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Conjunctiva thinner in patients with normal tension glaucoma than POAG
Researchers discovered an additional feature in the pattern of thinner ocular structures in patients with normal tension glaucoma: the conjunctiva is thinner than in those with primary open-angle glaucoma.
Van Ginderdeuren and colleagues included in their study 54 patients who were scheduled for trabeculectomy. Sixteen patients were considered to have normal tension glaucoma (NTG) because their intraocular pressures were 21 mm Hg or less, and 38 patients were considered to have high tension primary open-angle glaucoma (POAG) because their IOPs were greater than 21 mm Hg.
The mean stromal conjunctival thickness in patients with NTG was 64 ± 31 µm and in patients with POAG was 103 ± 44 µm, according to the study. The mean central corneal thickness (CCT) in patients with NTG was 546 ± 35 µm and with POAG was 548 ± 38 µm.
After pooling all patients, researchers found that stromal CT correlated positively with the maximum untreated IOP but not with CCT, age, number of medications, duration of therapy or severity of the visual field defects.
Van Ginderdeuren and colleagues stated that it is known that NTG patients can have a lower CCT.
“Thinner conjunctiva in patients with NTG can have implications on the complication rate after surgery; a thinner conjunctiva is more apt to tears and leakage after trabeculectomy with higher risk of blebitis and endophthalmitis,” they concluded. – by Abigail Sutton
Disclosure: The researchers reported no relevant financial disclosures.
Perspective
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Over the years, clinicians have increasingly become aware of the importance of risk factors other than intraocular pressure in patients with normal tension glaucoma (NTG). Gradually, scientists and clinicians are discovering both physiological and structural abnormalities that may leave certain patients susceptible to developing glaucoma despite statistically normal IOP.
This study adds to that knowledge base by confirming that the conjunctiva is thinner in patients with NTG. Although clinically this finding is unlikely to change our management, it contributes toward building a biometric profile for patients who have NTG.
With the ever-evolving field of genetic research, it will be interesting to see if such NTG phenotypes will be traced back to specific genes in the future.