Retinal Temperature Determination Based on Photopic Porcine Electroretinogram

Objective: Subthreshold retinal laser therapy (SLT) is a treatment modality where the temperature of the retinal pigment epithelium (RPE) is briefly elevated to trigger the therapeutic benefits of sublethal heat shock. However, the temperature elevation induced by a laser exposure varies between patients due to individual differences in RPE pigmentation and choroidal perfusion. This study describes an electroretinography (ERG)-based method for controlling the temperature elevation during SLT. Methods: The temperature dependence of the photopic ERG response kinetics were investigated both ex vivo with isolated pig retinas and in vivo with anesthetized pigs by altering the temperature of the subject and recording ERG in different temperatures. A model was created for ERG-based temperature estimation and the feasibility of the model for controlling SLT was assessed through computational simulations. Results: The kinetics of the photopic in vivo flash ERG signaling accelerated between 3.6 and 4.7%/degrees C, depending on the strength of the stimulus. The temperature dependence was 5.0%/degrees C in the entire investigated range of 33 to 44 degrees C in ex vivo ERG. The simulations showed that the method is suitable for determining the steady-state temperature elevation in SLT treatments with a sufficiently long laser exposure and large spot size, e.g., during > 30 s laser exposures with > 3 mm stimulus spot diameter. Conclusions: The described ERG-based temperature estimation model could be used to control SLT treatments such as transpupillary thermotherapy. Significance: The introduced ERG-based method for controlling SLT could improve the repeatability, safety, and efficacy of the treatment of various retinal disorders.Peer reviewe

Jalkapalloilijoiden hamstring-lihasvammojen ennaltaehkäisy harjoittelun keinoin : Harjoitusohjelma Oulu Nice Soccerin B18-juniorijoukkueelle

Jalkapallo on maailman suosituin urheilulaji. Sen harrastamisella on paljon positiivisia terveysvaikutuksia, mutta lajin luonne tuo mukanaan myös korkean loukkaantumisriskin. Lihasvammat kattavat noin kolmasosan kaikista jalkapalloilijoiden vammoista ja niistä lähes 40% syntyy hamstring-lihaksiin. Hamstring-lihasvammat ovat paitsi yleisiä, niin myös uusiutumisherkkiä, minkä vuoksi niiden ennaltaehkäiseminen on ensiarvoisen tärkeää. Yhteistyökumppaninamme toimi Oulu Nice Soccerin B18-juniorijalkapallojoukkue. Joukkueen pelaajat ovat 16−18-vuotiaita ja he tavoittelevat menestystä sekä joukkueena että yksilöinä. Loukkaantumisille ei siis ole sijaa, sillä niillä on negatiivinen vaikutus pelaajien kehitykseen, mikä heijastuu negatiivisesti myös joukkueen menestysmahdollisuuksiin. Opinnäytetyössämme perehdyimme jalkapalloilijoiden hamstring-lihasvammoja ennaltaehkäiseviin keinoihin fysioterapian näkökulmasta. Selvitimme hamstring-lihasvammoille altistavat riskitekijät ja vammojen syntymekanismit sekä mihin harjoittelussa tulee kiinnittää huomiota, jotta näitä vammoja voidaan ennaltaehkäistä. Tekemämme laajan kirjallisuuskatsauksen pohjalta laadimme yhteistyökumppanimme käyttöön harjoitusohjelman, jonka tavoitteena on hamstring-lihasvammojen ennaltaehkäiseminen. Lisäksi koulutimme joukkueen pelaajia ja valmentajia pitämällä heille luennon, jonka tavoitteena oli lisätä heidän tietouttaan hamstring-lihasvammoista, jotta he ymmärtäisivät ennaltaehkäisyn tärkeyden. Harjoitusohjelmaan valitsemamme harjoitteet ohjasimme pelaajille kolmessa harjoittelujaksossa, jotka etenivät progressiivisesti ohjatusta harjoittelusta kohti omatoimista harjoittelua. Tavoitteena harjoittelujaksoilla oli opettaa pelaajille oikeat suoritustekniikat sekä varmistaa, että pelaajilla on tietotaito omatoimiseen ja tavoitteelliseen harjoitteluun. Opinnäytetyön henkilökohtaisina oppimistavoitteinamme oli kehittää omaa opetus- ja ohjausosaamistamme sekä ryhmä- että yksilötilanteissa ja syventää omaa tutkimus-, päättely- ja menetelmäosaamistamme. Opinnäytetyöprosessin toteuttaminen kehitti omaa ammatillista osaamistamme sekä loi pohjan vastaavanlaisten projektien suunnittelemiseen ja toteuttamiseen tulevaisuudessa. Opinnäytetyössä laatimamme harjoitusohjelman keskeinen tavoite oli ennaltaehkäistä hamstring-lihasvammojen syntyminen, mutta tämän tavoitteen saavuttamisen mittaaminen ei ollut näin lyhyen prosessin puitteissa mahdollista. Tämä avaakin tuleville opinnäytetyön tekijöille jatkotutkimusmahdollisuuden, jossa voisi mitata laatimamme harjoitusohjelman vaikuttavuutta hamstring-lihasvammojen ennaltaehkäisijänä.Football is the most played sport in the world. Playing football has a lot of beneficial health effects but the rate of injuries is comparatively high as well. Muscle strain injuries account for approximately one third of all injuries in football. Almost 40% of these injuries are hamstring strain injuries. Preventing hamstring strain injuries is especially important as the injuries are common, and the rate of recurrence is high. Our cooperation partner was Oulu Nice Soccer’s B18 youth team. The players in the team are 16−18 years old and they aim for success both as a team and individually. Thus, there is no room for injuries as they have negative effect on players’ ability to perform which also affects on the team’s chances to succeed. In our bachelor’s thesis we made our selves familiar with the training methods which have preventive effect on hamstring strain injuries in football. We researched the risk factors and the injury mechanisms for hamstring strain injuries. We also figured out what are the key points to focus on in training so that these injuries can be prevented. Based on the extensive literature review we conducted, we created a training programme for the cooperation partner’s use to prevent hamstring strain injuries. In addition, we educated the team by delivering a lecture which aimed to increase the team’s knowledge of hamstring strain injuries so that they would understand why it is important to prevent these injuries. The exercises we had chosen to the training programme were instructed to the players in three training periods that proceeded progressively from supervised training towards independent training. The aim within these training periods was to teach the correct techniques to the players and to make sure the players have the sufficient know-how to proceed the training independently and goal-directedly. Our personal learning objectives during the thesis were to improve our teaching and guiding skills both in group and individually. Executing the thesis improved our skills as professionals and build a foundation for us to implement and execute similar projects in the future. The main goal of the training programme we created was to prevent hamstring strain injuries. However, it was not possible for us to evaluate if we accomplished this goal because of the limited time we had. There is a need for future research to evaluate if the training programme has had influence on the occurrence rate of hamstring strain injuries

In vivo monitoring of mouse retinal temperature by ERG photoresponses

Non-damaging heating of the retina and RPE provides a promising treatment for retinal diseases. However, the lack of proper control over the temperature hinders the development of safe and repeatable procedures. Here, we demonstrate with mice a non-invasive method for estimating the temperature changes in the retina and the RPE during a heating procedure. The method is based on monitoring the temperature dependent properties of retinal photoresponses recorded by electroretinography (ERG). In this study, our aim was to investigate the feasibility of ERG signal for retinal temperature estimation, utilizing a-wave and b-wave kinetics as the source of temperature information. We quantified the temperature dependencies of photoresponse kinetics and developed two linear regression models between the temperature and the photoresponse features, enabling temperature estimation. With the first model, based on the a-wave of a single photoresponse, the RMS error obtained for retinal temperature estimation was <0.9 °C. The second model, applying the b-waves of five dim flash responses, an RMS error of <0.7 °C was achieved. In addition, we tested the sensitivity of the method to small changes in light stimulus strength and investigated suitable stimulus intervals for continuous retinal temperature monitoring. The proposed method provides a convenient technique for monitoring mouse retinal and RPE temperature with ERG recording when studying controlled retinal heating. Similar temperature dependencies exist in human ERG suggesting that this approach could also be applicable in clinical heating treatments.Peer reviewe

A Novel Method for Mouse Retinal Temperature Determination Based on ERG Photoresponses

This study introduces a novel retinal temperature determination method based on the temperature dependent properties of photoresponses recorded by electroretinography (ERG). The kinetics and amplitudes of ERG photoresponses depend on retinal temperature. Additionally, raising retinal temperature increases the probability of long-wavelength photon absorption, which manifests as temperature dependence of photoreceptor sensitivity. In this study we extract a number of features that represent these properties from the a- and b-waves of mouse ex vivo ERG flash responses and construct three multivariable regression models between temperature and the selected features. The performance of these models was evaluated against a separate test dataset and for two of the models, an RMS temperature determination error of less than 0.50 °C could be reached. Our results demonstrate that the method can be successfully used for reliable retinal temperature determination ex vivo. The method, reflecting the temperature of distal retina, can be applied also in the estimation of retinal pigment epithelium temperature.Peer reviewe

Induction of heat shock protein 70 in mouse RPE as an in vivo model of transpupillary thermal stimulation

The induction of heat shock response in the macula has been proposed as a useful therapeutic strategy for retinal neurodegenerative diseases by promoting proteostasis and enhancing protective chaperone mechanisms. We applied transpupillary 1064 nm long-duration laser heating to the mouse (C57Bl/6J) fundus to examine the heat shock response in vivo. The intensity and spatial distribution of heat shock protein (HSP) 70 expression along with the concomitant probability for damage were measured 24 h after laser irradiation in the mouse retinal pigment epithelium (RPE) as a function of laser power. Our results show that the range of heating powers for producing heat shock response while avoiding damage in the mouse RPE is narrow. At powers of 64 and 70 mW, HSP70 immunostaining indicates 90 and 100% probability for clearly elevated HSP expression while the corresponding probability for damage is 20 and 33%, respectively. Tunel staining identified the apoptotic regions, and the estimated 50% damaging threshold probability for the heating (ED50) was ~72 mW. The staining with Bestrophin1 (BEST1) demonstrated RPE cell atrophy with the most intense powers. Consequently, fundus heating with a long-duration laser provides an approachable method to develop heat shock-based therapies for the RPE of retinal disease model mice.Peer reviewe