Ocular Hypertension and Corneal Thickness: A Long-Term Prospective Study. Results after Two Years

Blue-on-yellow perimetry and corneal thickness in patients with ocular hypertension

AIM

To evaluate the frequency of blue-on-yellow perimetry (B/YP) deficits in ocular hypertension (OHT) patients and to correlate these findings with central corneal thickness (CCT), and to investigate the influence of age, refraction and gender on the B/YP results in OHT patients.

METHODS

The B/YP and CCT were checked respectively in 72 OHT patients with normal white-on-white perimetry(W/WP) and normal optic nerve head. The B/YP was tested by Octopus 101 automated perimetry using G2 strategy, while the CCT was checked with DGH-550 ultrasound pachymeter. All patients were chosen randomly one eye for statistical analysis, a binary regression model was used to determine the independent contribution of variables included in the model, and the differences of the intraocular pressure (IOP), CCT, age, refraction and gender between the normal B/YP group and abnormal B/YP group were compared.

RESULTS

Forty-nine out of 72 patients with OHT showed normal B/YP results, whereas 23 of 72 patients(31.9%) demonstrated abnormal B/YP results. CCT showed a correlation with the B/YP results (B=-0.038, SE=0.019, P=0.044), whereas none of the IOP, age, refraction and gender was found to be correlated with the B/YP results. The mean CCT in OHT patients with abnormal B/YP group was lower than that with normal B/YP group (t=2.066, P=0.043).There was a significant positive correlation between IOP and CCT (R(2)=0.513, P=0.000).

CONCLUSION

The mean CCT in OHT patients with abnormal B/YP results was lower than that with normal B/YP results. There was a significant positive correlation between IOP and CCT in OHT patients. The age, refraction and gender didn't influence the B/YP results in OHT patients.

Assessing the relationship between central corneal thickness and retinal nerve fiber layer thickness in healthy subjects

PURPOSE

To determine the relationship between central corneal thickness (CCT) and retinal nerve fiber layer (RNFL) thickness obtained by scanning laser polarimetry (GDx-VCC; Carl Zeiss Meditec, Dublin, California, USA), confocal scanning laser ophthalmoscopy (HRT II; Heidelberg Engineering, Heidelberg, Germany), and optical coherence tomography (Stratus OCT; Carl Zeiss Meditec).

DESIGN

Multicenter clinical trial, retrospective cross-sectional study.

METHODS

One hundred and nine healthy subjects from the Advanced Imaging in Glaucoma Study were enrolled in this study. All subjects had a standard clinical examination, including visual field (VF) and good-quality scans from all three imaging devices. CCT was measured using an ultrasonic pachymeter. A linear mixed-effects model was used to assess the relationship between RNFL thickness and CCT, accounting for clustering of eyes within subjects, testing site, ethnicity, family history of glaucoma, axial length intraocular pressure, and VF global indices.

RESULTS

For OCT and GDx, there was a slight nonstatistically significant positive relationship between CCT and RNFL thickness. For HRT, there was a slight nonstatistically significant negative relationship between CCT and RNFL thickness. Relationships for each device were found to differ between sites.

CONCLUSIONS

CCT was not statistically significantly related to RNFL thickness in healthy eyes.

Relationship between central corneal thickness and hypotony maculopathy after trabeculectomy

PURPOSE

To study the relationship of central corneal thickness and other factors and the development of hypotony maculopathy (HM).

DESIGN

Prospective case-control study.

PARTICIPANTS

Thirteen patients with HM and 25 controls with hypotony (defined as intraocular pressure [IOP] of 6 mmHg or less) without signs of maculopathy after trabeculectomy or combined phacotrabeculectomy.

METHODS

Information from consecutive patients and controls was collected in a prospective manner. Factors associated with presence of HM were investigated by comparing the findings in the 2 groups in univariate and multivariate analysis.

MAIN OUTCOME MEASURES

The following factors were investigated: demographic factors (age and gender), presenting IOP, central corneal thickness (CCT), refractive error, type of glaucoma surgery, and presence of choroidal effusion, among others.

RESULTS

Among the variables evaluated, a significant difference between the 2 groups was observed in the age of the patients (patients with HM being significantly younger: 59+/-20 years vs. 73+/-9 years; P = 0.015) and in CCT (eyes with HM having significantly thicker cornea: 553+/-51 microm vs. 506+/-34 microm; P = 0.004). Both predictive factors (younger age and thicker CCT) persisted as significant in a multivariate logistic regression analysis. The measured IOP during hypotony was similar between eyes with HM and hypotony alone (4.7+/-3.2 mmHg and 3.9+/-1.6 mmHg, respectively; P = 0.649). No differences in gender, type of surgery, presence of choroidal detachment, lens status, or degree of myopia were observed between the 2 groups.

CONCLUSIONS

This study shows that patients with hypotony and thinner central corneas have a lower risk of experiencing maculopathy. This association may result from the influence of CCT on applanation tonometry, although we can not rule out that CCT is related to the development of HM by other mechanisms. This study suggests that CCT should be taken in consideration when setting a target pressure after glaucoma filtering surgery, particularly if the target IOP is low.

Corneal thickness and visual field damage in glaucoma patients

PURPOSE

To verify whether there was a significant correlation between central corneal thickness (CCT) and visual field damage in patients with primary open angle glaucoma (POAG).

METHODS

A total of 99 eyes with POAG were consecutively recruited. Patients were classified as glaucomatous based on visual field and optic nerve head damage. All underwent applanation tonometry, Humphrey perimetry, and measurement of CCT with ultrasonic pachymetry. Based on CCT value, the sample was split at the mode in two groups (group 1<535 microm, n=49; group 2>or=535 microm, n=50).

RESULTS

Entire cohort: mean CCT 554 microm+/-45.03; mean deviation (MD) -6.68 dB+/-7.32; pattern standard deviation (PSD) 5.33+/-3.75; intraocular pressure (IOP) 17.91+/-4.16 mmHg with treatment. Group 1: CCT was 504.8 microm+/-30.8; MD -9.01 dB+/-8.72; PSD 6.38+/-3.99; IOP 18.02 mmHg+/-4.66. Group 2: mean CCT 574.6 microm+/-35.03; MD -4.39 dB+/-4.70; PSD 4.25+/-3.19; IOP 17.79 mmHg+/-3.57. A significant difference was found between the two groups for both MD and PSD. Linear regression analysis showed a significant correlation between CCT and PSD (P<0.001).

CONCLUSIONS

Our data show that patients with a thinner cornea had a worse MD and PSD. As a thinner CCT causes an underestimation of the true IOP, there may be a delay in the diagnosis of POAG or an inadequate estimate of the clinical course despite apparently desirable IOP applanation readings.