The thick and thin of the central corneal thickness in glaucoma

Central corneal thickness (CCT) is an important parameter in the assessment of any potential glaucoma patient. While it affects prognosis in ocular hypertension, its value in patients diagnosed with glaucoma is less certain. There are several biological factors and genetic components that may influence glaucoma progression, which have been associated with thinner CCT. The CCT itself can be affected by several factors including ethnicity, age, sex, glaucoma medications, genetics, and the subtype of glaucoma. Besides, there is variability in the measurement of CCT between difference types of devices. These factors need to be considered in the evaluation of glaucoma patients' CCT and its effect on interpretation of intraocular pressure levels and risk stratification.

Central corneal thickness in glaucoma

PURPOSE OF REVIEW

The purpose of this review is to summarize the role of central corneal thickness (CCT) in the clinical management of a glaucoma patient.

RECENT FINDINGS

The prognostic value of CCT is well recognized in patients with ocular hypertension. However, its predictive value in other glaucoma suspects and patients with established glaucoma is less certain. Tonometry artefacts can result from variations in CCT. However, an adequately validated correction algorithm for Goldmann applanation tonometry measurements does not exist. Newer methods of tonometry are potentially less influenced by CCT but are limited in their clinical use. There may also be biological and genetic associations between corneal thickness and glaucoma. Demographics, environmental factors, glaucoma treatment and the measurement device used have a significant influence on CCT, and should be considered when interpreting the effect of cornea thickness in patients with glaucoma. New measurements of the biomechanical properties of the cornea are likely to be better approximations of the globe biomechanics than CCT, but these require further evaluation.

SUMMARY

The clinical significance of CCT is well recognized in the context of glaucoma diagnosis and management, though the extent of its importance remains debatable. Corneal biomechanical properties may be more significantly associated with glaucoma than CCT.

Effect of obstructive sleep apnea syndrome on corneal thickness

Obstructive sleep apnea syndrome (OSAS) might be a risk factor for the development of eye disorders. The aim of the study was to evaluate the effect of OSAS on central corneal thickness (CCT). A total of 195 patients were enrolled in the study, and underwent polysomnography. Patients were divided according to their apnea-hypopnea index (AHI) scores into control group (AHI < 5), mild (AHI, 5-15), moderate (AHI, 15-30), and severe OSAS (AHI > 30) groups. In ophthalmological examinations, CCT, auto refractometer measurement, tear break-up time, and Schrimer's test results were evaluated. Central corneal thickness was significantly decreased in patients with OSAS compared to the control group (542.14 ± 31.21 vs. 569.92 ± 13.46, p < 0.001). As the severity of OSAS increased, CCT decreased (mild OSAS = 567.48 ± 23 mm, moderate OSAS = 530.21 ± 30.2 mm, and severe OSAS = 557.97 ± 16.52 mm, respectively, p < 0.001). The mean values of auto refractometer, tear break-up time, and Schrimer's test were similar between the groups (p > 0.05). CCT was negatively correlated with AHI, oxygen desaturation index, desaturation percentages, and positively correlated with minimum oxygen saturation values (p < 0.05). This study showed that central corneal thickness is inversely correlated with the severity of OSAS. OSAS affects all organ systems particularly cardiovascular and neurological mechanisms. Further studies are warranted to evaluate the effect of OSAS treatment on CCT.