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.

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.

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.

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.

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.

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.

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.

Scotopic contrast sensitivity and glare after accelerated corneal cross-linking.

BACKGROUND: The aim was to assess one-year changes in uncorrected and corrected contrast sensitivity (CS) and glare under scotopic conditions after accelerated cross-linking (CXL) using the 18 mW/cm2 protocol for the treatment of progressive keratoconus and compare results with unoperated controls. METHODS: In this non-randomised clinical trial, 30 eyes were enrolled in the CXL group and 30 were assigned to the control group. Scotopic CS at spatial frequencies (SFs) of 0.5, 1.1, 2.2, 3.4, 7.1 and 15 cycles per degree (cpd) were assessed using the MonCv3System (Metrovision, Pérenchies, France) under scotopic conditions (0.5 lux) at baseline and at six and 12 months. RESULTS: The mean ages of the participants in the CXL and control groups were 24.32 ± 5.17 and 30.93 ± 7.43 years, respectively (p < 0.001). After adjusting for age, changes in uncorrected and corrected CS and glare were similar in the two groups (all p > 0.05) except for corrected CS at SF 7.1 cpd (1.45 ± 4.31 versus 3.21 ± 4.69 dB, p = 0.010) and 15 cpd (1.12 ± 4.63 versus 3.03 ± 5.48 dB, p = 0.007), which were reduced as an effect of CXL. Based on covariate analyses, among corrected CS indices, corrected CS7.1 and CS15 were related to CXL and their baseline values (all p < 0.050). Uncorrected CS in all SFs and uncorrected and corrected glare were related to their pre-operative values (all p < 0.001). CONCLUSION: Accelerated CXL can reduce scotopic corrected CS at SFs higher than 7.0 cpd in cases with better baseline values of these parameters. Changes in uncorrected CS and glare are only a factor of baseline values and the indices reduce in cases with better baseline values after one year.

Mesopic Quality of Vision after Accelerated 18 mW/cm2 Corneal Cross-linking: Mid-term Results.

PURPOSE: The purpose of the study was to determine 2-year changes in mesopic higher-order aberrations (HOAs) and contrast sensitivity (CS) after accelerated corneal cross-linking (CXL) in keratoconus patients. MATERIALS AND METHODS: In this before-after interventional case series, patients with progressive keratoconus were subjected to accelerated CXL (18 mW/cm2, 5 min). Patients were examined with the OPD-Scan III and CVS-1000 grating charts under mesopic conditions at baseline and at 12 and 24 months after CXL. RESULTS: At 24 months after CXL, compared to baseline, mesopic CS in spatial frequencies of 3, 6, 12, and 18 cycle per degree reduced respectively to 0.09 ± 0.27, 0.09 ± 0.32, 0.11 ± 0.19, and 0.02 ± 0.10; these changes were not statistically significant (all P > 0.05). The reduction in ocular HOAs was 0.11 ± 0.43; ocular coma, trefoil, and spherical aberration (SA) decreased by 0.09 ± 0.36, 0.05 ± 0.35, and 0.00 ± 0.13 microns, respectively (all P > 0.05). Reductions in corneal HOAs (0.89 ± 7.08) including coma (0.99 ± 3.55), SA (1.14 ± 3.92), and trefoil (1.28 ± 5.53) were not statistically significant (all P > 0.05). Coma had the highest share of corneal HOAs before and 24 months after CXL and the largest 24-month decrease was seen in corneal SA. CONCLUSION: At 2 years after accelerated CXL, despite reduced keratometry and corneal flattening, mesopic CS as well as ocular and corneal HOA remained unchanged, and the procedure did not cause a reduction in patients' vision quality.

Chronic subclinical inflammation after phakic intraocular lenses implantation: Comparison between Artisan and Artiflex models.

PURPOSE: To compare chronic subclinical inflammation induced after implantation of Artisan vs. Artiflex phakic intraocular lenses (pIOLs). METHODS: This prospective, comparative, non-randomized study included consecutive patients with moderate to high myopia who underwent Artisan or Artiflex pIOL implantation with standard surgery and postoperative care. Anterior chamber flare was assessed quantitatively using laser flare photometry (LFP) at baseline, 1 week, 1 month, 3 months, 6 months, and 2 years after surgery. RESULTS: PIOLs were implanted in 72 eyes (40 patients); Artisan pIOLs in 16 eyes (Artisan group) and Artiflex pIOLs in 56 eyes (Artiflex group). The mean preoperative anterior chamber flare was 6.5 ± 2.3 (range, 4.2-9.5) photons per millisecond (ph/ms) and 4.2 ± 0.9 (range, 2.5-11.7) ph/ms in Artisan and Artiflex groups, respectively (P = 0.400). In spite of early postoperative rise, the flare value returned to preoperative levels 6 months after pIOL implantation and remained stable up to 2 years. The amount of flare was not statistically different between Artisan and Artiflex groups in any postoperative follow-up (all P > 0.05). The trend in flare changes was not different between the studied groups (ANCOVA, P = 0.815). CONCLUSION: The inflammatory response induced by implantation of either type of Artisan and Artiflex pIOLs is short-lived without statistically significant difference between the two models.

Corneal Biomechanics After Accelerated Cross-linking: Comparison Between 18 and 9 mW/cm2 Protocols.

PURPOSE: To determine 1-year corneal biomechanical changes after accelerated corneal cross-linking in patients with progressive keratoconus and compare them between 5-minute (18 mW/cm2) and 10-minute (9 mW/cm2) protocols. METHODS: In this non-randomized clinical trial, cases in both groups were examined with the Corneal Visualization Scheimpflug Technology (Corvis ST; Oculus Optikgeräte GmbH, Wetzlar, Germany) at baseline and at 6 and 12 months after treatment. Extracted indices included intraocular pressure (IOP), central corneal thickness (CCT), first and second applanation times, lengths, and velocities (T1, T2, L1, L2, V1, and V2), highest concavity time (HCT), deformation amplitude (DA), peak distance between bending points, and radius of curvature. RESULTS: Mean patient age, baseline maximum keratometry, CCT, and IOP were similar between groups. After adjusting for CCT and baseline values with repeated measures analysis of covariance, at 1 year after the procedure, IOP (13.14 ± 1.41 vs 12.12 ± 1.49 mm Hg, P = .034) and T1 (6.84 ± 0.20 vs 6.67 ± 0.23 ms, P = .036) were higher in the 5-minute group, but T2 (21.31 ± 0.27 vs 21.58 ± 0.28 ms, P = .007), HCT (16.06 ± 0.51 vs 16.31 ± 0.48 ms, P = .017), and DA (1.03 ± 0.09 vs 1.10 ± 0.08 mm, P = .028) were lower. Other inter-group differences were not statistically significant (all P > .050). All 1-year changes were independent of cone position (all P > .050). CONCLUSIONS: At 1 year after cross-linking in cases of mild and moderate keratoconus, corneal biomechanics appeared stable or stronger than baseline with both 5- and 10-minute protocols. However, mild cases who had the 5-minute protocol showed better improvement based on Corvis ST indices. [J Refract Surg. 2017;33(8):558-562.].

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.

Mid-Term Results of a Single Intrastromal Corneal Ring Segment for Mild to Moderate Progressive Keratoconus.

PURPOSE: To study the mid-term effects of implanting a single intracorneal ring segment (ICRS) for treatment of mild to moderate progressive keratoconus. METHODS: This retrospective study was conducted on patients with progressive keratoconus treated with ICRS. The mean follow-up time was 15.2 ± 8.8 (range, 7-26) months before and 27.8 ± 7.5 (range, 18-35) months after surgery. Patients received no other treatment during this time. Of the cases studied, 59.1% had inferior keratoconus. RESULTS: Thirty eyes of 30 patients with a mean age of 27.5 ± 4.6 years were included in the study. Corrected distance visual acuity decreased by 1 line during the preoperative follow-up and improved by 2 lines after surgery (P < 0.05). Maximum keratometry (Kmax) of the anterior (2.39 ± 0.75 D) and posterior (0.33 ± 0.32 D) corneas at 3 mm and anterior Kmax at 8 mm (2.39 ± 0.95 D) decreased after treatment (all P < 0.05). The posterior Q value shifted toward a more oblate curvature (0.50 ± 0.52, P = 0.023). Decreases in anterior elevation at the thinnest point (5.22 ± 7.21 µm) and posterior corneal central elevation (8.89 ± 11.26 µm) were significant (both P < 0.05). Corneal thickness at the center (11.11 ± 12.38 µm) and thinnest point (15.89 ± 12.75 µm) increased after treatment (all P < 0.001). Other significant changes included postoperative decreases in the keratoconus index (0.12 ± 0.06), index of height decentration (0.06 ± 0.05), index of surface variance (27.32 ± 13.08), index of vertical asymmetry (0.42 ± 0.21), index of height asymmetry (8.42 ± 20.57), and an increase in the center keratoconus index (0.01 ± 0.02) (P < 0.001). CONCLUSIONS: This study demonstrates that ICRS implantation provides favorable mid-term outcomes in treatment of mild and moderate progressive keratoconus and can improve corneal indices compared with their preoperative states.

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.

Long-term Results of an Accelerated Corneal Cross-linking Protocol (18 mW/cm2) for the Treatment of Progressive Keratoconus.

PURPOSE: To compare the long-term outcomes of accelerated and standard corneal cross-linking protocols in the treatment of progressive keratoconus. DESIGN: Prospective randomized clinical trial. METHODS: Thirty-one eyes with keratoconus were treated with an accelerated protocol (18 mW/cm(2), 5 min) and all contralateral eyes were treated with the standard method (3 mW/cm(2), 30 min) using the same overall fluence of 5.4 J/cm(2). RESULTS: At 18 months after the procedure, the standard group showed significant improvement in spherical equivalent (P < .05), K-readings (P < .05), Q value (P < .05), index of surface variance (P < .05), and keratoconus index (P = .008) and decline in central corneal thickness (P < .05), but no significant change in visual acuity, corneal hysteresis, corneal resistance factor, P2 area, or endothelial cell density. In the accelerated group, central corneal thickness was the only parameter with statistically significant change. However, neither of these parameters showed significant differences between the standard and the 18 mW/cm(2) accelerated protocol, except K-reading (P = .059) and index surface variance (P = .034). CONCLUSION: An accelerated cross-linking protocol, using 18 mW/cm(2) for 5 minutes, shows a comparable outcome and safety profile when compared to the standard protocol, but better corneal flattening is achieved with the standard method than the accelerated method. Overall, both methods stop the disease progression similarly. This study will continue to examine more long-term results.

Corneal Collagen Cross-Linking in the Treatment of Progressive Keratoconus: A Randomized Controlled Contralateral Eye Study.

BACKGROUND: To assess the short-term efficacy and safety of corneal collagen cross-linking (CXL) in preventing the progression of keratoconus (KCN). MATERIALS AND METHODS: This randomized controlled clinical trial enrolled 26 patients diagnosed with bilateral progressive KCN and were eligible for CXL. In each patient, one eye was randomly selected for treatment, and the contralateral eye served as the control. The patients underwent CXL with riboflavin drops and ultraviolet radiation in the treated eye. One year follow-up data are presented. Postoperatively, patients were assessed for progression of KCN, visual changes, and other findings. The main outcome measures were maximum simulated keratometry (K-max), best spectacle-corrected visual acuity (BSCVA), and average simulated keratometry. P <0.05 was considered as statistically significant. RESULTS: In the treated eyes, the mean K-max values decreased by 0.22 D at 1-year postoperatively and increased by 0.41 D in the control group. This difference was statistically significant (P < 0.001). BSCVA improved slightly (a decrease of 0.13 LogMAR) and decreased slightly in the control group (a 0.01 LogMAR increase). The difference between groups was statistically significant (P = 0.014). There was no decrease in visual acuity attributable to complications of CXL in the treated eyes. At 1-year, the keratometry in 3 (12%) treated eyes increased by more than 0.50 D and were considered cases of failed treatment. CONCLUSION: Preliminary and 1-year results indicate CXL can halt the progression of KCN in most cases without causing serious complications.

Short-term comparison of accelerated and standard methods of corneal collagen crosslinking.

PURPOSE: To compare the 6-month results of accelerated and standard collagen crosslinking (CXL) treatment of progressive keratoconus. SETTING: Noor Eye Hospital, Tehran, Iran. DESIGN: Prospective randomized clinical trial. METHODS: Two groups of eyes (intervention and control) received corneal collagen crosslinking (CXL) treatment. The intervention group received accelerated CXL (18 mW/cm(2), 5 minutes), and the control group received standard CXL (3 mW/cm(2), 30 minutes). The eyes were evaluated for changes in the visual indices, refraction, and topography preoperatively and 1, 3, and 6 months postoperatively and regarding corneal rigidity indices and the endothelial cell count (ECC) preoperatively and at 6 months. RESULTS: The study evaluated 62 eyes (31 patient) in 2 groups. The mean changes in uncorrected (P = .733) and corrected (P = .646) distance visual acuities and manifest refraction spherical equivalent (P = .598) did not differ statistically significantly between the 2 groups. The central corneal thickness was higher in the standard group than the accelerated group (P = .025). The mean decrease in the maximum keratometry (K) (P = .865) and mean K (P = .974) and the mean changes in the asphericity (P = .272) were not statistically significantly different between the 2 groups. The mean changes in corneal hysteresis (CH) (P = .548) and the corneal resistance factor (CRF) (P = 1.000), CH-CRF (P = .282), and the area under the peak 2 (P = .260) were similar in both groups. The mean decrease in the ECC was not statistically significantly different between the 2 groups (P = .218). CONCLUSION: Based on 6-month results, accelerated and standard corneal CXL arrested the progression of keratoconus similarly. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

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.