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Label
Cataract

DefinitionEtiologyEpidemiologyPathophysiologyClinical Presentation
WorkupGoalsMed ChoicesClinical TrialsPipeline AgentsResourcesRefs
Definition:

Opacity or cloudiness of the lens of an eye, causing partial or total impairment of vision.

There are 3 most common types of senile (age related) cataracts; defined by their location within the lens:

  • Nuclear: Progression of a yellow to dark brown hue of the lens with increase in density; cause of some nearsightedness as cataract progresses
  • Cortical: Located in anterior, posterior or equatorial cortex; cause glare associated with bright lights
  • Posterior subscapular: Lies in front of the posterior capsule. Effect on vision can be significant, and often worse with bright lights
  • Mixed cataract: More than one type can occur in same eye

 

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Etiology:

Age-Related - most common cause

Systemic diseases

  • Diabetes
  • Hypertriglyceridemia
  • Renal disorders
  • Other metabolic disorders (hypocalcemia, Wilson disease, myotonic dystrophy etc.)
  • Atopic dermatitis
  • Down syndrome and other chromosomal abnormalities

Ocular disease

  • Ocular tumours
  • Pathologic myopia
  • Uveitis/iritis
  • Retinal detachment
  • Ocular surgery
  • Acute angle closure glaucoma

Environmental factors

  • Ultraviolet light
  • Radiation
  • Smoking
  • Trauma

Medications

  • Chronic oral corticosteroid use and possibly prolonged administration of high doses of inhaled corticosteroids
  • Amiodarone
  • Allopurinol
  • Phenothiazines

 

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Epidemiology:
  • From an estimated >30 million blind people worldwide, ~50% is due to cataract
  • Senile catracts represent ~90% of this condition

In Canada

  • More than 2.5 million individuals have cataracts, with an anticipated rise to 5 million in 25 years
  • By 2031, almost one-quarter of Canadians over the age of 40 will have cataracts
  • Prevalence is directly proportional to age
  • Percentage according to the age is estimated to be:
    • Approx. 2.5% = 40-49 years
    • Approx. 25% = 65-69 years
    • Approx. 70% = 80 years or more

 

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Pathophysiology:
  • Lens of the eye is composed of specialized stratified epithelial cells, with high cytoplasmic protein content arranged in a highly complex manner, these proteins provide the transparency to the lens
  • The lens is incapable of shedding nonviable cells making it susceptible to degenerative effects of aging
  • New cortical layers continuously add in a concentric manner and press and harden the central nucleus
  • As the lens ages, its weight increases and accommodation decreases
  • The epithelial cells accumulates and leads to loss of transparency
  • With aging the rate of transport of water, nutrients and antioxidants to the lens decrease which potentiates the oxidative processes in cataractogenesis
  • Photo-oxidative insult, potentiated by toxic or sensitizing substances, also play a role in the development of opacities

 

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Clinical Presentation:
  • History of painless progressive functional impairment in vision
  • Cataract formation is usually bilateral but can be asymmetric
  • Decreased visual acuity
  • Difficulty in driving, reading road signs and reading fine prints
  • Excessive glare or decreased vision with bright lights

 

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Investigation and Workup:

History: Should include duration of visual complaints, patient's ability to meet his/her visual needs and the extent of effect of the deficits; on the daily activities of life.

Inquire about:

  • Location of vision loss (central vs. peripheral)
  • Progressive loss of vision
  • Associated pain (sharp or dull)

Physical exam:

Decrease in visual acuity is directly proportional to the cataract density, the examination should include:

  • Assessment of visual acuity
  • Direct and indirect ophthalmoscopy: To rule out retinal disease
  • Slit-lamp examination: Visualization of lens opacity
  • Tonometry: To rule out increased intraocular pressure

Laboratory:

Rarely done, but may be necessary to rule out co-existing diseases.

  • CBC
  • Blood sugar
  • Electrolytes

Preoperative work up:

  • PT
  • APTT
  • ECG
  • Measurements for intraocular lens implantation

Imaging:

  • Ultrasound: Used to rule out posterior segment disease (e.g. ocular tumours or retinal detachment), if the cataract is too dense for direct visualisation of back of the eye

 

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Treatment Goals:
  • Maintain eye comfort
  • Promote early visual rehabilitation
  • Improve independence and quality of life

 

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Therapeutic Choices:

General considerations:

  • Lens removal in cataract patients:
    • Usually recommended when vision change is affecting the patient's activities
    • Surgery is usually done one eye at a time
  • Cataract surgery is usually done under local anaesthesia. Sometimes only topical drops required
  • Intraocular lens (IOL) implants are inserted at the time of cataract extraction
  • If IOL is not implanted then the patient is prescribed 'strong' glasses or contact lenses to correct refractive error

 

Surgical Options:

1) Intracapsular cataract extraction (ICCE)

Rarely used anymore, involves extraction of the entire lens including the lens capsule.

2) Extracapsular cataract extraction (ECCE)

Removal of the lens nucleus through an opening in the anterior capsule, with retention of the integrity of the posterior capsule

3) Manual Small Incision Cataract Surgery (MSICS)

A form of ECCE which uses a smaller incision (6-8 mm) and a scleral tunnel that is self-sealing. Results in significantly less astigmatic error.

 

4) Phacoemulsification:

Lens fragmentation through ultrasound and then aspirated, most common procedure for cataract removal

 

Lens Replacement:

After the removal of the lens, the patient is referred to as Aphakic (without lens). The lens must be replaced in order to focus light on retina for patient to see clearly.

There are three lens replacement options:

  • Aphakic eyeglasses: Effective but heavy, peripheral vision limited
  • Contact lenses: Provide almost normal vision, but needs to be removed occasionally so eyeglasses are still required
  • Intraocular lens implants (IOL): A regular approach during cataract surgery, there are certain condition like diabetic retinopathy, uveitis, chronic iritis, neovascular glaucoma, retinal detachment, in which implantation is contraindicated

 

Toxic Anterior Segment Syndrome (TASS):

A non-infectious inflammation caused by a toxic agent after uneventful surgery, and is a complication of anterior chamber surgery.

Note: There are many potential complications of cataract surgery, some of which can be intraoperative, early and late postoperative.

 

Femtosecond Laser:

The newest option where laser therapy is adopted for cataract removal, with fewer complications when compared with the conventional surgeries.

It can be used for wounds, opening of the lens and for the segmentation of cataract; in conjunction with phacoemulsification to remove the lens pieces.

 

MEDICATIONS:

Local Anesthetic, (ophthalmic)

  • Proparacaine
  • Tetracaine

Mechanisms:

  • Prevents initiation and transmission of impulse at the nerve cell membrane by inhibiting Na ion channels and stabilizing neuronal cell membranes

Dose:

Proparacaine

Ophthalmic surgery

  • 1 gtt of 0.5% solution in eye every 5-10 mins for 5-7 doses

Tonometry, gonioscopy, suture removal

  • 1-2 gtt of 0.5% solution in eye just prior to procedure

Tetracaine

Anaesthesia of the eye

  • Short-term: 1-2 gtt of 0.5% solution in eye pre-procedure
  • Prolonged: 1-2 gtt of 0.5% solution in eye every 5-10 mins for 3-5 doses

 

Adrenergic, vasopressors, (ophthalmic)

  • Phenylephrine

Mechanisms:

Stimulates alpha adrenergic receptors with weak beta-adrenergic activity, producing

  • Vasoconstriction of the arterioles of the conjunctiva
  • Activates the dilator muscle of the pupil to cause contraction

Dose:

Phenylephrine

Ocular procedures

  • 1-2 gtt of 2.5% or 10% solution and may administer after 10-60 mins as required

 

Mydriatic, cycloplegic and anticholinergic

  • Tropicamide

Mechanisms:

  • Prevents the sphincter muscle of the iris and the muscle of the ciliary body from responding to cholinergic stimulation

Dose:

Tropicamide

  • 1-2 gtt of 0.5% solution 15 mins prior to examination; may be repeated every 30 mins or as needed

 

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Clinical Trials:
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Pipeline Agents:
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Pharmacist Resources:

Encourage

Until the patient decide to have surgery, advise strategies that might help decrease cataract symptoms:

  • Use of eyeglasses or contact lenses with the most accurate prescription possible
  • Use a magnifying glass to read, if needed
  • Improve the lighting in home to comfortable level (as required)
  • Use of sunglasses with UVA and UVB protection in bright light or a broad-brimmed hat to reduce glare
  • Limit night driving

Patient should have postsurgical arrangement of extra help at home due to possibility of:

  • Restricted activity (such as, bending over and heavy lifting)
  • Vision changes (such as blurred vision and discomfort with bright light)

Drugs

American College of Chest Physicians (ACCP) recommend that

  • Patients who are receiving aspirin, may continue to receive aspirin at the time of the cataract procedure
  • Preoperative evaluation: Cautious about use of alpha-1-antagonists (commonly used for prostate disease and urological conditions), because alpha-1-antagonists have association with intraoperative floppy iris syndrome (IFIS), which can significantly increase risk of intraoperative complications
  • Patients who are receiving warfarin, may continue to receive warfarin at the time of the cataract procedure unless patient is at risk of suprachoroidal hemorrhage

Unlabelled/Alternate uses of medications

  • N/A

Counselling

  • Ensure patient is well informed about disease, as well as pre and postoperative medications
  • The procedure is usually brief, with patients discharged same day
  • Advise urgent medical assessment if patient reports any acute change in condition, especially pain

Alerts

  • Small fraction of cataracts can give rise to secondary glaucoma
  • Patient should contact doctor, if there is post-operative severe pain
  • Patient should not drive or operate mechanical equipment for at least 24 hours after surgery
  • Infection or serious bleeding may develop in the post-surgical eye, which can lead to a loss of vision
  • Highly myopic eyes are at high risk for retinal detachment after cataract surgery

Tips

Post-surgical:

  • Advise patient to wear glasses or eye shield at all times to protect eye from injury for minimum 1-2 weeks or as recommended by opthalmologist
  • Protect eye when showering, bathing or washing hair/face for approx. one week
  • Wash hands before touching the operative eye
  • Instruct patient and the family members about proper installation of eye drops and ointment
  • Patient to notify of any post-discharge medication changes
  • Avoid lying on the effected side on the night after surgery
  • Avoid bending over (example when putting shoes on)
  • Do not rub operated eye
  • Avoid straining, including with bowel movements

Expected outcome

  • Cataract surgery is a low risk procedure
  • Usually in patients without preexisting ocular comorbidity, postoperative visual acuity of 20/40 or better is expected
  • Posterior capsule opacification may occur in ~20% of patients; successfully treated with YAG (Yttrium Aluminum Garnet) laser capsulotomy- a Painless procedure from which patient can resume normal activities immediately
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References:

Core Resources:

  • American College of Eye Surgeons - Guidelines for cataract practice, 2001
  • Bellan L, Ahmed IIK, MacInnis B et al. Canadian Ophthalmological Society evidence-based clinical practice guidelines for cataract surgery in the adult eye. Can J Ophthalmol 2008;43:S7-57
  • Buhrmann R et al. Foundations for a Canadian Vision Health Strategy: Towards Preventing Avoidable Blindness and Promoting Vision Health prepared for the National Coalition for Vision Health. 2007
  • Compendium of Pharmaceuticals and Specialties (CPS). Canadian Pharmacist association. Toronto: Webcom Inc. 2012
  • Day RA, Paul P, Williams B, et al (eds). Brunner & Suddarth's Textbook of Canadian Medical-Surgical Nursing. 2nd ed. Philadelphia: Lippincott Williams and Wilkins; 2010
  • Foster C, Mistry NF, Peddi PF, Sharma S, eds. The Washington Manual of Medical Therapeutics. 33rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010
  • Gray J, ed. Therapeutic Choices. Canadian Pharmacists Association. 6th ed. Toronto: Webcom Inc. 2011
  • Longo D, Fauci A, Kasper D, et al (eds). Harrison's Principles of Internal Medicine. 18th ed. New York: McGraw-Hill; 2011
  • McPhee SJ, Papadakis MA, eds. Current Medical Diagnosis & Treatment. 49th ed. New York: McGraw-Hill; 2010
  • Pagana KD, Pagana TJ eds. Mosby's Diagnostic and Laboratory Test Reference. 9th ed. St. Louis: Elsevier-Mosby; 2009
  • Skidmore-Roth L. ed. Mosby's drug guide for nurses. 9th ed. St. Louis: Elsevier-Mosby; 2011
  • Skidmore-Roth L, ed. Mosby's nursing drug reference. 24th ed. St. Louis: Elsevier-Mosby; 2011

 

Online Pharmacological Resources:

  • e-therapeutics
  • Lexicomp
  • RxList
  • Epocrates Online

 

Journals/Clinical Trials:

  • Javitt JC, Wang F, West SK. Blindness Due to Cataract: Epidemiology and Prevention Ann Rev Public Health 1996; 17: 159-177

 

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Reviewers

EXPERT REVIEWER:
Garfield Miller, MD, FRCSC, Assistant Professor of Ophthalmology, University of Ottawa, The Ottawa Eye Institute, The Ottawa Hospital, Ottawa, ON Canada
.......................................... PHARMACY REVIEWER:
Sarah Pooler, B.Sc. Phm., R.Ph., Drug Information Pharmacist, Drug Information and Research Centre, Ontario Pharmacists Association, Toronto, ON Canada

 
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