Degenerative retinoschisis
Synonyms
Degenerative retinoschisis is also known as acquired degenerative retinoschisis.
The terms senile or age-related degenerative retinoschisis are also used, but these names do not correctly describe this condition as it can also occur in the third decade of life (20-30 years).
Definition
Degenerative retinoschisis is an acquired idiopathic condition characterized by gradual peripheral splitting of the retinal layers, typically between inner nuclear and outer plexiform layer. It produces a well-circumscribed, transparent dome-shaped elevation of the inner retina that extends anteriorly towards the ora serrata.
Degenerative retinoschisis was first reported by M. Bartels in 1933. Two histological forms of the disease have been described by B. R. Straatsma and R.Y. Foos in 1973.
Epidemiology, onset & clinical features
Epidemiology
Degenerative retinoschisis affects about 5-7% of the adult population. Occurrence in up to 22% of individuals older than 40 years has been reported. Both genders are equally affected. No ethnical predisposition has been found.
Classification
Based on histopathological criteria, two forms of degenerative retinoschisis have been described:
- typical (flat) retinoschisis characterized by: adhesion of cystic lesions as a result of degeneration of neuroretinal and glial supporting elements within areas of peripheral cystoid degeneration; deep separation of the retina into an inner and an outer layer; the inner layer contains the inner limiting membrane, retinal vessels, and inner plexiform layer, whereas the outer layer has portions of the outer plexiform, outer nuclear, and photoreceptor layers.
- reticular (bullous) retinoschisis characterized by: an extremely thin inner wall consisting of inner limiting membrane, remnants of the nerve fiber layer, attenuated blood vessels, and complete loss of the supporting radial pillars.
Clinical features
The disease is asymptomatic in majority of cases. Advanced cases may present a large peripheral visual field defect corresponding to the area of retinoschisis. Unselected clinical series reveal a bilateral occurrence in approximately 80% of cases, with typically symmetrical presentation between the eyes. The schisis is most frequently located in the inferior temporal quadrant, has a discrete border and is immobile. There is no associated pigmentation of the retinal pigment epithelium or vitreous. Blood vessels on the inner retinal layer may be white and sheathed, and white ‘snowflakes' may be visible.
Single or multiple retinal holes (outer retinal holes being more common than inner retinal breaks) are rare and occur in less than 20% of cases, creating a risk for secondary retinal detachment. Retinal detachments associated with retinoschisis are two types: a localized, relatively stable and asymptomatic form usually presenting with outer retinal holes only; a rapidly progressive form presenting with retinal breaks in both layers. The asymptomatic form is much more frequent than the symptomatic one (ratio of about 180:1). Retinoschisis is responsible for less than 2.5% of all rhegmatogenous retinal detachments. Tractional retinal tears in retinoschisis are extremely rare.
The hallmark feature of the disease is foveal schisis (retinal splitting) though over time this may become less distinct. More than 50% of patients have some peripheral retinoschisis (mostly in the inferotemporal region) that can vary from shallow schisis to marked elevation in the inner leaflet over a large retinal area. Breaks occur within the inner layer varying from small holes to large tears. Vessels crossing between the walls of the schisis may be unsupported and at risk of hemorrhage. Additional peripheral changes may include pigmentation, which can resemble retinitis pigmentosa, sublinear retinal fibrosis, white retinal flecks and vascular attenuation or sheathing. Some patients present an inner retinal reflex resembling a tapetal reflex. XLRS may progress to retinal detachment in 5-22% of affected individuals, including infants with severe retinoschisis. Four to 40% of individuals with XLRS may develop vitreous hemorrhage.
Carrier females almost always have normal visual function and normal electroretinogram (ERG). Rarely, white flecks or areas of schisis in the peripheral retina can be present. So far, affected females have been reported only twice in the literature, one of these report describing females with XLRS from a highly consanguineous Columbian family.
Etiology and pathogenesis
The etiology of degenerative retinoschisis is poorly understood. Genetic, vascular, nutritional, or tractional mechanisms do not seem to be implicated in the pathogenesis of the condition.
Diagnosis
Diagnosis is based on ophthalmoscopy with scleral depression and contact lens examination. The fellow eye should also be examined.
Differential diagnosis
Degenerative retinoschisis can easily be confused with retinal detachment (rhegmatogenous and exudative). Differentiation between these two conditions is extremely important since retinal detachment almost always requires treatment, while retinoschisis usually does not (or only occasionally).
The differential diagnosis between retinoschisis and retinal detachment is usually made on the basis of clinical examination. Clinically, retinoschisis is more transparent, less mobile, has less surface wrinkling, and exhibits less underlying retinal pigment epithelial atrophy than full-thickness retinal detachment. Optical coherence tomography can be used as an additional diagnostic method if differential diagnosis cannot be made clinically.
X-linked juvenile retinoschisis and secondary retinoschisis (due to diabetic retinopathy, retinopathy of prematurity) should also be considered.
Management
Most cases of retinoschisis are innocuous and do not affect central vision. Treatment (laser surgery, incisional surgery) should be considered only in symptomatic cases that threaten the macula and in cases with progressive retinal detachment.
Observation for asymptomatic cases is indicated. The frequency of the routine review depends upon the lesion size, the proximity to the macula and the presence or absence of symptoms (6-24 month intervals). Patients should be advised to return urgently if they experience retinal detachment symptoms, such as increased floaters or flashing lights or the presence of a curtain or shadow in their field of vision.
Follow-up and prognosis
The disease has usually a very-slowly progressive course. Patients usually remain stable for years.
References
Lewis H. Peripheral retinal degenerations and the risk of retinal detachment. Am J Ophthalmol. 2003 Jul;136(1):155-60.
Retina: Color Atlas and Synopsis of Clinical Ophthalmology, A. Ho, G. C. Brown, C. D.
Regillo J. Arch McNamara, J. F. Vander, F. M. Recchia. McGraw-Hill Medical, 2003
Contributors
Katia Marazova, PhD (June 2010), Prof. José Alain Sahel, MD, PhD and Dr Isabelle Audo, MD, PhD
Disclaimer: This document contains information based on published scientific articles and is for educational purposes only. It is in no way intended as a substitute for qualified medical professional help, advice, diagnosis or treatment
