Content uploaded by Evangelos S Pateras
Author content
All content in this area was uploaded by Evangelos S Pateras on Mar 09, 2020
Content may be subject to copyright.
e -Journal of Science & Technology (e-JST)
e-
http://e-jst.teiath.gr 9
Measurement of the eye accommodation range in young people with different
daily habits
Dr. Ε. Πατέρας
Mphl, PhD Aston University, Καθηγητής Εφαρμογών, Τ.Ε.Ι. Αθήνας
Τμήμα Οπτικής & Οπτομετρίας, e-mail: pateras@teiath.gr, Tel: 210-5385723
Abstract
Objective: To evaluate and measure the dioptric eye accommodation range in young
people with different daily habits and especially into two groups, those who use
computers for about 8 hours per day and those who do not use computers at all or use
them for less than 2 hours per day. The purpose of this study was to see if there is a
difference in eye accommodation range between these two populations.
Method and materials: The eye accommodation range was measured in the right eye of
200 young people whose ages were from 20 to 23 years. The average age of individuals
was 21.5 years. Basic requirement was that the first 100 were daily users of computers
(students from the Department of Informatics, T.E.I. of Athens with at least 8 hours
daily use of computers) while the remaining 100 have little or no use of computers
(students from Department of Optics & Optometry, T.E.I. of Athens).
The two clinical techniques used for measuring subjectively eye accommodation range
were a) The push-up method b) the minus lenses method.
Results: The data showed, that the differences in eye accommodation range between the
two populations, was around 0,25 Ds approximately maximum 0,33 Ds corresponding to
2-4% of the total eye accommodation range which is probably within the limits of
statistical error. What should also be noted is that in both group populations there was a
reduction in the range of eye accommodation about 2.00 Ds from the Donder’s results
that may be due to the subjective type of measurements used or other environmental
factors.
Key words: eye accommodation, push-up method, minus lenses method.
Introduction
Accommodation1,2,10,12 , as we all know is the ability of the eye to change its power by
changing the shape of the crystalline lens6,8,9,10,14,15 (changing the curvature of the
lens), and allow objects to be seen clearly at varying distances from it.
The crystalline lens of the eye is held in place by Zinn ligaments (Zinn’s membrane, the
ciliary zonule), a ring of fibrous strands connecting the ciliary body with the crystalline
lens of the eye and attached in the region of the equator of the lens. The ciliary body is
the circumferential tissue inside the eye composed of the ciliary muscle and the ciliary
processes. The ciliary body receives parasympathetic innervations from the oculomotor
nerve.
The parasympathetic system increases the curvature of the lens and facilitate
accommodation in order that nearby objects to be focused. The sympathetic
system reduces the curvature of the lens, facilitating the vision of distance vision objects
distant. Contraction of the ciliary muscle causes relaxation of the Zinn ligaments3,4,5,7
and reduction of tension that they carry in the lens periphery. Under the
influence of elastic forces13 of the lens capsule, the lens takes a more spherical shape and
e- &
e-Journal of Science & Technology (e-JST)
(2), 7, 2012 10
increases its refractive power. By this mechanism the eye can focus and display clearly
on the retina not only distant objects but also nearby.
The unit used to measure eye accommodation is the dioptre (D). The accommodation of
one dioptre is the amount of accommodation needed for an emmetropic person to
see a clear and sharp object away from its eyes at 1m distance.
The following Table 1. is given by Donders11,12. The first column shows the age
and the second the near point for an emmetropic eye in millimetres, the third
the diopters of adaptive (accommodative) power.
Table 1. Correspondence of dioptres, age and the near point in the normal eye
Age
Near vision point in mm
Corresponding Diopters
10
7
14
20
9
11
30
12
8
40
22
4,5
45
28
3,5
50
40
2,5
55
55
1,75
60
100
1
65
133
0,75
70
400
0,25
75
infinity
0
Method and materials
The amplitude of accommodation of the right eye was recorded. Ametropic cases were
given full correction before recording the near point of accommodation. In this study the
known clinical techniques for measuring subjectively eye accommodation range16 were
adopted and below analyzed:
The PUSH-UP Method11,12
For a young healthy person, a card (Snellen’s optotype for near) appears at 40
cm distance with 40 W lighting and the patient is instructed to find the smallest letter in
the card that can be seen clearly, usually 10/10 newsletter. As the card approaches the
patient, the examiner asks the patient when these letters start to blur. This test can be
conducted either binocular or by one eye at a time. The point where these letters start to
blur is measured in centimetres and record for example 10 cm. The dioptre of eye
accommodation is that number divided by 100 cm (e.g.100/10 = 10.0 dioptres).
The MINUS LENS TEST Method17
The method is using negative lenses of increasing power in front of the examined eyes
and is still a subjective measure technique for the range of eye accommodation. Under
specified conditions the test is performed monocularly, while the testing card
(Snellen’s optotype for near) is held at 33 cm in front of the tested eye. Then negative
lenses of increasing power are added in 0.25 dioptre increments. The purpose is to add
negative lenses up until the subject examined starts to defocus the letters of the
Snellen’s optotype. The sum of the negative lenses added in front of the eye is the
e -Journal of Science & Technology (e-JST)
e-
http://e-jst.teiath.gr 11
measured eye accommodation. While the push-up method may overestimate the final
eye accommodation due to the relative magnification of the target letters, the method of
the negative lenses may underestimate the eye accommodation because of
the reduced relative magnification produced by the negative lenses. In an effort to
address this problem, a proposal was made to place the test within 33cm instead of the
40 cm distance used by the push-up method. An expected difference between the
two tests of about >2.0 diopters is reported in other research projects. In our study the
difference between the two techniques was 3.07 Ds.
Clinical techniques
The survey was carried out using these two techniques for measuring subjectively eye
accommodation range in two populations with different daily behavior. The reference
was in working hours of computer use. The eye accommodation range was measured in
the right eye of 200 young people whose ages were from 20 to 23 year. The average age
of individuals was 21.5 years. Basic requirement was that the first 100 were daily users
of computers (students from the Department of Informatics, T.E.I. of Athens with at
least 8 hours daily use of computers) while the remaining 100 have little or no use of
computers (students from Department of Optics & Optometry, T.E.I. of Athens). The
purpose of this study was to determine whether the use of computers for about 8 hours
per day affects the eye accommodation range and thus to differentiate the results
between these two groups of people, those who use computers for more than 8 hours
daily and those who use them less than 2 hours.
Results
Comparison of the two groups
Statistical study of results
Table 2.
Group 1 (Non users of computers
< 2 hours per day)
Group 2 (Users of computers
> 8 hours per day)
Method : PUSH - UP
Method : PUSH - UP
Sample
100
Sample
100
Arithmetic mean of eye accommodation
9,0000
Arithmetic mean of eye accommodation
8,8850
95% CI for the mean
8,7541 έως 9,2459
95% CI for the mean
8,6453 έως 9,1247
Standard deviation
1,2391
Standard deviation
1,2078
Paired samples t-test
Mean difference
-0,1150
Standard deviation
1,6664
95% CI
0,4457 έως 0,2157
BLAND AND ALTMAN PLOT
Lower limit = -3,1512
95% CI = -3,7182 έως -2,5843
Upper limit = 3,3812
95% CI = 2,8143 έως 3,9482
e- &
e-Journal of Science & Technology (e-JST)
(2), 7, 2012 12
Figure 1. Bland & Altman plot, showing the average difference between these two
groups, Group1 & 2 in dioptres for eye accommodation range, measured with the
PUSH-UP method. The average difference between these two populations in eye
accommodation range corresponds to 0.11 Ds
Group 1 (Non users of computers
< 2 hours per day)
Group 2 (Users of computers
> 8 hours per day)
Method : MINUS LENS TEST
Method : MINUS LENS TEST
Sample
100
Sample
100
Arithmetic mean of eye accommodation
6.0400
Arithmetic mean of eye accommodation
5.7100
95% CI for the mean
5.8883 έως 6.1917
95% CI for the mean
5.5293 έως 5.8907
Standard deviation
0.7644
Standard deviation
0.9106
Paired samples t-test
Mean difference
0.33000
Standard deviation
1,2252
95% CI
0,0869 έως 0,5731
BLAND AND ALTMAN PLOT
Lower limit = -2,0714
95% CI = -2,4882 έως -1,6545
Upper limit = 2,7314
95% CI = 2,3145 έως 3,1482
e -Journal of Science & Technology (e-JST)
e-
http://e-jst.teiath.gr 13
Figure 1. Bland & Altman plot, showing the average difference between these two
groups, Group1 & 2 in dioptres for eye accommodation range, measured with the
MINUS LENS TEST method. The average difference between these two populations in
eye accommodation range corresponds to 0.33 Ds
Conclusions
As it is evident from the results of the clinical research for at least the age group between
20 to 23 years the population who does close reading work and especially usage of
computers for > 8 hours daily does not seem to be affect in their eye accommodation
range compared with those who do close work less than 2 hours per day. The differences
in eye accommodation range between the two populations was around 0,25 Ds
approximately (maximum 0,33 Ds – minimum 0.11 Ds) corresponding to 2-4% of the
total eye accommodation range, which is probably within the limits statistical error.
What should also be noted is that for both groups populations there was a reduction in
the eye accommodation range of about 2.00 Ds from Donder’s results, which might be
due to measurement procedure errors or other environmental factors. It should be
therefore a necessity to re-evaluate earlier studies for the measurement of eye
accommodation in all age groups by using both subjective and objective techniques,
cross-checked.
References
1. Fincham EF: The mechanism of accommodation. Br J Ophthalmol 1937, 21:
2. WeaIe RA: Presbyopia. Br J Ophthalmol 1962, 46: 660–8.
3. Fisher RF: The force of contraction of the human ciliary muscle during
accommodation. J Physiol 1977, 270: 51–74.
4. Coleman DJ: Unified model for accommodative mechanism. Am J
Ophthalmol1970, 69: 1063–79.
5. Coleman DJ: On the hydraulic suspension theory of accommodation. Trans Am
Ophthalmol Soc 1986, 84: 846–8.
e- &
e-Journal of Science & Technology (e-JST)
(2), 7, 2012 14
6. Fisher RF: The significance of the shape of the lens and energy changes in
accommodation. J Physiol 1969, 201: 21–47.
7. Fisher RF: The ciliary body in accommodation. Trans Ophthalmol Soc UK
1986, 105: 208–17.
8. Brown N: The changes in shape and internal form of the lens of the eye on
accommodation. Exp Eye Res 1973, 15: 441–59.
9. Fisher RF: The elastic constants of the human lens. J Physiol 1971, 212: 147–80.
10. Fisher RF: Presbyopia and the changes with age in the human crystalline lens. J
Physiol 1973, 228: 765–79.
11. Donders FC: On the anomalies of accommodation and refraction of the eye.
London: New Sydenham Soc (1864).
12. Duane A. Normal values of the accommodation at all ages JAMA. 1912;
59(2):1010–1013.
13. Schachar RA. The mechanism of accommodation and presbyopia. International
Ophthalmology Clinics. 46(3): 39-61, 2006
14. Schachar RA, Abolmaali A, Le T. Insights into the etiology of the age related
decline in the amplitude of accommodation using a nonlinear finite element model
of the accommodating human lens. British Journal of Ophthalmology. 90: 1304-
1309, 2006.
15. Schachar RA. The mechanism of accommodation and presbyopia. International
Ophthalmology Clinics. 46(3): 39-61, 2006.
16. Chattopadhyay DN, Seal GN. Amplitude of accommodation in different age groups
and age of on set of presbyopia in Bengalee population. Indian J Ophthalmol 32:85-
7, 1984
17. Heather A. Anderson, Gloria Hentz, Adrian Glasser, Karla K. Stuebing, and Ruth E.
Manny “Minus-Lens–Stimulated Accommodative Amplitude Decreases
Sigmoidally with Age: A Study of Objectively Measured Accommodative
Amplitudes from Age 3” Invest Ophthalmol Vis Sci. 2008 July; 49(7): 2919–2926.
