[Possibilities of treating retinal diseases in patients with damaged retinal pigment epithelium]

Possibilities of an experimental damaging effect on the retinal pigment epithelium

PURPOSE

To simulate the damaging effect on retinal pigment epithelium (RPE) in an experiment studying the effect of human neuronal precursors (NPs).

MATERIAL AND METHODS

The study was carried out on 31 rabbits (31 eyes) of the Chinchilla breed, which were divided into 3 groups: the 1^st group received a subretinal injection of balanced saline solution (BSS); the 2^nd group - subretinal injection of BSS with vitrectomy, displacement of the injection bladder away from the injection site using a perfluororganic compound (PFOC) and laser coagulation; the 3^rd group - subretinal injection of a culture of NPs using the same method as in the group 2. All rabbits were observed for 21 days using ophthalmoscopy, optical coherence tomography (OCT) and autofluorescence (AF).

RESULTS

In the 1^st group, 4 out of 5 rabbits were observed to have total retinal detachment and vitreoretinal proliferative processes in the early postoperative period after subretinal injection of the BSS. In the 2^nd group, OCT and AF revealed atrophy of the outer and inner layers of the retina as well as disorganization of the photoreceptors-RPE-Bruch's membrane complex in the area of injection on the 21 day after the operation. In the 3^rd group, the OCT data obtained during the 21 days of observation showed that a hyperreflective zone at the level of the RPE-Bruch's membrane complex corresponding to the NPs injection site was preserved, while there was a partial loss of the outer retinal layers - but of a smaller volume compared to the BSS injection. The suggested method of subretinal injection led to a reduced number of complications: in the 1^st group, postoperative complications amounted to 80%, while in the 2^nd and 3^rd groups - 45%.

CONCLUSION

The study proposes a new method for retinal injection of BSS, which can help reduce RPE degeneration patterns and possible postoperative complications, thus increasing research efficiency. Subretinal injection of a culture of neuronal precursors derived from human induced pluripotent stem cells (iPSCs) in an experiment can serve as a universal model for studying the survival and integration of stem cells.

[Avascular retinal pigment epithelium detachments in age-related macular degeneration]

Retinal pigment epithelium detachment (PED) is a pathological condition in which retinal pigment epithelium is separated from the underlying Bruch's membrane due to the formation of a fibrovascular membrane, drusenoid material, accumulation of fluid and/or blood. Six types of RPE detachments have been determined: pseudovitelliform, detachments associated with drainage drusen, serous, vascular and hemorrhagic, as well as PED associated with vascular retinal anomaly. The drusenoid PED is always avascular, the drusenoid material is contained between the RPE and Bruch's membrane. It was first described by Casswell in 1985. Ophthalmoscopy of the fundus shows a yellow-white cellular structure in the subretinal space, sometimes containing a patch of pigment, with an uneven surface, clear boundaries and a wavy edge. Serous PED is larger in area and prominence than drusenoid, characterized by the presence of a hyporeflective area under the detached RPE, over the area of more than 50% of the total area of detachment. Ophthalmoscopy shows a transparent yellow lesion in the subretinal space, sometimes brown-tinted, with clear boundaries and dome-shaped prominence. True serous PED is avascular (combination of choroidal neovascularization and serous PED will be discussed in the article about vascularized PED).

[Differential diagnosis of various types of fluids on the eye fundus in patients with age-related macular degeneration]

Age-related macular degeneration (AMD) is a leading cause of vision loss both worldwide and in Russia. A distinctive feature of the exudative form of AMD is the presence of choroidal neovascularization (CNV) as a result of pathological angiogenesis of the choroid. With the introduction of optical coherence tomography (OCT) - a non-invasive imaging technique - it has become possible to monitor CNV activity. In the development of CNV, OCT can reveal three types of fluid localization: intraretinal fluid (IRF), subretinal fluid, fluid under retinal pigment epithelium (RPE). Exudative IRF is characterized by the presence of round and/or oval space. This type of fluid is characterized by good response to anti-VEGF therapy. Degenerative IRF («cystoid degeneration») is characterized as a small, clearly defined hyporeflective spaces above the area with altered RPE not responding to anti-VEGF therapy. Thus, early diagnosis of AMD and detection of «new activity» after therapy with antivascular endothelial growth factor (anti-VEGF) by comparing distribution of the fluid in SD-OCT are critical to maintaining or restoring the best possible visual acuity in patients with this disease.

[New possibilities in the treatment of Stargardt disease]

Stargardt disease is a hereditary retinal dystrophy associated with mutations in the ABCA4 gene. Currently, no etiopathogenetic drugs nor treatment methods for Stargardt disease have completely passed clinical trials. The review summarizes experimental and clinical studies of drugs aimed at reducing the accumulation of vitamin A dimers, lipofuscin, complement inhibition and RPE regeneration by stem cell transplantation, as well as gene therapy studies with intravitreal vector injection of the ABCA4 functional gene.

[Morphological and functional indicators of retinal pigment epithelium and photoreceptor apparatus in inherited retinal diseases]

PURPOSE

To evaluate the relationship between the morphological and functional parameters of retinal pigment epithelium (RPE) and photoreceptors (PR) in inherited retinal diseases (IRD).

MATERIAL AND METHODS

The study included 52 patients (104 eyes), 23 of them with Stargardt Disease (STGD), 19 with cone-rod dystrophy (CRD), 10 with retinitis pigmentosa/pigmentary abiotrophy (RP) of comparable disease durations. All patients underwent standard and additional ophthalmological examination: fundus autofluorescence (AF), spectral optical coherence tomography (OCT), computer perimetry (CP), electro-oculography (EOG), Ganzfeld electroretinography (gERG).

RESULTS

Comparison of the groups of IRD patients and groups according to the degree of RPE damage with the control group revealed an increase in differences in the EOG and gERG indicators as the area and depth of damage to the RPE and PR progressed. The patterns of changes in RPE and PR, the frequency of their occurrence with IRD in this patient sample are described. A moderate correlation was found between the amount of RPE loss and EOG light rise, as well as between the defect of the ellipsoid zone and the amplitude of α- and β-waves, the latency of β-wave of the gERG. Some patients showed a mismatch between a small defect of the ellipsoid zone and RPE with significant damage to the visual field and reduction of the EOG and gERG indicators. The obtained electrophysiological indicators revealed pathological changes in RPE and PR, more significant and widespread in some cases than it was shown with visualization methods. Weak and moderate correlations between visual acuity, and RPE damage and light sensitivity index with loss of ellipsoid zone were calculated.

CONCLUSIONS

Modern methods of retinal examination can help obtain complete and versatile picture of morphological and functional state of the retina in IDR that supplement each other. EOG and gERG have capability to determine the degree of RPE and PR functions impairment including those cases when morphological studies are not sufficiently informative.