Opthalmology | Master Of Medicine

Category Archives: Opthalmology

Features of Pterygium and its difference from pinguecula.

Pterygium and Pinguecula are two names which are so similar that we often make mistakes when either is asked.So let us differentiate.

Pterygium


  1. Wing shaped fold of conjunctiva encroaching upon the cornea from either side of interpalpebral fissure
  2. Common in hot climates and in elderly males
  3. Pterygium is a degenerative and hyperplastic condition of conjunctiva.Subconjunctival tissue undergoes elastotic degeneration and proloferates as vascularised granulation tissue which encroaches upon the cornea, destroying the corneal epithelium,bowmans layer and superficial stroma.
  4. Pterygium can be unilateral or bilateral.
  5. It usually appears as a triangular fold of conjunctiva on nasal side of palpebral aperture, but it appears on temporal side also.
  6. Stockers line:Deposition of iron in corneal epithelium anterior to the advancing head of the pterygium.
  7. Asymptomatic in early stages, interferes with vision when it encroaches the pupillary area.

Pterygium has 3 parts:

  • Head – Anterior most part, present on cornea.
  • Neck – Limbal part.
  • Body – Scleral part.

Pinguecula

  1. Pinguecula is named so because of its resemblance to fat(pinguis)
  2. Common degenerative condition of the conjunctiva,characterised by formation of yellowish white patch on bulbar conjunctiva, near the limbus.
  3. Seen in persons exposed extremes of climate, heat,wind etc.
  4. Pinguecula is considered as a precursor of pterygium.

Vision 2020:Right to sight

Vision 2020:Right to sight, is an internatioonal initiative started by WHO in 1999 along with Task force of International NGO’s. It aims at dealing with 5 major conditions which cause blindness.

  1. Cataract
  2. Childhood blindness
  3. Trachoma
  4. Refractive errors and low vision
  5. Onchocerciasis(River bindness)

The Indian govt has adopted Vision 2020:Right to sight under National Programme for control of blindness in 2001. Diseases included in India are:

  1. Cataract
  2. Childhood blindness
  3. Trachoma
  4. Refractive errors and low vision
  5. Corneal blindness
  6. Diabetic retinopathy
  7. Glaucoma

River blindness was excluded from the list and three diseases added to the list.

Visual pathway and LGB

  • Lateral geniculate body is relay station on visual pathway.
  • Receives fibres from ipsilateral temporal hemiretina and contralateral nasal hemiretina.
  • Grey matter of LGB is split into 6 lamina.
  • Fibres from ipsilateral temporal hemiretina ends in- 2,3,5.
  • Fibres from contralateral nasal hemiretina ends in-1,4,6.
  • Magnocellular and parvocellular pathways project to occipital cortex(area 17)

Magnocellular pathway

Detects depth and movement flicker.

Originates from layers 1 and 2

Parvocellular pathway

Carries information regarding color,texture ,shape and fine details of objects.

Originates from layers 3,4,5,6.

Layers of retina

  1. Pigmented epithelium
  2. Layer of rods and cones
  3. External limiting membrane
  4. Outer nuclear layer
  5. Outer plexiform layer
  6. inner nuclear layer
  7. Inner plexiform layer
  8. Ganglion cell layer
  9. Nerve fibre layer
  10. Internal limiting membrane

Squint

Orthotropia

Exotropia

Esotropia

When eye is uncrossed diplopia is crossed, seen in divergent squint.

Concomitent squint

primary deviation= secondary deviation

No diplopia in concomitent squint.

If secondary deviation>primary, paralytic squint

Accomodative Esotropia-Hypermetropia,corrected by spectacles

Infantile Esotropia-b/l weakness in MR,Treatment is surgery(Bimedial resection)

Large angle esotropia-IO overactive,Latent nystagmus,cross fixation

Amblyopia

Lazy eye.

Stimulate lazy eye by covering the other eye for 2-3 months and do surgery for squint.

Stickler’s syndrome

Autosomal dominant

Optically clear vitreous

Associated with ectopia lentis

Presenile cataract

Glaucoma and vertical lattice degneration

Falttened nasal bridge,telecanthus,micrognathia,glossoptosis

Mimick pierre robbin anomaly

CRAO and CRVO

CRAO

  1. Carotid atherosclerosis is commonest cause of CRAO in elderly
  2. In young-Cardiac emboli.
  3. CAttle trucking appearance

Mnemonic:CRAO=CAttle

Treatment:

  1. Paracentesis by letting out
  2. Mannitol,acetazolamide
  3. Carbogen mixture-Inhaled CO2 ,causes systemic vasodilation.

CRVO

Ischaemic and NonIschaemic types

Vision<6/60

RAPD

Retinal hemorrhages

Vision loss is due to macular edema due to venous occlusion

Nonishaemic type is converted to ischaemic type in normal course of disease

Appearance of IRIS/Angle neovascularization-Indication for LASER photocoagulation.

Hundredth day glaucoma-CRVO,neovascularization in 3rd month.

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