Congenital Glaucoma: Are We Operating Prematurely?
The instinct is to act early to save vision – but at what cost?
Nader Bayoumi |
Glaucoma in children is a disaster waiting to happen. If undetected for too long or inadequately treated, the inevitable fate is blindness. In children, treatment is almost always surgical and there are many options, including angle surgery, filtration surgery (or a combination of the two), drainage device placement and cyclodestructive procedures. But inadequate treatment – just like no treatment – results in a relentless progression towards total vision loss. The visual deterioration is multifactorial and can be attributed to corneal pathology (progressive enlargement, edema and scarring), refractive error (myopic shift) and most importantly, optic nerve cupping attributed initially to posterior laminar bowing (which is reversible) and later neuronal damage (which is irreversible). Fortunately, timely successful surgery results can reverse many of these changes. The consensus is that the best chance is the first chance, and that each subsequent procedure has progressively lower success rates. Hence, maximizing the chance of a successful initial procedure is of utmost importance.
Most of us were taught that we should operate on pediatric glaucoma cases as early as possible – which means some procedures are performed on children only a few days old. But operating on very young children presents issues. Glaucoma diagnosis is not always clear at such an early age because it is very difficult to accurately measure IOP given the very narrow palpebral fissures present in very young children. Opening such small eyes almost invariably applies pressure to the globe, resulting in artefactually and artificially high IOP measurements. Additionally, cloudy corneas in such young patients are not always related to elevated IOP; many clear spontaneously with time. Further, a hasty decision to operate without waiting to perform further examinations does not allow us to establish whether the disease is progressive in nature. And then there are other issues related to the operative procedure itself; first, it’s technically difficult (through a very narrow palpebral fissure) and second, filtration surgery has a very high chance of failure because of the aggressive healing response in infants – the tendency to fibrose is inversely proportional to age.
But... How long could and should you postpone surgery for glaucoma in young infants? In my practice, we recommend two months. This is tempered by the clinical scenario: two months would not cause much optic cupping – or any deterioration that cannot be reversed if the subsequent surgery was successful, plus corneal edema would not result in any permanent scarring over this short period. Waiting also gives time for the palpebral fissure to grow, making IOP measurement more accurate (as well as diagnosis and evaluation) and surgery far easier to perform. And if the cornea is cloudy from a cause other than elevated IOP, there is time for spontaneous clearing to occur. The final advantage of waiting is that the healing response gets less aggressive with time, improving chances of filtration surgery success. So the surgeon’s dilemma is this: perform a hasty, technically difficult operation with an extremely low chance of success, with a potentially doubtful diagnosis… or wait for a 60-day delay that brings with it a solid diagnosis, makes the procedure technically easier to perform and has a higher success rate, plus the eventual reversal of almost all possible pathological changes induced by the disease. I strongly believe that the second option is the right one, and that’s why, in my practice, the minimum age for operation on children with glaucoma is currently two months.