Keratoconus is an adolescent-onset blinding eye disease characterized by the protrusion and thinning of the central or paracentral cornea. The cause of keratoconus remains unclear, though its onset and progression arise from a multifactorial interplay involving a polygenic background, environmental exposures, and biomechanical decompensation. Recent studies have demonstrated significant gender differences in the pathogenesis and progression of keratoconus.At the epidemiological level, most studies suggest that the disease shows a male predominance; in terms of clinical features, male patients tend to experience an earlier onset and present with more severe clinical phenotypes, such as more serious corneal morphological deterioration; at the pathological mechanism level, sex hormone expression differences and genetic susceptibility differences play a key role in disease progression; this difference further affects the formulation of clinical prevention and treatment strategies, such as early warning screening for high-risk male groups and individualized corneal cross-linking intervention timing. This article reviews gender differences in keratoconus from the perspectives of epidemiology, clinical characteristics, prevention and treatment, and pathological mechanisms, providing relevant references and insights for future clinical practice.

Keratoconus is a blinding eye disease characterized by central or paracentral corneal thinning, forward conical protrusion, and high myopia with irregular astigmatism.There are still no effective radical treatments for keratoconus.Current methods mainly include the prevention and treatment of risk factors, non-surgical optical correction and surgical treatment.The main risk factor prevention and treatment measures include intervention of eye rubbing behavior, symptomatic treatment of allergic diseases and systemic diseases, and correction of poor sleeping position.Non-surgical optical correction uses spectacles or corneal/scleral contact lenses to improve corrected vision.Surgical treatments include intracorneal ring segment implantation to improve corrected vision, corneal collagen cross-linking to increase the biomechanical stiffness of the cornea, and corneal transplantation to treat patients with severe keratoconus or corneal scarring.In addition, femtosecond laser-assisted keratoplasty, lenticule intrastromal keratoplasty combined with corneal collagen cross-linking have been gradually applied in clinical treatment, and tissue engineering based on biosynthetic substitutes, 3D bioprinting technology and cell engineering based on stem cell therapy have provided research prospects for the treatment of keratoconus.This article summarizes the prevention and treatment of clinical risk factors, non-surgical optical correction and surgical treatment, and discusses the research perspective of innovative treatment, in order to provide personalized treatment for patients with keratoconus.

Keratoconus is a blinding eye disease characterized by central or paracentral corneal thinning, forward conical protrusion, and high myopia with irregular astigmatism.There are still no effective radical treatments for keratoconus.Current methods mainly include the prevention and treatment of risk factors, non-surgical optical correction and surgical treatment.The main risk factor prevention and treatment measures include intervention of eye rubbing behavior, symptomatic treatment of allergic diseases and systemic diseases, and correction of poor sleeping position.Non-surgical optical correction uses spectacles or corneal/scleral contact lenses to improve corrected vision.Surgical treatments include intracorneal ring segment implantation to improve corrected vision, corneal collagen cross-linking to increase the biomechanical stiffness of the cornea, and corneal transplantation to treat patients with severe keratoconus or corneal scarring.In addition, femtosecond laser-assisted keratoplasty, lenticule intrastromal keratoplasty combined with corneal collagen cross-linking have been gradually applied in clinical treatment, and tissue engineering based on biosynthetic substitutes, 3D bioprinting technology and cell engineering based on stem cell therapy have provided research prospects for the treatment of keratoconus.This article summarizes the prevention and treatment of clinical risk factors, non-surgical optical correction and surgical treatment, and discusses the research perspective of innovative treatment, in order to provide personalized treatment for patients with keratoconus.

Keratoconus is a progressive blinding eye disease that characterized by corneal thinning and protrusion, which accompanied with irregular astigmatism and impaired visual acuity.The irregular astigmatism of early keratoconus can be corrected by spectacles. For the irregular astigmatism of moderate to severe keratoconus, spectacles are no longer suitable, and contact lenses are the best choice for patients to restore vision. There are various types of contact lenses, making the selection very difficult. In addition, trying on lenses for a long time will increase the discomfort and overall feeling of patients, and greatly increase the workload of doctors. Thus, the article aims to summarize and discuss the classification of contact lenses, the application of contact lenses in different types of keratoconus, the complications of contact lens, and the current status and prospect of contact lenses, with a view to understanding the management and clinical application of contact lenses in keratoconus patients and to further improving the application value of contact lenses in keratoconus.

Keratoconus is a blinding corneal disease characterized by central or paracentral corneal thinning and conical ectasia, and usually happens in adolescence. Currently, the etiology of keratoconus is unclear. Multiple studies have identified an association between genetics, eye rubbing, allergic diseases, ultraviolet exposure and keratoconus. Recently, several studies identified that sex hormones also played important roles in the pathogenesis of keratoconus. The disturbance of sex hormones may increase the risk of occurrence and progress of keratoconus. This review aims to summarize the pathophysiological effects of sex hormones on the cornea, clarify the effects of sex hormones on keratoconus and its related inflammatory or immune mechanisms, and explore the role of sex hormones in the early diagnosis and treatment of keratoconus, providing reference and help for clinical work.

Objective:To investigate the repeatability of corneal topographic parameters with the Pentacam HR in patients with keratoconus of different severity.Methods:A diagnostic test study was performed.A total of 120 eyes from 98 patients with subclinical keratoconus or keratoconus were enrolled at Henan Eye Hospital from January 2019 to March 2022.The patients were divided into subclinical keratoconus group, mild keratoconus group, moderate keratoconus group and severe keratoconus group, with 30 eyes in each group.An additional 30 eyes of 30 subjects undergoing refractive surgery were selected as a control group.Three consecutive Pentacam HR measurements were performed by the same clinician.The recordings included a total of 53 parameters in anterior corneal surface, posterior corneal surface, thickness, composite index, and corneal densitometry.The within-subject standard deviation (Sw), repeatability limit ( r) and tolerance index (TI) were calculated to evaluate the repeatability of the parameters between different groups.This study adhered to the Declaration of Helsinki and was approved by the Ethics Committee of Henan Eye Hospital (No.HNEECKY-2019[5]).All subjects were informed of the purpose and significance of the study and signed an informed consent form before enrollment. Results:Compared with the control group, the TI of the subclinical, mild, moderate and severe keratoconus groups were 54.71%(29/53), 66.04%(35/53), 90.57%(48/53) and 94.34%(50/53), respectively, higher than 0.31.The steep keratometry (Ks), the maximum keratometry (Kmax) of the anterior corneal surface, the anterior corneal radius of curvature, the flat keratometry (Kf) of the posterior corneal surface, the posterior corneal radius of curvature (PRC), the thinnest corneal thickness (TCT), the average densitometry for the anterior 120 μm in the 0-2 mm area (A.0-2 mm), average densitometry for the anterior 120 μm in the 2-6 mm area (A.2-6 mm), average densitometry for the central tissue in the 0-2 mm area (C.2-6 mm), average densitometry for the total cornea in the 0-2 mm area (T.0-2 mm) and average densitometry for the total cornea in the 2-6 mm area (T.2-6 mm) showed good repeatability in the subclinical and mild keratoconus groups (TI<0.31).Kmax Zonal Mean 3 mm, posterior corneal surface mean keratometry, central keratoconus index showed good repeatability in subclinical, mild and moderate keratoconus groups.Kmax Zonal Mean 4 mm and Kmax Zonal Mean 5 mm showed good repeatability in all groups (TI<0.31).Conclusions:For patients with subclinical and mild keratoconus, Kf of the posterior corneal surface, PRC and TCT are recommended to monitor disease progression.To monitor the condition of patients with moderate and severe keratoconus, we may focus on the detection of Kmax Zonal Mean 4 mm and Kmax Zonal Mean 5 mm.

Objective:To investigate the clinical characteristics of patients with keratoconus, and to explore the factors influencing keratoconus severity.Methods:A cross-sectional study was performed.A total of 908 patients (1 476 eyes) with primary keratoconus were enrolled in Henan Eye Hospital from January 2019 to December 2021.The medical history data of patients were collected by face-to-face questionnaire survey.Refractive parameters were measured by subjective optometry.Intraocular pressure (IOP) was measured by a non-contact tonometer, and corrected IOP was calculated by Dresden formula.Corneal topography parameters was obtained using Pentacam HR.The subgroup analysis of clinical characteristics of all patients was performed by age (<21 years, 21~<31 years, ≥31 years) and gender.Disease severity was graded based on steep keratometry (Ks), namely mild (Ks<48 D), moderate (48 D≤Ks<55 D) and severe (Ks≥55 D). The influencing factors of disease severity in keratoconus were analyzed by ordered Logistic regression.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Henan Eye Hospital (No.HNEECKY-2019[5]). All subjects or guardians were informed of the purpose and significance of the study and written informed consent was obtained.Results:Of the 908 patients, 622 were with bilateral keratoconus and 286 were with unilateral keratoconus.The median age of onset was 20(17, 26) years, and the median age of diagnosis was 21(18, 27) years.The ratio of males to females was 3.05∶1.There were 9.80%(89/908) of the patients having a history of allergy, 25.55%(232/908) having a history of other systemic diseases, and 1.98%(18/908) having a family history of keratoconus.Of the 1 476 affected eyes, 27.57%(407/1 476) were diagnosed as severe keratoconus, and 61.94%(568/917) had a history of eye rubbing.The medians of sphericity, cylindricity, IOP, corrected IOP, Ks, thinnest corneal thickness (TCT), anterior corneal surface elevation (AE) and posterior corneal surface elevation (PE) were -4.00(-7.00, -1.75)D, -3.50(-6.00, -1.50)D, 12.00(10.30, 13.80)mmHg, 15.40(13.60, 17.00)mmHg, 49.85(46.40, 54.90)D, 460.00(425.00, 490.00)μm, 21.00(13.00, 34.75)μm, 51.00(33.00, 75.00)μm, respectively.The spherical refraction, IOP and corrected IOP were lower and the cylindrical refraction was higher in patients at age <21 years than in patients at age 21~<31 years, and the TCT of patients at age <21 years was higher than that at age ≥31 years, and the differences were statistically significant (all at P<0.05). Compared with female patients, male patients had younger onset age, lower spherical refraction, IOP and corrected IOP, as well as higher cylindrical refraction, AE and PE, showing statistically significant differences (all at P<0.05). The spherical refraction and IOP of male patients were lower than those of female patients at age <21 years, and the cylindrical refraction was higher in males than in females among the patients at age 21~<31 years, and the differences were statistically significant (both at P<0.05). Among the patients with onset age <21 years and diagnosis age <21 years, the ratio of males to females in patients with severe keratoconus was higher than those with mild and moderate disease, and the difference was statistically significant (both at P<0.05). Older age of onset was a protective factor for disease severity in keratoconus (odds ratio=0.981, 95% confidence interval: 0.963~0.999). Conclusions:The younger the onset age of keratoconus patients, the more severe the disease.Among the patients with severe keratoconus, there were more male patients, and males have a younger onset age and severer conditions.It is suggested that early screening of keratoconus in children and adolescents should be strengthened in clinical work, and more active prevention and treatment measures should be taken for younger patients, especially males.

Objective:To compare the fitting effect between rig gas-permeable contact lens (RGPCL) and scleral lenses (SLs) in moderate and severe keratoconus eyes.Methods:A cross-sectional study was performed.Fifty-two eyes of 42 keratoconus patients were recruited in Henan Eye Hospital from September 2022 to September 2023.Based on steep keratometry (Ks) value, patients were divided into moderate stage (48 D≤Ks<55 D, 28 eyes) and severe stage (Ks≥55 D, 24 eyes). RGPCL and SLs were fitted normatively in all eyes.Fluorescein staining and anterior segment optical coherence tomography were performed under a slit lamp.The distance between the central and lateral centers of the lenses and the cornea, the centering of the lenses, the mobility of the lenses and the peripheral fit of the lenses were observed.Best corrected visual acuity (BCVA) converted to logarithmic minimum angle of resolution, comfort score, wetness score and clarity score were recorded.Differences in the above parameters of each patient between RGPCL and SLs wear were compared.The improvement of the above parameters after RGPCL and SLs wear was compared in moderate and severe patients.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Henan Eye Hospital (No.HNEECKY-2019[5]-04). Written informed consent was obtained from each patient before any medical examination.Results:After RGPCL wear, the mean BCVA, comfort, wetness, and clarity score were 0.19(0.10, 0.30), 5.5(3.0, 7.0) points, 7.0(5.0, 8.0) points and 7.0(4.0, 8.0) points, respectively.After SLs wear, the mean BCVA, comfort score, wetness score and clarity score were 0.10(0.00, 0.10), 8.0(8.0, 9.0) points, 8.0(8.0, 9.0) points and 8.0(6.0, 9.0) points, respectively.Compared with RGPCL wear, the BCVA, comfort score, wetness score and clarity score of SLs were significantly improved ( Z=-5.887, -6.064, -5.705, -5.516; all at P<0.001). There was a moderate positive correlation between BCVA and Kmax after SLs wearing ( rs=0.519, P<0.001), and had a moderate negative correlation with TCT ( rs=-0.535, P<0.001). There was a moderate positive correlation between the clarity score of the SLs and TCT ( rs=0.303, P=0.029). In the moderate and severe subgroup analysis, BCVA, comfort score, wetness score and clarity score were significantly improved after SLs wear compared to RGPCL (all at P<0.05). In addition, the clarity score was significantly improved in severe keratoconus compared to moderate keratoconus ( Z=-3.100, P=0.002). Conclusions:In patients with moderate to severe keratoconus, RGPCL can improve BCVA to a limited extent.SLs can significantly improve patients' comfort, wetness and visual clarity while improving their BCVA.

Keratoconus is a progressive and bilateral corneal disease with the characteristics of the protrusion of the dilated and central thinning cornea.Keratoconus often causes myopia and irregular astigmatism, and corneal edema and scarring in the late stage, leads to significant vision loss, and brings patients psychological pressure and economic burden.Eye rubbing is an important risk factor of keratoconus.Many studies suggest that eye rubbing is related to the occurrence and development of keratoconus.Different frequency and intensity of eye rubbing have different effects on the cornea.In susceptible population, eye rubbing causes severer damage to the cornea and more serious consequences.Eye rubbing damages the cornea by direct mechanical action, raising corneal temperature and intraocular pressure and releasing inflammatory factors resulting in cell apoptosis.Avoiding eye rubbing is of great significance in delaying the development of keratoconus.Reducing the rubbing time and frequency of patients with keratoconus by treating the primary disease causing eye rubbing and distracting them can reduce the occurrence and slow down the progression of keratoconus, and the life quality of patients can be improved.In this review, the role of eye rubbing in the etiology of keratoconus was elucidated to provide reference for the treatment and prevention of keratoconus.

Corneal densitometry is a biological property of corneal tissue, which is related to the transparency of cornea, and can be used to describe the degree of corneal transparency.At present, corneal densitometry has been used in the auxiliary diagnosis and severity evaluation of corneal diseases, as well as in the evaluation of the surgical outcome and the postoperative follow-up, even some systemic diseases affecting the cornea.The measurement of corneal densitometry is an objective, non-invasive and repeatable method to evaluate corneal transparency, which has important reference values for the monitoring of corneal and systemic health.In this article, the application of corneal densitometry in clinical practices was reviewed.