Idiopathic Macular Hole without Vitreomacular Separation

Purpose: To investigate the clinical features and treatment outcomes of idiopathic full thickness macular hole (FTMH) without vitreomacular separation (VMS). Methods: Consecutive cases of idiopathic FTMH at one tertiary center from January 2013 to April 2020 was retrospectively recruited. They were separated into two groups according to the findings in optical coherence tomography (OCT): FTMH with VMS and FTMH without VMS. Ophthalmic examinations and OCT were performed pre and postoperatively. The clinical findings were compared between two groups. Results: Of the total 124 cases, 15 (12.1 %) were noted as FTMH without VMS with the presence of an attached posterior hyaloid (PH) at macula. The macular hole (MH) size was smaller (276.06 ± 170.10 µm) compared to those with VMS (492.83 ± 209.31 µm) (P < 0.001). The incidence of lamellar hole associated epiretinal proliferation (LHEP) was much higher in this group (13/15, 86.7%), compared to FTMH with VMS (11/109, 10.1%) (P < 0.001). A higher rate of spontaneous closure of MH (13.3%) was also noted in FMTH without VMS (13.3% vs 0.9% in FTMH with VMS, P = 0.040). After operation, the MH closure rate was 93.3%. The postoperative best-corrected visual acuity was not significantly different between two groups (P = 0.098). Conclusions: A small percentage (12.1% in this series) of idiopathic FTMH had no VMS. The completely attached PH along with the high incidence of LHEP implied a tangential traction in FTMH without VMS. The MH size was usually small, and the postoperative outcomes was similar to those of conventional FTMH with VMS.

Effects of Near-surface Composites on Frictional Rolling Contact Solved by a Semi-analytical Model

A semi-analytical model (SAM) to tackle the steady-state elastic frictional rolling contact problem involving composites is presented. Specifically, the frictional rolling contact is categorized into two subtypes, namely normal and tangential problems, and the conjugate gradient method (CGM) is used to figure out the normal pressure and tangential traction. In SAM, the equivalent inclusion method (EIM) is applied to analyze the influence of composites on the matrix, and the displacement disturbance resulting from such composites is added to the total surface displacement, which implements the coupling between surface contact and composites. The accuracy of the proposed model is verified by the finite element model. The effects of composites on the frictional rolling contact behavior are investigated. The results indicate that Young's modulus, as well as the size and location of the composites, are correlated with the distributions of tangential traction, subsurface stresses and the sizes of stick and sliding zones.

Theoretical Studies of Forwarder Productivity with Limited Impact on Soils

Wheeled forest machines currently dominate the logging industry in Russia and in the world. Every year in Russia, the share of machine-made wood harvesting using Scandinavian technology increases, which involves felling trees, delimbing, and bucking them at a swath. Moreover, this technology is used not only for conventional two-machine systems with harvester and forwarder. In some regions of Siberia three-machine systems are gaining popularity. They consist of a feller-buncher, a swath processor, and a forwarder for skidding obtained logs. The issue of increasing the efficiency of forwarders is relevant for the timber industry. Its solving is possible on the basis of a comprehensive assessment of design solutions with the use of modern modeling and process optimization tools at the stage of development design. This approach requires deep theoretical and experimental research and is of great scientific and practical interest. When determining the maximum volume of skidded wood, the following machine limitations are considered: by bearing capacity; by tangential traction force; by the traction of the mover with the soil (tangential traction force should not exceed the traction force of the mover with the driving surface – the soil of the logging site). Besides this, there are recommendations to limit the weight of the skidder with the load, based on the permissible track depth after the first pass of the machine; it is believed that this figure should not exceed 20 cm. This statement is supported by the results of studies of the track development under the cyclic influence of the wheel mover (that is when the forwarder repeatedly passes the same section of the portage). This raises the question of forwarder productivity in the skidding operation with the regard to the track depth limitation. For citation: Burmistrova O.N., Prosuzhih A.A., Khitrov E.G., Kunitskaya O.A., Luneva E.N. Theoretical Studies of Forwarder Productivity with Limited Impact on Soils. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 3, pp. 101–116. DOI: 10.37482/0536-1036-2021-3-101-116

Reducing the soil structure destruction along the rut and increasing the traction properties of the tractor by using the rear grouser of the track link

The traditionally used mixed grouser of the metal track link causes a decrease in the traction qualities of the agricultural tractor. The use of a rear grouser on the track link, in our opinion, will significantly improve the traction properties of an agricultural tractor with a metal track and reduce the soil destruction. When the rear grouser is immersed in the soil, an additional horizontal deformation of the soil occurs, which changes the law of horizontal deformation distribution along the support surface of the trackdrive, which ensures the alignment of the link shares in the implementation of the tangential traction force. This leads not only to a reduction in the trackdrive skidding, but also to a reduction in tractor rolling losses. Comparative tests of the T-4A tractor with a serial track, and a track on which links the front grousers were removed showed that the maximum traction power increases from 59 to 65 kW, the skidding with a hook load of 40 kN decreases from 14.6 to 9.4%, the rolling resistance coefficient decreases from 0.093 to 0.072, eliminates the “scissors” effect, which will reduce the number of erosive-dangerous particles in the track trace to 30...40%, which is 5.6...4.25 times less than in agricultural tractors with a mixed grouser, which confirms the effectiveness of their use.

Vitrectomy With Sequential Internal Limiting Membrane Peeling and Flap Formation in Closure of a Large, Traumatic Macular Hole

Purpose: We report the use of sequential vitrectomy with internal limiting membrane (ILM) flaps in closure of a chronic, large, traumatic macular hole (MH) in a 32-year-old male patient. Methods: The patient underwent vitrectomy using a sequential ILM flap technique. Results: This sequential ILM flap technique resulted in complete closure of the MH and improvement in visual acuity. In this case, a second ILM flap procedure allowed for successful closure of a traumatic MH. Conclusions: This case suggests that the MH's closure may have been facilitated by both relief of tangential traction on the retina as well as glial tissue proliferation from presence of the ILM flap.

Differences in the presentation of stage 1 macular holes illustration by optical coherence tomography

Objective: To present two different phases of progression of Gass stage 1 foveolar detachment to lamellar or full-thickness macular holes revealed with spectral domain optical coherence tomography. Design: This is an observational study. Participants: The medical records of four patients (four eyes) with foveolar detachment that had evolved into stage 1 macular holes were compared. The patients manifested neither co-existing myopia nor any other ocular pathology. Methods: At each consultation, best-corrected visual acuity, dilated fundus examination, and spectral domain optical coherence tomography were performed to ascertain whether the foveolar detachment was associated with posterior vitreal detachment. Results: In two of the eyes, and at an early phase of the disease, an incomplete posterior vitreal detachment and vitreal adhesion at the head of the optic nerve were observed. In the other two cases, the traction was not antero-posterior but tangential and had been effected by thickening of the inner limiting membrane or by the presence of a discrete epiretinal membrane in the papillomacular area; the posterior vitreal detachment was complete. In the former two cases and in one of the latter, the foveolar detachments had progressed to full-thickness macular holes. The visual acuities were better in the latter than in the former two eyes. Conclusion: Two different pathological mechanisms appear to underlie the formation of macular holes: The optical coherence tomography–guided classification of Gass stage 1 macular hole as an antero-posterior traction with a triangular foveolar detachment has to be distinguished from a tangential traction and a complete posterior vitreal detachment. Tangential traction is typically associated with a more dome-shaped or irregular foveolar detachment and a hyper-reflective band at the vitreoretinal interface.

Reconstructing Foveola by Foveolar Internal Limiting Membrane Non-Peeling and Tissue Repositioning for Lamellar Hole-Related Epiretinal Proliferation

Differences in the pathogenesis and clinical characteristics between lamellar macular hole (LMH) with and without LMH-associated epiretinal proliferation (LHEP) can have surgical implications. This study investigated the effects of treating LHEP by foveolar internal limiting membrane (ILM) non-peeling and epiretinal proliferative (EP) tissue repositioning on visual acuity and foveolar architecture. Consecutive patients with LHEP treated at our institution were enrolled. The eyes were divided into a conventional total ILM peeling group (group 1, n = 11) and a foveolar ILM non-peeling group (group 2, n = 22). In group 2, a doughnut-shaped ILM was peeled, leaving a 400-μm-diameter ILM without elevated margin over the foveola after EP tissue repositioning. The EP tissue was elevated, trimmed, and inverted into the LMH. Postoperatively, the LMH was sealed in all eyes in group 2, with significantly better best-corrected visual acuity (−0.26 vs −0.10 logMAR; p = 0.002). A smaller retinal defect (p = 0.003), a more restored ellipsoid zone (p = 0.002), and a more smooth foveal depression (p < 0.001) were achieved in group 2. Foveolar ILM non-peeling and EP tissue repositioning sealed the LMH, released the tangential traction, and achieved better visual acuity. The presumed foveolar architecture may be reconstructed surgically. LMH with LHEP could have a combined degenerative and tractional mechanism.

Modern notions about the tactics of treatment of patients with non-full thickness macular holes: to observe or to operate?

In this review, the opinions of different authors on the problem of non-full thickness macular holes are discussed in detail. Currently, there are three different approaches to the management of this condition. Dynamic observation allows assessing the degree of their progression, to determine some or other anatomical indicators which influence the functional state of the retina and visual function. Pharmacological vitreolysis in some cases allows eliminating vertical and tangential traction in a least invasive mannor. To resolve this problem in a radical way is possible by surgical treatment posterior vitrectomy, but this is also related to certain surgical risks, and does not always lead to an increase in visual acuity. As a rule, it is recommended to patients with a significant decrease in visual acuity. Currently, indications for surgical treatment of patients with high visual function are ambiguous.