OBJECTIVE: To compare the axial length derived from a formula incorporating corneal dimensions with the results obtained by A-scan biometry. METHODS: This is a nonrandomized comparative study of patients from the outpatient department of a tertiary-care academic medical institution who were screened for cataract surgery. Corneal diameter and slope were measured with a Vernier no. 6 caliper and axial length determined using Ophthasonic A-Scan III machine. Computed axial lengths were arrived at using a formula incorporating corneal diameter and slope. The mean difference of measured and computed axial lengths were statistically analyzed using paired t test and general linear model tests. RESULTS: A total of 105 eyes (96 patients) were included in the study. The mean difference between computed and measured axial lengths was not statistically significant (p=0.64 for computed axial length< 22.00 mm, p=0.11 for computed axial length of 22.00 to 22.99, p=0.81 for computed axial length of 23.00 to 23.99, and p=0.03 for computed axial length ? 24.00 mm). CONCLUSION: Axial length measured with an A-scan can be reliably approximated by using Surrells formula based on corneal length measurements.
Human ; BIOMETRY ; CORNEA ; LENSES, INTRAOCULAR ; AXIAL LENGTH, EYE

PURPOSE: To evaluate choroidal blood flow changes in eyes with high myopia according to the pulsatile components of ocular blood flow analysis. METHODS: A total of 104 subjects (52 males and 52 females) were included in this study. One eye of each participant was randomly selected and assigned to one of four refractive groups, designated as, hyperopes (n = 20; refractive error, > or =+1.00 diopter [D]), emmetropes (n = 28; refractive error, +/-0.75 D), lower myopes (n = 33; refractive error, -1.00 to -4.75 D), and high myopes (n = 23; refractive error, < or =-5.00 D). Components of pulse amplitude (OBFa), pulse volume (OBFv), pulse rate (OBFr), and pulsatile ocular blood flow (POBF) were analyzed using a blood flow analyzer. Intraocular pressure and axial length were measured. RESULTS: Pulsatile components of OBFa, OBFv, and POBF showed positive correlations with refractive error and showed negative correlations with axial length (r = 0.729, r = 0.772, r = 0.781, respectively, all p < 0.001; r = -0.727, r = -0.762, r = -0.771, respectively, all p < 0.001). The correlations of refractive error and axial length with OBFr were irrelevant (r = -0.157, p = 0.113; r = 0.123, p = 0.213). High myopes showed significantly lower OBFa, OBFv, and POBF than the other groups (all p < 0.001). CONCLUSIONS: Axial length changes in high myopes potentially influence choroidal blood flow, assuming the changes are caused by narrowing of the choroidal vessel diameter and increasing rigidity of the choroidal vessel wall. These finding explains the influence of axial length on OBFa, OBFv, and POBF, but not on OBFr. Thus, changes in axial length and the possible influence of these changes on the physical properties of choroidal vessels is the mechanism believed to be responsible for putting high myopes at risk for ocular vascular diseases.
Adult ; *Axial Length, Eye ; Choroid/*blood supply ; Female ; Humans ; Male ; Myopia/diagnosis/*physiopathology ; Regional Blood Flow/*physiology ; Young Adult

PURPOSE: To investigate the feasibility of estimating effective lens position (ELP) and calculating intraocular lens power using corneal height (CH), as measured using anterior segment optical coherence tomography (AS-OCT), in patients who have undergone corneal refractive surgery. METHODS: This study included 23 patients (30 eyes) who have undergone myopic corneal refractive surgery and subsequent successful cataract surgery. The CH was measured with AS-OCT, and the measured ELP (ELP(m)) was calculated. Intraocular lens power, which could achieve actual emmetropia (P(real)), was determined with medical records. Estimated ELP (ELP(est)) was back-calculated using P(real), axial length, and keratometric value through the SRK/T formula. After searching the best-fit regression formula between ELP(m) and ELP(est), converted ELP and intraocular lens power (ELP(conv), P(conv)) were obtained and then compared to ELP(est) and P(real), respectively. The proportion of eyes within a defined error was investigated. RESULTS: Mean CH, ELP(est), and ELP(m) were 3.71 +/- 0.23, 7.74 +/- 1.09, 5.78 +/- 0.26 mm, respectively. The ELP(m) and ELP(est) were linearly correlated (ELP(est) = 1.841 x ELP(m) - 2.018, p = 0.023, R = 0.410) and ELP(conv) and P(conv) agreed well with ELP(est) and P(real), respectively. Eyes within +/-0.5, +/-1.0, +/-1.5, and +/-2.0 diopters of the calculated P(conv), were 23.3%, 66.6%, 83.3%, and 100.0%, respectively. CONCLUSIONS: Intraocular lens power calculation using CH measured with AS-OCT shows comparable accuracy to several conventional methods in eyes following corneal refractive surgery.
Axial Length, Eye/pathology ; Cornea/pathology/*surgery ; Humans ; *Lenses, Intraocular ; Male ; Middle Aged ; *Refractive Surgical Procedures ; Retrospective Studies ; Tomography, Optical ; Tomography, Optical Coherence

PURPOSE: To investigate the feasibility of estimating effective lens position (ELP) and calculating intraocular lens power using corneal height (CH), as measured using anterior segment optical coherence tomography (AS-OCT), in patients who have undergone corneal refractive surgery. METHODS: This study included 23 patients (30 eyes) who have undergone myopic corneal refractive surgery and subsequent successful cataract surgery. The CH was measured with AS-OCT, and the measured ELP (ELP(m)) was calculated. Intraocular lens power, which could achieve actual emmetropia (P(real)), was determined with medical records. Estimated ELP (ELP(est)) was back-calculated using P(real), axial length, and keratometric value through the SRK/T formula. After searching the best-fit regression formula between ELP(m) and ELP(est), converted ELP and intraocular lens power (ELP(conv), P(conv)) were obtained and then compared to ELP(est) and P(real), respectively. The proportion of eyes within a defined error was investigated. RESULTS: Mean CH, ELP(est), and ELP(m) were 3.71 +/- 0.23, 7.74 +/- 1.09, 5.78 +/- 0.26 mm, respectively. The ELP(m) and ELP(est) were linearly correlated (ELP(est) = 1.841 x ELP(m) - 2.018, p = 0.023, R = 0.410) and ELP(conv) and P(conv) agreed well with ELP(est) and P(real), respectively. Eyes within +/-0.5, +/-1.0, +/-1.5, and +/-2.0 diopters of the calculated P(conv), were 23.3%, 66.6%, 83.3%, and 100.0%, respectively. CONCLUSIONS: Intraocular lens power calculation using CH measured with AS-OCT shows comparable accuracy to several conventional methods in eyes following corneal refractive surgery.
Axial Length, Eye/pathology ; Cornea/pathology/*surgery ; Humans ; *Lenses, Intraocular ; Male ; Middle Aged ; *Refractive Surgical Procedures ; Retrospective Studies ; Tomography, Optical ; Tomography, Optical Coherence

PURPOSE: To investigate normative angle kappa data and to examine whether correlations exist between angle kappa and ocular biometric measurements (e.g., refractive error, axial length) and demographic features in Koreans. METHODS: Data from 436 eyes (213 males and 223 females) were analyzed in this study. The angle kappa was measured using Orbscan II. We used ocular biometric measurements, including refractive spherical equivalent, interpupillary distance and axial length, to investigate the correlations between angle kappa and ocular biometry. The IOL Master ver. 5.02 was used to obtain axial length. RESULTS: The mean patient age was 57.5 +/- 12.0 years in males and 59.4 +/- 12.4 years in females (p = 0.11). Angle kappa averaged 4.70 +/- 2.70 degrees in men and 4.89 +/- 2.14 degrees in women (p = 0.48). Axial length and spherical equivalent were correlated with angle kappa (r = -0.342 and r = 0.197, respectively). The correlation between axial length and spherical equivalent had a negative correlation (r = -0.540, p < 0.001). CONCLUSIONS: Angle kappa increased with spherical equivalent and age. Thus, careful manipulation should be considered in older and hyperopic patients when planning refractive or strabismus surgery.
Anterior Chamber/*pathology ; *Axial Length, Eye ; Diagnostic Techniques, Ophthalmological/*instrumentation ; Equipment Design ; Female ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Morbidity/trends ; Refractive Errors/*diagnosis/epidemiology ; Republic of Korea/epidemiology ; Retrospective Studies

PURPOSE: To evaluate the thickness and volume of the choroid in healthy Korean children using swept-source optical coherence tomography. METHODS: We examined 80 eyes of 40 healthy children and teenagers (<18 years) using swept-source optical coherence tomography with a tunable long-wavelength laser source. A volumetric macular scan protocol using the Early Treatment Diabetic Retinopathy Study grid was used to construct a choroidal thickness map. We also examined 44 eyes of 35 healthy adult volunteers (> or =18 years) and compared adult measurements with the findings in children. RESULTS: The mean age of the children and teenagers was 9.47 +/- 3.80 (4 to 17) vs. 55.04 +/- 12.63 years (36 to 70 years) in the adult group (p < 0.001, Student's t-test). Regarding the Early Treatment Diabetic Retinopathy Study subfields, the inner temporal subfield was the thickest (247.96 microm). The inner and outer nasal choroid were thinner (p = 0.004, p = 0.002, respectively) than the surrounding areas. The mean choroidal volumes of the inner and outer nasal areas were smaller (p = 0.004, p = 0.003, respectively) than those of all the other areas in each circle. Among the nine subfields, all areas in the children, except the outer nasal subfield, were thicker than those in adults (p < 0.05). Regression analysis showed that age, axial length, and refractive error correlated with subfoveal choroidal thickness (p < 0.05). CONCLUSIONS: Overall macular choroidal thickness and volume in children and teenagers were significantly greater than in adults. The nasal choroid was significantly thinner than the surrounding areas. The pediatric subfoveal choroid is prone to thinning with increasing age, axial length, and refractive error. These differences should be considered when choroidal thickness is evaluated in children with chorioretinal diseases.
Adolescent ; Adult ; Aged ; Aging/physiology ; Asian Continental Ancestry Group ; Axial Length, Eye/anatomy & histology ; Child ; Child, Preschool ; Choroid/*anatomy & histology ; Female ; Healthy Volunteers ; Humans ; Macula Lutea/anatomy & histology ; Male ; Middle Aged ; Republic of Korea ; *Tomography, Optical Coherence

PURPOSE: To compare the refractive results of cataract surgery measured by applanation ultrasound and the new partial coherence interferometer, AL-scan. METHODS: Medical records of 76 patients and 104 eyes who underwent cataract surgery from January 2013 to June 2013 were retrospectively reviewed. Biometries were measured using ultrasound and AL-scan and intraocular lens power was calculated using the SRK-T formula. Automatic refraction examination was done 1 month after the operation, and differences between the ultrasound group and AL-scan group were compared and analyzed by mean absolute error. RESULTS: Mean axial length measured preoperatively by the ultrasound method was 23.53 +/- 1.17 mm while the lengths measured using the AL-scan were 0.03 mm longer than that of the ultrasound group (23.56 +/- 1.15 mm). However, there was not a significant difference in this finding (p = 0.638). Mean absolute error was 0.34 +/- 0.27 diopters in the ultrasound group and 0.36 +/- 0.31 diopters in AL-scan group, which showed no significant difference (p = 0.946) in precision of predicting postoperative refraction. CONCLUSIONS: Although the difference was not statistically significant, intraocular lens calculations done by the AL-scan were nearly similar in predicting postoperative refraction compared to those of applanation ultrasound, however more precise measurements may be obtained if the axial length is longer than 24.4 mm. Except in the case of opacity in the media, which makes obtaining measurements with the AL-scan difficult, AL-scan could be a useful biometry in cataract surgery.
Aged ; Anterior Chamber/pathology ; Axial Length, Eye/*pathology ; Biometry/methods ; Female ; Humans ; Interferometry/*instrumentation ; *Lens Implantation, Intraocular ; Lenses, Intraocular ; Light ; Male ; Middle Aged ; *Phacoemulsification ; Refraction, Ocular/physiology ; Reproducibility of Results ; Retrospective Studies ; Visual Acuity/physiology