Biometric Accuracy in High
Hypermetropes and Myopes
Mangat S, Kumar B V, Prasad S
Arrowe Park Hospital,
Wirral University Hospital NHS Trust
No 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
Results
Axial length < 22mm
Axial length >26mm
Number of Patients
632
245
Number of Operations
764
297
Data Available
585
225
Mean Age of Patient
76.3
68.5
Age Range
37-95
13-93
Mean 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
Axial Length <22mm
Percentage of Patients
50
40
30
20
10
0
<-5
--4
-3
-2
-1
1
2
3
Deviation From Predicted Post-Operative Refraction
4
Axial Length>26mm
Percentage of Patients
50
40
30
20
10
0
-5 -4 -3 -2 -1 1 2 3 4 5 >5
Deviation from predicted postoperative refraction
Percentage of Patients
Axial Length 22-26mm
50
45
40
35
30
25
20
15
10
5
0
-5
-4
-3
-2
-1
1
2
3
Deviation from predicted postoperative refraction
4
Main IOL Models Inserted
IOL Mode
(%)
Axial Length
<22mm
Axial Length 2226mm
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.