OHTN Flashcards
OHTN
Statistically elevated IOP in the presence of an open angle on gonio and healthy optic nerves. The OHTS defined OHTN as an IOP 24-32mmHg. Clinically it is often classified as an IOP >22mmHg
OHTS study
Included patients with elevated IOP 24-32 with an open angle on gonio, a healthy ONH, and no VF defects
- patients were randomized into a treatment group (drops), and a control group. The target IOP for patietns in the treatment group was at least a 20% IPO reduction from baseline IOP and an IOP <24mmHg
- patients were followed for 5 years. The primary endpoint was progression to POAG, defined as glaucomatous damage to the ONH, glaucomatous VF defects or both
After 5 years, 9.6% of patients in the control group progressed to POAG, compared to 4.4% in the treatment group
Average CCT
473-597
What is the clinical average of CCT considered
555
Thicker CCT gives an ______ of IOP readings
Overestimation
Thinner CCTs give an _____ of IOP readings
Underestimation
CCT and glaucoma risk
OHTS concluded that thin pachs are an independent risk factors for he progression to POAG, even after controlling for the effect of CCT on IOP and other risk factors. Recall that it is no longer recommended to use a correction factor to determine the true IOP based on CCT, as the various proposed correction factors are unreliable; CCT should only be used to assign risk
High risk CCTs
<555
No change in risk on CCTs
555-588
Lower risk of POAG progression with CCTs
> 588
POAG risk: race
AA (as well as Hispanics and Latinos) have an increased prevalence compared to Europeans and caucasians
POAG and famHx
Positive famHx of POAG (first degree relative) increases the risk development of POAG by 3-4x
What is the most important risk factor of progression to POAG
Elevated IOP
- the only risk factor that can be treated
- as IOP increases, the risk of POAG also increases
Baltimore eye study
Followed patients with OHTN without treatment for 40 months and noted that 2.7% of patietns with an IOP 21-25mmHg, 12% of patients with an IOP 26-30mmHg, and 41.2% of patients with IOP >30mmHg developed POAG
Age of 90% of patients with POAG
> 55
Other potential risks for POAG
History of blunt trauma
Chronic use of systemic or topical ophthalmic steroids
Possibly myopia
P value of >5% on OCT
A p value >5% is assocaited with sectors marked as green on an OCT and indicates the thickness value is within the normal range for 95% of healthy patients in the population. A yellow sector is associated with a p value <5% but >1% and indicates the thickness value is normal for 1-5% of healthy patients in the population. A red sector is associated with a p value of <1% and indicates the thickness value is normal for less than 1% of the healthy patients in a population
Looking at red and yellow sectors on RNFL
Does not indicate that the patient has glaucoma. It indicates that the thickness value is normal in few healthy patients in the population. Always look at the optoc nerve rim tissue and the VF in addition to the OCT prior to making the diagnosis of glaucoma
HRT
Uses confocal scanning laser tomography to obtain a 3d image of the optic disc and the retina
GDx
Uses scanning laser polarimetry to measure the RNFL thickness
OCT
Uses optical coherence tomography to measure the RNFL thickness and macualr thickness
TSNIT pattern
Shows the RNFL thickness around the optic nerve. A normal TSNIT will have a double hump pattern, the shaded are of the map represents the range of the normative database
What quadrants are most important to look at on scans for glaucoma
S and I
ALT vs SLT
- ALT uses argon laser (same as PRP); SLT uses a selective frequency doubled Nd:YAG laser
- both ALT and SLT apply laser to the TM in order to lower IOP, although their proposed mechanisms differ: ALT causes scarring of the TM, causing tissue contraction that opens up the surrounding pores of the TM to improve AH outflow
- SLT stimulates the endothelial cell pumps and macrophages withi nthe TM to remove debris, resulting in an increase in AH outflow
- both have similar long term efficacy at controlling IOP, as well as similar side effects
- advantage of SLT of ALT is the repeatability of SLT due to reduced thermal damage to the TM compared to ALT
How does NTG differ from other glaucoma
- japanese
- IOP <24 (or less than 21)
- more likely to get a France hemorrhage
- paracentral VF defect
- progresses much slower, if at all
- much different risk factors and include vascular disorders (raynauds, sleep apnea)
IOP and NTG
Plays less of a role here than in POAG Other risks -vascular conditions -low blood pressure -sleep apnea -hypercoagulation
Most common VF defect in NTG
Paracentral
Optic neuropathy and NTG
Since IOP is in the normal range in NTG, it is important to consider other possible causes of optic neuropathy, especially in cases of suspected unilateral NTG. Additionally causes include hemorrhagic shock, MI, anemia, syphilis, vasculitis
Study question of OHTS
Does treating elevated IOP in a patient with OHTN decrease risk of progressing to POAG
Conclusion of OHTS
Treating patients with OHTN reduces the risk of progression to POAG by 5%
- the benefit of treatment is likely over-stated, as all patients who progressed to POAG based on glaucomatous optic nerve changes alone were asymptomatic, and even those patients that progressed based on VF defects were likely still asymptomatic
- certain patietns may have a higher rusk of progressing to POAG based on multiple risk factors. The decision to treat an individual patient with OHTN is multi-factorial; not all patients with OHTN require treatment. VF defects should be confirmed with consecutive fields to ensure true progression to POAG
EGPS study question
Does lowering IOP in patients with OHTN decreased the rare of progression to POAG
Conclusion of EGPS
Treatment of OHTN does not reduce the risk of progression to POAG. However, note that this study is poorly designed compared to the OHTS, as there was a high drop out rate, patients had thicker than average CCTs, only one IOP drop was used and no target IOP was set
EMGT study question
Should patients with newly diagnosed glaucoma be treated with IOP lowering drugs
Results of EMGT
45% of patients in the treatment group progressed compared to 62% on the control group
Risk factors to progression based on EMGT
Higher IOP (baseline and after treatment), bilateral disease, PXF, older age, and disc hemorrhages. For every 1mmHg of lowered IOP, there was a 10% reduction in risk of progression
Conclusion of EMGT
Lowering IOP reduces the risk of progression in the patients with early glaucoma. However almost half of the treated patients still progressed
CIGTS study question
Should patients with early (asymtaotmic) glaucoma (including pigmetnary and PXF) be initally treated with trab or with drops
Conclusion of CIGTS
Trab and drops are equally effective in the treatment of early OAG. Both should be soldiered as inital treatment options, although drops are often recommended first due to quality of life issues and lower risk of ocular complications, including cataracts
CNTGS study question
Does lowering IOP reduce the rate of progression in NTG
Conclusion of CNGTS
Treament is effective at reducing the risk of pression to NTG, but 2/3 of patietns with non fixation threatened NTG will not progress, even without treatment
AGIS study question
Should patients with advances glaucoma and inadequate IOP control on max therapy be treated with trab or ALT first
Conclusion of AGIS
The lower the IOP, the less risk of VF progression; a less important (but often quoted) conclusion is that ATT resulted in less VA loss in AA and TAT resulted in less VF loss in caucasians, however, the risk benefit ratio of each treatment should be considered for every patient, regardless of race
