Comparison of transepithelial and conventional photorefractive keratectomy in myopic and myopic astigmatism patients: a randomized contralateral trial.

BACKGROUND: To assess transepithelial photorefractive keratectomy (tPRK) in terms of corneal epithelial healing rate, postoperative pain, postoperative discomfort, and visual and refraction outcomes compared to mechanical epithelial debridement PRK (mPRK) and alcohol-assisted PRK (aaPRK). METHODS: In this double-masked, randomized clinical trial, thirty-nine patients underwent tPRK in one eye and mPRK in the fellow eye (arm A), and 33 patients underwent tPRK in one eye and aaPRK in the contralateral eye (arm B). All surgical procedures were done using the Schwind Amaris excimer laser. The area of corneal epithelial defect in all eyes was captured and analyzed using ImageJ software. RESULTS: Mean epithelial healing time was respectively 3.74 ± 0.82 and 3.59 ± 0.79 days in tPRK versus mPRK (P = 0.21) in arm A, and 3.67 ± 0.92 and 3.67 ± 0.74 days in tPRK versus aaPRK (P = 1.00) in arm B. Accounting for the initial corneal epithelial defect area, the epithelial healing rate was faster in conventional PRK groups compared to tPRK (both P<0.001) in both arms. However, there was no significant difference in safety, efficacy, spherical equivalent refractive accuracy, or corneal haze development between tPRK and conventional PRK groups (all P > 0.05). CONCLUSIONS: All three methods are effective in terms of visual and refractive outcomes. However, although time to complete re-epithelialization was similar with the three methods, the epithelial healing rate was faster in conventional PRK considering the initial corneal epithelial defect area, and the patients experienced less pain and discomfort in the first postoperative day. TRIAL REGISTRATION: IRCT, IRCT20200317046804N1 . Retrospectively registered 5 May 2020.

Matched comparison of corneal higher order aberrations induced by SMILE to femtosecond assisted LASIK and to PRK in correcting moderate and high myopia: 3.00mm vs. 6.00mm.

BACKGROUND: The refractive surgeries induce corneal higher order aberrations (C-HOAs). In this study, change of C-HOAs after small-incision lenticule extraction (SMILE) compared to femtosecond assisted laser in situ keratomileusis (femto-LASIK), and to photorefractive keratectomy with mitomycin-C (PRK) under photopic and mesopic conditions. METHODS: In this prospective study, age, gender, and apical corneal thickness (ACT) matched cases with moderate myopia [spherical equivalent (SE) 3.00 to 6.00D) to high myopia (SE > 6.00D)] were enrolled. In addition to visual acuity and refraction, total C-HOA, coma, spherical aberration (SA), and trefoil in the 3- and 6-mm zones were measured before and 3 and 6 months after surgery. RESULTS: Overall, 372 moderate myopia cases (124 eyes of 124 individuals in each surgical group) and 171 high myopia cases (57 eyes of 57 individuals in each surgical group) were enrolled. At baseline, the differences in age, gender, ACT, uncorrected and corrected visual acuity, and SE were not statistically significant between subgroups of surgical methods within each myopia group (all P > 0.05). At 12 months, in the moderate myopia group, there was less increase in 6-mm zone total C-HOA, coma, and SA with SMILE compared to the other groups (all P < 0.05). In the high myopia group, there was greater increase in photopic total C-HOA and trefoil and less increase in mesopic SA with SMILE (all P < 0.05). CONCLUSIONS: In correction of moderate myopia, SMILE has better results in mesopic condition. In high myopia correction, femto-LASIK and PRK have better results in photopic and SMILE in mesopic condition.

The efficacy of standard versus accelerated epi-off corneal cross-linking protocols: a systematic review and sub-group analysis.

PURPOSE: To compare the one-year efficacy of accelerated and standard 5.4 J/cm2 protocols of cross-linking (CXL) in the treatment of progressive keratoconus. METHODS: In this systematic review, two members of the research team searched Scopus, Pubmed, ISI, Ovid, Science Direct, and Cochrane databases independently for publications between January 2010 and December 2016. The majority of retrieved studies were not randomized clinical trials (RCT), or the second arm of the RCT was either untreated or customized CXL. The outcomes of interest were uncorrected distance visual acuity, corrected visual acuity, manifest refraction spherical equivalent, maximum keratometry in the central 3 mm, minimum keratometry in the central 3 mm, and corneal thickness in the apex or thinnest point at baseline and 1 year after CXL. RESULTS: Of the 453 papers found in the preliminary search, 23 papers were included in the final analysis. Analysis of variance of one-year changes showed that longer irradiation times were associated with a greater corneal flattening effect, although there was no difference in terms of improvement in vision or refraction. CONCLUSIONS: In other words, efficacy is comparable among different CXL protocols, so it is recommended to use the standard method in cases where maximum flattening is expected, such as young people and severe cases.

Photopic, Mesopic, and Scotopic Visual Acuity After 18 mW/cm2 Accelerated Corneal Cross-Linking.

OBJECTIVES: One-year changes in uncorrected (UDVA) and corrected (CDVA) distance visual acuity under different lighting conditions after accelerated cross-linking (CXL) in patients with progressive keratoconus in comparison with nontreated cases. METHODS: In this nonrandomized clinical trial, the sample included 50 eyes in the CXL group and 40 eyes in the control group. Visual acuity was tested under photopic (100 lux), mesopic (20 lux), and scotopic (0.5 lux) lighting conditions at 6 months and 1 year. RESULTS: Changes in all studied variables were similar in the two groups (all P>0.05) after adjusting for age, but the 0.02±0.17 logMAR reduction in scotopic UDVA in the CXL group showed a difference of marginal significance compared with the control group (P=0.061). In cases with baseline UDVA≤20/40, 1-year adjusted results in the CXL and control groups were, respectively, 0.61±0.34 and 0.83±0.35 logMAR for photopic UDVA (P=0.021), 0.48±0.22 and 0.68±0.27 logMAR for mesopic UDVA (P=0.033), and 0.21±0.14 and 0.26±0.07 logMAR for mesopic CDVA (P=0.056). In those with baseline UDVA greater than 20/40, 1-year adjusted results in the CXL and control groups were, respectively, 0.12±0.20 and 0.06±0.10 logMAR for mesopic UDVA (P=0.034) and 0.15±0.18 and 0.07±0.06 logMAR for scotopic UDVA (P=0.024). Other vision indices showed no significant intergroup differences (all P>0.05). CONCLUSION: Poor vision (UDVA≤20/40) keratoconus cases are more likely to achieve improved vision or a halt in its deterioration after CXL. In cases with good vision (UDVA>20/40), however, although further photopic vision impairment is halted, they may experience worse vision under mesopic and scotopic conditions.

Femtosecond laser-assisted LASIK versus PRK for high myopia: comparison of 18-month visual acuity and quality.

PURPOSE: To compare 18-month outcomes between femtosecond laser-assisted LASIK (femto-LASIK) and photorefractive keratectomy with mitomycin-C (PRK-MMC) for myopia of more than 7.0 D in terms of visual acuity and quality. METHODS: In this comparative nonrandomized clinical trial, 60 eyes from 30 patients (30 eyes in each group) were enrolled. The two procedures were compared in terms of 18-month changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, ocular and corneal higher order aberrations (HOAs), and contrast sensitivity (CS). RESULTS: Mean myopia was -8.65 ± 1.51 and -8.04 ± 1.70 D (P = 0.149) and mean ablation depth was 109.37 ± 9.07 and 105.09 ± 12.59 µm (P = 0.138), in the femto-LASIK and PRK-MMC groups, respectively. Baseline parameters were not significantly different between the two groups (all P > 0.05). At 18 months postoperatively, 75 % in the femto-LASIK, versus 57.1 % in the PRK-MMC group, had 20/20 UDVA (P = 0.017). CDVA remained similarly unchanged in both groups (P = 0.616). No case had residual refractive error more than 1.0 D in the femto-LASIK group, while 33.5 % in the other group had more than 1.0 D residual error (P = 0.390). Changes in corneal HOA were not significantly different between the two groups (P = 0.260). Cases in the femto-LASIK group showed more increase in ocular HOA (P = 0.032) and coma (P = 0.083, power = 72 %). CS remained similarly unchanged in all spatial frequencies in both groups (all P > 0.05). CONCLUSION: Although femto-LASIK induces more HOA compared to PRK-MMC, considering outcomes in terms of 20/20 UDVA, residual refractive error, and CS stability, femto-LASIK provides more favorable results than PRK-MMC in high myopia.

The location of incision in cataract surgery and its impact on induced astigmatism.

PURPOSE OF REVIEW: The purpose of the present study is a systematic review of previous studies on choosing the best incision site for the correction of astigmatism in cataract surgery and assessing the amount of surgically induced astigmatism (SIA) with each approach. RECENT FINDINGS: Regardless of astigmatism axis, studies show that using an on-axis incision is associated with favorable results for 0.5-1.0 diopter (D) of astigmatism. In cases with more than 1.0 D astigmatism, paired on-axis incisions can be appreciably efficient in astigmatism correction and cause at least 1.5 D SIA. Considering the amount of SIA, a temporal incision is the best approach when the patient has minimal amounts of corneal astigmatism preoperatively. At higher levels of astigmatism, if no other astigmatism correction method is used simultaneously, the temporal incision is used less frequently; however, since it is associated with the least SIA, it is still the choice site when another correction method is used. SUMMARY: The temporal incisions in cataract surgery are associated with little SIA and are appropriate choices for mild preoperative astigmatism. At higher levels of preoperative astigmatism, superior incisions are associated with better results when combined methods are not applied.

Femtosecond-Assisted LASIK Versus PRK: Comparison of 6-Month Visual Acuity and Quality Outcome for High Myopia.

OBJECTIVE: To compare the results of femtosecond-assisted laser in situ keratomileusis (femto-LASIK) and photorefractive keratectomy with mitomycin C (PRK-MMC) for the correction of myopia more than 7.0 diopters (D). METHODS: In this comparative nonrandomized trial, 60 eyes (30 eyes in each group) were enrolled. Patients were tested for uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, ocular and corneal aberrations, and contrast sensitivity (CS) before surgery and at 3 and 6 months postoperatively. RESULTS: Mean preoperative myopia was -8.65±1.51 and -8.04±1.70 D in the femto-LASIK and PRK-MMC groups, respectively (P=0.149). Intergroup differences in baseline indices were not statistically significant. At 6 months after surgery, UDVA showed an improving trend, but it was better in the femto-LASIK group (P=0.026). CDVA in the two groups remained similarly unchanged (P=0.170). For the femto-LASIK and PRK-MMC groups, the safety indices were 1.01±0.05 and 1.01±0.14 (P=0.949), respectively, and the efficacy indices were 0.99±0.07 and 0.93±0.22 (P=0.192), respectively. Comparing CS, only CS18 showed a significantly greater decrease in the femto-LASIK group compared with the PRK-MMC group (P=0.016). Intergroup differences were not statistically significant in other spatial frequencies. Changes in the ocular and corneal higher order aberrations were not statistically different between the two groups except ocular coma, which increased in the femto-LASIK group (P=0.041). CONCLUSION: Femto-LASIK improves UDVA better than PRK-MMC in high myopia. However, because of increased coma, the quality of vision is reduced. In other words, visual acuity outcome is better with femto-LASIK and visual quality outcome is better with PRK-MMC.

Matched comparison study of total and partial epithelium removal in corneal cross-linking.

PURPOSE: To compare the 1-year results of total versus partial epithelium removal in corneal cross-linking in the treatment of progressive keratoconus. METHODS: This retrospective study compared the results of total (the total group) versus partial (the partial group) approaches of epithelium removal in corneal cross-linking. Eighty eyes of 65 patients (40 eyes in each group) were enrolled. The mean age of the participants was 25.48 ± 4.80 years and 62.5% were male. One-year changes in vision parameters, refraction, and Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) indices were compared between the two groups using repeated measures analysis of variance. RESULTS: One year after corneal cross-linking, uncorrected distance visual acuity in the total and partial group improved by 0.13 ± 0.42 and 0.12 ± 0.36 logMAR (P = .447), respectively, and corrected distance visual acuity improved by 0.00 ± 0.19 and 0.13 ± 0.20 logMAR (P = .001), respectively. Spherical equivalent decreased by 0.44 ± 1.25 diopters (D) in the total group and 0.56 ± 1.47 D in the partial group (P = .710). The decrease in maximum keratometry was 0.39 ± 0.93 and 0.01 ± 0.95 D in the total and partial group, respectively (P = .037), and the decrease in mean keratometry was 0.42 ± 0.93 and 0.00 ± 0.65 D (P = .015), respectively. Central corneal thickness decreased by 18.39 ± 20.66 µm in the total group and 0.11 ± 13.29 µm in the partial group (P < .001). CONCLUSIONS: One year after corneal cross-linking, both approaches showed similar results in terms of uncorrected distance visual acuity. With the partial approach, there was slightly better corrected distance visual acuity improvement and central corneal thickness maintenance, but slightly better corneal flattening was achieved with the total removal. Long-term studies are needed to compare these two approaches in terms of stability of results and stopping the progression of keratoconus.

Femtosecond-assisted intrastromal corneal single-segment ring implantation in patients with keratoconus: a 12-month follow-up.

OBJECTIVE: To determine visual rehabilitation in patients with keratoconus who received femtosecond-assisted intrastromal corneal single-segment ring implantation. METHODS: This prospective study was conducted on 62 eyes of 45 patients with keratoconus who received single-segment Intacs. The FS200 femtosecond laser was used for tunnel creation. Patients were examined for astigmatism, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and manifest refraction spherical equivalent (MRSE) before the operation and 1, 6, and 12 months after operation. Scheimpflug imaging including minimum keratometry reading (min-K), maximum keratometry reading (max-K), average of minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), asphericity (Q-value), index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), center keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD), and minimum sagittal curvature (Rmin) was performed before and 12 months after the operation. RESULTS: The mean preoperative UCVA was 20/130, which increased to 20/62 1 year after the operation (P < 0.001). The mean BCVA in the last follow-up was 20/32, which improved when compared with preoperative BCVA (20/40) (P = 0.008). One year after the operation, MRSE and cylinder decreased to 1.33 ± 1.90 diopter (D) and 0.46 ± 1.50 D, respectively (P < 0.001 for both). Min-K, max-k, and mean-k reduced to 1.67 ± 0.1.40 D, 2.08 ± 1.84 D, and 1.85 ± 1.30 D (P < 0.001 for all). Q-value decreased to 0.81 ± 1.14 (P < 0.001). In contrast, CKI had a significant increase of 0.02 (P = 0.002). Other evaluated indexes did not show any significant differences. CONCLUSION: Implantation of the single-segment ring in patients with keratoconus improved vision because of regularizing the cornea and centralization of the corneal cone.

The prevalence of keratoconus in a young population in Mashhad, Iran.

PURPOSE: To determine the prevalence of keratoconus and some associated factors in the students of Mashhad University of Medical Sciences, Iran. METHOD: In this cross sectional study, multistage cluster sampling was used to select the participants. All participants underwent retinoscopy, slit lamp examination, topography with the TMS-4 and corneal assessment with the Orbscan II. The diagnosis of keratoconus was based on both clinical evidence and the results of corneal imaging. RESULTS: Of 1280 selected students, 1073 agreed to participate in the study, and of those who agreed, 1027 fulfilled the inclusion criteria. 42.5% of the study population was male with a mean age of 26.1 ± 2.3 years. The prevalence of keratoconus was 2.5% (n = 26) (95% confidence interval, CI 1.6-3.5). Eighteen students (69%) had bilateral keratoconus. Imaging of the cornea revealed that 70% of the keratoconics had nipple cones and the remaining had asymmetric bow-tie patterns. The prevalence of keratoconus was not significantly associated with age or gender (p > 0.05). In a multiple logistic regression model, family history (OR = 11.4, 95% CI: 2.5-51.3) and eye rubbing (OR = 6.3, 95% CI: 1.6-24.3) were significantly correlated with keratoconus. CONCLUSIONS: These results taken together with recent studies in the area suggest that keratoconus may have a higher prevalence in the Middle East and Asia than in Western Countries.

Analysis of superoxide dismutase 1, dual-specificity phosphatase 1, and transforming growth factor, beta 1 genes expression in keratoconic and non-keratoconic corneas.

PURPOSE: To quantitatively assess the superoxide dismutase 1 (SOD1), transforming growth factor, beta 1 (TGF-ß1), and dual-specificity phosphatase 1 (DUSP1) messenger ribonucleic acid (mRNA) expression levels as the main intracellular reactive oxygen species neutralizers, wound healing mediators, and immunomodulators (respectively) in keratoconic (KCN) and non-KCN corneas. METHODS: Total RNA was extracted from normal and keratoconic cultured corneal stromal fibroblasts. Semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) was used to measure the relative expression levels of mRNAs of the SOD1, TGF-ß1, and DUSP1 genes. RESULTS: The mRNA expression of TGF-ß1 and DUSP1 was augmented in the KCN corneas (three- and fivefold, respectively; both p<0.05). The KCN and non-KCN samples showed no difference in comparative SOD1 mRNA levels. CONCLUSIONS: This study demonstrated a higher level of DUSP1 and TGF-ß1 expression as known molecules in the inflammatory process. These results may provide new insight into the complex molecular pathways underlying KCN for investigating other inflammatory molecules.

Corneal collagen cross-linking with riboflavin and ultraviolet a irradiation for keratoconus: long-term results.

PURPOSE: To evaluate the long-term results of corneal collagen cross-linking (CXL) in patients with progressive keratoconus. DESIGN: Prospective case series. PARTICIPANTS: This study was conducted on 40 eyes of 32 patients with progressive keratoconus between 2006 and 2012. METHODS: Patients underwent CXL no later than 1 month after baseline examinations. For CXL, ultraviolet irradiation was applied for 30 minutes, during which riboflavin instillation was repeated every 3 minutes. MAIN OUTCOME MEASURES: Patients were tested for best-corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), manifest refraction spherical equivalent (MRSE), and Scheimpflug imaging from which we extracted maximum keratometry reading (max-K), average of minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), and anterior and posterior elevation at the apex at baseline, at 1, 3, 6 months after CXL, and 1, 2, 4, and 5 years later. We studied results at 5 years after CXL as well as the trend of changes over the 5-year period. RESULTS: Mean UCVA was 0.67 ± 0.52 logarithm of the minimum angle of resolution (logMAR) at baseline and 0.65 ± 0.51 logMAR at 5 years after the procedure. For mean BCVA, these values were 0.31 ± 0.28 and 0.19 ± 0.20 logMAR, respectively (P = 0.016). The mean MRSE changed from -3.18±2.23 diopters (D) to -2.77 ± 2.18 D, and mean refractive cylinder error changed from -3.14 ± 2.22 to -2.49 ± 1.71 D (P = 0.089). Mean max-K and mean-K decreased by 0.16 ± 2.20 and 0.10 ± 1.69 D, respectively. The CCT increased from 483.87 ± 29.07 to 485.95 ± 28.43 µm. Mean anterior elevation at the apex changed from 13.9 2 ± 8.28 to 11.45 ± 8.18 µm (P = 0.030) and posterior elevation at this point changed from 29.54 ± 18.39 to 26.34 ± 19.59 µm. The mean-K, max-K, UCVA, and astigmatism showed no change over time during these 5 years. After the first year, BCVA, MRSE, and CCT showed no change and stabilized, whereas elevation readings continued to decrease up to 5 years after CXL. CONCLUSIONS: Based on our 5-year results, treatment of progressive keratoconus with CXL can stop disease progression, without raising any concern for safety, and can eliminate the need for keratoplasty. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

The association between residual astigmatism and refractive errors in a population-based study.

PURPOSE: To examine the relationship of spherical equivalent (SE) with refractive, corneal, and residual astigmatism. METHODS: Using stratified cluster sampling, 6,311 individuals were invited and 82.2% participated in this study. Examinations including uncorrected and corrected distance visual acuity tests, refraction, slit-lamp examination, and funduscopy were performed for all participants. Refraction and keratometry were used to calculate refractive and corneal astigmatism, respectively, and their difference was regarded as residual astigmatism. RESULTS: Refractive astigmatism showed a U-shaped relationship with SE; with every diopter (D) increase in astigmatism, the SE increased by 0.230 D in hyperopes and 0.664 D in myopes (P < .001). With every 1.0 D increase in residual astigmatism, the SE showed 0.376 D myopic shift in myopes (P = .004) and 0.077 D hyperopic shift in hyperopes (P = .224). Mean SE was highest among cases of with-the-rule (WTR) astigmatism (P < .001). Cases of high myopia and high hyperopia mostly had WTR and most emmetropes had against-the-rule (ATR) refractive astigmatism. Residual astigmatism was mostly WTR in emmetropic cases; at higher levels of SE error in myopes and hyperopes, WTR residual astigmatism decreased, whereas ATR and oblique residual astigmatism increased. CONCLUSIONS: Increases in SE are associated with higher levels of refractive and residual astigmatism among myopic and hyperopic cases. Unlike refractive astigmatism, WTR residual astigmatism was mostly seen in near emmetropic individuals.

The distribution of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth in an adult population of Shahroud, Iran.

BACKGROUND: Ocular biometric parameters can be influenced by race, ethnicity, and genetics; their differences across different populations can probably explain differences in refractive errors in these populations. The aim of this study is to determine the normal range of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth in the population of Shahroud in the north of Iran. METHODS: In the first phase of Shahroud Eye Cohort Study, the 40-64 year old population were sampled cross-sectionally; 6311 were invited and 5190 (82.2%) participated in the study. Biometric examinations were done using the LENSTAR/BioGraph (WaveLight AG, Erlangen, Germany) after vision tests and before cycloplegic refraction tests. Any type of eye surgery, extensive pterygium, and lack of cooperation were used as exclusion criteria, and analyses were done with data from 4869 eyes. RESULTS: We found a mean axial length of 23.14 mm (95% confidence interval [CI], 23.11-23.17), mean anterior chamber depth of 2.62 mm (95% CI, 2.60-2.63), mean lens thickness of 4.28 mm (95% CI, 4.27-4.29), and the mean vitreous chamber depth was 15.72 mm (95% CI, 15.70-15.75).Kolmogorov-Smirnov tests showed that the distribution of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth significantly differed from normal; axial length and vitreous chamber depth demonstrated a leptokurtic distribution as well.Axial length, anterior chamber depth, and vitreous chamber depth significantly decreased with age, and lens thickness significantly increased with age (p < 0.001). All indices were significantly higher in men. CONCLUSIONS: The distributions of axial length, vitreous chamber depth, and lens thickness are reported for the first time in an Iranian adult population. Compared to other studies, axial length was in the mid range, nonetheless, studying axial length components showed that the Iranian population had smaller anterior chamber depth and lens thickness. Age and gender were significantly associated with all indices assessed in this study.

Biometry and intraocular power calculation using a swept-source optical coherence tomography: A repeatability and agreement study.

Purpose: To evaluate the repeatability of biometry and intraocular lens (IOL) power using Galilei G6 and to determine the agreement of its measurements with those of IOL Master 700 and IOL Master 500. Methods: Hundred mature cataract eyes were examined twice with Galilei G6 and the results were compared with those of other two devices. Axial length (AL), minimum (K1), maximum (K2), and mean keratometry, anterior chamber depth (ACD), white-to-white (WTW) diameter, lens thickness (LT), and the calculated IOL power were the studied parameters. The correlation coefficient, within-subject standard deviation (Sw), Bland-Altman method, and 95% limits of agreement (LoA) were used for statistical analysis. Results: The intraclass correlation coefficient (ICC) was above 0.9 for all indices, and the LoA ranged from a minimum of 0.08 mm for AL to a maximum of 0.50 D for K1. Sw also ranged between a minimum of 0.02 for AL, ACD, and WTW and a maximum of 0.13 for K1. In the Galilei G6-IOL Master 700 pair, the narrowest and widest LoA were calculated for AL (0.07 mm) and K2 (0.49 D), respectively. In the Galilei G6-IOL Master 500 pair, the narrowest and widest widths of LoA were calculated for AL (0.17 mm) and K2 (0.92 D), respectively. In the first pair, the LoA of IOL power (0.57 D) were the best for Haigis formula and in the second pair, the best agreement (LoA: 0.35 D) was observed for Holladay-1. Conclusion: Galilei G6 provided repeatable biometric measurements. The agreement between biometry and IOL power calculation was better in the Galilei G6-IOL Master 700 pair compared to the Galilei G6-IOL Master 500.

Mutation analysis of VSX1 and SOD1 in Iranian patients with keratoconus.

PURPOSE: To evaluate mutations in the visual system homeobox gene 1 (VSX1) and superoxide dismutase 1 (SOD1) genes with keratoconus (KTCN), direct sequencing was performed in an Iranian population. METHODS: One hundred and twelve autosomal dominant KTCN patients and fifty-two unaffected individuals from twenty-six Iranian families, as well as one hundred healthy people as controls were enrolled. Genomic DNA was extracted from whole blood sample. Then to study the possible linkage between KTCN and six known loci linkage analysis was performed using 12 short tandem repeat (STR) markers. Also, the entire coding region and intron-exon boundaries of VSX1 and SOD1 were amplified by the PCR technique in each proband. Subsequently, PCR products were subjected to direct sequencing. Co-segregation analysis of the identified mutation was conducted in the family members. An Amplification Refractory Mutation System PCR (ARMS-PCR) was additionally employed for detection of the identified mutation in healthy controls. RESULTS: Linkage analysis of aforementioned loci did not detect evidence for linkage to KTCN. Direct PCR sequencing revealed two single nucleotide polymorphisms (SNPs; g.1502T>G and g.9683C>T), as well as two missense mutations that have been previously reported (R166W and H244R) in VSX1. We also found three undescribed SNPs (g.4886G>A, g.4990C>G, and g.9061T>A) in SOD1. The R166W and H244R mutations were co-segregated in affected family members but not in those that were unaffected. Moreover, the ARMS-PCR strategy did not detect the identified mutations in controls. CONCLUSIONS: Our data suggest a significant association between KTCN patients and VSX1 genetic alterations (p.R166W and p.H244R). Although our findings support VSX1 as a plausible candidate gene responsible for keratoconus, other chromosomal loci and genes could be involved in KTCN development. Taken together, our results suggest that p.R166W and p.H244R could have possible pathogenic influences on KTCN.

Wavefront-guided vs wavefront-optimized LASIK: a randomized clinical trial comparing contralateral eyes.

PURPOSE: To compare wavefront-guided and wavefront-optimized LASIK in patients with myopic astigmatism up to -7.00 diopters (D) sphere and 3.00 D cylinder. METHODS: In this prospective, comparative study, 41 patients had wavefront-guided LASIK in one eye and wavefront-optimized LASIK in the fellow eye. The LASIK flap was created with a Hansatome XP microkeratome (Bausch & Lomb). The ALLEGRETTO Concerto excimer laser (WaveLight Laser Technologie AG) was used for photoablation. Pupil centroid shift and cyclotorsion were not compensated in the wavefront-guided treatments. The ALLEGRETTO Wave analyzer was used to measure ocular wavefront aberrations, and the CSV-1000 instrument (VectorVision) was used to measure contrast sensitivity before and 1 and 3 months after LASIK. RESULTS: Preoperative mean spherical equivalent refraction was -4.25±1.19 D (range: -7.50 to -2.50 D) and -4.15±1.21 D (range: -7.13 to -1.75 D) in the wavefront-guided and wavefront-optimized groups, respectively. Three months postoperatively, 33 (89.2%) eyes in the wavefront-guided group and 31 (83.8%) eyes in the wavefront-optimized group had uncorrected distance visual acuity of 20/20. Higher order aberrations increased from 0.28±0.08 µm (range: 0.13 to 0.48 µm) and 0.26±0.08 µm (range: 0.13 to 0.55 µm) to 0.45±0.17 µm (range: 0.18 to 0.71 µm) and 0.45±0.16 µm (range: 0.21 to 0.84 µm) in the wavefront-guided and wavefront-optimized groups, respectively. Except for C6 trefoil (P=.006), all Zernike polynomials increased in both groups postoperatively with no statistical difference between groups in spherical aberration (P=.41), C7 coma (P=.67), C8 coma (P=.79), and trefoil (P=.82). Contrast sensitivity did not decrease in either group and no statistically significant differences between groups were noted. CONCLUSIONS: Higher order aberrations, especially spherical aberration, increasd approximately the same amount in both groups.

Keratoconus detection by novel indices in patients with Down syndrome: a cohort population-based study.

PURPOSE: To use novel indices to determine the prevalence of KC and its progression in patients aged 10-30 years with Down syndrome. STUDY DESIGN: Cohort population-based study. METHODS: Two hundred twenty-six of 250 invited Down syndrome patients were enrolled. The diagnostic criteria were confirmed by two independent expert examiners using slit-lamp examinations and topographic indices measured by Pentacam HR (Oculus Optikgeräte): maximum keratometry centered on the steepest point (zonal Kmax-3 mm), Ambrósio's relational thickness (ART), inferior-superior asymmetry (IS-value), Belin/Ambrósio deviation value (BAD-D), the Tomographic and Biomechanical Index (TBI), and a posterior elevation map. In the KC cases, Corvis ST (Oculus Optikgeräte) was done. All the KC cases completed the second phase in 2017. RESULTS: KC was identified in 28 patients (12.39%; 95% confidence interval: 8.2-17.9%): 20 bilateral and eight unilateral cases. Of these, 24 were in the ≤ 20-years age group, and four, in the > 20-years age group. The frequency of KC was not significantly correlated with age (P = 0.804) or gender (P = 0.322). In the KC cases, the mean zonal Kmax-3 mm, ART-max, IS-value, BAD-D, CBI, and TBI were 50.40 ± 5.88 D, 321.63 ± 111.94 µm, 1.99 ± 2.51, 3.73 ± 3.12, 0.54 ± 0.61, and 0.86 ± 0.20, respectively, and the minimum corneal thickness was 492.17 ± 42.67 µm. Of the 28 patients, 39.6% showed progression, and all were in the ≤ 20-years age group. CONCLUSION: The prevalence of KC in Down syndrome patients is significantly higher than that reported in non-Down syndrome individuals of the same age groups. The progression rate is approximately similar to that of the non-Down syndrome population. Screening programs should be applied to prohibit serious visual impairment in these populations.

Two-year results of femtosecond assisted LASIK versus PRK for different severity of astigmatism.

PURPOSE: To compare two-year results of femtosecond laser assisted LASIK (femto-LASIK) and photorefractive keratectomy (PRK) in terms of astigmatism correction in patients with less than 2.0 diopters (D) of spherical error and more than 2.0 D of cylinder error. METHODS: In this retrospective study, data were extracted from 100 patient charts. The two study groups were matched by age, gender, and baseline uncorrected distance visual acuity (UDVA) and refractive astigmatism (RA). Preoperative astigmatism was categorized as mild: 2.00 to <3.00 D, moderate: 3.00 to <4.00 D, and severe: ≥4.00 D. RESULTS: Mean RA in the femto-LASIK and PRK groups was respectively -3.15 ± 0.94 D (-7.00 to -2.00 D) and -3.29 ± 0.95 D (-6.25 to -2.00 D) at baseline (P = 0.284), and -0.61 ± 0.40 D and -0.62 ± 0.60 D one year after surgery (P = 0.674), but significantly lower in the femto-LASIK group (-0.61 ± 0.39 vs. -0.83 ± 0.56 D, P = 0.021) at 2 years when the rate of residual astigmatism more than 1.0 D was 6.3% in the femto-LASIK and 19.6% in the PRK group (P = 0.046). Mean UDVA in the femto-LASIK group (0.02 ± 0.05 logMAR) was better than the PRK group (0.06 ± 0.10 logMAR) (P = 0.025). Mean corrected distance visual acuity (CDVA) was not significantly different between groups (0.01 ± 0.03 vs. 0.01 ± 0.04 logMAR, P = 0.714). Both groups had 1-4 Snellen lines CDVA improvement. The three subgroups of baseline astigmatism did not differ significantly in terms of residual astigmatism (all P > 0.05). However, in subgroups with ≥4.00 D cylinder, there was less astigmatic regression at 1 year in the femto-LASIK group (0.28 ± 0.43 D) than the PRK group (0.54 ± 0.68 D) (P = 0.007). CONCLUSIONS: Our results pointed to better two-year results with femto-LASIK in the treatment of different degrees of astigmatism. UDVA improvement was superior with femto-LASIK, but the two methods did not significantly differ in terms of CDVA improvement.

Multipoint assessment of demarcation line depth after standard and accelerated cross-linking in central and inferior keratoconus.

PURPOSE: To determine the changes in the depth of the demarcation line in the central to peripheral cornea following accelerated compared to standard corneal cross-linking (CXL). METHODS: In this prospective, non-randomized study, 60 eyes with progressive keratoconus underwent accelerated or standard CXL (30 in each group). Anterior segment optical coherence tomography (AS-OCT) was done one month later by two independent masked examiners to measure the depth of the demarcation line in the central cornea and on peripheral rings. RESULTS: The inter-examiner agreement (intra-class correlation coefficient) was >0.75 for all measured points, and average measurements were used in the analysis. The depth of the visualized demarcation line in the center was 223.4 ± 67.4 µm and 354.9 ± 79.0 µm in the accelerated and standard groups, respectively (P < 0.001). The depth significantly decreased from the center to the 7 mm ring in both groups (all P < 0.05). This change was 7.7-26.1% and 2.2%-11.1% in the accelerated and standard groups, respectively. In the accelerated group, the demarcation line was deeper in the central cone sub-group compared to the inferior cone sub-group, but in the standard group, the demarcation line was deeper in the inferior cone sub-group (all P < 0.05). Cases with an inferior cone showed greater inter-group differences in all studied points. CONCLUSIONS: The depth of the demarcation line with accelerated CXL is less than the standard protocol and decreases from the center towards the periphery. Demarcation lines are more homogenized with standard CXL. In cases with an inferior cone, demarcation line depth varies throughout the cornea.