cataract and refractive surgery

CATARACT AND REFRACTIVE SURGERY

Ms. A. Bobart Hone2009

CATARACT

• The term CATARACT denotes any opacity of the crystalline lens whether it affects the visual acuity or not

Anatomy

• Newborn - 3.5mm antero-posteriorly and 5mm equatorially • Unique to the lens is continued growth throughout life • Adult - 5mm antero-posteriorly and 9 - 10mm equatorially-i.e.. top to bottom• With age the lens becomes larger, more compact and less elastic• The lens is a biconvex optical structure behind iris and in front of vitreous in

posterior chamber of the eye• It is avascular and not innervated• Encircled by ciliary processes from which the zonules (suspensory ligament)

radiate to the lens surface• Zonules hold the lens in place and mediate the accommodative movements of

the ciliary muscle, therefore altering the lens shape.• Outmost layer is an acellular capsule (basement membrane) that surrounds the

lens• Anteriorly and just under the anterior capsule is the lens epithelium• Inner body of lens composed of tightly packed highly organised lens fibres• Innermost layer called the nucleus• Outer layers cortex

Red reflex with pen torch

Nuclear cataract( N.B. Pseudoexfoliation)

Brunescent nuclear sclerosis

Cortical cataract and Posterior subcapsular cataract

Cortical Cataract

Cortical cataract- multiple white spokes

Aetiology of Cataract • Age related• Physical - Trauma (often unilateral)• Electric shock (anterior subcapsular)• Radiation• Systemic - Diabetes• Dermatological - Atopic dermatitis• CNS disorders - Neurofibromatosis II which is

one of the group of harmatomatous disorders called the PHACOMATOSES

• ‘Drug induced’ -Amiodarone and- also a cause of corneal verticillata

• Iatrogenic- Corticosteroids (posterior subcapsular)

Corneal verticillata

Secondary

• Associated with Retinitis Pigmentosa• Uveitis- intraocular inflammation• Glaucoma, Corneal graft, vitreoretinal and any intraocular

surgery• Congenital• Hereditary disorders• Maternal rubella• Systemic disease e.g. galactosemia• Myotonic Dystrophy • Chromosomal• Trisomy 13 (Patau’s syndrome)• Trisomy 18 (Edward’s syndrome)• Trisomy 21 (Down’s syndrome)

Symptoms of cataract

• Glare • Gradual loss of vision unless traumatic• Reduced near vision i.e. difficulty reading - seen in

posterior subcapsular type• Central lens opacities may decrease pinhole vision• Second sight - nuclear cataracts cause changes in

refractive index of lens so that they become more myopic and one may not need reading lasses

• (Normally when one ages one becomes more presbyopic, i.e. near-sighted requiring more plus lens)

Examination

• Pen torch- red reflex

• Ophthalmoscopy (direct)- red reflex vs. black opacities in pupil area

• Slit lamp examination distinguishes the cataract subtype.

Red reflex with pen torch and note the white cortical lens opacities

Treatment• Surgical treatment is the only definitive treatment to

remove a cataract

• Indications for and against surgery • The aim of cataract surgery which is for the most part an

elective procedure is visual rehabilitation • Reasons ‘AGAINST’ surgery• Anaesthetic risk e.g. if unsuitable for LA but GA risk high• Severe amblyopia already investigated and documented• Extensive age-related macular degeneration or other retinal

pathology• Total afferent pupillary defect

Other reasons for lens extraction • Clear lens extraction may be performed- i.e. no significant

cataract present but lens may need to be removed• Severe myopia

• Patients may elect to have this done at an early age rather than wait to have cataract develop therefore avoiding need for thick spectacles or contact lenses

• Dislocated lenses• Pseudoexfoliation- can sometimes have associated glaucoma and

systemic manifestations with this• Trauma• Systemic conditions

» Marfan’s- typically upward dislocation of lens» Homocysteinuria typically downward dislocation of lens» Weill-Marchesani» Sulphite-oxidase deficiency

Dislocated lens in Trauma

Downward dislocation of lens can be seen in homocysteinuria

Types of Anaesthesia

• Local- most common• Topical anaesthetic drops• Retrobulbar, peribulbar, sub-Tenon’s injections

of local anaesthetic

• General (e.g.)• Children• Handicapped• Parkinson’s disease• Nystagmus

Types of cataract surgery

• Intracapsular– Rarely done– Removal of lens and capsule– Anterior chamber intraocular lens used

• Extracapsular cataract extraction– Removal of lens but capsule left behind

Phacoemulsification• The most common type of extracapsular surgery today is :

Phacoemulsification- ultrasonic lens fragmentation with simultaneous aspiration of lens fragments – Sophisticated small incision type (approx. 2.7-3.5mm wound incision)– Faster visual recover with fewer complications– Suture not routinely place

• In Extracapsular surgery:

– The intraocular lens is inserted into the capsule either by injection or unfolding

– If posterior capsule significantly damaged during surgery or deemed to be unstable lens may be inserted in the sulcus- space between iris and anterior capsule or alternatively into the anterior chamber. The latter must occur in conjunction with a peripheral iridotomy

Intraocular lens

Other

• Can combine cataract surgery with:

– Glaucoma surgery– Corneal graft surgery– Other surgery

Post-operative care and visual rehabilitation

• Combined steroid and antibiotic eye drops to be tapered over 4 weeks

• See at 1 day, 2 weeks and 1 month post-operatively

• If have artificial lens (pseudophakic) will need reading glasses post-operatively as no accommodation

• If no lens in eye (aphakic) correct with spectacles or contact lens

• Thickening of posterior capsule i.e. an ‘after cataract’ treated with YAG laser

Posterior capsular thickening with YAG laser capsulotomy

Laser Eye Surgery • Excimer laser • Therapeutic- removal or superficial cornea in

recurrent erosions

• Refractive– LASIK or Laser assisted in situ keratomileusis – LASEK or Laser assisted epithelial keratomileusis – PRK OR ASA or Photorefractive keratectomy or Advanced

Surface Ablation

Refractive Surgery may be used to correct Myopia, Hyperopia and Astigmatism

VIDEO OF PHACOEMULSIFICATION