DISEASES OF LENS (Cataract) Causes and Risk Factors, Classification, Clinical Manifestations, Diagnostic Evaluations and Nursing Management
A cataract is a clouding or opacity that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light. The term cataract is derived from the Greek word cataractos, which describes rapidly running water. When water is turbulent, it is transformed from a clear medium to white and cloudy. Cataracts typically progress slowly to cause vision loss and are potentially blinding if untreated.
CAUSES AND RISK FACTORS
- Age: the incidence increases after the age of 65
- Heredity: due to an anomaly in the chromosomal pattern of the individual
- Exposure to ultraviolet rays over the life span
- People who live at high altitudes
- Chronic exposure to heat (industrial workers)
- Glass blowers and welders without eye protection
- Intraocular disorders such as retinitis pigmentosa, uveitis, myopia, glaucoma and retinal detachment
- Medications those are phototoxic such as tetracycline, phenothiazines, thiazides, tranquilizers, oral contraceptives and corticosteroids
CLASSIFICATION OF CATARACT
A - Etiological Classification
- Congenital Cataract: When the disturbance occurs before birth, the child is born with congenital cataract. Etiological factors include genetic factors, malnutrition, infectious diseases during first trimester of pregnancy (German measles, mumps, chickenpox, hepatitis), radiation and drug ingestion (thalidomide), birth trauma, metabolic disorders or infectious diseases of the infant.
- Acquired Cataract: In acquired cataract opacification occurs due to degeneration of the already formed normal lens fibers
- Senile Cataract: it is also called as age related cataract. A senile cataract is characterized by an initial opacity in the lens, subsequent swelling of the lens and final shrinkage with complete loss of transparency. It may occur due to denaturation of lens proteins and opacification of cortical lens fibers.
- Traumatic Cataract: most commonly due to penetrating or blunt injury to the eye, lacerations, and foreign bodies in the eye.
- Complicated Cataract: it refers to the opacity of lens secondary to some other intraocular diseases. It is also called as secondary cataract.
- Metabolic Cataract: metabolic cataract occur due to endocrine disorders and biochemical abnormalities.
- Radiation Cataract: exposure to almost all types of radiation is known to produce cataract by causing damage to the lens epithelium. It may result from overexposure to heat, x-rays, UV rays, infra-red rays and radioactive materials.
- Electric Cataract: it is known to occur after passage of powerful electric current through the body
- Dermatogenic Cataract: cataract associated with the skin diseases such as atopic dermatitis.
- Toxic Cataract: medications those are phototoxic such as tetracycline, phenothiazines, thiazides, tranquilizers, oral contraceptives and corticosteroids also cause cataract.
B – Morphological Classification
- Capsular Cataract: it involves the capsule and may be anterior capsule or posterior capsule
- Sub capsular cataract: it involves superficial part of the cortex (just below the capsule) and includes anterior sub capsule or posterior sub capsule
- Cortical cataract: the lens fibers of the cortex are mainly affected. There is hydration due to accumulation of water droplets in between the fibers and the protein are first denaturated and then are coagulated forming opacity.
- Supranuclear cataract: it involves only the deeper parts of the cortex (just outside the nucleus)
- Nuclear cataract: it involves the nucleus of the crystalline lens. The nucleus becomes diffusely cloudy and obstructs the light rays
- Polar cataract: it involves the capsule and superior part of the cortex in the polar region only and may be anterior polar cataract or posterior polar cataract.
A cataract is a gradually developing opacity of the lens or lens capsule of the eye. The crystalline lens is a transparent structure. Its transparency may be disturbed due to degenerative process leading to opecification of the lens fibers. The lens focuses light rays on the retina-the layer of light-sensing cells lining the back of the eye-to produce a sharp image of what we see. When the lens becomes cloudy, light rays cannot pass through it easily, and vision is blurred.
Pathophysiology may vary with each form of cataract. Senile cataract show evidence of denaturation of lens protein, oxidative injury and increased pigmentation in the center of the lens due to accumulation of water and an increase in sodium content. Due to these changes the lens becomes cloudy, light rays cannot pass through it easily, and blurred image is cast onto the retina. Cataract usually affects both the eyes, but almost always one eye is affected earlier than the other.
Cataract progress through the following clinical stages of the development:
- Immature cataract: In immature cataract the lens of the eye is not completely opaque
- Mature cataract: in this stage, the lens is completely opaque and vision is significantly reduced
- Intumescent cataract: in this stage the lens absorbs water and increases in the size
- Hypermature cataract: hyper mature cataract are those in which lens protein break down into short chain polypeptides that leak through the lens capsule
- Gradual painless burring and
- Loss of vision due to lens opacity
- Increased glare in bright light
- Decreased color perception
- Decreased visual acuity
- Poor vision at night
- Photophobia (light sensitivity)
- Blurred or distorted images
- Light scattering
- Leukokoria or white pupil
- Reduced light transmission
- Contrast sensitivity is also lost
- Determine presence of risk factors in individual’s life style
- Direct ophthalmoscopy
- Slit-lamp biomicroscopy
- Refraction and retinoscopy
- Snellen visual acuity test
- Glare testing
- Penlight examination of pupil and lens
Surgery is the definitive treatment for cataracts. Most cataract surgery is performed in the ambulatory surgery centers, few patient require hospitalization. Common surgical procedure for cataract includes:
When a cataract is sufficiently developed to be removed by surgery, the most effective and common treatment is to make an incision (capsulotomy) into the capsule of the cloudy lens in order to surgically remove the lens. There are two types of eye surgery that can be used to remove cataracts:
- Extra Capsular Cataract Extraction: ECCE consists of removing the lens and the anterior portion of the lens capsule manually. The posterior capsule is left intact to support an IOL.
- Intra Capsular Cataract Extraction: In ICCE instruments are used to remove the entire lens and capsule manually. In either extra-capsular surgery or intra-capsular surgery, the cataractous lens is removed and replaced with the plastic lens 9an intraocular lens implant) which stays in the eye permanently
- Phacoemulsification: A titanium needle vibrating at ultrasonic frequencies (high frequency sound waves) used to disrupt the lens nucleus. The needle vibrates at ultrasonic frequency (40,000 Hz) and the lens material is emulsified. A second fine instrument (sometimes called a cracker or chopper) may be used from a side port to facilitate cracking or chopping of the nucleus into smaller pieces. The anterior capsule and lens particles are removed from the eye by irrigation and aspiration through a sleeve around the needle. The posterior capsule is left intact to support an IOL.
- Intraocular Lens Implantation: after the removal of the cataract, an intraocular lens (IOL) is usually implanted into the eye, either through a small incision (1.8 mm to 2.8 mm) using a foldable IOL, or through an enlarged incision, using a PMMA (polymethylmethacrylate) lens. The lens implanted is inserted through the incision into the capsular bag within the posterior chamber (in-the-bag implantation). There are a variety of intraocular lens styles available for implantation, including monofocal, toric, and multifocal intraocular lenses.
- Monofocal Lens: These lenses are the most commonly implanted lenses today. They have equal power in all regions of the lens and can provide high-quality vision at a single focal point (usually at distance). They usually require only a light pair of spectacles for optimal distance vision correction. However, monofocal lenses do not correct astigmatism, an irregular oblong corneal shape that can distort vision at all distances, and require corrective lenses for all near tasks, such as reading or writing.
- Toric Lens: Toric lenses have more power in one specific region in the lens (similar to spectacles with astigmatism correction in them) to correct astigmatism, which can further improve unaided distance vision for many individuals. Due to the difference in lens power in different areas, the correction of astigmatism with a toric lens requires that the lens be positioned in a very specific configuration. While toric lenses can improve distance vision and astigmatism, they still require corrective lenses for all near tasks, such as reading or writing.
- Multifocal Lens: Multifocal intraocular lenses have a variety of regions with different power within the lens that allows individuals to see at a variety of distances, including distance, intermediate, and near. While promising, multifocal lenses are not for everyone. They can cause significantly more glare than monofocal or toric lenses. Further, multifocal lenses cannot correct astigmatism, and some patients require additional surgery such as LASIK to correct astigmatism and maximize their unaided vision
- Contact Lens: extended wear contact lens is an option for those who do not receive IOL implantation. They restore binocular vision and result in magnification of images.
- Cryosurgery: Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen. In this technique, the cataract is extracted through use of a cryoextractor – a cryoprobe whose refrigerated tip adheres to and freezes tissue of the lens, permitting its removal.
- Activity/Rest: The change from the usual activities/hobbies in connection with visual impairment
- Neurosensory: Impaired vision blurred/can clear, bright light causes glare with a gradual loss of peripheral vision, difficulty focusing work with closely or feel the dark room. Vision cloudy/burry, looking halo/rainbow around the beam, changes eyeglasses, medication does not improve vision, photophobia (acute glaucoma)
- Signs: Looks brownish or milky white in the pupil (cataract), the pupil narrows and red/hard eye and a cloudy cornea (glaucoma emergency, increased tears)
- Pain/Leisure: Discomfort light/watery eyes. Sudden pain/heavy persist or pressure on or around the eyes, headaches.
- The patient’s preoperative preparation begins with appropriate history and physical examination
- Ask the patient to perform face scrub and cut eyelashes before admission in to operating room. Monitor and record complete vital signs of the patient before surgery
- Explain about the events as they will take place in the operating room to reduce fear and anxiety of the patient.
- Explain about surgery and expected postoperative care to patient and their family members
- Instruct the patient not to have food and fluids/for approximately 6 to 8 hours before surgery.
- Administer mydriatics (alpha-adrenergic agonist) and cycloplegic (anticholinergic) drug to dilate and paralyzed pupil of the operative eye
- Instill nonsteroidal anti-inflammatory eye drops to reduce inflammation and to help maintain pupil dilation
After cataract surgery most patients are discharged within the few hours. Immediate postoperative care of the patient after cataract surgery includes the following:
- Take vital signs immediately after surgery to determine status of the patient
- Instruct the patient to avoid sneezing, coughing an straining because these actions may increase the intraocular pressure
- Avoid pressure on operated eye by placing/positioning patient on back or unoperated side
- Instruct the patient to sleep on the unoperated side top prevent pressure on the incision
- Demonstrate eye drop instillation technique and instillation of ophthalmic ointment using aseptic techniques
- Administer antibiotics to prevent infections and anti-inflammatory drugs (corticosteroids drops) to reduce inflammation after surgery
- Post operative patient may have some scratchiness in the operative eye. Mild analgesics are usually beneficial to relieve any pain. If the pain is intense this may indication of hemorrhage, infection or increased IOP.
- Explain proper hygiene and eye care technique to prevent contamination of the surgical eye
- Encourage the patient to wear eye shield at night to protect operated eye from injury while sleeping
- Encourage the patient to wear dark glasses after eye dressing are removed to provide comfort form photophobia due to lack of pupil constriction from mydriatics and cycloplegic drops
- Teach the patient to maintain appropriate intake of antioxidant vitamins (vitamin C and E) and good nutrition
- Place the items of need within the easy reach of the patient
- Encourage the patient to avoid lifting heavy objects, isometric exercises or straining during defecation to prevent fluctuation in IOP
- Educate the patient and family about the signs and symptoms of infection and tell to report early for possible treatment
- Caution him to avoid activities that increase intraocular pressure, such as straining with coughing, bowel movements, or lifting
- Clients fitted with cataract eyeglasses need information about altered spatial perception. The eyeglasses should be first used when the patient is seated, until the patient adjusts to the distortion. Instruct the client to look through the center of the corrective lenses and to turn the head, rather than only the eyes, when looking to the side. Clear vision is possible only through the center of the lens. Hand-eye coordination movements must be practiced with assistance and relearned because of the altered spatial perceptions
- Teach the patient or family member how to instill ophthalmic ointment or drops
- Driving, sports and machine operation can be resumed when permission is granted by the eye surgeon.
- If the patient has increased eye discharge, share eye pain, or deterioration in vision, instruct him to immediately notify the physician.
DISEASES OF LENS (Cataract) Causes and Risk Factors, Classification, Clinical Manifestations, Diagnostic Evaluations and Nursing Management