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Year : 2019  |  Volume : 57  |  Issue : 1  |  Page : 27-30

Prevalence of convergence insufficiency between 18 and 35 years and its relation to body mass index

Department of Ophthalmology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth, Puducherry, India

Date of Web Publication10-Jun-2019

Correspondence Address:
Dr. Kirti Nath Jha
Department of Ophthalmology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth, Puducherry - 607 402
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjosr.tjosr_11_19

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Background: Convergence insufficiency (CI) is a common condition characterized by patient's inability to maintain binocular alignment on objects as they approach from distance to near. One study has found association between low body mass index (BMI) and CI. The purpose of this study is to find the prevalence of CI and its association with BMI among patients aged 18–35 years. Subjects and Methods: In a prospective study, we recorded convergence among individuals aged 18–35 years. We defined CI as near point of convergence of >10 cm, exophoria greater for near than distance, and positive fusional vergence of <18 ΔD. The prevalence of CI was expressed as percentage of the population. BMI was calculated. We calculated the association between CI and BMI by Chi-square test. P < 0.05 was considered as statistically significant. Results: We studied 142 individuals (male: 61 and female: 81). CI was noted in 27.5% of population; 53.84% of these were symptomatic as per symptom survey questionnaire. The average BMI of the study population was 23.78 ± 4.68. No association was found between BMI and CI (P = 0.773). Conclusions: Among 18–35 years of age, 27.5% of individuals exhibited CI. CI and BMI did not show any association.

Keywords: Body mass index, convergence insufficiency, ocular motility disorder

How to cite this article:
Vaishali RS, Jha KN, Srikanth K. Prevalence of convergence insufficiency between 18 and 35 years and its relation to body mass index. TNOA J Ophthalmic Sci Res 2019;57:27-30

How to cite this URL:
Vaishali RS, Jha KN, Srikanth K. Prevalence of convergence insufficiency between 18 and 35 years and its relation to body mass index. TNOA J Ophthalmic Sci Res [serial online] 2019 [cited 2022 Jul 3];57:27-30. Available from: https://www.tnoajosr.com/text.asp?2019/57/1/27/259868

  Introduction Top

Convergence insufficiency (CI) is the inability to accurately converge or to maintain convergence at near.[1] CI leads to asthenopia during near tasks. The symptoms can vary from redness, pain in and around the eyes, blurred vision, frontal headache, and intermittent diplopia for near vision.[2] CI has been acknowledged as a common and treatable condition. However, the scale of the problem is still not very clear. This is because population-based epidemiological studies have not been done. There is great variability in the reported prevalence of CI from 1.75% to 33%.[2]

Body mass index (BMI) is a measure used internationally to calculate whether a person's weight is ideal. High BMI has been associated with a lot of ocular disorders such as glaucoma, age-related macular degeneration, and optic disc cupping.[3]

So far, one study has revealed that most of the patients diagnosed with CI have low BMI.[3] Much information is not available regarding BMI and its relation to CI.

The purpose of this study is to understand the extent of CI in 18–35 years' age group and also to find its association, if any, with BMI.

  Subjects and Methods Top

It was a prospective, observational study conducted on all patients within the age group of 18–35 years who came to the ophthalmology outpatient department (OPD) in a tertiary health care center. One hundred and forty-two patients within the age group of 18–35 years who come to the ophthalmology OPD fulfilling the criteria formed the study sample. The study was approved by the Institutional Human Ethics Committee and adhered to the principles in the Declaration of Helsinki. Informed consent was obtained from all participants. Patients with strabismus, any infective ocular pathology, history of previous ocular surgery, pregnancy, history of hospitalization within 3 months for any systemic illness, postpartum period, and history of ocular trauma were excluded from the study. Detailed history was obtained from all participants, and thorough ophthalmic examination was done. Best corrected visual acuity was recorded followed by cover test; exophoria for near and distance was measured by Maddox wing and Maddox rod, respectively; near point of convergence (NPC) and near point of accommodation (NPA) were measured using Royal Air Force ruler; and positive fusional vergence was measured with prism bar using an accommodative target and using the synoptophore fusion slides. Ocular examination was done with slit-lamp biomicroscopy, and fundus was evaluated with 90-D lens. All patients were asked to fill out the CI Symptom Survey (CISS) questionnaire. We defined CI as (1) exophoria for near, (2) exophoria greater for near than for distance, (3) NPC >10 cm, and (4) positive fusional vergence <18 ΔD. Statistical analysis was carried out using SPSS version 19.0 (IBM SPSS, US) software with Regression Modules installed. Descriptive analyses were reported as mean and standard deviation (SD) of continuous variables. Chi-Square test was used to find out the correlation between CI and BMI. P <0.05 was considered as statistically significant.

  Results Top

One hundred and forty-two participants aged between 18 and 35 years participated in this study. There were 61 males (42.95%) and 81 females (57.04%). Mean age of the participants was 26.54 ± 17.45 years; mean ± SD of males was 24.55 ± 4.48 and females was 25.56 ± 5.51. Difference of age between the sexes was not statistically significant (P = 0.231).

The mean of BMI in males and females were 24.47 ± 4.56 and 23.25 ± 4.74, respectively. The Chi-Square test does not show statistically significant difference in distribution of BMI between males and females (P = 0.356).

The prevalence of CI between 18 and 35 years of age was found to be 27.46% (n = 39) [Figure 1], of which males were 33.33% (n = 13) and females were 66.66% (n = 26).
Figure 1: Prevalence of convergence insufficiency

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About 12.7% of the participants were found to have fusional vergence dysfunction (FVD), which was an incidental finding. The ratio of prevalence of FVD between males and females was 1:1.

[Table 1] shows the relationship between CI and BMI. Data show no statistically significant association between CI and BMI (P = 0.773).
Table 1: Association between convergence insufficiency and body mass index

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[Table 2] shows NPC, NPA, base-in break, base-out break, abduction, adduction, and exophoria in different states of BMI. There is no statistically significant difference in the various binocular vision tests in the different states of BMI.
Table 2: Mean and standard deviation of binocular vision tests in various states of body mass index

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Among 39 people with CI, 53.84% (n = 21) of the CI patients were found to be symptomatic based on the CISS questionnaire; there were 23.8% (n = 5) males and 76.19% (n = 16) females. However, based on the history, 76.92% (n = 30) of the patients presented with at least one symptom that caused significant asthenopia during near tasks. [Figure 2] shows the distribution of symptoms (%) among patients with CI.
Figure 2: Distribution of symptoms among patients with convergence insufficiency

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Of the 39 people with CI, 33.33% (n = 13) were found to have refractive error. Of the 39 people with CI, 10.25% (n = 4) had myopia and 23.07% (n = 9) had myopic astigmatism.

No significant relation was found between CI and refractive error [Table 3].
Table 3: Association between convergence insufficiency and refractive error

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  Discussion Top

Vergence anomalies have become more troublesome in the current times as computer usage and near tasks have increased over the past few decades.[4] CI is the most predominant and treatable form of vergence anomaly.[4] Patients with CI develop ocular fatigue due to breakdown of binocular vision system leading to asthenopia during near tasks.

Published literature reports a high variability (1.75%–33%) in the prevalence of CI. However, there is a dearth of population-based studies in the literature.[2] In our study, we found a high prevalence of CI (27.5%) among young (18–35 years) age group. This was corresponding with findings of a similar study by Ovenseri-Ogbomo and Eguegu, done between the age group of 15 and 28 years.[5] They in their study reported a prevalence of CI of 29.6%. However, Horwood et al. reported that the prevalence of CI among young individuals is not significant (10%), and hence, it is not mandatory to screen them.[6] Mahto reported a higher incidence of CI in women than in men with a females and males ratio of 3:2.[7] Our study also observed similar findings (female: 66.66% and male: 33.33%). However, few studies have reported that there is equal incidence of CI in both men and women.[5],[8] One report states that FVD is the most common form of vergence anomaly next to CI.[9] However, no other study substantiates this statement.

BMI has been found to be an important indicator of biological function and nutritional health. However, not much literature is available on the effect of BMI on the eye or binocular function. Studies done so far have found no correlation between ocular disorders and BMI.[10],[11] Most often, high BMI has been associated with impaired health. Surprisingly, a study by Momeni-Moghaddam et al. showed association between low BMI and weak binocular function.[3] We did not find such an association in our study (P = 0.773).

The most commonly reported symptoms in the patients with CI in our study were headache (76.92%) and eye pain (76.92%) followed by soreness of the eyes (55.41%), watering (46.15%), blurring of vision (42.02%), and intermittent diplopia (20.51%). Previous studies have also noted similar symptoms among participants with CI.[2],[12] Although the CISS questionnaire was found reliable, it was contradicted by Horwood et al. as it had poor sensitivity and a high false-positive rate.[6] This is attributed to the fact that the questionnaire is sensitive only when the patient presents with diverse symptoms which lead to asthenopia and not just a single symptom which is significant enough to cause asthenopia.[2] Similarly, in our study, according to the CISS questionnaire score, only 53.84% of our patients were found symptomatic. However, 76.92% of the patients had one symptom which was causing asthenopia.

Dwyer and Wick reported that the correction of ametropia helps in resolution of CI.[13] However, no studies show any correlation between the presence of vergence dysfunction and refractive error. This study shows no correlation between CI and refractive error.


Our study population has limited proportion of participants with low BMI. Therefore, it is difficult to opine whether low BMI is associated with CI.

  Conclusions Top

Among 18–35 years' age group, 27.5% of individuals exhibited CI. No correlation exists between CI and BMI (P = 0.773). A population-based study will help understand the distribution of CI across the age groups and reveal its association with BMI.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Davis AL, Harvey EM, Twelker JD, Miller JM, Leonard-Green T, Campus I, et al. Convergence insufficiency, accommodative insufficiency, visual symptoms, and astigmatism in Tohono O'odham students. J Ophthalmol 2016;1-7.  Back to cited text no. 1
Cooper J, Jamal N. Convergence insufficiency – A major review. Optometry 2012;83:137-58.  Back to cited text no. 2
Momeni-Moghaddam H, Kundart J, Ehsani M, Abdeh-Kykha A. Body mass index and binocular vision skills. Saudi J Ophthalmol 2012;26:331-4.  Back to cited text no. 3
Cooper J, Burns C, Cotter S, Daum KM, Griffin J, Scheiman M. Care of the Patient with Accommodative and Vergence Dysfunction. St. Louis: American Optometric Association; 2011.  Back to cited text no. 4
Ovenseri-Ogbomo GO, Eguegu OP. Vergence findings and horizontal vergence dysfunction among first year university students in Benin city, Nigeria. J Optom 2016;9:258-63.  Back to cited text no. 5
Horwood AM, Toor S, Riddell PM. Screening for convergence insufficiency using the CISS is not indicated in young adults. Br J Ophthalmol 2014;98:679-83.  Back to cited text no. 6
Mahto RS. Eye strain from convergence insufficiency. Br Med J 1972;2:564-5.  Back to cited text no. 7
Convergence Insufficiency Treatment Trial Study Group. Randomized clinical trial of treatments for symptomatic convergence insufficiency in children. Arch Ophthalmol 2008;126:1336-49.  Back to cited text no. 8
Scheiman M, Wick B, editors. Clinical Management of Binocular Vision: Heterophoric, Accommodative, and Eye Movement Disorders. 4th Rev. ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2014.  Back to cited text no. 9
Norn MS. Convergence insufficiency: Incidence in ophthalmic practice and results of orthoptic treatment. Acta Ophthalmol (Copenh) 1966;44:132-8.  Back to cited text no. 10
Ernest-Nwoke IO, Ozor MO, Akpamu U, Oyakhire MO. Relationship between body mass index, blood pressure, and visual acuity in residents of Esan West local government area of Edo state, Nigeria. Physiol J 2014;2014:1-5.  Back to cited text no. 11
Kent PR, Steeve JH. Convergence insufficiency, incidence among military personnel and relief by orthoptic methods. Mil Surg 1953;112:202-5.  Back to cited text no. 12
Dwyer P, Wick B. The influence of refractive correction upon disorders of vergence and accommodation. Optom Vis Sci 1995;72:224-32.  Back to cited text no. 13


  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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