49D. CONCLUSION:The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies.This technique can determine the correct focus position to assess the ocular optical quality.However,it has a relatively small measuring range in comparison with autorefractors(-8.00 to +5.00D),and requires prior information on the refractive state of the patient.

Subjective refractions determined by Dyop® and LogMAR chart as fixation targets

Background:Dyop®is a dynamic optotype with a rotating and segmented visual stimulus.It can be used for visual acuity and refractive error measurement.The objective of the study was to compare refractive error measurement using the Dyop®acuity and LogMAR E charts.Methods:Fifty subjects aged 18 or above with aided visual acuity better than 6/12 were recruited.Refractive error was measured by subjective refraction methods using the Dyop®acuity chart and LogMAR E charts and the duration of measurement compared.Thibo’s notation was used to represent the refractive error obtained for analysis.Results:There was no significant difference in terms of spherical equivalent(M)(P=0.96)or J0(P=0.78)and J45(P=0.51)components measured using the Dyop®acuity and LogMAR E charts.However,subjective refraction measurement was significantly faster using the Dyop®acuity chart(t=4.46,P<0.05),with an average measurement time of 419.90±91.17 versus 452.04±74.71 seconds using the LogMAR E chart.Conclusions:Accuracy of refractive error measurement using a Dyop®chart was comparable with use of a LogMAR E chart.The dynamic optotype Dyop®could be considered as an alternative fixation target to be used in subjective refraction.

Evaluation of patient visual comfort and repeatability of refractive values in non-presbyopic healthy eyes

AIMTo evaluate the intra-operator repeatability in healthy subjects using the WAM-5500 auto-kerato/refractometer and the iTrace aberrometer, to compare the refractive values and the subjective refraction obtained with both devices and to determine which of these three spherocylindrical corrections allows the subject to achieve the best visual comfort.METHODSForty-two non-presbyopic healthy eyes of 42 subjects were enrolled in this prospective study. Refractive values were compared, evaluating the repeatability, the relationship between the methods and the best visual comfort obtained.RESULTSSphere, cylinder and axis results showed good intraclass correlation coefficients (ICC); the highest ICC was obtained using the spherical refraction with the autorefractometer and the aberrometer, achieving levels of 0.999 and 0.998, respectively. The power vector (PV) was calculated for each refraction method, and the results indicated that there were no statistically significant differences between them (P&#x0003e;0.05). Direct comparison of PV measurements using the three methods showed that aberrometer refraction gave the highest values, followed by the subjective values; the autorefractometer gave the lowest values. The subjective method correction was most frequently chosen as the first selection. Equal values were found for the autorefractometer and the aberrometer as the second selection.CONCLUSIONThe iTrace aberrometer and the WAM-5500 auto-kerato/refractometer showed high levels of repeatability in healthy eyes. Refractive corrections with the aberrometer, the autorefractometer and subjective methods presented similar results, but spherocylindrical subjective correction was the most frequently selected option. These technologies can be used as complements in refractive evaluation, but they should not replace subjective refraction.