Higher order aberrations in keratoconus .

INTRODUCTION: Keratoconus is a progressive disorder of the cornea that causes thinning (Sedaghat et al. in Sci Rep 11(1):11971, 2021), ectasia, and irregular astigmatism, resulting in poor visual acuity that cannot be corrected with standard sphero-cylindrical spectacle lenses. One feature distinguishing keratoconic corneas is ocular aberrations, manifesting up to five or six times the amount of higher-order aberrations than a normal, healthy eye. These aberrations can cause visual disturbances even at the very early stages of the disease. METHODS: In the past, a diagnosis was derived from clinical symptoms, but technological advances have revealed multiple pre-clinical features, allowing for the differentiation between keratoconic and normal eyes at a much earlier stage. These include anterior and posterior corneal surface elevations, the corneal pachymetry profile, corneal epithelial patterns, wavefront aberration metrics, and corneal biomechanics (Sedaghat et al. in Sci Rep 11(1):11971, 2021).This review discusses the aberrations associated with keratoconus, how to measure them, and treatment methods to minimize their negative influence. CONCLUSIONS: Early diagnosis can lead to early treatment and may allow for arresting progression, thereby improving the long-term prognosis. With the acceleration of refractive surgery, it is important to identify patients with keratoconus, as they are usually contraindicated for refractive surgery.

A high body mass index strengthens the association between the time of eye rubbing and keratoconus in a Chinese population: a case control study.

BACKGROUND: Although body mass index (BMI) and eye rubbing are linked to an increased risk of keratoconus (KC), the interactive effect of eye rubbing and BMI on KC is largely unknown. This study aimed to evaluate the independent and interactive effects of BMI and eye rubbing on KC and to further explore the role of environmental factors on the occurrence of KC. METHODS: A total of 621 individuals (291 KC patients and 330 control individuals) were enrolled in this hospital­based study on KC patients in Central China after individuals missing BMI data were excluded. BMI was calculated as weight in kilograms divided by the square of height in meters. Data on eye rubbing was recorded through face-to-face interviews. Generalized linear regression models were used to analyze associations among BMI, eye rubbing and KC. Interaction plots were used to describe the interactive effects of BMI and eye rubbing on KC. RESULTS: The ß and 95% confidence interval (CI) were 0.923 (0.112, 1.733) (p = 0.026) and 3.356 (1.953, 4.759) (p < 0.001), respectively, for the effect of each 10 kg/m2 increase in BMI and each 1 min increase in eye rubbing on KC. The interaction of BMI and eye rubbing were positively correlated with KC (p < 0.001). CONCLUSION: These findings suggested that a high BMI aggravated the negative effect of eye rubbing on KC, implying that individuals with a high BMI may be more susceptible to exposure to eye rubbing, which is related to an increased risk of KC.

The association between keratoconus and allergic eye diseases: A systematic review and meta-analysis.

BACKGROUND: To investigate the association between keratoconus (KC) and allergic eye diseases, eye rubbing, and atopy. METHODS: PubMed, Web of Science, Scopus, and Cochrane databases were searched for studies investigating eye allergy, atopy, and eye rubbing as risk factors for KC up to April 2021. Two authors independently screened all titles and abstracts against the predefined inclusion and exclusion criteria. The study analysed the prevalence of KC and its risk factors, including eye rubbing, family history of KC, atopy, and allergic eye diseases. The National Institutes of Health Study Quality Assessment Tool was used. Pooled data are presented as odds ratios (OR) and 95% confidence intervals (CI). The analysis was conducted using RevMan version 5.4 software. RESULTS: The initial search yielded 573 articles. After screening, 21 studies were identified for qualitative analysis and 15 for quantitative synthesis. A significant association was found between KC and eye rubbing (OR = 5.22, 95% CI [2.80, 9.75], p < 0.00001), family history of KC (OR = 6.67, 95% CI [4.77, 9.33], p < 0.00001), and allergies (OR = 2.21, 95% CI [1.57, 3.13], p < 0.00001). However, no significant association was found between KC and allergic eye disease (OR = 1.82, 95% CI [0.37, 8.97], p = 0.46), atopy (OR = 1.54, 95% CI [0.58, 4.09], p = 0.39), allergic rhinitis (OR = 0.85, 95% CI [0.54, 1.33], p = 0.47), smoking (OR = 0.96, 95% CI [0.76, 1.21], p = 0.73), and asthma (OR = 1.58, 95% CI [0.99, 2.53], p = 0.05). CONCLUSION: Significant associations were observed between KC and eye rubbing, family history, and allergy, but not with allergic eye disease, atopy, asthma, and allergic rhinitis.

[Keratoconus: main lines of research]. / Keratokonus: osnovnye napravleniya issledovanii.

Keratoconus (KC) research focuses on studying pathogenesis, advancing diagnostic techniques and methods of correction and treatment. The working hypothesis for KC etiopathogenesis is based on abnormalities in distribution of microelements in the cornea and its potential influence on the processes of stromal collagen disorganization. Improvement of early diagnosis of KC is associated with evaluation of microstructural changes in the cornea using computerized methods such as Scheimpflug camera and high-definition optical methods for visualization of initial signs of a pigment ring. The main optimization directions of KC contact correction are associated with increasing gas permeability of the material, improving lens design and methods of lens fitting. Customized fitting of gas-permeable scleral hard contact lenses with consideration of topographic features of the anterior corneal surface allows achieving stable lens positioning and preserving the tear gap between the lens and the cornea. Alternative methods of correcting the refraction component of KC are associated with surgical interventions involving increase in corneal volume in the paracentral area. Implantation of corneal ring segments should be considered as an alternative to correction of refractive errors in cases with unsatisfactory individual subjective tolerance and insufficient patient compliance with contact correction. Femtolaser-assisted implantation of intrastromal allotransplants along with a decrease in the degree of spherical and astigmatic components of refractive errors contribute to prevention of KC progression. Advancement of techniques of corneal collagen cross-linking for prevention of KC progression is aimed at reducing the risk of developing post-operative complications directly related to the extent of intraoperative deepithelization. Limiting corneal ectatic area by implantation of intrastromal allotransplants can be considered an alternative approach. Deep anterior lamellar keratoplasty and penetrating keratoplasty are the surgeries of choice in replacing altered corneal layers in KC. With regard to the modern trends in selective keratoplasty, selective replacement of the cornea in lamellar keratoplasty reduces the rate of injuries and the risk of tissue reaction.

Corneal Confocal Analysis after Scleral Lens Wear in Keratoconus Patients: A Pilot Study.

SIGNIFICANCE: Scleral lenses rely on the scleroconjunctival region without bearing the cornea, which could improve the symptoms and modify the corneal nerve plexus morphology. PURPOSE: This study aimed to evaluate symptoms and changes in corneal nerve plexus morphology and density of Langerhans cells in keratoconus patients with and without intrastromal corneal ring before and after scleral lens wear. METHODS: Sixteen scleral lens wearers with keratoconus were recruited for this short-term experimental pilot study. Subjects were divided into two groups: keratoconus group and intrastromal corneal ring segment group. All subjects were examined in two visits: baseline (before scleral lens wear) and after 6 months of scleral lens wear, after lens removal. The Schirmer I test, the Ocular Surface Disease Index, tear breakup time, and in vivo confocal microscopy were evaluated. RESULTS: The mean age was 42.33 ± 11.27 years. A significant decrease in tear breakup time was found in the total group ( P = .01, Wilcoxon) compared with baseline. Ocular Surface Disease Index score had decreased after 6 months of scleral lens wear in the keratoconus with intrastromal corneal ring segment subgroup ( P = .03, Wilcoxon) and in the total group ( P = .001, Wilcoxon). No statistical changes in nerve density, tortuosity, and ramification were found for either the total group or the subgroup. However, the mean nerve length was higher in all groups, especially in the keratoconus subgroup ( P = .03, Wilcoxon) after 6 months of scleral lens wear. Regarding optical density, the total group showed a significant increase after 6 months of wearing ( P = .02, Wilcoxon). Finally, Langerhans cell density was not statistically different in any group. CONCLUSIONS: These results suggest that scleral lens wearing improves the symptoms and increased the mean length nerves after 6 months of wear use in keratoconus patients.

The association between keratoconus and allergic eye diseases: A systematic review and meta-analysis.

BACKGROUND: To investigate association between keratoconus and allergic eye diseases, eye rubbing, and atopy. METHODS: PubMed, Web of Science, Scopus, and Cochrane were searched for relevant published studies from inception to April 2021 without restrictions or filters. We included case-control, cohort, and cross-sectional studies that investigated eye allergy, atopy, or eye rubbing as possible risk factors for KC. Two authors independently screened all titles and abstracts against predefined inclusion and exclusion criteria. This study analysed keratoconus prevalence and risk factors including eye rubbing, family history of keratoconus, atopy, and allergic eye diseases. The National Institute of Health Study Quality Assessment tool was utilised. Pooled data were presented as odds ratio (OR) and 95% confidence intervals (CI). Analysis was conducted using RevMan version 5.3 software. RESULTS: Out of 573 articles, we excluded 161 duplicates than 361 articles by title and abstract screening. The remaining 51 articles underwent full-text screening, and 29 articles were excluded. Twenty-one studies were included in the qualitative synthesis and fifteen for quantitative synthesis. There was no significant association found between KC and allergic eye diseases (OR = 1.03, 95% CI [0.96, 1.11], p = 0.45), eye rubbing (OR = 1.59, 95% CI [0.70, 3.63], p = 0.27), or atopy (OR = 1.08, 95% CI [0.80, 1.44], p = 0.62). CONCLUSION: No significant association was observed between KC and allergic eye disease, eye rubbing, or atopy. Further prospective studies are needed to clarify and validate these findings.

The Underlying Relationship between Keratoconus and Down Syndrome.

Keratoconus (KC) is one of the most significant corneal disorders worldwide, characterized by the progressive thinning and cone-shaped protrusion of the cornea, which can lead to severe visual impairment. The prevalence of KC varies greatly by ethnic groups and geographic regions and has been observed to be higher in recent years. Although studies reveal a possible link between KC and genetics, hormonal disturbances, environmental factors, and specific comorbidities such as Down Syndrome (DS), the exact cause of KC remains unknown. The incidence of KC ranges from 0% to 71% in DS patients, implying that as the worldwide population of DS patients grows, the number of KC patients may continue to rise significantly. As a result, this review aims to shed more light on the underlying relationship between KC and DS by examining the genetics relating to the cornea, central corneal thickness (CCT), and mechanical forces on the cornea, such as vigorous eye rubbing. Furthermore, this review discusses KC diagnostic and treatment strategies that may help detect KC in DS patients, as well as the available DS mouse models that could be used in modeling KC in DS patients. In summary, this review will provide improved clinical knowledge of KC in DS patients and promote additional KC-related research in these patients to enhance their eyesight and provide suitable treatment targets.

The Role of Estriol and Estrone in Keratoconic Stromal Sex Hormone Receptors.

Keratoconus (KC) is a progressive corneal thinning disease that manifests in puberty and worsens during pregnancy. KC onset and progression are attributed to diverse factors that include: environmental, genetics, and hormonal imbalances; however, the pathobiology remains elusive. This study aims to determine the role of corneal stroma sex hormone receptors in KC and their interplay with estrone (E1) and estriol (E3) using our established 3D in vitro model. Healthy cornea stromal cells (HCFs) and KC cornea stromal cells (HKCs), both male and female, were stimulated with various concentrations of E1 and E3. Significant changes were observed between cell types, as well as between males and females in the sex hormone receptors tested; androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERα), and estrogen receptor beta (ERß) using Western blot analysis. E1 and E3 stimulations in HCF females showed AR, PR, and ERß were significantly upregulated compared to HCF males. In contrast, ERα and ERß had significantly higher expression in HKC's females than HKC's males. Our data suggest that the human cornea is a sex-dependent, hormone-responsive tissue that is significantly influenced by E1 and E3. Therefore, it is plausible that E1, E3, and sex hormone receptors are involved in the KC pathobiology, warranting further investigation.

Risk factors and severity of keratoconus on the East Coast of China.

PURPOSE: This study aims to investigate the characteristics, potential risk factors and associated severity of keratoconus on the east coast of China. METHODS: In this case-control study, patients diagnosed with keratoconus were invited to fill in the online electronic questionnaire designed with the help of the App named WenJuanXing. Several questions like, sex, age of diagnosis and eye care habits were administered to each subject through this e-questionnaire. Corneal topographies at diagnosis taken from Pentacam were also collected. RESULTS: Totally 391 Chinese keratoconus outpatients were enrolled in this study, among which 159 patients were newly diagnosed. Only three patients (0.77%) had a positive family history of keratoconus. Atopy could be identified in 66.0% of our patients. A total of 357 patients (91.3%) mentioned the habit of eye rubbing, with 191 patients (48.8%) rubbing their eyes frequently. Patients with younger age at onset (p = 0.005), male sex (p = 0.042), frequent eye rubbing (p = 0.003) and smoke (p = 0.002) were found significantly associated with increased risk of acute hydrops. In newly diagnosed patients, 79.9% had the maximum keratometry (Kmax) more than 52D, with males and patients aged 21-30 being even more serious (p = 0.009; p = 0.005). Besides, in patients aged over 21, frequent eye rubbing was significantly associated with steeper Kmax and more severe astigmatism (all p < 0.05). CONCLUSION: Our results suggest that frequent eye rubbing is closely related to the severity of keratoconus in Chinese patients. Chinese keratoconus patients always had much serious disease condition at the time of diagnosis. Thus, increasing the publicity of keratoconus and advocating appropriate eye care habits are needed urgently in China. REGISTRATION: The research was retrospectively registered, and the trial registration number is ChiCTR1900021273, and the registration date is 2019/02/09.

Genetics vs chronic corneal mechanical trauma in the etiology of keratoconus.

Both genetic and environmental factors have been considered to play a role in the etiology keratoconus. Eye rubbing, and more recently eye compression due to sleeping position, have been identified to be highly related to the condition, and are present in a high percentage of patients. Today, the predominant model is that these factors can provide the "second hit" necessary to generate the condition in a genetically susceptible individual. In addition, the extremely high prevalence in Arab populations, where endogamy could play a role, the high concordance rate in monozygotic twins, and the presence of family history of the condition between 5 and 23% of cases, support a genetic influence. Segregation analysis studies suggest that keratoconus is a complex non-Mendelian disease. Results from linkage analysis, next generation sequencing studies and genome-wide association studies also have suggested that genetic factors are involved in the condition. Recently, it has been proposed that mechanical trauma (i.e. eye rubbing or eye compression at night), is a sine quanon condition for the onset of keratoconus, and quite possibly its only cause. There are various arguments for and against this hypothesis. Indeed, it is possible, as initially suggested around 55 years ago, that the term "keratoconus" include diverse phenotypically similar conditions, which are actually of different etiology.

Differences in sphere-forming cells from keratoconic and normal corneal tissue: Implications for keratoconus pathogenesis.

Keratoconus is primarily an anterior corneal disorder of unclear aetiology. Stem cells may play a role in the perpetuation of keratoconus, although this has yet to be definitively established. Sphere-forming cells from normal human donor corneas have previously been shown to be a heterogenous mix of epithelial, stromal, stem and progenitor cell components which have potential for treatment of corneal dystrophies. Our work set out to isolate and characterise sphere-forming cells from human keratoconic tissue. Keratoconic donor corneas were successfully used to culture sphere-forming cells in vitro. Time lapse imaging of these spheres on a collagen surface over 8 days revealed keratoconic spheres lack the ability to maintain a central core and have diminished ability to repopulate the surface. Immunocytochemistry showed positive labelling for the stem cell marker 'Adenosine triphosphate-binding cassette sub-family B member 5 (ABCB5)' indicating stem cell retention and the myofibroblast marker alpha smooth muscle actin indicating wound repair while droplet digital Polymerase Chain Reaction confirmed an increase in expression of stem and stromal cell markers in keratoconic spheres compared to spheres cultured from normal donors at day 7 post-placement. Keratoconic sphere-forming cells showed a diminished repopulation ability, a faster wound healing response and lack of central core retention. These results suggest stem cells in keratoconus may be in an elevated state of wound repair and unable to respond appropriately to further injury in corneal maintenance. Sphere forming cell populations in keratoconus appear to be different to those isolated from normal corneas and this may be an important consideration in unearthing keratoconus aetiology.

The role of environment in the pathogenesis of keratoconus.

PURPOSE OF REVIEW: This study was conducted to demonstrate the importance of the environment in keratoconus (KC) genesis. RECENT FINDINGS: Genetic-related connective tissue disorders demonstrate the inconsistency of theories regarding KC pathogenesis since no corneal steepening was observed in the majority of these patients. Despite recent advances and decades of research into the genetics of KC, the identification of disease-causing KC genes has been frustrating. Variants found based on genome-wide and next-generation sequencing only seem to account for a small number of cases or play a limited role in KC pathogenesis. SUMMARY: The literature shows that mechanical manipulation may be the common underlying factor or the indispensable act precipitating the cascade of events leading to permanent corneal deformation. Hence, ophthalmologists have the opportunity to increase patient awareness about eye manipulation repercussions and treatment for ocular surface disorders. VIDEO ABSTRACT: http://links.lww.com/COOP/A42.

Eye rubbing in the aetiology of keratoconus: a systematic review and meta-analysis.

PURPOSE: Keratoconus is a potentially blinding condition that slowly deforms the cornea in young people. Despite the increasing prevalence of keratoconus, the exact aetiology of the condition is unknown. This first systematic review examines the evidence of eye rubbing and its association with keratoconus and presents the findings of the meta-analysis. METHODS: Two independent reviewers searched the electronic databases for all potential articles published from 1st of January 1900 to 31st of July 2020 on eye rubbing and keratoconus. The researchers assessed the methodological quality of the studies using the Newcastle-Ottawa scale for observational studies. The assessment for statistical heterogeneity was estimated using chi-square and I-square (I2) tests. A p value of < 0.05 was considered as statistically significant and I2 < 30% as homogenous. Begg funnel plot was used to interpret the asymmetry or small study effects. RESULTS: Eight case-control studies were included in this systematic review. Two studies assessed eye rubbing without odds ratios and thus were excluded. The pooled odds ratios for the six remaining studies included in the meta-analysis was 6.46 (95% CI 4.12-10.1). The study results were heterogenous (I2 = 71.69 [95% CI 35.14-87.88]). All the studies scored moderate quality methodology on the Newcastle-Ottawa scale. Begg funnel plot showed asymmetry supporting heterogeneity. CONCLUSION: Eye rubbing showed consistent association with keratoconus. However, the current evidence is limited to only a small number of case-control studies which present as heterogeneous and of sub-optimal methodological quality. Additionally, the cause-effect temporal relationship cannot be determined. Further studies are needed to address this intricate relationship of eye rubbing and its induction, ongoing progression, and severity of keratoconus.

The Characteristics and Risk Factors of Very Asymmetric Keratoconus.

PURPOSE: To characterize very asymmetric keratoconus (KC) in terms of clinical demographics and risk factors in the Japanese population. METHODS: We retrospectively reviewed the clinical records of patients with very asymmetric KC attending a university hospital. Patients with very asymmetric KC had defined clinical KC in one eye and normal topography in the fellow eye. All patients completed a questionnaire on potential risk factors (family history of KC, atopy, asthma, allergy, heart disease, sleep apnea, Down syndrome, eye rubbing, prone sleep position, and dominant hand). These data were compared with those of patients with clinical or topographic KC in both eyes. Subgroup analysis of very asymmetric KC eyes were performed based on the KC status: mild and severe. RESULTS: We retrospectively investigated 66 patients with very asymmetric KC and 505 patients with KC. Patients reported eye rubbing (53%-56%), allergy (62%-63%), and atopy (28%-29%) in both groups. There was no significant difference in terms of risk factors between the two groups. Approximately half of the 66 patients with very asymmetric KC had KC eyes ipsilateral to the dominant hand. Subgroup analysis of very asymmetric KC showed that atopy and asthma were more frequent in the mild KC group than in the severe KC group. Forty-four of 60 patients (73.3%) were using corneal, rigid, gas-permeable contact lenses (corneal GPs) for the KC eye, of which 30 patients (68.2%) were also using a corneal GP for the fellow eye. CONCLUSIONS: The patient-reported frequency of eye rubbing, allergy, and atopy were similar between KC and very asymmetric KC. Furthermore, we found no association between hand dominance and KC laterality.

Model Systems for Evidencing the Mediator Role of Riboflavin in the UVA Cross-Linking Treatment of Keratoconus.

Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.

Risk factors and association with severity of keratoconus: the Australian study of Keratoconus.

SIGNIFICANCE: Our results show that asthmatic patients tend to have more severe KC and thus close monitoring for disease progression would be advised, and appropriate treatment strategies may be actioned stabilise the condition that may reduce the need for future corneal transplantation. PURPOSE: To explore a wide range of risk factors associated with the severity of keratoconus (KC). METHODS: A cross-sectional study of KC patients was undertaken in Melbourne, Australia. A questionnaire addressing age, gender, educational background, ocular and medical history, smoking and alcohol consumption, and physical examination comprising anthropometric measurements was collected; eye examination was undertaken. The associations between a range of risk factors and the severity of KC were determined using univariate and multivariable linear regression analyses. RESULTS: A total of 260 KC subjects were included in this study. Mean age of subject was 35.5 (SD = 14.8) years and the majority of the subjects were European 171 (68.2%). Initial univariate regression analysis identified the following risk factors at the p < 0.1 level with KC: higher body mass index, smoking cigarettes, diabetes, rheumatoid arthritis and asthma were associated with increased severity of KC, whereas eczema was associated with less severe KC. Following multivariable regression analysis, only asthma remained as a significant risk factor associated with 2.2 diopters (D) steeper average mean keratometry compared to KC subjects having no asthma [p = 0.03; ß = 2.18; 95% confidence intervals: 1.22, 4.14]. CONCLUSION: Our study describes the comprehensive assessment of all the known risk factors in a large KC cohort recruited in Australia. Our study has reported asthma as the only risk factor found to be significantly associated with the severity of KC. The results of this study allow us to better understand the aetiology of KC and such knowledge could be useful in instigate systemic management of patients to slow or prevent KC.

[Possibilities of increasing contact lens tolerance in keratoconus (a clinical case study)]. / Vozmozhnosti povysheniya perenosimosti kontaktnoi korrektsii pri keratokonuse (klinicheskoe nablyudenie).

Optical correction of keratoconus (KC) is intended to simultaneously solve two tasks: elimination of myopic defocus and irregular astigmatism. In terms of the latter, hard contact lenses (HCL) should be considered as the first-choice method for optical correction of KC. HCL are currently the most effective means of optical correction of refractive errors induced by KC. Despite this, it should be noted that adherence of patients to this method of correction does not always correspond to results. Most often, limitations of HCL use in KC are associated with the so-called intolerance of correction. The term «correction intolerance¼ should be considered as a general complex of potential subjective symptoms and clinical manifestations that limit the possibility of using a particular method of optical correction. In this clinical observation, subjective discomfort when wearing lenses was practically eliminated by changing the design of the lens and switching from corneal to scleral HCL. The second problem was caused by clinical manifestations of corneal hypoxia (growth of newly formed vessels in the limbal region of the cornea) and attempts to solve it were associated with improved tear production and increased oxygen permeability of the material HCL are made of. The observed stabilization of the growth of newly formed vessels should be considered as a positive (although in need of dynamic evaluation) result of these therapeutic measures.

Risk factors for postlaser refractive surgery corneal ectasia.

PURPOSE OF REVIEW: To summarize newly reported and update previously known risk factors for post laser vision correction (LVC) corneal ectasia. RECENT FINDINGS: Advances in corneal topography and tomography have improved detection of preclinical ectasia-related changes. This has allowed for enhanced screening of surgical candidates. There are also known genetic predispositions for corneal ectasia, and recent genetic analyses have revealed various genes and inflammatory biomolecular markers related to corneal biomechanical integrity. Other models of risk assessment such as finite element biomechanical modeling and artificial intelligence tools have shown promise in detecting more subtle risk factors, such as those related to mechanical strain. SUMMARY: Risk factors for post-LVC corneal ectasia involve both surgery and patient-specific characteristics, such as topographic and tomographic abnormalities, younger age, thinner preoperative corneas, and residual stromal beds, high myopia, and higher percentage tissue altered. Preoperative risk stratification has helped to decrease the incidence of postoperative ectasia, a trend which will likely continue with advancements in analytic tools and better understanding of underlying genetic predispositions.

Incorrect sleeping position and eye rubbing in patients with unilateral or highly asymmetric keratoconus: a case-control study.

PURPOSE: To evaluate eye rubbing and sleeping position in patients with Unilateral or Highly Asymmetric Keratoconus (UHAKC). METHODS: Case-control study of consecutive UHAKC patients diagnosed at the Rothschild Foundation. Controls were age- and sex-matched, randomly selected refractive surgery clinic patients. Patients self-administered questionnaires regarding their family history of keratoconus, eye rubbing, and sleeping habits. All the eyes underwent a comprehensive ocular examination. Logistic regression was used to analyze univariate and multivariate data to identify risk factors for keratoconus. RESULTS: Thirty-three UHAKC patients and 64 controls were included. Univariate analyses showed that daytime eye rubbing [OR = 172.78], in the morning [OR = 24.3], or in eyes with the steepest keratometry [OR = 21.7] were significantly different between groups. Allergy [OR = 2.94], red eyes in the morning [OR = 6.36], and sleeping on stomach/sides [OR = 14.31] or on the same side as the steepest keratometry [OR = 94.72] were also significantly different. The multivariate model also showed statistical significance for most factors including daytime eye rubbing [OR = 134.96], in the morning [OR = 24.86], in the steepest eye [OR = 27.56], and sleeping on stomach/sides [OR = 65.02] or on the steepest side [OR = 144.02]. A univariate analysis in UHAKC group, comparing the worse and better eye, showed that eye rubbing [OR = 162.14] and sleeping position [OR = 99.74] were significantly (p < 0.001) associated with the worse eye. CONCLUSION: Our data suggests that vigorous eye rubbing and incorrect sleeping position are associated with UHAKC. This is especially true in rubbing the most afflicted eye, and contributory sleep position, including positions placing pressure on the eye with the steepest keratometry.

Kayser-Fleischer ring with keratoconus: a coincidence? A case report.

BACKGROUND: It is rare for hepatolenticular degeneration [Wilson's disease (WD)] to occur along with keratoconus (KC). In our report, a teenager was diagnosed with WD because of the discovery of Kayser-Fleischer (KF) ring in the cornea, and concomitant KC was found. CASE PRESENTATION: A 19-year-old male was diagnosed with KC due to a rapid decline in visual acuity within a short period of time. Ocular examination revealed the presence of ring-shaped, dense, brown sediment at the Descemet membrane of the bilateral limbus cornea, exhibiting characteristics similar to those of KF ring. Then, the patient was referred to the Department of Neurology and diagnosed with asymptomatic WD. During the next 5 years of follow-up, the patient has worn RGP lenses, routinely taken drugs that inhibit copper absorption and promote copper excretion, and maintained a low-copper diet. He has never exhibited obvious systemic symptoms associated with WD, such as neurological, mental, or hepatic dysfunction, and the color of the KF ring has grown obviously lighter. Moreover, the morphology of the cornea has stabilized. CONCLUSION: Only one report of WD combined with KC was found in the literature. So far, there is no evidence of a correlation between the occurrence of the two diseases. However, a low-copper diet and active copper-reducing therapy may have played a role in stabilizing the patient's condition in this case.