Perimetric severity in hospital‐based and population‐based glaucoma patients

Abstract

Background:  The aim was to compare the severity of glaucoma among newly diagnosed patients presenting to a hospital‐based glaucoma care centre (HBGS: Sankara Nethralaya, Medical Research Foundation) with that of age matched subjects from the population‐based Chennai Glaucoma Follow‐up Study (CGFS).

Methods:  Newly diagnosed subjects with primary glaucoma from HBGS and age‐ and gender‐matched subjects from the urban arm of CGFS examined during the same time period were included. All subjects underwent comprehensive ocular examinations including Humphrey visual field (HVF: 24‐2 SITA Standard). Glaucoma was defined as: an intraocular pressure (IOP) of 22 or greater mmHg in either eye; vertical cup‐to‐disc ratio (VCDR) of 0.7 or greater or asymmetry 0.2 or more or the presence of focal thinning, notching or a splinter haemorrhage. All subjects had a minimum of three follow‐up visits and reliable visual fields. The IOP, vertical cup‐to‐disc ratio, mean deviation (MD) and pattern standard deviation (PSD) of the Humphrey field measurements at the third follow‐up visit of CGFS were compared for assessing the severity of glaucoma with the HBGS group.

Results:  Forty‐seven age‐matched subjects from both the study populations were selected. Significantly higher (p = 0.04) IOP was noted in the HBGS population than the CGFS, with a difference in mean IOP of 2.80 mmHg (95% CI of diff: 0.14 to 5.46). The mean ± SD of the mean deviation and pattern standard deviation were ‐6.92 ± 6.53 dB and 6.05 ± 4.20 dB among the HBGS and ‐4.47 ± 4.19 dB and 3.26 ± 2.69 dB among the CGFS population, respectively, the difference in the mean deviation (p = 0.036) and pattern standard deviation (p = 0.0001) were statistically significant. The mean vertical cup‐to‐disc ratio did not vary between populations (p = 0.14).

Conclusion:  Patients from the HBGS group had higher IOP and more severe visual field defects than the CGFS group. Hence, results from hospital‐based studies on severity and the rates of progression should be interpreted with caution.

Key words:

• glaucoma
• hospital‐based study
• population‐based study
• visual fields

ACKNOWLEDGEMENT

The authors thank Ms PS Deepika, Birla Institute of Technology and Science, Pilani, India, for helping us conduct the study.