Schisis of the Eye: Causes and Related Conditions

The term “schisis” in ophthalmology refers to a split or cleft within the layers of the eye’s structures. It is not a single diagnosis but a descriptive term for a group of mostly congenital conditions present at birth, which arise from interruptions during the eye’s formation. The specific impact on an individual depends on which part of the eye is affected by the split.

Causes of Eye Schisis

The origins of eye schisis are rooted in early fetal development. As the eye forms, it begins as two small outgrowths from the developing brain that fold inward to create a cup-like structure. A temporary groove, the optic fissure, forms on the underside of this cup and the optic stalk and is meant to close by about the seventh week of gestation to allow blood vessels to enter the developing inner eye.

When this closure is incomplete, a gap or cleft remains, leading to the conditions categorized under eye schisis. This failure to close can happen at any point along the fissure, from the iris at the front of the eye to the optic nerve at the back.

While the direct cause is the incomplete closure of the optic fissure, the reasons for this interruption are not always clear. In some instances, genetic factors play a role, with mutations in specific genes disrupting normal eye development. These conditions can be associated with broader genetic syndromes, but a schisis-related condition often appears as an isolated event without a known family history.

Common Schisis-Related Eye Conditions

One of the most well-known conditions is a coloboma, a hole or gap in one of the eye’s structures. An iris coloboma, for example, results in a “keyhole” appearance of the pupil but often does not significantly affect sight. The pupil may be more sensitive to light because it cannot constrict as effectively.

A more impactful form is a chorioretinal coloboma, which involves a gap in the retina and the underlying choroid layer. The retina is the light-sensitive tissue lining the back of the eye, and the choroid is the layer of blood vessels that nourishes it. A gap in these layers means part of the visual field will be missing, and a coloboma of the optic nerve can also cause significant vision impairment.

Another condition is retinoschisis, defined by a splitting of the retina into two distinct layers. This separation creates a space that can fill with fluid, forming tiny cysts. Congenital or juvenile retinoschisis is a genetic disorder that primarily affects boys and young men, as the responsible gene is on the X chromosome. This splitting often affects the macula, the central part of the retina responsible for sharp, detailed vision.

The splitting of the retinal layers in juvenile retinoschisis prevents light from being properly processed, leading to blurry central vision that cannot be corrected with glasses. While a less common degenerative form can occur later in life, the congenital form is related to developmental abnormalities. This condition can lead to a gradual decline in vision during childhood that often stabilizes in early adulthood.

Symptoms and Diagnosis

The signs of an eye schisis condition vary widely. A coloboma of the iris is often identified at birth due to the visible keyhole shape of the pupil. Other symptoms that might prompt an eye examination include poor vision, light sensitivity (photophobia), or involuntary, rapid eye movements (nystagmus). If a coloboma is in the back of the eye or retinoschisis is mild, the condition may only be discovered during a routine vision screening.

Diagnosis is made by a pediatric ophthalmologist through a dilated eye exam. This procedure uses eye drops to widen the pupil, allowing the doctor a clear view of the structures inside the eye. An ophthalmoscope is used to illuminate and inspect the back of the eye for any gaps or splits.

For a more detailed analysis, especially when retinoschisis is suspected, a non-invasive imaging test called Optical Coherence Tomography (OCT) is used. An OCT scan provides a high-resolution, cross-sectional image of the retina, similar to an ultrasound. This technology allows the ophthalmologist to see the distinct retinal layers and identify the location and extent of any splitting. Genetic testing may also be recommended to confirm a diagnosis with a suspected genetic link.

Treatment and Management Strategies

There is no cure for the underlying structural defects of eye schisis, as the incomplete development cannot be reversed. Treatment and management focus on maximizing existing vision, addressing associated problems, and monitoring for potential complications.

Regular monitoring by an ophthalmologist is a primary part of management. For individuals with retinoschisis or chorioretinal colobomas, there is an increased risk of retinal detachment, a serious condition where the retina pulls away from the back of the eye. Frequent check-ups allow for early detection and treatment of such complications, which may involve laser surgery or cryopexy to secure the retina.

For many individuals, corrective lenses like glasses or contact lenses can help manage related refractive errors, though they cannot correct vision loss caused directly by the schisis. When vision is significantly impaired, low-vision aids become part of daily life to help with reading, schoolwork, and other visual tasks. These can include:

• Simple magnifiers
• Telescopes
• Advanced electronic devices
• Software that enlarges text and enhances contrast