Assessing & co-managing cataract: Prof Charles NJ McGhee This handout covers most of the PowerPoint slide details used in cataract lectures 1&2 and may be useful for notetaking during the lectures. Greater detail of key areas is provided in a separate Cataract Co-Management handout. Key considerations 1. Blindness from Cataract 2. Anatomy of the Human Crystalline Lens 3. Anatomy Anterior Segment 4. Simplified Diagrammatic Eye A. Sharing care in cataract Identifying Appropriately referring Pre-operative assessment Post operative management Unexpected complications B. Cataract aetiology o Congenital o Inherited o Age-related o Metabolic e.g. diabetes o Toxic e.g. steroids o Traumatic e.g. irradiation o Secondary e.g. ant. uveitis Aetiology: Congenital Cataracts Inherited no systemic abnormality Galactosaemia, Galactokinase deficiency, Neonatal hypocalcaemia Inherited systemic syndrome Lowe syndrome (oculocerebral), Down syndrome Intra-uterine infections Rubella, Varicella Zoster, Toxoplasmosis Aetiology: Causes of acquired cataracts Pre-senile cataracts Systemic diseases - Diabetes, myotonic dystrophy, atopic dermatitis Traumatic Direct trauma, irradiation, infra-red Toxic Corticosteroids, Chlorpromazine Secondary Chronic uveitis 1
Describing Cataracts by anatomical location Nuclear, cortical, anterior and posterior subcapsular The Auckland Cataract Study 1: Waiting Harbour Bridge Study (N=193) Mean age 77.2 years Mean wait 18.2+/-11.6 Mean BSCVA 6/36 Outcome Still waiting 49% Expedited Rx 4% Private Surgery 21% Deceased 12% Declined Surgery 12% Cataract - when to Refer Visual acuity Symptoms eg. glare Ocular disease Systemic disease Social factors Driving license NZ Cataract Prioritization Questionnaire Auckland Cataract Project 2: Demographics (N=500) Gender 62% Female Mean Age 74.9+/-9.8yrs BSCVA 6/48-1 European 85% Maori 7% Indian 3% Asian 2% Pacific Peoples 2% Auckland Cataract Project 2: Assessment General Health Hypertension 25% Cerebral vascular disease 12% Diabetes Melitus 11% Ischaemic Heart disease 10% Aspirin 42% Warfarin 6% 2
Auckland Cataract Study 2: Topographic Assessment Biometric Data (N=502) Sphere 0.00 +/- 3.1D Cylinder -1.2D (0-7.5D) Axial length 23.14 +/-1.03mm Orbscan Topography Round 34% Oval 10% Sym Bowtie 31% Asym Bowtie 10% A-T-R 39% Timing of Cataract Surgery see second handout Cataract Surgical procedures Historical - Couching Intra-capsular ICCE Extra-capsular includes ECCE and Phaco Intra-ocular lenses Sir Harold Ridley Invented intra-ocular lenses and performed the first successful Surgery in Moorfields Eye Hospital, London, in 1949 26. Biometry of the Eye The eye as an optical system Corneal dimensions Diameter: 10.6 x 11.75mm Pachymetry: 520 mm cent., 670 mm periph. Curvature: ant 7.8mm, post 6.5mm Ant Chamber: 3.15mm (2.6-4.4 mm) Lens Diameter 9-10mm Thickness 3-4mm Axial Length 24.2mm (22.9 26.4) Vitreous length 17.3mm Key considerations in calculating IOL power 1. Pre-operative Accurate axial length measurement Accurate central corneal curvature Effective IOL formula 3
2. Intra-operative Selection of appropriate IOL Surgical technique/placement 3. Post-Operative Periodic outcome analysis Keratometry: Key issues Routine calibration on spheres Perform before A-Scan Focus eyepiece for user up to 1.0D error! Clarity of mires Relate to refractive error / axial length Consider re-measurement > 46.0D or <41.0D > 1.0D between eyes prior refractive surgery Biometry: Ultrasound A-Scan echoes (Five principle echoes) Indications for re-measurement of axial length Less than 22mm or greater than 25mm Greater than 0.3mm between eyes Poor correlation with refraction Poor echo pattern Poor patient fixation/cooperation Presence of staphyloma AC Depth: Scheimpflug imaging - Measuring AC depth by Orbscan Assessing accuracy of Orbscan II Anterior Chamber Depth Auckland Cataract Study Biometry Subgroup of 426 eyes assessed ACD & AL by Tomey AL-2000 A-Scan ACD also measured by Orbscan II Results U sound 3.11+/- 0.48mm Orbscan 3.18+/- 0.46mm Correlation: R 2 = 0.199, P<0.001 Difference: Students t-test p=0.003 IOL Power calculation formulae 1967 Fyodorov physiological optics 1981 Binkhorst considered post-op ACD Sanders-Retzlaff-Kraff (SRK) formula Modified formula by regression analysis and Empiric tailoring via development of A-Constants 4
IOL power calculation formulae Obsolete formulae Fyodorov Binkhorst SRK Contemporary Formulae SRK II Hoffer Q (T) Holladay (T) SRK T (T) Factors influencing IOL power calculations Keratometry Average of three readings Error of 0.1mm produces 0.5D miscalculation Error of 1.00D - produces 1.0D miscalculation AC Depth Error of 0.1mm produces 0.1D difference in IOL NB AC is 0.06mm deeper for each 1.0D myopia Axial length Ultrasound Errors accuracy to 0.1mm - 0.1mm creates 0.25 0.3D difference - velocity of sound greater in cataract Importance of accurate biometry Inaccurate biometry is the biggest single source of cataract-related litigation in the USA. 20% of explanted posterior chamber IOLs are removed because the are the incorrect power Contemporary Phacoemulsification - Auckland Cataract Study 3: outcomes 488 consecutive cataract operations Surgeon preference for technique Mean BSCVA of 6/48 SphEq 0.49 +/- 1.03D 99.8% local anaesthesia (95% subtenons) 97.5% small incision phacoemulsification Phacoemulsification surgery outcomes Outcome: Mean BSCVA 6 / 7.5 (88% > 6/12) Mean SphEq 0.46+/-0.89D Complications: 4.9% capsular tears 3.7% cystoid macular oedema 0.2% endophthalmitis 1.5% of eyes red n BSCVA due to surgery 5
Auckland Cataract Project: Summary A predominantly elderly, female, population. Frequently with significant systemic illness and co-existing ocular diseases. Relatively advanced cataracts and poor BSCVA The majority (97.5%) underwent small incision, phacoemulsification, LA, day-case surgery. Almost 90% achieved 6/12, or better, post-operative BSCVA Approximately 5% sustained significant adverse intra-operative events. Overall 1.5% of eyes exhibited poorer post-operative BSCVA than pre-operative. CATARACT II: Sharing Care Sharing care in cataract Identifying Appropriately referring Pre-operative assessment Post operative management Unexpected complications Common complications Striate keratopathy Elevated IOP Aqueous leak Ant. Uveitis Loose sutures* Rare complications - Retinal detachment, Choroidal haemorrhage, Filtering bleb Post-operative management Usually 2-4 weeks topical medication Typically an antibiotic and a steroid e.g. g. Chloramphenicol QDS e.g g. Predforte QDS Or Betnesol N (betamethasone & neomycin) Occasionally NSAIDS e.g. ketorolac/diclofenac Postoperative unaided Vision Day one and day 7: Usually 6/6 to 6/18 If less than 6/12 unaided refract More than 1.5D residual error - consult Postoperative Corrected Visual Acuity Generally BSCVA around 6/7.5 If BSCVA <6/12, exclude causes of reduced vision: Cystoid macular oedema Posterior capsule opacity Age related macular degeneration Diabetic maculopathy 6
Postoperative refractive error Should discuss re-referral criteria with co-managing ophthalmologists However, generally contact ophthalmologist if: Greater than 1.50D from intended refraction Greater than 1.50D of induced astigmatism Wound appearance & aqueous leak Day 1 wound should well apposed, if anterior chamber shallow or IOP <10mmHg exclude wound leak: Check for phaco burn or wound retraction Perform fluorescein test Spontaneous leak or leak to gentle compression Check pupil is round Exclude iris prolapse If AC compromised refer Post-operative intraocular pressure Generally less than 24mmHg Less than 10mmHg consider leak Greater than 30mmHg or painful Consider acetazolamide Consider referral Corneal appearance day 1 Range of appearance related to cataract density, difficulty of case, nucleus density, phaco energy: Entirely clear Occasional effete endothelial cells Focal striae & oedema at wound Extensive striae & oedema Generally resolves - <0.5% develop PBK Postoperative pupil Should be round, up to mid-dilated, If distorted exclude: Iris prolapse, Vitreous to wound, Vitreous in anterior chamber, or IOL displacement Anterior chamber inflammation Day 1 Flare + Cells + to ++ If heavy flare or cells +++ consider endophthalmitis Day 28 Usually no activity 5% may have persisting low-grade inflammation 7
Postoperative IOL position IOL should be well centred Relative to capsular bag / rhexis Relative to pupil If > 1.0mm IOL displacement Consider haptic position Assess for vitreous in AC Discuss with ophthalmologist Fundal examination If BSCVA less than expected Assess macula Exclude retinal detachment Exclude vitreous/retinal haemorrhage Post-operative management: Day 28 review Symptoms Unaided VA Refraction Assess: Cornea Pupil Media IOL position IOP Dilated fundus Delayed complications Posterior capsular thickening 2-5% - Rx YAG laser Capsular phimosis Retinal detachment 1% Cataract Summary Points 1. Cataract surgery is the most common surgery in those over 65 years of age. 2. Worldwide cataract is the most common cause of blindness 3. In the developing world intra-capsular extraction techniques are most common. 4. In developed countries ECCE techniques are largely superceded by phaco-emulsification 5. Commonly senile in aetiology > 60 years 6. Consider trauma, diabetes, drugs < 60 years 7. Refer 6/12 or poorer VA (public) 8. Majority of subjects have CVS disease 9. Local anaesthetic day case management 10. Phacoemulsification with IOL 11. 1-2% risk of visual complications 12. Be aware of re-referral indications post-op Ophthalmology 2020 In 2020 world population 7.9 billion 90% of blind in developing world but 2/3 rd of blindness will be preventable 32 million cataract operations will be required per year 8