Congenital glaucoma

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					Volume 7                                            Symposium on congenital anomalies 127
Number 2

                              Congenital glaucoma

             Remarks on the aspect of chamber angle,
           ontogenetic and pathogenetic background, and
                   mode of action of goniotomy

                                          /. G. F. Worst

 JL he author has designed a special tech-         velopment, during which phase they were
nique for chamber angle observation, as a          essentially normal structures. The main
diagnostic and as a surgical procedure.1           characteristic of the congenital glaucoma
The optical quality of the chamber angle           angle is its chronologically fetal condition.
images obtained with it and the ability to         A pathogenetic vicious circle is present as
use this system at high power magnifica-           high pressure caused by aqueous secretion,
tion during operations have permitted us           and the persistence of a fetal condition is
to visualize, in some favorable cases of           incompatible with aqueous outflow. Go-
congenital glaucoma, certain finer details         niotomy relieves the high pressure by
of the congenital glaucoma chamber angle,          breaking apart the covering surface mem-
which we believe to be of significance in          brane, and thereby allowing the aqueous
the formation of a pathogenetic concept            humor to pass through the spongy uveal
of this disease. The essence of this concept       meshwork and the underdeveloped corneo-
is that in congenital glaucoma the chamber         scleral meshwork and Schlemm's canal. In
angle is filled with a band of persistent          typical cases this relief of high pressure is
mesodermal tissue (persistent uveal mesh-          sufficient to allow a development toward
work or persistent pectinate ligament).            functional normalcy. Having established
This tissue completely covers the fetal cor-       the presence of persistent uveal meshwork
neoscleral system, but is not the cause of         in congenital glaucoma and in normal fetal
the obstruction to aqueous outflow in its          angles, we were forced to propose a hy-
own right. It is the presence of an imper-         pothesis for its disappearance in normal de-
forate surface layer on this persistent meso-      velopment. In particular, certain theories
dermal tissue, which is the only cause of          have been proposed which deny the possi-
obstructed outflow. This surface mem-              bility of the angle remaining filled with
brane, Barkan's membrane, is probably an           mesoderm. In terms of the cleavage theory,
endothelial surface, which normally breaks         as developed by Burian, Braley, and Allan2
apart, but which persists in congenital            and supported by Manschot,3 atrophy and
glaucoma.                                          remnants with reference to congenital glau-
   Ontogenetically, the persistent mesoderm        coma have been called misleading con-
and its covering surface layer (and prob-          cepts.
ably also its surface layer) are remnants             A study of the prevailing concepts of
of an earlier phase of chamber angle de-           chamber angle development led to a new
                                                   theory which is neither based on atrophy
   University Eye Clinic, Groningen, The Nether-   nor cleavage but introduces a new concept
lands.                                             of changing relations in fetal angle struc-
128 Symposium on congenital anomalies                                    Investigative Ophthalmology
                                                                                          April 1968

tures. This concept discards cleavage as a       higher powers. We make mention of this
possible mechanism. It reappraises the           here as it may form one explanation why
older concept of atrophy by giving a more        certain angle details can only be seen with
detailed description of the transitional pro-    certain microscopes (providing optimal
cesses which finally lead to the disappear-      types of contact lenses are used).
ance of the uveal meshwork in normal de-            The author's lens seemed specially
velopment. This new concept cannot be            adapted for the observation of fine cham-
brought under one simple denominator,            ber angle details. It has a flat anterior sur-
and therefore will be called the develop-        face at a right angle to the line of observa-
mental angle theory of the changi7ig micro-      tion of the chamber angle. It provides
anatomical relations.                            nearly a 180 degree view of the angle with-
                                                 out mirror inversion, and in its normal
Gonioscopic technique                            anatomical relations, the flat anterior sur-
   Contact lens and microscope. Various          face guarantees that no optical errors are
systems can be used for gonioscopy of the        present because of spherical aberration. If
normal eye, for instance, Goldmann's lens        care is taken to keep the anterior surface
or the Barkan-Koeppe type of lens. In the        perpendicular to the line of observation,
examination of congenital glaucoma, how-         all prismatic errors are also excluded. In
ever, various adverse conditions are pres-       fact this lens acts as if the cornea had been
ent, which limit visibility of finer details.    anatomically removed. Loss of definition
This examination requires general anesthe-       with this lens is exclusively caused by op-
sia, which until the advent of the Zeiss         tical defects of the cornea itself. These op-
slit-lamp microscope, excluded the use of        tical defects, particularly in congenital
normal slit-lamp procedures. Furthermore,        glaucoma, may be of considerable impor-
for the observation of fine details it is nec-   tance (see the following discussion). This
essary to use such contact lenses, which         prismatic type of contact lens also allows
have no optical defects of their own. Any        special modes of illumination, which forms
spherical type of contact lens has an ad-        another means of increasing magnification
vantage of inherent magnification and can        without loss of detail (see Angle illumina-
be used without slit-lamp on the recumbent       tion). Several modifications of this lens
patient, but also has the disadvantage of        have been realized for gonioscopy, goniot-
not being corrected for optical errors. This     omy, angle photography, and angle cine-
implies that at the higher magnifications,       matography, with the author's principle of
as can be obtained by the microscope, a          the internally lighted contact lens. Only
loss of resolving power occurs (Leerver-         with the advent of "fiberlight" could a
groszerung). Only such contact lenses that       practical type of lens based on the inter-
have no magnification of their own can be        nally lighted principle be realized. The fi-
used at all for high power observation. The      berlight lenses have now replaced the
increase of magnification in this instance is    original internally lighted lenses, which
provided by the microscope itself.               used small cystoscope lamps for illumina-
   For the purpose of viewing angles at a        tion. A serious disadvantage of these lamps
high magnification, we have modified the         was the tendency to have frequent break-
Wild stereomicroscope, which proved to be        downs.
an observation instrument of outstanding            A special fiberlight contact lens for
quality. Only the more recently developed        goniotomy has also been made. This lens
Zeiss operating microscope can be com-           should be used as a handheld goniotomy
pared with it. We have had occasion to use       lens, as advocated by Swann. In the au-
a number of other German, French, Japa-          thor's opinion, however, this lens, though
nese, and American types of microscopes          very practical for routine goniotomy, does
and noticed a visible loss of quality at         not allow the researcher to make detailed
Volume 7                                         Symposium on congenital anomalies 129
Number 2

observations of the angle during the opera-      corneal edema is always present. Coaxial
tion. It seems that only the more elaborate      illumination produces corneal reflexes in
type of goniotomy lens, as designed by the       the same corneal areas as through which
author, is adapted for this type of clinical     the angle must be observed. Strongly fo-
research.                                        cused, very oblique incidence of the light,
   The goniotomy lens. This lens is based        however, produces a partial retroillumina-
on the same optical principle as the pris-       tion, which brings out certain angle struc-
matic gonioscopy lens. It has, however,          tures in "dark background" relief. As more
special features for its surgical use. First,    of the whole cornea is available for obser-
it carries a scleral rim with four holes in      vation, the chances are better that the
it, through which four episcleral sutures         angle can be observed in detail. The inter-
must pass for fixation. Second, the lens has     nally lighted lenses have special signifi-
a cannula through which the space between        cance in this respect. A detailed study of
the lens and the cornea can be filled with        angle structures in congenital glaucoma,
 saline during the most critical phases of       however, requires both types of illumina-
 the operation. Third, a lateral hole permits    tion. Also one must be able to switch from
introduction of a special goniotomy knife.       one type of illumination to the other dur-
 This knife permits full control of anterior     ing surgery.
 chamber depth.                                     Optical corneal defects in congenital
   This fairly elaborate technical setup,        glaucoma. A serious limitation of angle
consisting of a special microscope, special      visibility is the edematous condition of the
lens, knife, and surgical technique, has been    cornea. It is for this reason that the most
designed in the first place to enable ob-        dependable angle observations could only
servation of the angle during the operation      be done after a successful goniotomy had
 at the highest possible magnification. It is    normalized the pressure. To obtain more
not stressed that this system is the best        information on these angles, goniotomized
 available for routine contact lens goniot-      and nongoniotomized areas have been com-
omy, as other systems work equally satis-        pared. Further, in a small number of cases,
factorily, for instance, Barkan's original       experimental incisions have been made be-
method. It seems certain, however, that          side the actual surgical incision on Barkan's
the author's approach provides maximum           membrane. Such experimental incisions
control over each phase of this apparently       were: (1) local extremely superficial stabs
simple operation, which in fact is often ex-     into the angle and (2) partial skipping of
ecuted in a less than optimal manner, be-        the angle during the goniotomy, resulting
cause one readily fails to observe some          in the persistance of short bridges of intact
minor detail. For a full description of this     angle between two adjacent goniotomy
technique see Worst.4'5                          slits. From stereoscopic observation of these
   Angle illumination. Another factor which      angles, it became apparent that these an-
influences chamber angle visibility is its il-   gles had a very special structural arrange-
lumination. Contrary to the general belief,      ment in common. A fine membranaceous
it is not advisable to use a lamp held close     surface covered all angle structures. Con-
to the surgeons head. This may be useful         cluding from the actual surgical behavior
with spherical types of lenses, when used        and from the experimentally incised
under simple surgical conditions. With the       stretches, this seemed to us an imperforate
author's prismatic type of lens it proved        surface. In particular the small surface
better to obtain strong focal illumination       stabs very strongly suggested the presence
at a right angle to the line of observation.     of an ultrathin transparent surface cover-
Also for spherical types this is the better      ing. Stereophotographs were made with
type of illumination. The reason the coaxial     Donaldson's camera (courtesy of Mr. Lis-
lighting is less than optimal is that some       ter) and Dekking's camera. The phenomena
130 Symposium on congenital anomalies                                    Investigative Ophthalmology
                                                                                          April 1968

as seen during the operation could be re-         direct stromal inhibition of aqueous humor
produced in these stereoslides.                   due to Descemet's ruptures. This type may
   Rarely will the actual breaking apart of       seriously interfere with gonioscopy. One
Barkan's surface membrane be observed in          possible way to obtain some angle visibility
detail during goniotomy. The best way to          is to perform goniotomy in such part of the
visualize it is to apply the tip of the goniot-   angle, which is least influenced by the Des-
omy needle to the base of the iris and de-        cemet's rupture. With the author's sutured
press it slightly. Stretching and finally over-   contact lens, goniotomy in unusual parts
stretching of the surface membrane when           of the angle is relatively easy.
retroillumination is used, may at times re-          White cicatricial edema (usually associ-
move any doubt as to the presence of Bar-         ated with bullous epithelial edema). This
kan's membrane. The presence of this              type of edema, which indicates a poor
membrane is hypothetically extended to all        prognosis, makes contact lens visibility
typical cases of congenital glaucoma.             completely impossible and one should use
   In many cases visibility is limited, and at    Urrets-Zavalia's goniotripsy operation.7
high magnification no details are visible.           Poor angle visibility caused by Desce-
Poor visibility of the angle prior to surgery     met's folding. Contact lens pressure, par-
is due to epithelial edema, edema of the          ticularly in congenital glaucoma, which has
corneal stroma, local corneal edema, white        a relatively thin cornea but a well-devel-
cicatricial edema, and poor angle visibility      oped Descemet's membrane may produce
caused by Descemet's folding.                     a series of transverse highly refractile
   Epithelial edema. This may be removed          ridges, which reduce the resolving power
by scraping with a round-bellied knife. One       of the gonioscopic system considerably. All
drop of 70 per cent alcohol, absorbed in a        handheld gonioscopy and goniotomy lenses
surgical microsponge, however, is a more          suffer from this defect. It is only the au-
rapid and effective procedure for removing        thor's water-cushioned type of diagnostic
the epithelium. The epithelium is chemi-          (for photography and cinematography)
cally coagulated and can be removed sim-          lens and surgical lens (prismatic goniotomy
ply by wiping it off. Regeneration is not         lens) which do not exert pressure on the
negatively influenced. Care should be             cornea. This may be one more reason why
taken, however, to leave an intact ring of        certain angle details have been more visible
peripheral epithelium. This effective tech-       to us than to others.
nique of epithelial abrasion was originally
introduced to us by Van den Heuvel.6              Typical elements of the congenital
   Note: in chamber angle operations the          glaucoma angle
epithelium must always be removed, even              Combined gonioscopic and goniosurgical
when corneal clarity seems sufficient for         observations led us to the conclusion that
surgery. It usually will cloud over during        these angles, though varying very much in
some phase of angle surgery, and removal          secondary changes because of stretching,
at that time is impossible. The application       have much in common among themselves
of glycerine or a hypotonic salt solution is      but are also greatly related to normal in-
less effective.                                   fantile angles. Some typical elements of the
   Edema of the corneal stroma (pressure          congenital glaucoma angle can be inter-
edema of the diffuse type). This type of          preted as having been formed from an atyp-
edema may considerably interfere with de-         ical fetal angle after secondary stretching
tailed angle observation, though focal ret-       has exposed various structures. One of
roillumination may partially remedy this.         these exposed elements is the typical scal-
Glycerine or a hypotonic salt solution are        loped edge of the posterior pigment layer,
of no avail.                                      which is the normal pigment layer, over-
   Local corneal edema. This is caused by         stretched and in an upright position, and
Volume 7                                        Symposium on congenital anomalies 131
Number 2

which is more visible than usual because of     special in the angle of congenital glaucoma.
iris stroma atrophy. This atrophy is in fact    On the basis of our developmental theory,
the original fetal condition of the iris,       we are inclined to call this imperforate
which has to cover an unusually large area.     surface an endothelial membrane. Histo-
It therefore becomes thin and transparent.      logical proof of this structure is almost
Other exposed elements are the vascular         completely lacking. This absence of histo-
loops running upward into the depth of          logical proof, however, has little influence
the band of mesodermal tissue. These are        on the probability that this concept is valid.
not neoformations, but the ciliary vessels         Microdissections from one case of con-
exposed by central traction.                    genital glaucoma4 have enabled us to dem-
   An atypical, but, nevertheless, very char-   onstrate this membrane, but also its highly
acteristic element is the peculiar layer of     vulnerable character. It is in the nature of
mesodermal tissue covering the iris surface,    this surface structure, which probably con-
such as a "morning mist" appearance de-         sists of a sheet of overstretched endothelial
scribed by Lister,8 in addition to the broad    cells, that it is highly vulnerable to the
band of persistent uveal meshwork cover-        influence of mechanical distortion and fixa-
ing the whole angle. It must be stressed        tion fluids. In particular, the ones usually
that both the mesodermal tissue covering        applied to pathological specimens (forma-
the iris surface and mesodermal band are        lin and alcohol). In this case it was also
more conspicuous in congenital glaucoma         evident that even the most careful micro-
than in normal infantile angles. Combined       preparative approach disrupts its continu-
with the effects of internal and external       ity. This is completely in accordance with
stretching, this leads to a completely typ-     microsurgical findings during goniotomy;
ical aspect of the angle of congenital glau-    the most superficial touch will break this
coma in most cases. Occasionally this as-       surface.
pect remains close to normal, however. The         The dissection of one enucleated con-
most characteristic aspect of the angle of      genital glaucoma eye showed that the
congenital glaucoma is not based on one         membrane formed the first layer of about
single sign of tissue abnormality, but on       12 to 15 layers of highly permeable uveal
the totality of signs which signify that we     meshwork. For further details of the mem-
are in the presence of a more or less de-       brane theory see reference 4.
velopmentally retarded structure. We have
come to believe that the only typical ele-      Fetal origin of the pectinate ligament
ment of congenital glaucoma, Barkan's              A new theory of chamber angle develop-
membrane, is at the same time the poorest       ment. Having shown that Barkan's mem-
demonstrable element. Barkan's membrane         brane and its underlying mass of persistent
sets the congenital glaucoma angle apart        uveal meshwork is a biological reality, the
from fetal and infantile angles, not so much    next step was to explain the fetal develop-
morphologically, but pathophysiologically.      mental mechanism which might lead to
Normal infantile angles, sometimes clearly      the persistence of uveal meshwork both in
showing the "morning mist" and the meso-        normal (temporary persistent) and in path-
dermal filling of the chamber angle, carry      ological angles (permanently persistent,
a perforate membrane, in distinction with       unless a goniotomy was performed).
congenital glaucoma where the whole                We came to the conclusion that present
chamber angle is separated from the an-         theories of angle development could not
terior chamber by a closed surface. Since       account for the presence of a mass of meso-
only the most elaborate and careful gonios-     dermal tissue in the angle, neither in nor-
copy sometimes shows the presence of this       mal nor in abnormal situations (cleavage
structure, it is not surprising that some       versus resorption theory). For a detailed
authors have been unable to find anything       criticism of these concepts, see reference 4.
132 Symposium on congenital anomalies                                      Investigative Ophthalmology
                                                                                            April 1968

   The cleavage theory, as developed by           abnormal development, when this change
Burian, Braley, and Allan2 and supported          has become halted in some earlier develop-
by Manschot,3 is based on the assumption          mental stage.
that the angle is formed by the separation           In earlier stages no true scleral spur
of two preformed and structurally different       formation is present yet. However, with
tissue layers. In the specimens shown in          the formation of the scleral spur, the cor-
support of this theory (Manschot3), the           neoscleral system is fanned out and its
most plausible explanation of the chamber         base is "carried" into the receding tendons
angle cleft was a simple artifact.                (the fetal uveal meshwork) of the ciliary
   The resorption theory in its simplest          muscle. The muscle endings now become
form (Barkan9 and Mann10) states that a           gradually incorporated into the scleral
mass of mesoderm, present in the earliest         spur. Each ciliary muscle fiber sheet, which
stages, disappears through atrophy.               has found its "footing" on the scleral spur,
                                                  means the loss of one sheet of fetal uveal
New theory of chamber angle                       meshwork. Therefore, it is the ingrowing
development                                       scleral spur which determines the gradual
   The shifting microanatomical relations         disappearance of uveal meshwork. If this
in the chamber angle during ontogeny. In          scleral spur separation mechanism fails to
early stages of anterior chamber develop-         occur, a typical chamber angle arrange-
ment, a true chamber angle is only present        ment results, and a certain amount of uveal
as a slitlike extension of the anterior cham-     meshwork fills the chamber angle. Most
ber (which is a virtual space, potentially        of the ciliary muscle fibers, if not all, insert
present, and only visible after fixation fluids   into this triangular block of persistent uveal
have artificially opened it). In the 5 month      meshwork. The actual corneoscleral system
embryo the bottom of the chamber angle,           is an underdeveloped area overlying
if formed by a block of mesodermal tissue,        Schlemm's canal and is quite insignificant
consists of loosely meshed fibers which are       in comparison with the large amount of
the extension of the primordial ciliary           uveal meshwork. This is in fact the micro-
muscle. This area must, by definition, be         anatomical situation of congenital glau-
called the fetal pectinate ligament, accord-      coma.
ing to Seefelder.11 As it is the direct ex-          Those who deny the presence of uveal
tension of the ciliary muscle (longitudinal       meshwork in congenital glaucoma (Mau-
part), it is its primordial tendon. The pri-      menee12) have become entangled in a
mordial corneoscleral system forms part of        miniature semantic jungle, such as the
the primitive scleral tissue. It is a fanlike     large amount of abnormal tissue in the
extension situated at the end of the early        angle of congenital glaucoma should not
Descemets membrane formation. This                be called abnormal corneoscleral meshwork
primitive corneoscleral system in the ear-        but persistent uveal meshwork instead. The
lier stages lies side-by-side to the ciliary      abnormality of the corneoscleral meshwork
muscle-uveal mesh work complex. This orig-        is its insignificance in comparison with the
inal orientation is progressively lost during     persistent uveal meshwork, which com-
development and, as is well known, the            pletely covers the underdeveloped corneo-
ciliary muscle fibers (longitudinal part)         scleral meshwork.
are inserted into the scleral spur. As these         During the transitional stages of the
fibers are originally inserted into the fetal     shift in relations between the ciliary mus-
uveal meshwork (fetal pectinate ligament),        cle-uveal meshwork on the one hand and
a change of microanatomical tissue rela-
                                                  the corneoscleral-scleral spur complex on
tions occurs. This explains the disappear-
                                                  the other hand a regular layer of cells
ance of the fetal uveal meshwork, in nor-
                                                  covers the sinus formed by the iris base,
mal development and its presence in
                                                  the base of the uveal meshwork and the
Volume 7                                       Symposium on congenital anomalies 133
Number 2

top of the corneoscleral system. This layer    preparations and slides from various lab-
of endothelial cells is continuous with        oratories. Microdissections were performed
Descemet's endothelium. This layer also        on material from the University Clinic of
covers the anterior surface of the pupillary   Obstetrics. The fact that the material has
membrane. In the early stages this anterior    come from a variety of specimens (in par-
chamber sac is separated from the pos-         ticular as the material from abortions, on
terior chamber by the pupillary membrane,      which we have relied most in the micro-
but it seems that fluid entering this an-      anatomical dissections) and from undated
terior chamber endothelial sac still cannot    or poorly dated sources, we have proposely
reach the corneoscleral system (through        refrained from an exact dating of the pro-
the uveal meshwork) as this is still covered   cesses of microanatomical shifts. It is the
by an endothelial surface.                     general sequence of events, apparently not
   It is a matter of conjecture when the       described before, which forms the basis
excretory pathways are opened, but it          of our theory. More exact dating should
seems plausible that this occurs in time       now be possible, by re-examination of well-
with the production of aqueous humor.          dated specimens. It should be realized,
For aqueous humor to leave the anterior        however, that only the fate of the uveal
chamber in fetal life, two barriers must       meshwork can be studied by the use of
have been removed: (1) the pupillary           slides. The endothelial covering surfaces
membrane and (2) the endothelial cover-        must be studied in microdissections, flat
ing of the uveal meshwork. In addition to      preparations in phase contrast microscopy,
these barriers, two more areas must have       and so forth.
reached functional maturity: (1) the uveal
meshwork must have been removed from           The mode of action of goniotomy
the uveal meshwork (though its spongy             The explanation of the beneficial effect
aspect would not indicate a barrier to out-    of goniotomy must take into account that
flow, the fact that it is the carrier of the   the most superficial incision already results
angle endothelium might, nevertheless, in-     in pressure normalization. In the manner
dicate that it must be at least partially      we have applied Barkan's operation we
absent in order to allow aqueous to reach      have been able to perform this operation
the corneoscleral system), and (2) the         by simple disruption of Barkan's mem-
corneoscleral meshwork and Schlemm's           brane. On pathological anatomical grounds
canal.                                         Maumenee13 has stated that it is im-
   The covering layer of the uveal mesh-       possible to perform a truely micrometric
work in early stages should be called the      type of incision and that every surgical
endothelial chamber angle membrane. In         intervention in the congenital glaucoma
our opinion this membrane is the precursor     angle must inevitably touch deeper struc-
of Barkan's membrane. In normal de-            tures. We have been able to demonstrate
velopment this surface covers ends as a        in a goniofilm that such superficial incision
functionally and anatomically perforate        is, in fact, fairly easily obtained.
layer. Though at birth a considerable             As these superficial incisions of Barkan's
amount of uveal meshwork may be pres-          membrane result in tension normalization
ent, it is not kept together by this surface   the only conclusion which we can draw
structure. The same uveal meshwork is          from these observations is that Barkan's
present in congenital glaucoma. Here,          membrane is the cause of the obstruction
however, Barkan's membrane forms a com-        to aqueous outflow. We realize that this
plete obstruction.                             forms no final proof of the existence of Bar-
   The concept of changing relations in        kan's membrane, but it is from these sur-
chamber angle microanatomy is based on         gical observations in the first place, that
the study of a number of embryological         its existence has been deducted.
134 Symposium on congenital anomalies                                        In oestigative Ophthalmology
                                                                                              April 1968

    REFERENCES                                      12. Maumenee, A. E.: Pathogenesis of congenital
 1. Worst, J. G. F., and Otter, K.: Low vacuum          glaucoma, a new theory, Am. J. Ophth. 47:
    diagnostic contact lenses, Am. J. Ophth. 51:        824, 1959.
    527, 1961.                                      13. Maumenee, A. E.: Discussion of Worst, J.
 2. Burian, H. M., Braley, A. E., and Allan, L.:        G. F., The cause and treatment of congenital
    A new concept of the development of the             glaucoma, Tr. Am. Acad. Ophth. Oct. 766,
    chamber angle, Arch. Ophth. 53: 783, 1955.          1964.
 3. Manschot, W. A.: Ocular anomalies in osteo-
    genesis imperfecta, Ophthalmologica 149:        Discussion
    241, 1965.
 4. Worst, J. G. F.: The pathogenesis of con-          Drs. Levon Garron and Lorenz Zimmer-
    genital glaucoma, Springfield, 111., 1966,      man. In the discussion which followed Dr.
    Charles C Thomas, Publisher.                    Worst's paper, Levon Garron, M.D., pointed
 5. Worst, J. G. F.: Goniotomy, a microsurgical
                                                    out the pathologist's objection to the con-
    procedure, Internat. Eye Film Library, 1965.
 6. Van den Heuvel, J. E. A.: Personal communi-     cept of an impermeable Barkan's membrane
    cation, 1965.                                   covering the inner trabeculum which
 7. Urrets-Zavalia, A.: Goniotripsy: An operation   looks perforate. Lorenz Zimmerman, M.D.,
    for congenital glaucoma, Ophthalmologica        pointed out that the trabecular sheets
    140: 14, 1960.                                  should be compressed against the inner
 8. Lister, A.: Surgery of congenital glaucoma,
    Tr. Ophth. Soc. Australia 11: 39, 1952.
                                                    wall of Schlemm's canal if the intraocular
 9. Barkan, O.: Pathogenesis of congenital glau-    pressure were being exerted against an
    coma, Am. J. Ophth. 40: 1, 1955.                impermeable membrane. Yet, in all speci-
10. Mann, J.: Developmental anomalies of the        mens open spaces can be seen between the
    eye, London, 1937, Cambridge University         trabecular sheets. It was agreed that the
    Press.                                          final word on pathophysiology of infantile
11. Seefelder, R.: Das Verhalten der Kammer-
    bucht und ihres Gerustwerkes bis zur Geburt,    glaucoma had not yet been said.
    Graefe-Saemisch Handbuch 50, 1 Abt. 1910.

                     Tonometry and tonography in
                         congenital glaucoma

                        John Hetherington, Jr., and Robert N. Shaffer

K   I ormal standards of intraocular pressure
and tonography for adult patients are fairly
                                                    ated to provide some knowledge of the
                                                    mechanisms of the action of goniotomy.
well established. These levels, however,            However, the inconsistent results on ex-
may not apply to infants. The resistance of         amination forced a re-evaluation of all as-
the child to examination, sedatives, anes-          pects of tension measurements in the anes-
thetic agents, and other factors cause              thetized infant.
changes in aqueous dynamics that can lead              Giles1 in 1959 reported a mean pressure
to misunderstanding. This study was initi-          of 25.8 mm. Hg without general anesthesia
                                                    on 32 full-term newborn infants. The au-
From the Department of Ophthalmology, Univer-
                                                    thor admitted that the examination was
  sity of California Medical Center, San Fran-      difficult and possibly inaccurate. Korn-
  cisco, Calif.                                     blueth and associates2 in the same year ex-

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Description: Congenital glaucoma