Glaucoma is generally the result of a sustained increase of IOP. However, there are several types of Glaucoma one of which being Normal Tension Glaucoma where you guessed it the IOP is within what is classified as the “normal IOP range” but your optic nerve is still being damaged. This damage to the optic nerve can be the result of a higher ICP that puts pressure on the back side of your eyeball and damages the fibres of the optic nerve. Even though the IOP is WNL this IOP is too high for people that suffer with NTG.
Open angle glaucoma occurs when the drainage network of your eyes is working fine but is unable to keep up with the natural production of fluid, aqueous humour, within your eyes. This loss of equilibrium leads to a gradual increase in IOP over time that damages your optic nerve due to the increasing stress of a higher IOP.
Closed angle glaucoma occurs when the drainage network becomes clogged or shuts down resulting in an increased IOP as the regular aqueous fluid produced has less area to drain out of your eyes. This leads to an increased IOP which in turn damages your optic nerve.
An angle closure attack occurs when the drainage network is blocked by a mid-dilated pupil typically affecting long-sighted individuals. An angle closure attack causes a rapid increase in IOP which gives a steamy cornea, a very red & painful eye with the individual suffering from intense symptoms of pain, nausea, & light sensitivity. This attack requires immediate treatment to rapidly reduce the IOP and alleviate the sufferer’s symptoms. Typically, preventative treatment is administered to the fellow eye as a precaution and the individual is advised to see an eye specialist for IOL & PI procedures for both eyes.
PXF: Pseudoexfolitian glaucoma is the result of dandruff like material sloughing of the surface of an individual’s intra-ocular lens surface. This PXM is created by the back surface of the iris rubbing across the front surface of the intra-ocular lens. The PXM then accumulates in the pores of the drainage network of your eyes and leads to an elevated intra-ocular pressure.
PDS: Pigment dispersion syndrome is the result of a floppy iris. The Iris of these individuals is larger than what it should ideally be. The excessive surface area of the iris rubs on the ciliary processes (which connect to the intra-ocular lens) causing iris pigment to become displaced and float around in the convection currents within your eyes. Over time this loose pigment blocks the pores of the drainage network and leads to an increased IOP within your eyes.
Traumatic glaucoma typically results 10 years after a traumatic injury has affected an eye. Individuals who have sustained a traumatic injury to one or both of their eyes should be advised on the high likelihood of delayed onset glaucoma as the damage sustained to the drainage network typically from an angle recession leads to an elevated IOP and optic nerve damage.
Diabetic glaucoma can occur secondary to poorly controlled diabetes. Diabetes affects your eyes via new blood vessel growth in response to a reduced or poor oxygen supply to your eyes. Any new blood vessels that grow in your eyes are fragile and leak quite often. These leaking blood vessels create a damaging cycle of further reductions in oxygen supply for your eyes and further new blood vessel growth. These new blood vessels can then grow into and as a result close the drainage network via a “zippering” action. This leads to an elevated IOP and very poor prognosis for your eyes as the zippering shut of the drainage network cannot be reversed.
Regular eye health reviews can prevent many complications associated with all forms of glaucoma. During a regular eye examination, your Optometrist will check the IOPs and examine the health of the optic nerve heads for each of your eyes.
If you have a family history of glaucoma you should have a review of your IOPs and eye health at least every 12months or sooner. The timeframe for reviews is dependent on your IOP, your optic nerve health, your visual fields tests (test for the peripheral vision of each eye), and your family history. Your optometrist will advise you on the appropriate time frame for your regular reviews.
If a higher than average IOP is found during your routine examination, you may be asked to return for IOP phasing – checking your IOP range throughout the day. You would also be asked to return for baseline visual fields testing if this could not be arranged on the same day. If your optic nerve head examinations reveal signs of damage consistent with glaucoma you will be started on a pressure reducing eye drop typically used once a day and reviewed again in 2 weeks’ time – to have your IOPs re-measured to ensure the pressure reducing eye drops are doing what they are intended to do. If the drops are working as planned and have dropped your IOPs back down into the “ideal IOP range” you would then be reviewed again typically in 2-3 months’ time.
Regular reviews should then be carried out to ensure your IOPs are maintained in the target range, your optic nerves are not suffering from further damage, and that your visual fields tests are stable. If changes are found for any of the aforementioned then your treatment plan will be changed.
Below is a great video from Glaucoma Australia
Adam Maher
Optometrist
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