13988245
| Question | Answer |
| Refraction | Procedure: For both Distance and Near, Monocular and Binocular Normal: 18-24 - 6/4.5, >75 - 6/6+1 * have to be able to identify cause before Px leaves - congenital, refractive error, trauma, previous infections, existing pathology |
| Binocular vision - cover test | An objective method of assessing heterophoria |
| Near point of convergence (NPC) | Relative position of visual axes when they intersect at a near point of regard - ability of the eye to converge - response to muscle tonus, proximity of near and in synkinesis with accommodation Instructions: ' A measure of how well you can bring your eyes inwards when you are reading' Condition: Normal room lights Rx: required Target: one letter above best corrected vision - clear and single Result: where there is sustained double vision (measure distance where this occurs and when single vision is recovered) Recording: B/R - normal: 6/8cm with habitual Rx Symptoms - double vision at near |
| Near point of accommodation | Ciliary muscle constricts to make zonules of Zinn relaxed, thus crystalline lens curvature is altered to become more convex = accommodation - Decreases with increase age --> presbyopia - uncorrected myope will give falsely high reading and hypermetrope will give low one Symptoms: blurred vision at near Instructions: measuring focusing power of the eye Condition: normal room lighting Rx: required Target: one above their best corrected Procedure: do monocular only, bring letter closer until reached sustained blur Recording: cover distance into dioptres R 15D, L 15D Normal: 15-(1/4 age) |
| Binocular vision - Stereopsis | Test for quality of binocular vision 3 anatomical and physiological requirements: - large binocular over-lap in visual field - partial decussation of afferent visual fibres - coordinated conjugate eye movements Early impairment - lead to poor stereopsis - </= 40 min arc: any ocular misalignment cannot be larger than Panum's fusional area - 60 mins arc: still within normal limits - >60 min arc: accurate bifoveal fixation present Instructions: measure of how well your eyes can see depth perception Condition: normal lighting + Px wears 3D glasses Rx: required Working distance: 40cm Check for: - suppression (L/R) - Global (random dot) - Local (contour) Recording: Test name, type of stereopsis/suppression and min arc obtained with Rx |
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