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 Table of Contents  
Year : 2017  |  Volume : 29  |  Issue : 2  |  Page : 97-101

Retrospective study of effect of therapy on computer vision syndrome patients having convergence insufficiency

1 Department of Ophthalmology, Consultant, Sankara Eye Hospital, Bengaluru, Karnataka, India
2 Department of Optometrist, Consultant, Sankara Eye Hospital, Bengaluru, Karnataka, India
3 Fellow, Consultant, Sankara Eye Hospital, Bengaluru, Karnataka, India

Date of Web Publication10-Aug-2017

Correspondence Address:
Prajakta Paritekar
Anusaya Apt, Near DNS Bank Kulgaon Badlapur (East), Thane, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/kjo.kjo_77_17

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Aim: To study effect of therapy among computer users having convergence insufficiency.
Materials and Methods: Hundred people between age group of 20-35 and who worked in IT companies were enrolled in the study. They were subjected to orthoptic evaluation to establish diagnosis of convergence insufficiency. They were then called for in-office therapy for 12 days daily. They underwent brock string exercises and at the end of therapy re-evaluation was done.
Results: All the patients who underwent the therapy showed improvement in Near point of convergence at the end of therapy. They were also symptomatically better.
Conclusions: Convergence insufficiency is a common occupation hazard among IT professionals. But it can be treated with appropriate therapy.

Keywords: Computer users, convergence Insufficiency, therapy

How to cite this article:
Tiwari N, Paul U, Paritekar P. Retrospective study of effect of therapy on computer vision syndrome patients having convergence insufficiency. Kerala J Ophthalmol 2017;29:97-101

How to cite this URL:
Tiwari N, Paul U, Paritekar P. Retrospective study of effect of therapy on computer vision syndrome patients having convergence insufficiency. Kerala J Ophthalmol [serial online] 2017 [cited 2021 May 7];29:97-101. Available from: http://www.kjophthal.com/text.asp?2017/29/2/97/212762

  Introduction Top

“Necessity is the mother of invention.”

This saying is very appropriate in the current era of computers. In the good old days, most of the works were done on typewriters. However, then to minimize manual labor and save time, man invented computers. Computer indeed played a very important role in gaining more and more productivity nowadays but at the cost of its own hazards.

Computer vision syndrome is a well-known hazard among prolonged computer uses. It ranges as high as between 64% and 90%.[1] Eyestrain is one of the major symptoms of computer vergence system (CVS).[2] It is mainly due to convergence insufficiency (CI).

CI is a common binocular disorder affecting as much as 4%– 6% of the population.[3],[4],[5],[6] It is more among people doing prolonged near work such as reading, writing, and computer use.[7],[8] According to a study conducted by the National Institute of Occupational Safety And Health, USA indicates that 88% of people working on the computer more than 3 h a day suffer from symptoms of eye strain.

The need of this study was to create awareness among people who use computers for long time to undergo thorough evaluation and take the home-based as well as office-based therapy to get rid off the eye problems to maintain healthy and clear vision.

Aims and objectives

  1. To diagnose CI in prolonged computer workers (IT professional's) who present to our hospital with complaints of blurring of vision and eye strain
  2. To assess the improvement in above patients after thorough home- and office-based vision therapy.

Inclusion criteria

  1. Computer professionals working in IT company with minimum of 1-year experience
  2. Age group between 20 and 35 years
  3. Willing to participate in the study.

Exclusion criteria

  1. One-eyed patients
  2. Patients with media opacity
  3. Patients with preexisting manifest squint
  4. Visual acuity not correctable to 6/6.

  Materials and Methods Top


  1. Snellen's visual acuity chart to check visual acuity for distance
  2. Jaeger's chart for recording near visual acuity
  3. Heine retinoscope for retinoscopy
  4. Trial lens set for subjective refraction
  5. Maddox Rod to detect horizontal phorias
  6. Prism bar to perform prism bar cover test
  7. Camlin long scale to measure nasopharyngeal airway, nasopharyngeal carcinoma (NPC)
  8. Pen– accommodative target
  9. Brock String for therapy.


  1. Patients who fit in the inclusion criteria were referred to the vision therapy clinic
  2. Visual acuity for distance was recorded using Snellen's visual acuity chart at 6 m distance
  3. Near visual acuity was recorded using Jaeger's chart
  4. Dry retinoscopy was performed using Heine streak retinoscope
  5. Best-corrected visual acuity was noted after subjective acceptance
  6. Cover test was performed to diagnose phoria
  7. Prism bar cover test was performed to quantitate the phoria
  8. Near point of convergence was measured using a long scale and an object– pen
  9. Subjective response being diplopia and objective response being divergence was noted
  10. Breakpoint of convergence and recovery point was noted
  11. Fusional vergence amplitude was noted using prism bar
  12. Patients were given the full correction of glasses
  13. Seven days continuous in-office therapy and home therapy was advised
  14. Brock string exercises were done as in-office therapy, and pencil push-up exercises were advised as home therapy
  15. Reevaluation was done after 7 days
  16. Same parameters as pretherapy were noted and patients who did not show improvement were advised to come for one more session of therapy.

  Results Top

The statistical analysis was performed by STATA 11.2 (College Station, TX, USA). Shapiro-Wilk test has been used to check the normality. Student's paired t-test has been used to find the pre- and post-comparison of break, recovery, and objective and its expressed as mean and standard deviation. P <0.05 considered statistically significant.

This was a retrospective study conducted over a period of 1 year. A Hundred patients who fulfill the inclusion and exclusion criteria were included in this study. Mean age was 27.5 years.

52% were male, and 48% were female.

The break point in subjective measurement of NPC (without accommodative target) was 13.81 in pretherapy group and 9.94 in posttherapy group. This difference was statistically significant (P < 0.0001).

The recovery point in subjective measurement of NPC (without accommodative target) was 15.03 in pretherapy group and 9.79 in posttherapy group. This difference was statistically significant (P < 0.0001).

The objective value of measurement of NPC (without accommodative target) was 13.91 in pretherapy group and 9.09 in posttherapy group. This value was statistically significant (P < 0.0001).

The break point in subjective measurement of NPC (with accommodative target) was 14.73 in pretherapy group and 9.09 in posttherapy group. This difference was statistically significant (P < 0.0001).

The recovery point in subjective measurement of NPC (with accommodative target) was 15.39 in pretherapy group and 9.74 in posttherapy group. This difference was statistically significant (P < 0.0001).

The objective value of measurement of NPC (with accommodative target) was 15.30 in pretherapy group and 9.09 in posttherapy group This value was statistically significant (P < 0.0001).

The break point in measurement of positive fusional vergence in pretherapy group was 15.24 and in posttherapy group was 24.79. This difference is statistically significant (P < 0.0001).

The recovery point in measurement of positive fusional vergence in pretherapy group was 16.60 and in posttherapy group was 34.53. This difference is statistically significant (P < 0.0001).

Out of 100 patients, only 13% required additional therapy.

  Discussion Top

Computer vision syndrome is a term that describes eye-related problems and the other symptoms caused by computer used. As our dependence on computer continues to grow, an increasing number of people are seeking medical attention for eye strain and irritation, along with back, neck, shoulder, and wrist soreness. These problems are more noticeable with computer tasks than other near work because letter on the screen is form by tiny dots called pixels rather than a solid image. This causes the eyes to work a bit harder to keep the images in focus.

Victims of computer vision syndrome experience many frustrating symptoms, CI being one of the causes for them.

CI is characterized by a decreased ability to converge the eyes and maintain binocular fusion while focusing on a near target. CI is usually accompanied by a reduced near point of convergence (NPC), decreased convergence amplitudes, or an exodeviation (usually >10 prism diopters) at near. Patients often complain of eye strain when reading, closing one eye when reading, or blurred vision after short periods of near work. The diagnosis of primary CI is based on the patient's presenting symptoms and the aforementioned clinical signs.[9],[10],[11]

First described by von Graefe in 1855, CI was previously thought to be myogenic or even psychogenic in origin, with the asthenopic symptoms manageable by orthoptics treatment, but ultimately incurable. It is currently believed to have an innervational etiology; and only recently has vision therapy been established as an effective treatment.[12] Heretofore, management of CI has comprised a variety of treatments with little consensus or standard. Treatment modalities have included pencil pushups, in-office orthoptics training, base-in prism reading glasses, and computer-based training exercises. 14 As a result of findings from clinical studies conducted by the CI Treatment Trial investigator group, in-office vision therapy supplemented by home reinforcement has now been established as the most effective treatment for primary CI, showing a significant reduction in symptoms in 73% of those treated.


  1. Headache
  2. Diplopia
  3. Blurred vision
  4. Loss of concentration
  5. Tiredness while reading
  6. Dry eye (especially in people who work on computers).

CI can be either primary or secondary to an underlying etiology. In primary CI, the deviation is comitant and the patient reports long-standing symptoms with a negative health history. Whereas, a secondary CI (or, potentially, a convergence paralysis) may be associated with precipitating factors such as a mild traumatic brain injury, neurodegenerative disease such as Parkinson's disease, microvascular event, or secondary to accommodative insufficiency, also known as a pseudo-CI.


  1. Receeded near point of convergence breakpoint
  2. Exophoria greater at near than at distance by at least four prism diopters
  3. Positive fusional vergence that is insufficient to meet demands.

Sensorimotor findings

  1. Phorias Passmore and Maclean [13] noted that 79% of their patients with CI had exophoria at near. Cushman and Burri [12] reported that 63% of CI patients exhibited an exophoria on cover testing at near. Hence, patients with CI tend to have large exophorias for near
  2. Fusional convergence The majority of patients with CI have insufficient phase field crystal (PFC) amplitudes at near. Duane [14] stated that a CI frequently (had) decreased the abduction of 5° – 6° (~8– 10 Δ ), but not more than 9° (~15 Δ ), prism convergence usually decreased to 8° – 12° (~14 20 Δ ) or less. Low PFC is associated with asthenopic symptoms
  3. Near point of convergence The near point of convergence is the point to which the lines of sight are directed when convergence is at its maximum. According to Duane,[14] a receded NPC (NPC 0.3 inches or 7.5 cm) is the most consistent clinical sign found in persons with CI. Although the NPC is an easy clinical test to administer, there has not been consensus on how the test should be performed, with methodology varying from study to study
  4. Poor accommodation is also attributed to the possibility of CI.

Treatment of convergence insufficiency

General treatment

Orthoptic therapy is the primary treatment modality used by most eye care professionals for the treatment of CI. The plasticity of the fusional convergence reflex system allows patients to improve their convergence amplitudes with simple exercises. There are numerous different types of eye exercises; however, the primary treatment modalities for CI include home-based exercise, in-office exercises, computer vergence exercises, or a combination of these.

Conventional convergence exercises

Those utilizing voluntary convergence exercises are:

  1. Gradual convergence exercises (pencil pushups)
  2. Convergence cards
  3. Stereograms.

Others include

  1. Vergence facility exercise Exercise that has the patient look from a target at near to a target at distance with rapid fixation switches.

Prism-based therapy

  1. Base out prism exercise The base out prism induces crossed diplopia, and the patient must converge to overcome the prism strength and obtain binocular single vision
  2. Base in reading glasses Approximately, four prism diopters are prescribed in the spectacle.

Computer-based convergence exercise

A computer-based orthoptic program known as CVS is used by many eye care professionals. The program uses random dot stereograms to form pictures that require bifoveal fixation to stimulate the vergence system. The program gradually increases the amount of vergence required to appreciate the stereogram picture and can monitor progression online.

Office-based vision therapy

Office-based vision therapy requires a patient to undergo a specific therapy regimen with regular office visits (e.g., once or twice per week). Typically, the therapy is administered by a therapist in the office and supplemented with various home therapy procedures that are prescribed to be performed at home 5– 7 days per week. The estimated time of treatment for a person with CI is typically 10– 20 office visits.

Brock string exercises

During therapy, the one end of the Brock string is held on the tip of the nose while the other is tied to a fixed point. The three beads are spaced out at various distances. The patient is asked to focus on one of the beads while noting the visual input of each eye and sensation of convergence. The patient can use variable techniques to make easier or more difficult by bringing the beads closer/further to the nose and by employing lenses and prisms.

There are other treatments pertaining to other complaints of the patients with computer vision syndrome.

For example,

  • Dry eyes are treated by prescribing lubricating eye drops
  • Computer screen should be lowered
  • Video display terminals should have antiglare covering.

Following all these remedies and undergoing appropriate eye muscle therapy, a computer professional can make his work more comfortable!

  Conclusion Top

We would like to emphasize that:

  1. People who work on computers for long hours tend to develop CI
  2. Strain and headache associated with CI is very distressing for the patients
  3. Early diagnosis helps in early treatment and early alleviation of symptoms
  4. In majority of cases, a continuous 7 day in-office therapy with simple home exercises is sufficient to correct the insufficiency
  5. Some patients require two sessions of therapy to totally correct the insufficiency.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Hayes JR, Sheedy JE, Stelmack JA, Heaney CA. Computer use, symptoms, and quality of life. Optom Vis Sci 2007;84:738-44.  Back to cited text no. 1
Ranasinghe P, Wathurapatha WS, Perera YS, Lamabadusuriya DA, Kulatunga S, Jayawardana N, et al. Computer vision syndrome among computer office workers in a developing country: An evaluation of prevalence and risk factors. BMC Res Notes 2016;9:150.  Back to cited text no. 2
Rouse MW, Borsting E, Hyman L, Hussein M, Cotter SA, Flynn M, et al. Frequency of convergence insufficiency among fifth and sixth graders. The Convergence Insufficiency and Reading Study (CIRS) group. Optom Vis Sci 1999;76:643-9.  Back to cited text no. 3
Letourneau JE, Ducie S. Prevalence of convergence insufficiency among elementary school children. Can J Optom 1988;50:194-7.  Back to cited text no. 4
Scheiman M, Gallaway M, Coulter R, Reinstein F, Ciner E, Herzberg C, et al. Prevalence of vision and ocular disease conditions in a clinical pediatric population. J Am Optom Assoc 1996;67:193-202.  Back to cited text no. 5
Porcar E, Martinez-Palomera A. Prevalence of general binocular dysfunctions in a population of university students. Optom Vis Sci 1997;74:111-3.  Back to cited text no. 6
Daum KM. Convergence insufficiency. Am J Optom Physiol Opt 1984;61:16-22.  Back to cited text no. 7
Cooper J, Duckman R. Convergence insufficiency: Incidence, diagnosis, and treatment. J Am Optom Assoc 1978;49:673-80.  Back to cited text no. 8
American Academy of Ophthalmology. Basic and clinical science course. Pediatric Ophthalmology and Strabismus. Sec. 6. San Francisco: American Academy of Ophthalmology; 2006.  Back to cited text no. 9
Arnoldi K, Reynolds JD. A review of convergence insufficiency: What are we really accomplishing with exercises? Am Orthopt J 2007;57:123-30.  Back to cited text no. 10
von Noorden GK, Campos E. Theory and management of strabismus. Binocular Vision and Ocular Motility. 6th ed. St. Louis: Mosby; 2002.  Back to cited text no. 11
Cushman N, Burri C. Convergence insufficiency. Am J Ophthalmol 1941;24:1044-52.  Back to cited text no. 12
Passmore JW, Maclean F. Convergence insufficiency and its managements; an evaluation of 100 patients receiving a course of orthoptics. Am J Ophthalmol 1957;43:448-56.  Back to cited text no. 13
Duane A. A new classification of motor anomalies of the eye based upon physiological principles. Ann Ophthalmot Otolarngol 1886;3:247-60.  Back to cited text no. 14

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