TOP-VII: Robert N. Shaffer Lecture, AAO 2000
by Roger A. Hitchings.
"Glaucoma Management: what is the outcome of our treatment?"
Selected by the author
October 22-25, 2000, Dallas, USA
Topical b-blockers increase the relative risk of needing
asthma preparations by 2.5-3.0 (unpublished data)
FEV1 increases by 10-12% on switching from Timolol
to Betaxolol or epinephrine (Diggory's data)
20% of trabeculectomy patients show
³-2.0 myopic shift 12 months after surgery (Moorfields Eye Hospital data)
The chance of trabeculectomy "survival" after cataract
extraction is 60% at 2 years (Chens data)
One third of untreated NPG
patients do not have detectable visual field progression at 5
years (Moorfields Eye Hospital and Collaborative NTG study data)
25-30% IOP reduction is
needed to offer protection from progressive visual field loss in
NPG (Moorfields Eye Hospital and Collaborative NTG study data)
There is considerable scope for neuroprotection in NPG
The Ocular Hypertensive Treatment Study (OHTS)
confirmed the presence of thicker corneas in glaucoma suspects.
Corneal thickness > 600 microns was found in 26% of ocular
hypertensive subjects. Increased corneal thickness over estimates
applanation pressure readings and can falsely classify a patient as
having elevated intraocular pressure. This may account for a
large portion of glaucoma suspects who never demonstrate onset
of glaucomatous changes. More importantly, this finding
under estimates the true conversion rate from ocular hypertension
to open-angle glaucoma.
The OHTS investigators also found that
African-American subjects had corneas that were 25 microns thinner than
the other study races. Decreased corneal thickness under
estimates applanation pressure readings. This may partially account
for the higher incidence of open-angle glaucoma in this race.
Topical administration of the fixed combination of
latanoprost (0.005%) and timolol (0.5%) was effective in lowering
intraocular pressure. However, the added benefit of this combination
therapy was not convincingly presented.
Mitomycin-c for initial trabeculectomy in low-risk eyes is
associated with a high incidence of late complications
including hypotony (9%), bleb leak (14.5%), blebitis (4.9%), and
endophthalmitis (0.8%). These risks markedly lower the benefit
(low intraocular pressure) with the use of this antiproliferative
agent for initial filtration surgery.
Phase III studies with
AGN-192024 (Allergan) described as a "hypotensive lipid" (Lumigan®), is a very
effective ocular hypotensive agent. The difference and similarities
between Lumigan and other prostaglandin compounds has not been presented.
Viscocanalostomy is an effective procedure in Caucasians. However,
34% of eyes required a YAG and 22% eyes received 5-fluorouracil injections.
Bleb-associated endophthalmitis is associated with a
worse visual outcome than endophthalmitis after cataract
surgery. Twenty-seven of 34 eyes reported received
antiproliferative agents (23 eyes mitomycin-c) while five eyes had a
previous bleb leak. The most common organisms were
streptococcus and staphylococcus.
Moderate and severe sleep apnea syndrome is not a
glaucoma risk factor. Open-angle glaucoma was detected in only 2
of 143 (1.4%) patients with the syndrome, similar to the
expected occurrence in the studied age group. One patient was
known to have glaucoma and the second patient was a new diagnosis.
The uveoscleral pathway may
account for up to 50% of aqueous outflow in normal humans
and, when deficient, may be a significant contributor to elevated
intraocular pressure in glaucoma.
New genes have been
successfully inserted into the trabecular meshwork in a living
monkey, demonstrating that gene therapy for glaucoma may be possible.
Combination products consisting of two anti-glaucoma
medications in a single bottle may not be as effective as the
components given separately.
Short wavelength automated perimetry (blue-on-yellow
perimetry) may be able to detect damage to the visual field up to 5
years before traditional standard achromatic (white on white)
perimetry.
The presence of a disc hemorrhage, although not pathognomonic
for glaucoma, greatly increases the risk of disease progression.
Neuroprotection has been studied in a large number of
clinical trials for the treatment of a variety of neurological
disorders, such as stroke, but has yet to be proven effective.
Non-penetrating surgeries for glaucoma are increasing in
popularity, but long-term clinical trial data is lacking.
Two year follow-up of viscocanalostomy and
trabeculectomy revealed success rates (IOP < 21 mmHg, 20% decrease
in IOP, no medications required) of 76% and 92%, respectively.
Given the long-term complications of aggressive
adjunctive antifibrosis chemotherapy using mitomycin C,
consideration should be given to the use of intraoperative sponge
5-Fluorouracil during surgery in eyes not deemed at high surgical
risk of failure.
Early signs of bleb-related ocular infection, such as pain,
discharge, injection, and loss of vision, require immediate
attention if vision loss is to be prevented.
