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Home Vision Therapy and Prism Prescription in Presbyopic Persons With Convergence Insufficiency

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. Identifier: NCT05311917
Recruitment Status : Not yet recruiting
First Posted : April 5, 2022
Last Update Posted : April 22, 2022
Information provided by (Responsible Party):
Saeid Abdi, Shahid Beheshti University of Medical Sciences

Brief Summary:

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
Convergence Insufficiency Other: home vision therapy Other: base in prism prescription Other: conventional placebo Not Applicable

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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
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.
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.
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.
Other: conventional placebo
using near glasses with aimless eye training
Other Name: placebo

Primary Outcome Measures :
  1. 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


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


Any systemic and neurological diseases affecting binocular vision such as diabetes, myasthenia gravis, Graves', multiple sclerosis

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Responsible Party: Saeid Abdi, Principal Investigator, Shahid Beheshti University of Medical Sciences 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

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by Saeid Abdi, Shahid Beheshti University of Medical Sciences:
vision therapy
prism prescription
convergence insufficiency
Additional relevant MeSH terms:
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Ocular Motility Disorders
Central Nervous System Diseases
Nervous System Diseases
Cranial Nerve Diseases
Eye Diseases