CataractThe lens• Biconvex, transparent organ, Lies in the posterior chamber of the eye between the posterior surface of the iris and the vitreous body. held in position behind the iris by suspensory ligament (zonular fibers) whose fibers are composed of the protein fibrillin.

- Zonular fibers connect between ciliary body and lens capsule. These fibers hold the lens in position and transmit changes in the ciliary muscle allowing the lens to change its shape and refractive power .

- Functions : Refraction and focuses incident rays of light on the retina.

- Nourished by diffusion from the aqueous humor.

Histology:1. Capsule : replicated basal lamina, formed from the basement membrane of the epithelium.2. Subcapsular epithelium (simple cuboidal).- lens fibre production.-Synthesis of crystalline and membrane proteins- transport ions and water3. Lens fibers are nucleated in the cortex . As new lens fibers are added to the periphery of the cortex, lens fibers located deeper in the cortex lose their nuclei and become part of the harder nucleus of the lens.

- The water content of the lens is normally stable and in equilibrium with the surrounding

aqueous humor.

- The water content of the lens decreases with age, whereas the content of insoluble lens

proteins (albuminoid) increases.

- The lens becomes harder, less elastic (Loss of accommodation), and less transparent.

- The decrease in the transparency of the lens with age is as unavoidable.

- The nucleus of the lens becomes sclerosed and slightly yellowish .

Definition and causes of cataract

- Cataract is the name given to any light - scattering opacity within the lens wherever it is located.

- When it lies on the visual axis or is extensive (transparency of the lens is reduced ) , it gives rise to visual loss.

- Cataract is the commonest cause of treatable blindness in the world.

- In older subjects, as a result of cumulative exposure to environmental and other influences, such as smoking , UV radiation and elevated blood sugar levels . This is referred to as age - related cataract .

- More common in females .

• WHEN EYES WORK PROPERLY:

-Light passes through the cornea and the pupil to the lens.

-The lens focuses the light and produces clear sharp images on the retina..

• AS A CATARACT DEVELOPS :

• The lens becomes clouded, which scatters the light and prevents a sharply defined image from reaching the retina, as a result vision becomes blurred.

Symptoms:• A painless gradual loss of vision.

• Glare.

• Change in refraction.

Altered colour perception . Halos around lights . Double vision.

In infants, cataract causes amblyopia (a failure of visual maturation) ,by depriving the retina of a formed image at a critical stage of visual development.

Signs• Visual acuity is reduced .

• A cataract appears black against the red reflex when examined by direct ophthalmoscope .

• Reduced contrast .

• Severe dense cataract causes a white pupil.

• Slit - lamp examination allows the cataract to be examined in details, and the exact site of the opacity in the lens can be identified.

• Normal red reflex is : Diffuse bright red

• Causes of dim red reflex : anything that interferes with the passage of light from cornea to retina

1- Corneal ulcer , keratitis

2- Hyphema

3- Cataract

4- Vitreous hemorrhage

- NOT GLAUCOMA

Classification : Cataract can be classified according to :

• Cause : acquired vs congenital.

• Anatomical : nuclear , cortical , sub-capsular.

• Degree of

clouding (degree of loss of the normal transparency) : Immature , mature , hyper-mature.

• Investigations

Required if :

1. Systemic disease is suspected

2. Cataract is congenital

3. Appears at an early age.

• Treatment

Management remains surgical.

• lens

implant is calculated prior to surgery by measuring the length of the eye ultrasonically and the curvature of the cornea (and thus its optical power) optically ( biometry ).

• The power of the lens is generally calculated to provide good distance acuity without glasses (i.e. emmetropia).

• The choice of implant power is influenced by the refraction of the fellow eye and whether it too has a cataract which will require surgery.

• Where surgery on the fellow eye is likely to be delayed, it is important that the patient is not left with a major difference in the refractive state of the two eyes (aniseikonia), since the difference in retinal image size may not be tolerated visually.

• Postoperatively the patient is given a short course of steroid and antibiotic drops.

• New glasses, if required, can be prescribed after a few weeks, once the incision has healed.

• Visual rehabilitation and the prescription of new glasses is much quicker after phacoemulsification.

Complication of cataract surgery

1. Corneal astigmatism

2. Vitreous loss

3. Iris prolapse

4. Endophthalmitis

5. Cystoid macular oedema

6. Retinal detachment. , increased if there has been vitreous loss.

7. Opacification of the posterior capsule

8. Irritation or infection.

-- If the fine nylon sutures are not removed after surgery they may break in the following months or years, Symptoms are cured by removal

*Corneal astigmatism • Postoperative removal of sutures that were used under local anaesthetic with the patient

sitting at the slit lamp may reduce this.

• Loose sutures must be removed to prevent infection but it may be necessary to resuture the incision if healing is imperfect.

• Sutureless phacoemulsification through a smaller incision avoids these complications.

*Vitreous loss• If the posterior capsule is damaged during the operation the vitreous gel may come

forward into the anterior chamber, where it represents a risk for glaucoma or may cause retinal traction.

• The gel requires careful aspiration and excision ( vitrectomy ) at the time of surgery and placement of the intraocular lens may need to be deferred to a secondary procedure.

*Iris prolapse

• The iris may protrude through the surgical incision in the immediate postoperative period.

• It appears as a dark area at the incision site. The pupil is distorted.

• This requires prompt surgical repair.

*Endophthalmitis • Rare infective complication of cataract extraction (less than 0.3%). Extreme ophthalmic

emergency

• Patients present, usually within a few days of surgery with:

1. painful red eye

2. reduced visual acuity

3. Collection of white cells in the ant. chamber (hypopyon)

Management :

• Urgent sampling of the aqueous and vitreous for microbiological analysis.

• Intravitreal, broad - spectrum, antibiotic injection at the time of sampling (e.g. vancomycin and ceftazidime) to provide immediate cover.

• Further injections are dependent on the microbiological report and clinical response. In some instances topical and systemic antibiotics are used in addition .

*Cystoid macular oedema • Cystoid macular edema or CME, is a painless disorder which affects the central retina or macula. When this condition is present, multiple cyst-like (cystoid) areas of fluid appear in the macula and cause retinal swelling or edema

• The macula may become edematous following surgery, particularly if surgery was accompanied by vitreous loss or followed by inflammation.

• Can produce a severe reduction in acuity.

• Inflammatory prostaglandin release may play a part in this .

• Treatment with topical NSAIDs and steroid can alleviate the oedema

• Sometimes it may require treatment with steroids injected into or around the eye.

*Opacification of the posterior capsule. -Normally, the thin capsular layer behind the implant is crystal clear. However, in 20% of patients clarity of the posterior capsule decreases in the months following surgery, when residual epithelial cells migrate across its surface to form an opaque scar.

-Vision becomes blurred and there may be problems with glare.

-A small opening can be made in the capsule with a laser ( neodymium yttrium garnet (ndYAG) laser ) as an outpatient procedure. There is a small risk of cystoid macular oedema or retinal detachment following YAG capsulotomy.

-The lens implant material, the shape of the edge of the lens And overlap of the intraocular lens by a small rim of anterior capsule are important in preventing posterior capsule opacification.

A 60 - year - old lady presented to her GP with gradual loss of vision over some months. She noticed that the problem was particularly bad in bright sunshine. The eye was not painful or red. She was otherwise well.

Questions -What is the probable diagnosis? -How can the diagnosis be confi rmed? - What treatment may be advised?