Fig. 1 shows the accommodative lag/lead determined by dynamic retinoscopy (Fig 1a—MEM retinoscopy, b—Nott retinoscopy) compared to that measured by autorefraction. The line of unity (indicating perfect agreement) does not fit the data well, particularly for higher accommodative lags as determined by autorefraction, and indicates poor agreement between the two measures.
Fig. 2 shows a Bland-Altman plot14 of the difference in the accommodative lag/lead measured by the autorefractor and the dynamic retinoscopy methods compared to the average amount of accommodative lag/lead between the two methods. Larger differences between autorefraction and dynamic retinoscopy were associated with larger average accommodative lags (p = 0.002 for MEM retinoscopy and p = < 0.001 for Nott retinoscopy).
The autorefractor classified 116 (69%) children as having a lag of accommodation ≥1.00 D, MEM retinoscopy classified 85 (51%) children with a lag ≥1.00 D and Nott retinoscopy classified 45 (27%) children with ≥1.00 D of accommodative lag. Of the 116 children with an accommodative lag ≥1.00 D by the autorefractor, 66 children were classified by MEM retinoscopy and 35 by Nott retinoscopy as having an accommodative lag ≥1.00 D, yielding a sensitivity of 57% (95% CI = 47 to 66%) for MEM retinoscopy and 30% (95% CI = 22 to 39%) for Nott retinoscopy (Table 3). Of the 52 children classified with an accommodative lag <1.00 D by autorefraction, 33 children were classified by MEM retinoscopy and 42 children by Nott retinoscopy as having accommodative lags <1.00 D, yielding a specificity of 63% (95% CI = 49 to 76%) for MEM retinoscopy and 81% (95% CI = 67 to 90%) for Nott retinoscopy.
To determine if altering the cut points used for MEM and Nott retinoscopy methods would improve the ability of these methods to identify individuals with an accommodative lag ≥1.00 D as determined by the autorefractor, ROC curves were generated and are shown in Fig. 3. When the curve rises rapidly and lies close to the true positive values plotted on the ordinate, the area under the curve will be large, indicating the technique is accurate and both the sensitivity and specificity will be high. As seen in Fig. 3, the shape of the ROC curves for MEM and for Nott retinoscopy approaches the 45° diagonal and the area under the ROC curves is 0.59 and 0.60, respectively, demonstrating that neither technique accurately differentiates subjects with accommodative lag ≥1.00 D from those with accommodative lag <1.00 D based on the autorefractor. Changing the cut point for either method does not improve either method’s performance for identifying accommodative lag ≥1.00 D as determined by the autorefractor. For example, lowering the MEM retinoscopy cut point to 0.75 D accommodative lag would yield a sensitivity and specificity of 76 and 27%, respectively; lowering the Nott retinoscopy cut point to 0.75 D accommodative lag would yield a sensitivity and specificity of 58 and 54%, respectively.
Comparison of MEM vs. Nott Retinoscopy
Comparing MEM retinoscopy to Nott retinoscopy, the difference in accommodative lag/lead (MEM retinoscopy minus lag/lead calculated by Nott retinoscopy) ranged from −1.42 to + 1.33 D with a mean difference of +0.12 D, with 121 (72%) of the MEM retinoscopy values falling within 0.50 D of the Nott retinoscopy values. Fig. 4 shows a Bland-Altman plot14 of the difference between the lag/lead determined by MEM and Nott retinoscopy as a function of the average accommodative lag/lead from MEM and Nott retinoscopy. Larger differences between these dynamic retinoscopy methods are associated with larger accommodative lags as determined by the average of the MEM and Nott retinoscopy measurements (p = 0.03). However, larger differences between these two dynamic retinoscopy methods are not associated with larger accommodative lag/lead as determined by autorefraction (p = 0.57).
Agreement between the objective assessment of accommodative lag/lead by open-field autorefraction and either dynamic retinoscopy method was modest to poor. For accommodative lags of 1.00 D or greater as determined by autorefraction, the sensitivity for MEM retinoscopy was 57% and Nott retinoscopy was 30%. Although the specificity was better than sensitivity for each of the retinoscopy procedures, 63% for MEM retinoscopy and 81% for Nott retinoscopy, for most clinical applications the ability to accurately identify a child who does not have a large accommodative lag is often less important than to identify those with higher lags of accommodation. The shape and area of the ROC curves failed to reveal alternate cut points that would improve the combination of sensitivity and specificity for identifying accommodative lag ≥1.00 D as defined by autorefraction.
Comparison of the results of this study to similar studies in the literature is limited by the paucity of previous investigations and the lack of studies with children. McClelland and Saunders15 compared accommodative responses obtained by Nott retinoscopy and the Grand Seiko WV500 autorefractor for a 10.00, 6.00, and 4.00 D accommodative demand in 41 subjects 6 to 43 years of age (mean age: 24.45 years, SD: 9.82 years) while wearing their habitual distance correction for both methods. As stated by the authors, on average, the accommodative response measured with Nott retinoscopy was closer to the 4.00 D target demand (i.e., smaller accommodative lags) than those obtained with autorefraction (consistent with the results reported herein), but the mean difference between the two techniques was small (0.06 D for the 4.00 D stimulus) leading the authors to conclude that Nott retinoscopy “may be confidently used to assess objectively accommodative function ……”15 Rosenfield et al.16 compared a number of measures of accommodative response in 24 adults with a mean age of 25 years (range: 22.5 to 30.1). The comparison relevant to this investigation is between Nott retinoscopy and the Canon R1, an open-field autorefractor. For a 2.50 D demand they report a mean difference of −0.02 D with 95% limits of agreement of ±0.65 D, leading the authors to conclude that Nott retinoscopy was an appropriate method for clinical assessment of accommodative response.16 One explanation for the smaller differences between lag/lead by Nott retinoscopy and autorefraction reported previously15,16 compared to the larger difference reported in the present study is that the range of accommodative lags by autorefraction was much smaller in the previous studies than in the current study. As reported here and shown in Fig. 2, the magnitude of the differences in the amount of accommodative lag/lead measured by autorefraction and dynamic retinoscopy increases as the average of accommodative lag/lead measured by autorefraction and dynamic retinoscopy increases.
Significant procedural differences between each of the retinoscopy techniques and the autorefractor could have contributed to the modest to poor agreement and the higher accommodative lags measured by autorefraction. The current study was designed to compare MEM and Nott retinoscopy as performed routinely in clinical practice to the Grand Seiko autorefractor. MEM and Nott retinoscopy were performed through a trial frame with the most current subjective refraction whereas autorefraction was done through the spherical equivalent of the subjective refraction. Although the entrance criteria restricted astigmatic refractive errors to 1.50 D or less, uncorrected astigmatic errors during autorefraction resulting from the use of the spherical equivalent correction could introduce errors in the measured response if the children biased their accommodation towards one meridian over the other rather than choosing the mid-point where both meridians would be equally blurred. However, previous work by Rosenfield and Ciuffreda17 suggests that when adults are presented with two dioptrically disparate stimuli (separated by 2 or 4 D), the individual’s responses are variable and not predictable. They found that while the majority of subjects’ accommodative responses fell between the two stimulus levels, some accommodated for the proximal and others for the distal target. Therefore it is not possible to predict what effect the difference in refractive correction may have introduced in our study, but it is unlikely to have introduced a systematic error that would account for all the differences reported here.
Another important procedural difference is that both MEM and Nott retinoscopy were done with both eyes open, while autorefraction was performed monocularly, allowing the vergence loop to remain open. Vergence-associated accommodation present during the binocular retinoscopy procedures would be expected to result in smaller lags of accommodation.18 In fact, several authors have reported statistically significant smaller lags of accommodation for targets viewed binocularly compared to monocular viewing conditions. Using the Canon R-1 open-field autorefractor in a group of 14 young adults, Jiang et al.19 found larger accommodative responses (smaller lags of accommodation) for a 2.50 D accommodative stimulus under binocular viewing than found under monocular viewing. Nakatsuka et al.4 also reported smaller lags of accommodation with binocular viewing compared to monocular viewing, using the Grand Seiko open-field autorefractor, the same autorefractor used in the study reported here. For the 3.00 D demand, the accommodative lag for the 28 myopic adults was 0.35 ± 0.35 D (SD) under monocular viewing and 0.16 ± 0.35 D (SD) under binocular viewing. These previous reports of smaller lags of accommodation under binocular viewing conditions than under monocular viewing when tested with the same technique (autorefraction) are consistent with the differences reported in the current study and suggest that differences in viewing conditions between binocular retinoscopy and monocular autorefraction may be contributing to the poor agreement.
Both retinoscopy procedures were performed under moderate room illumination while autorefraction was done with the room lights off. The decreased illumination during autorefraction provides fewer proximal cues that would be consistent with less accurate accommodation or the larger accommodative lags found with autorefraction.20 Although the target size was similar in the present study for both retinoscopy procedures (about 20/80) and autorefraction (20/100), the cognitive demands of the test were greater during retinoscopy. The children were engaged during the retinoscopy procedure by the examiner asking them to read the words or letters aloud, but were only instructed to keep the letters clear during autorefraction. Increased cognitive demand has been associated with greater accommodation21 and therefore smaller lags of accommodation.
Although each dynamic retinoscopy procedure was performed by a different masked examiner, in random-assigned order, it is possible that one type of examiner bias may have contributed to a portion of the differences between the three methods. Although examiners received standardized training on each procedure, examiners may have been biased by the accommodative lag typically found in this age group. The expected accommodative lag for children with normal vision (kindergarten to grade 6) by MEM retinoscopy is 0.33 D,22 much lower than the mean amount of accommodative lag found in our study. When performing MEM or Nott retinoscopy it is difficult to determine how or if this expectation affects the results, but the fact that the lag/lead of accommodation when measured by the two retinoscopy methods was smaller than that obtained by autorefraction is consistent with a bias that could be present based on the expected accommodative lag for this age group. When performing Nott retinoscopy, lags of accommodation are neutralized by increasing the distance between the child and the examiner while the accommodative demand remains stationary at the 33 cm test distance. To measure an accommodative lag of 1.50 D for the 3.00 D demand, the examiner would need to be positioned at 67 cm from the subject, or would move back 33 cm (almost 13 inches) behind the accommodative target. Considering the retinoscope is conjugate with the participant’s point of focus in this technique, it may be difficult for the examiner to accept that the participant would be focused 33 cm behind the plane of the target.
Another factor that might have contributed to the differences between methods is the examiner’s ability to insure that the accommodative response is stable before taking a measurement with MEM or Nott retinoscopy. If the accommodative response is fluctuating, the examiner performing MEM and Nott retinoscopy is able to observe these fluctuations in the retinoscopic reflex and may tend to take the measurement that she/he feels is most representative of the accommodative response, although this could vary greatly across examiners. In contrast, there is no opportunity to directly monitor the accommodative response with autorefraction and take the most stable measurement. A related issue is that if the examiner notes a significant change in the accommodative response during retinoscopy, the examiner can redirect the attention of the child before taking the measurement. This interaction between examiner and subject during retinoscopy would be expected to result in a smaller lag of accommodation compared to the responses measured with the autorefractor, a prediction consistent with the results of this study.
The agreement between MEM and Nott retinoscopy found in this study (72% of values of MEM retinoscopy falling with ±0.50 D of Nott retinoscopy) is similar to that reported previously.16,23,24 The better agreement of MEM and Nott retinoscopy with each other compared with that between either technique and autorefraction suggests that both retinoscopy techniques may be measuring a similar factor, but perhaps not the same measured by the autorefractor.
Strengths of the current study include a large number of children with an extensive range of accommodative lag/leads, improving the generalizability of the results. The two retinoscopy procedures were performed by different examiners, masked to the results of each other. Additionally, all examiners were trained and certified to perform the procedures.
One limitation of the current study is selection bias related to the sample. As this study was conducted as an ancillary study within the screening process for a randomized clinical trial, some sites prescreened potential subjects, recruiting into the present study only those most likely to be eligible for the randomized trial. As a result, the proportion of children with esophoria at near (an inclusion criterion for the randomized trial) is much higher than would be expected in a typical sample of myopic children.8 The average lag of accommodation is also greater than that of typical myopic children in this age range8 measured previously with the Canon R1 open-field autorefractor. Another limitation is the test order effect. Although the order of the two retinoscopy techniques was randomized, the objective measurement of autorefraction was always performed last to maintain masking throughout the retinoscopy procedures. Therefore, the possibility of fatigue or wandering attention during measurements by autorefraction could have led to greater accommodative lag. There is also a trade-off between a larger sample gained by participation from multiple sites and the greater variability that results from the multiple examiners at the different sites.
In summary, MEM and Nott retinoscopy underestimated the lag of accommodation when compared to the objective, open-field autorefractor. The modest sensitivity of MEM and the poor sensitivity of Nott retinoscopy reported here indicate that using these methods according to the protocols employed in this study will not provide a viable alternative to autorefraction for the identification of lags of accommodation of 1.00 D or more in myopic children. A variety of modifiable methodological differences among the techniques may be contributing to the modest to poor agreement. Additional investigations will be required to determine if modification of the dynamic retinoscopy techniques and/or those used for autorefraction would result in better agreement between the different measures of accommodative lag.
No conflicting relationships exist.
The Correction of Myopia Evaluation Trial 2 (COMET2) Study Group
Lead authors: Ruth E. Manny, OD, PhD; Danielle L. Chandler, MSPH; Mitchell M. Scheiman, OD; Jane E. Gwiazda, PhD. Additional writing committee members (alphabetical): Susan A. Cotter, OD, MS; Donald F. Everett, MA; Jonathan M. Holmes, BM, BCh; Leslie G. Hyman, PhD; Marjean T. Kulp, OD, MS; Don W. Lyon, OD; Wendy Marsh-Tootle, OD; Noelle Matta; B. Michele Melia, ScM; Thomas T. Norton, PhD; Michael X. Repka, MD; David I. Silbert, MD; Erik M. Weissberg, OD.
Clinical Sites that Participated in this Protocol
Sites are listed in order by number of patients enrolled into the study. Personnel are indicated as investigator (I), coordinator (C), or tester (T).
Houston, TX—University of Houston College of Optometry (42)
Ruth E. Manny (I), Soyung A. Kim (I), Mamie R. Batres (C), Giselle M. Garza (C), Jennifer A. McLeod (C), Julio C. Quiralte (C), Gabynely G. Solis (C), Heather A. Anderson (T), Karen D. Fern (T)
Indianapolis, IN—Indiana University School of Optometry (33)
Don W. Lyon (I), Donna K. Carter (C), Sara C. Long (C), Stephanie K. Sims (C), Michelle L. Varvel (C), Julia A. Wilhite (C), Scott J. Caughell (T), Kathryn Gray (T), Danielle F. Warren (T)
Fullerton, CA—Southern California College of Optometry (31)
Susan A. Cotter (I), Carmen N. Barnhardt (I), Catherine L. Heyman (I), Kristine Huang (I), Yvonne F. Flores (C), Jamie H. Morris (C), Sue Parker (C), Monique M. Nguyen (T), Michael W. Rouse (T)
Columbus, OH—The Ohio State University (26)
Marjean T. Kulp (I), Jeffrey J. Walline (I), Mark A. Bullimore (I), Maureen E. Biddle (C), Freda D. Dallas (C), Nancy E. Stevens (C), David Berntsen (T), Andrew J. Toole (T)
Birmingham, AL—University of Alabama at Birmingham School of Optometry (22)
Wendy L. Marsh Tootle (I), Marcela Frazier (I), Kristine T. Hopkins (I), Katherine K. Weise (I), Cathy H. Baldwin (C), Terra L. Brackett (C), Michael P. Hill (C), Blake T. Samper (C), Maria S. Voce (C)
Lancaster, PA—Family Eye Group (13)
David I. Silbert (I), Don D. Blackburn (I), Troy J. Hosey (I), Eric L. Singman (I), Noelle S. Matta (C)
Philadelphia, PA—Pennsylvania College of Optometry (2)
Mitchell M. Scheiman (I), Karen E. Pollack (C), Melissa A. Carr (T), Michael F. Gallaway (T), Janet X. Swiatocha (T), Thuy Mong T. Vu (T)
Boston, MA—New England College of Optometry (1)
Erik W. Weissberg (I), Robert E. Owens (C), Elise N. Harb (T)
Correction of Myopia Evaluation Trial 2 (COMET2) Steering Committee:
Jane Gwiazda, Danielle Chandler, Susan Cotter, Donald F. Everett, Jonathan M. Holmes, Leslie Hyman, Marjean Kulp, Don W. Lyon, Ruth E. Manny, Wendy Marsh-Tootle, Noelle Matta, Michele Melia, Thomas Norton, Michael X. Repka, Mitchell Scheiman, David Silbert, Erik Weissberg
PEDIG Coordinating Center:
Roy W. Beck, Gladys N. Bernett, Christina M. Cagnina-Morales, Danielle L. Chandler, Katrina L. Dawson, Quayleen Donahue, Michelle D. Drew, Mitchell Dupre, Raymond T. Kraker, Stephanie V. Lee, Shelly T. Mares, Amanda R. McCarthy, Michele Melia, Pamela S. Moke, Stephanie Morgan-Bagley
National Eye Institute—Bethesda, MD:
Donald F. Everett
PEDIG Executive Committee:
Roy W. Beck, Eileen E. Birch, Stephen P. Christiansen, Susan A. Cotter, Sean P. Donahue, Donald F. Everett, Jonathan M. Holmes, Darren L. Hoover, Pamela A. Huston, Raymond T. Kraker, Michael X. Repka, Nicholas A. Sala, Mitchell M. Scheiman, David K. Wallace.
Ruth E. Manny
University of Houston
College of Optometry
505 J. Davis Armistead Building
Houston, Texas 77204-2020
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Keywords:© 2009 American Academy of Optometry
accommodative lag; dynamic retinoscopy; autorefractor; specificity; sensitivity; myopia; children