Glaucoma causes progressive, chronic damage to the optic nerve called glaucomatous optic neuropathy, in which eye pressure and other unknown factors (including nearsightedness and family history), contribute to the damage. Again, it is caused by absolute or relative (i.e., higher than ideal for the patient) high eye pressure. So, if the ideal or target pressure is 11, but the current pressure is 18, it is still in the normal range but too high for the patient. Progressive damage to the optic nerve and optic nerve function is the hallmark of uncontrolled glaucoma. Control is achieved when all the parameters are stable and show no progression. Thus, 1) timely optic nerve evaluation; 2) establishing an ideal target pressure; and, 3) demonstration of stability is the standard of care for glaucoma management. The failure to do each represents deviations from requisite standard of care.
Optic nerve evaluation is done by:
1) clinically looking at the optic nerve and the cup/disc (C/D) ratio. The higher the C/D ratio or the greater the asymmetry (it is expected that the difference between the two eyes would be < 0.2), the greater the likelihood of glaucoma or glaucoma progression;
2) visual field testing (which picks up abnormalities but not until possibly 50% of the optic nerve layer has already been damaged thus suggesting with the earliest findings that there is already mild to moderate disease; and,
3) measuring the nerve thickness with the GDx or OCT (noted before) which may be more sensitive in identifying early optic nerve damage, but not showing the actual effect on visual field (peripheral and central vision).
Optic nerve preservation medical expert witness specialities include neuro ophthalmology and ophthalmology.