Clinical features of keratoconus and influencing factors of disease severity

To investigate the clinical characteristics of patients with keratoconus, and to explore the factors influencing keratoconus severity.

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.

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).

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.