Corneal Curvature Values Research Articles

KeraRing Implantation with Femtosecond Laser in Keratoconus Treatment at Different Stages

Objective: To investigate the reliability and effectiveness of femtosecond laser-assisted KeraRing (Mediphacos, Belo Horizonte, Brazil) implantation in treating keratoconus. Methods: Intrastromal corneal ring segments (KeraRing, Mediphacos, Brazil) were implanted in 15 eyes of 14 patients unable to tolerate contact lenses. Femtosecond laser (Intralase, 60 Hz) was used for corneal tunnel creation. Based on the distribution of ectatic area on the cornea, dual segments were implanted in 9 eyes, while single segments were implanted in 6 eyes. Preoperative and postoperative uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), objective and subjective refraction, and topographic corneal curvature (K) values of the cases were compared using the Wilcoxon test. Results: The mean age of patients was 25±7.46 (range: 15-39) years, with a mean postoperative follow-up period of 10.8±7.37 (range: 1-24 months). BCVA improved in all eyes during the follow-up period, increasing from a mean of 0.12±0.1 to 0.38±0.24 (p

Efficacy comparison of combining cross-linking and refractive laser ablation in progressive keratoconus: systematic review and meta-analysis

ObjectiveThis study assessed the effect of combining corneal collagen cross-linking (CXL) with refractive laser ablation techniques for the treatment of keratoconus, a progressive corneal disorder. MethodsWe performed a systematic review and meta-analysis to assess the effect of combined CXL and refractive techniques. We included all published clinical trials or observational studies published by September 1, 2023. We calculated and compared the standardized mean difference (SMD) between CXL alone and CXL plus laser ablation for uncorrected distance visual acuity, best-corrected distance visual acuity, spherical equivalent manifest refraction, sphere and cylinder, flat keratometry (K1), steep keratometry (K2), and central corneal thickness. ResultsWe identified 13 studies that fulfilled our inclusion and exclusion criteria. The average follow-up was 21.3 ± 11.8 months. The CXL plus laser ablation group showed improvement in uncorrected distance visual acuity logMAR (SMD, –0.35; 95% CI, –0.67 to –0.04; p = 0.029), best-corrected distance visual acuity logMAR (SMD, –0.17; 95% CI, –0.30 to –0.03; p = 0.014), spherical equivalent manifest refraction (SMD, –0.28; 95% CI, 0.06–0.50; p = 0.013), and change in maximal corneal curvature (Kmax; SMD, –0.41; 95% CI, –0.69 to –0.13; p = 0.004) compared with CXL alone. However, central corneal thickness decreased further among patients who underwent CXL plus laser ablation (SMD, –0.37; 95% CI, –0.66 to –0.07; p = 0.016). No effect was observed in terms of sphere (p = 0.878), cylinder (p = 0.859), K1 (p = 0.907), or K2 (p = 0.169). Ectasia was not observed as an adverse effect resulting from the additional corneal ablation performed during the CXL treatments. ConclusionsThis study showed that combining refractive laser ablation techniques with standard or accelerated CXL treatment improved visual and refractive outcomes and anterior corneal curvature values.

Ptosis effects on intraocular lens power calculation.

To evaluate quantitatively ocular biometric parameters and intraocular lens (IOL) power measurements post-ptosis surgery. This study comprised involutional ptosis patients divided into droopy eyelid severity groups: Group 1:>4 mm, Group 2:3-4 mm, and Group 3:1-2 mm. The patients underwent anterior levator resection (ALR), and preoperative and postoperative biometry measurements 3 months postoperatively were obtained. The Group 1 sample size was 19, Group 2 was 22, and Group 3 was 16. The mean K1, K2, and Km values significantly decreased 3 months postoperatively in Group 1 (P<0.001 for all). The mean K1, K2, and Km values non-significantly decreased 3 months postoperatively in Groups 2 and 3 (P>0.05 for all). The mean corneal astigmatism magnitude decreased 3 months postoperatively in Group 1 (P<0.01), Group 2 (P=0.186), and Group 3 (P=0.952). The mean recommended IOL powers targeting emmetropia increased postoperatively in Group 1 and were similar pre- and postoperatively in Groups 2 and 3. In Group 1, the mean changes after ptosis surgery by formula were 0.47 D for SRK/T, 0.52 D for Hoffer Q, 0.55 D for Haigis, 0.50 D for Barrett Universal II and 0.55 D for Holladay 2. Ptosis > 4 mm significantly impacts corneal curvature values and IOL power calculations when cataract surgery is planned. Surgeons might consider altering their lens power choice accordingly if cataract surgery is to be sequentially followed by ptosis repair.

Efficacy of custom-made soft keratoconus lenses on corneal aberrations and photic phenomena in patients with keratoconus: a corneal topography imaging based study.

To evaluate the efficacy of custom-made soft keratoconus (KC) lenses on corneal aberrations and photic phenomena in two different optical zones in patients with KC. Sixty eyes of 42 patients with KC were examined at baseline and after fitting HydroCone (Toris K) soft silicone hydrogel lenses. Best spectacle-corrected visual acuity (BSCVA) and contact lens-corrected visual acuity (CLCVA) were recorded. Lower- and higher-order corneal aberrations (LOAs and HOAs) were measured with and without Toris K lenses and compared in central 4.5 mm and 7 mm zones. Mesopic pupil diameter and subjective photic phenomena were also assessed. Mean CLCVA was significantly improved compared to BSCVA (P<0.0001). Corneal curvature and refractive measurements were found to be significantly reduced by the use of Toris K lenses, except for posterior corneal curvature values. In the 4.5 mm central optical zone, all wavefront aberrations decreased significantly after lens fitting (P<0.0001). In contrast, in the 7 mm (peripheral) optical zone, values for HOAs, spherical and residual aberrations, and optical path differences were increased, while LOAs, trefoil, and quadrifoil coefficients were decreased. The rate of photic phenomena was significantly higher in participants with a pupil size >6.00 mm (85.7%). Toris K lenses provide good visual results and a significant reduction in central corneal aberrations in patients with KC but could cause an increase in peripheral aberrations. This practical and nonsurgical approach appears to be an effective method for the visual management of KC.

Evaluation of ocular biometry in the Japanese population using a multicenter approach: Prospective observational study.

This prospective observational study aimed to evaluate the ocular biometry of Japanese people through a multicenter approach. The uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) in the log minimum angle of resolution (logMAR), subjective and objective spherical equivalent values (SE) of ocular refraction, anterior and posterior corneal curvature (ACC and PCC, respectively), anterior and posterior corneal asphericity (ACA and PCA, respectively), central corneal thickness (CCT), anterior chamber depth (ACD), and ocular axial length (AL) were measured in the eyes of 250 participants (mean age = 46.5 ± 18.0 years, range: 20–90 years) across five institutions in Japan. The mean UDVA, CDVA, subjective SE, objective SE, ACC, PCC, ACA, PCA, CCT, ACD, and AL were 0.68, −0.08, −2.42 D, −2.66 D, 7.77 mm, 6.33 mm, −0.31, −0.39, 0.55 mm, 2.92 mm, and 24.78 mm, respectively. Age-related changes and sex-based differences were noted in the visual acuity, refraction, corneal shape, ACD, and AL. Our results serve as basis for future studies aiming to develop refractive correction methods and various vision-related fields.

Laser In Situ Keratomileusis (LASIK) Combined with Prophylactic Corneal Cross-Linking for Correction of Myopia: Regional Analysis of Corneal Morphology.

IntroductionThis study evaluated the outcomes of laser in situ keratomileusis (LASIK) combined with prophylactic corneal collagen cross-linking (CXL) in correcting myopia in cases with increased estimated risk of postoperative corneal ectasia, detected by regional analysis of corneal morphology.MethodsThe retrospective study included 180 eyes of 99 patients. Group 1 (94 eyes of 49 patients) with increased risk of postoperative corneal ectasia, as detected by “Ectasia Risk Factor Score System for LASIK”, underwent femtosecond laser-assisted LASIK (FS-LASIK) combined with prophylactic CXL, using short riboflavin soaking time and low UV energy. Group 2 (86 eyes of 50 patients) with normal corneal topography, who underwent FS-LASIK alone, were used as controls. Refractive and visual outcomes and Scheimpflug topo/tomography were analyzed preoperatively and 1 week, 1 month, and 12 months postoperatively. Mean regional corneal curvature (M) values for three subregions (the central 3.0 mm region, the paracentral 3.0–6.0 mm region, and the peripheral 6.0–9.0 mm region) of both anterior and posterior surfaces were calculated.ResultsAn increase in flattening of the peripheral anterior region and more steepening of the posterior paracentral region were shown at 12 months compared to 1 month postoperatively in group 1. The findings were significantly more pronounced than in group 2 (P < 0.001 and P = 0.035, respectively). The refractive and visual outcomes were comparable in the two groups.ConclusionsProphylactic CXL seems to influence corneal regional reshaping after surgery, while not affecting the 1-year visual and refractive results.

Long-term Outcomes of Collagen Crosslinking for Early Keratoconus.

PurposeTo evaluate the long-term outcomes of collagen crosslinking in early keratoconus.MethodsThirty eyes of twenty patients with early keratoconus were enrolled. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), objective refraction, subjective refraction, corneal topography and pachymetry were assessed before and 3, 6, 12 months and 9 years after performing collagen crosslinking surgery.ResultsThe patients' mean age was 31.2 5.59 years at nine-year follow-up (range, 25–44 years). The means of preoperative UCVA and BSCVA were 0.57 0.34 and 0.15 0.12 logMAR, respectively, and these values remained stable at the final follow-up (P = 0.990 and P = 0.227, respectively). The mean objective spherical equivalent decreased considerably from –6.00 4.05 D preoperatively to –5.22 3.71 D at the final follow-up (P 0.05). The mean subjective spherical equivalent was –4.25 2.87 D preoperatively and this value was stable at the last follow-up (P = 0.92). No considerable difference was found between the post- and preoperative mean objective cylinder values (P = 0.34). The mean subjective cylinder value changed significantly from –4.05 1.85 D preoperatively to –3.1 1.42 D at the final follow-up (P 0.05). The mean central corneal thickness was 496.97 45.95 µm preoperatively and this value was stable at nine-year follow-up (P = 0.183). No significant difference was found between the pre- and postoperative mean maximum and mean minimum corneal curvature values (P = 0.429 and P = 0.248, respectively). There were no significant postoperative complications.ConclusionCorneal crosslinking in early keratoconus seems to be a safe procedure that can effectively stabilize UCVA, BSCVA, subjective SE and CCT, while improving objective spherical equivalent.

Agreement of corneal curvature and central corneal thickness obtained from a swept-source OCT and Pentacam in ectopia lentis patients

To assess the inter-device consistency of corneal curvature and central corneal thickness between Pentacam and a swept-source Fourier-domain anterior segment optical coherence tomography (AS-OCT) in ectopia lentis patients. Totally 72 eyes of ectopia lentis patients were recruited. Central corneal thickness (CCT), corneal curvature values and corneal astigmatism were obtained from both the Pentacam and AS-OCT (CASIA2). Repeatability was evaluated for both devices. The coefficient of repeatability (COR) and the relative COR was calculated. Bland-Altman plots were conducted to evaluate the inter-device agreement of measurement. Orthogonal linear regression was used to examine any proportional bias. The mean difference of CCT, steep anterior corneal curvature (anterior KS), flat anterior corneal curvature (anterior Kf), anterior corneal astigmatism (ACA), steep posterior corneal curvature (posterior KS), flat posterior corneal curvature (posterior Kf), posterior corneal astigmatism (PCA), steep true net power (TNP KS), flat true net power (TNP Kf) and total corneal astigmatism (TCA) between Pentacam and CASIA2 were 7.03±9.70 µm, -0.19±0.41 D, -0.27±0.35 D, 0.04±0.47 D, -0.17±0.23 D, -0.11±0.11 D, -0.02±1.02 D -0.41±0.43 D, -0.52±0.46 D, and -0.15±0.96 D, respectively. For measurement of TNP Kf with the Pentacam and CASIA2, a mean difference of 0.52 D and COR of 0.90 with P=0.02 was detected. There was no significant difference in CCT (P=0.393), anterior Kf (P=0.107), anterior Ks (P=0.414), ACA (P=0.131), posterior Kf (P=0.286), posterior Ks (P=0.418), PCA (P=0.105), TNP Ks (P=0.054), and TCA (P=0.977) between Pentacam and CASIA2. Our study reveals good agreement of CCT, corneal curvature and corneal astigmatism measured by CASIA2 and Pentacam in ectopia lentis patients. However, there was significant difference for CCT and corneal curvature values obtained by the two devices.

Оcular Surface in Long Terms of Ortokeratology Lenses’s Use in Adolescents with Myopia

The purpose: to study to evaluate the effect of ortokeratology lenses (OK-lenses) on the state of the ocular surface, depending on the duration of their wearing by adolescents with myopia. Patients and methods. Under control were 212 patients with myopia aged 12 to 16 years, who used OK-lenses “Paragon CRT100” (USA) for a long time (3–5 years). Examination, in addition to standard ophthalmological methods, included evaluation of complaints using the OSDI questionnaire/scale, Schirmer, Norn tests and biomicroscopy with staining of the cornea with fluorescein before and during wearing OK-lenses. Patients with keratopathy additionally underwent scanning confocal microscopy of the cornea using ConfoSkan-4 (Nidek, Japan); bacteriological examination of scraping from the cornea. Results. Clinical and functional signs of dry eye syndrome (SDE) in patients before and after prolonged use of OK therapy are not diagnosed. In 12 (5.6 %) teenagers with non-standard values of corneal curvature, signs of late epitheliopathy were revealed against the background of the absence of complaints. Patients were divided into 2 subgroups depending on the choice of antimicrobial eye drops in addition to keratoprotectors. The results of treatment in both subgroups were the same, but the use of fluoroquinolones was accompanied by an adverse development of SDE. Conclusion. In general, long-term OK therapy of myopia in adolescents is safe. The compulsory condition is an adequate prescription and observance of the wearing and lens care rules. It does not have a significant adverse effect on the clinical and functional state of the ocular surface, including the cornea. The frequency of late epitheliopathies with long-term (3–5 years) wearing OK lenses is 5.6 %, and the severity of the manifestation is characterized mainly by a mild degree. Patients with extreme corneal curvature are in a high-risk group for the development of late corneal complications during the use of OK therapy. If late epitheliopathies are detected while wearing OK lenses, it is necessary to cancel their use and to prevent the development of infectious keratitis, in addition to keratoprotectors, you can add the modern antimicrobial drug with antiseptic effect, for example, Vitabact, as the original, without a preservative, approved medicine for use in children. The use of fluoroquinolone drugs with virtually aseptic inflammation of the cornea is unjustified.

Relationship Between Visual Acuity and Corneal Curvature Change in Children After Epiblepharon Surgery.

To determine the relationship between visual acuity and corneal curvature change in children after epiblepharon correction surgery by corneal topography. The authors retrospectively reviewed the data of 62 children (121 eyes) who had epiblepharon surgery. The authors measured keratometric values of corneal curvature for 2 corneal zones: central 3 and 5 mm zone. Two zones were classified into 4 areas, including nasal, superior, temporal, and inferior area. Visual acuity and keratometric values were estimated preoperatively and at 1, 3, and 6 months postoperatively. The authors analyzed the correlation between visual acuity and corneal curvature change in 4 areas of the 2 zones. There were statistically significant differences between preoperative and postoperative visual acuity 1 month after surgery. At postoperative 3 months, the inferior and superior areas of the 3 mm corneal zone were much flatter than before surgery (P < 0.05). Corneal curvature only at the inferior area of the 3 mm zone had significantly a negative correlation with postoperative visual acuity at 3 and 6 months (r = -0.275, P = 0.02 and r = -0.351, P = 0.01, respectively). However, visual acuity had no significant correlation with corneal curvature change in any of the areas of the 5-mm corneal zone. The authors found that corneal curvature has significantly become flattened in the superior and inferior areas of the 3 mm corneal zone, postoperatively. Furthermore, inferior area in the 3 mm corneal zone affected only on the visual acuity improvement after postoperative 3 months.

Corneal Curvature Measurements Utilizing a New Swept-source Optical Coherence Tomography Tomey OA-2000® and Comparison With IOL Master® 500 in Pterygium Patients

Introduction: Corneal curvature (CC) is an important anterior segment parameter. This study compared CC measurements conducted with two optical devices in pterygium eyes.Methods: Sixty pterygium eyes of 30 patients were enrolled in this study. CC was measured three times with the optical biometer and topography-keratometer Tomey OA-2000 (Tomey Corporation, Nagoya, Japan), then with partial optical coherence interferometry (PCI) IOL Master 500 (Carl Zeiss Meditec, Dublin, CA) and data were statistically analysed.Results: The measurements revealed in a mean CC of 43.86 ± 1.57 D with Tomey OA-2000 and 43.84 ± 1.55 D with IOL Master. Distribution of data is normal, and no significance difference in CC values was detected (P = 0.952) between the two devices. Correlation between CC measurements was highly significant (r = 0. 99; P &lt; 0.0001). The mean difference of CC values between devices was 0.017 D and 95% limit of agreement was -0.088 to 0.12. Duration taken for measurements with the standard biometer IOL Master was longer (55.17 ± 2.24 seconds) than with Tomey OA-2000 (39.88 ± 2.38 seconds) in automatic mode. Duration of manual measurement with Tomey OA-2000 in manual mode was shorter (28.57 ± 2.71 seconds).Conclusion: In pterygium eyes, CC measured with Tomey OA-2000 and IOL Master showed similar values, and high correlation was observed between these two devices. This shows that both devices can be used interchangeably. Tomey OA-2000 is better in terms of faster to operate and has its own topography systems.

Corneal Curvature, Astigmatism, and Aberrations in Marfan Syndrome with Lens Subluxation: Evaluation by Pentacam HR System

Marfan syndrome (MFS) is associated with abnormalities of corneal biometric characteristics. We conducted a retrospective case-control study including 55 eyes of the MFS patients with lens subluxation and 53 normal eyes of the control subjects to evaluate the corneal curvature, astigmatism and aberrations using a rotating Scheimpflug camera (Pentacam HR). Compared with the control group, the anterior, posterior, and total corneal curvature were flatter in the MFS group. The anterior and total corneal astigmatism were higher in the MFS patients, whereas the posterior corneal astigmatism was not significantly different between the two groups. Regarding the total corneal aberrations, the root mean square (RMS) aberrations, RMS higher-order aberrations and RMS lower-order aberrations increased, whereas the spherical aberration decreased in the MFS patients. Corneal parameters had potential diagnostic values for MFS patients with lens subluxation and the more reasonable cutoffs were the values of corneal curvature <41.35 D, corneal astigmatism >0.85 D and spherical aberration <0.188 μm. Corneal biometric characteristics of MFS patients with lens subluxation include decreased corneal curvature, higher corneal astigmatism, larger corneal aberrations, and lower spherical aberration. Corneal curvature, corneal astigmatism, and spherical aberration are better diagnostic tools for suspicious MFS.

Corneal tomography and biomechanics in primary pterygium.

To study the Scheimpflug's imaging and corneal biomechanics in primary pterygium. A prospective observational study of 55 patients with unilateral primary nasal pterygium was done. The normal fellow eyes of patients with pterygium were taken as controls. Clinical parameters noted included visual acuity, values of corneal curvature by doing Scheimpflug imaging, wavefront aberrations in terms of higher and lower-order aberrations and corneal hysteresis (CH) as well as corneal resistance factor (CRF) values by using ocular response analyzer. Of the total 55 patients, mean age was 43.0+11.4years (range: 20-72years). Mean LogMar uncorrected visual acuity in pterygium eyes and control eyes was 0.21+0.20 and 0.12+0.15, respectively (p=0.016). On Scheimpflug imaging the mean anterior corneal curvature values (Ka1/Ka2 D) were 41.09+3.38/44.33+2.29 in pterygium eyes, 43.13+1.79/43.98+2.17 in control eyes (p<0.0005) and mean posterior corneal curvature (Kp1/Kp2 D) values were 6.14+0.39/6.53+0.43 in pterygium eyes and 6.13+0.28/6.46+0.47 in control eyes (p>0.05). Analysis of corneal aberrations showed significantly higher corneal wavefront aberrations in pterygium eyes. Highest correlation of corneal astigmatism was noted with corneal area encroached by pterygium (ρ=0.540 for LOA and 0.553 for HOA) and distance from pupillary center (ρ=0.531 for LOA and 0.564 for HOA). Corneal biomechanical parameters including CH and CRF were found to be lower in the pterygium eyes, though not statistically significant (p value 0.60 and 0.59, respectively). Pterygium leads to deterioration of visual performance not only by causing refractive and topographic changes but also by causing a significant increase in corneal wavefront aberrations.

Ocular findings in adult subjects with an inactivating mutation in GH releasing hormone receptor gene

ObjectiveOcular function is fundamental for environmental adaptation and survival capacity. Growth factors are necessary for a mature eyeball, needed for adequate vision. However, the consequences of the deficiency of circulating growth hormone (GH) and its effector insulin-like growth factor I (IGF-I) on the physical aspects of the human eye are still debated. A model of untreated isolated GH deficiency (IGHD), with low but measurable serum GH, may clarify this issue. The aim of this study was to assess the ocular aspects of adult IGHD individuals who have never received GH therapy. DesignCross sectional study. MethodsSetting: University Hospital, Federal University of Sergipe, Brazil. Patients: Twenty-five adult (13 males, mean age 50.1years, range 26 to 70years old) IGHD subjects homozygous for a null mutation (c.57+1G>A) in the GHRH receptor gene, and 28 (15 males, mean age 51.1years, range 26 to 67years old) controls were submitted to an endocrine and ophthalmological assessment. Forty-six IGHD and 50 control eyes were studied. Main outcome measures: Visual acuity, intraocular pressure, refraction (spherical equivalent), ocular axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous depth (VD), mean corneal curvature (CC) and central corneal thickness (CCT). ResultsIGHD subjects exhibited unmeasurable serum IGF-I levels, similar visual acuity, intraocular pressure and LT, higher values of spherical equivalent and CC, and lower measures of AL, ACD, VD and CCT in comparison to controls, but within their respective normal ranges. While mean stature in IGHD group was 78% of the control group, mean head circumference was 92% and axial AL was 96%. ConclusionsThese observations suggest mild ocular effects in adult subjects with severe IGF-I deficiency due to non-treated IGHD.

Correlation between axial length and corneal curvature and spherical aberration

Objective: To discuss the correlation between axial length and corneal curvature and corneal spherical aberration in a group of cataract patients with axial length greater than 24 mm. Methods: Retrospective case series. This study comprised 117 (234 eyes) age-related cataract patients. There were 51 men (43.59%) and 66 women (56.41%) with mean age of (69.0±8.7) years (range from 52.0 to 85.0 years). The average axial length was 27.6±1.8 (range from 24.2 to 31.9 mm). We devided them into four groups according to the axial length. A-scan was used to measure the axial length and Pentacam was used to get the corneal curvature and corneal spherical aberration of both anterior and posterior surface. kolmogorov-smirnov test was used to check the normal distribution. ANOVA test was used to compare eachcorneal parameter among different groups. Pearson correlation analysis was used to obtain the correlation of corneal parameters in groups. Results: There were correlations between the axial length and the anterior and posterior corneal curvature (r=-0.213, r=0.174, respectively, P<0.05). No correlation was found between the axial length and anterior or posterior corneal spherical aberration (r=-0.114, 0.055, respectively, P>0.05). Mean values of corneal anterior surface curvature were (45.26±1.60) D (group 1), (44.17±1.45) D (group 2), (44.40±1.99)D (group 3), and (44.53±1.69) D (group 4) respectively. Mean values of corneal posterior surface curvature were(-6.57±0.26)D (group 1), (-6.40±0.24)D (group 2), (-6.41±0.38)D (group 3), and (-6.43±0.26)D (group 4) respectively. There were significant difference of corneal anterior and posterior surface curvature among 4 groups (P=0.004, P=0.001). There was significant difference of corneal curvature of anterior surface in group 1 compared to group 2 and group 3(P<0.01, P=0.01). There was significant difference of curvature of posterior surface in group 1 compared to group 2 and group 3, respectively (P<0.01). Mean values of anterior surface corneal spherical aberration were (2.09±0.53) μm (group 1), (1.90±0.44) μm (group 2), (2.00±0.74) μm (group 3), and (1.78±0.52) μm (group 4) respectively. Mean values of posterior surface corneal spherical aberration were (2.69±1.15) μm (group 1), (2.46±1.16) μm (group 2), (2.92±2.51) μm (group 3), and (2.69±1.13) μm (group 4) respectively. No correlation was found in anterior and posterior surface corneal spherical aberration(P>0.05) among different groups. Conclusions: The eye with a longer axial length have a flatter cornea. Cornea fails to compensate for axial length elongation when the axial length is longer than 28mm. The corneal spherical aberration varies among individuals, which suggests us to do the customized measurement before cataract surgery to make a decision on choosing the aspherical intraocular lens. (Chin J Ophthalmol, 2017, 53: 255-259).

Comparison of IOL refractive power caculation using different apparatus and various formulas in cataract eyes with silicon oil tamponade

Background Silicon oil tamponade eyes following vitrectomy accelerate and induce lens opacification, so the accurate measurement and calculation of intraocular lens (IOL) diopter before cataract extraction+ IOL implantation is very important for the recovery of visual function. Objective This study was to compare the differences of IOL powers measured and calculated by different apparatus and different IOL power formulas before cataract extraction+ IOL implantation silicon oil tamponade combined with cataractous eyes. Methods A prospective, consecutive, nonrandomized study was performed.Thirty-six silicon oil tamponade with cataract eyes of 36 patients were included in the Second Affiliated Hospital of Soochow University from August 2011 to October 2013.Patients with silicone oil emulsification for 4 months to 2 years prepared to treat by cataract extraction+ IOL implantation+ silicon oil removal.Axial length (AL), corneal curvature (CC) and anterior chamber depth (ACD) were measured with IOLMaster and A-scan with manual kerameter (MK) in the eyes for the prediction of IOL power by SRK-Ⅱ, SRK/T, Hoffer Q, Holladay 1 and Haigis formulas under the oral informed consent.The mean predictive error (MPE) and mean absolute refractive error (MAE) between predictive IOL diopters before operation and actual IOL diopters after operation were evaluated. Results The AL and ACD values measured by IOLMaster was (25.43±0.90)mm and (3.22±0.38)mm, which were significantly higher than (25.21±1.02)mm and (3.07±0.62)mm by A-scan+ MK respectively, the difference between the two measure methods was statistical significance(both at P=0.000). No significant difference was found in measured CC values between IOLMaster and A-scan+ MK ([44.58±1.57]D vs.[44.56±1.62]D) (P=0.568). When the parameters measured by IOLMaster were used, the MAE from SRK/T formula was smaller than that from SRK-Ⅱ, Hoffer Q, Holladay 1 and Haigis formulas (P=0.017, 0.009, 0.012, 0.001), and the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ, Hoffer Q and Holladay 1 formulas (P=0.026, 0.035, 0.021). When measured by A-scan+ MK, the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ, SRK/T, Hoffer Q and Holladay 1 formulas (P=0.007, 0.004, 0.018, 0.006). There was no significant difference in the number of eyes with MAE≤1.0 D between IOLMaster and A-scan+ MK measurements under the calculation of SRK-Ⅰ, SRK/T, Hoffer Q and Holladay 1 formulas (χ2=0.107, 2.250, 0.845, 0.084, all at P>0.05). However, the number of eyes with MAE≤1.0 D was significantly increased in IOLMaster measurement compared with A-scan+ MK under the calculation of Haigis formula (χ2=4.431, P=0.035). Conclusions In silicon oil-filled cataract eyes, SRK/T formula appears to have a more accurate predictive value of IOL power than that of other formulas when employ IOLMaster; when use A-scan+ MK measurement, the predictive value of IOL power seems to be better by using SRK-Ⅱ, SRK/T, Holladay 1 or Hoffer Q formulas. Key words: Biometry/instrumentation; Lens implantation, intraocular; Refraction, ocular/physiology; Algorithms; Cataract; Silicone oils/administration; Prospective studies

Changes in Ocular Parameters and Intraocular Lens Powers in Aging Cycloplegic Eyes

Age-related changes in lens elasticity and ciliary muscle contractility can affect how ocular parameters respond to cycloplegia, and therefore intraocular lens (IOL) power measurements calculated by formulas using anterior chamber depth (ACD), lens thickness (LT), or white-to-white (WtW) for effective lens position prediction can vary. In response, using swept-source optical biometry in prepresbyopic and presbyopic eyes, we investigated changes in ocular parameters and IOL power calculations attributable to cycloplegia. Cross-sectional study. In 38 prepresbyopic and 42 presbyopic eyes, we measured pupil diameter, radius of corneal curvature values, central corneal thickness, WtW, ACD, LT, and axial length both before and after cycloplegia. We determined IOL power calculations with the Sanders-Retzlaff-Kraff/theoretical, Holladay 2, and Haigis formulas. To pinpoint the effect of cycloplegia, we recorded refractive predictions in pre- and postdilation conditions according to the same IOL power calculations, even if postdilation IOL power calculations had changed. With cycloplegia, pupil diameter changed significantly more in presbyopic eyes (P < .001). Central corneal thickness decreased in prepresbyopic eyes (P= .048), whereas WtW increased in presbyopic eyes (P= .02). In both groups, ACD and LT changed significantly (P < .001). IOL power calculations according to the Holladay 2 formula differed in prepresbyopic eyes (P= .042), and refractive predictions with the Holladay 2 and Haigis formulas differed significantly in prepresbyopic eyes (P= .043 and P= .022, respectively). Surgeons should consider the effect of cycloplegia on refractive prediction errors and IOL power calculations determined with Haigis and Holladay 2 formulas, especially in prepresbyopic ages.

Change in corneal biomechanical properties and influence factors in population with myopia

Background Corneal refractive surgery has significant effects on corneal biomechanical properties.However, there are few study on large scale population with corneal biomechanical properties in the myopic population before corneal refractive surgery. Objective This study was to evaluate the change of corneal biomechanical properties and influence factors in myopic eyes using ocular response analyzer (ORA). Methods A prospective cohort study was carried out in Beijing Tongren Eye Center from April 2010 to January 2011.Corneal hysteresis (CH) and corneal resistance factor (CRF) were detected using ORA in 1 792 eyes of 896 myopic subjects who were going to receive corneal refractive surgery under the informed consent.According to different spherical equivalent (SE) the eyes were grouped into -0.25-<-3.0 D group, -3.0-<-6.0 D group, -6.0-<-9.0 D group, -9.0-<-12.0 D group, -12.0-<-15.0 D group and ≥-15.0 D group and according to different central corneal thickness (CCT), the eyes were grouped into <500 μm group, 500-<550 μm group, 550-<600 μm group and≥600 μm group.The CH value and CRF value in different SE groups or different CCT groups were compared, and the factors influencing CH and CRF were analyzed by Pearson correlation analysis. Results The mean CH and CRF value were (9.84±1.52)mmHg (1 mmHg =0.133 kPa) and (10.46±1.71)mmHg, respectively in the myopic eyes.The CH values were (10.35±1.53), (10.07±1.55), (9.81±1.46), (9.71±1.59), (9.35±1.55) and (9.23±1.28)mmHg in the -0.25-<-3.0 D group, -3.0-<-6.0 D group, -6.0-<-9.0 D group, -9.0-<-12.0 D group, -12.0-<-15.0 D group and ≥-15.0 D group, respectively, showing a significant difference among the groups (F=20.69, P<0.01), and the CH values in the -6.0-<-9.0 D group, -9.0-<-12.0 D group, -12.0-<-15.0 D group and ≥-15.0 D group were significantly lower than those in the -6.0-<-9.0 D group, -9.0-<-12.0 D group (all at P<0.01). There was no significant difference in the CRF values among different SE groups (F=0.65, P=0.49). CH and CRF values were increasing with the raise of CCT, with evidently differences among the CCT<500 μm group, 500 μm ≤CCT<550 μm group, 550 μm≤CCT<600 μm group and CCT≥600 μm group (CH: F=110.99, P<0.01; CRF: F=84.35, P<0.01), and the CH and CRF values were significantly higher in the 550 μm≤CCT<600 μm group and CCT≥600 μm group than those in the CCT<500 μm group (all at P<0.01). CH showed a positive correlation with SE (r=0.24, P<0.01), and no significant correlation between CRF and SE (r=0.03, P=0.20). The CH and CRF showed the positive correlations with the CCT (r=0.42, 0.57, both at P<0.01). In addition, CH and CRF values increased as the increases of SE, corneal curvature (CC) and CCT values, with the regression equation of CH=-7.87+ 0.08SE+ 0.16CC+ 0.02CCT (R2=0.26, P<0.01) and CRF=-11.42+ 0.14CC+ 0.03CCT (R2=0.34, P<0.01), respectively.The CH and CRF did not change with the age and gender in the subjects. Conclusions Corneal biomechanical properties including CH and CRF were positively correlated with CCT, CC and SE. Key words: Biomechanical phenomena/physiology; Cornea/physiopathology; Diagnostic techniques, ophthalmological/instrumentation; Elasticity/physiology; Refractive surgical procedures; Myopia; Humans

Therapeutic effect and safety of accelarated transepithelial riboflavin-ultraviolet corneal collagen crosslinking for keratoconus

Background Researches showed that classic corneal collagen crosslinking (CXL) can effectively control the progression of keratoconus and corneal ectasia, but its adverse responses and complications are common due to the de-epithelial procedure. A transepithelial riboflavin-ultraviolet CXL surgery has applied in ophthalmology, but its effectiveness and safety evaluation is less. Objective This study was to evaluate the effectiveness and safety of rapid transepithelial riboflavin-ultraviolet CXL for keratoconus. Methods A prospective self-controlled study was designed. Forty-six eyes of 28 keratoconus patients scheduled to receive the rapid transepithelial riboflavin-ultraviolet CXL in Beijing Tongren Hospital from March to October in 2014 under the approval of this hospital and informed consent with a follow-up duration for one year. The spherical equivalent (SE), astigmatic power, central corneal thickness (CCT), endothelial cell count, corneal topography parameters, the parameters from the anterior segment optical coherence tomography (AS-OCT) and corneal biomechanical parameters were examined before surgery and 1 week, 1 month, 3 months, 6 months and 12 months after surgery, and the results were compared among different time points to assess the effectiveness of transepithelial riboflavin-ultraviolet CXL for keratoconus. The postoperative irritation symptoms and adverse response were observed to evaluate the safety of surgery. Results No intraoperative complication and serious adverse postoperative infection were found in all the operated eyes. Slight irritation symptoms occurred in operated eyes 1 day after surgery and disappeared 3 days after surgery. A little reducing was seen in the spherical equivalent 1 month later, without significant difference among various time points (F=0.722, P=0.614). However, a significant reducing was found in astigmatic power in 12 months after surgery compared with before surgery (t =3.242, P=0.004). No considerably differences were seen in corneal endothelial cell (CEC) density, variation coefficient of CEC area and hexagonal CEC ratio among different time points (F=0.246, 0.465, 0.981; all at P>0.05). The corneal thickness values in postoperative 3 and 6 months were (467.86±52.92)μm and (468.51±52.96)μm, which were insignificantly higher than (453.91±45.78)μm in preoperation (t=0.236, 0.469; both at P>0.05), however, the corneal thickness value in postoperative 12 months([488.67±51.44]μm) was significantly increased in comparison with preoperation (t=3.681, P=0.002). The maximal corneal curvature value (Ks), minimal corneal curvature value (Kf) and average corneal curvature value (Avek) were not significantly lower 3, 6 and 12 months after surgery than those before surgery (F=0.592, 0.897, 1.029, all at P>0.05). High reflective light band of corneal stroma was found in OCT images in 39 eyes (84.78%) with the mean depth of (214.38±31.92)μm. No significant differences were found in corneal hysteresis (CH) and corneal resistance factor (CRF) before and after surgery (F=1.268、0.894, both at P>0.05). Conclusions Rapid transepithelial riboflavin-ultraviolet CXL for keratoconus can increase corneal thickness, flatten corneal curvature and therefore arrest the development of keratoconus corneas. In addition, this therapy does not alter the shape and function of corneal epithelial and endothelial cells with mild irritation to eyes. Key words: [Key words] Keratoconus/drug therapy; Photochemotherapy/methods; Photosensitizing agents/therapeutic use; Riboflavin/therapeutic use; Ultraviolet rays; Biomechanics, corneal; Accelerated transepithelial riboflavin-ultraviolet corneal collagen crosslinking

Biomeasurement and analysis of the anterior chamber angle and related tissues in myopia eyes

Background Myopia is one of the main blinding diseases worldwide.At present, a lot of studies on ocular structure focus on the changes of corneal curvature（CC), central corneal thickness (CCT), anterior chamber depth (ACD), ocular axial length (AL) and choroid and retina, but the research of anterior chamber angle section structure form and ciliary body shape is lack. Objective This study was to measure and analyze the changes of the anterior chamber angle and related tissue structure in myopic eyes. Methods One hundred and forty-nine eyes of 149 subjects were included from May 2008 to May 2010 in Eighth Hospital of Qingdao City with the ages of 18-40 years old under the informed consent.The subjects were assigned to the emmetropia group (30 eyes) ([0.02±0.18]D), low myopia group(46 eyes) ([-1.64±0.69]D), moderate myopia group (35 eyes) ([-4.56±0.66]D) and high myopia group(38 eyes) ([-7.04±1.02]D). Conventional indexes including intraocular pressure (IOP), CCT, CC, AL and ACD were measured, and the indexes including chamber angel open distance (AOD), iris thickness (IT1, IT2, IT3), the position of ciliary body such as A-angel, B-angel, trabecular ciliary process distance (TCPD), iris-ciliary process distance (ICPD) and ciliary body thickness (CBT1, CBT2, CBT3) were measured by ultrasound biomicroscope（UBM). Results The IOP, CC and CCT values showed slight change in different groups without remarkable difference among them (all at P>0.05). As the increase of myopic degree, AL was extended and ACD was deepened, showing significant differences among the groups (both at P 0.05). However, the measuring values of angle opening degree (TIA and AOD500), ciliary position (A-angle, B-angle, TCPD, ICPD) and CBT (CBT1, CBT2, CBT3) elevated with the increase of myopic degree (all at P<0.05). Positive correlations were found between AOD500 and ACD, A-angle, CBT1, CBT2, AL, negative correlations was found between AOD500 and myopic degree（r=0.573, 0.513, 0.325, 0.398, 0.542, -0.435, all at P<0.01); Positive correlations were found between TIA and ACD, A-angle, CBT1, CBT2, AL, negative correlations was found between AOD500 and myopic degree（r=0.573, 0.464, 0.276, 0.410, 0.539, -0.435, all at P<0.01). Conclusions Within certain limits, as the increase of myopic degree, ACD deepens, the anterior chamber angle widens, ciliary process thickens and ciliary body backward shifts. Key words: Biometry; Myopia; Microscopy, acoustic; Axial length; Anterior chamber/ultrasonography; Ciliary body/ultrasonography; Anterior chamber angle/ultrasonography