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Higher IOP risk for development of visual field defects
Researchers found that worse initial pattern standard deviation, disc hemorrhages and higher mean intraocular pressure were associated with the eventual development of a visual field defect.
According to a study in the British Journal of Ophthalmology, the retrospective hospital-based analysis included 130 eyes of 130 patients diagnosed with preperimetric normal tension glaucoma who were followed for 5 years.
The average age at diagnosis was 52.6 years, and there were 50 men and 80 women.
During the follow-up period, 21 eyes underwent cataract surgery, and two eyes eventually received filtering surgery.
Seventy-one eyes (54.6%) developed a glaucomatous visual field defect (VFD) during the follow-up. The average time to development of a VFD was 7 years.
Researchers determined that having a greater initial pattern, the presence of optic disc hemorrhage and higher mean IOP prior to developing a VFD was related to developing a VFD.
They found that a glaucomatous VFD developed in 21.5% at 5 years, 40.0% at 10 years, 58.6% at 15 years and 70.5% at 20 years.
“Our findings suggest that care should be taken to sustain regular ophthalmic examinations because some normotensive preperimetric glaucoma cases progress comparatively rapidly,” researchers wrote. – by Abigail Sutton
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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“Normal tension glaucoma” has long been a bit of a conundrum, going from being nonexistent when the definition of glaucoma required elevated intraocular pressure, to common, representing up to 90% of diagnoses in some populations.
Although normal tension glaucoma often progresses slowly (as noted in landmark trials including the Collaborative Normal Tension Glaucoma Study and Early Manifest Glaucoma Trial), presenting visual field defects can be deep and threaten fixation, part of the definition of advanced glaucoma.
Sawada and colleagues’ retrospective analysis reinforces several important concepts:
--Higher IOP, even if statistically normal, is a risk factor for glaucomatous optic neuropathy;
--Disc hemorrhages may be the single most important risk factor for disease progression; and
--Rates of progression are extremely variable between patients and through follow-up of individual patients.
While this study defined manifest glaucoma based upon 30-2 abnormalities, we now recognize that initial paracentral defects are common and may go undetected with the 24- or 30-2 grid. It follows that our ancillary testing should include ganglion cell and 10-2 analyses, ideally for all patients but definitely in the presence of lower IOP, disc hemorrhage, systemic hypotension or signs of vascular dysregulation (migraine, Raynaud’s, sleep apnea). When viewed through the correct lens, progression may prove to be more common than we think.