Investigating Esotropia Flashcards

Question

What is Monocular Occlusion used for?

Answer 1

To differentiate true & simulated convergence excess esotropia. Those with true convergence excess exhibit a manifest convergent strabismus when viewing a close object and a small, well-controlled latent strabismus upon fixation of a distant object. Those with simulated convergence excess have a comparable near deviation to those with true convergence excess but can be shown to have a distance deviation that approaches the size of the near strabismus once the normal fusional mechanisms are disrupted by a period of prism adaptation.

Answer 2

- Patient wears occlusion for 30 - 60 minutes - Alternate PCT measurements are retaken without allowing the patient to regain fusion - Assess for increase in distance angle which may match the near angle Cover one eye and see if the angle changes when able to fuse or not (when uncovering the eye). Tells us max angle of deviation, will tell us if there is a hidden deviation angle where the patient is controlling it by fusing so would want surgery on this higher amount compared to their PCT normal response. E.g. Nr 40 and Dist 20. Do this Monocular Occlusion to see if the Dist angle increases (if it does this is a simulated ET)

Answer 3

True Convergence Excess - No significant increase in distance deviation following monocular occlusion or prism adaptation Simulated Convergence Excess - Significant increase in distance deviation following monocular occlusion or prism adaptation

Answer 4

- Visual acuities – is there any explained visual loss - Previous history of esophoria or microtropia (i.e. broken down/decompensation into a ET) - Refraction – underlying myopia or hypermetropia? - OM – for lateral rectus function - Lids - Pupils - Concomitant esotropia can occur following occlusion or visual loss, due to a decompensation of an esophoria or microtropia, for an unknown reason, or due to myopia Occurs between the ages of 2 - 5yo

Answer 5

Fixation-preference testing has been useful in detecting amblyopia in children unable to give reliable visual acuities, except for children with small-angle tropias and those without manifest deviations. This test is performed by placing a vertically oriented 10 PD prism over one eye, either base down or base up (more commonly base down). The vertical prism induces a hypertropia, allowing evaluation of fixation preference. Strong fixation preference for one eye is indicative of amblyopia. Amblyopia can be bilateral in children with bilateral blurred retinal images (e.g., bilateral congenital cataracts, or bilateral high hypermetropia >+5.00 sphere) The fixation preference test is based on the assumption that nonamblyopic strabismic patients will alternate fixation or hold fixation well with either eye during binocular viewing. Conversely, amblyopic patients will show strong fixation preference with the sound eye and will not hold fixation with the amblyopic eye.

Answer 6

Same prescription in both eyes Without glasses Mod RET With glasses controlled to E at Nr and NAD at Dist PCT said without glasses is same at Nr and Dist at 35PD BO but with glasses down to 6PD 4yo = no surgeryIntermittent fully accom ET as completely controlled with glasses. Require prescription full-time due to size of deviation. = Fully accommodative esotropia. You would want to carry out a full investigation of BSV, including sensory, motor and stereopsis. You would want to check that this patient was not corrected to a microtropia. You would also want to know their visual acuities

Answer 7

Slightly reduced VA in LE so potentially amblyopic Without glasses marked LET at Nr and moderate LET at Dist PCT without glasses 50PD BO at Nr & 35PD BO at Dist = Constant ET potentially but need to prescribe glasses to ensure no accommodative element. Provide cycloplegic refraction and reassess the patient with prescription if needed. Could be early-onset due to 6mo. Unlikely to be infantile ET due to alternation not changing.

Answer 8

Still in critical period Same prescription in both eyes CT without glasses is a moderate RET at Nr and Dist CT with glasses Mod RET at Nr but controlled to E at Dist = Convergence Excess PCT without glasses Nr and Dist is 35PD BO With glasses at nr 20PD (so sort controlled but not fully) and controlled to 6PD at dist = Convergence excess ETYou would want to perform an appropriate VA test for the patient e.g. letter test (may need matching card). You would want to discuss full investigation of BSV, PAT and AC/A ratio to confirm your diagnosis of Convergence exceess esotropia.

Answer 9

10 years old so outside of the critical period Low prescription that’s not in use currently VA not significantly different in each eye CT without glasses showed a marked RET for Nr and Dist at 55PD BO AC/A is normal range so not likely a convergence excess ET or partially accom constant ET Right suppression response is interesting as vision not significantly different in each eye. = Constant ET without accommodative element

Answer 10

PODT cgls (fixing a target) 1/3m no complain of diplopia up to 20 dioptres over- and under-correction 6m no complain of diplopia from 20 dioptres under-correction to 10 dioptres over-correction, complain of diplopia from 10 to 20 dioptres over-correction