Biometric Accuracy in High Hypermetropes and Myopes

Mangat S, Kumar B V, Prasad SArrowe Park Hospital,

Wirral University Hospital NHS TrustNo financial interests

Introduction

• Cataract surgery in patients with myopia and hypermetropia can be technically challenging .

• These challenges arise due to extremes of axial length which can lead to complications during biometry.

• This can lead to potential intra and postoperative complications particularly with postoperative surprises particularly anisometropia.

• Hence obtaining accurate biometry in these patients is essential to ensure that the cataract surgery is successful.

Methods

• Retrospective review of medisoft database was undertaken of cataract surgery carried out between Jan 2005 - September 2009

• Surgery was carried out by Consultants, Fellow and Registrars.

• Myopia is defined when patient has an axial length more than 26mm

• Hypermetropia is defined when patient has an axial length less than 22mm

• Preoperative refraction, biometry measurements , visual acuity pre and post cataract surgery were all documented.

• Deviation from - predicted postoperative outcome and - final best corrected visual acuity were recorded

ResultsAxial length < 22mm Axial length >26mm

Number of Patients 632 245Number of Operations 764 297Data Available 585 225Mean Age of Patient 76.3 68.5Age Range 37-95 13-93Mean Post Op Spherical Equivalent

-0.01+/-1.20 (SD) (95%CI +/- 0.11)

-0.70 +/-0.95(SD) (95% CI +/-0.12)

Mean Deviation From Predicted Refraction

-0.01+/- 0.90 (SD) (95% CI +/- 0.08)

-0.09+/- 1.34 (SD) (95% CI +/- 0.17)

Predicted Post Operative Refraction +/- 1 D of predicted

484 192

<-1D of predicted 54 20>1D of predicted 45 12

0

10

20

30

40

50

<-5 --4 -3 -2 -1 1 2 3 4

Perc

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ge o

f Pati

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Deviation From Predicted Post-Operative Refraction

Axial Length <22mm

-5 -4 -3 -2 -1 1 2 3 4 5 >505

101520253035404550

Axial Length>26mm

Deviation from predicted postoperative refraction

Perc

enta

ge o

f Pati

ents

-5 -4 -3 -2 -1 1 2 3 405

101520253035404550

Axial Length 22-26mm

Deviation from predicted postoperative refraction

Perc

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ge o

f Pati

ents

Main IOL Models InsertedIOL Mode

(%)Axial Length

<22mm Axial Length 22-

26mm Axial Length

>26mm B&L L161AO 50.95 47.88 48.55

B&L L161SE 30.13 27.99 26.97

Chiron soflex 2 14.67 21.2 19.5

B&L M160 1.74 1.83 1.24

Conclusions

• Postoperative refraction in the <22mm and >26mm groups was within +/-1D in 84% and 86 % respectively

• There was no statistically significant difference between the mean post operative spherical equivalent -0.01 (<22mm) and 0.70 (>26mm). Paired Student t Test >0.05

• There was no statistically significant difference between the mean deviation from predicted refraction -0.01 (<22mm) and -0.09 (>26mm). Paired student t Test >0.05

Conclusions

• 89.5% cases with Axial Lengths 22-26mm had a postoperative refraction of +/- 1D

• Some postoperative surprises were noted as a result of Biometry errors which was rectified later with further surgery.

• It may be wise to discuss this finding preoperatively when dealing with patients with extremes of axial length

Available Evidence

• Zuberbuhler et al state that 53.2% of patients were +/- 1D of predicted in those with axial lengths above 30mm

• Lyle et al studied 106 highly myopic eyes. Postoperative corrected visual acuity was 20/40 or better in 94% of eyes, and uncorrected visual acuity was 20/40 or better in 77% of eyes at 27 months in those with axial lengths >26mm

• Maclaren et al state 55% patients were +/- 1D of predcited in 76 eyes requiring IOLs between 30-35D

References

• 1. Zuberbuhler B, Seyedian M, Tuft S. Phacoemulsification in eyes with extreme axial myopia. J Cataract Refract Surg. 2009 Feb;35(2):335-40.

• 2. Lyle et al. Phacoemulsification with intraocular lens implantation in high myopia. J Cataract Refract Surg. 1996 Mar;22(2):238-42.

• 3. MacLaren RE et al. Biometry and formula accuracy with intraocular lenses used for cataract surgery in extreme hyperopia. Am J Ophthalmol. 2007 Jun;143(6):920-931.