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AUTHORS'S PROFILE:DR. SHIVKUMAR CHANDRASHEKHARAN: M.S. ('93), M.S.University, Baroda; Fellow,Aravind Eye Care System. Presently faculty in Aravind Eye Hospital,Address: Aravind Eye Hospital & PGI, Triunelveli-627001, Tamilnadu;E-mail: aravind@tvl.aravind.org.

IOL Master Optical Biometry Vs Conventional UltrasoundBiometry in Intraocular Lens Power Calculations in High Myopic

Eyes

Dr. Shivkumar Chandra Shekharan, Dr. Neelam Pawar, Dr. Devendra Maheshwari,

Dr. R Ramakrishnan

(Presenting Author: Dr. Neelam Pawar)

The accurate calculation of intraocular lens(IOL) power is essential for attaining thedesired refractive outcomes after cataractsurgery. The most important factor affecting the

accuracy of biometry is the axial length.1 Theoverall accuracy depends on 3 factors:preoperative biometric data (axial length AL),anterior chamber depth (ACD), lens thickness,

mailto:aravind@tvl.aravind.orgmailto:aravind@tvl.aravind.org

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CATARA CT SESSION - IV 137

and keratometric index (K), IOL powercalculation formulas, IOL power quality controlby the manufacturer. Studies based onpreoperative and postoperative ultrasoundbiometry show that 54% of errors in predictedrefraction after IOL implantation can be

attributed to AL measurement errors, 8% tocorneal power measurement errors, 38% toincorrect estimation of postoperative ACD.2,3,6

Partial Coherence Interferometry (PCI) by IOLMaster is a fast, noncontact method to calculatelens implant power for cataract surgery. It hasbeen reported as a potentially more accurate

method than ultrasound biometry. The AL whenmeasured by applanation A-scan ultrasound,because of the indentation of the globe and off-axis measurement of the AL by the transducer,causes erroneous AL detection and an undesiredpostoperative refractive outcome. The ALmeasurement will be inaccurately shorter withcorneal indentation in highly myopic .

Materials and Methods

In a prospective randomised clinical study, 50high myopic patients undergoingphacoemulsification cataract surgery were

randomised to undergo biometry by either IOLMaster (25 patients) or the ultrasound (25patients) between October 2007 and January 2008

at Aravind Eye Hospital Tirunelveli.

Inclusion Criteria were: 1) Eyes with significantcataract and suitable for phacoemulsification andprimary implantation of posterior chamber

intraocular lens. 2) Spherical equivalent > -6 Dand or Axial Length > 26.0 mm. 3) Patientcoming for scheduled visits .

Exclusion Criteria: (1) Presence of retinaldetachment, proliferative diabetic retinopathy,(2) Previous intraocular or corneal surgery

(including refractive surgery), (3) Cornealopacities or irregularities: previous scarring,dystrophy, ectasia, (4) Corneal astigmatismgreater than 2 dioptres, (5) Inability to achievesecure 'in-the-bag' placement of the IOL (i.e. dueto posterior capsule rupture, vitreous loss, weakzonules, zonular rupture).

Preoperatively, Snellen visual acuity wasassessed and all patients underwent a non-cycloplegic refraction, keratometry measurementand axial length measurement. Patientunderwent dilated indirect ophthalmoscopy and

USG B scan was done in patients where mediaopacity was dense obscuring fundusvisualization. IOL MasterGroup (25 eyes) hadAL and K measurements with the IOLMaster.

Only data with a signal-to-noise (SNR) valuehigher than 2.1 were recorded. Ultrasound group(25 eyes) had AL measurements by applanation

ultrasound (Sonomed,) and K measurements byBausch and Lomb keratometer. AL

measurements were performed by oneexperienced ophthalmic personnel. The

intraocular lens power was based on the SRK/T

formula. All patients underwent uncomplicated

cataract surgery by phacoemulsification with inthe bag IOL implantation through a temporalclear corneal incision. The IOLs used in the study

were the 3-piece AcrySof (MA30BA, MA60BM,

MA60MA), 1-piece AcrySof (SA60AT, SN60AT),

and aspherical 1-piece AcrySof (SN60WF) andAurofoldable (Aurolab, Madurai) . A standard

postoperative topical antibiotic and antiinflammatory regime was administered . Patients

were examined at the following intervals: 1 dayafter surgery,1week after surgery, 4-5 weeks after

surgery. The primary outcome measure of the

study was post operative spherical

equivalent.The actual postoperative sphericalequivalent (SE) was recorded 4 weeks after

surgery.

Results

50 patients (20 females and 30 males), were

included in this study, of whom 25 patientsunderwent optical biometry and 25 patients had

biometry by applanation ultrasound . The mean

age of patients was 65.6 (SD 6.85) years (range of43-72years). The preoperative mean axial length

was 27.76 2.11 mm in the optical group (range of26.10-33.80 mm) and 26.84 1.27 mm in the

ultrasound group (range of 26.00-32.25 mm)(P

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Table 1

SE < 0.5D < 0.75 D

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CATARA CT SESSION - IV 139

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