[Central corneal thickness in a healthy Spanish population]

Central Corneal Thickness of a Saudi Population in Relation to Age, Gender, Refractive Errors, and Corneal Curvature

Background In this study, we aimed to investigate the relationship between central corneal thickness (CCT) and age, gender, refractive errors, and corneal curvature in a Saudi population. Methodology In this randomized, hospital-based, retrospective study, data were collected from Dr. Sulaiman Al Habib Hospital and Imam Medical Center, Riyadh. A total of 1,005 eyes were included and recruited from patients referred to the refractive surgery clinic for Lasik assessment. The study included patients aged between 17 and 57 years with no history of any ocular pathology, eye surgeries, and systemic disease, as well as all groups with stable refractions. The identifying data were the age and gender of the patients, as well as their CCT, refraction, and corneal curvature. CCT and corneal curvature were measured by ultrasound pachymeter Pentacam. Results The distribution of CCT was 543.81 ± 34.47 μm. A significant difference in the mean CCT was observed across different refractive errors (p = 0.004). Patients with astigmatism had the lowest CCT, followed by myopic and hyperopic patients. An association between the spherical equivalent of patients with myopia and CCT (p = 0.001) was noted. Conclusions In the Saudi population, we found no significant association between mean corneal curvature and CCT in all three groups. Spherical equivalent in myopic patients was significantly associated with CCT. A significant difference in the mean CCT was observed across different refractive errors. There was a significant negative and weak correlation between age in myopic and astigmatism patients and CCT. Gender was significantly associated with CCT in patients with astigmatism.

Do Gender, Age, Body Mass and Height Influence Eye Biometrical Properties in Young Adults? A Pilot Study

BACKGROUND

Do gender, age, body mass and height influence eye biometrical properties in young adults?

METHODS

A total of 155 eyes (92 female, 63 male) of healthy subjects between the ages of 18 and 39 years were included in the study. The subjects' gender and age were recorded, and their body mass, height and biometrical properties of the eyes were measured.

RESULTS

The male subjects had significantly thicker and flatter corneas and lower minimal rim-to-disk ratios than the female subjects did. In both genders, age showed strong, negative correlations with anterior chamber depth and pupil diameter and a positive correlation with lens thickness. We also found significant, negative correlations between body height and mass with keratometry measurements, negative correlations between body height and optic disk rim area and rim volume, and positive correlations between body mass and axial length in both genders.

CONCLUSIONS

Biometric eye parameters differ among people. In addition to age and gender, which are usually taken into consideration when interpreting ocular biometry findings, we strongly suggest that body height and mass should be also routinely considered when interpreting eye biometry data, as these factors have an impact on ocular biometry.

Corneal Biomechanical Parameters and Central Corneal Thickness in Glaucoma Patients, Glaucoma Suspects, and a Healthy Population

PURPOSE

To evaluate and compare corneal hysteresis (CH), corneal resistance factor (CRF), and central corneal thickness (CCT), measurements were taken between a healthy population (controls), patients diagnosed with glaucoma (DG), and glaucoma suspect patients due to ocular hypertension (OHT), family history of glaucoma (FHG), or glaucoma-like optic discs (GLD). Additionally, Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated IOP (IOPcc) were compared between the different groups of patients.

METHODS

In this prospective analytical-observational study, a total of 1065 patients (one eye of each) were recruited to undergo Ocular Response Analyzer (ORA) testing, ultrasound pachymetry, and clinical examination. Corneal biomechanical parameters (CH, CRF), CCT, IOPg, and IOPcc were measured in the control group (n = 574) and the other groups: DG (n = 147), FHG (n = 78), GLD (n = 90), and OHT (n = 176). We performed a variance analysis (ANOVA) for all the dependent variables according to the different diagnostic categories with multiple comparisons to identify the differences between the diagnostic categories, deeming p < 0.05 as statistically significant.

RESULTS

The mean CH in the DG group (9.69 mmHg) was significantly lower compared to controls (10.75 mmHg; mean difference 1.05, p < 0.001), FHG (10.70 mmHg; mean difference 1.00, p < 0.05), GLD (10.63 mmHg; mean difference 0.93, p < 0.05) and OHT (10.54 mmHg; mean difference 0.84, p < 0.05). No glaucoma suspects (FHG, GLD, OHT groups) presented significant differences between themselves and the control group (p = 1.00). No statistically significant differences were found in the mean CRF between DG (11.18 mmHg) and the control group (10.75 mmHg; mean difference 0.42, p = 0.40). The FHG and OHT groups showed significantly higher mean CRF values (12.32 and 12.41 mmHg, respectively) than the DG group (11.18 mmHg), with mean differences of 1.13 (p < 0.05) and 1.22 (p < 0.001), respectively. No statistically significant differences were found in CCT in the analysis between DG (562 μ) and the other groups (control = 556 μ, FHG = 576 μ, GLD = 569 μ, OHT = 570 μ). The means of IOPg and IOPcc values were higher in the DG patient and suspect groups than in the control group, with statistically significant differences in all groups (p < 0.001).

CONCLUSION

This study presents corneal biomechanical values (CH, CRF), CCT, IOPg, and IOPcc for diagnosed glaucoma patients, three suspected glaucoma groups, and a healthy population, using the ORA. Mean CH values were markedly lower in the DG group (diagnosed with glaucoma damage) compared to the other groups. No significant difference was found in CCT between the DG and control groups. Unexpectedly, CRF showed higher values in all groups than in the control group, but the difference was only statistically significant in the suspect groups (FHG, GLD, and OHT), not in the DG group.

[Comparison of Goldmann tonometry with air-puff tonometry. A study of 159 patients in Abidjan]

PURPOSE

The goal of this study was to compare the intraocular pressure (IOP) values obtained with each of the tonometry methods as well as to study the effect of corneal pachymetry on the measurements obtained by each method.

MATERIAL AND METHODS

We carried out a cross-sectional, descriptive, analytical, prospective study in the ophthalmology department of a multispecialty clinic in Abidjan (Ivory Coast) from April 2018 to August 2018. Patients aged 15 and over were included in the study. Over this period, IOP was measured by Goldman Applanation Tonometer (HaagStreit, AT 900, Switzerland) and air-puff Tonopachymeter (Nidek, NT 530 P, Japan), which also permitted measurement of central optical corneal pachymetry. The data analyzed focused on socio-demographic characteristics, ophthalmologic history, tonometry, and central corneal pachymetry. The comparison of the values obtained by both devices and the effect of central corneal thickness (CCT) on tonometry were analyzed using EpiDataAnalysis V2.2.2.183 software.

RESULTS

We examined 318 eyes of 159 patients whose mean age was 40±12.57 years, range 16 to 82 years. The gender ratio was 1. A past ophthalmologic history was noted in 79.2% of patients. The mean IOP by Goldmann applanation tonometry was 12.75±3.17mmHg, and that by non-contact air-puff tonometry was 13.83±3.80mmHg. The mean central corneal thickness was 530.50±32.61μm. The difference between IOP measured by non-contact tonometry and that measured by contact tonometry was statistically significant, with P=0.00. There was no statistically significant relationship between central corneal pachymetry and contact tonometry (P=0.80). However, there was a statistically significant relationship between non-contact tonometry and central pachymetry (P=0.00). The values obtained with the air-puff tonometer are more affected by central corneal thickness.

CONCLUSION

The values obtained by Goldmann applanation tonometry are not equivalent to those obtained by non-contact air-puff tonopachymetry.

Evaluation of myopic cornea lenticules. A histochemical and clinical correlation

In this work, we have analyzed the main clinical and corneal histological parameters that may be associated to the spherical equivalent (SE), age and gender of individuals with myopic refractive errors. For this purpose, 108 cornea stroma lenticules were obtained from patients subjected to ReLEx-SMILE myopia correction. Histological analyses were carried out and histochemistry and immunohistochemistry were used to quantify key histological components of the cornea stroma, including mature collagen fibers, reticular and elastic fibers, glycoproteins, proteoglycans, type-V collagen and several crystallins. Clinical and histological data were analyzed to determine their association with SE, age and gender. Results showed a significant correlation between the age range of the patients and the expression of crystallins CRY-α-A, CRY-λ1 and type-V collagen and between CRY-λ1 and corneal thickness, spherical diopters (D) and SE, although correlation between CRY-λ1 and SE was non-significant when age was controlled. Comparison of cases with low myopia and high/moderate myopia found statistical differences for D and lenticule thickness and diameter. The binary logistic regression analysis allowed us to construct a model using two clinical parameters (D and lenticule thickness). Parameters showing significant correlation with the age were the corneal radius, keratometry reading (K), OZ, CRY-α-A and type-V collagen, whereas SE, lenticule thickness, OZ, CRY-λ1 and type-V collagen showed statistically significant differences between the youngest and the oldest patients. A binary logistic regression analysis model was generated including 3 variables (D, cornea radius and OZ). No gender differences were found. The specific clinical and histological modifications found to be associated to the SE and age could be useful for a better understanding of the mechanisms involved in the genesis or progression of myopia and could establish the basement for future therapeutic options.

Corneal Endothelial Cell Density and Morphology in Healthy Egyptian Eyes

Purpose

To evaluate the corneal endothelial cell density and morphology in normal Egyptian eyes.

Methods

In total, 568 healthy eyes of 568 Egyptian volunteers aged 20 to 85 years were examined using noncontact specular microscopy for the central corneal thickness (CCT), mean endothelial cell density (MCD), coefficient of variation (CV) in cell area, mean cell area (MCA), and hexagonal cell (Hex) percentage. Variables were compared between sexes and between different age groups.

Results

The mean CCT, MCD, and MCA were 514.45 ± 43.04 μm, 2647.50 ± 382.62 cells/mm², and 390.59 ± 149.94 μm², respectively. MCD and MCA showed no significant differences between men and women (P=0.171 and 0.099, respectively), whereas CV (%) and Hex (%) showed significant differences (P=0.024 and 0.015, respectively). CCT (P=0.007, r = −0.113) and MCD (P < 0.001, r = −0.357) exhibited a significant negative correlation with age, whereas CV (%) (P < 0.001, r = 0.341) and MCA (P=0.008, r = 0.111) exhibited a significant positive correlation. The mean rate of endothelial cell loss from 20 to 85 years of age was 0.3% per year.

Conclusions

Our results provide normative data for the corneal endothelium in healthy Egyptian eyes, thus increasing the knowledge base for corneal endothelial cell parameters in healthy Egyptian eyes. Furthermore, our findings can be used as baseline values for comparisons between Egyptian and other populations and for studies of the endothelial cell reserve and capacity for intraocular surgery and corneal transplantation.

Evaluation of Corneal Epithelial Thickness Imaged by High Definition Optical Coherence Tomography in Healthy Eyes

PURPOSE

To evaluate corneal epithelial thickness (CET) and corneal thickness (CT) in healthy eyes using spectral domain optical coherence tomography.

METHODS

Thirty-six healthy eyes were imaged using the Cirrus high-definition (HD)-optical coherence tomography device. The average CET and CT were assessed using Cirrus Review Software within predefined concentric corneal ring-shaped zones. Specific regions of CET (superior, inferior, temporal, nasal, superonasal, inferotemporal, superotemporal, and inferonasal) were also assessed. The difference between zones was compared between males and females.

RESULTS

The average CET was 48.3, 47.1, 46.1, and 45.8 μm in the 4 concentric zones (0-2, 2-5, 5-7, and 7-9 mm), respectively (P < 0.001). The average CT was 533.5, 550.8, and 579.4 μm in the 3 zones (0-2, 2-5, and 5-7 mm), respectively (P < 0.001). There was no statistically significant correlation between CET and CT in any of the measured zones. Males had thicker corneas than did females in each of the 3 CT zones (P < 0.05), but CET did not differ significantly. The CET superonasal-inferotemporal in 2.0 to 5.0 mm and CET superotemporal-inferonasal in 5.0- to 7.0-mm zones were significantly thinner in males than in females (-1.15 vs. 0.9 μm, -3.5 vs. -1.9 μm), respectively (P < 0.05).

CONCLUSIONS

Optical coherence tomography-based analysis of CET reveals that it is thinner in the periphery, whereas the total corneal thickness is greater. Although total CT seems to be influenced by sex, CET is not. Regional and sex-based variations in CT may need to be considered when assessing corneal and epithelial alterations in the setting of disease.

Corneal Endothelial Characteristics, Central Corneal Thickness, and Intraocular Pressure in a Population of Chinese Age-Related Cataract Patients

Purpose

To describe corneal endothelial characteristics, central corneal thickness, and intraocular pressure in a population of Chinese age-related cataract patients and to determine the effects of age, gender, hypertension, and body mass index (BMI).

Methods

1551 eyes were examined preoperatively. The parameters measured were endothelial cell density (CD), average cell area (CA), coefficient of variation (CV), cell hexagonality (HEX), central corneal thickness (CCT), intraocular pressure (IOP), and axial length (AL).

Results

There were significant differences in CV and BMI between genders. There was a significant decrease in CD, CCT, and IOP and, conversely, an increase in CA and BMI with increasing age. The patients who suffered from hypertension had bigger CA, less CD, and lower HEX than the patients who did not suffer from hypertension. CD has a negative correlation with age and CV and a positive correlation with CCT, CCT has a positive association with CD and IOP, and IOP had a negative relationship with age and a positive relationship with CCT, CA, and HEX.

Conclusions

Normative data for the corneal endothelium, central corneal thickness, and intraocular pressure in the normal age-related cataract patients are reported which will serve as a baseline for comparative studies about cataract.

Corneal Thickness in Highlanders

Patyal, Sagarika, Amit Arora, Arun Yadav, and Vijay K. Sharma. Corneal thickness in highlanders. High Alt Med Biol. 18:56-60, 2017.

BACKGROUND

Corneal thickness is an important parameter with diagnostic and therapeutic implications. Various studies have highlighted increase in corneal thickness in lowlanders on ascending to high altitude. However, there are no studies in the published literature pertaining to corneal thickness of the highlanders who are inhabitants of such altitudes. Hence, study was carried out with objective to determine the corneal thickness of highlanders living at heights of more than 11,000 feet and compare it with corneal thickness of lowlanders.

MATERIALS AND METHODS

The highlander participants of the study consisted of inhabitants of Ladakh region of India at an altitude of 11,000 feet or more and lowlander participants consisted of inhabitants at an altitude of 1500 feet. A total of 254 highlanders and 212 lowlanders participated. A mean of 25 measurements of central corneal thickness (CCT) of every participant was obtained for each eye using ultrasonic pachymeter.

RESULTS

The mean age of the participants was 41.8 (15.9) and 47.7 (17.7) years among lowlanders and highlanders, respectively. The highlanders had 11.95 μm lower mean CCT reading compared to lowlanders after adjusting for age and sex (p value <0.001). There was no statistically significant difference in mean CCT readings of right eye and left eye in either lowlanders or highlanders. Age also had a significant effect after adjustment for location and gender (p = 0.001). CCT decreased by 0.31 μm with every year increase in the age. Gender had no statistically significant effect.

CONCLUSION

This study found statistically significant difference in CCT measurements between highlanders and lowlanders. The thinner corneas of highlanders may have a bearing on diagnosis and treatment of glaucoma, refractive surgery, contact lens fitting implantation of Intacs, and astigmatic keratectomy done on such patients. The study also opens the scope of further research in the area.

Central corneal thickness of Iraqi population in relation to age, gender, refractive errors, and corneal curvature: a hospital-based cross-sectional study

BACKGROUND

Central corneal thickness (CCT) is an important indicator of corneal status. Its measurement provides valid information about corneal physiological condition and possible changes associated with diseases, traumas, and hypoxia. It is an integral part for interpretation of intraocular pressure and glaucoma patient management and in prerefractive procedure assessment.

OBJECTIVE

The aim of this study is to determine the mean CCT among a normal Iraqi population and to correlate between CCT and age, gender, refraction, and corneal curvature.

PATIENTS AND METHODS

This cross-sectional study was carried out at Ibn Al-Haitham Teaching Eye Hospital. A total of 418 eyes from 209 healthy individuals with an age range from 20 to 75 years were studied. CCT was measured by ultrasound pachymeter. Refraction was measured using an auto-refractor and confirmed by trial lenses and retinoscopy to calculate the spherical equivalent. Corneal curvature was measured using an auto-refracto-keratometer to calculate the average corneal curvature (AVK).

RESULTS

The mean CCT was 543.95±32.58 μm with a range from 422 to 636 μm. CCT was not affected by gender. CCT significantly negatively correlated with age and AVK. CCT significantly positively correlated with the spherical equivalence.

CONCLUSION AND RECOMMENDATION

Among an Iraqi population, CCT significantly decreased with age. Myopics had significantly thinner corneas. There was weak but significant negative correlation between CCT and corneal curvature. We recommend further studies about the relationship between central corneal thickness and other ocular parameters in Iraqi population such as the axial length.

Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea

Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

A curious fact: Photic sneeze reflex. Autosomical dominant compelling helio-ophthalmic outburst syndrome

OBJECTIVE

To assess ocular involvement in the pathophysiology of autosomal dominant compelling helio-ophthalmic outburst syndrome (ACHOOs).

METHODS

An interview was conducted with a Caucasian family that showed clinical features of ACHOOs. Twelve of them had photic reflex and were recruited. A complete eye evaluation was made.

RESULTS

A dominant autosomal inheritance with mild penetrance was demonstrated, with 67% of the studied subjects showing some degree of prominent corneal nerves. No other eye changes were found.

CONCLUSIONS

Prominent corneal nerves may be associated with ACHOOs. The other eye structures studied do not seem to play a role in ACHOOs. Further studies are needed to understand the physiology of the ACHOOs.

Is the central corneal thickness of diabetic patients thicker than that of non-diabetics’ eyes?

The purpose of the study was to evaluate central corneal thickness in diabetic patients and to compare the results with controls without diabetes mellitus. Sixty-five diabetic patients (65 eyes) constituted the study group, and 50 eyes were from the healthy control group (50 non-diabetic patients). The study group was subdivided into group 1 (no diabetic retinopathy, n = 35), group 2 (mild to moderate nonproliferative diabetic retinopathy, n = 20), and group 3 (proliferative diabetic retinopathy, n = 10). Central corneal thickness measurements in microns were determined using ultrasound pachymetry. The mean central corneal thickness was significantly greater in the study group (567.14 μm ± 14.63 μm) than in the control group (531.14 μm ± 5 μm). In addition, the mean central corneal thickness was found to be greater in group 3 (577 μm ± 12 μm) than in groups 1 (562 μm ± 13 μm) and 2 (566.86 μm ± 15 μm), but the difference did not reach statistical significance. We found that the mean central corneal thickness for diabetic patients was thicker than that of the healthy controls. Thicker central corneas associated with diabetes mellitus should be taken into consideration when obtaining accurate intraocular pressure measurements in diabetics.

Relationships between central and peripheral corneal thickness in different degrees of myopia

PURPOSE

To analyze the relationship between the central corneal thickness (CCT) and mid-peripheral corneal thickness (PCT) with the degree of myopia [axial length (AL) and spherical equivalent refractive error (SE)].

METHODS

175 right myopic eyes from 175 patients were divided according to the degree of SE: group #1 (n=76, <6.00 D), group #2 (n=72, between 6.00 and 12.00 D) and group #3 (n=27, >12.00 D). The CCT and PCT (3mm from the apex to the superior, inferior, nasal and temporal locations) were measured with the Orbscan-II. Relative peripheral index (RPI) was calculated by dividing the PCT by the CCT. The AL was measured with the IOL Master, and the SE was obtained with subjective refraction.

RESULTS

AL was 25.18±1.16 mm, 26.59±1.26 mm and 29.45±2.58 mm and SE was -3.31±1.40 D, -8.32±1.64 D and -16.44±4.48 D for groups #1, #2 and #3, respectively. Non-statistically significant differences in central and peripheral corneal thickness were found between groups (P>0.05 ANOVA). Non-significant relationship was found between central and peripheral corneal thickness with the AL and SE in the three study groups and in the total sample (r<0.24; P>0.05). The RPI values were similar between groups without significant difference between groups (P>0.05 ANOVA). Linear relationship was found between RPI superior location in group #2 (r=-0.23; P=0.04) and RPI nasal location in group #3 with the EE (r=0.41; P=0.03).

CONCLUSION

There are no significant differences among low, moderate and extremely myopic eyes related to the CCT and PCT. Corneal thickness is very similar in myopic eyes with small differences that are not clinically relevant to myopic patient management.

A genome-wide association study of central corneal thickness in Latinos

PURPOSE

Central corneal thickness (CCT) is a clinically important risk factor for primary open-angle glaucoma and keratoconus. Genetic factors controlling CCT in Latinos, the most populous minority population in the United States, are unclear. Here we describe the first genome-wide association study (GWAS) report of CCT in Latinos.

METHODS

We performed a GWAS for CCT on 1768 Latinos recruited in the Los Angeles Latino Eye Study (LALES) using Illumina's HumanOmniExpress BeadChip (∼730K markers). To discover additional associated single-nucleotide polymorphisms (SNPs), we imputed SNPs based on the 1000 Genomes Project reference panels. All subjects were 40 years of age and older. We used linear regression with adjustment for age, sex, and principal components of genetic ancestry.

RESULTS

we replicated the involvement of several previously reported loci, SUCH AS RXRA-COL5A1, FOXO1, and ZNF469, for CCT in Latinos (P 0.002). moreover, we discovered novel SNPS, RS3118515, RS943423, RS3118594, AND RS3132307, THAT REACHED GWAS SIGNIFICANCE (P 5 10(8)) in the uncharacterized LOC100506532 (GENE TYPE: miscRNA) for CCT in Latinos. By conditional analysis, we demonstrate that rs3118515 in this gene is responsible for the GWAS signal in the chromosome 9 RXRA-COL5A1 region in Latinos. Moreover, multiple sources of ENCODE evidence suggest that rs3118515 is in a regulatory region. Reverse-transcription PCR products indicated that transcripts of LOC100506532 surrounding rs3118515 were expressed in human corneas.

CONCLUSIONS

We discovered novel SNPs for CCT in Latinos and provided the first reported evidence of the corneal expression of LOC100506532. These results help to further increase our understanding of the genetic architecture of CCT.