vennila.c.r refraction refractive errors refractive errors emmetropia emmetropia ametropia ametropia

Download VENNILA.C.R REFRACTION Refractive Errors Refractive Errors Emmetropia Emmetropia Ametropia Ametropia

Post on 21-Dec-2015

229 views

Category:

Documents

11 download

Embed Size (px)

TRANSCRIPT

  • Slide 1
  • Slide 2
  • VENNILA.C.R REFRACTION
  • Slide 3
  • Refractive Errors Refractive Errors Emmetropia Emmetropia Ametropia Ametropia
  • Slide 4
  • Emmetropia Emmetropia Emmetropia means no Refractive error Emmetropia means no Refractive error It is the ideal condition in which the incident parallel rays come to a perfect focus upon the light sensitive layer of the retina, When accommodation is at rest It is the ideal condition in which the incident parallel rays come to a perfect focus upon the light sensitive layer of the retina, When accommodation is at rest
  • Slide 5
  • Ametropia Ametropia Ametropia means Refractive error Eye Ametropia means Refractive error Eye It is the opposite condition, wherein the parallel rays of light are not focused exactly upon the retina, When the accommodation is at rest It is the opposite condition, wherein the parallel rays of light are not focused exactly upon the retina, When the accommodation is at rest
  • Slide 6
  • Ametropia Ametropia Myopia Myopia Hypermetropia Hypermetropia Astigmatism Astigmatism
  • Slide 7
  • Myopia Myopia Principal focus is formed in front of the retina Principal focus is formed in front of the retina
  • Slide 8
  • Causes Causes Axial Myopia Axial Myopia Curvature Myopia Curvature Myopia Index Myopia Index Myopia Abnormal position of the lens Abnormal position of the lens
  • Slide 9
  • Axial Myopia Axial myopia results from increase in anteroposterior length of the eye ball. Axial myopia results from increase in anteroposterior length of the eye ball. Normal Axial length- 23mm to 24mm Normal Axial length- 23mm to 24mm 1mm increase in AL 3Ds of Myopia 1mm increase in AL 3Ds of Myopia
  • Slide 10
  • Curvature Myopia Curvatural myopia occurs due to increased curvature of the cornea and Lens or both. Curvatural myopia occurs due to increased curvature of the cornea and Lens or both. Anterior surface of the cornea- 7.8mm Anterior surface of the cornea- 7.8mm Posterior surface of the cornea- 6.5mm Posterior surface of the cornea- 6.5mm 1mm increases in radius of curvature results in 6 Ds of Myopia 1mm increases in radius of curvature results in 6 Ds of Myopia
  • Slide 11
  • Index myopia Index myopia results from increase in the refractive index of crystalline lens. Index myopia results from increase in the refractive index of crystalline lens. Refractive index of normal Lens - 1.42 Refractive index of normal Lens - 1.42
  • Slide 12
  • Abnormal position of the lens Positional myopia is produced by anterior displacement of crystalline lens in the eye. Positional myopia is produced by anterior displacement of crystalline lens in the eye. Accommodative Myopia:. Myopia due to excessive accommodation.
  • Slide 13
  • Types Types Congenital myopia Congenital myopia Simple Myopia (or) Developmental myopia Simple Myopia (or) Developmental myopia Pathological Myopia (or) Degenerative myopia Pathological Myopia (or) Degenerative myopia Acquired myopia Acquired myopia
  • Slide 14
  • Congenital myopia Congenital myopia is present since birth however, it is usually diagnosed by the age of 2 3 years. Congenital myopia is present since birth however, it is usually diagnosed by the age of 2 3 years.
  • Slide 15
  • Simple myopia Simple or developmental myopia is the commonest variety. It is considered as a physiological error not associated with any disease of the eye. Simple or developmental myopia is the commonest variety. It is considered as a physiological error not associated with any disease of the eye. Power limit less than 6D Power limit less than 6D
  • Slide 16
  • Aetiology Axial type of simple myopia Axial type of simple myopia Curvatural type of simple myopia Curvatural type of simple myopia
  • Slide 17
  • Pathological myopia Myopia associated with degenerative changes in the eye. Myopia associated with degenerative changes in the eye. Myopia more than 6D to25D or More than 25D Myopia more than 6D to25D or More than 25D
  • Slide 18
  • Aetiology Axial growth Axial growth (i) Heredity (ii) General growth process
  • Slide 19
  • Acquired myopia Some of the causes of acquired myopia * Index myopia * Curvatural myopia * Positional myopia * Consecutive myopia * Pseudo myopia * Space myopia * Night myopia (or) Twilight myopia * Drug induced myopia
  • Slide 20
  • Symptoms Poor vision for distance Poor vision for distance Asthenopic symptoms Asthenopic symptoms Exophoria Exophoria Muscae volitantes (pathological) Muscae volitantes (pathological) Night blindness (pathological) Night blindness (pathological)
  • Slide 21
  • Signs Large eye ball Large eye ball deep Anterior chamber deep Anterior chamber sluggish Pupil sluggish Pupil Large Disc Large Disc
  • Slide 22
  • Complications Complications Retinal tear Vitreous haemorrhage Retinal tear Vitreous haemorrhage Retinal detachment Retinal detachment Degeneration of the vitreous Degeneration of the vitreous Primary open angle Glaucoma Primary open angle Glaucoma Posterior cortical cataract Posterior cortical cataract Posterior staphyloma Posterior staphyloma
  • Slide 23
  • Treatment Treatment Optical Optical Spectacle Correction (Concave Lens) Contact lens Surgical SurgicalPRKKeratomileusisEpikeratophakia Redial Keratotomy
  • Slide 24
  • Optical Treatment Concave lens Concave lens Myopic with Exophoria give full correction. Myopic with Esophoria give under correction.
  • Slide 25
  • Hypermetropia Principal focus is formed behind the retina Hypermetropia Principal focus is formed behind the retina
  • Slide 26
  • Causes Causes Axial Hypermetropia Axial Hypermetropia Curvature Hypermetropia Curvature Hypermetropia Index Hypermetropia Index Hypermetropia Abnormal position of the lens Abnormal position of the lens
  • Slide 27
  • Axial Hypermetropia Axial hypermetropia is by far the commonest Axial hypermetropia is by far the commonest In fact, all the new- borns are almost invariably hypermetropic (approx,+2.50D) This is due to shortness of the globe, and is physiological. In fact, all the new- borns are almost invariably hypermetropic (approx,+2.50D) This is due to shortness of the globe, and is physiological. Normal axial length 23mm to 24mm Normal axial length 23mm to 24mm 1mm decrease in AL 3Ds of hypermetropia 1mm decrease in AL 3Ds of hypermetropia
  • Slide 28
  • Curvature Hypermetropia In which the curvature of cornea, Lens or both is flatter than the normal resulting in a decrease in the refractive power of the eye. In which the curvature of cornea, Lens or both is flatter than the normal resulting in a decrease in the refractive power of the eye. Anterior surface of the cornea- 7.8mm Anterior surface of the cornea- 7.8mm Posterior surface of the cornea- 6.5mm Posterior surface of the cornea- 6.5mm 1mm increase in radius of curvature results in 6Ds of hypermetropia 1mm increase in radius of curvature results in 6Ds of hypermetropia
  • Slide 29
  • Index Hypermetropia Index hypermetropia occurs due to change in refractive index of the lens in old age. It may also occur in diabetics under treatment. Index hypermetropia occurs due to change in refractive index of the lens in old age. It may also occur in diabetics under treatment. Refractive index of Normal Lens- 1.42 Refractive index of Normal Lens- 1.42
  • Slide 30
  • Classification Classification Total Hypermetropia may be divided into Total Hypermetropia may be divided into (a) Latent Hypermetropia (a) Latent Hypermetropia (b) Manifest Hypermetropia (b) Manifest Hypermetropia (i) Facultive Hypermetropia (i) Facultive Hypermetropia (ii)Absolute Hypermetropia (ii)Absolute Hypermetropia
  • Slide 31
  • Latent Hypermetropia LH which is corrected physiologically by the tone of ciliary muscle. As a rule latent hypermetropia amounts to only one dioptre. It can be revealed only after atropine cycloplegia. LH which is corrected physiologically by the tone of ciliary muscle. As a rule latent hypermetropia amounts to only one dioptre. It can be revealed only after atropine cycloplegia.
  • Slide 32
  • Manifest Hypermetropia MH is made up of two components Facultative hypermetropia is that part of hypermetropia which can be corrected by the effort of accommodation. Facultative hypermetropia is that part of hypermetropia which can be corrected by the effort of accommodation. Absolute hypermetropia which can not be overcome by the effort of accommodation. Absolute hypermetropia which can not be overcome by the effort of accommodation.
  • Slide 33
  • Clinical Types Simple hypermetropia Simple hypermetropia Pathological hypermetropia Pathological hypermetropia Functional hypermetropia Functional hypermetropia
  • Slide 34
  • Simple hypermetropia It results from normal biological variation in the development of the eye ball. It includes Axial and Curvatural HM. It may be hereditary. It results from normal biological variation in the development of the eye ball. It includes Axial and Curvatural HM. It may be hereditary.
  • Slide 35
  • Pathological hypermetropia PH results due to either co

Recommended

View more >