Assessment of Stereopsis in Myopic and Hyperopic
Anisometropia
Shakila Abbas, Aima Khalid, Qurat-ul-Ain,
Zarish Riaz, Rai Farwa Nawaz
The University of Faisalabad 38000, Pakistan
|
METADATA Paper history Received: 20
March 2023 Revised: 10 April
2023 Accepted: 20 April
2023 Published online:
10 May 2023 Corresponding
author
Email: shakilaabbas.OPT@tuf.edu.pk (Shakila Abbas) Keywords Myopia Stereopsis Anisometropia Hyperopia Citation
Abbas S, Khalid
A, Qurat-ul-Ain, Riaz Z, Nawaz RF (2023) Assessment of stereopsis in myopic and hyperopic
anisometropia. Innovations in
STEAM: Research & Education 1: 23010101. https://doi.org/10.63793/ISRE/0001 |
ABSTRACT Background: Anisometropia, a condition
where each eye has a different refractive power, can significantly affect
binocular vision and depth perception. Myopic and hyperopic anisometropia may
lead to disrupted stereopsis, impacting visual performance and quality of
life. Objective: The purpose of the study was
to assess and compare the impact of myopic and hypermetropic anisometropia on
stereopsis. Methodology: This cross-sectional study was
conducted from August 2021 to December 2021 at Madina Teaching Hospital,
Faisalabad. About 30 individuals of both sexes were included, aged from 12 to
25 years. A non-probability convenient sampling technique was employed to
access the data. Patients having refractive anisometropia were included, and
those with any type of ocular pathology, infections, strabismus, and
amblyopia were excluded. Stereopsis was assessed binocularly with best
refractive correction by the TNO chart (a clinical test for evaluating
stereopsis). An independent sample t-test was used with the help of
IBM SPSS-20 to get a statistical result. Results: The results of the study showed that the mean value of
120 ± 69.282 seconds of arc scoa red by myopic anisometropic and 276 ± 150.20
second of arc by hyperopic anisometropic. Although the normal values for
stereopsis for an emmetropic person should score 60 seconds of arc, which
means that minimum value for stereopsis reveal good and increased levels for
stereopsis. As the mean values for stereopsis in both myopic and hyperopic
anisometropia are greater than the normal value of stereopsis, this shows
that both the myopic and hyperopic anisometropic persons have decreased
levels of stereopsis. Conclusion: The results of the study
concluded that anisometropia reduces stereopsis; however, these reductions
are more significant in hyperopic anisometropia as compared to the myopic
anisometropia. Study recommends making stereopsis assessment and management
as an integral part of routine examination to improve the qualities of life
who are suffering. |
INTRODUCTION
The
term ametropia (refractive error) depicts any condition where light is
inadequately focused on the retina of the eye, bringing about obscured vision.
This is a typical eye issue and incorporates conditions, for example, myopia
(near-sightedness), hypermetropia (far-sightedness), astigmatism, and
presbyopia is an age-related decrease of vision. (Agarwal et al. 2002).
Anisometropia is a condition in which both eyes of an individual have different
refractive power (Khurana et al. 2014). In myopic anisometropia, the
sharpness of distance vision in each eye is lower than normal, the more
nearsighted eye having less clearance of vision. In any case, when the measure
of nearsightedness in the less nearsighted eye is small (minus 0.25 or 0.50 D),
the visual sharpness in that eye is adequately great with the goal that the
patient may not know about the issue, regardless of whether the visual keenness
in the more nearsighted eye is very poor.
In hypermetric anisometropia, the visual
sharpness of the two eyes is moderately good as long as the patient has
adequate accommodation (Khurana and Khurana 2015). Stereopsis is specifically
referring to perception of depth in relation to binocular single vision (Fig. 1),
which makes basics for seeing three dimensional images (Howard and Rogers 1995).
Fig. 1: Stereopsis view
Fig. 2: TNO test for stereopsis
Stereo acuity development in
children with normal binocular single vision. The lower limits of stereo acuity
compatible with normal binocular single vision were 3 1/2 years, 3,000 seconds;
5 years, 140 seconds: 5 1/2 years, 100 seconds; 6 years, 80 seconds; 7 years,
60 seconds; and 9 years, 40 seconds (Shah et al. 2009).
MATERIALS AND METHODS
A cross-sectional study was conducted from August 2021 to December 2021
in the Department of Ophthalmology, Madina Teaching hospital Faisalabad,
Pakistan. All patients included in the study were selected through
non-probability convenient sampling technique. Total number of patients
included in the study was 30. Both genders were included, age ranged from 12 to
25 years. 15 patients with refractive hyperopic anisometropia (spherical) and
15 patients with refractive myopic anisometropia (spherical) were included. All
the patients have anisometropia of greater than 1D without any ocular
pathology. All cases with strabismus, media opacity, patients with history of
any ocular surgery, ocular trauma, cataract, pseudophakia, aphakia, amblyopia,
keratoconus, and ocular pathologies were excluded. After taking both verbal and
written consent detailed history was taken.
Subjective plus objective refraction was done to confirm
myopic and hyperopic anisometropia. Stereopsis was tested in both myopic and
hyperopic anisometropia. TNO chart was used to measure the stereopsis with best
corrected visual acuity of the anisometropic patient. After the collection of
data, independent sample t-test was used with the help of IBM SPSS-20 to
get statistical results.
RESULTS
To check the normality of data Shapiro-wilk test was
applied. After analysis, it showed, that non-significant (p>0.05), so
parametric test was used. The study included 30 anisometropic patients with age
ranging from 12–25 years. Out of them 15 had myopic anisometropia and 15 had
hyperopic anisometropia. The study showed that 12(40%) were male and 18(60 %)
were female with mean age 16.93.
For
qualitative assessment of stereopsis, among the myopic anisometropic group,
gross stereopsis was present in 13(86.6%) and remaining 2(13.3%) showed absence
of gross stereopsis. Results obtained from the hyperopic anisometropic group
showed that gross stereopsis was present 11(73.3%) and the remaining 4(26.6%)
did not had gross stereopsis and showed absence of stereopsis. More subjects
from myopic anisometropic group showed presence of stereopsis as compared to
the hyperopic anisometropic group By analyzing both of the results, presence of
gross stereopsis in myopic anisometropic was more significant than that of
hyperopic anisometropic.
Quantitative
assessment of stereopsis for myopic and hyperopic anisometropia was done which
resulted means value of 120 ± 69.282 sec of arc scored by myopic anisometropic
and 276 ± 150.20 sec of arc by hyperopic anisometropic subjects included in
this study. Although the normal values for stereopsis for an emmetropic person
should score 60 sec of arc which means that minimum value for stereopsis reveals good and increased levels
for stereopsis. As the mean values for stereopsis in both myopic and hyperopic
anisometropia are greater than the normal value of stereopsis, shows that both
the myopic and Table
1: Comparison
of stereopsis of myopic anisometropia and hyperopic anisometropia t-test for equality of means Parameters F test Significance t test df Significance (2-tailed) Mean difference Standard error difference 95% confidence interval of
difference Lower Upper Equal variance assumed 6.789 0.018* -2.982 18 0.008** -156.00 52.307 -265.892 -46.108 Equal variance not assumed -2.982 12664 0.011* -156.00 52.307 -269.308 -42.692 *
P<0.05; ** P<0.01
On comparison, we find that as myopic anisometropic
persons have scored mean value of 120 sec of arc, which is closer to the normal
value that is 60 sec of arc as compared to the mean value for stereopsis scored
by hyperopic anisometropic subjects that is 276 sec of arc, which is less close
to the normal value for stereopsis (Table 1). In this table P-value of
being less than 0.05 i.e., 0.008 shows that there is difference between the
mean effects of the myopic and hyperopic anisometropes which makes it statistically
significant. Our results showed that both the myopic and hyperopic
anisometropic persons have decreased levels of stereopsis than that of normal
value, but this reduction is more obvious among hyperopic anisometropes as
compared to the myopic anisometropes.
DISCUSSION
Another study
which agrees to our results that spherical hyperopic anisometropia had much
adverse effects on binocular visual functions and stereopsis than that of
myopic anisometropia (Weakley 2001). Previous research suggested that
anisometropia causes reduction of stereopsis in myopic and hyperopic forms of
anisometropes, which makes an agreement to the results of our study but
disagrees when his results says that these reduced changes are more significant
among myopic type of anisometropia. This opposition is due to the fact that
previous study experimentally induced anisometropia on emmetropes to carry out
his study, but we have assessed stereopsis on subjects having refractive
anisometropia and our results disagree to that research results because our
results show that reduction of stereopsis is more obvious among hyperopic form
of anisometropia as compared to the myopic form of anisometropia (Nabie et
al. 2017).
According to
past research, increasing degree of anisometropia causes decrease in the levels
of stereopsis which supports the results of our study. Likewise, it has been
found in the study that anisometropia has adverse effects on stereopsis which
also agree to our study (Tarczy-hornoch et
al. 2011). Lee et al. (2013) reported that wearing glasses was
better in myopic anisometropia as compared to the hyperopic anisometropia that
agree to our study but they also concluded that the stereopsis was clinically
normal in anisometric patients wearing their subjective corrections despite of
the extent of anisometropia, that contradicts our findings, our study found
that there is decrease in stereoacuity with increasing degree of anisometropia.
CONCLUSION
Our results showed that Anisometropia has worse
effects on stereopsis in both myopic and hyperopic forms of anisometropia. Loss
of stereopsis is more significant in hyperopic anisometropia as compared to
myopic anisometropia. anisometropia causes a reduction of stereopsis, which in
turn affects the quality of life of patients. This study suggests making
stereopsis an integral part of routine examination. Patients, especially those
of a younger age, should be carefully treated as their chances of developing
amblyopia is common with anisometropia.
ACKNOWLEDGMENTS
The authors would like to express their sincere gratitude to all faculty
of Optometry who contributed to the successful completion of this research
AUTHOR CONTRIBUTIONS
SA: Conceptualization of study design, data analysis, data
interpretation; AK: Data collection, data analysis; QA: Data collection,
write-up; ZR: Literature search; RFN: Literature search, write-up
CONFLICTS OF INTEREST
The authors declare that they have no conflicts of
interest
DATA AVAILABILITY
The data will be made available on a fair request to
the corresponding author
ETHICS APPROVAL
Not applicable
FUNDING SOURCE
This project is not funded by any agency
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