A clinical investigation into the significance of alignment methods as used with the Dioptron II Automated. Refractor was compared to the subjective refraction. A total of 110 eyes were tested. using two differing alignment modes: 1) instrument alignment target centered with the pupil, i.e. on the pupil axis; 2) instrument alignment target centered on the corneal light reflex, i.e. on the line of sight. Results showed no significant difference between either of the alignment methods when they were compared to the subjective refraction examination results

Courtney, Herb

Goldman, Bruce

Henderson, John

English

CommonKnowledge

Pacific University 
CommonKnowledge 
College of Optometry Theses, Dissertations and Capstone Projects 
3-10-1982 
Clinical evaluation of alignment methods using the Dioptron II 
John Henderson 
Pacific University 
Bruce Goldman 
Pacific University 
Herb Courtney 
Pacific University 
Recommended Citation 
Henderson, John; Goldman, Bruce; and Courtney, Herb, "Clinical evaluation of alignment methods using 
the Dioptron II" (1982). College of Optometry. 588. 
https://commons.pacificu.edu/opt/588 
This Thesis is brought to you for free and open access by the Theses, Dissertations and Capstone Projects at 
CommonKnowledge. It has been accepted for inclusion in College of Optometry by an authorized administrator of 
CommonKnowledge. For more information, please contact CommonKnowledge@pacificu.edu. 
Clinical evaluation of alignment methods using the Dioptron II 
Abstract 
A clinical investigation into the significance of alignment methods as used with the Dioptron II 
Automated. Refractor was compared to the subjective refraction. A total of 110 eyes were tested. using 
two differing alignment modes: 1) instrument alignment target centered with the pupil, i.e. on the pupil 
axis; 2) instrument alignment target centered on the corneal light reflex, i.e. on the line of sight. Results 
showed no significant difference between either of the alignment methods when they were compared to 
the subjective refraction examination results. 
Degree Type 
Thesis 
Degree Name 
Master of Science in Vision Science 
Committee Chair 
Donald Schuman 
Subject Categories 
Optometry 
This thesis is available at CommonKnowledge: https://commons.pacificu.edu/opt/588 
Copyright and terms of use 
If you have downloaded this document directly from the web or from CommonKnowledge, see 
the “Rights” section on the previous page for the terms of use. 
If you have received this document through an interlibrary loan/document delivery service, the 
following terms of use apply: 
Copyright in this work is held by the author(s). You may download or print any portion of this 
document for personal use only, or for any use that is allowed by fair use (Title 17, §107 U.S.C.). 
Except for personal or fair use, you or your borrowing library may not reproduce, remix, 
republish, post, transmit, or distribute this document, or any portion thereof, without the 
permission of the copyright owner. [Note: If this document is licensed under a Creative 
Commons license (see “Rights” on the previous page) which allows broader usage rights, your 
use is governed by the terms of that license.] 
Inquiries regarding further use of these materials should be addressed to: CommonKnowledge 
Rights, Pacific University Library, 2043 College Way, Forest Grove, OR 97116, (503) 352-7209. 
Email inquiries may be directed to:.copyright@pacificu.edu 
CLINICAL EVALUATION OF ALIGNMENT METHODS USING THE DIOPTRON II 
Submitted by 
John }!i~~derson 
Bruce oldman 
Herb Courtney 
In partial fulfillment of the requirement 
for th~ Doctor of Optometry Degree 
Donald Schuman, O.D. 
Pacific University 
Forest Grove, Oregon 
March 10, 1982 
{) 
/ 
ABSTRACT 
A clinical investigation into the significance of alignment 
methods as used with the Dioptron II Automated. Refractor was 
compared to the subjective refraction. A total of 110 eyes 
were tested. using two differing alignment mod.es: 1) instrument 
alignment target centered with the pupil, i.e. on the pupil 
axis; 2) instrument alignment target centered on the corneal 
light reflex, i.e. on the line of sight. Results showed no 
significant d.ifference between either of the alignment methods 
when they were compared to the subjective refraction exam-
ination results. 
page 1 
Introduction 
The age of the automated refractors has come to pass. 
The use of automated refractors in everyday optometric 
practice has become a commonplace occurrence. The ease with 
which 011e can ascertain a quick objective measure of re-
fractive status has made these instruments an invaluable 
aid. in obtaining an initial starting point for the exam-
ination. When considering the use of an automated. refractor 
in actual practice, the question arises as to how one can 
use these instruments most efficiently to arrive at a valid 
measure of the patient's refractive error. Certain variables 
may need to be considered in the actual operation of these 
instruments to obtain the data we can most readily utilize. 
Consideration of these variables with the use of the Dioptron 
II automated refractor will be the purpose of this inves-
tigation. 
The Dioptron II, manufactured by the Coherent Medical 
Division, measures the refractive error of the patient by 
the retinal image formation technique. An invisible, in-
frared bar pattern is projected onto the patient's retina 
while viewing a. visible starburst target within the instrument. 
A focus detector determines the sharpness of the retinal 
image and adjusts the main measuring lens for maximum sharp-
ness. The bars are oriented in various meridians while the 
movable lens is adjusted for the best focus. The relative 
location of the movable lens from its initial starting point 
yields a measure of the patient's refractive error. The back-
page 2 
lighted starburst image which the patient is viewing, projects 
in such a way as ta demonstrate to the operator the corneal 
light reflex reflected from the apex of the cornea. In 
previously reported studies, the location of this corneal 
light reflex determines the patient's own visual axis. 
In placement of the patient in the Dioptron II, prior 
to carrying out the measurements, the operator will often 
note that the patient's corneal light reflex is decentered 
horizontally and/or vertically from the geometric center of 
the pupil. The instrument's manufacturer recommends that the 
operator center the pupil exactly within the target's star-
burst image. The authors have found that when measurements 
are made with the pupil exactly centered, and then placement 
of the pupil image is varied so as to place the corneal light 
reflex at the center of the starburst, different sets of data 
are obtained. 
The literature reveals little information about possible 
variations in the autorefractor results due to varying 
alignment criteria. Most of the studies on the Dioptron 
and other autorefractors deal strictly with the accuracy re-
lative to the subjective exam results. All the studies found 
a very high correlation to the subjective for sphere, r=.978, 
and a fair correlation for cylinder power, r=.766. The 
correlation for cylinder axis was very low for lower cylinder 
powers (less than .50D), and high for cylinders of greater 
power, r=.594 and r=.902, respectively. The Dioptron gave 
page 3 
fairly accurate estimates of the refractive error over a 
wide range of refractive errors, pupil sizes, and subject 
limitations. 
All the studies indicated that the autorefraetor results 
were not reliable or accurate enough to substitute for the 
subjective refraction. The standard technique of retinoscopy 
showed a higher correlation to the subjective than to the 
Dioptron results. In certain people with poor stability of 
fixation (hyperactive children, the mentally retarded, patients 
w·i th nystagmus, uncooperative patients, etc. ) , the instrument 
did not yield reliable or valid results. This leads to the 
possibility that the alignment changes induced by these fix-
ation changes contributed to the erratic results. Since our 
study utilizes two different alignment conditions (pupil 
c.en.tered and corneal light reflex centered), the results 
should indicate if there is a significant change in measure-
ments due to alignment changes. Also, the alignment which 
shows the higher correlation to the subjective exam results 
would obviously be recommended. 
The purpose of this study is to determine if objective 
refraction with the corneal light reflex c.entered within the 
starburst image, provides an objective lens measurement that 
more nearly agrees with the practitioner derived subjective 
refraction to best visual acuity. It is our purpose to test 
this hypothesis in actual practice. This study will hope-
fully help the practitioner to better utilize instruments 
of this design, and at the same time, minimize possible 
page 4 
errors in data collection due to improper initial alignment. 
Methods 
Data was accumulated in a local optometric practice 
where the Dioptron II is incorporated into the initial seg-
ment of the visual examination. Comparison of the Dioptron 
II measurements with the pupil centered, and then with the 
corneal light reflex centered, yielded data that was then com-
pared to the practitioners distance subjective measurement of 
best visual acuity. This study will deal with accuracy of 
the spherical and cylindrical power measurements, as well as 
the accuracy of the location of the cylindrical axis. Re-
fractive data, using the two different modes of alignment, 
was compared to the practitioner-derived subjective to best 
visual acuity. 
Measurements were taken by one of three optometric 
assistants employed in the office. All measurements were 
obtained using the same basic procedures. Initially, the 
patient was com~ortably seated at the instrument and adjust-
ment for height was made. Placement of the chin and forehead 
was such that minimal movement could be achieved. The patient 
was instructed as to what he would be viewing, and the import-
ance of keeping any eye movement to a minimumo Measurements 
were then taken using pupil centration as one criterion 
and centration of the corneal light reflex as the second 
/ 
page .5 
criterion. The distance subjective was determined by one 
of the two optometrists employed by the office. Cycloplegic 
refractions were not included in this study. 
Pearson's coefficients of correlation were used in 
data analysis. A total of 110 eyes were sampled with 
patients ranging in age from 8 years to 82 years. The 
practitioners subjective exam was used as our comparison 
standard. Calculations of coefficients of correlation were 
computed for spherical and cylind.rical power, and cylindrical 
axis. Results of our data analysis follow. 
Results 
The results gathered were statistically analyzed using 
the Pearson Product Moment Correlation Coefficient. The 
data was broken. down to s.eparately analyze sphere power, 
cylinder power and cylinder axis. 
Following are the coefficients of correlation for the 
various comparisons: 
1) The correlation coefficients for the Dioptron II 
sphere pol'rer for 110 eyes as compared. to the subjective re-
fraction sphere findings was r=.987 for pupil alignment and 
r=.989 for corneal reflex centered. 
2) The correlation coefficient for cylinder powers 
of .2.5D or greater were calculated for 64 eyes. Pupil 
alignment vs. subjective refraction revealed a correlation 
page 6 
of r=.748. Corneal alignment vs. subjective refraction 
indicated a correlation of r=.572. 
3) Cylinder axis correlations were obtained from the 
same :s.ample as cylinder powercorrelations. For pupil 
alignment vs. subjective refractive findings, r=.939; for 
corneal reflex centered vs. refractive f.il"ldings, r:::~'76. 
Table of Correlations 
sphere 
sample size = 110 eyes 
cylinder power 
sample size= 64 eyes 
cylinder axis 
sample size= 64 eyes 
pupil centered 
r=.987 
r=.748 
r=.939 
page 7 
corneal reflex centered 
r=.989 
r=.572 
page 8 
Discussion 
This study revealed no significant difference between 
either of the alignment methods tested when they were measured 
against the subjective. The sphere and cylinder axis 
correlations were both very high and almost identical. The 
values obtained were similar to those obtained in past studies. 
The lower correlation for the cylinder power can possibly be 
explained by the fact that the subjective cylinder power is 
often decreased from the amount which actually exists. This 
seems evident in that the average power of cylinder obtained 
by either alignment method was found to be approximately 
0.12D greater than the subjective. 
The results of the study correspond to the manufacturer's 
recommendation that alignment method is not as critical as 
might be expected. The manufacturer states that alignment 
is only crucial in that it allows the maximum amount of in-
frared to reach the instrument having been reflected from the 
retina. 
The use of the Dioptron II gives the clinician a 
reasonably accurate measurement of refractive error regard-
less of the alignment method used. The authors therefore 
recommend that either alignment method can be used dependent 
only on the operator's preference. Either method will result 
in equal levels of success. 
page 9 
References 
1. Sloan PG, Folse KA: Clinical evaluation of a fully auto-
mated optometer. Am J Optom 51:189-197, 1974 
2. Folse KA, Kerr KE: An Automatic Objective Optometer. 
Arch Ophth 93(3):225-231, 1975 
3. Coherent Medical Division: Dioptron II Operating 
Instructions. 1977 
4. Coherent Medical Division: Dioptron II Autorefractor-
Desoription and Clinical Evaluation. 1977 
5. Mailer CM: Automatic Refraction and the Private Ophthal-
mologist: Dioptron II Compared with Subjective Examination. 
Can. J Ophth 13(4): 1978 
6. Drance SM, Mitchell DWA, Schulzen M: Studies of an 
Automatic Refraction Machine. Can J Ophth 10(4):462-468, 
1975 


Clinical evaluation of alignment methods using the Dioptron II

https://commons.pacificu.edu/cgi/viewcontent.cgi?article=2022&amp;context=opt

Clinical evaluation of alignment methods using the Dioptron II

Abstract

Similar works

Full text

Available Versions

CommonKnowledge