Inflammatory response after cataract surgery : Randomized controlled clinical and laboratory studies of different surgical techniques

Abstract

During the last few years the phacoemulsification technique for cataract extractionhas improved considerably. Because of this development phacoemulsification has recentlysuperseded extracapsular cataract extraction (ECCE) as the preferred method. Theaim of the present thesis was to evaluate the new method for cataract surgery andto compare it with ECCE in randomized controlled trials. Studies of details in thesurgical technique were performed on rabbits.

The alleged advantages of phacoemulsification include the small incision and theuse of a more durable anterior capsulotomy - the continuous curvilinear capsulorhexis(CCC), which promotes fixation of the intraocular lens (IOL) in the capsular bag.However, phacoemulsification also involves more sophisticated technique and potentialhazards due to the development of high energies and temperatures in the anteriorchamber as well as the creation of air bubbles and free radicals.

The function of the blood-aqueous barrier (BAB) is a sensitive measure of surgicaltechnique. Since BAB disruption is a sign of intraocular inflammation, quantitativeand objective measurements of the postoperative inflammatory response in the anteriorchamber are good indicators of the quality of surgical methods and the biocompatibilityof implanted materials.

In the present work the inflammatory response and BAB function was studied onhumans with laser flare photometry and anterior chamber fluorophotometry with determinationof the diffusion coefficient for fluorescein leakage through the BAB. These methodscan detect clinical as well as subclinical inflammatory reactions. In rabbits thesetechniques may be less reliable. Samples from the rabbit aqueous humour were takenand analysed for prostaglandin E2, white blood cells and proteins. The rabbit iris-ciliarybody and after cataract were dissected for wet mass measurements. Corneal thicknesswas measured by pachymetry.

In humans the clinical outcome was assessed with slit lamp examination, visualacuity and intraocular pressure measurements.

Phacoemulsification induced significantly less surgical trauma with less BAB disruptioncompared to ECCE. The size of the incision was a significant factor for the intraocularinflammatory response. It is important to secure placement of the IOL in the capsularbag since significantly more inflammation and after-cataract was found followingciliary sulcus fixation of the IOL. Eyes with a small CCC showed less inflammationthan eyes with a large CCC. The diameter of the CCC did not affect the amount ofafter-cataract. The postoperative inflammatory response was not correlated to theamount of phacoemulsification energy used during surgery. After phacoemulsificationand implantation of a heparin surface modified IOL in eyes with no other known diseasethe great majority of eyes healed satisfactorily without anti-inflammatory treatment.These results indicate that phacoemulsification with IOL implantation is a safe procedure,although repeated BAB reactions may occur.

Key words: Cataract extraction, phacoemulsification, inflammation, blood-aqueousbarrier, anti-inflammatory agents, heparin surface modified intraocular lens, fluorophotometry,prostaglandins, after-cataract, corneal oedema, lasers, comparative study, randomizedcontrolled trial, double-blind method. ISBN 91-628-2762-6