O3A 2 Deviations

when two eyes do not point at the same object of regard- image doesnt fall on both fovea

• It is there all the time
• TROPIA
• heterotropia, strabismus, squint

• only there when you cover the eye
• brought about by eliminating all stimuli to fusion

retinal disparity

blur

• anatomical position of rest
• eyes tend to diverge after death
• whilst alive tend to turn inwards- due to surrounding tissue and tone of muscle
• physical position of rest

convergence compensating for any excess or deficit in tonic convergence stimulated by retinal disparity

voluntary convergence- due to knowlede that the object is nearby

accommodation

position the axes take when stimuli to fusion is absent

fusional divergence has to bring it back to ortho= amount of phoria

fusional convergence has to make up for it

phoria depends on the amount of convergence that accompanies each dioptre of accommodation

does not cause symptoms

thought to generate suppression

• tonic position gives deviation
• muscle weak/inserted incorrectly- rare

interaction between vergence and accommodation is abnormal

uncorrected hyp- overconverge

• aesthnopia
• HA
• transient blur/diplopia
• avoidance of near work
• loss of place while reading
• words running together while reading

• specs
• vision training

• possible muscle weakness
• same as phoria

• diplopia: superimposition causing confusion
• suppression: adult-> diplopia, in macular to avoid confusion
• ambyopia: strab- occur in deviating eye as a result of continued suppression
• rx- uncorrected aniso or astig
• anomalous correspondence- one fovea of the eye doesnt correspond with the other
• can fix diplopia and confusion

specs, occlusion, vision training, surgery, botox

A regularly repetitive, rapid involuntary movement of the eye

unequal image size and shapes

angle of tropia is same in all directions of gaze

angle differs in different directions of gaze