Horizontal Deviations

A large proportion of Esophoric conditions have problems with accommodation as their root cause. Due to the synergistic link between accommodation and convergence excessive accommodation produces excessive convergence and thus esophoria uncorrected hypermetropia  esophoria However, a small proportion of esophoric conditions may be classed non-accommodative; i.e. faulty accommodative-convergence plays no part in the condition.

Divergence Weakness decompensated esophoria for distance vision. for near vision the phoria will be approximately 6  more exophoric and likely to be compensated, particularly in older, presbyopic patients. Cover test: DISTANCE 12  SOP NEAR 5  SOP

Aetiology I) Uncorrected hypermetropia is the most common cause of esophoria in distance vision and in this accommodative esophoria spectacle correction usually helps reduce the magnitude of the phoria. II) Muscle tonus in the adductors may be a factor in esophoria in young Pxs. III) Anatomical factors such as abnormal orbital structure, lengths of check ligaments, muscle insertion etc. IV) General Factors a) endocrine over-activity b) diseases of the central nervous system c) anoxemia – lack of oxygen

Investigation I) Symptoms are usually associated with distance vision unless there is accompanying high hypermetropia which will accentuate symptoms for close work. The symptoms described are usually those associated with prolonged use of the eyes, e.g. frontal headaches, blurred near vision and will be less or absent in the mornings, unless there is an underlying pathological cause. II) Refraction is very important in divergence weakness type of esophoria because of the associated with uncorrected hypermetropia. III) Measurement of the phoria and test for decompensation will be the most useful part of the investigation.

Management I) REMOVAL OF THE CAUSE OF DECOMPENSATION consider what improvements could be made to the Px’s working conditions. II) REFRACTIVE CORRECTION uncorrected hypermetropia is a common cause full correction is usually given and this may mean that a cycloplegic refraction is required in the case of children. The Px should be asked to wear the correction for about 1 month whereupon tests for decompensation should be carried out again if symptoms persist.

III) ORTHOPTIC TREATMENT if symptoms persist then orthoptic exercises should be considered. physiological diplopia (phys dip) exercises increase the negative fusional reserves and/or positive relative accommodation for distance vision. IV) RELIEVING PRISMS this is rarely necessary in esophoria may be considered as a last resort after orthoptic exercises have been unsuccessful. A test for decompensation (e.g. Fixation Disparity) is used to find the prism power that will allow the phoria to be just compensated. V) REFERRAL - this should be considered if a pathological cause is suspected. Management

Convergence Excess characterised by an increase in the degree of esophoria for near vision which is decompensated. usually a small degree of compensated phoria for distance for near vision. Cover test: DISTANCE 3  SOP NEAR 10  SOP

I) Excessive accommodation is usually the main factor: uncorrected hypermetropia spasm of accommodation pseudo-myopia prolonged work at a very close distance. II) High AC/A is often a factor. This is normally about 4  /1D but when it is high accommodation for near vision will result in excessive convergence. Convergence excess can rarely occur with a normal or low AC/A ratio. Aetiology

III) Convergence excess can also occur as part of a hysterical reaction. IV) Incipient presbyopia can occasionally result in convergence excess due to the high ciliary muscle effort needed to produce adequate accommodation. Aetiology (cont’d)

Investigation I) Symptoms will usually be associated with prolonged use of the eyes in near vision. Frontal headache ocular fatigue blurred near vision II) Gradient Test Measurement of the AC/A ratio may be performed. This can be done with the Maddox Wing.

III) Cycloplegic refraction is required in convergence excess Pxs to explore the possibility of latent hypermetropia, spasm of accommodation or pseudo-myopia. IV) Measurement of the phoria and test for decompensation will reveal high esophoria for near vision. Investigation (cont’d)

Management I) REMOVAL OF THE CAUSE OF DECOMPENSATION II) REFRACTIVE CORRECTION full refractive error found by cycloplegic refraction (less tonus correction if appropriate). With this correction in place the Px’s distance vision may be blurred initially but it should clear as the Px’s latent error becomes manifest.

II) REFRACTIVE CORRECTION Bifocals are sometimes prescribed for young Pxs with convergence excess Sometimes convergence excess breaks down into a convergent strabismus (esotropia) for near vision. In these cases bifocals may be appropriate if binocular vision is restored when the Px looks through the segment. Bifocals are not considered suitable in Pxs with a low AC/A ratio. Management (cont’d)

III) ORTHOPTIC TREATMENT Exercises that develop the positive relative accommodation These exercises encourage accommodation without convergence The divergent amplitude of the prism vergence can be developed. Here the accommodation is encouraged to remain unchanged whilst the eyes diverge Management (cont’d)

IV) RELIEVING PRISMS – not appropriate for convergence excess type. V) REFERRAL - this should be considered if a pathological cause is suspected. Management (cont’d)

Basic or Mixed decompensated esophoria of the same magnitude in both distance and near vision Cover test: DISTANCE 13  SOP NEAR 12  SOP

Exophoria is a more passive condition that esophoria. The anatomical position of rest of the eyes is divergent When accommodation and accommodative convergence is relaxed the eyes tend to diverge.

Anatomical Rest Fusion Free Position Fusion of Distant Object Near Fusion Free Fusion of Near Object Tonus Proximal + Accommodative

1) Convergence Weakness decompensated exophoria of approximately the same degree for distance and near vision. Cover Test Dist 13  Near 12 

2) Divergence Excess typical form is an intermittent divergent strabismus (exotropia) for distance vision and compensated exophoria for near. It was originally defined as an exo-deviation of 15  greater for distance vision than for near.

3) Convergence Insufficiency The Px has an inability to obtain or maintain sufficient convergence for comfortable near vision. May be present without decompensated heterophoria for distance or near vision. An anomaly of convergence rather than a true heterophoria and will be dealt with in subsequent lectures.

1) Convergence Weakness Exophoria.

Aetiology I) Anatomical factors seem to play a part in most exophoria as the position of anatomical rest is divergent. II) Hypertonicity of the abductors may be a contributory factor. III) Myopia when uncorrected may build up a false accommodation convergence relationship for near vision.

IV) Presbyopia is usually accompanied by exophoria as accommodation is reduced when a reading addition is employed. V) Absolute hypermetropia may also be a factor in the generation of exophoria. Hyperopic Pxs reach an age when they are no longer able to compensate for their refractive error by accommodating. They allow their accommodation and convergence to flag, resulting in decompensated exophoria. VI) Suppression of one eye due to long periods of using monocular vision can also be a factor. Aetiology (cont’d)

Investigation I) Symptoms are not usually as marked as those in esophoria and suppression of one eye may alleviate the symptoms. Symptoms may include frontal headaches, ocular fatigue and intermittent diplopia. II) Measurement of the phoria and tests for decompensation will be the most useful part of the investigation

Management I) REMOVAL OF THE CAUSE OF DECOMPENSATION II) REFRACTIVE CORRECTION – myopia or absolute hypermetropia. In other hyperopic cases a partial correction may be necessary In presbyopia the reading addition should be kept to a minimum.

III) ORTHOPTIC TREATMENT this may be appropriate in younger Pxs, the treatment should aim to: a) treat any suppression b) develop positive fusional reserves and/or negative relative accommodation. c) develop a correct appreciation of physiological diplopia. Management (cont’d)

IV) RELIEVING PRISMS where orthoptic treatment is inappropriate or unsuccessful, prism relief may prove to be a simple and effective means of management. V) REFERRAL this should be considered if all other treatments fail or if a pathological cause is suspected. Management (cont’d)

2) Divergence Excess Exophoria.

Aetiology The causes of divergence excess remain uncertain  tonic/ anatomical factors. Divergence excess exophoria shows a greater deviation for distance vision than for near and it may even break down to an intermittent squint for distance.

Investigation I) Symptoms are usually absent divergence of one eye is noticed by others may become apparent with inattention or stress. some Pxs learn to control the deviation be exercising accommodation and will report blurred vision.

II) Cover test may show a decompensated exophoria for distance vision but some Pxs can make this appear compensated by active attention. Repetition of the cover test usually increases the deviation for distance vision and the exophoria may become an exotropia. The Maddox rod and compensation tests may similarly show variation for distance vision. Investigation

III) Refractive error is usually low. IV) Negative fusional reserves are abnormally high. Instead of the average 5-9  (base-in) they may exceed 20  . The very divergent position produced by measuring the negative fusional reserves in divergence excess is usually accompanied by suppression. Investigation

Management I) REMOVAL OF THE CAUSE OF DECOMPENSATION not usually possible other than by the means outlined below. II) REFRACTIVE CORRECTION myopes should be given the full correction. low degree of hyperopia a correction is not given unless required to improve and equalise the acuity.

III) ORTHOPTIC TREATMENT a) treat any suppression b) develop positive fusional reserves and/or negative relative accommodation. c) develop a correct appreciation of physiological diplopia. IV) RELIEVING PRISMS – are seldom satisfactory in divergence excess as they disturb near vision. V) REFERRAL Management

Horizontal Deviations

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Horizontal Deviations