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Editors Selection IGR 17-3
Clinical Forms of Glaucoma: NTG Progression to Blindness
Comment by Ki Ho Park on:
61017 Progression to Legal Blindness in Patients With Normal Tension Glaucoma: Hospital-Based Study, Sawada A; Rivera JA; Takagi D et al., Investigative Ophthalmology and Visual Science, 2015; 56: 3635-3641
The authors evaluated the probability of normal tension glaucoma (NTG) progressing to legal blindness under standard ophthalmic care after a retrospective analysis of 382 NTG patients with a mean follow-up period of 13 years. Upon final examination, 34 patients had progressed to unilateral blindness and five to bilateral blindness. Thus, the probability of patients with NTG progressing to unilateral blindness was 5.8% at ten years and 9.9% at 20 years; that for bilateral blindness was 0.3% at ten years and 1.4% at 20 years. A lower initial best-corrected visual acuity (BCVA), a worse AGIS score, and the frequency of glaucoma-medication change during the follow-up period were significantly correlated with the development of blindness in at least one eye. The frequency of glaucoma-medication change might not be a cause of blindness but seems, rather, to be an epiphenomenon related to the medications prescribed during the disease-worsening period.
Special care should be taken to follow-up on NTG patients, especially those with worse best-corrected visual accuity and more advanced visual field loss at diagnosis
As for the study's strengths, a large number of NTG patients from one institute were followed-up on over a long duration. Also, the study provides an important reference even though the probability of blindness in eyes with NTG is much lower than previously reported in patients with high-tension glaucoma.
The major limitation of this study is the large proportion of patients lost during the initial follow-up period. This seems an important but inevitable issue in a study performed retrospectively. Another issue, not mentioned in the paper, was the lack of information on the degree of cataract, which could have affected visual acuity and the probability of blindness as well.
These issues notwithstanding, the study offers a clinically important message, which is that doctors should exercise caution with respect to their NTG prognoses when the patient shows low BCVA and advanced visual field loss at diagnosis.
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