Evaluation of choroidal perfusion changes in obese patients: ocular effects of insulin resistance / Avaliação das alterações da perfusão coroidiana em pacientes obesos: efeitos oculares da resistência à insulina

ABSTRACT Purpose: We aimed to evaluate choroidal per­fusion changes in obese patients using optical coherence tomography and dynamic contour tonometry, to determine whether these changes are associated with body mass index, and to assess the ocular effects of insulin resistance. Methods: We retrospectively evaluated the data of 32 obese patients with body mass index >30 kg/m2 and 45 healthy control individuals. Intraocular pressure and ocular pulse amplitude values of the patients were measured using dynamic contour tonometry, and the mean choroidal thickness was measured using enhanced depth imaging optical coherence tomography. Insulin resistance was assessed using the homeostasis model assessment-estimated insulin resistance index. Results: The mean choroidal thickness (294.30 ± 60.87 μm) and ocular pulse amplitude (2.10 ± 0.74) were lower, whereas the mean intraocular pressure (16.61 ± 2.35 mmHg) was higher in obese patients than in controls. There was a significant negative correlation between body mass index and ocular pulse amplitude (r=-0.274; p=0.029) and an insignificant negative correlation between mean choroidal thickness, intraocular pressure, and body mass index. There was an insignificant negative correlation between homeostasis model assessment-estimated insulin resistance index, mean choroidal thickness, and intraocular pressure and significant ne­gative correlation between homeostasis model assessment-estimated insulin resistance index and ocular pulse amplitude (r=-0.317; p=0.022). Conclusion: We found reduced mean choroidal thickness and ocular pulse amplitude and increased mean intraocular pressure in obese patients. These changes indicated a decrease in choroidal perfusion and ocular blood flow. It may be possible to detect ocular blood flow changes in obese patients through noninvasive assessment using the choroid. The negative correlation between insulin resistance and ocular pulse amplitude may be associated with intracellular fat accumulation in obese patients.

RESUMO Objetivo: Avaliar as alterações da perfusão coroidiana em pacientes obesos utilizando tomografia de coerência óptica e a tonometria de contorno dinâmico, para determinar se essas alterações estão associadas ao índice de massa corporal e avaliar os efeitos oculares da resistência à insulina. Métodos: Foram avaliados, retrospectivamente, os dados de 32 pacientes obesos, com índice de massa corporal >30 kg/m2, e 45 controles saudáveis. Os valores de pressão intraocular e da amplitude de pulso ocular dos pacientes foram medidos por meio de tonometria de contorno dinâmico e a espessura média da coroide foi medida por tomografia de coerência óptica com profundidade de imagem aprimorada. A resistência à insulina foi avaliada usando o índice de estimativa da resistência à insulina pelo modelo de homeostase. Resultados: A espessura média da coroideia (294,30 ± 60,87 μm) e a amplitude de pulso ocular (2,10 ± 0,74) foram menores, enquanto a pressão intraocular média (16,61 ± 2,35 mmHg) foi maior nos obesos do que nos controles. Houve uma correlação negativa significativa entre o índice de massa corporal e a amplitude de pulso ocular (r=-0,274; p=0,029) e uma correlação negativa insignificante entre a espessura média da coroide, a pressão intraocular e o índice de massa corporal. Houve uma correlação negativa insignificante entre a avaliação do modelo de homeostase - estimativa do índice de resistência à insulina, espessura média da coróide e pressão intraocular e correlação negativa significativa entre o modelo de avaliação de homeostase - o índice de resistência à insulina estimado e a amplitude de pulso ocular (r=-0,317; p=0,022). Conclusão: Encontramos redução da espessura média da coroide e da amplitude de pulso ocular e aumento da pressão intraocular em pacientes obesos. Essas alterações indicaram uma diminuição na perfusão coroidal e no fluxo sanguíneo ocular. Pode ser possível detectar alterações no fluxo sanguíneo ocular em pacientes obesos por meio de avaliação não invasiva usando a coróide. A correlação negativa entre a resistência à insulina e a amplitude de pulso ocular pode estar associada ao acúmulo de gordura intracelular em pacientes obesos.

Comparison of Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Relation to Central Corneal Thickness

PURPOSE: In this study we compared the intraocular pressures (IOPs) measured using dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) and investigated the correlation between central corneal thickness (CCT) and IOP. METHODS: In a prospective study, 178 eyes of 91 subjects with glaucoma and glaucoma suspect were enrolled. IOP was measured using DCT and GAT and CCT was measured using ultrasound pachymetry. Each eye was classified into 1 of 3 groups according to their CCT: low CCT (Group A; CCT or = 561 microm). In each group, we investigated the correlation between CCT and IOP measurement using GAT and DCT. RESULTS: A significant correlation was found between CCT and IOP measured using GAT (p < 0.001), but not between CCT and IOP measured using DCT (p = 0.108) in all patients. Subgroup analysis showed that CCT affected IOP measured with GAT only in Group A (p = 0.027) and IOP measured with DCT was not affected by CCT in all 3 groups. CONCLUSIONS: IOP measured using GAT and DCT were significantly affected by CCT, especially when the CCT was low. CCT may have no effect on DCT thus, IOP measured using DCT is more reliable than GAT in patients with thin corneas.

The Effect of Corneal Biomechanical Factors on Ocular Pulse Amplitude in Normal Subjects

PURPOSE: To investigate the influence of corneal biomechanical factors on ocular pulse amplitude measured using dynamic contour tonometry in normal subjects. METHODS: The study population consisted of normal subjects who visited the outpatient clinic from January, 2014 to July, 2014. Ocular pulse amplitude was measured using dynamic contour tonometry and corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using an ocular response analyzer. We applied univariate and multivariate linear regressions to investigate the relationship between ocular pulse amplitude and corneal biomechanical factors and other ocular factors. RESULTS: Fifty eyes of 50 patients (average age 52.8 +/- 17.2 years) were examined. The average ocular pulse amplitude was 2.90 +/- 1.04 mm Hg and the CH and CRF were 10.44 +/- 1.96 mm Hg and 11.03 +/- 2.21 mm Hg, respectively. In univariate linear regression, factors influencing ocular pulse amplitude were ocular pressure based on CRF (beta = 0.280, p = 0.049), Goldmann applanation tonometry (beta = 0.293, p = 0.039), and spherical equivalent (beta = 0.283, p = 0.047), while in multivariate linear regression the only factor influencing ocular pulse amplitude was CRF (beta = 0.686, p = 0.042). CONCLUSIONS: A positive correlation between ocular pulse amplitude reflecting ocular perfusion pressure and CRF reflecting corneal elasticity was observed. Correlations between the 2 factors will be an important aspect in future studies regarding the influences of corneal biomechanical factors on ocular perfusion pressure in glaucoma patients.

The Effect of Cataract Surgery on Ocular Pulse Amplitude

PURPOSE: To investigate the change of intraocular pressure (IOP) and ocular pulse amplitude (OPA) measured by dynamic contour tonometry (DCT) after cataract surgery and to identify the influencing factors related with OPA change after cataract extraction. METHODS: The present study included 32 patients who underwent unilateral cataract surgery and the non-operated fellow eyes were used as control. IOP was measured by Goldman applanation tonometry (GAT) and Pascal DCT preoperatively, and 3 months postoperatively. Additionally, OPA was measured by Pascal DCT preoperatively, and 3 months postoperatively. Axial length (AL), anterior chamber depth (ACD), and central corneal thickness (CCT) were measured preoperatively. RESULTS: After cataract surgery, IOP by GAT, IOP by DCT, and OPA decreased significantly with a mean decrement of 1.3 mm Hg, 1.6 mm Hg, and 0.5 mm Hg, respectively (p 0.05) postoperatively. The most important factor influencing the decrement of IOP by GAT, IOP by DCT, and OPA after cataract surgery was the preoperative level of their measurements (r = 0.382, p < 0.05 in GAT, r = 0.807, p < 0.001 in DCT, r = 0.627, p < 0.001 in OPA). In addition, the OPA decrement after cataract surgery was significantly correlated with age (r = -0.370, p = 0.037), and was not correlated with AL, ACD, and CCT. CONCLUSIONS: Both IOP and OPA decreased after cataract surgery, which appears to influence the relationship between IOP and OPA. The correlation between OPA decrement and age may be related to increased ocular rigidity with aging.

The Effect of Cataract Surgery on Ocular Pulse Amplitude

PURPOSE: To investigate the change of intraocular pressure (IOP) and ocular pulse amplitude (OPA) measured by dynamic contour tonometry (DCT) after cataract surgery and to identify the influencing factors related with OPA change after cataract extraction. METHODS: The present study included 32 patients who underwent unilateral cataract surgery and the non-operated fellow eyes were used as control. IOP was measured by Goldman applanation tonometry (GAT) and Pascal DCT preoperatively, and 3 months postoperatively. Additionally, OPA was measured by Pascal DCT preoperatively, and 3 months postoperatively. Axial length (AL), anterior chamber depth (ACD), and central corneal thickness (CCT) were measured preoperatively. RESULTS: After cataract surgery, IOP by GAT, IOP by DCT, and OPA decreased significantly with a mean decrement of 1.3 mm Hg, 1.6 mm Hg, and 0.5 mm Hg, respectively (p 0.05) postoperatively. The most important factor influencing the decrement of IOP by GAT, IOP by DCT, and OPA after cataract surgery was the preoperative level of their measurements (r = 0.382, p < 0.05 in GAT, r = 0.807, p < 0.001 in DCT, r = 0.627, p < 0.001 in OPA). In addition, the OPA decrement after cataract surgery was significantly correlated with age (r = -0.370, p = 0.037), and was not correlated with AL, ACD, and CCT. CONCLUSIONS: Both IOP and OPA decreased after cataract surgery, which appears to influence the relationship between IOP and OPA. The correlation between OPA decrement and age may be related to increased ocular rigidity with aging.

Relación entre amplitud del pulso ocular y presión intraocular: efectividad del tratamiento hipotensor / Association of ocular pulse amplitude and intraocular pressure and effectiveness of the hypotensive treatment

OBJETIVOS: Determinar la asociación entre la amplitud del pulso ocular y la tensión ocular en los pacientes con glaucoma primario de ángulo abierto según grupos de tratamiento. Evaluar la amplitud del pulso ocular como medio para medir la efectividad de la terapia antihipertensiva ocular. Definir correlación entre espesor corneal central/tensión ocular y entre espesor corneal/amplitud del pulso usando el tonómetro de contorno dinámico. MÉTODOS: Se estudiaron 90 pacientes mayores de 15 años con diagnóstico reciente de glaucoma primario de ángulo abierto que aún no habían recibido tratamiento alguno; con ellos se conformaron tres grupos de estudio de forma aleatoria y según el medicamento indicado: Grupo l: Timolol 0,5 por ciento, Grupo II: Travoprost (Travatán) 0,2 por ciento y Grupo III: Dorzolamida (Trusopt) 2 por ciento. A estos pacientes se les tomó la medida del espesor corneal central por paquimetría previa al tratamiento, a la semana, al mes y a los 3 meses en el servicio de glaucoma del Hospital Ramón Pando Ferrer(diciembre-2006 a mayo-2007). Se midieron además las variables presión intraocular y amplitud del pulso ocular. RESULTADOS: Se encontró menor amplitud del pulso a medida que disminuía la presión intraocular, existió mayor descenso de la presión y de la amplitud del pulso en el grupo tratado con Travoprost, hubo para este grupo de tratamiento una mejor correlación entre ambas variables. No se encontró correlación entre el espesor corneal central y presión intraocular, ni entre espesor corneal y amplitud del pulso. CONCLUSIONES: Monitorear la presión y la amplitud del pulso puede ser eficaz para conocer el efecto de la terapéutica hipotensora ocular

OBJECTIVES: To determine the association of the ocular pulse amplitude and the ocular pressure in patients with primary open angle glaucoma by groups under treatment; to evaluate the ocular pulse amplitude as a means to assess the effectiveness of anti-hypertensive ocular therapy and to define correlation between central corneal thickness/ocular pressure, and corneal thickness and pulse amplitude using the dynamic contour tonometer. METHODS: Ninety patients aged over 15 years, recently diagnosed with primary open angle glaucoma and still untreated, were studied. They were randomly included in three study groups according to the indicated drug, that is, Group I- 0,5 percent Timolol, Group II- 0,2 percent Travoprost (Travatan) and Group III- 2 percent Dorzolamide (Trusopt). Their central corneal thickness was measured by pachymetry prior to the treatment, and one week, one month and 3 months later at the the glaucoma service at Ramón Pando Ferrer Cuban Institute of Ophthalmology (December 2006-May 2007). Also the variables intraocular pressure and ocular pulse amplitude were taken. RESULTS: It was found that pulse amplitude decreases as the intraocular pressure goes down; higher decline in pressure and pulse amplitude existed in group under Travoprost treatment where the correlation of both variables was better. No correlation was observed between central corneal thickness and intraocular pressure; similarly the corneal thickness and the pulse amplitude did not correlate. CONCLUSIONS: Monitoring the pressure and the pulse amplitude may be effective to find out the effect of the ocular hypertensive therapy

Measurements of Dynamic Contour Tonometry After Penetrating Keratoplasty and EpiLASIK

PURPOSE:To analyze the clinical results of Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry (PDCT) and the influences of central corneal thickness and keratometric power in eyes that underwent EpiLASIK or penetrating keratoplasty. METHODS: Measurements of intraocular pressure by GAT and PDCT as well as keratometric power and central corneal thickness were measured in 45 eyes that underwent penetrating keratopasty and 63 eyes that underwent EpiLASIK. These parameters were also measured in healthy eyes with no specific disorders to create a control group. RESULTS: In the keratoplasty group, the PDCT results were significantly higher than the GAT results by 1.22+/-2.84 mmHg (p=0.006), but neither method showed a significant correlation with CCT or keratometric power. In the EpiLASIK group, PDCT was higher as 3.45+/-2.35 mmHg than GAT, and the corrected results of GAT were not different from the results of PDCT. In the control group, GAT was affected by central corneal thickness and keratometric power, but PDCT showed no significant relationship with these two factors. CONCLUSIONS: After EpiLASIK or penetrating keratoplasty, both of which change CCT and keratometric power, IOP cannot be accurately measured by GAT. In these patients, PDCT may play an important clinical role since it is less affected by corneal properties.

Comparison Between Dynamic Contour Tonometry and Goldmann Applanation Tonometry

PURPOSE: To compare the intraocular pressures (IOPs) measured by dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT), and to investigate the association of IOPs on eyes of varying central corneal thickness (CCT). METHODS: In this prospective study, 451 eyes of 233 subjects were enrolled. IOPs were measured by GAT and DCT. CCT was measured three times and the average was calculated. Each eye was classified into one of three groups according to CCT: low CCT (group A, CCT550 micrometer, n=142). In each group, we investigated the association of CCT with IOP measurement by GAT and DCT. RESULTS: The IOPs measured by GAT and DCT were significantly associated for all eyes (R=0.853, p<0.001, Pearson correlation). CCT was related with both IOP measurement by GAT and DCT with statistical significance (mixed effect model, p<0.001). However, subgroup analysis showed that CCT affected IOP measured by GAT for groups B and C, whereas it affected IOP measured by DCT only for group C. CONCLUSIONS: IOP measured by DCT was not affected by CCT in eyes with low to normal CCT, whereas this measurement was affected in eyes of high CCT range. CCT may have less effect on IOP measurements using DCT than those obtained by GAT, within a specified range of CCT.

Comparison of Dynamic Contour Tonometry and Goldmann Applanation Tonometry

PURPOSE: To compare dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) and investigate the influence of central corneal thickness (CCT) onintraocular pressure. METHODS: In a prospective study of 165 eyes with glaucoma (135 eyes), glaucoma suspect (14 eyes), and ocular hypertension (16 eyes), intraocularpressure was measured with DCT and GAT, and followed by measurement of the CCT with ultrasound pachymetry. Statistical analysis were performed with simple linear regression analysis and t-test using SPSS (Statistical software, ver. 10; SPSS Inc., Chicago, IL). RESULTS: A clear correlation between DCT and GAT was found (r=0.733, p<0.001). The average intraocular pressure was 14.92+/-2.28 mmHg with DCT and 13.97+/-3.12 mmHg with GAT, and the intraocular pressure with DCT was 0.95+/-2.49 mmHg higher than with GAT. A meaningful correlation was shown between GAT and CCT (r2=0.145, p<0.001), but was not demonstrated between DCT and CCT (r2=0.012, p=0.081). In addition, the difference of intraocular pressure between GAT and DCT (GAT-DCT) showed a significant correlation with CCT (r2=0.145, p<0.001). CONCLUSIONS: DCT appears to be a reliable method for intraocular pressure measurement, which is not influenced by CCT, unlike GAT.

Measurement of Intraocular Pressure after LASIK by Dynamic Contour Tonometry / 华中科技大学学报（医学）（英德文版）

Changes of corneal properties induced by laser in situ keratomileusis (LASIK) results in low inaccurate intraocular pressure (IOP) readings by Goldmann applanation tonometry (GAT).Before and after LASIK, the applied value of IOP, measured by dynamic contour tonometry (DCT)in comparison to GAT, was evaluated. Before and 1, 4 weeks after LASIK, the IOP in 30 cases (60 eyes) was measured by GAT and DCT respectively. The obtained results were statistically processed by SPSS11. 5 statistical software. The results showed that central corneal thickness (CCT)could affect GAT measurements but not DCT measurements. The comparison of IOP one and 4 weeks after LASIK revealed that the readings from GAT was separately decreased by 5.00±1.12 and 5.45±1. 13 mmHg as compared with those before LASIK, while those from DCT had no significant difference. It was concluded that LASIK-induced changes of CCT could influence the accuracy of GAT measurements, but had no influence on those from DCT. DCT was more beneficial to the measurements of IOP in normal eyes and those subject to LASIK surgery.