Changes in choroidal thickness, axial length, and ocular perfusion pressure accompanying successful glaucoma filtration surgery

The Effect of Change in Intraocular Pressure on Choroidal Structure in Glaucomatous Eyes

Purpose

Choroidal thickness increases linearly with intraocular pressure (IOP) lowering. We studied the relationship between the change in size of the choroidal vasculature and IOP lowering after glaucoma procedures.

Methods

Thirty eyes of twenty-nine patients were examined pre- and postoperatively for up to 6 months with standard clinical assessment, enhanced depth imaging spectral-domain optical coherence tomography (OCT), and axial length measurement. Each enhanced depth imaging spectral-domain OCT image was analyzed using three separate methods to determine the choroidal thickness, choroidal vessel thickness, choroidal interstitial thickness, large choroidal vessel layer thickness, medium choroidal vessel layer thickness, and light-dark ratio. Bivariate linear regression analysis was completed with largest change in IOP as the independent variable. The dependent variables included choroidal thickness, choroidal vessel thickness, and choroidal interstitial thickness, at the largest change in IOP. Multivariable regression analysis using a generalized estimating equation to account for multiple measurements per eye was also completed.

Results

Mean choroidal vessel thickness increases 1.5 μm for every 1 mm Hg decrease in IOP (P < 0.0001; 95% confidence interval [CI], 0.8, 2.1) and choroidal interstitial thickness increases 1.3 μm for every 1 mm Hg change in IOP (P < 0.0001; 95% CI, 0.8, 1.8). There was no significant association between change in IOP and change in large choroidal vessel layer temporally (P = 0.13), nasally (P = 0.20), or subfoveally (P = 0.18). There was also no association between IOP and the light-dark ratio (P = 0.16).

Conclusions

The increase in choroidal thickness at lower IOP is associated with approximately equal increases in its intravascular and extravascular compartments.

Enhanced Depth Imaging Optical Coherence Tomography: A New Way Measuring Choroidal Thickness in Pregnant Women

The body changes markedly during pregnancy; each system behaves differently from a nonpregnant state. As the eyes are the only windows to see directly what is going on in the internal environment, more and more researches have been done to explain the association between ocular changes and the physiological and pathological changes during pregnancy. The choroid is one of the critical parts of the eye, providing nutrition. And abnormal choroid may result in ocular dysfunction and visual problems. As the optical coherence tomography develops, a rapid, direct, noninvasive, and nontoxic way is available to obtain the choroid situation of pregnant women, which may explain the mechanism of pregnancy-related eye diseases. This review would summarize relevant original articles published from January 1, 2008 to December 1, 2016 to assess the changes of choroidal thickness (CT) with enhanced depth imaging optical coherence tomography (EDI-OCT) during pregnancy. And the relationship between choroidal thickness changes and pregnancy remains uncertain. To our knowledge, this is the first review of EDI-OCT in assessing the choroidal thickness of the pregnant women.

Choroidal thickness changes after dynamic exercise as measured by spectral-domain optical coherence tomography

Purpose:

To measure the choroidal thickness (CT) after dynamic exercise by using enhanced depth imaging optical coherence tomography (EDI-OCT).

Materials and Methods:

A total of 19 healthy participants performed 10 min of low-impact, moderate-intensity exercise (i.e., riding a bicycle ergometer) and were examined with EDI-OCT. Each participant was scanned before exercise and afterward at 5 min and 15 min. CT measurement was taken at the fovea and 1000 μ away from the fovea in the nasal, temporal, superior, and inferior regions. Retinal thickness, intraocular pressure, ocular perfusion pressure (OPP), heart rate, and mean blood pressure (mBP) were also measured.

Results:

A significant increase occurred in OPP and mBP at 5 min and 15 min following exercise (P ˂ 0.05). The mean subfoveal CT at baseline was 344.00 ± 64.71 μm compared to 370.63 ± 66.87 μm at 5 min and 345.31 ± 63.58 μm at 15 min after exercise. CT measurements at all locations significantly increased at 5 min following exercise compared to the baseline (P ˂ 0.001), while measurements at 15 min following exercise did not significant differ compared to the baseline (P ˃ 0.05). There was no significant difference in retinal thickness at any location before and at 5 min and 15 min following exercise (P ˃ 0.05).

Conclusion:

Findings revealed that dynamic exercise causes a significant increase in CT for at least 5 min following exercise.

Changes in the Choroidal Thickness and Axial Length Upon Mannitol Infusion in Patients With Asymmetric Intraocular Pressure

BACKGROUND/AIMS

To evaluate the changes in the choroidal thickness (CT) and axial length (AL) upon systemic mannitol infusion in glaucoma patients with asymmetric intraocular pressure (IOP).

MATERIALS AND METHODS

Forty glaucoma patients with asymmetric IOP, with the IOP of 1 eye ≥40 mm Hg and the fellow eye <25 mm Hg, were administered 150 mL of a 20% mannitol infusion to reduce the IOP. The CT and AL were measured before and an hour after the infusion. The relationship between the IOP reduction and the changes in the CT and AL were investigated.

RESULTS

The mean decrease in the IOP was -14.23 mm Hg (32.15%) and -4.13 mm Hg (21.40%) in the eyes with higher IOP and their fellow eyes, respectively. The mean changes in the subfoveal CT were 19.28 µm (9.20%; P<0.001) and 2.60 µm (1.93%; P=0.452) in the eyes with higher IOP and their fellow eyes, respectively. The mean changes in the AL were -0.10 µm (0.42%; P<0.001) and -0.33 mm (0.14%; P=0.008) in the eyes with higher IOP and their fellow eyes, respectively. Stepwise analysis revealed that the percent IOP change is the most influential factor on the percent change of the subfoveal CT (P<0.0001; R=0.3).

CONCLUSIONS

These results suggest that large IOP changes upon mannitol infusion cause the shortening of the AL in both the eyes and the thickening of the choroid only in the eyes with a higher IOP.

Topographic profile of choroid in eyes after acute primary angle-closure

OBJECTIVE

To characterize and compare the topographic profile of choroid in eyes after acute primary angle-closure (APAC) and in normal controls.

DESIGN, SETTING, AND PARTICIPANTS

A prospective observational study was conducted. Forty-four consecutive patients who had experienced unilateral APAC that was resolved by treatment were recruited. Seventy age- and sex-matched normal individuals were recruited as controls.

METHODS

Enhanced depth imaging-optical coherence tomography was used to measure choroidal thickness (CT) in 9 diffuse locations of macular region. The average CT was compared among each location in the APAC and control groups and between the same locations in the 2 groups.

RESULTS

Variants of CT at different macular locations were found in both groups; it was greatest at subfoveal locations and spread thinner around them, to reach a significant decrease (all p ≤ 0.05) 3 mm away in all directions from the fovea except for the superior direction in normal controls (p = 0.472). Among the 4 directions, the superior had the thickest CT in both groups, followed by the temporal, inferior, and nasal directions in both groups, whereas the APAC had a thicker choroid profile at each location (all p < 0.05). Univariate analysis showed that age, sex, anterior chamber depth, axial length, and spherical equivalent were all associated with the subfoveal choroidal thickness (SFCT) (all p < 0.1). Multivariable linear regression analysis showed that the SFCT was significantly thicker in association with an APAC diagnosis, shorter axial length, greater spherical equivalent refractive error, and younger female subjects (all p ≤ 0.05).

CONCLUSIONS

APAC eyes have a thicker choroid than normal eyes in the macular region, and the increase in CT in APAC eyes follows topographic distribution as in normal control eyes.

Longitudinal change in choroidal thickness after trabeculectomy in primary open-angle glaucoma patients

PURPOSE

To investigate longitudinal changes in intraocular pressure (IOP), axial length (AL), and choroidal thickness (ChT) in primary open-angle glaucoma (POAG) eyes after trabeculectomy and to evaluate the parameters that might influence those changes.

METHODS

In this prospective observational study, we recruited 28 patients with POAG (28 eyes) scheduled for trabeculectomy. The average macular ChTs and foveal retinal thicknesses along 6-mm segments centered on the fovea were examined preoperatively and postoperatively (at 1, 3, and 6 months) using swept-source optical coherence tomography. The IOP, AL, and mean deviation (MD) of standard automated perimetry (SAP) were also analyzed as independent variables.

RESULTS

Results from 16 patients were included in the final analysis. A significant increase in ChT with respect to the preoperative value was observed at every postoperative stage (1 month, P < 0.001; 3 months, P < 0.001; 6 months, P = 0.011), whereas the retinal thickness showed no significant change over the study period. The ChT increase and IOP reduction were sustained throughout the 6-month period without further significant changes. Stepwise multivariate analyses showed significant correlations between the percentage decrease in IOP and the percentage increase in ChT at 1 and 6 months postoperatively. The percentage increase in ChT was also significantly correlated with a better MD of the SAP at 1 month (β = 0.01; P = 0.009).

CONCLUSIONS

The ChT increase following trabeculectomy was sustained at 1, 3, and 6 months postoperatively. The percentage increase in ChT was significantly correlated with the percentage change in IOP and (more weakly) with better SAP MD values.

Ocular Biometric Changes after Trabeculectomy

This review article aimed to evaluate ocular biometric changes after trabeculectomy. The PubMed database was searched using the keywords "axial length" (AL), "anterior chamber depth" (ACD), "corneal astigmatism," "corneal topography" and "trabeculectomy." The extracted studies were categorized based on the evaluated parameters and the biometry method (contact and non-contact). Comparable studies with respect to their sample size were combined for statistical analysis. Twenty-five studies including 690 individuals which met the inclusion criteria were selected. After trabeculectomy, a significant and persistent AL reduction, with a range of 0.1-0.19 and 0.1-0.9 mm measured with contact and non-contact methods, respectively, was observed. With respect to topographic changes, 0.38-1.4 diopters (D) with-the-rule (WTR) astigmatism was induced postoperatively. All studies revealed ACD reduction immediately after surgery, which gradually deepened and approximated its preoperative levels on day 14. ACD reduction was not significant after that period in the majority of cases. In conclusion, changes in ACD is of small amount and of short period, thus it can be ignored; however, reported changes in AL and keratometry are of sufficient magnitude and can affect the refractive prediction of combined cataract surgery and trabeculectomy.

Changes in choroidal thickness after intraocular pressure reduction following trabeculectomy

PURPOSE

To evaluate the changes of peripapillary and subfoveal choroidal thickness (CT) after trabeculectomy.

METHODS

Prospective longitudinal study included 37 eyes with open-angle glaucoma. The subfoveal and peripapillary CT was measured using enhanced depth imaging spectral domain optical coherence tomography before trabeculectomy and 1 week, 3 and 6 months postoperatively. The associations between changes in the CT, intraocular pressure (IOP) and axial length were analysed.

RESULTS

The medium subfoveal CT (IQR) increased from 182 (97) μm at baseline to 267 (107) μm 1 week, 213 (97) μm 3 months and 207 (91) μm 6 months postoperatively (p < 0.001). The peripapillary CT increased in all four quadrants at all follow-ups (p < 0.05). The subfoveal and peripapillary choroidal thickening correlated with the magnitude of IOP reduction (p < 0.05) and axial length shortening (p < 0.01) during whole follow-up period. There was a peripapillary CT increase of 2.9 μm per mmHg of IOP reduction (p < 0.001, CI 1.5-4.4) and 4.8 μm per mm of baseline axial length (p = 0.049, CI 0.03-9.6) 1 week postoperatively after adjustment for baseline IOP. Six months postoperatively, the decrease in axial length was the only factor associated with peripapillary choroidal thickening (p = 0.031; regression coefficient: 73.29 μm/mm, CI 7.1-139.5).

CONCLUSION

Intraocular pressure (IOP) reduction after trabeculectomy caused the increase in subfoveal and peripapillary CT for at least 6 months postoperatively correlating with greater IOP reduction and axial length shortening. In the long term, the decrease in axial eye length, but not IOP, was the only factor to be associated with peripapillary choroidal thickening.

Morphological changes after trabeculectomy in highly myopic eyes with high intraocular pressure by using swept-source optical coherence tomography

Purpose

To investigate the effects of intraocular pressure (IOP) reduction on the eyeball shape in highly myopic eyes with high IOP.

Methods

This study included patients with an axial length ≥26.5 mm and high IOP ≥22 mmHg after receiving maximum medication, with successful trabeculectomy by a single surgeon, and who underwent swept-source optical coherence tomography (SS-OCT) examinations on preoperative and postoperative ≥3 months periods. Eight eyes of 7 patients were included in the analysis. The morphological changes in the eyeball that occurred pre- and post-operation were analyzed from the SS-OCT images.

Results

In 6 out of 8 examined eyes, the following apparent morphological changes in the posterior pole and/or peripapillary sclera were postoperatively detected on SS-OCT images: peripapillary scleral shrinkage, decrease in the lamina cribrosa depth, flattening of the peripapillary scleral insertion into the optic disc, decrease in the angle of the scleral protrusion temporal to the optic disc, and inhomogeneous change in scleral curvature of the posterior pole.

Conclusions and importance

We found that the shape of some eyes with high myopia and high IOP changed owing to the decrease in IOP. Eyeball deformities may be affected by high IOP, and IOP reduction might reduce scleral deformation in highly myopic eyes with high IOP.

Choroidal thickness of the papillomacular region in young healthy individuals

PURPOSE

To characterize the choroidal thickness of the papillomacular region in young healthy individuals using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Papillary and macular SD-OCT scans were obtained using an enhanced depth imaging mode. Digital retinography was used to assess any overlapping areas and to determine the papillomacular region. Spearman's correlations were used to explore the relationship between the different regional choroidal thicknesses.

RESULTS

Sixty-three volunteers aged 21.6 ± 1.1 years were included. There was a significant asymmetry in choroidal thickness throughout the 10-mm length model (p < 0.001). While the choroid was shown to thicken as the distance from the optic disc increased (p < 0.001), each of the 500-µm blocks of the papillomacular region were significantly thinner than their nasal counterparts (p < 0.02 in all pairwise comparisons).

CONCLUSION

In young healthy individuals, the choroid under the papillomacular region appears to be thinner than in other areas. These differences could relate to specificities of the retina overlying this region.

Change in choroidal thickness and axial length with change in intraocular pressure after trabeculectomy

BACKGROUND/AIMS

We studied the change in choroidal thickness (CT) and axial length (AL) after intraocular (IOP) changes produced by trabeculectomy.

METHODS

Twenty-one eyes of 20 patients were studied preoperatively, and then postoperatively at 1 week, 1, 3, and 6 months. Variables measured included IOP, AL, keratometry, refractive error, central corneal thickness, and average CT in the posterior 6 mm centred on the fovea using enhanced depth imaging spectral domain optical coherence tomography (OCT).

RESULTS

OCT images in 17 eyes (58 images, preoperatively and postoperatively) were of sufficient quality to determine CT. In every patient, CT increased with IOP lowering postoperatively. For each 1 mmHg decrease in IOP, there was a mean increase of 3.4 µm in CT (p<0.0001; univariate regression, 95% CI 2.5 to 4.3). This represented a CT increase of 1.7% per mm Hg decrease (p<0.0001; 95% CI 1.3 to 2.0%). AL decreased by 6.8 µm per mm Hg decrease in IOP (p<0.0001, univariate regression, 95% CI 4.9 to 8.6).

CONCLUSIONS

The dynamic relationship between change in IOP and the state of sclera and choroid was confirmed by sequential measurements in postoperative trabeculectomy patients, providing estimates of the magnitude of choroidal swelling and scleral volume decrease with IOP lowering.