Introduction, Assessment and Management of Amblyopia

Editor's Notes

• #3: Introduction What is amblyopia? neurophysiology of amblyopia types causes Classification sign and symptoms Assessment VA testing Contrast sensitivity test ND filter test Stereoacuity test Eccentric fixation Management Passive therapy Active therapy
• #4: The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.
• #5: Amblyopia: The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye. Amblyopia is the most common cause of decreased vision in children.
• #7: in normal vision, an image is seen by both eyes and blended into one picture by the brain When one eye is weaker, the brain ignores the image sent by the weaker eye amblyopia or loss of vision results.
• #8: Amblyopia can be caused by anything that interferes with vision for a significant amount of time during the critical period from birth to about 6 years of age.
• #9: poor aim- most common poor focus- most difficult to detect poor clarity- most severe
• #10: most difficult to detect each eye have unequal refractive error Both eye cannot be in focus at the same time Blurred image in one eye is ignored by the brain
• #12: Meridional amblyopia is a mild condition in which lines are seen less clearly at some orientations than others after full refractive correction. An individual who had an astigmatism at a young age that was not corrected by glasses will later have astigmatism that cannot be optically corrected after 2 y/o.
• #14: most common Both eyes not aimed in exactly same direction Brain turns off misaligned eye to avoid double vision
• #15: Age onset of a strabismus: Critical period- developing amblyopia(birth-3y/o)(5-7y/o) -deep constant suppression After critical period/ adulthood- not lead to amblyopia - constant diplopia because suppression of the eye is difficult and the both eyes retain good VA
• #16: most severe disuse/ understimulation of the retina Due to eye disorder- e.g cataract,corneal opacties,ptosis, eyelid tumors,etc. visual not develop well - brain
• #17: Drugs: - chloramphenicol- use in certain infection can cause toxic antibiotics digoxin-Antiarrhythmic Agent  ethambutol-Antitubercular Agent Tobacco amblyopia – a condition in which the vision is lost because of the use of tobacco. The toxic effects of tobacco constrict the vessels of the body and interfere with circulation. The optic nerve is very sensitive to tobacco and can be easily irritated by excessive smoke. As a result, the optic nerve swells, a condition known as optic neuritis. Alcohol- disorder involves lost vision, including scotomas (blind spots) and decreased visual acuity within the central portion of the visual field Chemicals- Lead, methanol can cause optic nerve damage Nutritional disorders- Strachan's syndrome Figure 2 The optic nerve head in patients with ischemic optic neuropathies
• #18: Refractive, anisometropic- affected same proportionally the centrally and peripherally. Strabismus – affected foveal area. Meridonial – affected the area along the blurred astigmatic meridian. Visual and toxic- may affected part or entire visual field.
• #19: Amblyopia is primarily a defect of central vision. There is a critical period for sensitivity in developing amblyopia. The time necessary for amblyopia to occur during critical period is shorter for stimulus deprivation than for strabismus or anisometropia.
• #21: Visual deprivation amblyopia It is usually caused by congenital or early acquired media opacity. This form of amblyopia is the least common but most damaging and difficult to treat. In bilateral cases acuity can be 20/200 or worse. Toxic amblyopia Endogenous/ Exogenous poisoning. Most severe
• #22: Characteristics of Amblyopia General characteristics of amblyopia are: 1. Abnormal position of pupil2. Blinking or rubbing eyes frequently 3. Narrowing his/ her eyes or slanting when looking at objects4. Looking at objects in a very close distance 5. Leaning forward or aside when looking at object in distance 6. Having problems when reading, such as skipping words 7. Always making mistake when writing or copying 8. Excessive tearing and sensitive to light 9. Red eyes, swollen eyelid and secretion in eyes 10. Motion sickness when travelling long journey
• #37: The contrast sensitivity function provides a more thorough representation of the visual system. For example, the pivotal visual developmental study of Harwerth et al. (17) characterized the changes in the contrast sensitivity function after different periods of monocular deprivation in monkeys. The loss of sensitivity in the mid to high spatial frequencies was profound during abnormal visual development, with increased deprivation leading to further contrast losses. Not only will certain disease/disorders of the eye reduce visual acuity, contrast sensitivity will also be affected (18). For example, patients with multiple sclerosis will have mid to low contrast sensitivity losses (Fig. 25B), whereas patients with cataracts will have an overall reduction in contrast sensitivity (Fig. 25C). Mild refractive error or mild amblyopia will lead to a CSF similar to D in Fig. 25, with more severe refractive errors or severe amblyopia, resulting in a CSF similar to curve C.
• #46: 1. Passive therapy: The patient experiences a change in visual stimulation without any conscious effort Optical correction Occlusion Penalization 2. Active therapy: is designed to improve visual performance by the patient ‘s conscious involvement in a sequence of a specific, controlled visual task that provide feedback CAM visual stimulator Intermittent photic stimulation Pleoptic *Passive therapy (spectacles, occlusion, pharmacological agents). The patient experiences a change in visual stimulation without any conscious effort *Active therapy is designed to improve visual performance by the patient ‘s conscious involvement in a sequence of a specific, controlled visual task that provide feedback
• #47: Useful to give the patient a short period of time (6-8weeks) with proper optical correction alone before the initiation of other amblyopia theapy
• #48: This animation shows the wiring involved with amblyopia, and why we patch eyes to correct vision.
• #50: 1. Total patching excluding all light and form Adhesive patch Spectacle occlude Opaque contact lens 2. Total patching excluding form only allowing the passage of some light. Semi opaque occlusion material such Blenderm tape or frosted glass, is effectively total occlusion.
• #53: under 5 year old age Full time direct occlusion may risk reverse amblyopia Need to establish alternate occlusion (direct and inverse) Ie: for 3 years old children, may need 3 days direct and 1 day indirect occlusion consider 1 cycle and repeated period of time
• #61: described as the "heightened response" to a visual stimulus when an active exposure to light of one second was alternated with a dark period of thirty seconds provide alternate stimulation of the amblyopic eye with equal dark and light intervals, the frequency of four light flashes persecond (4Hz) being chosen after much clinical experimentation. The targets consisted of slides containing much detail of varying type and angular dimension, and were viewed against a red flickering background. provide alternate stimulation of the amblyopic eye with equal dark and light intervals
• #63: The underlying purposes : eccentric fixation must be disrupted first and then the fovea retrained to resume normal fixation Apparatus based on ophthalmoscope principle Euthyscope, projectoscope, pleutophore Used to exposed peripheral retina to a very bright light while protecting the macular area This resulted in after images, which, if negative, had a clear area corresponding to the macula, which the patient was then trained to localized correctly. Pleoptic treatment was only suitable for older children or adults