1. Cataract Lecture for Medical Students By Prof. U. F. Ezepue

2. Introduction Definition Cataract is opacity of the crystalline lens –Clinically significant cataract is that, which by virtue of its density or location, has caused or can explain an observed visual impairment. Many types of cataract depending on the structure and aetiology –Senile (age related) cataract is epidemiologically the most important and significant, accounting for much of the world’s blindness today –Age related cataract accounts for > 65% of the blindness burden despite cataract blindness being completely reversible/curable –Age related cataract characterised by visual impairment that is gradual in onset Progressive Painless usually worse in bright light but tends to improve slightly in dim light occurs in persons 60 years and above.

3. Classification of Cataract Classification by location of the opacity within the lens Nuclear cataract –Results from excessive nuclear sclerosis and yellowing with the formation of central lens opacity Nucleus of the lens progressively becomes very opaque and brown –this is called brunescent nuclear cataract. Cortical cataract –Results from changes in ionic composition of the lens cortex Produce cataract by causing changes in lens fibres hydration producing cataract. Posterior subcapsular cataract –Heralded by the formation of granular and plaque-like opacities in the posterior subcapsular cortex

4. Classification of Cataract Classification by aetiology Traumatic –Penetrating injury, concussion, infrared irradiation, electric shock, ionizing radiation Metabolic –Diabetes, galactosaemia, mannosidosis, Fabry’s disease, Lowe’s (oculocelebrorenal) syndrome, Hypocalcaemia Toxic –Steroid, Chlorpromazine, miotics, Busulphan (myleran), Amiodarone, gold Secondary (Complicated) –Chronic anterior uveitis, hereditary retinal dystrophies, high myopia, glaukomflecken (following acute glaucoma) Maternal Infections –Rubella, Toxoplasmosis, cytomegalic inclusion disease Component of syndromes –Down’s, Werner’, and Rothmund’s syndromes Hereditary

5. Pathogenesis of Cataract Cataract results from Complex and Multifactorial interaction between different physiological processes It is physiologically normal that –With age the lens’ weight and thickness increases while its power of accommodation decreases This is by the formation of new concentric cortical layers, compressing the nucleus which becomes hardened: this is called nuclear sclerosis.

6. First Mechanism of Cataractogenesis Lens epithelium undergoes age related changes including –Decrease in epithelial cell density –Aberrant differentiation of lens fibres –Reduction in the rate at which water and water-soluble low-molecular weight metabolites can enter the cells of the nucleus through the epithelium and cortex Subsequent decrease in rate of transport of water, nutrients and antioxidants Products of oxidation accumulate in the lens (e.g. oxidized glutathione) Concentration of antioxidant vitamins and the enzyme superoxide dismutase decrease in the lens Consequence: - –Progressive oxidative damage to the lens, which is believed to lead to cataractogenesis.

7. Second Mechanism of Cataractogenesis Conversion of soluble low molecular weight cytoplasmic lens proteins to –Soluble high molecular weight aggregates –Insoluble phases –Insoluble membrane protein matrices These protein changes alter the refractive index of the lens, scatter light and reduce transparency

8. Cataractogenesis The role of nutrition, particularly glucose, trace minerals and vitamins are being investigated and has led to a profusion of several enzyme/vitamin-based products in the market advertised as being able to either prevent or slow the progression of cataract

9. Clinical Presentation Presenting complaints and history Decreased visual acuity is the commonest complaint. –The visual disturbance is progressive and painless, being worse in bright light –Depending on the location/type of the cataract, the visual impairment may worsen with near work There may be complaint of glare and monocular diplopia if the cataract splits the visual axis A myopic shift in the refraction with progression of cataract may also be noted Some complain of a white reflex in the pupil

10. Clinical Presentation The past medical history May reveal risk factors such as –Trauma –Intrauterine infection –Diabetes or other metabolic disorders Family history Cataract may have occurred in other members of the family in the hereditary variants

11. Findings at Physical Examination Visual acuity is impaired for both distance and near and the patient may be blind Ocular adnexia and intraocular structures when examined may reveal lesions that may point at –the cause, type and eventual visual prognosis If the swinging flashlight test reveals a Marcus Gunn pupil or RAPD, this indicates an optic nerve disease or extensive macular lesion: –visual prognosis guarded in such cases

12. Findings at Physical Examination Age-Related (Senile) Cataract Bilateral Congenital Cataract

13. Findings at Physical Examination Presence of long-standing ptosis from childhood may indicate a sensory amblyopia Ocular motility problems may indicate a strabismic amblyopia Presence of other explanations of the visual problem indicate that prognosis of good vision after surgery is guarded –Optic atrophy –Retinal degenerations –ARMD –Retinal detachment –Glaucoma, etc

14. Findings at Physical Examination Slit lamp examination would evaluate the lens opacity before and after dilatation checking for –Droplet nuclear cataracts –Posterior subcapsular cataracts –Exfoliation syndrome –Position of the lens and integrity of the zonules Cornea is also examined for –Thickness –Opacities –Guttata

15. Findings at Physical Examination Direct and indirect ophthalmoscopy may reveal optic nerve and posterior pole disorders such as –Macular oedema –Age-related macular degeneration –Retinal detachment Examination under mydriasis –Pre-tests the ability of pupil to dilate when mydriatics are exhibited –Allows a more thorough examination of the lens and ocular fundus

16. Associated Systemic Examination Findings –Systemic examination may reveal disorders associated with or coexisting with cataract that may affect surgical risks and results

17. Investigations Generally Investigations are aimed at Confirming visual significance of cataract and prognosticate Determining possible cause and co- morbidities Planning visual rehabilitation at surgery Determining suitability for surgery

18. Investigations To confirm visual significance of cataract and prognosticate –Light projection test –Ocular imaging studies B-scan Ultrasound CT Scan MRI OCT –Brightness acuity test –Contrast sensitivity test –Automated visual field test in patients with pre-existing glaucoma, optic nerve disease and retinal disease –In suspected macular disease, Maddox rod test, photostress recovery test, blue light entoptoscopy, Purkinje entoptic phenomenon, visual evoked response and electroretinography may be useful –Laser interferometry

19. Investigations To determine possible cause and co- morbidities –Fasting blood sugar –Urinalysis –etc

20. Investigations To plan visual rehabilitation at surgery –Refraction of both eyes: power of IOL to be implanted must be compatible with the error in the fellow eye to avoid postoperative anisometropia and other complications –Accurate biometry to determine power of IOL to be implanted. Biometry entails measurement of Axial length of the globe by A-Scan ultrasound Keratometry Determination of posterior chamber lens power and backup anterior chamber lens power.

21. Investigations To determine suitability for surgery –Assessment of corneal integrity, especially endothelial health by pachymetry and specular microscopy. These are able to predict postoperative corneal morbidities such as corneal oedema and corneal decompensation and allow surgeon weigh the risks of surgery, particularly decision to implant an IOL. –IOP measurement –FBC, BP, Renal function test, RVS (I and II), etc

22. Treatment Medical No proven medical remedy to clear, delay progression or prevent cataract is known Optical care Meticulous refraction at the early stages may be helpful and delay mandatory surgery Surgical Care Has evolved from the ancient couching through ECCE, ICCE, with aphakic spectacles and ECCE with IOL to phacoemulsification with foldable multifocal IOLs

23. Complications Of Cataract Of Surgery Of Visual/Optical Rehabilitation

24. Complications Of Cataract –Lens induced glaucoma and uveitis –Dislocation with corneal endothelial touch and decompensation –Hypermaturity –Etc

25. Complications Of Surgery –Intraoperative complications: Shallow/flat anterior chamber, capsule rupture, corneal oedema, suprachoroidal haemorrhage or effusion, expulsive choroidal haemorrhage, retained lens material, vitreous disruption and incarceration in the wound, iridodialysis, and retinal light toxicity

26. Complications Of Surgery –Immediate postoperative complications Flat or shallow anterior chamber due to wound leak, choroidal detachment, pupillary block, ciliary block, suprachoroidal haemorrhage, stromal and epithelial oedema, hypotony, vitreocorneal touch syndrome with persistent corneal oedema, delayed choroidal haemorrhage, Hyphaema, elevated IOP, cystoid macular oedema, retinal detachment, acute Endophthalmitis, uveitis-glaucoma-hyphaema (UGH) syndrome

27. Complications Of Surgery –Late postoperative complications Suture induced astigmatism, pupillary capture, corneal oedema, chronic uveitis and chronic endophthalmitis

28. Complications Of Visual/Optical Rehabilitation –Decentration Sunset syndrome Sunrise syndrome –Dislocation –Pseudophakic Bullous keratopathy –Wrong power of IOL used

29. Options for Prevention of Cataract Blindness Primary option –No proven intervention can prevent the occurrence of senile cataract. –However, cataract due to other causes could be prevented by meticulous, adequate and appropriate intervention. Diabetic cataract may be prevented by strict blood sugar control; Trauma is preventable and so is cataract due to it Limitation of exposure to radiant energy may help Issue of use of antioxidant vitamins has not been proven despite its popularity in the hands of alternative medicine practitioners

30. Options for Prevention of Cataract Blindness Secondary Option –Once cataract develops, its progress can not be altered by any proven intervention No proof that antioxidants are useful for this Tertiary option –This is the only proven option –Variably effective methods have been used to extend cataract services to communities around the world