Hyperopia (quiz before exam)

• Hypermetropia


  Refractive state of eye where parallel rays of light coming from infinity are focused behind the sentient layer of retina with accommodation being at rest

  
• Hyperopia


  Also called longsightedness
• Hypermetropia first suggested by KASTNER

  1755
• Hypermetropia


  • Posterior focal point is behind the retina which receives a blurred image

  
• etiology

  • Axial
  • Curvature
  • Index
  • Positional
  • Absence of lens

  
• Axial hypermetropia


  Most common, total refractive power of eye is normal but axial shortening of eyeball

  
• Curvature hypermetropia


  Flattening of cornea, lens or both
• Index hypermetropia


  Change in refractive index with age, physiologically in old age or pathologically in diabetics under treatment
• Positional hypermetropia


  Posteriorly placed crystalline lens, occurs as congenital anomaly or result of trauma/disease

  
• Clinical types of hypermetropia


  • Simple hyperopia
  • Pathological
  • Functional
• Simple hyperopia

  Most common, results from normal biological variations in the development of eyeball

  
• Pathological hypermetropia


  Anomalies lie outside the limits of biological variation, includes acquired hypermetropia and positional hypermetropia
• Functional hypermetropia


  Results from paralysis of accommodation, seen in patients with 3rd nerve paralysis & internal ophthalmoplegia
• Optical condition in hypermetropia

  Parallel rays focus behind retina, diffusion circles produce blurred & indistinct images, retina is nearer to nodal point, image is smaller than in emmetropic, rays diverge from retina, formation of clear image is possible only when converging power of eye is increased

  
• Total hypermetropia


  Total amount of refractive error, estimated after complete cycloplegia with atropine, divided into latent & manifest

  
• Latent hypermetropia

  Corrected by inherent tone of ciliary muscle, usually about 1D, high in children, decreases with age, revealed after abolishing tone of ciliary muscle with atropine
• Manifest hypermetropia


  Remaining part of total hypermetropia, corrected by accommodation and convex lens, consists of facultative & absolute

  
• Facultative hypermetropia


  Corrected by patients accommodative effort
• Absolute hypermetropia


  Residual part, not corrected by patients accommodative effort

  
• At birth +2+3D hypermetropia, slightly increase in one year of life, gradually diminished until by the age 5-10 years, in old age after 40 year again tendency to hypermetropia
• Symptoms of hypermetropia

  Blurring of vision for close work, asthenopia (tiredness, frontal or fronto temporal headache, watering of the eyes, mild photophobia), defective vision with asthenopia, defective vision only

  
• Small error produces no symptoms, corrected by accommodation of patient
• Asthenopia increases as day progresses and after prolonged near work
• Defective vision with asthenopia when refractive error more than 4D, not corrected by accommodation</b>

  
• Defective vision only when refractive error more than 4D, adults usually do not accommodate

  
• Signs of hypermetropia


  • Defective visual acuity, small or normal sized eyeball, smaller than normal cornea (cornea plana), shallow anterior chamber, dislocated lens backwards, short axial length on A-scan ultrasonography

  
• Complications of hypermetropia

  • Recurrent styes, blepharitis or chalazia, accommodative convergent squint, amblyopia, predisposed to develop primary narrow angle glaucomas
• Basis for treatment


  No treatment if error is small, asymptomatic, visual acuity normal, no muscular imbalance
• Treatment in young children

  Some degree of hypermetropia is physiological so no correction, treatment required if error is high or strabismus is present, small error may require correction when working in school, error tends normally to diminish with growth so refraction should be carried out every six months and correction reduced if necessary
• Treatment in adults

  Correct as much of the total hypermetropia as possible to relieve the accommodation, undercorrect in case of spasm of accommodation or exophoria hyperopia, patients with absolute hypermetropia more likely to accept nearly the full correction, in pathological hypermetropia the underlying cause rather than the hypermetropia is chief concern
• Optical treatment


  • Spectacles
  • Contact lens
  • Refractive surgery (hexagonal keratotomy, laser thermal keratoplasty, photorefractive keratectomy, laser assisted in situ keratomileusis, phakic IOL and clear lens extraction)
• Refractive surgery not as effective as in myopia
• Appropriate optical correction almost always leads to clear and comfortable single binocular vision

  
• Younger children with significant hyperopia associated with amblyopia, strabismus, or anisometropia require treatment, starting as early as 3-6 months of age
• Hyperopia is a common refractive disorder that has been overshadowed by myopia in public perception, vision research & the scientific literature
• Uncorrected hyperopia has a greater adverse effect on visual acuity than uncorrected myopia, and the close association between hyperopia, amblyopia & strabismus, especially in children, makes hyperopia a greater risk factor for more permanent vision loss than myopia

  
• Early diagnosis & treatment of significant hyperopia & its consequences can prevent a significant amount of visual disability in the general population