Introduction
Headache is defined as pain or discomfort arising from any pain-sensitive structures in the head.1 Headache is one of the most common symptoms for patients seeking medical attention. In the Global Burden of Disease Study, updated in 2013, Headache disorders collectively were the highest cause worldwide of years lost due to disability (YLD).2
Even though the evidence in the literature for a strong association between ocular diseases and headache is weak, Ophthalmologists are usually the first physicians to evaluate patients with headaches. Refractive errors, presbyopia, binocular vision anomalies, glaucoma, inflammatory diseases, computer vision syndrome are the common ocular causes for headache.3
Convergence insufficiency (CI) is a common dysfunction of binocular vision. Convergence insufficiency (CI) is the inability to accurately converge or to maintain convergence at near. The symptoms can vary from redness, pain in and around the eyes, blurred vision, frontal headache, and intermittent diplopia for near vision. In literature, the prevalence of Convergence Insufficiency varies widely ranging from 2 % to 27%.4, 5 Binocular vision anomalies have been a major cause of headache which goes undetected due to neglect towards this aspect as a cause of headache.
In this study, the association between Convergence insufficiency and headache was evaluated.
Materials and Methods
It was a prospective cross-sectional study conducted in the department of Ophthalmology, at a tertiary eye care hospital. The approval from the Institutional ethics committee and an informed written consent from the patients was obtained.
The study included 84 patients with complaints of headache who either had come by their own or were referred from other departments to the department of Ophthalmology. Patients were also referred to other departments to rule out non-ocular cause of headache.
Exclusion criteria
Age > 36 years of age, unco-operative patients, any patients with strabismus, inflammatory ocular diseases, post ocular surgery/ trauma, pregnancy, recent history of hospitalization (within 3 months before the date of examination) for any systemic illness.
Detailed history was obtained from all the participants regarding the demographic profile, the headache pattern and asthenopic symptoms. Ocular evaluation consisted of detailed refractive check-up with retinoscopy, binocular vision assessment and anterior segment by slit lamp examination and posterior segment examination by +90 D with slit lamp biomicroscopy.
Refractive errors were classified as myopia, hyperopia and astigmatism. Myopia was defined as a spherical equivalent of ≥ −0.50 Diopters (D), hyperopia was defined as a spherical equivalent of ≥ +0.50 D, astigmatism was defined as the cylindrical component of the refractive error more than 0.50 D.
CI is defined as Near Point of Convergence (NPC) >10 cm, positive fusional vergence and exophoria greater for near than for distance. Near point of Convergence (NPC) and Near point of Accomodation (NPA) was measured with a Royal Air Force (RAF) ruler. Fusional reserves were measured with a vertical bar prism using an accommodative target. Near base-in and base-out fusional reserves were recorded at the break point. Heterophoria was measured first, followed by divergence amplitudes and then convergence amplitudes to prevent vergence adaptation.
Data was entered in Microsoft excel sheet. These individual data were analysed by Percentage and Chi square test.P value < 0.05 is considered statistically significant.
Results
A total of 84 patients with headache complaints participated in the study. Females constituted the majority of patients (66.6%) and males (33.3%).
Table 1
Age distribution in headache patients
|
Age |
Percent |
|
0-9 years |
2.4 |
|
10 -19 years |
50.0 |
|
20- 29 years |
28.6 |
|
30 – 35 years |
19.0 |
|
Total |
100.0 |
50% was in the school going age group 10 – 19 years. Among the participants, 57.14 % were students (both school and college), 28.57% were home makers and 2.3% had computer related works.
Among the headache patients, astigmatism was seen in 59.6%; mainly myopic astigmatism seen in 31%. Emmetropia was seen in 33.3% , myopia 4.8 % and hypermetropia in 2.4%.
Abnormal Near point of convergence > 10 cm was seen in 26.2 % of headache patients. Base out prism value less than 18ΔD was seen in 23.8 %. In this study, the prevalence of Convergence Insufficiency was 26.2% among headache patients.
Table 2
Age and convergence insufficiency.
|
Age |
Percentage of CI |
|
5 -9 years |
0 |
|
10 – 19 years |
36.4% |
|
20 – 29 years |
36.4 % |
|
30 – 35years |
27.3 % |
72.8% of CI was seen in young patients. CI was more common in female patients (63.6%) than in male patients (36.4%) in our study. House wives were commonly affected (45.5 %) when compared with the students (36.4%).
Table 3
Type of headache and Convergence insufficiency
|
Type Headache |
Percent in CI |
|
Frontal |
78.7% |
|
Occipital |
9.09% |
|
Diffuse |
9.09% |
|
Others |
9.09% |
Frontal headache was seen in 78.7% of patients with CI. The frequency of other symptoms were defective vision 36.4 %, eye strain 45.5 % and Eye pain 54.5 %. Intermittent diplopia was not seen in any patients.
In this study, astigmatism was seen in 45.5% of CI patients, followed by emmetropia (36.4%). 72.7% of CI patients had vision between 6/12 to 6/6.
Table 4
Association between Base out prism and NPC
Table 4 show the between Base out prism and NPC is found to be statistically significant with Chi-Square value: 23.85 (p-value < 0.005)
The association between Base out prism and eye pain is found to be statistically significant with Chi-Square value: 6.74 (p-value < 0.005). The association between eye pain and NPC is found to be statistically significant with Chi-Square value: 19.21 (p-value < 0.005). Age group, gender, occupation, other symptoms were not statistically significant.
Discussion
In this era of increased technological use of computers and cell phones, the importance of binocular vision anomalies have become more significant. CI is the most common and the easily treatable vergence anomaly.
In this study, the prevalence of Convergence Insufficiency was 26.2% among headache patients. This prevalence is less than Garg et al 6 (39.19%) but more than Sanjay et al 7 (16.25%) and Amy et al8 (18.7%). The prevalence is similar to Vaishali RS et al 5 (27.5%). These discrepancies might be due to different occupation of the patients in the study group.
72.8% of CI patients were in the age group 10 -29 years. Females outnumbered males in a ratio of 2:1 with 36.4% males and 63.6% females. These findings correlates with the literature.6, 7 Since young patients has more stress in their academics and profession, headache is more common in this group and they seek medical advice frequently.
The association between Base out prism break with abnormal NPC was statistically significant. Base out prisms abolishes the fusion and causes diplopia, causing strain on the convergence system to maintain binocular single vision. In case of CI, the amplitude of fusional vergence is less and so these patients cannot converge with Base out prisms. These patients will be more symptomatic. This correlates with our finding where the association between Base out prism and eye pain is found to be statistically significant.
Near point of convergence (NPC) is the point where the binocular single vision is maintained with maximum effort of the convergence when a near target is presented. In CI, NPC value increases.
Frontal headache (78.7%) was frequently associated with CI in our study similar to Garg et al6 and Sanjay et al.7 Asthenopic symptoms were seen in 82 % of CI patients, asymptomatic in 18%). The asthenopic symptoms are frequent when the NPC and Base out prism values are more deranged.
In our study, CI was commonly seen in astigmatism (45.5%). This correlates with Amy et al8 and Sanjay et al.7 Headache is frequently associated with astigmatism.9 In this study , since headache patients were the study population, CI is frequently associated with astigmatism. Gupta et al10 reported that CI was common in myopia. Vaishali RS et al 5 reported no correlation between CI and refractive error.
Conclusion
This study provides the evidence that vergence anomalies are frequently associated with headache. But exact percentage of these anomalies causing headache needs further study as these anomalies are associated with refractive error often. We conclude that thorough refractive evaluation and binocularity evaluation are important in patients presenting with headache especially in younger age group as their demand for near work is very high in this technology driven era. With early detection of convergence insufficiency, quality of vision and life can be maintained.
