Structural and biomechanical corneal differences between patients suffering from primary congenital glaucoma and healthy volunteers

Changes in corneal biomechanics in patients with glaucoma: a systematic review and meta-analysis

INTRODUCTION

Corneal biomechanics has been implicated in a variety of ocular diseases. The purpose of this study was to evaluate the relationship between the glaucoma and corneal biomechanical properties, and exploring the value of corneal biomechanics in the diagnosis and follow-up of glaucoma diseases.

METHODS

We searched studies in PubMed, EMBASE, Web of Science and clinicaltrials.gov., as of October 8, 2022. Only English studies were included, without publication time limit. We also searched the reference lists of published reviews. This meta-analysis was conducted with random-effects models, we used mean difference(MD) to evaluate the outcome, and the heterogeneity was assessed with the I2 statistic. Subgroup analyses were performed under the appearance of high heterogeneity. We used 11 items to describe the characteristics of included studies, publication bias was performed through the Egger's test. The quality assessment were evaluated by Newcastle-Ottawa Scale(NOS) items.

RESULTS

A total of 27 eligible studies were identified for data synthesis and assessment. The result of meta-analysis showed that in the comparison of included indicators, the corneal biomechanics values of glaucoma patients were statistically lower than those of normal subjects in a similar age range. The covered indicators included central corneal thickness(CCT) (MD = -8.34, 95% CI: [-11.74, -4.94]; P < 0.001), corneal hysteresis(CH)(MD = -1.54, 95% CI: [-1.88, -1.20]; P < 0.001), corneal resistance factor(CRF)( MD = -0.82, 95% CI: [-1.21, -0.44]; P < 0.001), and intraocular pressure(IOP)( corneal-compensated intraocular pressure (IOPcc): MD = 2.45, 95% CI: [1.51, 3.38]; P < 0.001); Goldmann-correlated intraocular pressure (IOPg): MD = 1.30, 95% CI: [0.41, 2.20]; P = 0.004), they all showed statistical difference. While the value of axial length(AL) did not show statistically different(MD = 0.13, 95% CI: [-0.24, 0.50]; P = 0.48).

CONCLUSION

Corneal biomechanics are associated with glaucoma. The findings can be useful for the design of glaucoma screening, treatment and prognosis.

Corneal characteristics and OCT-angiography findings in pediatric glaucoma and glaucoma suspects

PURPOSE

To analyze corneal biomechanics, specular microscopy, and optical coherence tomography-angiography findings in children with glaucoma.

METHODS

Pediatric patients (<18 years of age) with glaucoma (n = 38), increased cup:disk ratio and normal intraocular pressure (IOP) glaucoma suspects (n = 36), and controls (n = 67) were prospectively enrolled. Patients underwent testing with Ocular Response Analyzer, CellChek Specular Microscope, and Heidelberg OCT-A.

RESULTS

Average age of participants was 12.4 ± 3.5 years, with no difference between groups (P = 0.71). Glaucoma patients had undergone more intraocular surgeries (P < 0.0001) and showed worse logMAR visual acuity (P < 0.0001) than suspects or controls. Central corneal thickness (CCT) was greater in glaucoma patients (642.8 ± 85.9 μm [P < 0.0001]) and suspects (588 ± 43.7 μm [P = 0.003]) compared with controls (561 ± 39.9 μm). Corneal hysteresis (CH) was decreased in eyes with glaucoma (10.4 ± 3.0) compared with controls (11.7 ± 1.5 [P = 0.006]), but not suspects (11.3 ± 2.0 [P = 0.1]). Glaucoma patients had lower endothelial cell density (2028.4 ± 862.7 [P < 0.0001]) and greater average cell area (547.2 ± 332.4 [P < 0.0005]) compared with suspects (2919.3 ± 319.1, 347.5 ± 46.2) and controls (2913.7 ± 399.2, 350.8 ± 57.7), but there was no difference in polymegathism (P = 0.12) or pleomorphism (P = 0.85). No differences in vessel density or vessel skeletal density in the retinal vascular complex (P = 0.3077, P = 0.6471) or choroidal vascular complex (P = 0.3816, P = 0.7306) were detected.

CONCLUSIONS

Children with glaucoma showed thicker corneas with lower endothelial cell density and greater cell area, but no difference in retinal/choroidal vascular densities compared with suspects and controls.

Incidence and outcomes of microbial keratitis after cyclophotocoagulation to treat childhood refractory glaucoma

PURPOSE

To report the incidence and outcomes of microbial keratitis (MK) following cyclophotocoagulation (CPC) for treatment of refractory childhood glaucoma (CG) at a single center over a period of 6 years.

METHODS

In this cohort study, the medical records of children with CG who underwent CPC and subsequently presented with MK from 2014 to 2020 were reviewed retrospectively. Data were collected on age, type of glaucoma, surgeries before MK, CPC parameters, interval between CPC and MK, presenting symptoms of MK, infiltrate location, bacterial isolates, MK treatment, and outcomes.

RESULTS

Among the 312 children who underwent CPC during the study period, 37 eyes of 33 children had MK, with an incidence of 1.8% (95% CI, 0.3-3.2). The median interval between CPC and MK was 4 years (IQR, 2.7-7.4). CPC was repeated once in 20 eyes (54%) and twice in 4 (11%). In 20 eyes, there was no pain at MK onset. The primary isolates were Streptococcus pneumoniae (12/27 [22%]) and Staphylococcus epidermis (8/27 [30%]). MK resolved in 17 eyes (46%) after treatment; 8 eyes (22%) underwent evisceration or had phthisis, and keratoplasty failed in 6 eyes (16%). The absence of pain at presentation with MK was negatively associated with resolution (OR = 5.0 [95% CI, 1.1-23.8]; P = 0.04).

CONCLUSIONS

The absence of pain at MK onset may be a proxy for neurotrophic keratitis after CPC and is linked to poor response to management.

Effects of Corneal Biomechanical Properties on Rebound Tonometry (Icare200) and Applanation Tonometry (Perkins) Readings in Patients With Primary Congenital Glaucoma

OBJECTIVE

The aim was to assess the influence of corneal biomechanics on intraocular pressure (IOP) measurements made with the Icare200 (IC200) rebound tonometer and the Perkins handheld applanation tonometer in patients with primary congenital glaucoma (PCG).

MATERIALS AND METHODS

A total of 40 PCG patients and 40 healthy controls, age, and sex-matched, were recruited. IOP was measured with the Ocular Response Analyzer (IOPc, IOPg), IC200 and Perkins. The variables age, IOP, corneal hysteresis (CH), corneal resistance factor (CRF), central corneal thickness (CCT), best-corrected visual acuity, spherical equivalent, medications, and glaucoma surgeries were recorded for each subject. Univariate and multivariate analysis were used to detect effects of variables on IOP measurements.

RESULTS

Mean CCT was 545.65±71.88 μm in PCG versus 558.78±27.58 μm in controls (P=0.284). CH and CRF were significantly lower in PCG group than in control group: mean CH 8.11±1.69 versus 11.15±1.63 mm Hg (P<0.001), and mean CRF 9.27±2.35 versus 10.71±1.75 mm Hg (P=0.002). Mean differences between IOP IC200-Perkins were 0.79±0.53 mm Hg in PCG versus 0.80±0.23 mm Hg in controls (P<0.001) and mean differences IC200-IOPc were -0.89±5.15 mm Hg in PCG (P<0.001) versus 1.60±3.03 mm Hg in controls (all P<0.009). Through multivariate analysis, CRF showed positive association and CH negative association with IOP measured with Perkins or IC200 in both subject groups. No association was detected for CCT, age, or sex.

CONCLUSION

CH and CRF were identified as the main factors interfering with IOP measurements made with both tonometers in patients with PCG and healthy controls.

Agreement between rebound (Icare ic200) and applanation tonometry (Perkins) in patients with primary congenital glaucoma

PURPOSE

To examine agreement between intraocular pressure (IOP) measurements made using the rebound tonometer Icare ic200 (RT200) and the Perkins handheld applanation tonometer (PAT) in patients with primary congenital glaucoma (PCG). The impacts of several covariables on measurements using the two devices were also assessed.

MATERIALS AND METHODS

Intraocular pressure measurements were made in a single session in 86 eyes of 86 patients with PCG (46 under anaesthesia, 40 in the office). The order was RT200 then PAT. The variables age, central corneal thickness (CCT), corneal state and anaesthesia were recorded in each patient. Data were compared by determining interclass correlation coefficients (ICC) for each tonometer and representing the differences detected as Bland-Altman plots. Effects of covariables were assessed through univariate and multivariate regression.

RESULTS

Mean IOP difference between tonometers (RT200 minus PAT) was 1.26 mmHg (95%: 0.22-2.31). Absolute agreement (ICC) was 0.73 (95% CI: 0.62-0.82). Lower and upper limits of agreement (95%) were -8.06 mmHg (95% CI: -9.87 to -6.25) and 10.59 mmHg (95% CI: 8.77-12.40), respectively. The tonometers showed systematic differences (a = -4.63 mmHg; 95% CI: -9.11 to -1.44) and proportional differences; for each mmHg increase in PAT-IOP, the RT200 reading increased by 1.28 mmHg (b = 1.28; 95% CI: 1.12-1.53). None of the variables tested as predictors were able to explain differences between the tonometers.

CONCLUSIONS

Despite the good overall agreement between both tonometers, caution should be taken in high values of IOP, considering the interchangeability of its readings as systematic and proportional differences appear to exist between both methods.

Corneal densitometry and biomechanical properties in patients with primary congenital glaucoma

OBJECTIVE

To describe corneal densitometry, topographic measurements, and biomechanical properties in patients with primary congenital glaucoma (PCG) and healthy patients. To examine correlations between variables and determine their glaucoma diagnostic capacity.

METHODS

This was a cross-sectional, case-control study conducted in 50 eyes of 50 patients with PCG (G1) and 40 eyes of 40 healthy patients (G2). The variables determined in each participant were: intraocular pressure, best corrected visual acuity (BCVA), corneal densitometry, topographic data using the Pentacam HR-Scheimpflug imaging system (Oculus Optikgerate GmbH, Wetzlar, Germany), and corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY).

RESULTS

Overall densitometry was significatively higher in the PCG group (G1: 17.94 ± 4.99 vs G2: 13.25 ± 1.96, p < 0.001). CH (G1: 8.02 ± 11.35 vs G2: 11.35 ± 1.42, p < 0.001) and CRF (G1: 9.48 ± 2.83 vs G2: 10.77 ± 1.34, p < 0.001) were lower in the glaucoma group. Mean posterior, central, and anterior elevation and mean keratometry were higher in G1 (p < 0.05). In the PCG group, overall densitometry showed significant correlation with CH (r = -0.321, p = 0.028) and with BCVA (r = -0.498, p = 0.002). AUCs (areas under the curve) for CH and overall densitometry were high (0.839 and 0.899 respectively) and the best overall densitometry; CH and CRF cutoffs were 14.0, 9.3 and 9.2 respectively.

CONCLUSION

Densitometry is increased, and biomechanical corneal properties are decreased in patients with PCG. Densitometry and visual acuity showed a negative and significant correlation, so this measurement could be used as an indirect parameter of BCVA in the clinical practice.

Corneal densitometry and topography in patients with primary congenital glaucoma

OBJECTIVE

To compare corneal densitometry and topography variables in patients with primary congenital glaucoma (PCG) and healthy subjects.

MATERIAL AND METHODS

Cross sectional study, consecutive recruitment with gender- and age-matched control group. Forty eyes of 40 patients in each group were studied with Pentacam corneal topography. The variables compared between the two groups were: intraocular pressure (IOP), visual acuity (VA) and Pentacam (Oculus, Wetzlar, Germany) corneal topography measurements: mean and maximum keratometry (Km, Kmax), cylinder (Cyl), anterior elevation apex (AEA), central anterior elevation (CAE), maximum anterior elevation (MAE), posterior elevation apex (PEA), central posterior elevation (CPE), maximum posterior elevation (MPE), pachymetry and anterior, mid-stromal and posterior corneal densitometry in the 0-2mm, 2-6mm, 6-10mm zones.

RESULTS

Significant differences between patients and healthy controls were detected in the topographic variables MAE (P=0.002) and MPE (P<0.001), and in all the densitometry variables (anterior, mid-stromal, posterior for the 0-2mm, 2-6mm and 6-10mm zones) (P<0.001 each). In the PCG group, negative correlation was observed between VA and total densitometry (r=-0.49; P=0.004).

CONCLUSION

Patients with PCG and healthy subjects display differences in corneal densitometry and topographic measurements. PCG patients show greater corneal density with an inverse relationship between visual acuity and higher elevation (anterior and posterior values).

Influence of Axial Length on Intraocular Pressure Measurement With Three Tonometers in Childhood Glaucoma

PURPOSE

To determine the agreement between intraocular pressure (IOP) measurements obtained using the handheld version of the Goldmann applanation (Perkins; Clement-Clarke, Haag-Streit, Harlow, United Kingdom), rebound Icare-Pro (Icare, Tiolat Oy, Helsinki, Finland), and Tonopen XL (Reichert Inc., Depew, NY) tonometers in children with childhood glaucoma and to identify factors that may affect those measurements.

METHODS

Ninety-one eyes of 46 children with early-onset childhood glaucoma were included in this cross-sectional study in which IOP, ocular axial length, anterior chamber depth, lens thickness, vitreous length, and central corneal thickness measurements were obtained under general anesthesia. Agreement between tonometers was evaluated using intraclass correlation coefficients (ICCs) and the Bland-Altman method. The influence of ocular biometric parameters and central corneal thickness on IOP measurements was analyzed using multiple linear regression analysis.

RESULTS

The mean age of the children in the current study was 29.1 months (range: 13 to 31 months). The Icare-Pro and Tonopen XL overestimated IOP measurements compared to the Perkins tonometer (Icare-Pro-Perkins mean IOP difference: 2.2 ± 3.4 mm Hg, P < .0001, 95% confidence interval [CI]: 1.5 to 2.9 vs Tonopen XL-Perkins mean IOP difference: 6.7 ± 7.1 mm Hg, P < .0001, 95% CI: 5.2 to 8.2). The Icare-Pro showed greater agreement with the Perkins tonometer than the Tonopen XL (ICC: 0.789, 95% CI: 0.697 to 0.856, P < .0001 vs 0.453, 95% CI: 0.272 to 0.603, P < .0001). Ocular axial length affected IOP measurements the most, finding increased impact on Tonopen XL (slope: 0.086, 95% CI: 0.013 to 0.16, P = .022 vs 0.997, 95% CI: 0.369 to 1.625, P = .002 vs 1.571, 95% CI: 0.541 to 2.602, P < .0001 for Perkins, Icare-Pro, and Tonopen XL IOP measurements, respectively).

CONCLUSIONS

Ocular axial length affects IOP measured by the Perkins, Icare-Pro, and Tonopen XL devices in patients with childhood glaucoma. The Icare-Pro shows more agreement with the Perkins tonometer than the Tonopen XL; therefore, it seems to be a more suitable option for these patients. [J Pediatr Ophthalmol Strabismus. 2020;57(1):27-32.].