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

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 Because of this development phacoemulsification has recently superseded extracapsular cataract extraction (ECCE) as the preferred method.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

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

The function of the blood-aqueous barrier (BAB) is a sensitive measure of surgical technique. Since BAB disruption is a sign of intraocular inflammation, quantitative and objective measurements of the postoperative inflammatory response in the anterior chamber are good indicators of the quality of surgical methods and the biocompatibility of implanted materials. In the present work the inflammatory response and BAB function was studied on humans with laser flare photometry and anterior chamber fluorophotometry with determination of the diffusion coefficient for fluorescein leakage through the BAB. These methods can detect clinical as well as subclinical inflammatory reactions. In rabbits these techniques may be less reliable. Samples from the rabbit aqueous humour were taken and analysed for prostaglandin E2, white blood cells and proteins. The rabbit iris-ciliary body and after cataract were dissected for wet mass measurements. Corneal thickness was measured by pachymetry.

In humans the clinical outcome was assessed with slit lamp examination, visual acuity and intraocular pressure measurements. Phacoemulsification induced significantly less surgical trauma with less BAB disruption compared to ECCE. The size of the incision was a significant factor for the intraocular inflammatory response. It is important to secure placement of the IOL in the capsular bag since significantly more inflammation and after-cataract was found following ciliary sulcus fixation of the IOL. Eyes with a small CCC showed less inflammation than eyes with a large CCC. The diameter of the CCC did not affect the amount of after-cataract. The postoperative inflammatory response was not correlated to the amount of phacoemulsification energy used during surgery. After phacoemulsification and implantation of a heparin surface modified IOL in eyes with no other known disease the 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.