====== Convergence Insufficiency ======

  * Symptoms of eye strain, double vision with near work, headaches, astenopia worse with prolonged near work 
  * Abnormally far [[convergence|near point of convergence]]
  * Common accompanying signs: 
    * exophoria greater at near than distance
    * decreased or absent [[convergence|fusional convergence]] 
    * normal divergence
    * Low [[accommodative_convergence_to_accommodation_ratio|AC/A]] 
    * accommodative insufficiency 
  * Uncommon accompanying signs:
    * orthophoria
    * esophoria at near

====Near Point of convergence====
  * Point at which a person can no longer hold convergence at near
  * Testing procedure
    * Proper correction should be worn 
    * Use accommodative target (20/40 image or similar) 
    * Patient focuses the target that slowly moves towards the nose
    * Where diplopia occurs is the "break point"
  * **>6 cm** from the nose in non-presbyopes and **>10 cm** for presbyopes is probably abnormal
====Convergence Amplitudes====
  * Testing procedure 
    * Should be wearing proper correction
    * Measure with base out prism on distance (6 m) then near target (1/3 m)
    * Use accommodative target 20/40 or similar
    * Move the prism bar to the point where patient can no longer maintain single vision on the object, this is the **break point**.
    * Before reaching the break point, the patient may note a point where the image blurs, the patient can no longer use fusional convergence and resorts to accommodative convergence which may improve convergence but causes a blurred image due to over-convergence 
    * Reduce the base out prism until the patient recovers single vision, this is the **recovery point**. 
    * if exotropia present ensure not worse XT in downgaze.
    * Encouragement often improves convergence and should be provided to every patient.
    * Testing convergence after testing divergence amplitudes will reduce convergence.

=== Normal Convergence Amplitudes reported by Several Authors ===

^ Prism Diopters  ^ Parks (1976)  ^ Duane (1933)  ^ Fray (2017)  ^ Ferrari (2019)  ^
|  **Near**                                                                    |||||
| Break Point     | 20-25         | 38-51         | 35           | 45              |
| Recovery Point  | 18-22         |               |              | 40              |
|  **Distance**                                                                |||||
| Break Point     | 15            |               | 26           | 25              |
| Recovery Point  | 12            |               |              | 20              |

====Convergence Amplitudes in Convergence Insufficiency====
Most studies would include patients with **≤ 15 PD break point**

====Other Signs of CI====
  * Low [[accommodative_convergence_to_accommodation_ratio|AC/A ratio]] of <2:1
  * Esophoria larger at near than at distance
  * High CI symptom survey score of ≥16

====Convergence Insufficiency Symptom Survey====

  - Do your eyes feel tired when reading or doing close work?
  - Do your eyes feel uncomfortable when reading or doing close work?
  - Do you have headaches when reading or doing close work?
  - Do you feel sleepy when reading or doing close work?
  - Do you lose concentration when reading or doing close work?
  - Do you have trouble remembering what you have read?
  - Do you have double vision when reading or doing close work?
  - Do you see the words move, jump, swim or appear to float on the page when reading or doing close work?
  - Do you feel like you read slowly?
  - Do your eyes ever hurt when reading or doing close work?
  - Do your eyes ever feel sore when reading or doing close work?
  - Do you feel a “pulling” feeling around your eyes when reading or doing close work?
  - Do you notice the words blurring or coming in and out of focus when reading or doing close work?
  - Do you lose your place while reading or doing close work?
  - Do you have to re-read the same line of words when reading?

===Scoring===
  - Collect response to each question from one of the 5 possible responses: 
    - "Never" = 0 points
    - "Infrequently" = 1 point
    - "Sometimes" = 2 points
    - "Fairly Often" = 3 points
    - "Always" = 4 points
  - Tally points from each question- the total will be from 0-60 points

===Analysis of Score===
If score is **≥ 16** CI is likely
  * Convergence Insufficiency mean= 30.8 ± 8.4
  * Normal mean = 8.4 ± 6.4 
  * Cut of value of **16** gives sensitivity of 95.7% and specificity of 87.5%

<WRAP round info 50%>
[[ciss_calculator|Go to the Convergence Insufficiency Symptom Score Calculator]]\\
</WRAP>


====Resources=====
  * [[http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v1/v1c007.html| Marshall Parks. Vergences in Duanes Ophthalmology Chapter 7]]
  * {{::convergence_index_measure_of_converging_power_duane_1914.pdf|Duane, A. The Convergence Index as a Measure of Converging Power. Trans Am Ophthalmology Soc. 1914;13(Pt3):851-8}}
  * {{::study_of_normative_values_of_the_fusional_amplitudes_of_ocular_convergence_and_divergence_2019.pdf |Study of normative values of the fusional amplitudes of ocular convergence and divergence. Ferrari et al. eOftalmo 2019;5(4):167-72}}
  * {{::fusional_amplitudes-developing_testing_standards_fray_2017.pdf |Fusional Amplitudes: Developing Testing Standards. Fray K. Strabismus 2017;25(3):145-155}}

{{tag>convergence}}