REFRACTION Dr. Puneet Kumar Srivastava

Refraction Def: Method of evaluating the optical state of eye. Or The process by which the patient is guided through the use of a variety of lenses so as to achieve the best possible acuity on distance and near vision test. Acc. To the physicist, Refraction is defined as bending of light rays when it passes from one media to other having diff refractive indices.

Refraction happens because the light slows down in the material (the part of the beam that arrives first slows down first)

Types Of Lenses 1.Sphere lens: Same curvature over its entire surface and thus the same refractive power in all meridians. Convex Sphere Lens: Converge light rays, “+”plus lens. Concave Sphere Lens: Diverge light rays, ”-”minus lens. 2. Cylinder lens 3.Spherico-cylinder lens 4.Prism

Lenses

Refractive State of eye Emmetropia: Parallel light rays are focused sharply on retina. Ammetropia: Unable to bring parallel light rays into focus. Types: 1.Myopia 2.Hypermetropia 3.Astigmatism

Emmetropia o It’s a optically normal eye. o In emmetropic eye, parallel light rays are focused sharply on sensitive layer of retina with the accommodation at rest.

Myopia o Short sightedness, excessive convergent power o Parallel rays of light coming from infinity are focused in front of retina when accommodation is at rest.

NormalMyopia

Hypermetropia o Long sightedness, Insufficient convergent power. o Parallel rays of light coming from infinity are focused behind the retina with accommodation being at rest. o The posterior focal point is behind the retina, which therefore receives a blurred image.

Astigmatism The rays of light entering the eye cannot converge to a point focus but form focal lines.

Strum’s Conoid

Presbyopia Progressive loss of accommodative ability of the crystalline lens caused by natural process of ageing.

Presbyopia

Visual Aids for Impairments Optical Aids Hand Magnifier Stand magnifier Bifocals High Power Spectacles Focusable telescope Closed-circuit Camera Non optical Aids Lighting Color clues Consistent storage plan Portable Lamp High Contrast Print Large Print Cane Touch tone buttons

Low Vision & Blindness BCVA = 20/70 to 20/200 Blindness = 20/400 to No Light Perception Absolute blindness = No Light Percertion Legal Blind = BCVA < 20/200 in better eye; widest visual field diameter = 20` Travel Vision = Patient negotiate their environment without auxiliary aids. Common Causes = Adults(Diab. Retino./Macular Degen. /Gaucoma)

Assessment & Diagnostic Tests Patient’s interview Chief Complaints History: past/ medical/ surical Contrast sensitivity testing Glare testing

Nursing Management Adaptation required for patient: Emotional Physical Social

Promoting Coping Efforts Grieving: Denial & Shock Anger & Protest Restitution Loss Resolution Acceptance Additional: Independence- Dependence conflict Coping with Stigma Social without visual cues & landmarks

Promoting Spatial Orientation &Mobility Collaborative effort between patient & responsible adult who serve as the sighted guide.  Remembering room layouts  Emotional support  Assess the degree of physical assistance

Promoting Home & Community-Based Care Collaborative effort of Nurse Social worker Family others

Thank You..