Cataract

Overview

Eye Cells

Video 5.1: Opacification of the lens

Structure and function of the lens

  • The natural lens that is present inside the eye.
  • Consists of:
    • A capsule: a transparent thin membrane
    • Of a transparent gel comprised of enucleated cells arranged in concentric layers.
  • Important function in accommodation
    • It is possible to modify its ray of curvature
    • Role in focusing of light rays on the retina

Cataract – Definition

  • Opacification of the lens. (1)
  • It can affect the totality of the lens, the anterior capsule, the posterior capsule and the lens nucleus. 

Epidemiology

  • Age-related cataract, the leading cause of blindness world-wide:
    • 48% of cases of blindness
    • affects 18 million persons (2)
    • a high priority disease according to the WHO: cataract not treated surgically accounts for 33% of cases of loss of visual acuity. (3)
  • A frequent disorder in older persons:
    • 20% of the French population starting at age 65 years,  
      • > 35% starting from 75 years
      • > 60% starting from age 85 years. (4)
  • Is on the increase because of increased life expectancy. (3)

Risk factors

  • Age: the major risk factor:  Age-related cataract
  • Ocular injury: Traumatic cataract (1)
    • Time of occurrence is variable: a few days to a few years
  • Certain medical or surgical treatments: Iatrogenic cataract (5)
    • Corticosteroids
    • Placement of intraocular implants (glaucoma, severe ametropia), vitrectomy, etc.
    • Exposure to X-rays (radiotherapy)
  • Secondary to another disease:
    • Diabetes (6), myopia, uveitis, glaucoma, etc.(1)
  • Congenital cataract
    • < 8 births per 100,000         
    • Heredity, intra-uterine infection (rubella), etc.
  • Other risk factors:
    • Smoking, alcohol abuse, prolonged exposure to ultraviolet radiation (1)

Epidémiologie

  • Cataracte liée à l'âge, première cause de cécité dans le monde:
    • 48% des cécités
    • touche 18 millions de personnes (2)
    • maladie prioritaire pour l'OMS : la cataracte non opérée représente 33% des déficiences visuelles. (3)
  • Affection fréquente chez les séniors:
    • 20 % de la population française à partir de l’âge de 65 ans,
      • > 35 % à partir de l’âge de 75 ans
      • > 60 % à partir de l’âge de 85 ans. (4)
  • En augmentation en raison de l’allongement de l’espérance de vie. (3)

Facteurs de risques

  • Age: le facteur de risque majeur : Cataracte liée à l'âge
  • Traumatismes oculaires : Cataracte traumatique (1)
    • Délai de survenue variable: quelques jours à quelques années
  • Certains traitements médicaux ou chirurgicaux : Cataracte iatrogène (5)
    • Corticoïdes
    • Pose d’implants intraoculaires (glaucome, fortes amétropies), vitrectomies, etc...
    • Exposition aux rayons X (radiothérapie)
  • Secondaire à une autre maladie:
    • Diabète (6), myopie, uvéite, glaucome...(1)
  • Cataracte congénitale
    • < 8 naissances sur 100 000                  
    • Hérédité, infection intra-utérine (rubéole)....
  • Autres facteurs de risques:
    • Tabagisme, consommation d’alcool, exposition prolongée aux rayons ultraviolets (1)

 

Clinical Presentation

Video 5.2: Cataract – visual symptoms​

Symptoms

  • Often affects both eyes, but in different degrees.
  • Depends on location in the lens:
    • Blurred vision with sensation of a veil in front of the eyes.
    • Glare, especially bothersome for night-time driving or for major sunlight.
    • Altered perception of colours
    • Double vision in the eye (monocular diplopia, is rarer).
    • At a later stage, progressive and painless decreased visual acuity. (1)

Progression

  • Progression to increasing opacification of the lens
  • The progression generally slow and progressive over several years.
  • In absence of treatment:
    • Deterioration of visual acuity, after 2 years in 60 to 70% of patients. (4)
    • Faster progression in persons:
      • With cataract in the posterior capsule of the lens,
      • In patients with insulin-dependent diabetes. (4)
    • Can result in blindness when the lens is totally opaque.
    • In rare cases, can be complicated by acute glaucoma with sudden increase in size of the lens (1)
  • In the industrialised countries:
    • Good management with surgery
    • The most common surgical procedure: > 500,000 procedures performed per year in France (7)
  • Possibility of secondary cataracts (7)

Diagnostic

World Cells

Diagnostic approach

  • Diagnosis established by an ophthalmologist
  • A detailed interview on symptoms experienced and visual impairment.
  • Measurement of visual acuity.

Laboratory examinations

  • Slit lamp examination of the lens :
    • A rapid and painless examination
    • Can be performed after dilatation of pupils with an eye drop to facilitate investigation (1)
    • Enables:
      • To evaluate with precision if there is opacity of the lens
      • To determine location, characteristics and dimensions of this opacity.
      • To magnify the anterior part of the eye: anterior chamber, cornea, iris, pupil, anterior vitreous body and lens.
  • Ultrasound:
    • To determine the location and characteristics of the opacity
    • To evaluate the capsule surrounding the lens.
  • Biometry:
    • To determine the characteristics of implants used in cataract surgery to replace the natural lens.
  • Other tests:
    • Can be used to rule out all other eye disorders:
      • Measurement of intraocular pressure: glaucoma,  
      • Fundoscopy examination: involvement of the retina or of the optic nerve, etc.  
      • etc.

Treatment

Eye Cells

Therapeutic approach

  • The only curative treatment is surgery:
    • Removal of the cataract and replacing the lens with an intraocular implant in order to compensate for the refractory power of the lens. (1)
  • Indications:
    • Is not an emergency.
    • The surgical decision depends on:
      • The functional impairment experienced,
      • The visual acuity after correction (no threshold, but intervention generally proposed 4 to 5/10ths (5)),
      • Socio-occupational requirements,
      • Existence of other causes of decreased visual acuity,
      • The stage of development of the cataract.
  • Techniques (1):
    • Intra-capsular extraction (is practically no longer used)
      • Creating a large opening in the cornea,
      • Removing the totality of the lens with an instrument called a cryode.
      • Placement of an implant.
    • Extra-capsular cataract extraction (utility for a very dense cataract)
      • Removing solely the lens and the cortex of the lens with a spatula
      • Intraocular implant is inserted into the capsule left in place.
    • Phacoemulsification: the preferred technique

Video 5.3: Cataract – Treatment by phacoemulsification with a femtosecond laser ​

Phacoemulsification

  • Principle:
    • A small incision is made in the cornea
    • Fragmentation of the nucleus of the lens using an instrument that delivers ultrasound.
    • Suctioning of the fragments outside of the eye
    • Placement of an implant in the preserved capsule of the lens.
  • Advantages: 
    • Effective, safe, enables rapid recovery of vision because of a smaller incision than the other methods. (8)
  • Conduct:
    • Procedure performed under local anaesthesia in ambulatory practice
    • Duration of 15 minutes on average
    • Patient is prohibited from driving on the day after the procedure
    • Post-operative control the following day and then at a frequency specified by the eye surgeon.
  • Results
    • Generally very good:
      • Recovery of vision within 4 days in the majority of cases (8)
      • Over 90% of persons who undergo surgery recover visual acuity equal to or greater than 5/10ths without corrective lenses. (4)

Video 5.4: Secondary cataract – Opacification of the posterior capsule and treatment with capsulotomy

Secondary cataract: Opacification of the posterior capsule.

  • Opacification of the capsule of the lens which has been left in place during the procedure.
  • Recurrence of symptoms of cataract
  • Involves about 18% of patients 1 year after surgery and 38% after 9 years.
  • Usually occurs between 3 months and 4 years after the procedure.
  • Develops gradually.
  • Can be treated by a procedure using Nd laser: YAG, capsulotomy. (7)

Other potential complications (very rare)

  • Intraocular infection (endophtalmia), glaucoma, retinal detachment, displacement of the implant, formation of oedema in the macula.

References

Cells
  1. Porter RS, Kaplan JL. Chapter 66. Cataract. The Merck Manual of Diagnosis & Therapy, 19th Edition,  Merck Research Laboratories 2011, p. 709-712 .
  2. Organisation mondiale de la santé. Prévention de la cécité et des déficiences visuelles.  Maladies oculaires prioritaires. Cataracte.  http://www.who.int/blindness/causes/priority/fr/index1.html
  3. Organisation mondiale de la santé. Cécité et déficience visuelle. Aide-mémoire N°282  http://www.who.int/mediacentre/factsheets/fs282/fr/ . Août 2014
  4. ANAES. Evaluation du traitement chirurgical de la cataracte de l’adulte. Février 2000.
  5. Baudouin C, Félix D. Cataracte - Guide à l’usage des patients et de leur entourage. Bash 2008.
  6. Malecaze F. La chirurgie de la cataracte chez le diabétique. Journal français d’ophtalmologie 2003;26:525-7.  
  7. Affsaps, Haute Autorité de Santé. Mise au point sur les implants intraoculaires monofocaux utilisés dans le traitement chirurgical de la cataracte. Avril 2008.
  8. Ancel JM. Les progrès de la cataracte en 2008. E-mémoires de l’Académie Nationale de Chirurgie 2008;7:43-44.