The effect of head tilt on keratometric measurement using the IOLMaster.
OBJECTIVE
To investigate the effect of head tilt on keratometric measurement using the IOLMaster.


METHODS
Twenty-seven right eyes of 27 volunteers were examined using a manual keratometer (MK), automated keratometer (AK), and an IOLMaster. MK and AK measurements were performed in the upright head position, whereas IOLMaster measurements were performed in five different head positions (upright, 5° or 15° clockwise head tilt, and 5° or 15° counter-clockwise head tilt). The repeatability of IOLMaster was compared with MK and AK. The keratometric measurements (mean keratometric power, magnitude of astigmatism, and steep meridian) in different head positions were compared.


RESULTS
The IOLMaster showed good repeatability of keratometric measurement comparable to MK or AK. 15° and 5° clockwise head tilt resulted in 12.09 ± 9.51 (mean ± SD) (P<0.001 vs upright) and 5.51 ± 5.97 (mean ± SD) degrees (P<0.001) of clockwise rotation of steep meridian, respectively. 15° and 5° counter-clockwise head tilt resulted in 12.49 ± 7.07 (mean ± SD) (P<0.001) and 6.08 ± 5.09 (mean ± SD) degrees (P<0.001) of counter-clockwise rotation of steep meridian, respectively.


CONCLUSIONS
The patient's head tilt (5° or 15°, clockwise or counter-clockwise) significantly changed the steep meridian of astigmatism measured using IOLMaster and the steep meridian generally shifted to the direction of head tilt. The importance of maintaining the upright head posture during IOLMaster measurement is demonstrated.
Department of Ophthalmology, Dongguk University, Ilsan Hospital, Koyang, South Korea.
C Y
CY
Park
Department of Ophthalmology, Dongguk University, Ilsan Hospital, Koyang, South Korea.
J R
JR
Do
Department of Ophthalmology, Dongguk University, Ilsan Hospital, Koyang, South Korea.
S H
SH
Kim
Department of Medicine, Graduate School, Dongguk University, Seoul, South Korea.
C-Y
CY
Lim
Department of Ophthalmology and Visual Sciences, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY, USA.
R S
RS
Chuck
D000328:Adult; D001251:Astigmatism / Q000175:diagnosis*; D058452:Axial Length, Eye; D003315:Cornea / Q000473:pathology*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006257:Head / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D007368:Interferometry / Q000295:instrumentation; D008297:Male; D011187:Posture / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult