Ocular Biometric Values and Prevalence of Corneal Astigmatism in Patients Candidate for Cataract Surgery.

Purpose: To analyze the biometric values and the prevalence of corneal astigmatism in cataract surgery candidates. Methods: This is a prospective study. Ocular biometric values and corneal keratometric astigmatism were measured by optical low-coherence reflectometry (Lenstar LS 900) before surgery in patients who were candidates for cataract extraction surgery. Descriptive measurements of biometric dimensions and keratometric cylinder data and their correlations with sex and age were evaluated. Results: Ocular biometric and keratometric values from 2084 eyes of 2084 patients (mean age 66.43, range 19-95 years) were analyzed. The mean values were as follows: corneal astigmatism 0.89 diopter (D), mean corneal keratometry 44.29 D, central corneal thickness 534 µ, internal anterior chamber depth (ACD) 3.11 mm, lens thickness 4.50 mm, and axial length 23.35 mm. Corneal astigmatism was <1.25 D in 1660 (79.5%) of eyes. Astigmatism was with-the-rule in 976 (46.8%) of eyes, against-the-rule (ATR) in 702 (33.7%), and oblique in 406 (19.5%). Analysis of corneal astigmatism revealed a change toward "ATR" with age which was not statistically significant. The ACD was correlated with age. The amount of corneal astigmatism had no correlation with age and sex. Conclusion: Corneal astigmatism was higher than 1.25 D in about 21% of cataract surgery candidates with slight differences between the various age ranges and had no correlation with age and sex.

Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus and Early Pellucid Marginal Degeneration.

PURPOSE: To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD). METHODS: It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1 week, 2 and 6 months. RESULTS: One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5 mm zones increased at 1 week (both P < 0.001) and then started to decrease up to 6 months. However, the corneal irregularity of PMD group had significant reduction only at 1 week in 5-mm zone (P = 0.02) and 2 months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively. CONCLUSION: Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

Long-Term Visual and Refractive Stability and Ocular Biometric Changes after Laser-Assisted Subepithelial Keratomileusis for Correction of Myopia: An 8-Year Follow-Up.

PURPOSE: To assess the long-term visual and refractive stability and ocular biometric changes in low to moderate myopic subjects treated by laser-assisted subepithelial keratomileusis (LASEK). METHODS: It is a prospective, interventional study. Included were 70 eyes of 35 patients who underwent LASEK for correction of ≤6 diopters (D) myopia. The uncorrected and corrected distance visual acuity (UDVA and CDVA), manifest refractions, and ocular biometric indices (by Lenstar-LS900, Haag-Streit AG, Koeniz, Switzerland) including keratometry, anterior chamber depth (ACD), aqueous depth (AD), axial length (AL), central corneal thickness (CCT), and lens thickness (LT) were assessed preoperatively and after 6 months and 8 years. RESULTS: Mean preoperative spherical equivalent was -3.99 (standard deviation [SD] =1.38) D which improved to 0.02 (SD = 0.27, P < 0.001) D and -0.10 (SD = 0.31, P < 0.001) D at 6 months and 8 years, respectively. The preoperative AL was not different from postoperative measures at 6 months (P = 0.15) and 8 years (P = 0.47). The ACD and AD decreased during 8 years, while LT increased (all P ≤ 0.001). The changes of LT inversely correlated with changes of ACD (rs = -0.67, P = 0.001 at 6 months and rs = -0.87, P < 0.001 at 8 years) and AD (rs = -0.76, P < 0.001 at 6 months and rs = -0.86, P < 0.001 at 8 years). The CCT and keratometry values reduced at 6 months postoperatively (all P < 0.001) and then did not change up to 8 years (0.21 ≤ P ≤ 0.87). CONCLUSIONS: The post-LASEK myopic regression is 0.1 D over 8 years. Ocular biometric values like keratometry, CCT, ACD, AD, and LT have been changed for a long period after LASEK in low to moderate myopia except AL.

Visual and Refractive Outcomes and Tomographic Changes after Femtosecond Laser-assisted Intrastromal Corneal Ring Segment Implantation in Patients with Keratoconus.

PURPOSE: To evaluate the visual, refractive, and tomography changes after femtosecond laser-assisted intrastromal corneal ring segment (ICRS; Intacs® SK) implantation in patients with keratoconus. METHODS: In this prospective interventional case series, Intacs SK ICRSs were inserted using a femtosecond laser into eyes with stage I-IV keratoconus. Visual, refractive, and corneal tomography changes, along with surgical complications, were analyzed 1 week, 2 months, and 6 months postoperatively. RESULTS: The study evaluated 71 eyes of 52 patients (mean age: 27.5 years). Six months postoperatively, the spherical equivalent, mean sphere, and mean cylinder were decreased by 2.07, 1.47, and 1.13 diopters (D), respectively. The mean preoperative uncorrected distance visual acuity (UDVA) increased from 0.87 ± 0.26 to 0.46 ± 0.19 LogMAR and the mean preoperative corrected distance visual acuity (CDVA) increased from 0.55 ± 0.21 to 0.28 ± 0.17 LogMAR (P < 0.001). Flat and steep keratometry decreased by a mean corneal power in the 3-mm zone, and mean anterior elevation decreased by 0.91 D, 2.52 D, and 1.03 microns (P < 0.001), respectively. Among all eyes, 93.0% gained one or more lines of CDVA. Mean internal anterior chamber depth decreased from 3.25 ± 0.33 to 3.14 ± 0.45 mm (P = 0.001), and mean irregularity in the 3-mm zone decreased from 5.63 ± 1.71 to 5.24 ± 1.82 (P = 0.006). However, mean posterior elevation and irregularity in the 5-mm zone did not change significantly. CONCLUSION: Implantation of one or two Intacs SK segments is safe and effective to treat keratoconus, leading to significant improvement in UDVA, CDVA, and refractive error.

Adjustment formulae to improve the correlation of white-to-white measurement with direct measurement of the ciliary sulcus diameter by ultrasound biomicroscopy.

PURPOSE: This study evaluates the correlation between horizontal white-to-white (WTW) distance using Caliper and Orbscan IIz with the ciliary sulcus diameter measured by high frequency ultrasound biomicroscopy (UBM) and presents an adjustment formula to improve the correlation. METHODS: We measured horizontal sulcus-to-sulcus (STS) dimension of 273 right eyes of 273 high myopic patients with 35 MHz UBM and horizontal WTW using Orbscan IIz and Caliper. Mean WTW diameter, differences, and the correlation of measurement methods were evaluated. RESULTS: The mean spherical equivalent was -8.79 ± 4.87 diopters. Mean horizontal STS dimension with UBM was 12.13 ± 0.45 mm (range, 10.81-13.42 mm). Mean WTW diameter in the Caliper method was 11.70 ± 0.40 mm (range, 10.6-12.8 mm) and 11.70 ± 0.40 mm (range, 10.5-13.1 mm) in the Orbscan method. Mean difference of UBM STS and WTW with Caliper was 0.48 ± 0.28 mm (range, -0.19 to 1.37 mm). Mean difference of UBM STS diameter and Orbscan WTW was 0.38 ± 0.31 mm (range, -0.64 to 1.29 mm). The Pearson correlations of WTW diameter measured by Caliper and Orbscan with UBM's STS diameter were 0.778 and 0.773, respectively. This difference diminished after adjustment. The 95% limit of agreement was almost the same in Caliper and Orbscan (-0.07 to 1.03 compared with -0.23 to 0.99). CONCLUSION: There is a significant difference in measurements between STS diameter using UBM and WTW diameter utilizing Caliper and Orbscan. This difference diminished after our recommended adjustment.

Ocular higher-order aberrations changes after implantable collamer lens implantation for high myopic astigmatism.

PURPOSE: To investigate the changes in higher-order aberrations (HOAs) induced by the implantation of implantable collamer lenses (ICLs) and Toric ICL (TICL) in eyes with high myopia and high myopic astigmatism. METHODS: We investigated 33 eyes of 18 consecutive patients (in a prospective, interventional case series study), with spherical equivalent errors of -6.00 to -21.09 diopters (D) and cylindrical errors of -0.5 to -4.75 D, who underwent ICL and TICL implantation. Before and after 5 days, 2 and 6 months of surgery, the uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), defocus and adverse events of the surgery were assessed. Ocular HOAs were also evaluated by Hartmann-Shack aberrometry (Technolas PV, Rochester, New York, USA) before and after 6 months of surgery. RESULTS: At 6.0 months after surgery, the UCVA and BCVA in 40% and 66.7% of eyes were 20/20, respectively. Mean defocus refraction and astigmatism was reduced to -0.66 and 0.65 D from -12.79 and 2.18 at baseline, respectively. For a 6 mm pupil, HOAs were not significantly changed, merely from 0.417 ± 0.162 µ before surgery to 0.393 ± 0.119 µ after surgery (P = 0.45). Spherical aberration (Z400) increased significantly (P = 00.0). Surgical induced astigmatism was lower than 0.25 D, and there were no changes in trefoils and coma aberration. No vision-threatening complications occurred during the observation period. CONCLUSION: This study shows that the ICL and TICL performed well in correcting high myopic astigmatism without significant changes in HOAs during a 6-month observation period, although the spherical aberration (Z400) increased significantly.

Long-term outcomes of posterior chamber phakic intraocular lens implantation in keratoconus.

BACKGROUND: In this retrospective observational case series study, the aim was to evaluate the long-term safety, efficacy, stability and predictability of posterior chamber phakic intraocular lens (pIOL) implantation to correct myopia and myopic astigmatism associated with keratoconus. METHODS: Uncorrected distance visual acuity (UDVA), best spectacle-corrected distance visual acuity (BSCDVA), refraction and adverse effects were evaluated in 23 keratoconic eyes of 13 patients after five years with Visian ICMV4 pIOL (STAAR Surgical). RESULTS: The mean pre-operative spherical equivalent and cylinder changed from -5.35 ± 2.82 D and -3.14 ± 1.58 D to -0.78 ± 1.31 D and -1.56 ± 1.53 D, respectively, five years post-operatively. Before the surgery the mean Snellen decimal BSCDVA was 0.60 ± 0.20. The mean UDVA and BSCDVA changed to 0.74 ± 0.22 and 0.88 ± 0.16, respectively. A total of 82.5 per cent of eyes achieved 6/12 or better UDVA post-operatively. The mean safety and efficacy indices were respectively, 1.47 ± 0.32 and 1.24 ± 0.34. No eye lost a line of visual acuity and 19 eyes gained one or more lines. An endothelial cell loss of 7.88 per cent occurred. No significant changes were seen in intraocular pressure, steep, flat and mean keratometry. The crystalline lens was clear. CONCLUSION: The clinical outcomes of the current study demonstrate the safety, efficacy and predictability of the implantable collamer lens (toric and non-toric) in the correction of myopia and myopic astigmatism associated with keratoconus. The patients' refractions achieved early stability and remained stable during the course of the study.