Transcript Hyperopia
Hyperopia Walter Huang, OD Yuanpei University Department of Optometry Definition The common name for this refractive error is far-sightedness Patients with hyperopia are known as hyperopes Definition When parallel rays of light enter the eye (with accommodation relaxed) and come to a single point focus behind the retina Etiology Axial length The axial length of the eye is shorter than normal due to imperfect emmetropization Etiology Refractive power The refractive power of the eye is too weak Curvature hyperopia Cornea or lens has a flat curvature Decreased index of refraction Due to decreased density in some parts of the optical system of the eye Loss of accommodation Due to age, drug medications Aphakia (no lens) Due to cataract removal Prevalence Hyperopia is more common than myopia Prevalence Age The mean refractive error is +2.00D in newborns The mean refractive error is +1.00 to +0.50D in children at age 6 The mean refractive error is plano in children at age 10 The mean refractive error is skewed toward myopia in children after age 10 Prevalence Gender Hyperopia is more common in females than in males Prevalence Ethnicity Higher prevalence in American Indians, Blacks, Caribbean, South Sea Islanders, and Eskimos Compensating Accommodation Factors Fatigue – general and ocular Due to continuous focusing of images in and out on the retina Illness (e.g., cold, fever) Mental state (e.g., stress) Alcohol Drugs and medications (e.g., antihistamines) Antihistamines may relax accommodation and dilate the pupils Facultative Hyperopia Definition The amount of hyperopia that can be overcome by accommodation Absolute Hyperopia Definition The amount of hyperopia that cannot be overcome by accommodation Manifest Hyperopia Definition The amount of hyperopia revealed with a noncycloplegic refraction (i.e., when no pharmacological drugs are used to dilate the eyes) Latent Hyperopia Definition The amount of hyperopia revealed with cycloplegic refraction (i.e., when pharmacologic drugs are used to dilate the eyes) Latent Hyperopia Causes Drugs and progressive near work, resulting in accommodative spasms so that accommodation may not be relaxed Total Hyperopia Definition The sum of manifest hyperopia and latent hyperopia Absolute Hyperopia and Visual Acuity Uncorrected VA Refractive Error (D) 20/30 0.50 20/40 0.75 20/60 1.00 20/80 1.50 20/120 2.00 20/200 2.50 Symptoms Asthenopia or ocular fatigue Frontal headaches Avoidance of visual tasks, especially at near Blurry vision at distance and near Intermittent blurring of vision Signs Miotic pupil Enables accommodation and increased depth of focus Esophoria Inward deviation of the eyes With accommodation, eyes tend to converge Decreased visual acuities at distance and near, especially the latter Occasional diplopia or double vision Clinical Tests Visual acuity tests – distance and near Binocular vision tests (e.g., cover test) Accommodation tests Retinoscopy Subjective refraction Management Accommodation training (especially in young patients) Convergent or plus lenses in spectacles or contact lenses Refractive surgery Management Spectacles Single vision glasses Management Contact lenses Soft contact lenses Rigid gas permeable contact lenses Management Refractive surgery Photorefractive keratectomy (PRK) Laser in-situ keratomileusis (LASIK)