Jacob Bell
New Member
APRIL 1976 Vol. 15/4
Products of the Cannabis sativa plant
and its close relatives are used throughout
the world to make hashish and marihuana.
The physiologically active compounds in
these products have been identified as
tetrahydrocannabinols (THC). The specific
chemical is not clear since A9-THC is produced
only in an acidic environment.1 Reports
by the Secretary of Health, Education,
and Welfare have been made to Congress
annually since 1971 and include much
of the data available on use and the medical
aspects of consumption.2 One federal
report of the Senate Committee on the
Judiciary; estimated that in 1973 there were
25,000,000 users.3 Of this group 10 per cent
used cannabis more than six times per
week. Based on trends from federal seizures
the use doubling time was 1.54 years.
In 1973, about 790,000 pounds of marihuana
and 50,000 pounds of hashish were
seized in the United States. These publications
establish that there is a wide variance
of use based on geographic region and
socioeconomic variables. Although information
relative to eye toxicity of THC is
modest, because of space limitations only
a few reports can be described. These
range from "case study" material to elaborately
controlled research papers.
Shapiro4 reported his observations on
350 patients who were cannabis users. All
presented with vague eye complaints. Several
consistent effects included: (1) decreased
intraocular pressure; (2) photophobia
and blepharospasm; (3) ciliary
(mixed) injection of the globe; (4) increased
visibility of the corneal nerves,
and (5) accomodative or refractive
changes. All of these effects were reversible.
Similar findings were reported by
Valk,5 who studied the eye signs over a
period of weeks in five young users (aged
17 to 24). All had normal acuity. All presented
pupillary abnormalities (static) with
pupillary reactions ranging from the completely
paradoxical to hardly reactive. All
showed reduced accomodation (range 2.5 to
5 diopters; normal 7 to 11 diopters). Three
had conjunctival injection, two of these had
iritis. Two had red optic discs and three
saw spots during the Amsler test.
Moskowitz, Shania, and Schapero,6 compared
visual function in 12 male college
students after consumption of a placebo,
310 micrograms A°-THC per kilogram of
body weight (oral) or 0.69 G. ethyl alcohol
per kilogram. No differences were
found in dark adaption time to a mesopic
level, static ("grating") acuity, vertical
phoria, supraduction, infraduction, or adduction.
Alcohol and marihuana produced
moderately debilitating effects on lateral
phoria and abduction. These were statistically
significant from the placebo effects.
Both lacrimation and intraocular pressure
are sharply reduced after smoking
marihuana.7 Hepler, Frank, and Ungerleider8
found IOP decreases up to 45 per
cent in nine of eleven subjects after 30
minutes of smoking. Pupillary diameter decreased
by about 0.4 mm. in five minutes
during smoking and there were extensive
increases in conjunctival injections. But
Flom, Adams, and Jones9 were able to repeat
the intraocular pressure reduction
findings only in subjects who were only
slightly to moderately experienced with
marihuana use and who experienced a
subjective "high" and relaxation. Individuals
in their sample who used marihuana
most, showed no or little intraocular pressure
drop. Pharmacologically the mechanism
by which marihuana affects intraocular
pressure is not clear. Green and
Pederson10 found decreased fluid secretion
and increased ultrafiltration when THC
was applied directly to the isolated ciliary
body of the rabbit. Flom, Adams, and
Jones9 conclude the effect of the THC may
not be direct in human users, but secondary
to the relaxation and general subjective
state. Conjunctival injection and other
variables were not discussed by these
authors.
The physiological and subjective effects
of brief smoking (10 minutes) are of
limited duration. Pulse rate peaks in about
10 minutes and is near the baseline after
three hours. Intraocular pressure mean decrease
is maximum in about 60 minutes
and subjective "high" peaks at about 30
minutes.9 Pupillary constriction peaked at
five minutes.s Clearance of A9THC from
human systemic circulation was not complete
for about three days after intravenous
injection.11
Findings relating to the chronic use of
cannabis are much more limited than
those on acute use. A recent report on
visual and ophthalmic effects after 10
years of use compared 39 users and
matched controls with equal cigarette
(tobacco) consumption.12 Although differences
of statistical validity were found
between users and controls none of the
differences were so large that pathology
could be inferred. Measures were reported
on pupil size and responsiveness, intraocular
pressure, dark adaptation, acuity,
color matching, lacrimation, fundus, and
conjunctival injection. The users were not
intoxicated during testing. Of particular
interest are the results on intraocular pressure,
pupil response, and conjunctival injection.
Intraocular pressure was found to
be slightly (0.7 mm. Hg) greater in users.
Pupil size and responsiveness was not
measurably different between groups, and
16 of the users were judged to have conjunctival
injection compared to 13 of the
nonusers.
An overview of this literature indicates
that there are numerous and complex effects
of THC on vision and the eye. These
vary with dose and with the individual experience
with the drug. The majority of
eye effects seem to be confined to the anterior
segment and in some ways mimic an
irritative process of that region. These effects
are transient and seem to produce no
cumulative effects of long term clinical
significance.
William W. Dawson
Departments of Ophthalmology
and Physiology
College of Medicine
University of Florida
Gainesville, Fla. 32610
REFERENCES
1. Quarles, W., Ellman, G., and Jones, R.:
Toxicology of marijuana: conditions of conversion
of cannabidiol to THC upon smoking,
Clin. Toxicol. 6: 211, 1973.
2. "Marihuana and Health": Reports to Congress
from the Secretary Health, Education,
and Welfare, 1971-1975. United States
Government Printing Office.
3. "Marihuana-Hashish Epidemic and its Impact
on United States Security." Hearings
before the Judiciary Committee. United
States Government Printing Office, 1974.
4. Shapiro, D.: The ocular manifestations of
the cannibinols, Ophthalmologica 168: 366,
1974.
5. Valk, I,.: Hemp in connection with ophthalmology,
Ophthalmologica 167: 413, 1973.
6. Moskowitz, H., Shania, S., and Schapero,
M.: A comparison of the effects of marijuana
and alcohol on visual functions. Current Research
in Marihuana, In: Lewis, M., editor.
New York, 1972, Academic Press, pp. 129-
150.
7. Hepler, R., and Frank, I.: Marijuana smoking
and intraocular pressure, J.A.M.A. 217:
1392, 1971.
8. Hepler, R., Frank, I., and Ungerleider, J.:
Pupillary constriction after marijuana smoking,
Am. J. Ophthalmol. 74: 1185, 1972.
9. Flom, M., Adams, A., and Jones, R.: Marijuana
smoking and reduced pressure in human
eyes: drug action or epiphenomenon?
INVEST. OPHTHALMOL. 14: 52, 1975.
10. Green, K., and Pederson, J.: Effect of Ao
tetrahydrocannabinol in aqueous dynamics
and ciliary body permeability in the rabbit,
Exp. Eye Res. 15: 499, 1973.
11. Lemberger, L.: Tetrahydrocannabinol metabolism
in man, Drug Metabolism and Disposition
1: 461, 1973.
12. Carter, W., and Coggins, W., editor: A
Study of the Effect of Chronic Smoking
Cannabis in Costa Rica. Final report contract
HSM-42-73-233 (ND) to National
Institute on Drug Abuse, United States
Public Health Service, Feb. 1, 1976.
Source: Investigative Ophthalmology: Cannabis And Eye Function
Products of the Cannabis sativa plant
and its close relatives are used throughout
the world to make hashish and marihuana.
The physiologically active compounds in
these products have been identified as
tetrahydrocannabinols (THC). The specific
chemical is not clear since A9-THC is produced
only in an acidic environment.1 Reports
by the Secretary of Health, Education,
and Welfare have been made to Congress
annually since 1971 and include much
of the data available on use and the medical
aspects of consumption.2 One federal
report of the Senate Committee on the
Judiciary; estimated that in 1973 there were
25,000,000 users.3 Of this group 10 per cent
used cannabis more than six times per
week. Based on trends from federal seizures
the use doubling time was 1.54 years.
In 1973, about 790,000 pounds of marihuana
and 50,000 pounds of hashish were
seized in the United States. These publications
establish that there is a wide variance
of use based on geographic region and
socioeconomic variables. Although information
relative to eye toxicity of THC is
modest, because of space limitations only
a few reports can be described. These
range from "case study" material to elaborately
controlled research papers.
Shapiro4 reported his observations on
350 patients who were cannabis users. All
presented with vague eye complaints. Several
consistent effects included: (1) decreased
intraocular pressure; (2) photophobia
and blepharospasm; (3) ciliary
(mixed) injection of the globe; (4) increased
visibility of the corneal nerves,
and (5) accomodative or refractive
changes. All of these effects were reversible.
Similar findings were reported by
Valk,5 who studied the eye signs over a
period of weeks in five young users (aged
17 to 24). All had normal acuity. All presented
pupillary abnormalities (static) with
pupillary reactions ranging from the completely
paradoxical to hardly reactive. All
showed reduced accomodation (range 2.5 to
5 diopters; normal 7 to 11 diopters). Three
had conjunctival injection, two of these had
iritis. Two had red optic discs and three
saw spots during the Amsler test.
Moskowitz, Shania, and Schapero,6 compared
visual function in 12 male college
students after consumption of a placebo,
310 micrograms A°-THC per kilogram of
body weight (oral) or 0.69 G. ethyl alcohol
per kilogram. No differences were
found in dark adaption time to a mesopic
level, static ("grating") acuity, vertical
phoria, supraduction, infraduction, or adduction.
Alcohol and marihuana produced
moderately debilitating effects on lateral
phoria and abduction. These were statistically
significant from the placebo effects.
Both lacrimation and intraocular pressure
are sharply reduced after smoking
marihuana.7 Hepler, Frank, and Ungerleider8
found IOP decreases up to 45 per
cent in nine of eleven subjects after 30
minutes of smoking. Pupillary diameter decreased
by about 0.4 mm. in five minutes
during smoking and there were extensive
increases in conjunctival injections. But
Flom, Adams, and Jones9 were able to repeat
the intraocular pressure reduction
findings only in subjects who were only
slightly to moderately experienced with
marihuana use and who experienced a
subjective "high" and relaxation. Individuals
in their sample who used marihuana
most, showed no or little intraocular pressure
drop. Pharmacologically the mechanism
by which marihuana affects intraocular
pressure is not clear. Green and
Pederson10 found decreased fluid secretion
and increased ultrafiltration when THC
was applied directly to the isolated ciliary
body of the rabbit. Flom, Adams, and
Jones9 conclude the effect of the THC may
not be direct in human users, but secondary
to the relaxation and general subjective
state. Conjunctival injection and other
variables were not discussed by these
authors.
The physiological and subjective effects
of brief smoking (10 minutes) are of
limited duration. Pulse rate peaks in about
10 minutes and is near the baseline after
three hours. Intraocular pressure mean decrease
is maximum in about 60 minutes
and subjective "high" peaks at about 30
minutes.9 Pupillary constriction peaked at
five minutes.s Clearance of A9THC from
human systemic circulation was not complete
for about three days after intravenous
injection.11
Findings relating to the chronic use of
cannabis are much more limited than
those on acute use. A recent report on
visual and ophthalmic effects after 10
years of use compared 39 users and
matched controls with equal cigarette
(tobacco) consumption.12 Although differences
of statistical validity were found
between users and controls none of the
differences were so large that pathology
could be inferred. Measures were reported
on pupil size and responsiveness, intraocular
pressure, dark adaptation, acuity,
color matching, lacrimation, fundus, and
conjunctival injection. The users were not
intoxicated during testing. Of particular
interest are the results on intraocular pressure,
pupil response, and conjunctival injection.
Intraocular pressure was found to
be slightly (0.7 mm. Hg) greater in users.
Pupil size and responsiveness was not
measurably different between groups, and
16 of the users were judged to have conjunctival
injection compared to 13 of the
nonusers.
An overview of this literature indicates
that there are numerous and complex effects
of THC on vision and the eye. These
vary with dose and with the individual experience
with the drug. The majority of
eye effects seem to be confined to the anterior
segment and in some ways mimic an
irritative process of that region. These effects
are transient and seem to produce no
cumulative effects of long term clinical
significance.
William W. Dawson
Departments of Ophthalmology
and Physiology
College of Medicine
University of Florida
Gainesville, Fla. 32610
REFERENCES
1. Quarles, W., Ellman, G., and Jones, R.:
Toxicology of marijuana: conditions of conversion
of cannabidiol to THC upon smoking,
Clin. Toxicol. 6: 211, 1973.
2. "Marihuana and Health": Reports to Congress
from the Secretary Health, Education,
and Welfare, 1971-1975. United States
Government Printing Office.
3. "Marihuana-Hashish Epidemic and its Impact
on United States Security." Hearings
before the Judiciary Committee. United
States Government Printing Office, 1974.
4. Shapiro, D.: The ocular manifestations of
the cannibinols, Ophthalmologica 168: 366,
1974.
5. Valk, I,.: Hemp in connection with ophthalmology,
Ophthalmologica 167: 413, 1973.
6. Moskowitz, H., Shania, S., and Schapero,
M.: A comparison of the effects of marijuana
and alcohol on visual functions. Current Research
in Marihuana, In: Lewis, M., editor.
New York, 1972, Academic Press, pp. 129-
150.
7. Hepler, R., and Frank, I.: Marijuana smoking
and intraocular pressure, J.A.M.A. 217:
1392, 1971.
8. Hepler, R., Frank, I., and Ungerleider, J.:
Pupillary constriction after marijuana smoking,
Am. J. Ophthalmol. 74: 1185, 1972.
9. Flom, M., Adams, A., and Jones, R.: Marijuana
smoking and reduced pressure in human
eyes: drug action or epiphenomenon?
INVEST. OPHTHALMOL. 14: 52, 1975.
10. Green, K., and Pederson, J.: Effect of Ao
tetrahydrocannabinol in aqueous dynamics
and ciliary body permeability in the rabbit,
Exp. Eye Res. 15: 499, 1973.
11. Lemberger, L.: Tetrahydrocannabinol metabolism
in man, Drug Metabolism and Disposition
1: 461, 1973.
12. Carter, W., and Coggins, W., editor: A
Study of the Effect of Chronic Smoking
Cannabis in Costa Rica. Final report contract
HSM-42-73-233 (ND) to National
Institute on Drug Abuse, United States
Public Health Service, Feb. 1, 1976.
Source: Investigative Ophthalmology: Cannabis And Eye Function
