7573088
Description
Flashcards by Andrew Street, updated more than 1 year ago
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Created by Andrew Street
about 8 years ago
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| Question | Answer |
| What is a squint & what are the causes? | Squints are common in childhood. They occur with misalignment of the visual axes of the eyes so that they appear to point in different directions. If a squint develops in first 7yrs, it can have a significant impact on visual development. The causes of squint may be: * Idiopathic * Refractive error * Visual loss * Ophthalmoplegia (central or peripheral) OHOP |
| What are the two main types of squint? | Concomitant (non-paralytic) squint: * Common & usually due to a refractive error in one or both eyes * Often convergent Non-concomitant (paralytic) squint: * Rare & usually due to cranial (motor) nerve palsy * Must exclude an intracranial lesion (eg brain tumour) OHOP |
| Define convergent, divergent, & latent squints. | * Convergent - bad eye turned inwards (cross-eyed appearance) * Divergent - bad eye turned outwards * Latent - a squint that is controlled by subconscious effort & is not always apparent. In certain situations, such as fatigue, control is lost & the squint will become ‘manifest’. OHOP |
| What tests can be used to detect a squint? | * Corneal light reflex test - use a pen-torch held at a distance to produce reflections on both corneas simultaneously. The light reflection should appear in the same position in the two pupils. If it does not, a squint is present. Minor squint may be difficult to detect. * Cover test - when the fixing eye is covered, the squinting eye moves to take up fixation. The test should be performed with the object near (33 cm) & distant (at least 6 m), certain squints are present only at one distance. OHOP |
| Corneal light reflex (reflection) test to detect a squint. The reflection is in a different position in the two eyes because of a small convergent squint of the R eye. ITOP p61. | |
| The cover test is used to identify a squint. If the fixing eye is covered, the squinting eye moves to take up fixation. This diagram shows a L convergent squint. ITOP p61. | |
| Mx of squints. | The aim of Rx is to get the ‘weaker’ squinting eye ‘trained up’ in order to prevent amblyopia. Rx's are usually under supervision of orthoptists in co-operation with ophthalmic surgeons. * Correct refractive error - wear glasses * Eye patch wearing on the good eye to ‘train’ weaker eye * Eye muscle exercises * Eye (muscle) surgery if large squint and above measures failing OHOP |
| What is amblyopia & what causes it? | Potentially permanent loss of visual acuity in an eye that has not received a clear image. Affects 2–3% of children. Usually affects one eye. Any interference with visual development may cause amblyopia: * Refractive errors * Squint * Visual deprivation eg ptosis or cataract ITOP p62. |
| Rx of amblyopia. | Early Rx is essential as after 7 YO improvement is unlikely. * Correct refractive error with glasses * Eye patching - attempt to reverse amblyopia, by covering the better eye to force the ‘lazy eye’ to work * Eye (muscle) SX OHOP |
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