Optics and Refractive errors correction

ByDr. ABDULMAJID ALSHEHAH

Ophthalmology consultantAnterior Segment and Uveitis consultant

Contents

• Basic optics.• Refractive power of the eye.• Refractive status of the eye.• Refractive errors.• Eyeglasses. • Contact lenses.• Refractive surgery.• Visual aids.

Basic optics

Light

• In physics, the term light refers to electromagnetic radiation of any wavelength, whether visible or not.

Light

• Visible light (commonly referred to simply as

light) is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has a wavelength in the range of about 380 nanometres (nm), or 380×10−9 m, to about 740 nanometres – between the invisible infrared, with longer wavelengths and the invisible ultraviolet, with shorter wavelengths

Lenses

Refractive power of the eye

Refractive status of the eye.

• EmmetropiaRefractive state of the eye

when parallel rays of light from a distant object are brought to focus on the retina with the eye at rest (i.e. not accommodating)

When out of focus on the retina : Ametropia

Refractive errors (Ametropia)

• Myopia (nearsightedness or shortsightedness)

• Hyperopia (hypermetropia ,farsightedness or;

longsightedness)

Astigmatism

Astigmatism

Presbyopia

Presbyopia correction

• Glasses • Bifocal if ametropic

• Surgery include corneal and lens exchange procedures but still patient satisfaction is not encouraging

Corrective lenses

Spherical lenses Cylindrical lenses

Glasses prescription

Eye glasses

Eye glasses

Limitation • Cosmetic• Discomfort.• Limited clear visual field.• Sports• Magnification and

minification • High Astigmatism correction

Complications • Almost None

Contact lenses

Corrective Cosmetic

Contact lenses

Limitation• Expensive • Daily care• Allergy

Complications • Infection• Infection • Infection • Corneal ischemia• Corneal thinning

Corneal Refractive surgery

• LASIK Laser In-Situ Keratomileusis

• LASEK Laser sup-epithelial Keratomileusis

• EPI-LASIK Epithelial Laser In-Situ Keratomileusis.• INTRALSE-LASIK (Femto-LASIK)

Corneal Refractive surgery

Limitation• High refractive errors• Keratoconus patients

(clinical and subclinical)

Complications• Infection• Scarring• Dryness• Residual error• Overcorrection

Non-Corneal Refractive surgery

• Phakic intraocular lens insertion• Clear lens extraction• Cataract surgery.

Vision Aids

Questions