Glaucoma medications that reduce aqueous production β blockers α2 adrenergic agonists carbonic anhydrase inhibitors
“Discussion” points for every glaucoma patient: “controlling a risk factor (high eye pressure) for glaucoma” “in hopes to prevent vision loss” “no guarantee that vision loss will not occur” “like controlling (blood pressure) a risk factor for heart attack and stroke”
Glaucoma standard of care dilation with retinal biomiscropy Goldmann tonometry visual fields gonioscopy pachymetry photography (debatable) OCT/GDx/HRT
OHTS goals of study Ocular Hypertension Treatment Study Evaluate safety / efficacy of topical glaucoma medications to prevent or delay congenital open angle glaucoma (COAG) in patients with high IOP identify baseline demographic and clinical factors predict which patients will develop COAG
Ocular Hypertension Treatment Study (OHTS) OHTS Enrollees patients with: – high IOP – normal visual fields (VF) – normal discs patient randomly assigned to medical treatment or observation patient monitored: – VF q 6 months – fundus photos q year – endpoint of COAG: VF evidence disc evidence or both VF and disc evidence
Ocular Hypertension Treatment Study (OHTS) OHTS results COAG patients: – 55% diagnosed via disc changes without VF changes – 20% reduction in IOP decreased incidence of COAG by 50% at 5 years – black people developed COAG at significantly higher rate
Ocular Hypertension Treatment Study (OHTS) OHTS Important risk factors for glacomatous damage in ocular hypertensives higher IOP old age large C/D greater pattern standard deviation thin central cornea thickness (CCT)
Ocular Hypertension Treatment Study (OHTS) OHTS central corneal thickness (CCT) findings patients with CCT less than 555 are 3x more likely to develop POAG Much bigger risk factor than: – race – family history – refractive error – general health Recommendation: pachymetry as standard part of evaluation of ocular hypertensive patients.
Ocular Hypertension Treatment Study (OHTS) OHTS Guidelines IOP: – 23.75 or below low risk – 23.75 < IOP < 25.75 moderate risk – above 25.75 high risk CCT (pachymetry): – above 588 low risk – 555 < CCT < 588 moderate risk – 555 or below high risk vertical C/D – 0.3 or less low risk – 0.3 < C/D < 0.5 moderate risk – 0.5 or above high risk
In glaucoma, NFL damage precedes… field loss and disc changes 5 year, 50% “rule” 50% of NFL is lost before a VF will reveal a defect. “we are in the business of preventing any vision loss”
Instruments commonly used to manage patients with glaucoma HRT2 – Heidelbert Retinal Tomograph Stratus OCT – Optical Coherence Tomography from Zeiss Humphrey GDx-VCC nerve fiber analyzer (with variable corneal compensator from Laser Diagnostic Technologies)
HRT, OCT, GDx factoids image the optic disc and/or retinal NFL each has strengths & weaknesses useful for glaucoma suspects moderate glaucoma patients NOT helpful for advanced glaucoma patients cost: HRT < GDx < OCT
Optic nerve imaging considerations imaging reimbursable at least once a year, HOWEVER, cannot be reimbursed for fundus photos & imaging on same day. results need to be used within a larger clinical context! – ONH tissue, VF defects and imaging should all correlate & “make sense”
HRT strengths & “considerations” The HRT utilizes confocal scanning laser ophthalmoscopy Strengths – shows topography of optic nerve – detects patient progression – confirms nerve size – evaluates cupping “Considerations” – accuracy depends on drawing contour line correctly the first time. – probably not the best for assessing thickness of RNFL
OCT strengths & “considerations” OCT uses optical back scattering of light to compute tomographic images based on amount of incident light reflected by tissue. Strengths – accurately measures RNFL thickness – correlates highly with VF loss & disc damage – reproducible – image quality monitored during test – awesome for macular holes, edema CNV mgmt – reason why less fewer FLANs done at UMSL “Considerations” – automatically generated disc contour lies can be somewhat inaccurate – does not determine progression – difficult to determine how much change is clinically significant – requires dilated pupil, minimal media opacity
GDx strengths & “considerations” GDx uses a scanning laser polarimeter Strengths – measures RNFL – very reliable – portable – can do undilated – media opacities least likely to interfere Considerations – image quality cannot be measured during test
GDx NFL analysis Gives ‘NFI’ number: – 0—30 normal, low probability of glaucoma – 31—70 glaucoma suspect – 71—100 high probability of glaucoma The NFI number does NOT indicate severity or progression of glaucoma.
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