Management of glaucoma in the implanted patient

The Binkhorst Medal Lecture. Biologic relationship between poly(methyl methacrylate) intraocular lenses and uveal tissue

Implantation of a poly(methyl methacrylate) (PMMA) intraocular lens (IOL) after cataract surgery is associated with breakdown of the blood-ocular barrier and a foreign body inflammatory response. Although the material is biocompatible, it is not inert. The history of PMMA IOL implantation has reflected mechanical, chemical, and immunological interactions between the IOL and ocular tissues. The common link in these events is instability of the blood-ocular barrier. In this lecture, I discuss the nature of these interactions and present evidence that currently investigated methods of surface modification and capsular bag IOL implantation are effective in stabilizing the blood-ocular barrier.

The glaucomas in aphakia and pseudophakia

Intraocular pressure may become temporarily or permanently elevated at various intervals following cataract surgery. There are several mechanisms by which glaucoma develops as a complication of the cataract extraction itself. The presence of a pseudophakos may or may not contribute to the pathogenesis. Important diagnostic clues include the anterior chamber depth, the presence or absence of an iridectomy, gonioscopic findings, and the appearance of the optic nerve head. Life-long medical treatment is frequently justified, as alternative laser or surgical modalities may not be successful. The exact causes for high failure of filtration surgery in aphakic eyes is not clearly understood; scarring of the conjunctiva, the vitreous, and altered characteristics of the aqueous humor have all been incriminated. Current research to improve surgical success includes the development of effective artificial drainage implants or the use of pharmacologic modulators of wound healing, which promote filtration by preventing scar formation.

Preoperative evaluation of the cataractous patient

The author reviews the methods and considerations involved in evaluating the cataractous patient. A well documented work-up is essential both to determine the need for surgery and to be able to inform the patient of possible outcomes. Many subjective factors influencing the decision to operate are also taken into account. The decision must be made on the basis of the work-up, a complete evaluation of the patient's complaints, lifestyle, and needs, and consideration of the risk factors involved. Indications and contraindications for intraocular lens implantation are examined. The subject of calculating lens power is covered in detail. The use of endothelial cell counts is also examined.

Ghost cell glaucoma following lens implantation

When intraocular hemorrhage occurs following cataract surgery and lens implantation, ghost cell glaucoma may develop. An intraocular lens (IOL) may be a factor in recurrent bleeding, particularly in the predisposed patient. Six patients with ghost cell glaucoma following cataract surgery and lens implantation are described. Because intraocular pressure (IOP) was uncontrolled, vitrectomy was performed to remove the reservoir of ghost cells. In each case, postoperative visual acuity improved to 20/40 or better and IOP was controlled with the use of medications.

Surgical management of chronic glaucoma in aphakia

The surgical management of glaucoma in aphakia has been limited by poor success in the control of intraocular pressure and serious postoperative complications that threaten vision. A consecutive series of trabeculectomy filtering procedures in aphakic eyes with a mean preoperative intraocular pressure of 38 mmHg was followed for an average of 26 months and revealed a 62% control of intraocular pressure at 21 mmHg or less. Five additional patients (24%) had pressures lower than 21 mmHg following digital massage. The complication of decreased visual acuity following surgery was significant but not directly related to the surgical procedure. Another patient population with glaucoma and aphakia with a mean preoperative pressure of 25 mmHg was treated with laser trabeculoplasty. In 12 of 15 patients (80%) intraocular pressure was lower than 22 mmHg for an average of eight months and did not require glaucoma surgery. There were no significant complications following this therapy and all patients retained preoperative level of visual acuity. In aphakic patients who have uncontrolled glaucoma on maximal medical therapy, surgery is indicated. We recommend the following approach to surgical management: (1) Laser treatment to the trabecular meshwork if the angle is open; (2) if this fails, or the angle is extensively closed, a trabeculectomy filtering procedure is suggested; (3) cyclocryotherapy has been effective in controlling pressure but the unpredictable loss of vision has prompted caution in seeing eyes; (4) cyclodialysis; and (5) transpupillary or transscleral treatment of the ciliary processes are additional modes of therapy. Improved results of surgical treatment for glaucoma and aphakia have been encouraging and should be used when maximal medical therapy is ineffective.

Pseudophakia and glaucoma

A retrospective study of 40 eyes with pseudophakia and glaucoma is presented. Consideration of pre-existing and secondary types of glaucoma is given. Complications relating to pseudophakia and glaucoma are included as well as a discussion of mechanisms. Visual function results are given and medical and surgical therapies are outlined.