Retinal detachment: pathogenesis

Pathogenesis of rheumatogenic retinal detachment

Regmatogenic retinal detachment occurs annually in approximately 1 case per 10000 population, in 10% of cases it is bilateral. Retinal ruptures, which are the cause of retinal detachment, can appear due to the interaction: dynamic bitreoretinal traction, predisposing dystrophy at the periphery of the retina. Myopia also plays a significant role.

Dynamic vitreoretinal traction

Pathogenesis

Synchisis is the dilution of the vitreous body. In the presence of synchysis in some cases, holes appear in the thinned cortical part of the vitreous body, which is located above the fovea. The liquefied substance from the center of the vitreal cavity passes through this defect into a freshly formed retrogialoid space. This leads to a hydrodissection of the posterior hyaloid surface from the inner border membrane of the sensory retina up to the posterior boundary of the vitreous base. The remaining dense vitreous body descends below and the retrogialoid space completely remains occupied by the diluted substance. This process is called acute rhematogenous posterior vitreal detachment with omission. The probability of an acute posterior vitreal detachment increases with age and in the presence of myopia.

Complications associated with acute posterior vitreal separation

They depend on the strength and size of the vitreoretinal fusion present.

• Absence of complications is typical for the majority of cases of weak vitreoretinal fusion.
• Retinal tears appear in about 10% of cases as a result of traction of powerful vitreoretinal adhesions. Discontinuities in combination with acute posterior vitreal abruption are usually U-shaped, localized in the upper half of the fundus and are often accompanied by vitreal hemorrhages as a result of breakage of peripheral blood vessels. From the formed rupture, the liquefied retrogialoid fluid can freely penetrate into the subretinal space, so preventive laser coagulation or rupture cryotherapy reduces the risk of detachment of the retina.
• Separation of peripheral blood vessels leading to intralesional hemorrhages without the formation of retinal ruptures.

Symptoms of peripheral retinal dystrophy

Approximately 60% of ruptures appear on the periphery of the retina and cause specific changes. These changes can be associated with spontaneous breakage of pathologically thinned retina with subsequent formation of holes or may cause retinal rupture in the eyes with acute posterior detrimental detachment. Retinal holes are usually smaller than rills and less often lead to detachment of the retina.

Lattice dystrophy

It occurs in 8% of the world's population and in 40% of cases with retinal detachment. It is the main cause of retinal detachment in myopia in young people. Changes in the type of "lattice" are often found in patients with the syndromes Marfan, Stickler and Ehlers-Danlos, which are associated with a high risk of retinal detachment.

Symptoms

• a typical "lattice" consists of strictly limited, peripheral, spindle-shaped areas of retinal thinning, most of which are located between the equator and the posterior border of the base of the vitreous. "Lattice" is characterized by a violation of the integrity of the internal border membrane and various atrophy of the underlying sensory retina. The changes are usually bilateral, more often localized in the temporal half of the retina, mostly from the top, rarely - in the nasal, from below. A characteristic feature is a branched network of thin white strips in the islets formed as a result of PES disturbances. Some "latticular" dystrophies may resemble "snowflakes" (the remains of degenerative changes in Muller cells). The vitreous over the "lattice" is diluted, and along the edges of the dystrophy it forms dense adhesions;
• The atypical "lattice" is characterized by radially oriented changes that extend to the peripheral vessels and can continue back to the equator. This type of dystrophy usually occurs with Stickler syndrome.

Complications

Absence of complications is observed in the majority of patients, even in the presence of small "holey" ruptures, which are often found in the islets of "latticular" dystrophy.

Retinal detachment associated with atrophic "perforated" ruptures, mainly occurs with myopia in young patients. They may have no symptoms-precursors of acute posterior detrimental detachment (photopsy or floating opacities), and the leakage of subretinal fluid usually occurs more slowly.

Retinal detachments, caused by traction ruptures, can be detected in the eyes with an acute posterior vitreal detachment. Tractional ruptures usually develop along the posterior edge of the "latticular" dystrophy as a result of dynamic traction in the region of powerful vitreoretinal fusion. Sometimes a small area of the "lattice" can be determined on the valve of the retinal rupture.

Dystrophy by the "snail trace" type

Symptoms: clearly defined circles of dystrophy in the form of densely packed "snowflakes", giving the periphery of the retina the appearance of a white ice pattern. Usually exceed the length of the islets of "latticular" dystrophy. Although the dystrophy of the "snail trace" is associated with the dilatation of the vitreous humor covering it, a significant visceral traction in the region of its posterior border is rarely observed, so traction U-shaped ruptures almost never occur.

Complications include the formation of "holey" ruptures, which can lead to detachment of the retina.

Degenerative retinosis

Retinoschisis is a separation of the sensory retina into two layers: the outer layer (choroidal) and the inner (vitreal) layer. There are 2 main types: degenerative, congenital. Degenerative retinosis is found in about 5% of the world's population over the age of 20, mostly with hypermetropia (70% of patients are hypermetropic) and almost always asymptomatic.

Classification

• typical, splitting occurs in the outer plexiform layer;
• reticular, occurs less frequently, splitting occurs at the level of the layer of nerve fibers.

Symptoms

• Early changes usually cover the extreme lower temporal periphery in both eyes, manifesting itself in the form of extensive sections of mild-cystic dystrophy with some elevation of the retina.
• Progression can appear around the circumference, up to full coverage of the periphery of the retina. A typical rethiosis is usually anterior to the equator, while the reticiosis may extend posteriorly from it.
• On the surface of the inner layer, changes can be detected in the form of "snowflakes", characteristic changes in the vessels according to the type of the symptom of the "silver wire" or "case," and through the cleavage cavity ("schizis") a ragged gray-white flap can pass.
• The outer layer looks like a "broken metal" and is manifested by the phenomenon of "white with pressure".

For retinoschisis, in contrast to retinal detachment, stability is characteristic.

Complications

• Absence of complications is typical for most cases with a favorable course.
• Discontinuities may appear in the reticular form. The ruptures of the inner layer are small, rounded, while the rarer ruptures of the outer layer are large, with wrapped edges and are located behind the equator.
• Retinal detachment is very rare, but it can appear if there are gaps in both layers. With ruptures in the outer layer, detachment of the retina, as a rule, does not appear, since the liquid inside the "schizis" has a viscous consistency and can not quickly infiltrate into the subretinal space. However, sometimes a liquid can dilute and penetrate through the gap into the subretinal space, raising a limited area of detachment of the outer retinal layer, which is usually within the limits of retinoschisis.
• Vitreal hemorrhages are uncharacteristic.

"White without pressure"

Symptoms

A) "white with pressure" - a translucent grayish retina change caused by sclerocompression. Each site has a certain configuration that does not change when the sclerocompressor moves to the neighboring area. This phenomenon is often observed in normal, as well as along the posterior border of the islets of "latticular" dystrophy, dystrophy as a "snail trail" and the outer layer of acquired retinosis;

B) "white without pressure" has a similar pattern, but manifests itself without sclerocompression. At the general or common inspection the normal site of a retina surrounded by "white without pressure", can be mistaken for a flat "holey" rupture of a retina.

Complications. Giant tears sometimes develop along the back border of the site with "white without pressure".

Significance of myopia

Although myopia affects about 10% of the world's population, more than 40% of all retinal detachments occur in myopic eyes. The higher the refraction, the higher the risk of detachment of the retina. The following interrelated factors predispose to retinal detachments in myopic eyes:

• "Latticular" dystrophy is more common in medium-degree myopia and can lead to normal and "holey" ruptures.
• Dystrophy of the "snail trace" type occurs in myopic eyes and may be accompanied by "holey" ruptures.
• Diffuse chorioretinal atrophy can lead to small "holey" ruptures in high degree myopia.
• A macular rupture can cause retinal detachment in high degree myopia.
• Dystrophy of the vitreous body and posterior vitreal detachment are often found.
• The loss of the vitreous humor during cataract surgery, especially if errors were committed during the operation, is associated with subsequent retinal detachment in approximately 15% of cases of myopia above 6 dptr; The risk is much higher with myopia above 10 Dpt.
• Posterior capsulotomy is associated with a high risk of retinal detachment in myopic eyes.

[1], [2], [3], [4], [5], [6], [7], [8]