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ID naloge: 124 Letnik: 2002 Predmet: oftalmologija
Multifokalna elektroretinografija pri bolnikih z boleznijo makule in zdravih preiskovancih
Avtor: Milena Kaplanovic, Aida Korpic
Mentor: doc. dr. Marko Hawlina
IZHODIŠCE. Multifokalna elektroretinografija (mfERG) je nova metoda, ki omogoca posnetek funkcionalnega zemljevida elektricne aktivnosti na posamezna polja razdeljene mrežnice in s tem natancnejši prikaz njenega majhnega, a za vid izjemno pomembnega dela - makule oz. rumene pege. Doslej uporabljani fotopicna in skotopicna elektroretinografija (fsERG) ter slikovna elektroretinografija (PERG) merita sumacijske bioelektricne odzive dražene mrežnice, zato je njuna uporaba je v diagnostiki lokaliziranih okvar mrežnice omejena. Tako mfERG obeta koristno dopolnitev ostalim elektrofiziološkim metodam, kar je še posebej pomembno v diferencialni diagnostiki makulopatij in locevanje le-teh od nevropatij vidnega živca.
NAMEN. Leta 2001 je Mednarodno združenje za elektrofiziologijo vida (ISCEV) izdalo smernice za snemanje in dolocitev normativov mfERG in dolocilo pogoje, ki bi omogocili boljšo primerljivost rezultatov razlicnih laboratorijev po svetu. Namen naloge je bil izdelati lastne normativne vrednosti za novo metodo na zdravih prostovoljcih v skladu s smernicami ISCEV. Želeli smo tudi oceniti uporabnost mfERG v zgodnji diagnostiki najpogostejših bolezni, ki prizadenejo makulo (Stargardtova makularna distrofija, Bestova viteliformna distrofija, starostna degeneracija makule).
HIPOTEZA. S simultanim multifokalnim draženjem mrežnice in merjenjem odgovorov posameznih polj dosežemo zgodnejše in natancnejše objektivno odkrivanje bolezenskih sprememb makule kot z dosedaj uveljavljenimi elektrofiziološkimi metodami, kot sta fotopicna in skotopicna elektroretinografija in slikovna elektroretinografija.
METODE. V nalogi smo posneli mfERG pri 20 zdravih prostovoljcih (10 žensk in 10 moških, starih od 20 do 28 let; srednja starost žensk 23,9 in moških 25,8 let). Vsi so imeli ocesno ozadje brez bolezenskih sprememb, korigirana vidna ostrina je bila 1,0, nihce ni imel v anamnezi ocesnega obolenja ali poškodbe. Nato smo posneli mfERG na 13 bolnikih z boleznijo makule (9 žensk in 4 moški, starih od 15 do 78 let; srednja starost žensk 47,7 in moških 34,5 let), kot je Stargardtova makularna distrofija, Bestova viteliformna distrofija in starostna degeneracija makule. Bolnikom smo vzeli anamnezo, dolocili vidno ostrino, slikali ocesno ozadje in testirali vidno polje. Narejena je bila tudi fluoresceinska angiografija, lasersko slikanje z avtofluorescenco in posamezne elektrofiziološke preiskave (elektrookulografija, fsERG, PERG). Priprava preiskovancev in tudi nastavitev parametrov sisema Roland Consult, RETIscan sta bili v skladu s smernicami ISCEV. Pri meritvah smo uporabljali nekornealno elektrodo HK. Dražljaj iz 61 šesterokotnikov je bil predstavljen na zaslonu s kotom gledanja 30° na vsaki strani fiksacije. Merili smo amplitudo P1 in njen skalarni produkt, amplitudo N1 ter latenci N1 in P1 v 5 koncentricnih obrocih s središcem v makuli. Pri zdravih preiskovancih smo vsako spremenljivko obdelali z deskriptivno statisticno metodo. Razlike v normativnih vrednostih med levim in desnim ocesom ter med moškimi in ženskami smo ocenjevali s Studentovim testom t (vrednosti p < 0,05 smo imeli za statisticno pomembne).
REZULTATI. Normativne vrednosti so pokazale odgovore relativno visokih amplitud z nizkim koeficientom variacije v primerjavi z ostalimi študijami (122,9 ± 24,2 nV/deg2, KV 19,7%). Pomembnih razlik med spoloma ter levim in desnim ocesom nismo odkrili (p < 0,05). Pri bolnikih so bile nenormalne vrednosti izmerjene predvsem v centralnih 2 obrocih, kar se ujema z lokalizacijo patoloških sprememb. Prav tako smo pri 13 bolnikih ugotovili odvisnost med vidno ostrino in vrednostjo skalarnega produkta amplitude P1 centralnega obroca (koeficient korelacije r = 0,46, p = 0,019). Primerjava meritev mfERG pri bolnikih (26 oci) z normativnimi vrednostmi za centralna 2 obroca je pokazala, da vrednosti amplitude P1 in njenega skalarnega produkta pri 85% odstopajo od normativnih. V centralnem obrocu je bila amplituda N1 znižana pri 61%, latenca N1 je bila podaljšana pri 19%, latenca P1 pa pri 8%. Doslej uporabljane metode so bile manj obcutljive, saj je PERG odstopal od normalnih vrednosti pri 38% in fsERG le pri 11%.
ZAKLJUCKI. S standardizacijo multifokalne elektroretinografije smo v našem prostoru pridobili novo metodo, ki omogoca topografski prikaz funkcije posameznih delov mrežnice. Naši rezultati potrjujejo hipotezo, da je mfERG obcutljivejša od drugih elektrofizioloških metod pri lokaliziranih obolenjih makule. Njena obcutljivost je bila še posebej velika pri obeh najpogostejših distrofijah makule, kjer je pokazala nenormalnosti pri vseh testiranih bolnikih. Nekoliko manj obcutljiva je bila metoda v zgodnjih fazah starostne degeneracije makule. Z mfERG smo pridobili ucinkovito in hitro metodo pri odkrivanju zgodnjih objektivnih znakov bolezni makule.
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[Abstract / English version]
Multifokalna elektroretinografija pri bolnikih z boleznijo makule in zdravih preiskovancih
Author: Milena Kaplanovic, Aida Korpic
Mentor: doc. dr. Marko Hawlina
BACKGROUND. Multifocal electroretinography (mfERG) is a new method for imaging the functional map of electric activity in a retina divided into fields, thus offering a more precise depiction of the very small part of the retina which is of extreme importance for eyesight: the fovea. The Ganzfeld ERG and pattern electroretinography (PERG) methods used to date measure a stimulated retina's sum of bioelectric responses, which limits their applicability in localised retinal disorder diagnosis. Multifocal electroretinography thus offers a useful complement to other electrophysiological methods, which is particularly important in differential diagnostics of maculopathies and their discernment from optic nerve neuropathies.
AIM. In 2001 the International Society for Clinical Electrophysiology of Vision (ISCEV) issued guidelines for the imaging and the definition of normative values for mfERG, thus laying down the conditions that would allow for better comparison of results between laboratories worldwide. The aim of the present paper is to define our own normative values for the new method with healthy volunteers in line with ISCEV guidelines. The authors' aim was also to assess the applicability of mfERG in early diagnosis of the most frequent disorders to the fovea (Stargardt's macular dystrophy, Best macular dystrophy, age related macular degeneration).
HYPOTHESIS. Simultaneous multifocal stimulation of the retina and response measurement in individual fields allow for earlier and more precise objective diagnosis of disease-related alterations to the macula compared against the established electrophysiological methods such as Ganzfeld ERG and pattern electroretinography.
METHODS. The research comprised of mfERG imaging in 20 healthy volunteers (10 males, 10 females, age 20 to 28; mean female age 23.9, mean male age 25.8). All exhibited a fundus without disorders, the corrected visual acuity was of 1.9, none had eye disorders or injuries in their histories. This was followed by mfERG imaging on 13 patients with a disorder of the macula (9 female, 4 male, age 15 to 78; mean female age 47.7, mean male age 34.5), such as Stargardt's macular dystrophy, Best macular dystrophy, age related macular degeneration. The patients' histories were reviewed, their visual acuity determined, their fundus photographed and their visual field tested. Fluorescent angiography, autofluorescent laser scans and individual electrophysiological tests (electro-oculography, Ganzfeld ERG, PERG) were also performed. The preparation of the individuals for testing and the parameter settings on the Roland Consult RETIscan system were carried out in line with ISCEV guidelines. A non-corneal HK electrode was used for the measurements. The stimulus from 61 hexagons was shown on a screen positioned at a 30-degree viewing angle on each fixation side. Measurements were made of the P1 amplitude and its scalar product, of the N1 amplitude, and of the implicit times of P1 and N1 in 5 concentric rings around the fovea. In healthy individuals, every variable was processed using the descriptive statistical method. Differences in normative values between the left and the right eye and between males and females were assessed using the Student t test (values of p < 0.05 were considered as statistically significant).
RESULTS. Normative values resulted in responses with relatively high amplitudes with a low coefficient of variation compared to other studies (122.9 ± 24.2 nV/deg2, KV 19.7%). Significant differences between the left and right eye or between genders were not discovered (p < 0.05). In patients, abnormal values were measured primarily in the 2 central rings, which coincides with the localisation of pathological changes. In 13 patients a correlation between visual acuity and the scalar products of the P1 amplitude in the central ring was discovered (coefficient of correlation r = 0.46, p = 0.019). A comparison of mfERG readings in patients (26 eyes) against normative values for the 2 central ringss showed that P1 amplitude values and their scalar products deviate from normative values in 85% of cases. In the central ring the N1 amplitude was low in 61% of the cases, N1 implicit times were extended in 19% and P1 implicit times in 8% of the cases. Existing methods proved less sensitive, as PERG exhibited deviations from normal values in 38% of the cases, while the Ganzfeld ERG method only exhibited deviations in 11% of the cases.
CONCLUSIONS. The standardisation of multifocal electroretinography offers our environment a new method allowing for the topographic depiction of the functioning of individual retinal parts. Our results confirm the hypothesis that in localised macular disorders mfERG is more sensitive than other electrophysiological methods. Its sensitivity was particularly apparent in both of the most frequent macular dystrophies, where abnormalities were shown in all patients tested. The method was slightly less sensitive in the early stages of age related macular degeneration. Multifocal ERG offers an effective and quick method of diagnosing early objective signs of macular disorders.
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