Keratoconus and Personality Traits: A Case-Control Study
Aiello F, Gallo Afflitto G, Ceccarelli F, et al1
Industry support for this study: None
ABSTRACT SUMMARY
The aim of this prospective interventional case-control study was to compare the personality traits of patients with keratoconus (KC; n = 30) to those of age- (18–30 years) and sex-matched individuals without the disease (n = 30). Exclusion criteria included current or past non-KC ocular disease in both eyes, cognitive impairment, and any known psychiatric disorder.
STUDY IN BRIEF
A prospective interventional case-control study compared the personality traits of patients with keratoconus (KC) to those of non-KC control patients. A higher incidence of personality disorders, abnormal temperament, and neuroticism was found in the KC group.
WHY IT MATTERS
This study showed that the burden of KC extends beyond ocular impairment to include psychological features. Early psychiatric consultation and support for KC patients might improve their overall wellness.
Patients received an ophthalmic evaluation and completed the National Eye Institute Visual Function Questionnaire-25 to assess their perceptions of visual function and quality of life. Study participants also underwent a complete psychiatric assessment.
KC patients scored significantly lower on all National Eye Institute Visual Function Questionnaire-25 subscales, signaling they had worse visual function compared to control patients. When assessed with the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, a higher percentage of KC patients presented with at least one cluster C personality disorder compared to control patients (P = .0056). KC patients were also more prone to mood and anxiety disorders; these results, however, were not statistically significant.
On the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego-Modified, KC patients scored significantly higher on the depressive (P = .0358), cyclothymic (P = .0003), and irritable (P = 0.0359) temperament scales compared to control patients. On the NEO Five-Factor Inventory test, KC patients had a significantly higher neuroticism score than non-KC patients (P = .0007). Finally, on the Symptom Check List-90-Revised, KC patients scored higher on the Global Severity Index (P = .0254), Positive Symptom Total (P = .0061), and Positive Symptom Distress Index (P = .0213), which measure overall psychological distress, self-reported symptoms, and symptom intensity, respectively.
DISCUSSION
KC typically presents at a young age. These patients’ development of dysfunctional personality traits may arise from associated visual difficulties, periodic medical visits, and invasive treatments during important phases of their psychosocial development. Eye rubbing is an important risk factor for KC and may be associated with emotional stress in adolescence. Additionally, growing evidence suggests that KC is linked with proinflammatory cytokines, which could also be found in concurrent dysfunctional personality traits.
The study by Aiello et al had two key limitations. First, the case-control design did not permit analysis of the evolution of personality disturbances over time. Second, the small sample size and consistently young age of the study participants could prevent the findings from being generalizable to the broader KC patient population.
Causal Links Between Systemic Disorders and Keratoconus in European Population
Chen X, Chen L2
Industry support for this study: None
ABSTRACT SUMMARY
A mendelian randomization (MR) analysis sought to establish a causal relationship between prevalent systemic diseases and KC. MR uses genetic variants such as single nucleotide polymorphisms to identify possible causal links between risk factors and health outcomes. The study adhered to the Strengthening the Reporting of Observational Studies in Epidemiology Using MR statement guidelines.3
STUDY IN BRIEF
A mendelian randomization analysis identified a causal relationship between prevalent systemic diseases and keratoconus (KC). Hay fever/allergic rhinitis/eczema and ulcerative colitis were found to be risk factors for KC. Additionally, prolonged hyperglycemia was not found to delay KC pathogenesis, as some prior studies have suggested.4
WHY IT MATTERS
Some modern swept-source OCT biometry devices provide a useful foveal snapshot that may help identify macular pathology. Unfortunately, this foveal fixation snapshot demonstrated less sensitivity in the study than spectral-domain OCT, with a false negative rate of 21% to 29%. This has implications for preoperative patient counseling and surgical planning.
A two-sample MR design was used. Genetic data for KC were extracted from an extensive genome-wide association study (GWAS) comprising 2,116 European cases and 24,626 European controls. GWAS data were used to identify single nucleotide polymorphisms demonstrating robust associations with various diseases, including diabetes, hay fever/allergic rhinitis/eczema, obstructive sleep apnea, thyroid gland dysfunction, aortic aneurysm, major depressive disorder, inflammatory bowel disease, and mitral valve prolapse. Inverse-variance weighting was used in the primary analytic study, and the results were corroborated by the Causal Analysis Using Summary Effect estimates model.
Hay fever/allergic rhinitis/eczema (odds ratio [OR], 10.144; P = .001) and ulcerative colitis (OR = 1.147; P = .002) were associated with an increased risk of KC. In contrast, no causal association was identified between hyperglycemia (OR = 0.320; P = .353), obstructive sleep apnea (OR = 0.775; P = .580), thyroid-stimulating hormone (OR = 0.900; P adjusted = .069), aortic aneurysm (OR = 0.995; P = .937), major depressive disorder (OR = 1.227; P = .627), Crohn disease (OR = 1.096; P = .062), or mitral valve prolapse (OR = 0.980; P = .826) and increased KC risk.
DISCUSSION
Identifying specific risk factors for KC raises new considerations for patient care. Earlier KC detection and treatment in patients with associated underlying conditions might reduce KC severity and improve visual outcomes. Moreover, MR analysis presents a promising frontier for studying complex interactions between systemic and ocular diseases.
The analysis by Chen and Chen had several limitations. First was an absence of data for Down syndrome and connective tissue disease because the investigators were unable to locate GWAS data for these conditions. Second, the data used in the MR analysis were not from diverse ethnic groups, making it challenging to generalize the findings to other populations. Third, the sample size of GWAS data for KC was smaller than for other systemic diseases, which could decrease the robustness of identified causal links. Finally, KC is a complex disease influenced by a combination of genetic and environmental factors, and MR analysis is limited in that it overlooks nongenetic factors.
1. Aiello F, Gallo Afflitto G, Ceccarelli F, et al. Keratoconus and personality traits: a case-control study. Cornea. 2024;43(2):237-244.
2. Chen X, Chen L. Causal links between systemic disorders and keratoconus in European population. Am J Ophthalmol. 2024;265:189-199.
3. Skrivankova VW, Richmond RC, Woolf BAR, et al. Strengthening the reporting of observational studies in epidemiology using Mendelian randomization: the STROBE-MR statement. JAMA. 2021;326(16):1614-1621.
4. Kuo IC, Broman A, Pirouzmanesh A, Melia M. Is there an association between diabetes and keratoconus? Ophthalmology. 2006;113(2):184-190.
