Abstract
Purpose: :
To estimate the age of glaucoma disease onset, using visual field progression rate in a cohort of progressive normal tension glaucoma (NTG) subjects. We study the differences in clinical profiles, by analysis using the usual age of presentation/ age of diagnosis, versus analysis using this calculated age of disease onset.
Methods: :
NTG and field progression were defined according to the Collaborative NTG Study. One hundred and sixty-six eyes from 166 NTG subjects with field progression were recruited in this cross-sectional analysis of a prospective cohort. Patients were followed up for 36 months. The main outcome was the estimated age of onset of NTG from field progression rate. That was taken as the age when the mean deviation (MD) would have been zero decibel (dB). The same progression rate was used to estimate the degree of MD loss at 90 years old. Subjects were classified into 3 groups: group I (<40 years old), group II (40-59 years old), and group III (>60 years old), according to age of diagnosis and group A (<40 years old), group B (40-59 years old), and group B (>60 years old), according to calculated age of onset. Analysis of clinical profiles using these two definitions of age was made.
Results: :
In this study, 13.3% and 30.1% of subjects had calculated age of onset <40 years old and between 40-59 years old, respectively. On average, the NTG patients might have started their functional loss 13.7 years prior to being diagnosed. If untreated, by 90 years old, one-third of this progressive group will go into blindness (MD worse than -28 dB).While statistical analysis using age of disease presentation/ diagnosis was unable to demonstrate any significant clinical differences among groups I, II and III, the results changed when the calculated age of onset was employed: comparing groups A, B, and C, baseline MD (P=0.051) and pattern standard deviation (P=0.019) became significantly worse in patients with younger calculated age of onset. The mean number of systemic medical diseases (P=0.001), systemic hypertension (P=0.022) and ischemic heart disease (P=0.008) were significantly more in older calculated age of onset group.
Conclusions: :
Our results support the notion on screening for possible glaucoma from 40 years of age onwards. Further work on cost-effectiveness of such screening is warranted. The study suggested the importance of treatment for progressive NTG, as more than one-third may be blind by 90 years old. Statistical analysis using calculated age of onset may be helpful in uncovering potential risk factors not apparent using age of diagnosis/ presentation.
Clinical Trial: :
www.clinicaltrials.gov NCT00321386
Keywords: clinical (human) or epidemiologic studies: natural history • clinical (human) or epidemiologic studies: risk factor assessment