Crystalline Lens It is biconvex and transparent lens , lies behind the pupil & iris, in front of the vitreous. It is suspended by the Zonules, arising from the ciliary processes (ciliary body), extending centrally to attach to the equator of the lens. Lens is surrounded by the elastic capsule which is a basement membrane secreted by the lens epithelium. Ant. lens epithelium: Lens fibers: arise from the epithelium at the equator.

Crystalline Lens

Lens Epithelium & Zonules

Diopteric (Refractive) power of the eye ≈ 60 diopter Functions of the Lens 1. Transmits light: (transparent). 2. Refracts light: act as convex lens which converge light rays.. Diopteric (Refractive) power of the eye ≈ 60 diopter 40 d. (cornea) + 20 d. (lens) ● But the cornea is static (does not change its shape & power).. ● While the lens is Elastic & can change its shape, convexity & power in response to the changes in the ciliary muscle tone & hence zonular tension. 3. Accommodation: human eye can focus & see clearly objects at different distances.. When we look at infinity (6m).. The ciliary muscle is relaxed  dilatation of ciliary ring  stretch of zonules  flat (↓convexity) of the lens..

Accommodation

When we look at near object, the ciliary muscle will contract  ↓ diameter of the ciliary ring  relaxation of the zonules  lens will restore spherical shape due to its elasticity, and its convexity and power will ↑. SO, If we look at an object 2 meters away, we need to ↑ lens power by 0.5 diopter [3m  1/3d. | 50cm  2d.]

Presbyopia Aging process, due to ↓ elasticity of the lens with age, its ability to accommodate will ↓. At age 40-45 years, every person will need a convex lens (glasses) to assist his near vision.. The condition is progressive, so the power of reading glasses need to be increased frequently.. Earlier in hypermetropia… Later or never happened in myopia..

Presbyopia

Congenital Anomalies of Lens Congenital Cataract: either Hereditary. AD or Acquired in utero, e.g..: maternal inf. (Rubella), or Metabolic disease (Galactosemia). Ectopia Lentis: due to zonular rupture or laxity, the lens either completely displaced (dislocation) or partially displaced (subluxation), It is either: Hereditary 1- Marfan Syndrome 2- Homocystinuria 3- Ehler Danlos Syndrome 4- Familial (AR) Or Acquired 1- Trauma 2- High myopia 3- Buphthalmos

Coloboma of the lens: in fact it is coloboma of the zonules which are mesodermal in origin, but it appear as a notch in the lens…

Congenital Cataract

Congenital Cataract

Ectopia Lentis

Ectopia Lentis

Coloboma of the lens

Cataract الساد، الماء الأبيض Definition: Any opacity of the lens. N.B: A. Not all cataracts are clinically significant: depends on: 1. Size 2. Site e.g.: Post. subcapsular cataract versus ant. cataract B. Opacity differ in the level, e.g.: Capsular  Subcapsular  Cortical  Nuclear

Cataract

Posterior subcapsular cataract

Anterior subcapsular

Capsular cataract

Cortical cataract

Nuclear cataract

Mature cataract

Aetiology: Senile: most common Traumatic: - blunt - penetrating - infrared (glass blowers) XR, UV Congenital - hereditary - maternal dis., e.g.: Rubella (TORCH) Secondary to syst. causes, e.g: - D.M. - galactosemia - atopic dermatitis - dyst. myotonica - drugs: steroid, chloropr. Complicated: ocular diseases: - glaucoma -myopia - uveitis -retinitis pigmentosa -retinal detachment

Clinical Picture: Blurring of vision: Painless, Gradually progressing. Refractive error: Nuclear = myopia Cortical = hypermetropia Altered color values: Glare: strong light  scattered by the opacity Mononuclear diplopia or polyopia Leukocoria : dense cat. (pediatric)  white pupil

Blurred vision

Diagnosis: this is done by: Direct ophthalmoscope: red reflex is partially or completely obscured.. Slit lamp..

Devices for diagnosis

Evaluation of retinal functions, esp. in dense cataract: a. V.A. b. Light perception c. Pupillary reaction (optic N.) d. 4 quadrant projection e. Color discrimination f. US, B-scan

B-scan

Further management: Medical: Glasses to correct refractive errors. Dark glasses. Mydriatic eye drops. Surgical: Definitive treatment. Indications: VISUAL, MEDICAL (DM, Optic Nerve dis. Glaucoma) and COSMOTIC Two components: (a) Cataract Extraction + (b) Optical Correction

A) Cataract Extraction: Intra Capsular Cataract Extraction (ICCE): whole lens (with caps.) is removed. - cryoprobe.. Extra Capsular Cataract Extraction (ECCE): microsurgery – anterior capsulotomy remove the nucleus and cortex, leave posterior capsule. Phacoemulsification: capsulorrhexis, US probe (very rapid vibrating)  phacolysis, most recent and preferred.. small incision 3.2 mm, ↓↓ less wound complications.. Lensectomy: used in congenital cataract, vitrectomy machine , lens and anterior face of the vitreous..

ECCE

Phacoemulsification

B) Optical Correction: High hypermetropia).. (Aphakic eye) Glasses ≈ +10 image magnified 30%  anisoconea Contact lens 6% Intraocular lens, IOL (Silicon-PMMA, …etc) Ant. chamber AC-IOL 1-2% Post. chamber PC-IOL (foldable, injectable)

Glasses

Contact lens

Ant. & post. Cham. lens

Foldable lens

Complication of Cataract Surgery: Surgical hyphema: Vitreous loss: Endophthalmitis: pain, ↓vision, hypopyon. (intravitreal AB, subconj., topical). Pars Plana Vitrectomy (PPV) Expulsive choroidal hemorrhage: Wound dehiscence: Astigmatism.. Cystoid macular edema Retinal detachment: Glaucoma: Corneal endothelium decompensation

Hyphema

Endophthalmitis

Expulsive choroidal hemorrhage

Retinal detachment

Retinal detachment