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This is a brief survey of more than 100 syndromes in which microphthalmos and/or coloboma appear. It is suggested that the disorders be assessed systematically by consecutive discussions of their aetiology, morphology and embryology.
The majority of patients with microphthalmos and colobomas have genetic disorders. This is a survey of non-inherited, sporadic microphthalmos. Such cases may occur in the Goldenhar, CHARGE and VATER associations; it may also be due to teratological agents, for instance maternal ingestion of drugs, maternal infection, fever or irradiation. In these cases it is possible that neural crest cell development is abnormal. Some drugs, for instance retinoic acid are regulators of Hox genes which control an ordered sequence of differentiation; coloboma or microphthalmos may appear if deregulation occurs. Large choristomas of the anterior segment of the eye may be associated with microphthalmos or anophthalmos. Encephaloceles or orbital tumours may deform the growing eye and are another cause of non-inherited microphthalmos.
Simple microphthalmos was diagnosed in 22 patients on the basis of a normal-appearing eye and a total axial length at least 2 SDs below the mean for age. Anterior segment length was normal in most patients while posterior segment length was at least 2 SDs below the mean in all patients, indicating that disproportionate reduction in posterior segment length accounted for the microphthalmos. The normal values for total axial length, anterior segment length, and posterior segment length were determined from the analysis of axial length measurements obtained from age-similar controls. Ten patients had isolated microphthalmos. One of them was diagnosed as having nanophthalmos on the basis of microcornea, total axial length less than 18 mm, and absence of systemic disease. Twelve patients had associated systemic disorders, such as fetal alcohol syndrome, myotonic dystrophy, and achondroplasia, which implicated decreased size of the optic cup, altered vitreous proteoglycans, low intraocular pressure, and abnormal release of growth factors in the pathogenesis of microphthalmos.
Forty patients were diagnosed as having complex microphthalmos on the basis of a malformed globe with a total axial length measurement at least 2 SDs below the mean for age-similar controls. Three had anterior segment dysgenesis; 4, congenital lens abnormalities; 14, chorioretinal colobomas; 12, persistent hyperplastic primary vitreous; 4, retinal dysplasia; and 3, complex malformations due to ipsilateral facial malformations. Measurements of total axial length indicated that complex microphthalmos was congenital and that postnatal growth of the malformed eye was similar to that of normal eyes. In most patients the anterior segment length was normal, while in all patients the posterior segment length was at least 2 SDs below the mean. Corneal diameter correlated significantly with total axial length (r2 = .57) and decreased linearly as total axial length decreased. In most patients in whom measurements were obtained, the lens and corneal power were increased, thereby compensating for decreased total axial length. We propose that inadequate production of secondary vitreous is the cause of the microphthalmos, given that the posterior segment was disproportionately reduced in size and the secondary vitreous is its predominant component. Evidence that each of the various ocular malformations can influence the production of secondary vitreous is presented.
Three patients had microphthalmos with cyst in one orbit and contralateral congenital cystic eye, microphthalmos alone, or microphthalmos with cyst. Four eyes were examined histopathologically. The microphthalmic eye demonstrated a spectrum of anterior segment abnormalities, retinal disorganization and gliosis, and a choroidal and scleral colomboma. The cyst connected to the colobona consisted of an outer fibrovascular layer and inner gliotic neuroectodermal layer. The cyst probably originated from proliferation of neuroectodermal tissue at the edge of a persistently open embryonic fissure. Treatment consisted of multiple aspirations of the cyst, excision of the cyst alone, and excision of both the microphthalmic eye and cyst.
A 3-month-old girl presented with a rare occurrence of bilateral microphthalmos associated with orbital cysts. She underwent subtotal removal of the right orbital cyst. Histological examination was compatible with microphthalmos with orbital cyst. Although microphthalmos associated with orbital cyst is rarely encountered, it must be considered in the differential diagnosis of orbital cystic lesions.
The author has experienced a case of microphthalmos with large orbital cyst in a 4 months old female, that was found at the time of birth. To facilitate fitting a cosmetic prosthesis, the microphthalmos with cyst was removed surgically. On serial section I could find an area of discontinuation of the sclera that was suspected to be the defective closure of the embryonic cleft. Some aberrant retinal tissue was found in the wall of the cyst, and markedly disorganized ocular tissue forming a tumor-like mass filled the microphthalmic eyeball. In view of these histopathologic findings I could draw the conclusion that developmental failure of the embryonic eyeball and consequential proliferation of the embryonic neuroepithelial cells occurred at an early developmental stage causing the formation of microphthalmos with cyst.
We report two rare cases of corneal choristoma with microphthalmos. In both cases, the whole thickness of the cornea, as well as the anterior chamber and iris, was replaced by cutaneous and subcutaneous tissue. In case 1, diagnosed as dermoid choristoma, the cutaneous tissue contained skin appendages and subcutaneous fibrofatty tissue extended into the vitreous cavity. The fibrous mass in the cavity contained fragments of retina. In case 2, diagnosed as a dermislike choristoma, the cutaneous tissue lacked skin appendages. These choristomatous cutaneous tissues hindered normal growth of ocular structures, resulting in microphthalmos. Use of computed tomography was helpful in evaluating the extent of ocular tissue involvement and accompanying intraocular malformations.
A new model of inherited retinal degeneration has been found in the rat. It is inherited in association with a number of other ocular defects, including microphthalmos, coloboma, retinal dysplasia, optic nerve hypoplasia and/or aplasia, as well as medullation of the nerve fiber layer of the retina. Together, these abnormalities constitute a condition referred to as complicated colobomatous microphthalmos. This condition was originally discovered in the Bmn strain of rats but subsequently transferred to a new genetic background in the Bmn-wys strain of rats (BW). This facilitated the histological evaluation of both the developmental and degenerative ocular defects in the adult animals. A well defined pattern emerged relating eye size, optic nerve size and retinal histology. Normal-sized eyes had normal-sized optic nerves and normal retinal histology while intermediate-sized eyes with no optic nerves had uniformly thin retinas. In contrast, intermediate-sized eyes with small optic nerves had areas of both normal thickness and thin retina. All of these eyes developed retinal degeneration characterized by a late onset and slow progression associated with normal phagocytic activity in the pigment epithelium and a tendency for the rod outer segments to fragment into very thin structures rather than accumulate as lamellar debris. This indicates that the retinal degeneration in the BW model differs in many respects from the well studied RCS model.
A 23-year-old man had bilateral microphthalmos without microcornea. The eyes measured about 15 mm in length by ultrasound while the corneas were 11 mm in diameter. A distinctive, elevated, funnel-shaped retinal fold stretching between the disk and the macula was present bilaterally. Other unusual aspects were the deep anterior chambers and uncompromised chamber angles. This combination of anomalies is believed to be the result of a failure of growth of the posterior outer coats of the eye. These were of insufficient size to accommodate the excess sensory retina which folded to conform to its outer structural shell. Other cases of high hyperopia may in some instances be cases of microphthalmos, unrecognized because of normal-sized corneas.
We compared the distribution of birth order and maternal and paternal ages of blind school children throughout Japan with that of the total Japanese population of the corresponding age groups and with that of a subgroup of children with acquired blindness. The number of first-born children with microphthalmos was smaller, and the number of second-, third-, or fourth-born children was larger, as compared with the control groups. The differences were highly statistically significant by chi-square test. There was a less pronounced indication of birth order effect in amblyopia, congenital cataract, and optic nerve atrophy, which involved more first-borns than in the controls. The distribution of maternal age was also different from the control group in microphthalmos, congenital cataract, corneal opacity, and optic nerve atrophy. Less mothers in their 20s and more in their 30s produced children with these conditions. We believe this finding may be partly related to the rapid decline in infant mortality and in the incidence of congenital blindness in Japan.
A retarded boy with microcephaly, microphthalmos, and retinal folds is described. His mother and sister showed microphthalmos and the sister was also microcephalic. Another family showing similar findings has been described, indicating that this combination of abnormalities constitutes a discrete entity showing single gene inheritance.
The authors report an unusual sporadic case of bilateral posterior microphthalmos in an 8-year-old Chinese girl. Cycloplegic refraction showed hyperopia of 12.5 diopters in both eyes. Anterior segment examination showed normal corneal diameters, open angles, and normal lens thicknesses. Ultrasonography showed short vitreous compartments resulting in short axial lengths of 17.2 mm. Fundoscopy showed full-thickness macular holes associated with radiate retinal striae. This is the first report of bilateral macular hole formation in sporadic posterior microphthalmos. The literature is reviewed.
Posterior microphthalmos is a congenital anomaly of the posterior segment of the eye, caused by an abnormally thickened sclera. The thickened sclera does not impede the growth of the neuro-retina but seems to influence the development of the choroid and of the retinal pigment epithelium. This may explain the common occurrence of a papillomacular fold in such cases. As such eyes are at risk of developing uveal effusion or angle-closure glaucoma, it is important to consider the diagnosis of posterior microphthalmos in high hypermetropic eyes.
Standardized A scan echography is the best technique for the biometric parameters of the eye. This has been very useful in studying the sizes of the anterior and posterior segments of the eye in hereditary microphthalmos. Echography and a genetic study led to a new classification of hereditary microphthalmos.
A family with autosomal dominant congenital cataracts was studied to determine clinical variability. A total of 159 relatives was ascertained; 17 affected and 19 normal individuals were evaluated and their blood sampled for inclusion in the linkage analysis. The disease was compatible with normal to mildly decreased visual acuity until adult life in all affected except the product of a consanguineous marriage of affected first cousins who was born with bilateral microphthalmos and dense congenital cataracts, attributed to homozygosity of the cataract gene. There were no extraocular abnormalities; the patient was of normal intelligence. Twenty-three markers were typed, 18 of which were informative. Linkage could be excluded for all 18 markers at short distances.
We present magnetic resonance features of a case of bilateral microphthalmos with orbital cysts, a rare congenital anomaly resulting from defects in closure of the embryonic fissure of the optic disk.
A case of microphthalmos with bilateral colobomatous orbital cyst accompanied by polycystic kidney disease and vacuolization of myeloid progenitor cells is presented. Association of these three entities has not been described previously in the literature.