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Central corneal thickness associated with visual field progression
Researchers reported that thin central corneal thickness was associated with visual field progression in primary angle closure glaucoma in a study recently published in the Asia-Pacific Journal of Ophthalmology.
Tan and colleagues conducted a combined cross-sectional, prospective study of primary angle closure glaucoma (PACG) and primary angle closure (PAC) to assess any relationship between visual field progression and CCT.
Researchers used a microscopy SP-200P (Topcon Corp.) to measure CCT in the participants. The study included 105 total eyes: 35 eyes each for groups of normal control, PACG and PAC patients. Researchers divided the PACG and PAC patients into groups of thick and thin CCT. Participants received 12 to 18 months of follow-up analysis, which included visual field progression assessment with mean Advanced Glaucoma Intervention Study (AGIS) score.
Results showed that the control group had a CCT of 540 ± 27.8 µm, while the PACG and PAC groups were significantly thinner, at 509.7 ± 27.4 µm and 516.8 ± 26.0 µm, respectively. Researchers also reported a statistically significant increase of mean AGIS score during the follow-up of the thin CCT PACG group, but no significant increases in the thick CCT PACG group or either PAC groups.
"The PACG and PAC group had statistically significantly thinner mean CCT compared with the control group," the authors stated. "Thin CCT is associated with visual field progression based on the mean AGIS score in the PACG group, but not in the PAC group." – by Chelsea Frajerman Pardes
Disclosure: The authors reported no relevant financial disclosures.
Perspective
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The cornea has no known involvement in the pathogenesis of glaucoma. However, its biometry may hold clues about the propensity for disease progression, and its thickness plays a primary role in the accuracy of Goldmann applanation tonometry.
In this Malaysian study, primary angle closure (PAC) and primary angle closure glaucoma (PACG) patients more commonly had thinner central corneal thickness (CCT). Similar to reports on thin corneas in open-angle glaucoma, the authors also observed that PACG patients tended to have a more aggressive disease course. Although one might expect PACG patients to have thinner corneas, reflecting inherent structural weaknesses in the ocular tissues and underestimation of IOP, it is not intuitive that PAC patients would also have thinner CCT.
We continue to see evidence that open-angle glaucoma patients with thinner CCT may indicate a more aggressive disease course. This study suggests a similar stance should be taken for PACG.