ACQUIRED RETINOSCHISIS

SIGNS AND SYMPTOMS
The patient is nearly always asymptomatic. Rarely, the patient reports a sharp visual field defect corresponding to the area of the retinoschisis. Ophthalmoscopy reveals a smooth, stationary, bullous elevation of either the inferior-temporal or superior-temporal retina. The elevation may extend beyond the equator, and may rarely invade the posterior pole. The dome of the elevation is smooth and translucent. Blood vessels traverse the dome and cast shadows on the underlying structures. There is no pigmentation line unless a concurrent retinal detachment exists.

PATHOPHYSIOLOGY
Every eye over the age of eight years manifests peripheral cystic changes in the inner nuclear and outer plexiform layers of the retina. These spaces coalesce to form interlacing tunnels. If enough cystic spaces coalesce, the retina will form a retinoschisis, splitting into an inner and outer layer cavity. The superficial retinal layers comprise the inner layer, while the deeper layers of the retina and RPE represent the outer layer of the retinoschisis cavity.

There are technically two types of acquired retinoschisis. There is the typical degenerative retinoschisis, which presents as a shallow elevation of the inner retinal layers. There is also reticular degenerative retinoschisis, which presents in the traditional appearance of a bullous elevation.

In all types of acquired retinoschisis, either the inner layer or the outer layer, or both layers, may develop holes. Should holes develop in the inner layer of the retinoschisis, then liquid vitreous may flow into the fluid cavity. This doesn't change the prognosis. If there are outer layer holes as well, then liquid vitreous could enter the subretinal space and cause a rhegmatogenous retinal detachment. To this end, retinoschisis with both inner and outer layer holes has the potential to progress to rhegmatogenous retinal detachment. The risk of progression to rhegmatogenous retinal detachment in retinoschisis with double layer holes is 0.25 to 1.4 percent. The risk of detachment in retinoschisis without double layer holes is 0.024 percent. There is also potential for the splitting of the retina to continue with posterior extension of the retinoschisis.

MANAGEMENT
The risk of rhegmatogenous retinal detachment occurring in a retinoschisis (even with double layer holes) is exceedingly low, so there is no treatment beyond routine monitoring every six to 12 months. If possible, the retinoschisis should be photographed to monitor for progression. Because retinoschisis results in a sharply demarcated visual field defect, the stability can be monitored with a threshold visual field of the central 60 degrees.

CLINICAL PEARLS

While retinoschisis has the potential to enlarge and extend posteriorly and threaten the macula, its progression is extremely slow and may take months to years in order to threaten vision. Thus, a retinal consult is rarely urgent.

Because the RPE is not disrupted by retinoschisis, the RPE does not become hyperplastic and a pigment demarcation line will not form. If a pigment demarcation line is present in a retinoschisis, it should be taken as a sign that there is a concomitant retinal detachment.

The retinoschisis shows no movement or undulation upon eye movement or scleral indentation, whereas a retinal detachment does. Furthermore, scleral indentation will show preservation of the schisis cavity, as opposed to retinal detachment.