ABSTRACT
AIM:To compare the corneal curvature and to investigate the agreement between three different keratometers.METHODS:In this prospective study,keratometry was performed using an IOL Master (IM),a Bausch &Lomb manual keratometer (Man) and TOPCON KR-8800autokeratometer (Top) on 252 eyes of patients recruited from camps for cataract surgery.The average keratometry values were recorded and compared.The agreements between the instruments were analyzed using the Bland-Altman statistical method.The main outcome measure was average keratometry values.RESULTS:1) IOL Master and Manual keratometer:the mean corneal power was 44.62± 1.52 D with the IOL Master and 44.60 ± 1.52 D with the Manual keratometer.The paired t-test demonstrated a statistically significant difference in the mean corneal power between the IOL Master and Manual keratometer (P=0.001).The 95％ LOAs of the two devices were-0.22 to 0.22 as shown in the Bland-Altman plot;2) IOL Master and autokeratometer:the mean corneal power was 44.62±1.52 D with the IOL Master and 44.46± 1.53 D with the autokeratometer.The paired t-test demonstrated a statistically significant difference in the mean corneal power between the IOL Master and autokeratometer (P＜ 0.0001).The 95％ LOAs of the two devices were-0.24 to 0.55 as shown in the Bland-Altman plot;3) Autokeratometer and Manual keratometer:the mean corneal power was 44.60±1.52 D with Manual keratometer and 44.46±1.53 D with the autokeratometer.The paired ttest demonstrated a statistically significant difference in the mean corneal power between the autokeratometer and Manual keratometer (P＜ 0.0001).The 95％ LOAs of the two devices were-0.30 to 0.57 as shown in the Bland-Altman plot.CONCLUSION:Keratometry data obtained with different instruments may not be interchangeable,a fact that has important implications for cataract surgeons with respect to both surgical planning and outcomes auditing.
ABSTRACT
PURPOSE: To compare the keratometry obtained from optical low-coherence reflectometry (Lenstar LS900®), autokeratometer (KR-8100®), and topography (Medmont E300®) in children. METHODS: A retrospective study was performed in 316 eyes of 160 subjects. Subjects were divided into 3 groups according to age. Group 1 was younger than 10 years, group 2 was older than 10 years and younger than 18 years, and group 3 was older than 18 years. Subjects were tested using the Lenstar LS900®, KR-8100®, and Medmont E300®. Comparisons were made for steep K, flat K, mean K, and astigmatism among three groups. Agreement among the 3 devices was examined using the Bland-Altman method. RESULTS: The keratometry measured by Medmont E300® was highest, followed by that of Lenstar LS900® and KR-8100® in all 3 groups. Almost all keratometry was significantly different among the 3 devices except for the flat K measured by LS900® and KR-8100® in all 3 groups and flat K measured by KR-8100® and Medmont E300® in Group 3 (p < 0.05). With regard to mean K, the agreement between Lenstar LS900® and KR-8100® was better than that between the other two pairs in both Groups 1 and 2, while agreement between Lenstar LS900® and Medmont E300® was better in Group 3. The agreement between KR-8100® and Medmont E300® was worse than that between the other two pairs in Groups 1 and 3, while the agreement between Lenstar LS900® and Medmont E300® was worse in Group 2. CONCLUSIONS: There were significant differences in keratometry among the 3 devices in all 3 groups. In children, Medmont E300® showed relatively less agreement compared with the other two devices. In adults, however, the agreement between 2 devices showed variable results. Consideration of the keratometry measurement from Lenstar LS900®, KR-8100®, and Medmont E300® might be helpful to estimate accurate corneal keratometry in children.
Subject(s)
Adult , Child , Humans , Astigmatism , Methods , Retrospective StudiesABSTRACT
PURPOSE: To investigate clinical availability of AL-Scan(TM) (Nidek, Gamagori, Japan) by comparing corneal refractive power with AL-Scan(TM), Autokeratometer(TM) (Topcon KR-1, Tokyo, Japan) and Pentacam(TM) (Oculus, Wetzlar, Germany) devices. METHODS: Seventy-one patients (142 eyes) who visited our hospital for refractive surgery were tested using AL-Scan(R), Autokeratometer and Pentacam(R) and corneal refractive power was compared among devices. RESULTS: When comparing measurements with AL-Scan(R), Autokeratometer and Pentacam(R), the mean corneal refractive power was 43.37 +/- 1.32 D (2.4 mm zone), 43.35 +/- 1.32 D (3.3 mm zone), 43.36 +/- 1.35 D, and 43.35 +/- 1.36 D respectively and showed no significant differences. Corneal refractive power had strongly positive linear correlation (p < 0.001) and Bland-Altman plots showed high degree of agreement among AL-Scan(R), Autokeratometer and Pentacam(R) devices. CONCLUSIONS: Because measuring ocular biometry with AL-Scan(R) including axial length, intraocular lens power calculation and topography simultaneously is possible, clinical use is convenient. Corneal refractive power was not different when compared with autokeratometer and Pentacam(R) devices, thus, AL-Scan(R) can be used in the clinical environment.
Subject(s)
Humans , Biometry , Lenses, Intraocular , Refractive Surgical ProceduresABSTRACT
PURPOSE: To comparatively analyze the repeatability and consistency between different methods of measuring corneal refraction and astigmatism in order to precisely determine the toric intraocular lens target. METHODS: The medical records of 254 eyes of 192 persons were retrospectively reviewed to compare the repeatability of corneal refraction measured with autokeratometer, IOL Master, and topography. The axis and the amount of the astigmatism were compared between these methods. The differences between the estimated spherical equivalents using measured corneal refractive values and the actual spherical equivalents after cataract surgery were compared to evaluate the expected astigmatic error of each measurement. RESULTS: The average corneal refraction was greater with topography than with IOL Master or autokeratometer. Astigmatism calculated with IOL Master was greater than that measured with topography or autokeratometer. The mean coefficient of variation for mean corneal refraction was 0.19% with autokeratometer, which was smaller than that with IOL Master or topography. In patients with more than 1.5D of astigmatism, there were no significant differences in the axis measured by each instrument. The expected spherical error in IOL calculation was smaller with the measured values from IOL Master and autokeratometer than were those with topography. CONCLUSIONS: The repeatability of measurements for corneal refraction and astigmatism was significantly higher using the autokeratometer and IOL Master, with the highest astigmatic value observed with the IOL master. The axis of astigmatism for each method was consistent in the patients with more than 1.5D of astigmatism.
Subject(s)
Humans , Astigmatism , Axis, Cervical Vertebra , Cataract , Eye , Lenses, Intraocular , Medical Records , Retrospective StudiesABSTRACT
PURPOSE: To compare the keratometry measurements by the handheld Nikon Retinomax K-plus2, the on-table Canon RK-5 autokeratometer, and the manual Topcon OM-4 keratometer and to evaluate the degree of agreement among the three instruments. METHODS: Adults (n=30) and children (n=40) presenting toa tertiary eye hospital clinic were examined by an optometrist. Topcon OM-4 keratometer, Nikon Retinomax and the on-table Canon RK-5 autokeratometer analyses were performed in order. The horizontal and vertical keratometry data were measured. The vector components of astigmatism, mean bias and agreement among the three types of measurements were evaluated. RESULTS: There were no significant differences among the three keratometers in horizontal or vertical keratometry or in central corneal astigmatism in both the adult and child groups (p-value>0.05). The keratometers which were estimated with Retinomax K-plus2 were highly correlated with those by on-table RK-5 autokeratometer (min. 0.89, max. 0.97) and Topcon OM-4 keratometer (min. 0.67, max. 0.94) in the adult group, while in the child group, the three instruments showed slightly decreased correlation (min. 0.45, max. 0.97 on RK-5, min. 0.36, max. 0.92 on OM-4), especially in the left eyes. CONCLUSIONS: The handheld Retinomax K-plus2 provided comparable data to that of the conventional on-table Topcon and manual keratometers. This instrument will beuseful in the clinic to measure keratometry in children or immobilized patients who have difficulty sitting during the examination.