Home Vision Therapy and Prism Prescription in Presbyopic Persons With Convergence Insufficiency
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ClinicalTrials.gov Identifier: NCT05311917 |
Recruitment Status :
Not yet recruiting
First Posted : April 5, 2022
Last Update Posted : April 22, 2022
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convergence insufficiency is one of the most common binocular vision problems in which the eyes tend to have more exophoria in near than distance activities. Its prevalence is typically reported from 2.25% to 29.6% depending on the study population and its definition. Most of its symptoms include difficulty seeing at close works, headache, eye pain during study, blurred vision, diplopia, movement of words in reading, a feeling of pressure in the eye, and lack of concentration. Its signs include increasing near point of convergence, more exophoria at near than distance, decreased AC / A ratio, decreased positive fusional vergence.
In patients with convergent insufficiency, the first valid and standard questionnaire to assess the frequency and type of symptoms used before and after convergence insufficiency treatment is the convergence insufficiency symptom survey (CISS) questionnaire.
Generally, vision therapy is the first choice for convergence insufficiency management and the other choice is base in prism prescription. On the other hand, due to the changes in the interaction of the accommodation and convergence systems with increasing age, It is necessary to study how these systems interact and compare their responses to the active treatment of vision therapy and inactive prescription of base in prism.
In this controlled study, investigators will evaluate and compare the effect of vision therapy and base in prism prescription in patients over 40 years of age. this investigation will help to clarify which treatment is more effective.
This study will have two phases. In the first phase, investigators will seek to check the reliability and validity of the Persian version of CISS questionnaire for the elderly patients. For this purpose, investigators will use the Persian version questionnaire in previous study that assessed for young adults, and the investigators will modify it and check the reliability and validity of the final Persian version for subjects with presbyopia. This modified CISS questionnaire will be investigated in the elderly participants and the appropriate cut off point to differentiate between the normal group and the group with convergence insufficiency will be determined.
in the second phase one optometrist (Z.K.R) will do the preliminary examination and another optometrist (S.A) will do the interventions. After the initial examination and having the inclusion criteria, patients will be invited to participate in the study, the nature of the research will be explained to subjects and informed consent will be obtained from them. Before randomization, patients are asked to complete the CISS questionnaire and submit this questionnaire to Optometrist No. 1 (Z.K.R).According to the randomization all patients will be assigned to one of the treatment or control groups by optometrist No. 1. Vision therapy exercises, necessary trainings and prescriptions are given to all patients by Optometrist No. 2 (S.A).For the participants in the control group only near glasses will be prescribed as a conventional treatment, for the second group near glasses with base in prism according to sheard's criterion will be prescribed and in the third group, the prescription of near glasses will be given along with the complete training of the home exercises.
Condition or disease | Intervention/treatment | Phase |
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Convergence Insufficiency | Other: home vision therapy Other: base in prism prescription Other: conventional placebo | Not Applicable |

Study Type : | Interventional (Clinical Trial) |
Estimated Enrollment : | 250 participants |
Allocation: | Randomized |
Intervention Model: | Parallel Assignment |
Masking: | Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor) |
Primary Purpose: | Treatment |
Official Title: | To Compare Home Vision Therapy and Prism Prescription in Presbyopic Persons With Convergence Insufficiency |
Estimated Study Start Date : | April 2022 |
Estimated Primary Completion Date : | March 2023 |
Estimated Study Completion Date : | May 2023 |
Arm | Intervention/treatment |
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Experimental: home vision therapy
near glasses will be prescribed along with a complete training of the exercises and with a eye exercise form of information about how and how long to do the exercise, by optometrist No 2 (Saeid Abdi).training includes: Voluntary convergence, Bug on string, Eccentric Circles, Jumping vergence , Barrel card, chiastopic fusion, Brock string, push-up These exercises will be done 3 days a week for 20 minutes ( 10 minutes at noon and 10 minutes at night ) for 2 month. Home exercises include eight vision therapy exercises and patients will do two exercises each day at noon and two exercises at night.
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Other: home vision therapy
a group of vision therapy procedures in home to improve convergence insufficiency
Other Name: home eye training |
Experimental: base in prism prescription
base in prism prescription using sheards criterion near prismatic glasses will be prescribed and the amount of prism will be divided between two eyes; and random and aimless eye movements, without convergence and accommodation effects will be prescribed by optometrist No. 2 (Saeid Abdi). patients should complete their checking form for eye exercises.
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Other: base in prism prescription
base in prism prescription according to sheards criterion
Other Name: prism prescription |
Placebo Comparator: conventional
new near glasses as a conventional treatment with the practice of random and aimless eye movements, without convergence and accommodation effects will be prescribed by optometrist No. 2 (Saeid Abdi). patients should complete the form of their eye training.
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Other: conventional placebo
using near glasses with aimless eye training
Other Name: placebo |
- treatment success criteria [ Time Frame: 2 month after intervention ]
achieving near point of convergence below 6 cm or 4 cm reduction in its distance, positive fusional vergence according to sheard criterion or grater than 15 prism or 10 prism improvement.
achieving normal limit in CISS or 10 score improvement in total score.

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Ages Eligible for Study: | 40 Years to 60 Years (Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | Yes |
Inclusion Criteria:
CISS score more than the estimated cut off point
Best corrected visual acuity=20/20 for near and far
Having Convergence Insufficiency
Near exophoria should be at least 4 prisms more than distant exophoria
NPC more than 6 cm
Inadequate near-positive positive fusion according to the Convergence Insufficiency Treatment Trial (CITT) study (8)
Normal monocular accomodation amplitude according to Hofster formula
Exclusion Criteria:
Any type of strabismus
Amblyopia
Refractive error more than 6 diopters
Patients with history of prism prescription
History of vision therapy from 5 years ago
History of strabismus surgery or refractive error surgery
History of eye trauma
Use of any ophthalmic or general ophthalmic drugs affect ocular accommodation such as phenylephrine, anticholinergic drugs (mydriatics), carbonic anhydrase inhibitors, antihistamines, morphine and its derivatives, antidepressants amphetamine and imipramine
More than one prism of vertical phoria
Any mechanical limitations in the eye muscles
Ocular muscle paralysis
Nystagmus
Any systemic and neurological diseases affecting binocular vision such as diabetes, myasthenia gravis, Graves', multiple sclerosis
Responsible Party: | Saeid Abdi, Principal Investigator, Shahid Beheshti University of Medical Sciences |
ClinicalTrials.gov Identifier: | NCT05311917 |
Other Study ID Numbers: |
1400.610 |
First Posted: | April 5, 2022 Key Record Dates |
Last Update Posted: | April 22, 2022 |
Last Verified: | April 2022 |
Studies a U.S. FDA-regulated Drug Product: | No |
Studies a U.S. FDA-regulated Device Product: | No |
vision therapy prism prescription convergence insufficiency |
Ocular Motility Disorders Central Nervous System Diseases Nervous System Diseases Cranial Nerve Diseases Eye Diseases |