Refractive Errors Amblyopia Squints

Refractive errors Amblyopia Squints

Refractive errors • Rays of light entering the eye are refracted by the cornea and the lens to form an image on the retina • If the axial length of the eye is too short image will form behind the retina (hypermetropia) • If the axial length of the eye is too long image will form in front of the retina (myopia) • If the refracting power of the cornea and lens is different in one meridian than inother(astigmatism) Reduced visual acuity will result

Refractive errors • Presbyopia The lens of every eye suffers a progressive loss of ability to become more convex (accommodation) with increasing age. • It is manifested by a decreased ability to focus upon near objects while distance VA remains normal. • Presbyopia is corrected with convex lenses in lower segment of the spectacle

Refractive errors

Refractive errors Corrected with glasses

Refractive errors Hard Contact lens

Amblyopia • It is defined as unilateral defective vision, uncorrectable by glasses, in otherwise normal eye. • It is diagnosed when the best corrected visual acuity in an apparently normal eye is two or more lines poorer than in the fellow eye • Crowding phenomenon in which visual acuity is better with single letters than with a whole raw of letters

Amblyopia • Why the child get amblyopia? It develops in young children in whom visual information received by the brain from one eye is inadequate or conflicts with information from the other eye. • The cortical cells receiving inadequate visual information fail to develop properly, their function is actively inhibited.

Amblyopia • Amblyopia may occur in several ways Stabismic amblypia two eyes are misaligned, one eye is looking at the object of regard and neglect of sensory input from the opposite eye E.g.:-cataracts

Refractive amblyopia(anisometropic)

When there is a marked difference in refractive errors of the two eyes

Occlusion amblypia(stimulus deprivation) When opacities of the ocular media prevent adequate sensory input E.g.:- cataracts, corneal opacities

Meridional amblypia

Occurs with marked degrees of astigmatism

Amblyopia • How to treat? -Occlusion of the other eye. (Monitor carefully to avoid causing sensory deprivation amblyopia of the occluded eye) -Treat the cause.

Squints

Squints • The eyes are looking in different directions because their visual axes are not parallel -Convergent squint (esotropia) -Divergent squint -Hypertropia -Hypotropia

(exotropia)

Squints • Causes of squints Normally, a complex set of reflexes keep the two eyes always pointing in the same direction. These reflexes involve both the sensory and motor parts of the nervous system Sensory part - Takes the two images produced by two eyes join together in the brain. Motor part -Makes sure that the two eyes always move together to one direction The squint occurs when something goes wrong with these reflexes

Squints • Disorders of the vision One eye is diseased –image is blurred Eg-corneal scar,cataract,retinal disease,optic nerve disease

• Disorders of the eye movements This may be in the muscles or nerve supply 1.Congenital abnormalities 2.Fractures of the orbital walls 3.Dysthyroid eye disease 4.Generalized muscle disease

• Refractive errors One eye error will blur the vision and it may cause squint

Squints

Squints

Squints

Squints

Squints Esotropia ( infantile esotropia )

Squints Esotropia ( infantile esotropia )

Squints Esotropia (refractive,accommodative)

Squints Esotropia corrected with glasses

Exotropia

Squints

Squints Alternating divergent squint

Squints

Esotropia due to Right 6th nerve paralysis

Squints

Exotropia due to right frontal sinus mucocele

Squints Surgery