We thank Dr Arnolds and Ms Matta for their letter regarding our article
Vision screening in children by Plusoptix Vision ScreenerTM compared with
gold standard orthoptic assessment Dahlmann-Noor et al. (19 November
2008). We agree that a child vision screening tool that could be used
effectively with minimal input from healthcare personnel would be
desirable. This, together with the National Screenin...
We thank Dr Arnolds and Ms Matta for their letter regarding our article
Vision screening in children by Plusoptix Vision ScreenerTM compared with
gold standard orthoptic assessment Dahlmann-Noor et al. (19 November
2008). We agree that a child vision screening tool that could be used
effectively with minimal input from healthcare personnel would be
desirable. This, together with the National Screening Committee ( UK)
directive that all children should undergo vision screening between the
age of 4-5 years stimulated our interest in the Plusoptix Vision Screener.
Contrary to their interpretation of Table 3 in our article, the
Plusoptix is not able to detect most refractive errors. This study was a
vision screening investigation, with a study population of mostly
emmetropic children. When the prevalence of refractive errors is low, the
Plusoptix may appear to perform well. However, it fails to identify
children with significant hypermetropia even when it causes a reduction in
visual acuity, probably because of device-induced fixation myopia.
Whilst the present study investigated the performance of the
Plusoptix as a vision screening tool, its refractive performance is
subject of a different study we conducted (Plusoptix Vision ScreenerTM:
The accuracy and repeatability of refractive measurements using a new
autorefractor. Dahlmann-Noor AH, Comyn O, Kostakis V, Misra A, Gupta N,
Heath J, Brown J, Iron A, McGill S, Vrotsou K, Vivian AJ. Br J Ophthalmol.
2008 Nov 10. [Epub ahead of print]). This article is currently available
online and will appear in print soon. In this second study, all subjects
underwent cycloplegic refraction allowing for a meaningful assessment of
the refractive performance of the Plusoptix. Many of Dr Arnold and Ms
Matta’s points occurred to us as well, and are addressed by this second
study. The idea that changing the cut-off criteria could improve
sensitivity is sensible but when we did re-analyse data with different
cutoff values (as explained in the discussion) this resulted in a lowering
of specificity with very modest improvement of sensitivity as would be
expected if the under-estimation of hypermetropia is caused by
accommodation by the child on the machine at 1 metre.
Whereas the prevalence of amblyopia in most populations is between 2-
4%, the combined prevalence of amblyopia. strabismus and significant
refractive errors reducing visual acuity is considerably greater. We
report an orthoptic referral rate of 12.5% in our study with only two
false positives in this group. The limitation of an orthoptist-only
screening program is that refraction is not part of the screening, hence
the desire to find a sensitive and specific refraction tool.
In our view, the Plusopix Vision Screener has many plus points, but
until the problem with fixation-induced myopia is overcome, its lack of
sensitivity limits its use as a stand-alone child vision screening device.
Again, we wish to thank Dr Arnolds and Ms Matta for their interest
and hope that the answers we have provided clarify the concerns they have
raised.
Out of ignorance, I am surprised that the lenses in a stereoscope
should be described as "plus" lenses. They may be so, but I would have
expected the more important property to be prism, to aid superimposition
of the paired images.
We would like to give a response to the letter of Dr. Anshuman
Sinha concerning our article "23 Gauge versus 20 Gauge System for Pars
Plana Vitrectomy: A Prospective Randomized Clinical Trial".
For analysis of postoperative pain we used a simplified verbal
rating scale (ranging from 0, meaning no pain, to 3, meaning severe
pain). The standardized verbal rating scale reaches from 0 (no pain) to...
We would like to give a response to the letter of Dr. Anshuman
Sinha concerning our article "23 Gauge versus 20 Gauge System for Pars
Plana Vitrectomy: A Prospective Randomized Clinical Trial".
For analysis of postoperative pain we used a simplified verbal
rating scale (ranging from 0, meaning no pain, to 3, meaning severe
pain). The standardized verbal rating scale reaches from 0 (no pain) to
10 ("the worst pain possible"), which we think is too extensive for our
patients and purpose.
In literature verbal rating scales are described to be a valid, reliable
and appropriate tool for determination of postoperative pain in clinical
practice [1,2] Furthermore we believe that the assessment of
postoperative pain is not likely to be biased if the assessor is not
masked, because the perception of pain is a completely subjective
parameter.
Regarding the sample size evaluation: The effect size was assumed
to be 75% of the standard deviation and the power to be 80%. These
assumptions were extrapolated from the observations of our previous
study [3]. Unfortunately, this information had been dropped from a
previous version of the manuscript for brevity.
It is well known that studies with single surgeons have better
results than with multiple surgeons. On the other hand, it is
recommended to choose a realistic situation to achieve more realistic
results. Our surgeons were randomized and there was a general surgical
protocol to be followed. This also is the reason why we used two
different vitrectomy machines. Both of them work in a comparable way and
the settings were preset and the same in both machines.
We agree, that the lens status has an influence on the amount of
vitreous removed and that an intraocular tamponade influences
postoperative eye pressure. However, both factors were equally
distributed in both surgical groups and therefore have no influence on
the results.
Concerning the way of suturing the 20 gauge wounds, this was done the
same way in all patients using vicryl 7.0 sutures as described in the
methods section.
A summary of nominal categorical data would have to be done by
contingency tables and neither by mean nor by median and interquartile
range. Since the data mentioned are not of nominal but ordinal nature,
we assume that the author of this letter refers to ordinal data. We have
to note that the summary presented in table 2 was done for the area
under the curve (AUC) for the conjunctival injection and postoperative
pain measured at days 0, 1, 2, 3, one week, one month and three months
after surgery as indicated in figures 1 and 2. Although theses
measurements are, strictly speaking, still of ordinal nature they have a
large range of values (see table 2) and hence can be treated as metric
variables. Moreover, it is common practice to summarize AUCs by mean and
standard deviation. We also note that in a previous version of the paper
we have given in addition to the mean and standard deviation also the
median, first and third quartile. Unfortunately, these numbers as well
as the information in the text that the AUCs are summarized have been
omitted in the edited manuscript.
We furthermore agree that each complication represents a serious
situation. However, from the data of our study we can not conclude that
a clear indication for higher risk is given using 23 gauge vitrectomy.
This question remains open and a larger prospective randomized study is
needed to get a clear result of the safety of 23 gauge surgery. Since
the data do not indicate a difference in the development of serious
complications between the two treatment groups we made the cited careful
assertion "seems to be a safe system".
Regarding the Consolidated Standards for Reporting Trials (CONSORT)
statement [4], we certainly know and appreciate this publication and
followed these recommendations. Moreover, our article represents the
only prospective randomized study concerning this topic.
We do appreciate your considerations, but we strongly believe that we
have performed a well-designed study. Still, there are always things
that can be improved.
References
1.Williamson A, Hoggart B. Pain: a review of three commonly used
pain rating scales. J Clin Nurs. 2005 Aug;14(7):798-804.
2.Randall C. Cork, Ihab Isaac, Ahmad Elsharydah, Sarosh Saleemi,
Frank Zavisca and Lori Alexander: A comparison of the verbal rating
scale and the visual analog scale for pain assessment. The Internet
Journal of Anesthesiology. 2004: Volume 8, Number1.
3.Kellner L, Wimpissinger B, Stolba U, Brannath W, Binder S.
25-gauge vs 20-gauge system for pars plana vitrectomy: a prospective
randomised clinical trial. Br J Ophthalmol. 2007 Jul;91(7):945-8.
4.Moher D, Schulz KF, Altman DG. The CONSORT statement: revised
recommendations for improving the quality of reports of parallel-group
randomised trials. Lancet 2001;357:1191-4.
American pediatricians, armed with a new reimbursement code for
photoscreening young children (99174), are very interested in the validity
of
potential instruments. As such, we were interested in the recent report
that
compared Plusoptix photoscreener to orthoptic exam in early primary school
children, reporting 100% specificity but relatively low sensitivity: “the
sensitivity of the PVS to detect
amblyopia-associated f...
American pediatricians, armed with a new reimbursement code for
photoscreening young children (99174), are very interested in the validity
of
potential instruments. As such, we were interested in the recent report
that
compared Plusoptix photoscreener to orthoptic exam in early primary school
children, reporting 100% specificity but relatively low sensitivity: “the
sensitivity of the PVS to detect
amblyopia-associated factors is 44%, with 95% CI from 28 to 62%. Even a
sensitivity of
62% would be less than desirable for a standalone screening test”[1] We are
concerned the methodology and terminology for “sensitivity” differs from
what many pediatricians might expect.
From Table 3, it appears the PlusOptix was able to detect most refractive
errors but underestimated cycloplegic hyperopia and strabismus. We ask
that
the authors report their results by using pre-defined pediatric
ophthalmology
risk levels (ref 10) and clarify the limited number of their subject who
actually
completed the cycloplegic examination which others consider the gold
standard[2].
Plusoptix allows users to pre-define age-based referral cut offs for
various
amblyopia risk factors. We wonder why the authors chose their PlusOptix
cutoffs that differed from an attempt to calibrate the instrument in
reference
21?[3] Furthermore we wonder if changing the cutoff for hyperopia may
increase the accuracy of the device. It may be worthwhile to re-analyze
this
original cohort to see if the sensitivity would improve. It would also be
worth
noting how the gold standard orthoptic vision screening compares to a
dilated cyclopleged examination by a pediatric ophthalmologist, as
comparing the Plusoptix to a comprehensive ophthalmology examination
may change the reliability. Orthoptists are ideally trained to provide an
accurate pediatric vision screening on children, however in certain
countries,
such as the United States of America, with a population of approximately
305
million people and only approximately 300 orthoptists more efficient
methods of pediatric vision screenings must be discovered and refined.
In recent population studies the prevalence of childhood amblyopia,
primarily
comprised of refractive error and manifest esotropia, is about 2.5%[4]. If
an
acceptable screening technique has false positive rate less than 1/3, then
the
ideal referral rate should be about 4%, much closer to the PlusOptix
compared to 12.5% for orthoptic screening. The author’s “gold standard”
orthoptic screening has merit, but probably has low predictive value for
amblyopia screening.
Robert W. Arnold, MD
Noelle Matta CO, CRC, COT, Orthoptist
Members of the Vision Screening Committee of AAPOS
References
1. Dahlmann-Noor A, Vrotsou K, Kostakis V, et al. Vision
screening in
Children by Plusoptix Vision Screener compared with gold standard
orthoptic
assessment. Br J Ophthalmol 2008;92:e-pub.
2. Donahue S, Arnold R, Ruben JB. Preschool vision screening:
What
should we be detecting and how should we report it? Uniform guidelines
for
reporting results from studies of preschool vision screening. J AAPOS
2003;7:314-6.
3. Clausen MM, Arnold RW. Pediatric Eye/Vision Screening:
Referral
Criteria for the PediaVision PlusOptix S04 Photoscreener Compared to
Visual
Acuity & Digital Photoscreening: “Kindergarten Computer
Photoscreening”.
Binoc Vis and Strabismus Quart 2007;22:83-9.
4. MEPEDS. Prevalence of amblyopia and strabismus in African
American and Hispanic children ages 6 to 72 months the multi-ethnic
pediatric eye disease study. Ophthalmology 2008;115:1229-36 e1.
Dear Editor,
We thank Dr Arnolds and Ms Matta for their letter regarding our article Vision screening in children by Plusoptix Vision ScreenerTM compared with gold standard orthoptic assessment Dahlmann-Noor et al. (19 November 2008). We agree that a child vision screening tool that could be used effectively with minimal input from healthcare personnel would be desirable. This, together with the National Screenin...
Dear Editor
Out of ignorance, I am surprised that the lenses in a stereoscope should be described as "plus" lenses. They may be so, but I would have expected the more important property to be prism, to aid superimposition of the paired images.
Please clarify the optics involved.
BLC
Dear editor,
We would like to give a response to the letter of Dr. Anshuman Sinha concerning our article "23 Gauge versus 20 Gauge System for Pars Plana Vitrectomy: A Prospective Randomized Clinical Trial".
For analysis of postoperative pain we used a simplified verbal rating scale (ranging from 0, meaning no pain, to 3, meaning severe pain). The standardized verbal rating scale reaches from 0 (no pain) to...
American pediatricians, armed with a new reimbursement code for photoscreening young children (99174), are very interested in the validity of potential instruments. As such, we were interested in the recent report that compared Plusoptix photoscreener to orthoptic exam in early primary school children, reporting 100% specificity but relatively low sensitivity: “the sensitivity of the PVS to detect amblyopia-associated f...
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