Background: In vivo corneal biomechanics evaluation has been used to help screen early keratoconus in recent years. This study is to evaluate the value of a Scheimpflug-based biomechanical analyser combined with tomography in detecting subclinical keratoconus by distinguishing normal eyes from frank keratoconus (KC) and forme frusta keratoconus (FFKC) eyes in Chinese patients. Methods: Study design: diagnostic test. This study included 31 bilateral frank keratoconus patients, 27 unilateral clinically manifesting keratoconus patients with very asymmetric eyes, and 79 control subjects with normal corneas. Corneal morphological and biomechanical parameters were measured using a Pentacam HR and a Corvis ST (OCULUS, Wetzlar, Germany). The diagnostic ability of computed parameters reflecting corneal biomechanical and morphological traits [including the Belin-Ambrósio deviation index (BAD_D), the Corvis biomechanical index (CBI) and the tomographic and biomechanical index (TBI)] was determined using receiver operating characteristic (ROC) curve analysis and compared by the DeLong test. Additionally, the area under the curve (AUC), the best cut-off values, and the Youden index for each parameter were reported. A novel corneal stiffness parameter, the stress-strain index (SSI), was also compared between KC, FFKC and normal eyes. Results: Every morphological and biomechanical index analysed in this study was significantly different among KC, FFKC and normal eyes (P = 0.000). The TBI was most valuable in detecting subclinical keratoconus (FFKC eyes), with an AUC of 0.928 (P = 0.000), and both forms of corneal ectasia (FFKC and frank KC eyes), with an AUC of 0.966 (P = 0.000). The sensitivity and specificity of the TBI was 97.5 and 77.8 % in detecting FFKC and 97.5 and 89.7 % in detecting any KC, respectively, with a cut-off value of 0.375. The morphological index BAD_D and the biomechanical index CBI were also very useful in distinguishing eyes with any KC from normal eyes, with AUCs of 0.965 and 0.934, respectively. The SSI was significantly different between KC, FFKC and normal eyes (P = 0.000), indicating an independent decrease in corneal stiffness in KC eyes. Conclusions: The combination of a Scheimpflug-based biomechanical analyser and tomography could increase the accuracy in detecting subclinical keratoconus in Chinese patients. The TBI was the most valuable index for detecting subclinical keratoconus, with a high sensitivity and specificity. Evaluation of corneal biomechanical properties in refractive surgery candidates could be helpful for recognizing potential keratoconic eyes and increasing surgical safety.

Development of evidence-based guidelines for keratorefractive lenticule extraction (KLEx). Keratorefractive lenticule extraction refers to various corneal refractive procedures involving removal of refractive lenticules of intrastromal corneal tissue, typically through a small incision, eliminating creation of a corneal flap. This technique has gained popularity rapidly; however, no clinical practice guidelines exist. These evidence-based guidelines were developed following the World Health Organization guidebook using the Appraisal of Guidelines for Research and Evaluation II tool and adhering to the Reporting Items for Practice Guideline in Healthcare statement. The body of evidence was drawn from 8 literature databases, 5 clinical guideline databases, and 2 academic organizations. Recommendations were developed via a Delphi consensus of 44 global experts in refractive surgery, cornea, retina, glaucoma, and optometry. The certainty of evidence, balance of benefits and harms, patient preferences and values, and economic evaluations were considered fully. The Grading of Recommendations Assessment, Development, and Evaluation approach was used to assess evidence quality and recommendation strengths. From 385 initial clinical questions, 15 were identified, prompting a review of 250 717 studies, with 609 included for conducting and updating 26 and 2 systematic reviews, respectively. Subsequently, consensus was reached on 38 recommendations for preoperative screening, candidate selection, intraoperative quality control, operating principles, postoperative monitoring, and complication management. For KLEx, an effective and accurate refractive correction is attributed to various factors such as corneal thickness, degree of myopia, treatment nomogram, and optical zone. For complications that could affect vision, comprehensive and effective management strategies were proposed, particularly for wrong-plane dissection and difficult lenticule removal, suction loss, and perioperative infection. Customized surgical planning protocols and operative techniques were analyzed. Among all recommendations, 29 (76%) were labelled as strong, each externally reviewed. The corneal biomechanical properties may help to improve safety and predictability, although they need further validation. Several research gaps for enhancing KLEx safety were also revealed. These guidelines provide evidence-based recommendations for KLEx in clinical practice, such as for preoperative screening for keratoconus, surgical planning, and management and prevention of complications and infection. The guidelines are expected to minimize the complications and achieve better outcomes. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Purpose: To analyze the level of sex hormone in relation to keratoconus (KC).Methods: Sixty-two eyes of 62 patients (12 females, 50 males) classified as KC and 120 eyes of 120 patients (21 females, 99 males) with mild to moderate myopia and astigmatism were analyzed. Plasma samples were collected and analyzed using a chemiluminescence immunoassay to determine the concentrations of estriol (E₃), estradiol (E₂), progesterone (P), and testosterone (T). Corneal morphological parameters, such as the central corneal thickness (CCT), thinnest corneal thickness (TCT), and maximum simulated keratometry (K_max), were measured using Pentacam and Sirius.Results: The mean age was 23.73 ± 5.16 years for patients with KC and 23.68 ± 6.10 years for patients treated with laser vision correction (LVC). Among the patients with KC, 12 were female (19.35%) and 50 were male (80.65%). The majority of patients with KC were between 20 and 30 years old. In female patients, the concentration of T in the KC group was significantly lower than that in the LVC group (0.86 ± 0.33 vs. 1.18 ± 0.58 nmol/L; P = 0.044). There were positive correlations between T, CCT (r = 0.395, P = 0.023) and TCT (r = 0.378, P = 0.030) in female patients. In male patients, E₂ was higher in the KC group than the LVC group (143.75 ± 34.82 vs. 124.80 ± 43.56 pmol/L; P = 0.013), while T was significantly lower (11.59 ± 2.85 vs. 13.58 ± 4.77 nmol/L; P = 0.026). A positive correlation was found between E₂ and K_max (r = 0.222, P = 0.007) in male patients.Conclusions: Conclusively, our results showed that T level was reduced in both female and male KC plasma, while E₂ was increased in male KC plasma. Different levels of sex hormones are correlated with KC, which, may provide the basis of a new technique for screening and diagnosing KC with or without the assistance of current imaging techniques. Moreover, the correlations between sex hormone alterations and KC provide compelling insight into KC etiopathogenesis.

PURPOSE: To compare clinical outcomes between topography-guided customized ablation treatment (TCAT) and wavefront-optimized (WFO) laser in situ keratomileusis (LASIK) in fellow eyes of myopic patients. METHODS: This prospective randomized contralateral study included 432 eyes of 216 myopic patients who underwent LASIK. TCAT was randomly performed in one eye (TCAT group) and WFO LASIK in the fellow eye (WFO group). The WaveLight FS200 femtosecond laser (Alcon Laboratories, Inc., Fort Worth, TX) was used to create the flap and the EX500 excimer laser was used for photoablation. The Sirius combined corneal topographer and tomographer system (CSO, Florence, Italy) was used to measure the corneal aberrations. Refractive and visual outcomes and corneal aberrations were compared between the two groups. RESULTS: At 1 month postoperatively, the uncorrected distance visual acuity (UDVA) was 20/20 or better in 89.4% of eyes in the TCAT group and 93.5% of eyes in the WFO group ( P < .05). The UDVA became similar at postoperative 6 months ( P > .05). Postoperative corrected distance visual acuity and residual manifest refractive spherical equivalent were similar between the groups ( P > .05). The postoperative residual refractive astigmatism in the TCAT group was greater than that in the WFO group ( P < .05). The optical path difference and root mean square of higher order aberrations and coma were significantly lower in eyes in the TCAT group at postoperative 1 and 6 months ( P < .05). CONCLUSIONS: TCAT in virgin eyes induced less corneal optical path difference, fewer higher order aberrations, and less coma than WFO LASIK. However, TCAT was not as accurate as WFO, especially in astigmatism correction. A better compensation method for TCAT is warranted. [ J Refract Surg. 2019;35(9):575–582.]