Convergence Tests

• Convergence is the ability of two eyes to move inwards to focus properly at an object placed near the eye, mainly between the eye and a distance up to one meter. 

• Good convergence is necessary for comfortable viewing and working at near distance; convergence insufficiency is not a rare condition and is met with frequently in people having eyestrain.

• Convergence is divided into two objective and subjective convergence. Both objective and subjective convergence can be done on Livingston Binocular Gauge.

Objective Convergence

• To the binocular gauge, there is an attachment, a small stick with a pointer.

•  The stick is painted alternately black and white.  The stick is placed in the slit of the scale with the pointer running over the centimeter marks. 

• The instrument is placed over the infra orbital margin and the candidate is asked to keep looking at the black and white stick. 

• The stick is then moved towards his nose and the examiner watches the ocular movements of the candidate.  T

• he point where one of the two eye stops moving inwards or suddenly shoots out is taken as the point of convergence. 

• The pointer reading on the scale is noted and is expressed as - convergence 7 cm. 

• If the reading is very high e.g. beyond 11 to 12 cm, the test should be repeated after explaining to the individual what is required of him.

• The test can also be done by the help of a pencil and scale.  The scale is placed below the nose of the candidate and the pencil tip is brought at the level of bridge of the nose. The pencil is then moved towards the nose in contact with marking on the scale and the result noted as explained earlier.

Subjective Convergence

• This can be done with the help of Livingston Binocular Gauge only. 

• The gauge has a box like attachment with the front portion having a cut in the form of a cross.  The back wall has an ivory card with a black vertical line and the letters ‘ALT’ written on either side of it. 

• The card is so placed that the line lies in the middle of the vertical arm of the cross and is seen in the center of the vertical cut when viewed binocularly. 

• The candidate is instructed to look at the line and inform the examiner when the line shifts either to right or left. 

• The box from the far and is then gradually moved towards the candidate’s eye and he informs the examiner as soon as the deflection takes place. 

• The reading is read off from the scale and is noted as SC 18 cm (Right).  This Right or left denotes the dominant eye for the near. 

• The test becomes unreliable in case of presbyopia.

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