APR 25, 2014
This study demonstrated that calculated glaucoma risk based on the available risk models can fluctuate significantly and should be interpreted with caution. A single risk calculation may not be sufficient for accurate risk assessment or informed decision-making.
Subjects included 27 untreated patients followed in a glaucoma referral practice for a minimum of 60 months (mean of 98.3 months). Age, central corneal thickness, IOP, vertical cup-to-disc ratio and visual field pattern standard deviation were used to calculate the five-year risk of conversion to POAG at baseline and at each follow-up visit.
The estimated five-year risk of conversion to POAG varied significantly during follow-up, with a trend toward increasing over time. Seven individuals (25.9 percent) converted to POAG.
For each patient, the mean risk of POAG conversion over a five-year period increased almost tenfold when comparing the best case scenario and worst case scenario (5.0 vs. 45.7 percent, P < 0.01).
The authors note that the subset of patients that converted to glaucoma did not have a statistically significant difference in risk of conversion at baseline compared with the subset that did not convert to glaucoma. The subset that did convert to glaucoma, however, did have a greater risk of conversion at follow-up visits and a greater change in risk over time. There was also a huge difference in the best case scenario risk compared to the worst case risk in both of the subsets.
I think this study nicely highlights that existing calculators can offer an improved quality of care by helping to aid treatment for our ocular hypertensive patients. However, one must exercise caution in determining this risk solely with baseline characteristics and in assuming that this risk is static. The determinants of risk and thus the risk of conversion are inherently fluctuant over time, and the initial risk of conversion to POAG can vary greatly during a patient’s follow-up. Furthermore, the assumed linear risk progression that most multivariate prediction models have is likely inaccurate as indicated by the greater increase in risk over time in patients who do convert to POAG.
The authors note that further refinement of the glaucoma prediction models in ocular hypertensive patients should account for variations in risk factor measurements over time.