Investigation of ocular biometry in 4- to 9-year-old Chinese children.

PURPOSE: To investigate the distribution and changes in ocular biometry in 4-to to 9-year-old Chinese children and to compare the differences between age and genders in these parameters. METHODS: This was a school-based cross-sectional study. A total of 1,528 Chinese children, aged 4-9 years, from one primary school and 12 kindergartens, were included in the study. Axial length, corneal curvature, anterior chamber depth, and corneal diameter were measured for each child. RESULTS: AL and anterior chamber depth gradually increased with age in both genders. No significant changes in corneal curvature or corneal diameter were detected at different ages in either genders group. The mean ALs of males and females were 22.94 ± 0.80 mm and 22.38 ± 0.79 mm, respectively. The mean corneal curvatures of males and females were 43.05 ± 1.37 D and 43.75 ± 1.48 D, respectively. The mean anterior chamber depth of males and females were 3.47 ± 0.24 mm and 3.38 ± 0.25 mm, respectively. The mean corneal diameter of males and females were 12.08 ± 0.43 mm and 11.94 ± 0.44 mm, respectively. Females had consistently shorter ALs, shorter anterior chamber depth, smaller corneal diameter, and steeper corneal curvatures than males at any age. CONCLUSIONS: Boys had larger dimensions than girls for all ocular parameters except corneal curvature (flatter). Boys and girls showed similar trends for all parameters. Axial length and anterior chamber depth increased from 4 to 9 years of age, whereas corneal diameter and curvature did not change with age in either genders.

Assessment of total corneal power after myopic corneal refractive surgery in Chinese eyes.

PURPOSE: To develop a new regression formula based on the Gaussian thick lens formula and to verify the accuracy of the regression formula. METHODS: In this prospective study, 207 eyes of 207 myopic subjects and 133 eyes of 67 postoperative subjects were included. For the 133 postoperative eyes, 127 eyes underwent laser-assisted in situ keratomileusis, and 6 eyes underwent photorefractive keratectomy. Subjective refraction and Pentacam HR were performed preoperatively and postoperatively, and IOLMaster was performed in the postoperative group. SimK, keratometry based on the Gaussian optic formula (KGOF), KCHM obtained using the clinical history method, and the regression formulas KRF1 and KRF2 were calculated. RESULTS: (1) A statistically significant difference (t = 155.164, P = 0.000) between SimK and KGOF of 1.24 ± 0.12 D was observed, and there was a good correlation between SimK and KGOF (r = 0.996, P = 0.000). The first regression formula (KRF1 = 0.351 + 1.021 × KGOF) was obtained using linear regression. (2) Statistically significant differences (t = 19.114, - 25.184, 4.702, and all P = 0.000) between SimK and KCHM, KGOF and KCHM and KRF1 and KCHM of 0.75 ± 0.45 D, 0.96 ± 0.44 D and 0.18 ± 0.43 D, respectively, were obtained. Good correlations between SimK and KCHM, KGOF and KCHM and KRF1 and KCHM (all r ≧ 0.977, all Ps = 0.000) were also observed. The regression formula (KRF2 = - 1.204 + 1.027 × KRF1) was obtained using linear regression. (3) Six methods were used for the prediction of IOL power in the postoperative group. The highest results were obtained from the Shammas formula (without preoperative data) combining Km (obtained by IOLMaster) followed by the KCHM and KRF2 combining Haigis formula. The third was obtained from the KCHM and KRF2 combining Hoffer Q formula; and the smallest was the Km combining Haigis formula. CONCLUSION: The IOL power predicted by KRF2 in eyes after myopic CRS may be accurate.

Corneal power measurement with a new aberrometer/corneal topographer in eyes after small incision lenticule extraction for myopia.

PURPOSE: To assess corneal power measurements obtained by the OPD SCAN III Topographer in eyes with prior myopic small incision lenticule extraction (SMILE) surgery. METHODS: Sixty untreated myopic eyes of sixty subjects and forty previous myopic SMILE surgery eyes of forty subjects were consecutively enrolled in the present study. Manifest refraction, OPD SCAN III and Pentacam HR were performed. Keratometric measurements assessed by OPD SCAN III-simulated keratometry, average pupil power and effective central corneal power (ECCP) were compared with mean keratometry (Km) obtained by Pentacam HR in the untreated group and the clinical history method (CHM) in the treated group. RESULTS: In the untreated group, no statistically significant differences were revealed between all corneal power measurements obtained with OPD SCAN III and Km. In the treated group, all the corneal power measurements were statistically different from the CHM except for the Haigis method and the Shammas method, while ECCP had a statistically but not clinically significant overestimation of 0.42 D with 95% limit of agreement (LOA) of - 0.81 D to 1.64 D. The three modified ECCP had better prediction performance with narrower 95% of LOA lying in (- 1.20, 1.20 D) (- 1.22, 1.23 D) and (- 0.90, 1.00 D), respectively. CONCLUSIONS: The ECCP provided with OPD SCAN III could be used as an alternative option for the CHM after specific modifications in eyes with previous myopic SMILE surgery when the preoperative data are unavailable considering the narrowest agreement between the modified ECCP and the CHM. Otherwise, caution must be raised considering the wide LOA.

Precision and agreement of higher order aberrations measured with ray tracing and Hartmann-Shack aberrometers.

BACKGROUND: To assess the precision and agreement of measurements of higher order aberrations (HOAs) obtained with a ray tracing aberrometer (iTrace) and a Hartmann-Shack aberrometer (Topcon KR-1 W). METHODS: Prospective evaluation of the diagnostic test. Data from the right eyes of 92 normal subjects obtained using the two devices were included in this study. Two observers performed 3 consecutive scans to determine the intraobserver repeatability and interobserver reproducibility. About one week later, one observer performed an additional 3 consecutive scans to obtain the intersession reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and intraclass correlation coefficient (ICC) were used to assess the precision, while Bland-Altman plots were performed to assess the agreement. RESULTS: For intraobserver repeatability of the ocular, corneal and internal HOAs, Topcon KR-1 W showed a 2.77Sw of 0.079 µm or less and ICCs of 0.761 or more; and iTrace showed a 2.77Sw of 0.105 µm or less and ICCs of 0.805 or more. The ICCs of the internal HOAs of interobserver reproducibility were less than 0.75 except for spherical aberration (SA) (0.862), and interobserver reproducibility of the counterpart showed similar but lower results. For the ocular, corneal and internal HOA measurements, statistically significant differences existed between the Topcon KR-1 W and iTrace (all P < 0.05). No significant differences were observed in the ocular SA and internal coma. CONCLUSIONS: The ray tracing and Hartmann-Shack method aberrometers provided excellent repeatability but less reliable reproducibility in the measurement of HOAs (except for SA). The two aberrometers should not be interchangeable in clinical application because of the significant differences in HOA measurements between them.

A Comparison between Scheimpflug imaging and optical coherence tomography in measuring corneal thickness.

PURPOSE: To assess the repeatability and reproducibility of 3 rotating Scheimpflug cameras, the Pentacam (Oculus, Wetzlar, Germany), Sirius (Costruzione Strumenti Oftalmici, Florence, Italy), and Galilei (Ziemer, Biel, Switzerland), and 1 Fourier-domain optical coherence tomography (FD-OCT) system, the RTvue-100 OCT (Optovue Inc., Fremont, CA), in measuring corneal thickness. DESIGN: Evaluation of diagnostic test. PARTICIPANTS: Sixty-six right eyes of 66 healthy volunteers, whose mean age ± standard deviation (SD) was 35.39±10.06 years (range, 18-55 years). METHODS: Corneal thickness measurements obtained by each system included central corneal thickness (CCT), thinnest corneal thickness (TCT), and midperipheral corneal thickness (MPCT), measured at superior, inferior, nasal, and temporal locations at a distance of 1 and 2.5 mm from the corneal apex. In the first session, 3 consecutive measurements were performed by the same operator to assess intraobserver repeatability and by a second operator to assess interobserver reproducibility. Measurements were repeated in the second session scheduled 1 day to 1 week later. The mean values obtained in the 2 sessions by the first operator were used to investigate the intersession reproducibility. MAIN OUTCOME MEASURES: Intraobserver repeatability and interobserver and intersession repeatability of corneal thickness measurements, as calculated by means of within-subject SD, test-retest repeatability, coefficient of variation (COV), and intraclass correlation coefficients. RESULTS: The precision of CCT, TCT, CT2 mm (midperipheral corneal thickness [MPCT] with a distance of 1 mm from the corneal apex), and CT5 mm (midperipheral corneal thickness [MPCT] with a distance of 2.5 mm from the corneal apex) measurements was high with all 4 systems. The COV was ≤1.16%, 0.94%, and 1.10% for repeatability, interobserver reproducibility, and intersession reproducibility, respectively. The 4 devices offered better interobserver reproducibility than intersession reproducibility for all measurements. The CTsuperior-5 mm (midperipheral corneal thickness [MPCT], measured at superior locations with a distance of 2.5 mm from the corneal apex) measurements showed the poorest repeatability and reproducibility. The Galilei revealed the best precision of CCT, TCT, and CT2 mm measurements. CONCLUSIONS: Both Scheimpflug imaging and FD-OCT offer highly repeatable and reproducible measurements of CCT and MPCT. The precision was lower in the midperipheral superior quadrant. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

The effect of cycloplegia on the lenstar and the IOLMaster biometry.

PURPOSE: To evaluate the effect of cycloplegia on ocular biometry measurements and intraocular lens (IOL) power calculation using the Lenstar LS900 (Haag-Streit AG, Koeniz, Switzerland) and the IOLMaster (Carl Zeiss Meditec AG, Jena, Germany) biometers and to assess the agreement between the devices. METHODS: Measurements were taken with the Lenstar and the IOLMaster on 43 healthy volunteers with a mean age of 22.1 ± 4.7 years (range, 18 to 37 years). Axial length (AL), anterior chamber depth (ACD), corneal curvature, and horizontal iris width (white-to-white [WTW]) measurements were performed with and without cycloplegia. The IOL powers were calculated using four formulas: Sanders-Retzlaff-Kraff/Theoretical, Holladay 1, Hoffer Q, and Haigis. RESULTS: Cycloplegia had no significant effect on AL or corneal curvature. However, ACD and WTW significantly increased postcycloplegia (Lenstar, 0.09 ± 0.06 mm and 0.10 ± 0.17 mm, respectively; IOLMaster, 0.06 ± 0.07 mm and 0.43 ± 0.35 mm, respectively; p <0.001). The Lenstar AL measurements were statistically but not clinically significantly longer than those of the IOLMaster (precycloplegia, 0.03 ± 0.03 mm; postcycloplegia, 0.02 ± 0.03 mm; p < 0.001). For ACD measurements, the 95% limits of agreement were -0.19 to 0.20 mm without cycloplegia and -0.11 to 0.17 mm with cycloplegia. The 95% limits of agreement for WTW measurements were -1.07 to 0.45 mm with cycloplegia. The only significantly different IOL power precycloplegia and postcycloplegia was with the Haigis formula and the Lenstar measurements: 15.12 ± 3.87 diopters and 15.26 ± 3.92 diopters (p < 0.01). CONCLUSIONS: Cycloplegia affected ACD and WTW but not AL or corneal curvature measurements. Generally, good agreement was found between the Lenstar and the IOLMaster, although not for WTW. Differences between these devices do not produce a clinically significant impact on IOL power.

[Assessments of total corneal power and intraocular lens power in post-LASIK eyes].

OBJECTIVE: To compare the different evaluations of corneal power in post-laser-assisted in situ keratomileusis (LASIK) eyes and assess the accuracy and differences of intraocular lens (IOL) power prediction with corneal powers through different calculation methods. METHODS: For this prospective study, 71 eyes of 39 candidates undergoing LASIK and 3 months later returning for reexamination were included. All subjects were divided into 2 groups according to the axial length: Group A (23.46 - 25.97 mm) 44 eyes, Group B (26.00 - 28.52 mm) 27 eyes. The ranges of spherical equivalents were -1.75 - -9.50 D with an average of (-4.82 ± 1.98) D. Subjective refraction and Pentacam Scheimpflug analyzer were performed at pre-operation and subjective refraction, IOLMaster and Galilei II dual Scheimpflug analyzer at over 3 months post-operation. The following values were obtained: SimK by Galilei II dual Scheimpflug analyzer, Kn calculated with Gaussion thick lens formula, Kray with ray tracing method, Kchm calculated with clinical history method and Km by IOLMaster. Repeated measures analysis of variance analyze the differences between SimK, Kn, Kray, Km and Kchm. Repeated measurement analysis of variance was employed to analyze the differences between SimK, Kn, Kray, Km combining intraocular lens power formula and Kchm combining intraocular lens power formula. Pearson's analysis was performed to analyze the correlations between SimK, Kn, Kray, Km and Kchm. Those combining with formulas for IOL power calculations were also analyzed. P < 0.05 indicated statistical significance. RESULTS: The values of SimK, Kn, Kray, Km and Kchm were (39.02 ± 1.8), (37.8 ± 1.51), (36.8 ± 1.84), (39.18 ± 1.75) and (38.55 ± 1.83) D respectively. The differences between SimK, Kn, Kray, Km and Kchm had statistical significances (P < 0.01). High correlations existed between SimK, Kn, Kray, Km and Kchm (r > 0.9, P < 0.01). In the same IOL formula, Kray had the highest IOL power value, Kn followed, Kchm the third, SimK and Km the smallest. Among the IOL formulas, Haigis-L and Haigis predicted the highest IOL power, HofferQ followed, Holladay the third and SRK/T the smallest. CONCLUSION: Kn/Kray combining with Haigis formula may be a new and effective method for predicting the IOL power in post-LASIK eyes.

Comparison of lens refractive parameters in myopic and hyperopic eyes of 6-12-year-old children.

Background/aims: To evaluate the influence of cycloplegia on lens refractive parameters in 6-12-year-old children with myopia and hyperopia for exploring the pathogenesis of myopia. Methods: One hundred eyes of 100 patients (50 boys) were included. In the myopic group, 50 subjects (25 boys and 25 right eyes) were enrolled with a mean age of 9.20 ± 1.69 years. IOLMaster 700 measurements were performed pre- and post-cycloplegia. The pictures were marked using semi-automatic software. The lens curvature and power were obtained using MATLAB image processing software. Paired and independent sample t-tests were used for data analysis. Statistical significance was set at P < 0.05. Results: Anterior and posterior lens curvature radius in myopic eyes were larger than those in hyperopic eyes, both pre- and post-cycloplegia (both P < 0.001). The refractive power in myopic eyes was lower than that in hyperopic eyes without cycloplegia, both pre- and post-cycloplegia (both P < 0.001). The changes in anterior lens curvature and refractive power between pre- and post-cycloplegia in hyperopic eyes were larger than those in myopic eyes (both P < 0.05). No significant difference was found in the change in posterior lens curvature and refractive power after cycloplegia in hyperopic and myopic eyes (P > 0.05). Conclusion: Anterior and posterior surfaces of the lens were flatter, and the refractive power was lower in the myopia group than in the hyperopia group. Myopic and hyperopic patients showed a tendency for lens flattening and refractive power decrease after cycloplegia. Hyperopic patients had more changes in anterior lens curvature and refractive power after cycloplegia.

A novel analysis of Scheimpflug total corneal refractive power following corneal cross-linking in mild to moderate keratoconus.

AIM: To detect an earlier improvement in mild to moderate keratoconus following corneal cross-linking (CXL) with total corneal refractive power (TCRP) using ray tracing method. METHODS: A total of 40 eyes of 30 consecutive patients who underwent CXL for progressive keratoconus were retrospectively enrolled. The following keratometric parameters provided by Pentacam HR, including maximum keratometry (Kmax), steepest keratometry (Ksteep), 3 mm zonal TCRP centered over corneal apex (TCRPapex,zone 3 mm), zonal mean keratometry and TCRP centered over corneal cone (Kmcone,zone and TCRPcone,zone 1, 2, 3 mm) were evaluated preoperatively and 1, 3, 6, and 12mo postoperatively. Groups 1 and 2 were defined based on Kmax at postoperative 1mo as improved (the initial improvement group) or worsen (the initial deterioration group) compared to the preoperative level. RESULTS: In the overall group, only keratometric parameters based on ray tracing method displayed significant improvement early at 3mo postoperatively, in which TCRPcone,zone 1 mm and 2 mm exhibited the largest flattening (0.57 D and 0.53 D, respectively). In Group 1, only Kmax, Kmcone,zone 2 mm and TCRPcone,zone 2 mm showed significant improvement initially at 1mo postoperatively, in which Kmax exhibited the largest improvement (1.05 D), followed by TCRPcone,zone 2 mm (0.82 D). In Group 2, only keratometric parameters based on ray tracing method and Kmcone,zone 3 mm showed slight but not significant improvement early at 3mo, in which TCRPcone,zone 3 mm displayed the most improvement (0.19 D), followed by TCRPcone,zone 2 mm (0.15 D). CONCLUSION: The findings indicate that a 2 mm zonal TCRP centered over Kmax could earlier detect keratometric improvement by CXL compared to other commonly used parameters in mild to moderate keratoconic eyes.

A Comparative Study of Total Corneal Power Using a Ray Tracing Method Obtained from 3 Different Scheimpflug Camera Devices.

PURPOSE: We sought to assess the agreement of ray-traced corneal power values by 3 Scheimpflug tomographers tp construct the corresponding arithmetic adjustment factor in comparison with an automated keratometer (IOLMaster) and a conventional Placido-based topographer (Allegro Topolyzer). DESIGN: Prospective reliability analysis. METHODS: A total of 74 eyes from 74 healthy subjects who underwent corneal power measurements using Pentacam, Sirius, Galilei, IOLMaster, and Allegro Topolyzer were included. Ray-traced corneal power values, such as total corneal refractive power (TCRP), mean pupil power (MPP), total corneal power (TCP), mean keratometry (Km), and simulated keratometry (SimK) were recorded respectively and analyzed using one-way analysis of variance (ANOVA) and Bland-Altman plots. RESULTS: Among the 3 ray-traced corneal power values, TCRP and MPP did not differ significantly (P = 0.81), whereas TCP presented a slightly significant larger value (P < 0.001). Compared to Km or SimK, corneal power measurements by the ray tracing method exhibited significantly lower values (P < 0.001). Bland-Altman plots disclosed that the 3 Scheimpflug tomographers showed similar 95% limits of agreement after arithmetic adjustment compared with Km (-0.40 to 0.40 D, -0.39 to 0.39 D, and -0.35 to 0.34 D) or SimK (-0.50 to 0.51 D, -0.43 to 0.42 D, and -0.46 to 0.46 D). CONCLUSIONS: Ray-traced corneal power values obtained using 3 Scheimpflug tomographers with default diameter settings were similar, indicating that they could be used interchangeably in daily clinical practice. The 3 Scheimpflug tomographers were satisfactory in agreement after arithmetical adjustment compared with conventional automated keratometer or Placido-based topographer.

Comprehensive evaluation of total corneal refractive power by ray tracing in predicting corneal power in eyes after small incision lenticule extraction.

PURPOSE: To assess the prediction accuracy of four variations of total corneal refractive power (TCRP) by the ray tracing method in determining corneal power in eyes after myopic small incision lenticule extraction (SMILE). METHODS: Forty eyes of forty patients who had undergone myopic SMILE were enrolled in this prospective study. Manifest refraction and Pentacam HR were performed preoperatively and three months or more postoperatively. Mean keratometry (Km), true net power (TNP), equivalent keratometry readings (EKR) and 4 subtypes of TCRP (pupil centered or apex centered within a ring or a zone)-TCRPpupil,ring, TCRPpupil,zone, TCRPapex,ring and TCRPapex,zone-were recorded and compared to the theoretical postoperative keratometry value using the clinical history method (CHM). RESULTS: The only keratometric values that showed no statistically significant differences from the CHM were 4.0 mm and 4.5 mm EKR, 6.0 mm TCRPpupil,zone and TCRPapex,zone. Pearson's correlation test revealed that 4.0 mm TCRPpupil,zone exhibited the highest correlation coefficient (r = 0.974) followed by TCRPapex,zone 4.0 mm (0.972) and EKR 4.5 mm (0.970). The 95% limits of agreement (LOA) of the 4.0 mm EKR and CHM, the 4.5 mm EKR and CHM, the 6.0 mm TCRPpupil,zone and CHM, the 6.0 mm TCRPapex,zone and CHM were (-1.27 to 1.22 D), (-1.04 to 0.98 D), (-1.39 to 1.08 D) and (-1.38 to 0.96 D), respectively, while the modified 4.0 mm TCRPpupil,zone (TCRPpuil,zone + 0.70 D) and TCRPapex,zone (TCRPapex,zone+0.70 D) yielded the narrowest 95% LOA of (-0.96 to 0.95 D) and (-0.96D, 1.05 D). CONCLUSIONS: Total corneal refractive power using the ray tracing method could predict corrected corneal power derived from the CHM in eyes following SMILE surgery after simple modification.

Evaluation of the Ocular Surface Disease Index Questionnaire as a Discriminative Test for Clinical Findings in Dry Eye Disease Patients.

Purpose: To investigate to what extent the OSDI can be utilized as a discriminative test for clinical findings. Methods: One thousand and ninety patients with dry eye disease (DED) were consecutively included and examined for osmolarity, tear film break-up time (TFBUT), ocular protection index (OPI), ocular surface staining (OSS), Schirmer I test (ST), meibum expressibility (ME), meibum quality (MQ), and diagnosis of meibomian gland dysfunction (MGD). Receiver-operating characteristic curve (ROC) analysis considering optimum balanced sensitivity and specificity (close to 50%) was used for assessment. Results: The present study on more than 1,000 patients indicates that the OSDI in the ROC curve analysis is a poor discriminator of pathological scores for TFBUT ≤ 5 (AUC = 0.553; p = .012) and ≤10 s (AUC = 0.608; p = .002), OSS ≥ 3 (AUC = 0.54; p = .043), ST ≤ 5 (AUC = 0.550; p = .032) and ≤10 mm/5 min (AUC = 0.544; p = .016), and ME ≥ 1 (AUC = 0.594; p = <0.001). Pathological scores for osmolarity >308 and >316 mOsm/L, OPI, OSS > 1, MQ, and MGD could not be discriminated by OSDI (p > .05). Conclusion: Cut-off values for the OSDI can be defined to discriminate pathological TFBUT (≤5 and ≤10), OSS (≥3), ST (≤5 and ≤10) and ME, however, the discriminability was low. Our comprehensive study emphasises the importance of taking both symptoms and signs into account in DED management.

Precision (repeatability and reproducibility) of ocular parameters obtained by the Tomey OA-2000 biometer compared to the IOLMaster in healthy eyes.

PURPOSE: To assess the precision (repeatability and reproducibility) of ocular parameters measured by the Tomey OA-2000 biometer, and to compare them with those measured by the IOLMaster. METHODS: In this prospective study, the right eyes of 108 healthy subjects were included. Three consecutive scans were obtained by 2 observers using the Tomey OA-2000, and in the same session one observer used the IOLMaster (version 5.4.4.0006) for the measurements. About 1 week later, 3 scans were obtained by one observer using the Tomey OA-2000. The axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), keratometer readings, pupil diameter (PD) and corneal diameter (CD) values measured by the Tomey OA-2000 and IOLMaster were analyzed. The coefficient of variation (CoV), intraclass correlation coefficient (ICC), within subject standard deviation (Sw) and 2.77Sw were calculated to assess the repeatability and reproducibility. The paired t test and Bland-Altman plots were used to analyze the differences and agreements of parameters measured by the two devices, respectively. RESULTS: Intraobserver repeatability, and interobserver and intersession reproducibility of the AL, CCT, ACD, LT, Kf, Ks, Km, PD and CD values measured by the Tomey OA-2000 biometer showed a CoV of less than 1% except that for PD, and an ICC of more than 0.97 except that for PD and CD. The AL, Kf, Ks, Km and CD values measured by the Tomey OA-2000 were 0.058 ± 0.094 mm, 0.088± 0.150 diopters (D), 0.163 ± 0.170 D, 0.127 ± 0.117 D and 0.171 ± 0.217 mm lower than those measured by the IOLMaster, respectively (all Ps < 0.05). However, the ACD values from the two devices were comparable (P = 0.169). The 95% linite of agreement (LoA) of the AL, ACD, CD and all keratometer readings were no more than 0.24 mm, 0.14 mm 0.60 mm and 0.5 D, respectively. CONCLUSION: Except for the PD and CD, the ocular parameters measured by the Tomey OA-2000 were highly repeatable and reproducible. Except for the CD value, there was good agreement of ocular parameters measured by the Tomey OA-2000 and the IOLMaster in healthy eyes.

The thickness and volume of the choroid, outer retinal layers and retinal pigment epithelium layer changes in patients with diabetic retinopathy.

AIM: To evaluate the thickness and volume changes of the choroidal, outer retinal layers (ORL) and retinal pigment epithelium (RPE) in patients with diabetic retinopathy (DR) using optical coherence tomography (OCT) and correlate them with visual acuity. METHODS: We carried out a retrospective observational case series. Consecutive DR patients were recruited for color fundus photography and OCT assessment. The RPE, ORL and choroidal thickness were measured. The correlation with the best-corrected visual acuity (BCVA) was also investigated. RESULTS: The study included 128 eyes, comprising 45 eyes of 25 diabetic macular edema (DME) patients, 34 eyes of 20 DR without DME (non-DME) patients, and 49 eyes of 25 age-matched normal individuals. The choroidal thickness in DR patients were decreased statistically significantly compared with the control group (P<0.05). The mean macular ORL thickness in DME (73.02±15.34 µm) and non-DME groups (76.35±7.32 µm) were decreased statistically significantly compared with the control group (80.20±5.85 µm; P=0.006, P=0.013, respectively). In both the non-DME and DME groups, the RPE thickness were decreased compared with the control group (P<0.05), except in the macular and central ring. The BCVA were significant interactions with the total inner retinal volume and macular RPE thickness in the DME group (r=0.115, P<0.001, r=-0.013, P=0.017, respectively). CONCLUSION: The choroid, ORL and RPE thickness are significantly decreased in DR patients compared with controls in different segments.

Choroidal Variations in Diabetic Macular Edema: Fluorescein Angiography and Optical Coherence Tomography.

PURPOSES: To (i) evaluate variations in choroidal thickness (CT) and choroidal volume (CV) in diabetic macular edema (DME), as demonstrated by fluorescein angiography (FA) and enhanced depth-imaging (EDI) optical coherence tomography (OCT) (EDI-OCT) and (ii) correlate these variations with visual acuity. METHODS: This study was a retrospective observational case series of patients with diabetic retinopathy (DR) and DME. The study groups comprised 77 DR patients (n = 87), all of whom underwent color fundus photography, FA, and OCT on the same day. The control group comprised 25 age-matched healthy individuals (n = 50 eyes). CT was measured by manual segmentation (EDI-OCT built-in automated retinal segmentation software). Variations in CT in DME patterns were analyzed. RESULTS: We studied a total of 87 eyes from patients with DR, including 50 eyes from 25 patients with DME (DME group) and 37 eyes from 22 patients without DME (non-DME group). For DME-group patients, mean subfoveal choroidal thickness (SFCT) and total CV (TCV) were 258.8 ± 81.7 µm and 6.6 ± 1.8 mm3, respectively. For non-DME group patients, mean SFCT and TCV values were 247.6 ± 73.3 µm and 6.6 ± 1.6 mm3, respectively. SFCT and TCV values for both groups were significantly lower than for healthy controls (294.3 ± 87.6 µm and 7.7 ± 1.8 mm,3 respectively) (p = 0.040 and 0.019, respectively). CTs varied according to morphological FA and OCT patterns of DME, but did not differ significantly (p > 0.05). CONCLUSIONS: CT and CV in DR patients were decreased compared with healthy controls. CTs did not differ significantly between DME patterns demonstrated by OCT and FA.

Precision (Repeatability and Reproducibility) and Agreement of Corneal Power Measurements Obtained by Topcon KR-1W and iTrace.

PURPOSE: To evaluate the repeatability and reproducibility of corneal power measurements obtained by Topcon KR-1W and iTrace, and assess the agreement with measurements obtained by Allegro Topolyzer and IOLMaster. METHODS: The right eyes of 100 normal subjects were prospectively scanned 3 times using all the 4 devices. Another observer performed additional 3 consecutive scans using the Topcon KR-1W and iTrace in the same session. About one week later, the first observer repeated the measurements using the Topcon KR-1W and iTrace. The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), J0 and J45 were analyzed. Repeatability and reproducibility of measurements were evaluated by the within-subject standard deviation (Sw), coefficient of variation (CoV), test-retest repeatability (2.77Sw), and intraclass correlation coefficient (ICC). Agreements between devices were assessed using Bland-Altman analysis and 95% limits of agreement (LoA). RESULTS: Intraobserver repeatability and interobserver and intersession reproducibility of the Ks, Kf and Km showed a CoV of no more than 0.5%, a 2.77Sw of 0.70 D or less, and an ICC of no less than 0.99. However, J0 and J45 showed poor intraobserver repeatability and interobserver and intersession reproducibility (all ICCs not greater than 0.446). Statistically significant differences existed between Topcon KR-1W and IOLMaster, Topcon KR-1W and iTrace, Topcon KR-1W and Topolyzer, iTrace and Topolyzer, iTrace and IOLMaster for Ks, Kf and Km measurements (all P < 0.05). The mean differences between Topcon KR-1W, iTrace, and the other 2 devices were small. The 95% LoA were approximately 1.0 D to 1.5 D for all measurements. CONCLUSIONS: The Ks, Kf and Km obtained by Topcon KR-1W and iTrace showed excellent intraobserver repeatability and interobserver and intersession reproducibility in normal eyes. The agreement between Topcon KR-1W and Topolyzer, Topcon KR-1W and IOLMaster, iTrace and Topolyzer, iTrace and IOLMaster, Topcon KR-1W and iTrace were not so good, they should not be interchangeable in clinical application. Given that the intraobserver repeatability and interobserver and intersession reproducibility of corneal astigmatism measurements obtained by Topcon KR-1W and iTrace were poor, it should be cautious that Topcon KR-1W and iTrace were applied for the preparation of toric lens implantation.

Corneal Power Measurement With the Dual Scheimpflug-Placido Topographer After Myopic Excimer Laser Surgery.

PURPOSE: To evaluate the ability of the Sirius Scheimpflug-Placido Topographer (Costruzione Strumenti Oftalmici, Florence, Italy) in predicting corneal power in eyes with previous myopic corneal refractive surgery. METHODS: The following corneal refractive power measurements were obtained with Sirius in 38 eyes with prior myopic excimer laser surgery: simulated keratometry (SimK), true net power based on the Gaussian optical formula (TNP), and the mean pupil power (MPP) calculated by ray tracing within the diameter of the entrance pupil range from 2.5 to 6 mm. These values, along with the corresponding keratometric value, which was based on the equation that converted the MPP within 4.5-mm entrance pupil diameter to a keratometric reading in 75 myopic eyes, were compared using the clinical history method. RESULTS: SimK significantly overestimated corneal power by 0.67 ± 0.52 diopters (D), whereas TNP significantly underestimated corneal power by -1.05 ± 0.48 D. The only measurements that showed no statistically significant difference by the clinical history method were the 5 mm MPP, 5.5 mm MPP, and KMPP4.5POST, and the 95% limits of agreement (LOA) were -1.10 to 0.62, -0.91 to 0.89, and -0.67 to 1.05 D, respectively. CONCLUSIONS: The Sirius Scheimpflug-Placido Topographer is an alternative method of measuring corneal power in eyes with previous corneal refractive surgery for myopia when preoperative data are not available. The best options seem to be the 5 mm MPP, 5.5 mm MPP, and the keratometric reading calculated from the regression formula.

Evaluation of Equivalent Keratometry Readings Obtained by Pentacam HR (High Resolution).

PURPOSE: To assess the repeatability of Equivalent Keratometry Readings (EKRs) obtained by the Pentacam HR (high resolution) in untreated and post-LASIK eyes, and to compare them with the keratometry (K) values obtained by other algorithms. METHODS: In this prospective study, 100 untreated eyes and 71 post-LASIK eyes were included. In the untreated group, each eye received 3 consecutive scans using the Pentacam HR, and EKR values in all central corneal zone, the true net power (Knet) and the simulated K (SimK) were obtained for each scan. In the post-LASIK group, each eye received subjective refraction and 3 consecutive scans with the Pentacam HR preoperatively. During the 3-month post-surgery exam, the same examinations and the use of an IOLMaster were conducted for each eye. The EKRs in all zone, the Knet, the mean K (Km) by IOLMaster and the K values by clinical history method (KCHM) were obtained. The repeatability of the EKRs was assessed by the within-subject standard deviation (Sw), 2.77Sw, coefficient of variation (CVw) and intraclass correlation coefficient (ICC). The bonferroni corrected multiple comparisons were performed to analyze the differences among the EKRs and K values calculated by other algorithms within the 2 groups. The 95% limits of agreement (LoA) were calculated. RESULTS: The EKR values in all central corneal zone were repeatable in both the untreated group (Sw≦0.19 D, 2.77Sw≦0.52 D, CVw≦1%, ICC≧0.978) and the post-LASIK group (Sw≦0.22 D, 2.77Sw≦0.62 D, CVw≦1%, ICC≧0.980). In the untreated group, the EKR in 4mm zone was close to SimK (P = 1.000), and the 95% LoA was (-0.13 to 0.15 D). The difference between Knet and SimK was -1.30±0.13 D (95% LoA -1.55 to -1.55 D, P<0.001). In the post-LASIK group, all the EKRs were significantly higher than KCHM (all P<0.001). The differences between the EKR in 4mm zone and KCHM, the EKR in 7mm zone and KCHM, Knet and KCHM, Km and KCHM, SimK and Knet were 0.64±0.50 D (95% LoA, -0.33 to 1.62 D), 1.77±0.88 D (95% LoA, 0.04 to 3.51 D), -0.98±0.48 D (95% LoA, -1.92 to -0.04 D), 0.64±0.53 D (95% LoA, -0.40 to 1.68 D), and 1.73±0.20 D (95% LoA, 1.33 to 2.13 D), respectively. CONCLUSIONS: The EKRs obtained by the Pentacam HR were repeatable in both untreated eyes and post-LASIK eyes. Compared to the total corneal power obtained by the clinical history method, the EKR values generally overestimated the total corneal power in post-LASIK eyes. So, further calibrations for the EKR values should be conducted, before they were used for the total corneal power assessment in post-LASIK eyes.

Keratometric index obtained by Fourier-domain optical coherence tomography.

PURPOSE: To determine the keratometric indices calculated based on parameters obtained by Fourier-domain optical coherence tomography (FD-OCT). METHODS: The ratio of anterior corneal curvature to posterior corneal curvature (Ratio) and keratometric index (N) were calculated within central 3 mm zone with the RTVue FD-OCT (RTVue, Optovue, Inc.) in 186 untreated eyes, 60 post-LASIK/PRK eyes, and 39 keratoconus eyes. The total corneal powers were calculated using different keratometric indices: Kcal based on the mean calculated keratometric index, K1.3315 calculated by the keratometric index of 1.3315, and K1.3375 calculated by the keratometric index of 1.3375. In addition, the total corneal powers based on Gaussian optics formula (Kactual) were calculated. RESULTS: The means for Ratio in untreated controls, post-LASIK/PRK group and keratoconus group were 1.176 ± 0.022 (95% confidence interval (CI), 1.172-1.179), 1.314 ± 0.042 (95%CI, 1.303-1.325) and 1.229 ± 0.118 (95%CI, 1.191-1.267), respectively. And the mean calculated keratometric index in untreated controls, post-LASIK/PRK group and keratoconus group were 1.3299 ± 0.00085 (95%CI, 1.3272-1.3308), 1.3242 ± 0.00171 (95%CI, 1.3238-1.3246) and 1.3277 ± 0.0046 (95%CI, 1.3263-1.3292), respectively. All the parameters were normally distributed. The differences between Kcal and Kactual, K1.3315 and Kactual, and K1.3375 and Kactual were 0.00 ± 0.11 D, 0.21 ± 0.11 D and 0.99 ± 0.12 D, respectively, in untreated controls; -0.01 ± 0.20 D, 0.85 ± 0.18 D and 1.56 ± 0.16 D, respectively, in post-LASIK/PRK group; and 0.03 ± 0.67 D, 0.56 ± 0.70 D and 1.40 ± 0.76 D, respectively, in keratoconus group. CONCLUSION: The calculated keratometric index is negatively related to the ratio of anterior corneal curvature to posterior corneal curvature in untreated, post-LASIK/PRK, and keratoconus eyes, respectively. Using the calculated keratometric index may improve the prediction accuracies of total corneal powers in untreated controls, but not in post-LASIK/PRK and keratoconus eyes.

Anterior chamber depth measurements using Scheimpflug imaging and optical coherence tomography: repeatability, reproducibility, and agreement.

PURPOSE: To determine the repeatability, reproducibility, and agreement of anterior chamber depth (ACD) measurements obtained with 3 Scheimpflug cameras and an anterior segment optical coherence tomography (AS-OCT) device. SETTING: Eye Hospital of Wenzhou Medical University, Zhejiang, China. DESIGN: Observational cross-sectional study. METHODS: Two observers took 3 consecutive measurements in healthy right eyes using each device to assess intraoperator repeatability. The mean values obtained at different sessions by the first operator were used to determine the intersession reproducibility. Three consecutive measurements obtained by the first operator at the first session were averaged and used to assess agreement. RESULTS: The ACD measurements obtained by 2 observers in 71 eyes were highly repeatable using the 4 devices, with a test-retest repeatability of 0.04 to 0.07 mm for intraoperator repeatability. The interoperator and intersession reproducibility of ACD measurements were high, and the test-retest repeatability ranges of interoperator and intersession reproducibility were 0.06 to 0.07 mm and 0.05 to 0.08 mm, respectively. The ACD measurements of the 4 systems were sorted from the thickest to the thinnest (Galilei G2 > Visante > Sirius > Pentacam). The differences in the measurements were statistically significant except between the ACD measurements obtained by the Sirius device and the Visante device. However, good agreement with narrow 95% limits of agreement was found between these devices. CONCLUSIONS: The 4 devices provided high intraoperator repeatability and interoperator and intersession reproducibility for ACD measurements. Good agreement in ACD measurements was found between the devices in healthy eyes. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.