Changes in Corneal Thickness in Patients With Treated and Untreated Ocular Hypertension

Comparison of Central Corneal Thickness Measurements Using Optical and Ultrasound Pachymetry in Glaucoma Patients and Elderly and Young Controls

PRéCIS:: Optical and ultrasound pachymetry cannot be used interchangeably in young, healthy adults. In elderly, healthy and glaucoma patients the speed of ultrasound in the cornea increases because of changing corneal biomechanical characteristics in age and disease and the different devices could be used interchangeably.

PURPOSE

The purpose of this study was to compare central corneal thickness (CCT) using optical and ultrasound pachymetry in patients with open-angle glaucoma and young as well as elderly, healthy controls. Further to investigate whether the devices could be used interchangeably.

METHODS

In total, 69 eyes of 41 glaucoma patients, 51 eyes of 32 elderly and 50 eyes of 25 young controls were consecutively included in this cross-sectional observational study. Optical CCT measurements were obtained using the noncontact Specular Microscope CEM-530 (NCSM). Ultrasound pachymetry (USP) was measured using the Pachy Meter SP 3000.

RESULTS

In young subjects (27.2±4.8 y), the mean CCT taken with NCSM and USP was 562.1±33.6 μm and 565.8±35.8 μm, respectively. This was significantly different (USP>NCSM, P=0.019). In elderly subjects (70.6±10.7 y) CCT measured with NCSM (562.5±27.8 μm) compared to USP (564.9±27.1 μm) was not statistically significantly different (P= 0.121). In glaucoma patients (65.0±11.1 y), USP measured thinner CCT values compared to NCSM, without significant differences between the devices (NCSM 525.3±32.3 μm; USP 522.9±33.15 μm; P=0.067). CCT was significantly thinner in comparison to both healthy groups (P< 0.001).

CONCLUSIONS

In young subjects, ultrasound pachymetry measurements are higher than they are with optical pachymetry. This difference is no longer observed in elderly subjects and is even reversed in glaucoma patients. A higher speed of ultrasound in the cornea due to changing corneal biomechanical properties in the elderly and glaucoma patients could explain this. The devices could be used interchangeably in older and glaucoma patients, but not in young individuals.

Corneal thickness as a predictor of corneal transplant outcome

PURPOSE

To assess corneal thickness (CT) and correlation with graft outcome after penetrating keratoplasty in the Cornea Donor Study.

METHODS

A total of 887 subjects with a corneal transplant for a moderate-risk condition (principally Fuchs dystrophy or pseudophakic corneal edema) had postoperative CT measurements throughout a 5-year follow-up time. Relationships between baseline (recipient, donor, and operative) factors and CT were explored. Proportional hazards models were used to assess the association between CT and graft failure. Relationship between CT and cell density was assessed with a longitudinal repeated measures model and Spearman correlation estimates.

RESULTS

Higher longitudinal CT measurements were associated with the following: diagnosis of pseudophakic or aphakic corneal edema (P < 0.001), intraocular pressure >25 mm Hg during the first postoperative month (P = 0.003), white (non-Hispanic) donor race (P = 0.002), and respiratory causes of donor death (P < 0.001). Among those without graft failure within the first postoperative year, the 5-year cumulative incidence (± 95% confidence interval) of graft failure was 5% ± 5% in those with a 1-year CT ≤ 500 μm, 5% ± 3% for CT 501 to 550 μm, 7% ± 4% for CT 551 to 600 μm, and 20% ± 11% for CT >600 μm. In a multivariate analysis, both 1-year CT and cell density were associated with subsequent graft failure (P = 0.002 and 0.009). CT increase was modestly associated with endothelial cell loss during follow-up (r = -0.29).

CONCLUSIONS

During the first 5 years after penetrating keratoplasty, CT can serve as a predictor of graft survival. However, CT is not a substitute for cell density measurement because both measures were independently predictive of graft failure.

Relationship of Fuchs endothelial corneal dystrophy severity to central corneal thickness

OBJECTIVE

To define the relationship between Fuchs endothelial corneal dystrophy (FECD) severity and central corneal thickness (CCT).

METHODS

We examined 1610 eyes from a subset of index cases, family members, and unrelated control subjects with normal corneas from the FECD Genetics Multi-Center Study. To estimate the association between FECD severity grade (7-point severity scale based on guttae confluence) and CCT measured by ultrasonographic pachymetry, a multivariable model was used that adjusted for eye, age, race, sex, history of glaucoma or ocular hypertension, diabetes mellitus, contact lens wear, intraocular pressure, and familial relationship to the index case. An interaction between FECD severity grade and edema (stromal or epithelial) on slitlamp examination findings was used to investigate whether the effect of FECD severity grade on CCT differed between those with and without edema.

RESULTS

Average CCT was thicker in index cases for all FECD grades compared with unaffected controls (P ≤ .003) and in affected family members with an FECD grade of 4 or greater compared with unaffected family members (P ≤ .04). Similar results were observed for subjects without edema. Average CCT of index cases was greater than that of affected family members with grades 4, 5, and 6 FECD (P ≤ .02). Intraocular pressure was also associated with CCT (P = .01).

CONCLUSIONS

An increase in CCT occurs with increasing severity of FECD, including at lower FECD grades in which clinically observable edema is not present. Monitoring CCT changes serially could be a more sensitive measure of disease progression with surgical therapeutic implications.

Goldmann tonometry and pachymetry measures in patients with and without topical medical treatment at a glaucoma clinic

PURPOSE

To investigate, by audit, the intraocular pressure (IOP) and central corneal thickness (CCT) of patients attending a routine glaucoma clinic, in order to assess the potential effect of CCT on IOP measures.

METHODS

Data on current IOP (Goldmann), CCT (ultrasound) and glaucoma medications use were collected from 140 patients who presented for a follow-up visit over a 3-month period. Baseline IOP was retrieved from patient records.

RESULTS

The IOP was lower at follow-up, an expected effect of the use of IOP-lowering medications. However, the CCT was lower in medicated patients indicating, but not proving, that it changed in response to the lowering of IOP. Overall, the measured IOP was higher in patients with greater CCT values (p < 0.001) but this IOP-CCT relationship was most noticeable in patients with normal tension glaucoma and not obvious in those diagnosed with ocular hypertension. Overall, the slope of the IOP-CCT relationship was slightly steeper for those patients prescribed glaucoma medications.

CONCLUSIONS

In the routine assessment of glaucoma patients, corneal thickness can be shown to have an impact on applanation tonometry data. However, this effect may not be uniformly evident in patients with different types of glaucoma and may be different for patients under topical medical treatment.