Comparison of the influence of cataract and pupil size on retinal nerve fibre layer thickness measurements with time-domain and spectral-domain optical coherence tomography.
BACKGROUND
To investigate and compare the effect of cataract and pupil size on retinal nerve fibre layer (RNFL) thickness measurements using spectral-domain optical coherence tomography (Cirrus OCT) and time-domain OCT (Stratus OCT).


METHODS
Prospective, hospital-based study.


METHODS
Twenty-five eyes from 25 normal subjects undergoing cataract surgery.


METHODS
Three retinal nerve fibre layer (RNFL) thickness measurements were taken before and after dilation, preoperatively and postoperatively, using Cirrus 200×200 Optic Disc Scan and Stratus Fast RNFL Scan.


METHODS
Linear regression, intraclass correlation coefficient (ICC) and coefficient of variation analysis.


RESULTS
Cataract removal caused significant increase in RNFL measurements in both modalities (Cirrus P<0.02; Stratus P<0.001). There was no significant difference in the increase in measurements between the two machines. Pupil dilation had variable and non-statistically significant effect in both (P>0.05). ICC showed excellent reproducibility with Cirrus OCT after mydriasis, preoperatively (ICC=0.78-0.90) and postoperatively (ICC=0.90-0.97), but poor reproducibility before mydriasis (P<0.75). Stratus OCT achieved excellent reproducibility after cataract removal both before (ICC=0.86-0.96) and after mydriasis (ICC=0.92-0.95), but poor reproducibility before cataract surgery (P<0.75).


CONCLUSIONS
Cataracts, not pupil size, cause significant underestimation of RNFL measurements in both Cirrus and Stratus OCT. The extent of influence exerted does not appear different between the two instruments. Reproducibility of each machine appears to be affected differently. Mydriasis is required to achieve excellent reproducibility with Cirrus OCT, and media clarity is required with Stratus OCT.
Department of Ophthalmology Clinical Research Unit, Tan Tock Seng Hospital, Singapore.
Clarissa Sm
CS
Cheng
Maricel G
MG
Natividad
Arul
A
Earnest
Vernon
V
Yong
Boon A
BA
Lim
Hon T
HT
Wong
Leonard W
LW
Yip
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002386:Cataract / Q000150:complications*; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D018918:Phacoemulsification; D011446:Prospective Studies; D011680:Pupil / Q000502:physiology*; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000295:instrumentation*; D014792:Visual Acuity / Q000502:physiology