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Experimental vitreoretinal surgery in the rabbit eye - electrophysiology and morphology

Gjörloff, Karin LU (2006)
Abstract
The field of vitreoretinal surgery has expanded greatly over the last decades. A continuous refinement of surgical methods and instruments has increased the number of treatable retinal disorders. Vitrectomy, retinectomy and laser treatment are all part of the modern surgical arsenal. In order to further develop and refine these methods, and also to improve the knowledge of the mechanisms behind their efficiency, standardized animal models including functional and histological evaluations are of great value. Full-field electroretinography (ERG) and multifocal electroretinography (mfERG) are methods by which electrical activity from neurons in the retina can be measured. ERG measures the total response of cones and/or rods after light... (More)
The field of vitreoretinal surgery has expanded greatly over the last decades. A continuous refinement of surgical methods and instruments has increased the number of treatable retinal disorders. Vitrectomy, retinectomy and laser treatment are all part of the modern surgical arsenal. In order to further develop and refine these methods, and also to improve the knowledge of the mechanisms behind their efficiency, standardized animal models including functional and histological evaluations are of great value. Full-field electroretinography (ERG) and multifocal electroretinography (mfERG) are methods by which electrical activity from neurons in the retina can be measured. ERG measures the total response of cones and/or rods after light stimulation whereas mfERG measures the focal cone-mediated activity from the central part of the retina. In this thesis the ERG and mfERG protocols were adapted and standardized for the rabbit eye. Reliable and reproducible ERG readings were obtained, and combining the technique with immunohistochemistry, the retinal impact of various surgical procedures in the rabbit eye was studied. After vitrectomy, ERG recordings displayed reduced amplitudes up to 4 weeks postoperatively, with rods more affected than cones. A general glial fibrillary acidic protein (GFAP) labeling throughout the retina was noted postoperatively, with a more intense labeling in eyes where a low cutting rate of the vitrectomy instrument had been used, implying a higher degree of traumatic impact compared with high-speed settings. An experimental method was also developed for performing a retinectomy in the rabbit eye, where a part of the retina was surgically removed. Using the mfERG, it was shown that the procedure induces a general reduction of the central retinal function for 1 month. After this time, retinal function was gradually restored except for in the area of removed retina. The study thus showed that lesions down to 1 mm in diameter could be detected by the method. In the last 2 studies, focal laser photocoagulation was performed in the rabbit retina. ERG measurements did not indicate a reduction in function, but in the mfERG, the implicit time was slightly delayed implying a local reduction in function. The GFAP labeling was intense in the entire retina in the immediate postoperative phase, and the protein kinase C (PKC) labeling displayed a previously not known pattern with an activation followed by a depletion of the protein expression. The altered PKC expression could be a part of the explanation of the efficiency of laser treatment in diabetic retinopathy. Our findings indicate that focal laser treatment induces a general retinal response evident by alterations in the expression of several important proteins. However, retinal function is not negatively compromised, and we conclude that the treatment at least in the short term is safe. (Less)
Abstract (Swedish)
Popular Abstract in Swedish

Tekniken för vitreoretinal kirurgi har utvecklats betydligt de senaste åren, både vad gäller metodik och instrumentering. Allt fler sjukdomstillstånd i näthinnan kan nu behandlas. För att utveckla dessa metoder vidare, och även öka kunskapen bakom verkningsmekanismen för deras effektivitet, är standardiserade djurmodeller där både funktion och histologi kan utvärderas av mycket stort värde. Full-fälts elektroretinografi (ERG) och multofokal elektroretinografi (mfERG) är metoder där den elektriska aktiviteten i näthinnans neuron kan mätas. ERG mäter totalsvaret från alla tappar och/eller stavar vid ljusstimulering, medan mfERG mäter tappsvaret i ett lokaliserat område på näthinnans centrala del. I... (More)
Popular Abstract in Swedish

Tekniken för vitreoretinal kirurgi har utvecklats betydligt de senaste åren, både vad gäller metodik och instrumentering. Allt fler sjukdomstillstånd i näthinnan kan nu behandlas. För att utveckla dessa metoder vidare, och även öka kunskapen bakom verkningsmekanismen för deras effektivitet, är standardiserade djurmodeller där både funktion och histologi kan utvärderas av mycket stort värde. Full-fälts elektroretinografi (ERG) och multofokal elektroretinografi (mfERG) är metoder där den elektriska aktiviteten i näthinnans neuron kan mätas. ERG mäter totalsvaret från alla tappar och/eller stavar vid ljusstimulering, medan mfERG mäter tappsvaret i ett lokaliserat område på näthinnans centrala del. I denna avhandling utvecklades standardiserade ERG och mfERG protokoll för kanin. Svarsresultaten var reproducerbara, och kombinerat med immunohistokemi kunde effekten av olika kirurgiska ingrepp på näthinnan studeras. Efter vitrektomi noterades reducerade amplituder för ERG i upp till 4 veckor, där stavarna var mer påverkade än tapparna. Efter operationen noterades en generell inmärkning av näthinnan med glial fibrillary acidic protein (GFAP), med kraftigare inmärkning i de ögon som opererats med en låg klipphastighet på vitrektorinstrumentet, indikerande att en högre klipphastighet är skonsammare för näthinnan. Det utvecklades även en experimentell metod för retinektomi, varvid en lokaliserad del av kaninens nähinnan avlägsnades kirurgiskt. Postoperativa mfERG undersökningar visade en generell reduktion av näthinnans centrala funktion upp till en månad. Därefter restaurerades gradvis funktionen, utom i det område där näthinnan var bortopererad. Studien visade att förändringar ner till 1 mm i diameter kunde detekteras med denna metodik. I de 2 avslutande studierna utfördes fokal laserbehandling av kanin näthinna. ERG visade ingen reducerad funktion, men i mfERG noterades en fördröjning av svaret som tecken på en lokaliserad påverkan. Inmärkningen av GFAP var uttalad i hela näthinnan postoperativt, och protein kinase C (PKC) inmärkning uppvisade ett tidigare inte känt aktiveringsförlopp med åtföljande hämning. Det förändrade uttrycket av PKC skulle delvis kunna förklara varför laserbehandling är effektivt vid diabetesretinopati. Resultaten indicerar att laserbehandling inducerar en generell påverkan på uttrycket av ett flertal proteiner, där dock funktionen inte är märkbart påverkad. Fokal laserbehandling bedömes därför, i alla fall på kort sikt, säker för ögat. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • prof Stéfansson, Einar, MD, PhD
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Oftalmologi, Ophtalmology, retinectomy, GFAP, PKC, rabbit, vitrectomy, focal laser photocoagulation, full-field electroretinography, multifocal electroretinography
pages
109 pages
publisher
Department of Ophthalmology, Lund University
defense location
GK salen Biomedicinskt centrum Sölvegatan Universitetssjukhuset i Lund
defense date
2006-04-22 10:00:00
ISBN
91-85481-67-X
language
English
LU publication?
yes
additional info
id
54893a4e-f1ba-4417-9441-1c2dd74f67dc (old id 546488)
date added to LUP
2016-04-01 16:27:41
date last changed
2018-11-21 20:41:34
@phdthesis{54893a4e-f1ba-4417-9441-1c2dd74f67dc,
  abstract     = {The field of vitreoretinal surgery has expanded greatly over the last decades. A continuous refinement of surgical methods and instruments has increased the number of treatable retinal disorders. Vitrectomy, retinectomy and laser treatment are all part of the modern surgical arsenal. In order to further develop and refine these methods, and also to improve the knowledge of the mechanisms behind their efficiency, standardized animal models including functional and histological evaluations are of great value. Full-field electroretinography (ERG) and multifocal electroretinography (mfERG) are methods by which electrical activity from neurons in the retina can be measured. ERG measures the total response of cones and/or rods after light stimulation whereas mfERG measures the focal cone-mediated activity from the central part of the retina. In this thesis the ERG and mfERG protocols were adapted and standardized for the rabbit eye. Reliable and reproducible ERG readings were obtained, and combining the technique with immunohistochemistry, the retinal impact of various surgical procedures in the rabbit eye was studied. After vitrectomy, ERG recordings displayed reduced amplitudes up to 4 weeks postoperatively, with rods more affected than cones. A general glial fibrillary acidic protein (GFAP) labeling throughout the retina was noted postoperatively, with a more intense labeling in eyes where a low cutting rate of the vitrectomy instrument had been used, implying a higher degree of traumatic impact compared with high-speed settings. An experimental method was also developed for performing a retinectomy in the rabbit eye, where a part of the retina was surgically removed. Using the mfERG, it was shown that the procedure induces a general reduction of the central retinal function for 1 month. After this time, retinal function was gradually restored except for in the area of removed retina. The study thus showed that lesions down to 1 mm in diameter could be detected by the method. In the last 2 studies, focal laser photocoagulation was performed in the rabbit retina. ERG measurements did not indicate a reduction in function, but in the mfERG, the implicit time was slightly delayed implying a local reduction in function. The GFAP labeling was intense in the entire retina in the immediate postoperative phase, and the protein kinase C (PKC) labeling displayed a previously not known pattern with an activation followed by a depletion of the protein expression. The altered PKC expression could be a part of the explanation of the efficiency of laser treatment in diabetic retinopathy. Our findings indicate that focal laser treatment induces a general retinal response evident by alterations in the expression of several important proteins. However, retinal function is not negatively compromised, and we conclude that the treatment at least in the short term is safe.},
  author       = {Gjörloff, Karin},
  isbn         = {91-85481-67-X},
  language     = {eng},
  publisher    = {Department of Ophthalmology, Lund University},
  school       = {Lund University},
  title        = {Experimental vitreoretinal surgery in the rabbit eye - electrophysiology and morphology},
  year         = {2006},
}