ACTA OPHTHALMOLOGICA VOL. 4 2 1964

From the Eye Hospital, University of Helsinki (Head: Prof. S . Vannas, M. D.)

and the Institute of Human Gendics of the Samfundet Folkhalsan

EMBRYOTOXON CORNEAE POSTERIUS I N A FAMILY WITH

SLIT-PUPIL AND I N CASES WITH OTHER ANOMALIES OF THE IRIS'.')

BY

Henrik Forsius and Aldur Eriksson

Embryotoxon corneae posterius (ECP), also called prominent anterior border- ring of Schwalbe or .dysplasie marginale posterieur<<, is a narrow, grey ring on the posterior surface of the cornea close to the limbus, as a rule present only temporally. In the slit-lamp it is seen in 15-30 per cent of all eyes (Streiff; Burian, Braley & Allen; Marty; Forsius, Eriksson & Fellman). Histo- logically, ECP consists of collagenous tissue. Lt occurs in association with anomalies of both mesodermal and ectodermal origin (Collier).

In those cases where ECP is conspicuous or is visible all around the limbus, different types of corneal and iris anomalies are often also present. The ring then frequently extends somewhat onto the cornea. Since Axelfeld in 1920 observed ECP in a case of hypoplasia of the iris and peripheral iris synechiae, numerous similar cases have been reported. ECP has been described in asso- ciation with the following anomalies of the iris:

ECP has been observed in aniridia, but not invariably. It has been described both in total aniridia [Lindberg; Esteban & Wolf (cit. Marty), Paganelli] and in the partial form (Rieger; Badtke) and coloboma iridis (Schmidt; Paufique. Gtienne & Bonnet; Collier). Hypoplasia of the iris is often present in eyes ex- hibiting ECP (Axenfeld; Thier; Friede; Remky; Kaminskij ; Hagedoorn; Schmidt; von Grosz; Streiff; Paufique et al.; Burian, Braley & Allen; Burian, Rice & Allen; Collier; Forsius, and others). Remnants of the pufiillary mem-

In part supported by a grant from the Sigrid JusClius Stiftelse, Helsingfors. ") Received September 23rd 1963.

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brane may be observable even in mild cases (Friede; Theodore; Paufique et a].). Gedda & Berard-Magistretti described a large family with progressive atrophy of the iris and glaucoma, corectopia and remnants of the pupillary membrane, in which ECP was observable in some members.

In severe anomalies of the iris, ECP may be combined with iris synechiae, which sometimes extend even to the central parts of the cornea (Theodore; Streiff; Grignolo; Collier). Among the deformities of the iris with which ECP is associated, anomalies of the pupil, e. g . corectopia (Knapp; Rossano; Hage- doorn; v. Grosz; Theodore; Hugger; Braendstrup; Grignolo), polycoria Vera (Lisch) or pseudopolycoria (Kaminskij ; Rossano; v. Grosz; Burian, Braley & Allen) are frequent. ECP has also been observed in iridoschisis (Waardenburg 1961). Furthermore, the anomaly was seen in a brother and sister with albino- ism (Waardenburg 1961).

Heredity of ECP The heredity of ECP without other ocular abnormalities has been the sub-

ject of another paper (Forsius, Eriksson & Fellman). The heredity of severe anomalies of the iris and cornea is often dominant. ECP in dysgenesis mesoder- malis corneae and iridis has been described by Waardenburg (1932), Schmidt, Braendstrup, Falls and Burian, Braley & Allen. If the iris anomalies and ECP are combined with oligodontia, the transmission is dominant (Rossano; Rieger; Schmidt; Rejchrt & Miksa; Unger; Kittel; Lemmingson & Riethe; Busch et al.). It may be mentioned that, according to a personal communication, the family described by Rossano now comprises three generations.

C A S E R E P O R T S

I. Aniridia Case 1 . Gunhild F., 45, female. Partial aniridia. Operated upon for cataract. ECP

in the right eye temporally at 7-10 o’clock and in the left eye nasally at 6-8 o’clock. No iris synechiae.

Case 2. Edit F-H., 57, female. Sister of no. 1. Partial aniridia in both eyes and cataract. ECP without iris synechiae in the left eye at 2-6 o’clock.

In two other siblings with clinically total aniridia ECP was absent. One son of a total of six children of no. 2 had embryotoxon, and of his two sons one had a weak, but obvious ECP, though otherwise completely normal eyes. None of the normal siblings of the subjects with aniridia had ECP, and the same holds good for the remainder of the descendants of these persons, totalling 22. (The family has been described in the Acta Ophthalm. 1963). Seven other subjects with aniridia, belonging to 5 families, had no ECP.

11. Coloboma of the iris

was absent, and there were no anterior iris synechiae, either. In two brothers with coloboma of the iris and cataract in both eyes, ECP

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111. Hypoplasia of the iris Case 1. M. P., 61, male. Hearing was impaired. Degeneration of the inner ear was

diagnosed on the basis of an audiogram. Glaucoma was observed a t the age of 38. Vision of the right eye 0.9 with + 2.25 D. Vision of the left eye I /m. In both eyes the cornea exhibited a long subepithelial Stahli’s pigment line (linea corneae senilis). The anterior layers of the iris were markedly hypoplastic. The pigment layers, which were visible over the whole of the iris, gave the eyes a brownish-grey colour. The an- terior chambers were of normal depth. Gonioscopically, peripheral synechiae to the anterior border-ring of Schwalbe were seen in the right eye at 1-6.30 and 8.30- 12 o’clock. In the left eye, the chamber angle was free only a t 6-7 and 11 o’clock (Fig. 1).

Case 2. H. V., 48, female. The breadth of the cornea was 11.5 mm in both eyes. Corneal refraction was 42.25:42.75 D (horizontal1y:vertically). The right eye showed markedly prominent ECP at 6-12 o’clock, with adhesions to the iris temporally in the upper quadrant. Nasally, the mesodermal layer of the iris was markedly hypo- plastic. In the left eye ECP was observable at 7-10 and 2-4 o’clock.

Case 3. K. L., 4, male. The corneal diameter was 10.5 mm, refraction 44.50 D. Right eye: ECP observable at 3-9 o’clock. At 5-5.30 o’clock tent-shaped iris synechiae to the ECP. There was a slight dislocation of the pupil downwardly and nasally. The ECP was partially fringed and pigmented. At 9-10 o’clock the ECP changed into a flat grey opacity. In the left eye ECP was present at 2-11 o’clock. Peripheral iris synechiae at 6-7. The pupil was dislocated downwardly and nasally and elongated in this direction. The iris was slightly hypoplastic. The patient was an only child. The mother was examined and found to have noimal eyes.

Case 4. K.L., 40, male. The vision of the right eye had always been poor. On examination it was found to be 0.5 E. The anterior chamber was low. Temporally there was a marked ECP with iris synechiae. Gonioscopically the chamber angle was found to be narrow. Cystic macular degeneration was present. The left eye was normal.

Case 5 . E. T., 7, male. Right eye: Vision 1.0 with + 6.5 2 cyl. + 1.5 D ax 90’. Gonioscopically a prominent anterior border-ring of Schwalbe was observable. Left eye: Vision 0.1 with + 5.5 cyl. + 2.5 ax 7 5 O . A convergent squint was present. ECP was present nasally at 8-10 o’clock, with anterior iris synechiae. Gonioscopically the ECP was partially pigmented.

The mother had high hyperopia, astigmatism and ECP, but no anomalies of the iris. Case 6. A. N., 18, female. Right eye: Vision 1.2 with + 0.75 D. ECP at 4-6 and

7-8, with iris synechiae. Between 4 and 5 o’clock, in an area between the ECP and the sphincter, the iris was split into two layers. The pupil was round, but somewhat dislocated towards 4-5 o’clock. Left eye: Vision 1.2 E. ECP at 6-8 o’clock. The iris was normal.

A sister to this patient had astigmatism (2.5-2.75 D) and ECP, but no anomalies of the iris.

Case 7. A 14-year-old girl in a school for the blind with nystagmus and albinotic uvea. She had slight ECP without iris synechiae, and astigmatism of 5.75 D in the right eye and 5 D in the left.

Case 8. K.V., 19, female. Rotatory nystagmus was present. Right eye: Vision 0.05 (+ 5.5 D z cyl. -3.5 D ax 90’). Corneal refraction 42:43.5 D. ECP a t 5-9 o’clock. A remnant of the pupillary membrane was discernible. Left eye: Vision 0.5 with + 5.5 D cyl. -0.75 D ax 30°. Corneal refraction: 43:44 D. ECP at 2-5 o’clock fringed in the lower quadrant. Remnants of the pupillary membrane were observable.

cyl. -2.5 D ax 0’. Case 9. L. L., 44, male. Right eye: Vision 0.7 with + 9.0 D

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Corneal refraction 40.5:42.5 D. Left eye: Vision 0.06 with + 8.0 D cyl. - 1.0 D ax 0’. Corneal refraction 40.75:42.75 D. The iris was hypoplastic in both eyes. ECP at 2-10 o’clock. The left eye showed an inward squint.

cyl. i- 8.0 D ax 90’. Corneal refraction 42.25:49.25 D. ECP at 2-5 and 7-1 1 o’clock. Gonioscopically a pro- minent border-ring of Schwalbe was visible all around the limbus. It was richly pigmented and exhibited round, white elevations. In the lower quadrant the ECP was partially double. From the iris collarette four iris synechiae extended into the anterior chamber, without reaching the ECP. Left eye: Vision 1.5 E. Corneal re- fraction 43.75:44.75 D. There was no ECP, and the iris was normal.

cyl. - 1.0 D ax 95’. The cornea, iris and lens were normal. Left eye: Vision 1.25 with 4- 0.5 D There was a divergent squint of 25O. The cornea was clear. The pupil was dislocated 2 mm towards 10 o’clock. Close to the margin of the pupil there was a hole in the iris measuring 1 mm, from which iris threads diverged. The Iens was clear. There was a large drusen of the optic nerve in both eyes.

Case 12. A. J., 24, male. Vision, corneal refraction and lens were normal. ECP was present in both eyes at 2-5 and 7-10 o’clock. The iris was brownish-grey, and hypo- plastic. Gonioscopically a prominent border-ring of Schwalbe was seen all around the limbus.

The ocular fundus showed heavy pigmentation in the form of spots and streaks. Pigmentation was also present in the right macular region. Adaptation was normal. The aetiology of the finding in the ocular fundus is still obscure.

Case 13. W. K., 47, female. Right eye: Vision 0.7 with 1.5 D. The iris was slightly hypoplastic and iridodonesis was present. There were abundant remnants of the pu. pillary membrane. Furthermore, there was a lateral coloboma of the lens with a con- cave margin. No ECP was observable. Left eye: Vision 0.01. The iris was in the same condition as in the right eye. The lens was dislocated straight downwards and showed opacities, particularly in the posterior cortex An ECP was present laterally.

Case 10. J. L., 35, male. Right eye: Vision 0.15 with - 4 D

Case 11. L. K., 19, femaIe. Right eye: Vision 1.0 with - 1.25 D

Familial progressive atrophy of the iris Case 1. T. K-R., 35, female. The patient was the fourth of five siblings. Her siblings

and their children were said to have normal eyes. Her husband had normal eyes. She had two children, and both had anomalies of the iris (see the following patients).

The patient’s hearing was impaired. According to the audiogram, the lesion was mainly located in the middle ear, but in addition there was a component indicative of a lesion of the inner ear. Right eye: Vision 0.4 with - 1.0 DE cyl. - 1.0 ax 0’. The corneal diameter was 11 mm, corneal refraction 41.75 : 42.75. In the corneal paren- chyma, arcus lipoides was seen macroscopically at 3-5 and 7-8 o’clock, but micro- scopically all around the cornea. The pupil was slit-like. The iris parenchyma was markedly hypoplastic. At 6 o’clock the iris tissue exhibited a slit, but there was no sphincter tissue. A definite ECP was discernible only in parts. At 5 and 7 o’clock two large grey synechiae extended from the sphincter tissue to the peripheral portion of the cornea. Threadlike anterior synechiae were seen at 1 1 and 2 and 4 o’clock. Gonio- scopically, thin synechiae were observable everywhere in the chamber angle. All synechiae were attached to the anterior border-ring of Schwalbe. In those sites where this was entire, they were also seen biomicroscopically. Left eye: Vision 0.3 (- 1.5 D cyl. - 1.5 ax O’), corneal diameter 10 : 1 1 , corneal refraction 42 : 41 D. In the corneal parenchyma arcus senilis was visible with the naked eye at 7-11 o’clock. There was a

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marked ECP at 2-9 o’clock. Biomicroscopically, it was seen around the whole of the limbus. Inside this, too, the posterior surface of the cornea was blurred over a breadth of 1 mm. Iris synechiae to ECP were present. The iris parenchyma was markedly hypoplastic, and the pigment layer gave the iris a dark brown colour. Temporally at the periphery, the anterior parenchymal layer and the posterior layers of the iris were separated. The pupil was slit-like, and drawn upwards nasally. Gonioscopically a markedly prominent anterior border-ring of Schwalbe was seen all around the limbus, and around the periphery there were thin iris synechiae extending to this. The chamber angle was for the most part visible through the synechiae, and at 6 and 12 o’clock, for instance, the latter were split up so much in the chamber angle that the picture resembled an exudate. The anterior chamber was normal in depth. The lens was clear, and the ocular fundus appeared to be normal.

During an observation time of 6 years, the hypoplasia of the iris increased (see Fig. 2 a, 2 b). The patient had glaucoma, which was controlled with miotics. Since vision was markedly impaired by the instillations, the patient did not follow the pre- scriptions consistently.

Case 2. M.R., 12, female. The daughter of no. 1 . Right eye: Vision 1.3 E, corneal diameter 12.5 : 13 mm, corneal refraction 42.5 : 42.75 D. ECP at 1-6 o’clock. The iris was hypoplastic. The pupil was round and central. There was a broad iris synechia to the ECP at 4-5 o’clock, and centrally of this the anterior and posterior layers of the iris parenchyma were separated. The anterior chamber was of normal depth. Left eye: Vision 1.3 E, corneal diameter 12:125 D, corneal refraction 43.75:44.5 D. An ECP was visible almost the whole distance between 2 and 9 o’clock. In parts, the posterior surface of the cornea was opaque even inside the ECP. Gonioscopically, anterior synechiae were seen at 2, 5-7 and 8 o’clock, and a prominent anterior border- ring of Schwalbe was visible all around the limbus (Fig. 3).

The patient had been treated for glaucoma for 3 years with the result that a fairly normal pressure had been maintained.

Case 3. R. R., 10, female. The sister of no. 2. She had been under treatment for in- creased ocular pressure for 6 years.

Right eye. (1957, Fig. 4 a). Vision 0.2 E, corneal breadth 12.5 mm. In the limbus corneae a superficial, thin corneoscleral opacity, 1 mm broad, was observable. The pupil was slit-like. The anterior iris layer was markedly hypoplastic. In the middle of the lower quadrant the pigment layer alone was visible. No ECP was discernible in the slit-lamp, but gonioscopically a prominent border-ring of Schwalbe was seen everywhere, and in many sites small or large iris synechiae were attached to it, in particular in those sites where the sphincter pupillae was closest to the limbus. The ocular fundus was normal. Left eye (1957, Fig. 5 a): Vision 0.2 E, corneal breadth 13 mm, refraction 38.5 : 39.5 D. Slight opacities of the posterior surface of the cornea were observable in the central part of the cornea. The pupil was slit-like. The ver- tically elongated sphincter pupillae was in contact with the posterior surface of the cornea at 6 o’clock. Above the pupil there was a vertical slit in the iris, measuring 5 mm. The iris was markedly hypoplastic, just as in the right eye. Pressure was about 40 mm Hg in both eyes. Instillation of miotic5 was instituted. The patient was not seen again until 1960. In February 1960 (Fig. 4 b) the pupil of the right eye was found to be dislocated somewhat upwards and to have become rotated some- what in the horizontal direction and more rounded. The slit in the iris was of the same size, but the atrophy of the iris parenchyma had progressed. The pupil of the left eye (Fig. 5 b) had become a little more downwardly dislocated, and the slit in the iris above the pupil had enlarged somewhat. Medication with Florop~yl drops

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Fig. 1. III/ l , M. P. Left eye. Anterior layer of the iris markedly hypoplastic. Sphincter pupillae clearly visible. Arcus senilis. Gonioscopically a prominent anterior border- ring of Schwalbe is seen, to which there are iris synechiae. Secondary glaucoma.

Fig. 2. a) IV/l, T. K. Left eye of a 29-year-old woman. Progressive atrophy of the iris with

slit-pupil.

b) The same eye 6 years later. The patient is receiving miotics. The hypoplasia of the iris and the arcus srnilis have increased. Embryotoxon corneae posterius with iris

synechiae is present from 2-11 o’clock (not visible in the photograph).

Fig. 3. IV/2, M. R., the 12-year-old daughter of the woman in Fig. 2. Left eye. ECP is visible

a t 1-6 o’clock. At 6 o’clock the anterior layer of the iris is split off (iridoschisis).

Fig. 4. a) IV/S, R. R., a 4-year-old girl (sister to the girl in Fig. 3) with slit-pupil laterally.

The right eye in 1957. b) The same eye in 1960. The pupil has been drawn upwards and become rounder

The atrophy of the iris has increased.

c) The same eye in 1961 before operation. The pupil has disappeared under the limbus at 11.30 o’clock. The sphincter is seen biomicroscopically as a round ring without any opening a t the centre. The direction of the iris synechiae shows the site of the sphincter pupillae. The atrophic area in the iris extends over the whole of the cornea.

The pigment layer, too, has split and the patient sees through this new pupil.

Fig. 5 . a) Left eye of the same patient as in Fig. 4 a, b, c. March 1957. Slit-pupil in the lower quadrant. The iris is hypoplastic and the sphincter pupillae clearly visible

b) Same eye in February 1960. The slit in the iris has become larger.

c) Same eye in October 1962. Ocular tension 55 mm Hg. The anterior chamber has disappeared. The pupil is seen through corneal opacities close to the limbus. The sphincter is now entirely circular. The slit extends across the whole of the cornea.

(di-isopropyl-fluorophosphate) once a day was instituted, and this led to normaliza- tion of the ocular pressure.

In 1961, the pupil of the right eye had been drawn upwards, so that it was covered by the limbus and only the lower portion of the sphincter was visible. The ocular pressure was 30 mm Hg. The dark area with a slit in the iris, which had previously been obliquely positioned, had been drawn out vertically and extended across the whole of the cornea (Fig. 4 c). The patient saw 0.3 (-2.5 D) through the slit. Pressure in the left eye was 40 mm Hg. The pupil of this eye is seen close to the limbus at 6 o’clock, and the slit in the iris had extended and become larger. Through this slit vision was 0.2 with -2.5 D. The anterior chamber was low in both eyes. The patient was given acezolamide, adrenaline and Tosmilen (decamethylene-bis) as ambulant treatment. After three weeks the anterior chamber had disappeared from the left eye and vision had decreased to 1/00 , and the cornea showed diffuse opacities. The ocular pressure was 43 mm Hg in the right eye and 59 mm Hg in the left. The slit in the iris of the left eye measured 2 X 8 mm, and the lens pressed against the cornea. After persistent persuasion, the mother consented to one operation. Since there seemed to be more hope with regard to the right eye, an iridencleisis was performed on this. A small piece of the iris which existed showed marked atrophy of the parenchymal tissue and smooth muscle tissue. Postoperatively, the anterior chamber was not re- formed. A sclerotomy was made, and air was injected into the chamber. The cham- ber was reformed, but a central synechia between the lens and the posterior surface of the cornea remained. Between these tissues some pigment was left. Since the lens was situated in an almost normal position, it had the shape of a lenticonus anterior with a protruding central portion. After operation the slit in the iris continuously enlarged until it extended across the whole of the cornea. Six weeks after operation there was an acute increase of the ocular pressure, and treatment for glaucoma was again instituted. Subsequently, the pressure was kept under control with miotics. Tono- graphically the outflow is normal and vision has remained the same. Now, in 1963, the corneal breadth of the right eye is 12.5 mm, and the corneal refraction 40.75: 37.75. The left eye is completely blind (Fig. 5 c).

At the World Congress in New Delhi in 1962, pictures of this patient, among others. were shown in connexion with a paper read on iridoschisis and essential iris atrophy (Forsius & Tarkkanen).

DISCUSS10 N

Since ECP is normally present in 12-30 per cent of the population, its pos- sible correlation with a certain ocular disease must be studied on the basis of a large series.

The commonest ocular anomaly which occurs in conjunction with ECP is hypoplasia of the iris. This was found to be the case in the present series, too. I t should be borne in mind, however, that hypoplasia of the iris is not in- variably accompanied by ECP, as was pointed out by Kayser as long ago as 1922, and as has also frequently been observed by the present authors. On the other hand, ECP is seldom accompanied by any other type of ocular changes. In a series of 700 subjects examined by Marty, there were 132 cases of ECP, but not a single case of atrophy of the iris, if the senile atrophy which is

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normal in the aged is excepted. In an ophthalmologist’s practice hypoplasia of the iris in association with ECP is a not uncommon finding, however. Minor iris synechiae are frequently observable in these cases, although only gonioscopically or after careful examination with the slit-lamp. In the present series some cases of this type have been included, but not all we have seen. Hence, the rarer, grosser deformities are predominant in this report.

In the literature, too, severe anomalies of the iris have mainly been de- scribed. Not even severe anomalies of the iris are invariably accompanied by ECP. In aniridia this condition is rare. W e saw it in 2 out of 9 cases in- vestigated, and in these patients the ECP was only of >>physiological<< degree of severity. It is striking that out of 24 relatives in a family in which ECP was observed, none had ECP except for two of the descendants of a patient exhibiting aniridia and ECP. These two had otherwise normal eyes, and it seems possible that ECP occurred in this family independently of the aniridia.

As judged by the data in the literature and on the basis of our own expe- rience it appears, however, that ectocoria, polycoria and slit-pupil - i. e. the group of diseases known under the name of dysgenesis mesodermalis corneae et iridis - are as a ruie combined with ECP. The partial aniridias with ECP which have been described (Badke; Rieger) belong to this group. By contrast, anomalies of the iris which are combined with ectodermal lesions, e. g. most cases of aniridia and hereditary iris coloboma with opacities of the lens, do not seem to occur in association with embryotoxon corneae posterius.

It is sometimes difficult to decide whether an ECP is present. In case III/1 (M. P.), for instance, no ECP was discernible. The finding of a prominent border-ring of Schwalbe - which anatomically is the same anomaly - was made by gonioscopy, which also revealed an abundance of iris synechiae.

The family R., IV/1-3, shows a very peculiar anomaly: slit-pupil, which later became perfectly circular, ECP and progressive atrophy of the iris. Ac- cording to Waardenburg ( I 9Sl>, slit-pupil in successive generations has been described only by Goto & Sibata, Baratta and Falls. Rieger has also described such a family. In the cases described by Baratta, ECP seems to have been absent.

Families with essential, not X-linked atrophy of the iris, probably progres- sive in nature (though this cannot be proved since the patients had not been examined previously) was observed by Kittel, Gedda & Bkrard-Magistretti, Lemmingson & Riethe and Blum, Allen & Holland. Kittel and Lemmingson & Riethe reported that anomalies of the teeth were also present in their patients. In the family described by Blum, Allen & Holland an anterior border-ring of Schwalbe was seen gonioscopically.

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SUMMARY

The occurrence of embryotoxon corneae posterius (ECP) or visible anterior border-ring of Schwalbe was studied in 16 subjects exhibiting various ano- malies of the iris. Normally, ECP occurs in 12-30 per cent of the population in Finland (studied with a slit-lamp). ECP was present in 2 out of 9 patients with aniridia. In 2 cases of congenital coloboma of the iris ECP was absent. Five patients with hypoplasia of the iris exhibited ECP. In 2 of these cases there were anterior iris synechiae to the ECP. Furthermore, the series includes one case in which both ECP and iris synechiae were discernible gonioscopi- cally, but not with the slit-lamp. In 3 other cases there were iris synechiae to the ECP without hypoplasia of the iris being present. In addition, ECP was observed in conjunction with three other types of anomaly of the iris. In 4 cases ECP was combined with hyperopia of over 5 D and in 2 cases with astigmatism of 5-8 D.

A family is described, consisting of a mother and two daughters with ECP, continuous changes in the position of the pupil, glaucoma and progressive atrophy of the iris, slit-pupil and pseudo-polycoria. These patients have been under observation for six years. To the best of our knowledge, such a com- bination of symptoms has not previously been described as a hereditary dis- ease.

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Burian, H. M., Braley, A . E., and Allen, L.: External and gonioscopic visibility of the ring of Schwalbe and the trabecular zone. An interpretation of the posterior corneal embryotoxon and the so-calIed congenitaI hyaline membranes on the posterior corneal surface. Tr. Am. Ophth. SOC. 1954: 52: 389-428.

Burian, H . M., Rice, M . H. and Allen, L.: External visibility of the region of Schlemm’s canal. A. M. A. Arch. Ophth. 1957: 57: 651-658.

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Collier, M.: La dysplasie marginale posttrieure de l a cornte dans le cadre des ano- malies squelettiques et ectodermiques. Ann. ocul. 1962: 195: 512-549.

Esteban, A . et Wolf, J . A.: Aniridia bilateral con ptosis y embriotoxon. Arch. oftal Buenos Aires 1948: 23: 141-148. Cit. by Marty.

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Grignolo, A,: Su due casi di aderenze congenite irido-corneali multiple associate in un paziente a deformazione ed ectopia pupillaire (disgenesis mesodermalis corneae et iridis di Rieger). Boll. ocul. 1949: 28: 641-648.

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