Corneal Morphologic Characteristics in Patients With Down Syndrome

Current concepts in the management of cataract with keratoconus

This review analyzed all pertinent articles on keratoconus (KCN) and cataract surgery. It covers preoperative planning, intraoperative considerations, and postoperative management, with the aim of providing a simplified overview of treating such patients. Preoperatively, the use of corneal cross-linking, intrastromal corneal ring segments, and topo-guided corneal treatments can help stabilize the cornea and improve the accuracy of biometric measurements. It is important to consider the advantages and disadvantages of traditional techniques such as penetrating keratoplasty and deep anterior lamellar keratoplasty, as well as newer stromal augmentation techniques, to choose the most appropriate surgical approach. Obtaining reliable measurements can be difficult, especially in the advanced stages of the disease. The choice between toric and monofocal intraocular lenses (IOLs) should be carefully evaluated. Monofocal IOLs are a better choice in patients with advanced disease, and toric lenses can be used in mild and stable KCN. Intraoperatively, the use of a rigid gas permeable (RGP) lens can overcome the challenge of image distortion and loss of visual perspective. Postoperatively, patients may need updated RGP or scleral lenses to correct the corneal irregular astigmatism. A thorough preoperative planning is crucial for good surgical outcomes, and patients need to be informed regarding potential postoperative surprises. In conclusion, managing cataracts in KCN patients presents a range of challenges, and a comprehensive approach is essential to achieve favorable surgical outcomes.

Mendelian Randomisation Analysis of Causal Association between Lifestyle, Health Factors, and Keratoconus

Keratoconus (KC), a leading cause of vision impairment, has an unclear aetiology. This study used Mendelian randomization (MR) to explore the causal links between various factors (smoking, asthma, Down syndrome, inflammatory bowel disease, atopic dermatitis, and serum 25-hydroxyvitamin D levels) and KC. A two-sample MR design, grounded in genome-wide association study (GWAS) summary statistics, was adopted using data from FinnGen, UK Biobank, and other GWAS-related articles. The inverse-variance weighted (IVW) method was employed, complemented by the Wald ratio method for factors with only one single-nucleotide polymorphism (SNP). Sensitivity and stability were assessed through Cochrane's Q test, the MR-Egger intercept test, MR-PRESSO outlier test, and the leave-one-out analysis. The IVW results for the ORA (Ocular Response Analyzer) biomechanical parameters indicated significant associations between tobacco smoking (CH: p < 0.001; CRF: p = 0.009) and inflammatory bowel disease (CH: p = 0.032; CRF: p = 0.001) and corneal biomechanics. The Wald ratio method showed tobacco smoking was associated with a lower risk of KC (p = 0.024). Conversely, asthma (p = 0.009), atopic dermatitis (p = 0.012), inflammatory bowel disease (p = 0.017), and serum 25-hydroxyvitamin D levels (p = 0.039) were associated with a higher risk of KC by IVW, and the same applied to Down syndrome (p = 0.004) using the Wald ratio. These results underscore the role of corneal biomechanics as potential mediators in KC risk, warranting further investigation using Corvis ST and Brillouin microscopy. The findings emphasise the importance of timely screening for specific populations in KC prevention and management.

Keratoconus in Down syndrome: Prevalence, risk factors, severity and corneal tomographic characteristics

BACKGROUND

This study investigated the prevalence, risk factors and severity of corneal tomographic features of keratoconus in Down syndrome (DS). Additionally, previous studies indicate anomalous corneal features in DS, without keratoconus, this study characterised corneal features in DS without keratoconus.

METHODS

This prospective observational study included participants with DS ≥10 years old. Keratoconus diagnosis, risk factors and corneal tomographic characteristics were recorded. Participants underwent slit-lamp biomicroscopy, Scheimpflug corneal tomography, corneal topography and autorefraction. A diagnosis of keratoconus (DS-KC), suspect keratoconus (DS-SK) and non-keratoconus (DS-NK) was made based on expert review of scans by three fellowship trained anterior segment ophthalmologists. Corneal tomography parameters from one eye of each participant were analysed.

RESULTS

Keratoconus affected 50 (26.3%) of 190 participants, diagnosed by corneal tomography, topography or slit-lamp signs. Corneal hydrops affected 14.0% of DS-KC participants. Eye rubbing was a significant risk factor for keratoconus (p = 0.036). 175 (92%) participants could undertake corneal tomography of which tomography assessment alone identified 47 (26.9%) DS-KC participants, 64 (36.6%) DS-SK participants and 64 (36.6%) DS-NK participants. Significant differences (p < 0.001) were identified when the DS-KC, DS-SK and DS-NK groups were compared in maximum keratometry and posterior elevation at the thinnest point respectively: median (interquartile range) 50.20 (10.30D), 47.60 (1.95D), 46.50 (2.40D); 24.0 (38.00 μm), 10.00 (13.75 μm), 8.00 (6.00 μm). The DS-SK and DS-NK cohorts had similar minimum pachymetry, however, had several significantly different parameters among which included greater maximum keratometry, posterior elevation at the thinnest point in the DS-SK group.

CONCLUSIONS

Keratoconus is common in DS. Keratoconus screening with corneal tomography is recommended for early detection.

Anterior segment indices in mentally retarded children

To compare the anterior segment indices between mentally retarded and normal children. The current study was conducted as a cohort. In this study, 73 mentally retarded and 76 normal children were selected from normal school and special schools for mentally retarded children using random cluster sampling method. Mental retardation in children was confirmed by a psychologist. Optometry examinations including visual acuity and refraction were performed for all participants, and ultimately, corneal imaging measurements were taken by Pentacam. The mean age of mentally retarded and normal children was of 13.30 ± 1.83 and 13.05 ± 1.82 years, respectively (P = 0.180). A multiple generalized estimating equations model demonstrated that there is a significant association between central corneal thickness (CCT) (coef = 1.011, P < 0.001), corneal diameter (CD) (coef = 0.444, P = 0.046), anterior chamber depth (ACD) (coef = 0.23), P < 0.001) and index of vertical asymmetry (IVA) (coef = 0.12, P < 0.001) and mental retardation. Cerebral palsy children had higher keratoconus index (KI), central keratoconus index (CKI), index of height asymmetry(IHA), and index of height decentration (IHD) compared to those without cerebral palsy (P < 0.05). Children with moderate mental retardation had higher index of surface variance (ISV), IVA, IHA, and IHD than those with mild mental retardation (P < 0.05). The mean and standard deviation of CCT, CD, ACD and IVA index in mentally retarded children were 535.3 ± 46.68 micron, 11.87 ± 0.42 mm, 3.29 ± 0.24 mm and 0.25 ± 0.18 mm, respectively. These indices in the normal group were 525.53 ± 47.52 micron, 11.84 ± 0.38 mm, 3.15 ± 0.28 mm and 0.17 ± 0.05 mm, respectively. The findings of this study showed that some anterior segment indices were different in mentally retarded compared to normal children. Moreover, some keratoconus indicators were worse in cerebral palsy children and children with higher grade mental retardation. So, it is important to consider keratoconus screening in these children.

Systemic Associations with Keratoconus

Keratoconus is a disease of the cornea that results in progressive steepening and thinning of the cornea and subsequent vision loss. It nearly always presents as a bilateral disease, suggesting that there is an underlying abnormality of the corneas that becomes manifest with time. However, the mechanisms underlying the development of keratoconus are largely unknown. Associations reported between keratoconus and systemic diseases are abundant in the literature, and the list of possible associations is very long. We found that atopy, Down syndrome, and various connective tissue diseases were the most frequently cited associations in our broad literature search. Additionally, Diabetes Mellitus has been increasingly studied as a possible protective factor against keratoconus. In this review, we have summarized the evidence for and against these particular systemic conditions and keratoconus and have discussed some of the implications of keratoconus patients having these conditions.

Animal model of corneal ectasia in rabbits by intrastromal injection of type II collagenase

INTRODUCTION

Collagenase II has been used to induce experimental keratoconus in animal models. However, its effect when administered by intrastromal injection has not been studied, so the purpose of this study was to study the effects of intrastromal injection of collagenase II on corneal surface and corneal morphology.

METHODS

Six New Zealand rabbits were used, collagenase II was administered by intrastromal injection (5μL of 2.5mg/mL) in the right eyes and balanced salt solution in the left eyes. Keratometry was performed to evaluate curvature alteration, also at day 7 corneas were obtained and Hematoxylin-Eosin staining was performed to examine morphologic changes. Likewise, changes in type I collagen expression were investigated by Sirius Red staining and semiquantitative PCR.

RESULTS

K1, K2 and Km presented differences in the means with statistically significant changes. The morphological changes that were demonstrated were degradation and irregular arrangement of the corneal stroma, increase in the cellular density of keratocytes and slight cellular infiltration. Finally, it was demonstrated that there is greater expression of type I collagen fibers in the experimental group as opposed to the controls and the thickness of the fibers also increased due to the action of collagenase II, however, in terms of genetics there were no changes in the expression of type I collagen at molecular level between the control and experimental groups.

CONCLUSIONS

Collagenase II administered by intrastromal injection is able to induce changes in the corneal surface and stroma, being able to simulate a model of keratoconus.

The Ophthalmic Manifestations of Down Syndrome

Down Syndrome is one of the most common chromosomal conditions in the world, affecting an estimated 1:400-1:500 births. It is a multisystem genetic disorder but has a wide range of ophthalmic findings. These include strabismus, amblyopia, accommodation defects, refractive error, eyelid abnormalities, nasolacrimal duct obstruction, nystagmus, keratoconus, cataracts, retinal abnormalities, optic nerve abnormalities, and glaucoma. These ophthalmic conditions are more prevalent in children with Down Syndrome than the general pediatric population, and without exception, early identification with thoughtful screening in this patient population can drastically improve prognosis and/or quality of life.

A three-dimensional morpho-volumetric similarity study of Down syndrome keratopathy vs. keratoconus

BACKGROUND

To compare and contrast morpho-volumetric features between Down syndrome (DS) cornea and non-DS keratoconic cornea by three-dimensional (3D) modelling.

METHODS

Forty-three subjects (43 eyes) with DS and 99 patients matching their age and sex (99 eyes) with keratoconus (KC) were included in this single-center cross-sectional study. Main outcome measures were high-order aberrations (HOA), central corneal thickness (CCT), spherical equivalent refraction, and morpho-volumetric parameters established using a 3D corneal model, such as deviation of anterior and posterior corneal apices (D_apexant/D_apexpost) and minimum thickness points (D_mctant/D_mctpost) from corneal vertex, areas of the anterior and posterior surfaces (A_ant/A_post), sagittal area passing through the anterior and posterior corneal apices (A_apexant/A_apexpost) and minimum thickness point (A_mctpost) and corneal volume of the complete cornea (V_total).

RESULTS

Age, gender, spherical equivalent refraction, CCT and V_total were similar between the net on-DS KC and DS groups (P > 0.05), while non-DS KC group had higher HOA than the DS group (P < 0.05). D_apexant, A_ant, A_post and A_apexant showed higher values in the DS group than in the non-DS KC group, whereas D_apexpost showed a reduction in the DS group when compared with the non-DS KC group (P < 0.05).

CONCLUSIONS

This study demonstrated that anterior and posterior corneal apex dynamics were specifically different in DS subjects, as the anterior apex tends to displace more prominently when compared to that from the non-DS KC group, while the posterior apex appears to be more stable than that in non-DS KC, which also support the theory that DS patients suffer from a specific keratopathy, distinctively different to KC but strongly related to it, and probably showing a diversity of corneal phenotypes in all cases of DS.

Vitamin D Supplementation Impacts Systemic Biomarkers of Collagen Degradation and Copper Metabolism in Patients With Keratoconus

Purpose

To evaluate the impact of vitamin D (Vit D) supplementation on systemic biomarkers of collagen degradation, inflammation, oxidative stress, and copper metabolism in adolescent patients with keratoconus (KC).

Methods

This was a prospective observational pilot study. Twenty patients (age range, 16-19 years) presenting KC and Vit D insufficiency (<30 ng/mL) were included. Vit D supplementation was prescribed by their general practitioner as per the standard of care. Patients were followed up for 12 months. At each visit, best spectacle-corrected visual acuity (BSCVA), maximal keratometry (Kmax), and thinnest corneal thickness (TCT) were evaluated. The primary outcome of the study was the proportion of patients with Kmax progression of less than 1 D throughout the 12-month follow-up time. Blood samples were collected at different time points to evaluate Vit D levels and systemic markers of collagen degradation, inflammation, oxidative stress, and copper metabolism by ELISA or RT-PCR.

Results

Lower Vit D levels in the plasma were correlated with higher levels of systemic biomarkers of collagen degradation. Vit D supplementation increased the cell availability of copper. Moreover, stabilization of KC progression was found in 60% of patients (72% of eyes) after 12 months with Vit D supplementation. BSCVA, Kmax, and TCT rates remained stable during the observation period.

Conclusions

Our findings support that Vit D administration could affect ocular and systemic biomarkers in KC and illuminate a possible mechanism that can be used to develop new treatment alternatives.

Translational Relevance

Although KC therapy currently relies exclusively on surgical procedures, Vit D supplementation may offer a non-invasive and inexpensive alternative with minimal associated side effects.

Corneal characteristics in Down syndrome patients with normal and keratoconic cornea

Purpose

To determine the reference range of corneal indices in Down syndrome patients with normal corneas (DS-N) and to compare it with the corneal indices in Down syndrome patients with keratoconic corneas (DS-KC).

Methods

A study was conducted using the data of 154 eyes of 154 DS-N and 25 eyes of 25 DS-KC patients. Eighteen indices related to thickness, anterior chamber, keratometry, elevation, and aberrations routinely used for KC diagnosis were extracted from the Pentacam.

Results

The mean age of the participants in DS-N and DS-KC groups was 16.73 ± 4.70 and 16.56 ± 4.22 years (P = 0.852). In the DS-N group, 95% CI were 511.65–520.31 for minimum corneal thickness, 2.97–3.07 for anterior chamber depth (ACD), 46.83–47.37 for maximum keratometry (Kmax), 46.13–46.62 for zonal Kmax at 3 mm, 0.35–0.58 for inferior-superior asymmetry (I-S value), 1.56–1.88 for Belin/Ambrósio display-total deviation, 8.65–10.79 for best-fit-sphere posterior elevation at the thinnest point, and 0.18–0.22 for corneal vertical coma. The age-related change in I-S value and corneal spherical aberration (SA) was significant (both P < 0.05). There were significant inter-gender differences in 11 indices; the female DS patients had shallower, steeper, more elevated, and more aberrated corneas (all P < 0.05). There were significant differences in all indices except for ACD (P = 0.372) and corneal SA (P = 0.169) between DS-N and DS-KC groups.

Conclusion

In DS patients aged 10–30 years, the reference ranges of corneal indices are different from the range reported for non-DS subjects and are close to values reported for mild KC non-DS cases. The normal values are different between DS male and female; hence, sex-specific ranges should be considered for diagnosis of corneal abnormality in DS patients.

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 Impact of Repetitive and Prolonged Eye Rubbing on Corneal Biomechanics

PURPOSE

To evaluate the effect of simulated repetitive eye rubbing on the corneal biomechanics of porcine eyes using an ex vivo model system.

METHODS

The average rubbing force that patients with keratoconus apply to their eyelids was previously determined. Fresh porcine eyes with eyelids were either exposed to 10,500 rub cycles from a custom-built eye rubbing machine that rubbed with a similar force to knuckle human eye rubbing (n = 33) or no rubbing at all (control; n = 37). A total of 10,500 rubs are equivalent to 1 year of rubbing six times daily, five movements per rub. The corneal biomechanical properties of these eyes were then tested by measuring the elastic modulus of 5-mm strips.

RESULTS

The elastic modulus at the range of 1% and 5% of strain was 1.219 ± 0.284 and 1.218 ± 0.304 N/mm² in the eye rubbing group and the no-rub control group, respectively. Corneal stiffness was similar in both groups (P = .984).

CONCLUSIONS

The threshold to induce biomechanical changes (purely by eye rubbing) must be higher than 10,500 rubbing movements, suggesting that occasional eye rubbing may not affect corneal biomechanics in normal eyes, and likely only triggers keratoconus progression in predisposed corneas. Further in vivo studies assessing the impact eye rubbing has on inflammatory activity and the biomechanical properties of weakened corneas is warranted. [J Refract Surg. 2022;38(9):610-616.].

Corneal Epithelium Asymmetry in Children With Atopy: The Effect of Hand Dominance

Purpose

To evaluate the effect of eye rubbing on the epithelial thickness profile in tomographically normal corneas by AS-OCT and to compare right and left eyes in right-handed children.

Methods

Thirty right-handed boys (mean age 11.2 years) with ocular allergy and history of eye rubbing were evaluated using Scheimpflug (Pentacam HR, Oculus Wetzlar, Germany) and anterior segment optical coherence tomography. Epithelial thickness (ET) and full corneal thickness (CT) parameters were compared between right and left eyes with a non-parametric Mann–Whitney test. A p-value lower than 0.05 was considered for statistical significance.

Results

No eyes had topometric nor tomographic criteria for keratoconus. The min-max ET was lower in right eyes (−2.8 µm vs −3.5; p = 0.02). The difference between inferior and superior (I-S) octants was lower in right eyes (1.1 µm vs 1.9 µm; p = 0.03) as a result of inferotemporal thinning. The highest ET difference was registered between nasal and temporal octants and was more pronounced in the right eyes (2 µm vs 3.1 µm; p < 0.001).

Conclusion

AS-OCT analyses reveal different epithelial thickness patterns between the eyes in young atopic patients, likely eye rubbers. Inferior and temporal epithelial thickness seem to be more affected by thinning in the eye on the side of the dominant hand.

Comparative Contralateral Randomized Clinical Trial of Standard (3 mW/cm2) Versus Accelerated (9 mW/cm2) CXL in Patients With Down Syndrome: 3-Year Results

PURPOSE

To compare the long-term results of accelerated corneal cross-linking (CXL) (9 mW/cm², 10 min) with standard CXL (3 mW/cm², 30 min) in patients with Down syndrome who had keratoconus.

METHODS

In this contralateral randomized clinical trial, 27 patients with Down syndrome aged 15.78 ± 2.46 years (range: 10 to 19 years) were enrolled. CXL was performed using the KXL System (Avedro, Inc) under general anesthesia, and patients were followed up for 3 years. The main outcome measure was a change in average keratometry in the 3-mm zone around the steepest point (zonal Kmax-3mm). Secondary outcomes were changes in Corvis ST (Oculus Optikgeräte GmbH) biomechanical parameters and vision, refraction, and corneal tomography measurements.

RESULTS

Mean 3-year changes in zonal Kmax-3mm were not significantly different between the accelerated and standard groups (-0.06 ± 0.75 and -0.35 ± 0.94 diopters [D], respectively, P = .727). Despite the contralateral design of the study, based on most baseline biomechanical indices, corneas in the standard group were weaker before treatment. The standard group also showed significantly fewer 3-year changes in the stress-strain index (-0.11 ± 0.21 vs -0.30 ± 0.32), integrated radius (+0.99 ± 3.48 vs +3.14 ± 2.84), and deformation amplitude ratio-2mm (-1.38 ± 1.33 vs +0.30 ± 1.75) (all P < .0167). Corneal stiffness in the accelerated group was stable for 2 years, and the decline mainly occurred during the third year.

CONCLUSIONS

In young patients with Down syndrome who had keratoconus, accelerated and standard CXL showed a similar flattening effect. Standard CXL is better able to maintain corneal stiffness in weaker corneas. With accelerated CXL, despite stable results for 2 years, there was decreased corneal stiffness in the third year. Longer follow-up periods are warranted to study the decreased efficacy on keratoconus progression. [J Refract Surg. 2022;38(6):381-388.].

Management of Keratoconus in Down Syndrome and Other Intellectual Disability

PURPOSE

The purpose of this study was to assess an intellectual disability (ID) cohort with keratoconus (KC) regarding ophthalmic (visual acuity and corneal tomography) and systemic characteristics and to describe an appropriate clinical algorithm for investigation and management of KC in this setting.

METHODS

This was the retrospective cohort study of patients with ID (Down syndrome, autism, and other) in the cornea department of a tertiary referral ophthalmic hospital in Dublin, Ireland. Retrospective chart review was conducted on people with ID undergoing examination under anesthesia or crosslinking under general anesthetic. Key outcome data included corneal examination findings, corneal tomography, visual acuity, and examination findings (eg, type of ID, general anesthetic, and cardiac status).

RESULTS

Mean age of the 24 patients was 31.9 years (66.7% male). ID type was Down syndrome (66.7%), autism (25%), and other (8.3%). KC was diagnosed in 98% of eyes, with 45.8% having untreatable advanced disease (57.1% of these bilateral), 39.6% amenable to corneal collagen crosslinking (35.7% of these bilateral), and 6.3% having corneal transplantation. Congenital heart defects were present in 37.5% of the Down syndrome group. There were no serious ocular or systemic adverse events.

CONCLUSIONS

KC is strikingly prevalent in the ID population. Ireland has the highest rate of Down syndrome in Europe (26.3:10,000 live births). This group is rarely suitable for corneal transplantation, and corneal collagen crosslinking is an effective intervention to prevent progression to advanced KC in this already socially restricted group. We propose an algorithm for investigation/treatment and also recommend uniform pediatric KC screening/treatment in ID populations.

Immediate sequential bilateral cataract surgery in adults with Down's syndrome

PURPOSE

To describe the cataract surgery outcomes in 34 adult patients with Down's syndrome in our center between 1996 and 2019.

SETTING

Clinical practice, tertiary hospital in Madrid, Spain.

DESIGN

Retrospective, descriptive study in which 34 patients with Down's syndrome who underwent cataract surgery in our center between 1996 and 2019 were included.

METHODS

Socio-demographic and clinical data such as the type of cataract, the keratometry and biometry, the type of surgery, the IOL material, and the complications before and after surgery were recovered.

RESULTS

Fifty-four eyes of 34 patients (23 female, 11 male, mean age 49 ± 8 years) underwent cataract surgery with general anesthesia. Immediately sequential, bilateral cataract surgery was performed in 18 patients (90% of bilateral cases). White cataract was found in 11 eyes (20.4%). Phacoemulsification technique was used in 51 eyes, extracapsular technique in 2 eyes (3.7%), and intracapsular technique in 1 eye (1.85%) (the only aphakic eye after surgery). The mean Km was 48.73 ± 4D, and the mean axial length was 25.2 ± 2.5 mm. The most frequent ocular comorbidity was myopia (27 eyes, 50%) followed by strabismus (11 eyes, 20.4%) and keratoconus (10 eyes, 18.5%). Posterior capsular rupture as a complication during surgery was found in 3 eyes (5.5%). The mean preoperative visual acuity was 0.8 ± 0.2 logMAR, and the mean postoperative visual acuity was 0.5 ± 0.18 logMAR.

CONCLUSIONS

Phacoemulsification technique can be performed in adults with Down's syndrome with an acceptable rate of complications. The lack of patient cooperation, the ocular comorbidities and the challenging biometric estimation must be considered in surgical planning. It seems reasonable to perform immediately sequential, bilateral cataract surgery when possible, in order to reduce the exposure to general anesthesia.

Detecting Keratoconus: Feasibility and Findings in Three Pediatric Risk Groups

PURPOSE

To investigate the utility of three corneal screening devices in three groups of children.

METHODS

This was a prospective study of patients with Trisomy 21 (group 1), patients with a first-degree relative with keratoconus (group 2), and control patients (group 3). Informed consent was obtained before testing with the Pentacam (Oculus Optikgeräte GmbH), Orbscan (Orbscan, Inc), and Ocular Response Analyzer (ORA) (Ametek Reichart Technologies). The ability to complete tests, the quality of results, and the corneal parameters obtained for each eye were recorded. A one-way analysis of variance test was used to compare the results between the three groups.

RESULTS

Fifty-four patients aged from 7 to 17 years (mean: 11.74 years) were enrolled between July 2014 and July 2016. The number of patients and the percentage of tests completed for groups 1, 2, and 3 were 12 (55%), 21 (87%), and 21 (88%), respectively. The Pentacam values by group were central corneal thickness of 524, 543, and 542 µm (P = .36); thinnest point of 498, 536, and 534 µm (P = .03); corneal front mean keratometry of 44.9, 43.2, and 43.2 (P = .01); and quality score of 1.42, 0.22, and 0.04 (P < .0001), respectively. Orbscan values by group were central corneal thickness of 493, 551, and 550 µm (P = .01) and thinnest point of 451, 536, and 538 µm (P < .0001), respectively. ORA values by group were corneal hysteresis of 10.6, 12.1, and 11.6 (P = .124); corneal resistance factor of 9.9, 11.8, and 11.6 (P = .03); and waveform score of 5.6, 7.6, and 7.3 (P < .0001), respectively.

CONCLUSIONS

Patients in group 1 completed fewer tests reliably and had thinner corneas and lower corneal resistance factors than patients in groups 2 and 3. Corneal tests used to evaluate adults for keratoconus may not be reliable for the evaluation of certain high-risk pediatric patients. [J Pediatr Ophthalmol Strabismus. 2022;59(2):94-101.].

Nutritional and Metabolic Imbalance in Keratoconus

Keratoconus (KC) is a progressive corneal degeneration characterized by structural changes consisting of progressive thinning and steepening of the cornea. These alterations result in biomechanical weakening and, clinically, in vision loss. While the etiology of KC has been the object of study for over a century, no single agent has been found. Recent reviews suggest that KC is a multifactorial disease that is associated with a wide variety of genetic and environmental factors. While KC is typically considered a disease of the cornea, associations with systemic conditions have been well described over the years. In particular, nutritional and metabolic imbalance, such as the redox status, hormones, metabolites, and micronutrients (vitamins and metal ions), can deeply influence KC initiation and progression. In this paper, we comprehensively review the different nutritional (vitamins and minerals) and metabolic (hormones and metabolites) factors that are altered in KC, discussing their possible implication in the pathophysiology of the disease.

Down syndrome: a review of ocular manifestations

Down syndrome is the most common genetically mediated intellectual disability. Although many physiologic and pathologic features of Down syndrome are discussed at length in the literature, the ocular manifestations of Down syndrome have seldom been discussed in a comprehensive fashion. Given that Down syndrome has ocular manifestations from the front to the back of the eye, it is important for physicians to become familiar with these manifestations, especially given the prevalence of Down syndrome. This review aims to discuss the varied ophthalmologic manifestations of Down syndrome – including strabismus, amblyopia, nystagmus, accommodation deficits, nasolacrimal duct obstruction, keratoconus, optic nerve pathology, neoplastic disease, and retinal pathology – to facilitate better care and visual outcomes in this important patient population.

The link between Keratoconus and posterior segment parameters: An updated, comprehensive review

Keratoconus (KCN) has been typically known as a disorder with effects limited to the cornea. Because of this viewpoint, less attention has been devoted to its effects on the posterior segment structures. We aimed to provide a comprehensive review of the literature to understand the potential link between KCN and posterior segment structures and their functions. It is clear from the extensive evidence in the literature that KCN can be associated with morphological and functional changes in different parts of the posterior segment. It is worth noting that anatomical changes have been not only noted in several layers of the retina but also in the optic nerve head and the choroid. Several mechanisms have been proposed to explain this observation, including incidents induced by oxidative stress in keratoconic corneas and retinal adaptions to the distorted image that lands on the retina. Consequently, when KCN has been diagnosed, it seems practical to consider assessing the retinal and choroidal profile using optical coherence tomography and potentially functional abnormalities through electrophysiology procedures.

Anterior pituitary, sex hormones, and keratoconus: Beyond traditional targets

"The Diseases of the Horny-coat of The Eye", known today as keratoconus, is a progressive, multifactorial, non-inflammatory ectatic corneal disorder that is characterized by steepening (bulging) and thinning of the cornea, irregular astigmatism, myopia, and scarring that can cause devastating vision loss. The significant socioeconomic impact of the disease is immeasurable, as patients with keratoconus can have difficulties securing certain jobs or even joining the military. Despite the introduction of corneal crosslinking and improvements in scleral contact lens designs, corneal transplants remain the main surgical intervention for treating keratoconus refractory to medical therapy and visual rehabilitation. To-date, the etiology and pathogenesis of keratoconus remains unclear. Research studies have increased exponentially over the years, highlighting the clinical significance and international interest in this disease. Hormonal imbalances have been linked to keratoconus, both clinically and experimentally, with both sexes affected. However, it is unclear how (molecular/cellular signaling) or when (age/disease stage(s)) those hormones affect the keratoconic cornea. Previous studies have categorized the human cornea as an extragonadal tissue, showing modulation of the gonadotropins, specifically luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Studies herein provide new data (both in vitro and in vivo) to further delineate the role of hormones/gonadotropins in the keratoconus pathobiology, and propose the existence of a new axis named the Hypothalamic-Pituitary-Adrenal-Corneal (HPAC) axis.

Potential underlying genetic associations between keratoconus and diabetes mellitus

Background Keratoconus (KC) is the most common ectatic corneal disease, characterized by significantly localized thinning of the corneal stroma. Genetic, environmental, hormonal, and metabolic factors contribute to the pathogenesis of KC. Additionally, multiple comorbidities, such as diabetes mellitus, may affect the risk of KC. Main Body Patients with diabetes mellitus (DM) have been reported to have lower risk of developing KC by way of increased endogenous collagen crosslinking in response to chronic hyperglycemia. However, this remains a debated topic as other studies have suggested either a positive association or no association between DM and KC. To gain further insight into the underlying genetic components of these two diseases, we reviewed candidate genes associated with KC and central corneal thickness in the literature. We then explored how these genes may be regulated similarly or differentially under hyperglycemic conditions and the role they play in the systemic complications associated with DM. Conclusion Our comprehensive review of potential genetic factors underlying KC and DM provides a direction for future studies to further determine the genetic etiology of KC and how it is influenced by systemic diseases such as diabetes.

Refractive and Vision Status in Down Syndrome: A Comparative Study

Objectives:

To determine the prevalence of refractive errors and visual impairment in Down syndrome (DS) patients compared to normal controls.

Materials and Methods:

Cycloplegic refraction was tested in 213 DS patients and 184 normal age- and gender-matched controls using autorefraction followed by retinoscopy. Data from the worse eye of each case were used in the analyses.

Results:

In the DS and control groups, respectively, mean age was 17.2±4.8 and 17.2±4.4 years (p=0.993) and 53.0% and 49.5% were male (p=0.473). In the DS and control groups, respectively, mean spherical equivalent (SE) was -5.13±4.47 and -4.15±3.04 diopters (D) in myopics (p=0.050) and 2.47±1.64 and 2.36±2.04 D in hyperopics (p=0.482), mean cylinder error was -2.17±1.39 and -2.05±1.57 D (p=0.451), mean J0 was -0.03±0.89 and 0.12±0.76 D (p=0.086), and mean J45 was 0.11±1.02 and -0.13±1.03 D (p=0.024). The prevalence of oblique astigmatism was higher in the DS group (20.4% vs. 6.1%) while against-the-rule astigmatism was more prevalent in the control group (84.0% vs. 71.6%) (p<0.001). The prevalence of anisometropia was not significantly different between the groups (19.4% vs. 13.8%). Visual impairment was detected in 11.7% of the DS and 0.5% of the control group (p<0.001). The prevalence of amblyopia was 36.3% and 3.8% in the DS and control groups, respectively (p<0.001). Based on the multiple model, only absolute SE inversely correlated with age and differed between males and females (all p<0.05).

Conclusion:

In DS patients, the prevalence rates of refractive errors, amblyopia, and visual impairment are higher than those in non-DS individuals, and emmetropization appears to be either defective or slow. Cylinder error is stable in this age range, but the rotation of astigmatism axis is different from normal samples.

Neuro-Ophthalmological Manifestations in Children with Down Syndrome: Current Perspectives

Down syndrome, caused by an extra copy of all or part of chromosome 21, is the most prevalent intellectual disability of genetic origin. Among numerous comorbidities which are part of the phenotype of individuals with Down syndrome, ocular problems appear to be highly prevalent. Neuro-ophthalmological manifestations, such as ocular alignment and motility disturbances, amblyopia, hypoaccommodation or optic nerve abnormalities, and other organic ocular anomalies frequently reported in Down syndrome, may lead to an overall decrease in visual acuity. Although numerous studies have reported ocular anomalies related to Down syndrome, it remains challenging to determine the impact of each anomaly upon the decreased visual acuity, as most such individuals have more than one ocular problem. Even in children with Down syndrome and no apparent ocular defect, visual acuity has been found to be reduced compared with typically developing children. Pediatric ophthalmological examination is a critical component of a multidisciplinary approach to prevent and treat ocular complications and improve the visual outcome in children with Down syndrome. This narrative review aims to provide a better understanding of the neuro-ophthalmological manifestations and discuss the current ophthalmological management in children with Down syndrome.

Challenges in Patients with Trisomy 21: A Review of Current Knowledge and Recommendations

Purpose

To summarize and review the common ophthalmic anomalies in children with trisomy 21 (Down syndrome) in order to propose an update to current clinical recommendations.

Methods

A retrospective chart review, systemic literature review, and international survey of the frequency of ocular abnormalities, screening schedules, and challenging aspects examining children with trisomy 21. The chart review included patients treated at the Department of Ophthalmology at the University Hospital of Zurich over a two-year period. The international survey was submitted to the members of the Swiss Society of Ophthalmology, Slovenian Ophthalmological Society, and European Pediatric Ophthalmology Society.

Results

Analysis of 52 patient records during the study period revealed refractive errors (astigmatism: 54% of patients, hyperopia: 26%, and myopia: 15%) as the most common diagnosis, whereas childhood cataract was reported in 5%. This is in concordance with the extended literature review of 249 publications, although congenital cataracts were reported to be higher than at our institution. The survey participants reported great challenges in taking care of these patients, despite their long professional experience (73% with over 10 years of experience).

Conclusion

Care and treatment of children with trisomy 21 continues to be demanding for paediatric ophthalmologists. We recommend the following examination schedule for these patients: first, ophthalmological examination at 6-12 months of age, then once in 3-6 months for children under 2 years of age, once in 6 months for children 2-5 years of age, annually for children 5-10 years of age, and thereafter, to be decided on an individual basis depending on the presenting ocular abnormalities of the patient.

Prevalence of keratoconus in persons with Down syndrome: a review

Purpose

Keratoconus is a vision-threatening condition, and there is a need for knowledge about the occurrence in subgroups of the population. The progression of the disease can be effectively stopped, and vision may be restored, if keratoconus is diagnosed at an early stage. The purpose of this review was to evaluate the literature of the prevalence of keratoconus in persons with Down syndrome.

Methods

We conducted a literature review of keratoconus prevalence in persons with Down syndrome. A thorough search was performed in Pubmed (Medline), and the quality of evidence was evaluated.

Results

The literature review identified 20 relevant studies, which reported keratoconus in 0%–71% of persons with Down syndrome. These studies varied greatly in design, patient selection, sample sizes and mean age, and the quality of evidence concerning estimates for the prevalence of keratoconus was generally evaluated as low. Most studies that included adults reported high prevalences of keratoconus–in many studies more than 10-fold the prevalence in the general population. No large screening studies in persons with Down syndrome were identified.

Conclusions

The present review showed that the prevalence of keratoconus in persons with Down syndrome is higher than in the general population. However, estimates from previous studies vary widely. Screening for keratoconus in this group should be considered.

Opportunities, barriers, and recommendations in down syndrome research

BACKGROUND

Recent advances in medical care have increased life expectancy and improved the quality of life for people with Down syndrome (DS). These advances are the result of both pre-clinical and clinical research but much about DS is still poorly understood. In 2020, the NIH announced their plan to update their DS research plan and requested input from the scientific and advocacy community.

OBJECTIVE

The National Down Syndrome Society (NDSS) and the LuMind IDSC Foundation worked together with scientific and medical experts to develop recommendations for the NIH research plan.

METHODS

NDSS and LuMind IDSC assembled over 50 experts across multiple disciplines and organized them in eleven working groups focused on specific issues for people with DS.

RESULTS

This review article summarizes the research gaps and recommendations that have the potential to improve the health and quality of life for people with DS within the next decade.

CONCLUSIONS

This review highlights many of the scientific gaps that exist in DS research. Based on these gaps, a multidisciplinary group of DS experts has made recommendations to advance DS research. This paper may also aid policymakers and the DS community to build a comprehensive national DS research strategy.

Transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus

BACKGROUND

Keratoconus is the most common corneal dystrophy. It can cause loss of uncorrected and best-corrected visual acuity through ectasia (thinning) of the central or paracentral cornea, irregular corneal scarring, or corneal perforation. Disease onset usually occurs in the second to fourth decade of life, periods of peak educational attainment or career development. The condition is lifelong and sight-threatening. Corneal collagen crosslinking (CXL) using ultraviolet A (UVA) light applied to the cornea is the only treatment that has been shown to slow progression of disease. The original, more widely known technique involves application of UVA light to de-epithelialized cornea, to which a photosensitizer (riboflavin) is added topically throughout the irradiation process. Transepithelial CXL is a recently advocated alternative to the standard CXL procedure, in that the epithelium is kept intact during CXL. Retention of the epithelium offers the putative advantages of faster healing, less patient discomfort, faster visual rehabilitation, and less risk of corneal haze.

OBJECTIVES

To assess the short- and long-term effectiveness and safety of transepithelial CXL compared with epithelium-off CXL for progressive keratoconus.

SEARCH METHODS

To identify potentially eligible studies, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2020, Issue 1); Ovid MEDLINE; Embase.com; PubMed; Latin American and Caribbean Health Sciences Literature database (LILACS); ClinicalTrials.gov; and World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We did not impose any date or language restrictions. We last searched the electronic databases on 15 January 2020.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in which transepithelial CXL had been compared with epithelium-off CXL in participants with progressive keratoconus.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology.

MAIN RESULTS

We included 13 studies with 723 eyes of 578 participants enrolled; 13 to 119 participants were enrolled per study. Seven studies were conducted in Europe, three in the Middle East, and one each in India, Russia, and Turkey. Seven studies were parallel-group RCTs, one study was an RCT with a paired-eyes design, and five studies were RCTs in which both eyes of some or all participants were assigned to the same intervention. Eleven studies compared transepithelial CXL with epithelium-off CXL in participants with progressive keratoconus. There was no evidence of an important difference between intervention groups in maximum keratometry (denoted 'maximum K' or 'Kmax'; also known as steepest keratometry measurement) at 12 months or later (mean difference (MD) 0.99 diopters (D), 95% CI -0.11 to 2.09; 5 studies; 177 eyes; I² = 41%; very low certainty evidence). Few studies described other outcomes of interest. The evidence is very uncertain that epithelium-off CXL may have a small (data from two studies were not pooled due to considerable heterogeneity (I² = 92%)) or no effect on stabilization of progressive keratoconus compared with transepithelial CXL; comparison of the estimated proportions of eyes with decreases or increases of 2 or more diopters in maximum K at 12 months from one study with 61 eyes was RR 0.32 (95% CI 0.09 to 1.12) and RR (non-event) 0.86 (95% CI 0.74 to 1.00), respectively (very low certainty). We did not estimate an overall effect on corrected-distance visual acuity (CDVA) because substantial heterogeneity was detected (I² = 70%). No study evaluated CDVA gain or loss of 10 or more letters on a logarithm of the minimum angle of resolution (logMAR) chart. Transepithelial CXL may result in little to no difference in CDVA at 12 months or beyond. Four studies reported that either no adverse events or no serious adverse events had been observed. Another study noted no change in endothelial cell count after either procedure. Moderate certainty evidence from 4 studies (221 eyes) found that epithelium-off CXL resulted in a slight increase in corneal haze or scarring when compared to transepithelial CXL (RR (non-event) 1.07, 95% CI 1.01 to 1.14). Three studies, one of which had three arms, compared outcomes among participants assigned to transepithelial CXL using iontophoresis versus those assigned to epithelium-off CXL. No conclusive evidence was found for either keratometry or visual acuity outcomes at 12 months or later after surgery. Low certainty evidence suggests that transepithelial CXL using iontophoresis results in no difference in logMAR CDVA (MD 0.00 letter, 95% CI -0.04 to 0.04; 2 studies; 51 eyes). Only one study examined gain or loss of 10 or more logMAR letters. In terms of adverse events, one case of subepithelial infiltrate was reported after transepithelial CXL with iontophoresis, whereas two cases of faint corneal scars and four cases of permanent haze were observed after epithelium-off CXL. Vogt's striae were found in one eye after each intervention. The certainty of the evidence was low or very low for the outcomes in this comparison due to imprecision of estimates for all outcomes and risk of bias in the studies from which data have been reported.

AUTHORS' CONCLUSIONS

Because of lack of precision, frequent indeterminate risk of bias due to inadequate reporting, and inconsistency in outcomes measured and reported among studies in this systematic review, it remains unknown whether transepithelial CXL, or any other approach, may confer an advantage over epithelium-off CXL for patients with progressive keratoconus with respect to further progression of keratoconus, visual acuity outcomes, and patient-reported outcomes (PROs). Arrest of the progression of keratoconus should be the primary outcome of interest in future trials of CXL, particularly when comparing the effectiveness of different approaches to CXL. Furthermore, methods of assessing and defining progressive keratoconus should be standardized. Trials with longer follow-up are required in order to assure that outcomes are measured after corneal wound-healing and stabilization of keratoconus. In addition, perioperative, intraoperative, and postoperative care should be standardized to permit meaningful comparisons of CXL methods. Methods to increase penetration of riboflavin through intact epithelium as well as delivery of increased dose of UVA may be needed to improve outcomes. PROs should be measured and reported. The visual significance of adverse outcomes, such as corneal haze, should be assessed and correlated with other outcomes, including PROs.

Prevalence of Keratoconus in Persons With Down Syndrome in a National Registry in Norway

This cross-sectional study evaluates the association of keratoconus with Down syndrome by estimation of the prevalence of keratoconus in persons with Down syndrome in Norway.

Three-Dimensional Morphogeometric and Volumetric Characterization of Cornea in Pediatric Patients With Early Keratoconus

PURPOSE

To present morphogeometric and volumetric characteristics of the cornea and its diagnostic value in pediatric patients with keratoconus (KC) using 3-dimensional (3-D) corneal modeling.

DESIGN

Cross-sectional study.

METHODS

This single-center (VISSUM Innovation, Alicante, Spain) study comprised 49 eyes of 49 pediatric patients (age ≤16 years) with KC and 31 eyes of 31 healthy pediatric controls. Eyes were graded as early (n = 21) and mild KC (n = 28) based on the RETICS (Thematic Network for Co-Operative Research in Health) classification system. The 3-D corneal model was generated using raw topographic data. Deviation of anterior (D_apexant) and posterior (D_apexpost) apex and minimum thickness points (D_mctant, D_mctpost), D_apexant-D_apexpost difference, total corneal volume (V_total), volumetric distribution (VOL_AAP, VOL_PAP, and VOL_MCT), and percentage of relative volume increase (VOL_AAPrel, VOL_PAPrel, and VOL_MCTrel) between 2 consecutive radii centered to anterior/posterior apex and thinnest point were evaluated.

RESULTS

D_apexpost and D_apexant-D_apexpost difference were higher in the early and mild KC groups compared to the control group (P < .05). Eyes with early and mild KC had decreased V_total compared with the control group (P < .05). D_apexpost, D_apexant-D_apexpost difference, and VOL_MCTrel between 1.0 and 1.4 mm diameters had area under receiver operating characteristics curve (AUROC) values over 0.93 in discrimination of early KC from normal.

CONCLUSIONS

This is the first study presenting morphogeometric and volumetric characterization of cornea in pediatric patients with early and mild KC using a 3-D corneal model. Integration of the morphogeometric and volumetric parameters to topography software can add value in early detection of KC in pediatric patients.

Evidence of a Down Syndrome Keratopathy: A Three-Dimensional (3-D) Morphogeometric and Volumetric Analysis

The aim of this study was to investigate whether a different and abnormal corneal profile is present in Down syndrome (DS) by personalized three-dimensional (3D) modelling. This single-centre cross-sectional study included 43 patients with DS (43 eyes) and 58 age-sex-matched control subjects (58 eyes) with normal karyotype and topography. Refraction, central corneal thickness (CCT), aberrations (high-order, coma and spherical), asphericity and morphogeometric/volumetric parameters based on a 3D corneal model that was generated from raw topographical data were evaluated. Deviation of anterior/posterior apex (D_apexant/D_apexpost) and thinnest point (D_mctant/D_mctpost) from corneal vertex, anterior/posterior surface area (A_ant/A_post), sagittal area passing through the anterior/posterior apex (A_apexant/A_apexpost) and thinnest point (A_mctpost), total corneal volume (V_total) and volumetric progression for each 0.05 mm step of the radius value centred to the thinnest point (VOL_MCT) and anterior/posterior apex (VOL_AAP/VOL_PAP) comprised the morphogeometric/volumetric parameters. In the DS group, 58.1% of the eyes presented abnormal topography. High-order and coma aberrations, asphericity, D_apexant, A_ant, A_post and A_apexant were significantly higher, whereas CCT, A_apexpost, A_mctpost, V_total, VOL_AAP, VOL_PAP and VOL_MCT were lower in the DS group than in the control group (p < 0.05). D_apexpost did not differ between the groups (p > 0.05). This study demonstrates that corneas of the subjects with DS are different and more aberrated than those of normal age- and sex-matched non-DS controls. Anterior corneal apex appears to be displaced in DS even with normal topography, while posterior apex seems stable although topography is abnormal. These findings may help to modify our approach in the diagnosis of keratopathy in subjects with DS.

Tomography-based definition of keratoconus for Down syndrome patients

Background

To assess the diagnostic ability of Pentacam HR (Oculus Optikgeräte, GmbH, Wetzlar, Germany) tomographic indices in discriminating keratoconus (KC) and KC suspect (KCS) in 10- to 30-year-old patients with Down syndrome (DS).

Methods

In this study, DS patients were enrolled through special needs schools, the National Down Syndrome Society, and relevant non-profit organizations. Diagnoses were made independently by two experienced specialists. Forty Pentacam indices related to corneal thickness, volume, density, keratometry, power, shape, aberration, and elevation were extracted. For each index, the accuracy for KC and KCS diagnosis was evaluated using discriminant analysis and the area under receiver operating characteristic curve (AUROC). From each enrolled case, data from only one eye was entered in the analyses.

Results

Analyses were performed on data from 25 KC, 46 KCS, and 154 non-ectatic DS eyes. The best discriminants for KC were anterior higher order aberrations (HOA) (cutoff > 0.643, AUROC = 0.879), posterior vertical coma (cutoff > 0.0702 μm, AUROC = 0.875), anterior vertical coma (cutoff > 0.4124 μm, AUROC = 0.868), and total HOA (cutoff > 0.608, AUROC = 0.867). The difference between AUROCs were not statistically significant (all P > 0.05). For KCS, the best discriminants were minimum corneal thickness (cutoff ≤ 480.0 μm, AUROC = 0.775), corneal volume (cutoff ≤ 55.3 μm, AUROC = 0.727) and Belin Ambrosio display-total deviation (BAD-D) (cutoff > 2.23, AUROC = 0.718) with no significant difference between AUROCs (all P > 0.05).

Conclusions

In this sample of DS patients, best KC discriminators were HOA and coma which showed good diagnostic ability. For KCS, best predictors were minimum corneal thickness, corneal volume, and BAD-D with relatively good diagnostic ability. Defining a new set of KC diagnostic criteria for DS patients is suggested.

Ophthalmological abnormalities in Down syndrome among Brazilian patients

Down syndrome is the most common chromosomal disorder, affecting 1/700 live births. Among the clinical findings, one constant concern is the high prevalence of visual disorders that, if left untreated, can negatively affect child development. The aim of this study was to determine the prevalence of ophthalmological findings among patients who attended an outpatient clinic for patients with Down syndrome in southern Brazil between 2005 and 2016. A cross-sectional study including 1,207 patients medical records were done, which 492 (40.8%) had some ophthalmological disorder. These data were subjected to descriptive analysis using Statistica software. Among the 492 patients with any ophthalmological disease, the need for glasses was found in 434 (36%) patients, keratoconus in 254 (42.1%), congenital cataract in 27 (15.1%), nasolacrimal duct obstruction in 25 (2.0%), strabismus in 22 (1.9%), nystagmus in four (0.3%), and juvenile cataract in two (0.2%). Two young adults with keratoconus underwent corneal transplantation. Although the prevalence of an ophthalmological disease among the present sample (40.8%) was lower than described in the current literature, it still reinforced the importance of routine and early evaluations in infants. These should begin at 6 months of age and be repeated half-year until 2 years old, annually until 7 years old, biennial in adolescents, and triennial in adults and elderly. Our findings of a high frequency of keratoconus support a detailed corneal study in such patients for early detection and treatment.

Corneal Abnormalities Are Novel Clinical Feature in Wolfram Syndrome

PURPOSE

To evaluate corneal morphology among patients with Wolfram syndrome (WFS).

DESIGN

Comparative observational longitudinal case series of WFS patients with a laboratory approach in the WFS1 gene knockout (Wfs1KO) mouse model.

METHODS

A group of 12 patients with biallelic mutations in the WFS1 gene recruited from the whole country and a control group composed of 30 individuals with type 1 diabetes (T1D) were evaluated in a national reference center for monogenic diabetes. All subjects (n = 42) underwent a complete ophthalmic examination, computer videokeratography, and corneal thickness and endothelial measurements. Additionally, WFS patients (n = 9) underwent longitudinal videokeratography and Pentacam evaluation. Corneal characteristics were assessed and compared between both groups. Human and mouse corneas were subjected to immunohistochemistry to detect wolframin expression and microscopic evaluation to study corneal morphology ex vivo.

RESULTS

Clinical and topographic abnormalities similar to keratoconus were observed in 14 eyes (58.3%) of 8 WFS patients (66.7%). Flat keratometry, inferior-superior dioptric asymmetry, skewed radial axis, logarithm of keratoconus percentage index, index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, index of height asymmetry, and index of height decentration differed between WFS and T1D patients. Immunohistochemistry demonstrated wolframin expression in human and mouse corneas. Compared with Wfs1WT mice, Wfs1KO mice also presented corneal abnormalities.

CONCLUSIONS

Patients with WFS present a high prevalence of changes in corneal morphology compatible with the diagnosis of early stages of keratoconus. Observations in a mouse model suggest that a mutation in the WFS1 gene may be responsible for corneal abnormalities similar to keratoconus.

Assessment of the mechanical forces applied during eye rubbing

Background

To determine the average amount of mechanical forces applied to the lids of keratoconus patients during eye rubbing.

Methods

Fifty-seven patients (41 male, 16 female, average age 34.8 years) with a clinically and topographically diagnosed keratoconus and a history of eye rubbing were prospectively asked to perform their individual eye rubbing movement on a high-precision balance. The type of eye-rubbing movement and the force applied, represented in newtons (N), were recorded and analyzed.

Results

We detected three different types of eye rubbing. Rubbing with the fingertip was most frequent (51%), followed by rubbing with the knuckle (44%) and rubbing with the fingernail (6%). Each type of eye rubbing showed different average forces, with knuckle type eye rubbing applying significantly more force (9.6 ± 6.3 N) on the lids than fingertip (4.3 ± 3.1 N) and fingernail (2.6 ± 3.3 N) types (p < 0,001 and p = 0,016, respectively).

Conclusions

There were major variations in the force exerted on the lids, depending on the type of eye rubbing employed. This data will help determine the forces that need to be applied in future experimental eye rubbing models.

Effect of Down syndrome and keratoconus on corneal density and volume: a triple comparative study

Keratoconus (KCN) and Down syndrome affect the corneal density and volume. In this study included Down syndrome patients with and without KCN (24 Down-KCN and 204 Down-nonKCN eyes) and normal age- and gender-matched individuals (184 eyes). Studied parameters were the corneal density measured with Pentacam HR in 5 concentric zones and annuli (0-2 mm, 2-6 mm, 6-10 mm, 10-12 mm, and 0-12 mm) in 4 different depth layers (anterior 120 µm, posterior 60 µm, middle layer, and the full thickness of the cornea), and the 10 mm zone corneal volume. In Down-KCN, Down-nonKCN, and control groups, respectively, mean full thickness density in the 0-12 mm zone was 19.35 ± 2.92, 17.85 ± 2.55, and 15.78 ± 2.67 GSU, and mean corneal volume was 57.45 ± 4.37, 56.99 ± 3.46, and 61.43 ± 3.42mm3. All density readings were significantly different between the three studied groups (all P < 0.01) except full thickness density in 0-2 mm and 2-6 mm (P > 0.05) and corneal volume (P = 0.519) between Down-KCN and Down-nonKCN groups; these inter-group densitometry differences within the 6 mm zone were only in the middle layer, and not the anterior or posterior thickness layers (all P > 0.05). Corneal density increased with age and corneal thickness, but there was no significant relationship with gender. Overall, Down syndrome is associated with increased density and light scatter in all corneal layers up to the 12 mm diameter. In Down patients with KCN, the increased light scatter and density in the 6 mm zone is only in the middle thickness layer. Corneal volume is reduced in Down syndrome irrespective of the presence or absence of KCN.

Keratoconus and corneal morphology in patients with Down syndrome at a pediatric hospital

PURPOSE

To evaluate patients with Down syndrome for keratoconus and corneal abnormalities using Scheimpflug imaging (Pentacam HR) in a pediatric setting.

METHODS

The Pentacam scans of patients with Down syndrome seen at Children's Hospital Colorado Ophthalmology Department were reviewed retrospectively, and the following data were collected: keratometry values, pachymetry values, components of the Belin ABCD Grading System, the Belin/Ambrosio enhanced ectasia display D value, and topometric indices, including ISV, IVA, and KI. Subjective interpretation was used to classify scans as normal, abnormal, keratoconus suspect, and definite keratoconus.

RESULTS

A total of 56 eyes of 31 patients aged 4-24 years (mean, 12.4) were included. The average value for K1 was 44.95 ± 1.73 D (range, 40.90-49.3 D); for K2, 46.87 ± 2.16 D (range, 42.50-51.80 D); for Kmax, 48.20 ± 3.11 D (range, 43-61.7 D); and for Kmean, 45.81 ± 1.85 D (range, 41.7-50.35 D). Mean pachymetry at the thinnest point was 509 ± 44.24 μm (range, 410-612 μm) and at the apex was 519 ± 44.24 μm (range, 412-646 μm). The mean D value was 2.08 ± 1.57 (range, 0.08-9.71). There were 10 patients (32%) with either keratoconus suspect or definite keratoconus in at least one eye.

CONCLUSIONS

We found a high frequency of keratoconus and keratoconus suspect in pediatric and young adult patients with Down syndrome. The corneas in this population had steeper K values and thinner pachymetry values compared to previously reported controls.

Genetic and Environmental Risk Factors for Keratoconus

Keratoconus, a progressive corneal ectasia, is a complex disease with both genetic and environmental risk factors. The exact etiology is not known and is likely variable between individuals. Conditions such as hay fever and allergy are associated with increased risk, while diabetes may be protective. Behaviors such as eye rubbing are also implicated, but direct causality has not been proven. Genetics plays a major role in risk for some individuals, with many large pedigrees showing autosomal inheritance patterns. Several genes have been implicated using linkage and follow-up sequencing in these families. Genome-wide association studies for keratoconus and for quantitative traits such as central corneal thickness have identified several genetic loci that contribute to a cumulative risk for keratoconus, even in people without a family history of the disease. Identification of risk genes for keratoconus is improving our understanding of the biology of this complex disease.

Treatment of Severe Keratoconus Hydrops With Intracameral Platelet-Rich Plasma Injection

PURPOSE

To present successful management of severe corneal hydrops by corneal optical coherence tomography (OCT) guidance and intracameral application of eye platelet-rich plasma (E-PRP) in a case with Down syndrome.

METHODS

A 36-year-old woman with Down syndrome presented with acute vision loss, pain, photophobia, and corneal edema in the left eye. Clinical examination revealed keratoconus in the right eye and extreme keratoconus with severe corneal hydrops in the left eye. Anterior segment OCT (MS-39, Costruzione Strumenti Oftalmici, Firenze, Italy) showed intrastromal cystic fluid collection and ruptured and detached Descemet membrane. The OCT-guided management of hydrops is first described in this case report.

RESULTS

Medical treatment and intracameral sulfur hexafluoride injection failed. A sterile 0.3 mL of E-PRP was injected into the anterior chamber. Clinical and anatomical improvement began from the first postoperative day, and corneal edema totally resolved at 1 week. Postoperatively, no significant side effect was noted except an early transient moderate (28 mm Hg) intraocular pressure peak. Anterior segment-OCT demonstrated dramatic normalization in corneal morphology with total disappearance of fluid in the cystic intracorneal space, closure of the DM rupture, and DM reattachment. The patient was stable during the 6-month follow-up.

CONCLUSIONS

In this case, intraocular E-PRP was a promising, apparently safe, and effective treatment option in management of corneal hydrops, in which conventional approaches failed. This is the first case in the literature to describe OCT appearance of corneal hydrops and intracameral use of E-PRP for the resolution of DM rupture in acute corneal hydrops.

The keratoconus enigma: A review with emphasis on pathogenesis

PURPOSE

To review the literature on the etiopathogenesis of keratoconus (KC).

METHODS

A literature search was conducted using PUBMED and Google Scholar for keratoconus. The authors analyzed epidemiology studies, reviews, and case reports.

RESULTS

Atopy and ocular surface inflammation are a common features of KC and should lead to a reconsideration of the traditional definition of KC as a "non inflammatory" condition. Co-morbidities suggest that KC may be the ocular manifestation of a systemic disease. Finally, KC shows higher prevalence in certain ethnicities, which calls into question the status of KC as a rare disease, at least in these communities.

CONCLUSION

We believe that future studies should test whether selected, high prevalence populations exhibit specific genetic background and/or ethno-specific environmental risk factors.

Application of Topographical Keratoconus Detection Metrics to Eyes of Individuals with Down Syndrome

SIGNIFICANCE

The challenges associated with clinical assessment of individuals with Down syndrome contribute to a wide range of estimates on the prevalence of keratoconus in the Down syndrome population. This work focuses on two topographical indices previously identified with keratoconus detection, applying them to a topographical data set meeting strict sampling criteria.

PURPOSE

The purpose of this study was to quantify the level of keratoconus-like topographical morphology in a large sample of eyes from individuals with Down syndrome, as identified by two keratoconus detection metrics: inferior-superior dioptric asymmetry (I-S) and KISA%. Severity of the asymmetry was also cast within the context of established Collaborative Longitudinal Evaluation of Keratoconus study disease severity classification criteria.

METHODS

Corneal topography data on both eyes of 140 subjects with Down syndrome and 138 control subjects were collected. Both I-S and KISA% were calculated from the topography data of eyes with sufficient sampling. Steep and flat keratometry data are reported for subjects with measurements on both eyes in the context of values recorded by the Collaborative Longitudinal Evaluation of Keratoconus study in frank keratoconus to examine within-eye and between-eye asymmetry and severity.

RESULTS

Keratoconus detection thresholds were exceeded in 20.8% of the eyes of subjects with Down syndrome and 2.2% of the eyes of controls using I-S and 11.8% of the eyes of subjects with Down syndrome and 0.0% of the eyes of controls using KISA%. Examination of the level of intraeye difference between flat and steep keratometry data for individuals with Down syndrome detected as having corneal morphology consistent with moderate keratoconus yields an average of 1.81 D of toricity, whereas the Collaborative Longitudinal Evaluation of Keratoconus study reported 3.28 D of toricity.

CONCLUSIONS

Morphology consistent with keratoconus as codified in the detection metrics I-S and KISA% is present in a large percentage of the eyes of individuals with Down syndrome. Differences were observed in the distribution of severity of corneal morphology in individuals with Down syndrome and the keratoconus population at large.

Keratoconus detection by novel indices in patients with Down syndrome: a cohort population-based study

PURPOSE

To use novel indices to determine the prevalence of KC and its progression in patients aged 10-30 years with Down syndrome.

STUDY DESIGN

Cohort population-based study.

METHODS

Two hundred twenty-six of 250 invited Down syndrome patients were enrolled. The diagnostic criteria were confirmed by two independent expert examiners using slit-lamp examinations and topographic indices measured by Pentacam HR (Oculus Optikgeräte): maximum keratometry centered on the steepest point (zonal Kmax-3 mm), Ambrósio's relational thickness (ART), inferior-superior asymmetry (IS-value), Belin/Ambrósio deviation value (BAD-D), the Tomographic and Biomechanical Index (TBI), and a posterior elevation map. In the KC cases, Corvis ST (Oculus Optikgeräte) was done. All the KC cases completed the second phase in 2017.

RESULTS

KC was identified in 28 patients (12.39%; 95% confidence interval: 8.2-17.9%): 20 bilateral and eight unilateral cases. Of these, 24 were in the ≤ 20-years age group, and four, in the > 20-years age group. The frequency of KC was not significantly correlated with age (P = 0.804) or gender (P = 0.322). In the KC cases, the mean zonal Kmax-3 mm, ART-max, IS-value, BAD-D, CBI, and TBI were 50.40 ± 5.88 D, 321.63 ± 111.94 μm, 1.99 ± 2.51, 3.73 ± 3.12, 0.54 ± 0.61, and 0.86 ± 0.20, respectively, and the minimum corneal thickness was 492.17 ± 42.67 μm. Of the 28 patients, 39.6% showed progression, and all were in the ≤ 20-years age group.

CONCLUSION

The prevalence of KC in Down syndrome patients is significantly higher than that reported in non-Down syndrome individuals of the same age groups. The progression rate is approximately similar to that of the non-Down syndrome population. Screening programs should be applied to prohibit serious visual impairment in these populations.

Corneal Collagen Cross-Linking Under General Anesthesia for Pediatric Patients With Keratoconus and Developmental Delay

PURPOSE

To report the clinical characteristics and outcomes of pediatric patients with keratoconus (KCN) who underwent corneal collagen cross-linking (CXL) under general anesthesia for developmental delay or inability to cooperate with topical anesthesia.

METHODS

In this retrospective case series, we reviewed the medical charts of pediatric patients with KCN who had CXL under general anesthesia from January 2018 to April 2019. Baseline disease characteristics of patients with and without developmental delay were compared using the Pearson χ test and the t test. Main outcomes were anesthesia or surgical complications and postoperative best corrected visual acuity (BCVA), keratometry (K) values, and caregiver report of eye-rubbing behavior.

RESULTS

Fourteen eyes of 9 patients were reviewed. All were habitual eye rubbers at baseline. Six (66.7%) were developmentally delayed. Compared with patients without developmental delay, developmentally delayed patients were diagnosed and treated at older ages (16.0 vs. 13.9 years), experienced longer delays from diagnosis to surgery (20.7 vs. 8.8 weeks), and had lower BCVA (20/70 vs. 20/40), higher steep K values (54.0 vs. 50.9), and a higher incidence of corneal scarring (75.0% vs. 33.3%) and monocular vision loss (50.0% vs. 0.0%) at baseline, although these differences were not statistically significant. No anesthesia or surgical complications occurred. BCVA and K values were stable at postoperative month 6, with no clinically or statistically significant change observed for either measure. Eight patients decreased or stopped eye rubbing.

CONCLUSIONS

We demonstrate the efficacy and safety of CXL under general anesthesia in halting the progression of KCN for pediatric patients with developmental delay or an inability to cooperate with the procedure until topical anesthesia.

Total corneal refractive power and shape in Down syndrome

PURPOSE

To determine the total corneal refractive power in 1-8 mm corneal zones and the 8 mm Q-value in non-keratoconic patients with Down syndrome and normal subjects aged 10-30 years.

METHODS

Right eye data from 203 Down syndrome patients (mean ± standard deviation age: 17.0 ± 4.7 years) and 189 age- and gender-matched normal subjects (17.1 ± 4.5 years) were compared. Main extracted Pentacam indices were total corneal refractive power in steep and flat axes, and mean and difference (corneal astigmatism) total corneal refractive power in 1-8 mm zones.

RESULTS

Mean total corneal refractive power in 1-8 mm zones was 45.17-45.74 D and 42.91-43.52 D in Down and normal group, respectively (all p < 0.001). The coefficients of variation of total corneal refractive power from the center to the periphery were similar in the two groups (p = 0.855). None of the mean total corneal refractive powers significantly correlated with age, and all of them were significantly higher in females (p < 0.001). Mean total corneal refractive power-based corneal astigmatism in these zones changed from 1.46 to 1.66 D in Down syndrome patients and 1.64 to 1.99 D in normal group. All corneal astigmatism indices were similar between two groups (all p > 0.05). The prevalence of against the rule and oblique astigmatism in all zones were higher in the Down syndrome group (all p < 0.05).

CONCLUSION

Adolescent and young non-keratoconic patients with Down syndrome have a more prolate cornea and a homogeneous keratometry distribution. In this population, females have a steeper cornea.

In vivo evaluation of corneal biomechanical properties by optical coherence elastography at different cross-linking irradiances

Corneal collagen cross-linking (CXL) strengthens the biomechanical properties of damaged corneas. Quantifying the changes of stiffness due to different CXL protocols is difficult, especially in vivo. A noninvasive elastic wave-based optical coherence elastography system was developed to construct in vivo corneal elasticity maps by excitation of air puff. Biomechanical differences were compared for rabbit corneas given three different CXL protocols while keeping the total energy delivered constant. The Young’s modulus was weaker in corneas treated with higher irradiance levels over shorter durations, and a slight increase of Young’s modulus was present in all groups one week after the recovery process. Due to the noninvasive nature and minimal force to generate corneal elastic waves, this technique has the potential for early detection and treatment of corneal diseases in clinic.