Acquired cataract
Age-related cataract
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Subcapsular ( Fig. 9.1 ): (a) anterior lies directly under the lens capsule, and (b) posterior lies just in front of the posterior capsule and appears black on retroillumination; the latter often has a more profound effect on vision than a comparable nuclear or cortical cataract, with glare and poor near vision.
Fig 9.1
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Nuclear: often associated with myopia due to an increase in the refractive index of the nucleus; when advanced, the nucleus appears brown ( Fig. 9.2 ).
Fig 9.2
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Cortical: starts as clefts and vacuoles between lens fibres ( Fig. 9.3 ) due to hydration of the cortex and evolves into wedge-shaped or radial spoke-like opacities ( Fig. 9.4 ).
Fig 9.3
Fig 9.4
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Christmas tree : polychromatic opacities ( Fig. 9.5 ).
Fig 9.5
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Cataract maturity: (a) immature (lens is partially opaque), (b) mature (lens is completely opaque), (c) hypermature (shrunken and wrinkled capsule; Fig. 9.6 ), and (d) Morgagnian cataract (inferior sinking of nucleus in a liquefied cortex; Fig. 9.7 ).
Fig 9.6
Fig 9.7
Cataract in systemic diseases
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Diabetes mellitus: hyperglycaemia leads to the overaccumulation of metabolic products in the lens, initially leading to fluctuating refraction and later to cataract, particularly accelerated age-related nuclear.
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Myotonic dystrophy: fine cortical iridescent opacities that evolve into a visually disabling stellate posterior subcapsular cataract ( Fig. 9.8 ).
Fig 9.8
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Atopic dermatitis: dense anterior subcapsular plaque is characteristic ( Fig. 9.9 ).
Fig 9.9
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NF2: cataract develops in approximately 60% of patients, often prior to the age of 30 years.
Causes of secondary cataract
A secondary (complicated) cataract develops as a result of other primary ocular disease such as the following:
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Chronic anterior uveitis: cataract may be caused both by inflammation and by the steroids; progresses more rapidly in the presence of posterior synechiae ( Fig. 9.10 ).
Fig 9.10
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Acute congestive angle closure: small, grey-white, anterior opacities within the pupillary area (glaukomflecken; Fig. 9.11 ).
Fig 9.11
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High (pathological) myopia: posterior subcapsular opacities and early onset nuclear sclerosis.
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Hereditary fundus dystrophies: retinitis pigmentosa, Leber congenital amaurosis, gyrate atrophy, and Stickler syndrome (see Chapter 15 ).
Causes of traumatic cataract
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Penetrating trauma.
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Blunt trauma may cause a characteristic flower-shaped opacity ( Fig. 9.12 ).
Fig 9.12
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Electric shock.
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Infrared radiation (e.g. occupational exposure).
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Ionizing radiation (e.g. for ocular tumours).
Management of age-related cataract
Preoperative considerations
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Indications for surgery: (a) visual improvement, (b) medical indications (e.g. phacomorphic glaucoma; see Chapter 10 ), and (c) to facilitate management of fundus disease (e.g. diabetic retinopathy).
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Systemic preoperative assessment: general medical history; investigations are not usually performed for routine local anaesthesia.
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Ophthalmic preoperative assessment: (a) past ophthalmic history, (b) visual acuity (VA), (c) cover testing, (d) pupillary responses, (e) slitlamp biomicroscopy, (f) ocular adnexa (e.g. chronic dacryocystitis), (f) red reflex quality, (g) fundus examination (US if poor view), and (h) refractive status (including postoperative result from an eye previously operated on).
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Biometry: facilitates calculation of the lens power for a planned refractive outcome by measuring corneal power (keratometry) and axial length (e.g. optical interferometry, US). Refractive outcome planning may need to take into account the refractive status of the fellow eye as well as the patient’s preferences and the effect of previous ocular surgery.
Intraocular lenses
The intraocular lens (IOL) is optimized for positioning within the intact capsular bag, although complicated surgery may necessitate alternatives such as placement within the ciliary sulcus or anterior chamber.
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Flexible IOLs: made of silicone, acrylic, or Collamer; can be rolled or folded for introduction into the eye through a small incision.
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Rigid IOLs: still occasionally used.
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Sharp/square-edged optics: associated with a lower rate of posterior capsular opacification (PCO) compared with round-edged optics.
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Ultraviolet filter: routine in modern IOLs to reduce energy incident on the retina; blue light filters are also available.
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Aspheric IOL optics: counteract spherical aberration.
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Heparin coating: reduces the attraction and adhesion of inflammatory cells, which may have particular application in eyes with uveitis.
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Multifocal, accommodative, and pseudo-accommodative IOLs: aim to provide clear vision over a range of focal distances.
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Toric IOLs: integral cylindrical refractive component to compensate for pre-existing corneal astigmatism.
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Adjustable IOLs: alteration of refractive power following implantation.
Anaesthesia
Most cataract surgery is performed under local anaesthesia (LA), sometimes with the aid of oral or intravenous sedation. General anaesthesia is sometimes used (e.g. for children and very anxious patients).
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Sub-Tenon periocular LA: cannula is introduced through an incision in the conjunctiva and Tenon capsule 5 mm from the limbus inferonasally; akinesia is variable.
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Peribulbar block: needle is introduced through the skin or conjunctiva; provides effective anaesthesia and akinesia.
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Topical anaesthesia: (drops or gel) can be augmented with intracameral preservative-free lidocaine; despite the absence of akinesia, most patients can cooperate adequately.
Phacoemulsification
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Definition: most cataract surgery is performed using phacoemulsification (‘phaco’) in which the nucleus is broken down within the eye using ultrasound ( Fig. 9.13 ).
