David J. Apple

Anterior chamber lenses. Part I: Complications and pathology and a review of designs

ABSTRACT Clinicopathologic data to assist ophthalmologists in choosing a safe and efficacious anterior chamber intraocular lens (IOL) are rapidly becoming available. Two important factors that have led to an increased success rate with some anterior chamber IOL styles are (1) attention to lens design and (2) attention to modern manufacturing and lens finishing techniques. We now know much more about how to achieve appropriate lens flexibility, which decreases the need for perfect sizing. Increased attention has been given to the anteriorposterior vaulting characteristics of IOLs. This has reduced the incidence of various complications such as the intermittent touch syndrome and the uveal chafing syndrome. We recognize several design flaws in some lens styles. For example, there is now a considerable decrease in the number of small‐diameter, roundlooped anterior chamber IOLs being implanted, particularly those with a closed‐loop configuration. Several problems have been and continue to be caused by some poorly manufactured anterior chamber lenses with sharp optic and haptic edges. Technology to assure smooth lens finishing and polishing is available and readily accessible to all manufacturers. Defective lenses should soon be a thing of the past.

A comparison of ciliary sulcus and capsular bag fixation of posterior chamber intraocular lenses

We compare indications, advantages, and disadvantages of ciliary sulcus and lens capsular bag (lens capsular sac) fixation of posterior chamber intraocular lenses (IOLs). Our findings suggest that, whenever possible, it is efficacious to implant the loops of posterior chamber IOLs within the capsular bag. This positions the lens optic and the supporting loops in the natural anatomical position, sequestered from highly vascular uveal tissue and the blood aqueous barrier. This should minimize the potential for complications that may be associated with iris-ciliary body contact. Considering the rapid increase in the number of implantations of IOLs now being performed (approximately 700,000 per year in the United States alone), a possible reduction of even 1% in clinically significant complications would make this effort worthwhile. Widespread application of in-the-bag implantation is predicated on the assumption that the surgeon is proficient with this procedure and that careful follow-up of patients does not reveal any significantly increased incidence of lens dislocation due to zonular rupture.

Decentration of Flexible Loop Posterior Chamber Intraocular Lenses in a Series of 222 Postmortem Eyes

Two hundred twenty-two postmortem eyes containing posterior chamber intraocular lenses (IOLs) were analyzed for optic decentration in relationship to lens style, implant duration, and loop fixation site. Decentration values were not affected significantly by either lens style or implant duration. In 33.3% of specimens, both loops were situated within the lens capsular sac, 18.0% had both loops fixated in the ciliary sulcus, and in 48.7% one loop was fixated in the lens capsular sac and the opposite loop in the ciliary sulcus or zonular region. There was a statistically significant difference in the amount of decentration in the three fixation groups studied. Capsular fixation provides the best and most consistent centration compared with fixation of both loops in the ciliary sulcus or asymmetrical fixation with only one loop in the capsular sac.

Posterior capsular opacification and intraocular lens decentration Part I: Comparison of various posterior chamber lens designs implanted in the rabbit model

ABSTRACT Experimental phacoemulsification procedures were performed in 54 Rex rabbits. In 96 eyes, posterior chamber intraocular lenses (IOLs) were implanted in the capsular sac, and 12 eyes served as controls with no lens implantation. The IOLs were divided into eight groups consisting of both one‐piece and three‐piece styles with various optic designs. Each lens was evaluated for the relative effect on posterior capsular opacification (PCO) and optic decentration, two of the most common complications of modern cataract surgery and IOL implantation. Optics with a convex‐anterior, plano‐posterior design (the type of IOL optic most frequently implanted today) had the highest incidence of PCO With capsular fixated IOLs, the features that have a statistically significant impact on reducing PCO include (1) one‐piece, all‐polymethylmethacrylate (PMMA) IOL styles, (2) a biconvex or posterior convex optic design, and (3) angulated loops. Lens decentration was not affected by the optic design, but statistical analysis showed that one‐piece, all‐PMMA IOL construction provided the most consistent centration.

Posterior capsular opacification and intraocular lens decentration Part II: Experimental findings on a prototype circular intraocular lens design

ABSTRACT In a prospective randomized study, 25 New Zealand white rabbit eyes were implanted with four intraocular lens (IOL) designs These included a one‐piece modified J‐loop IOL, a three‐piece modified J‐loop IOL, a rigid disc IOL, and an experimental compressible disc (CD) IOL. The CD IOL revealed the lowest mean posterior capsular opacification (PCO) of all IOLs tested (P <.01). With all lenses tested, a positive correlation between PCO and decentration was found (R = 0.55, P <.05). These results suggest that because of its design features (i.e., one‐piece construction, biconvex optic, posterior angulation of the fixation element), the CD lens produces a mechanical barrier against lens epithelial cell migration and reduces the incidence of PCO.

Biocompatibility of implant materials: A review and scanning electron microscopic study

The evolution of various plastic materials used in the manufacture of intraocular lenses is reviewed, with special reference to the problem of biocompatibility of lens haptic materials. To date, polypropylene has been found and continues to be a highly effective, relatively inert material, providing good surgical results. However, the present study and other morphologic and chemical studies have provided evidence that indicates long-term alteration of polypropylene may occur. For this reason we believe that further studies of this particular polymer are warranted. Also, a continuing search and trial of other plastics to discover an equivalent or even more efficacious haptic material seems desirable. There is a need for careful long-term follow-up of patients after intraocular lens implantation, particularly of young patients.

Posterior chamber intraocular lenses in a series of 75 autopsy eyes Part I: Loop location

ABSTRACT Over a period of 27 months, November 1983 to February 1986, 75 eyes obtained postmortem with posterior chamber intraocular lenses (IOLs) were examined at the Center for Intraocular Lens Research, University of Utah Health Sciences Center. These IOLs were studied by histopatholog cal techniques to determine the location of the loops. The most common combination, found in 47% of the specimens, was one loop in the lens capsular sac (bag) and one loop in the ciliary sulcus. In 32% of the specimens, both loops were in the capsular sac; in 17%, both loops were in the ciliary sulcus: Compared to results observed in other autopsy studies, in which capsular fixation was documented in less than 3% of cases, these findings reflect a trend toward capsular sac (in‐the‐bag) implantation of open‐looped posterior chamber IOLs.

Localized endophthalmitis: A newly described cause of the so-called toxic lens syndrome

ABSTRACT We report five cases of post‐extracapsular cataract extraction infection in which subsequent pathologic analyses identified the organisms and found the infection to be localized or confined to the lens capsular sac. The most common offending organisms were gram‐positive pleomorphic bacilli. In one case, we were able to identify the bacteria as Propionibacterium acnes. We designate this condition a localized endophthalmitis. It should be considered any time a persistent, smoldering, postoperative inflammation occurs, and in the differential diagnosis of phacoanaphylactic endophthalmitis. The condition itself is not new, but undoubtedly many such cases have gone unrecognized or have been misdiagnosed as the so‐called toxic lens syndrome. In localized endophthalmitis, a clinically visible inflammatory process may occur even when multiple diagnostic taps are negative, although when the cases first appeared, the surgeons were not aware of the entity and anaerobic cultures were not always obtained. A negative tap may be explained by the fact that metabolic products from the organisms are released from the bag into the anterior segment and vitreous. A synergistic reaction may occur between these organisms and retained lens cortical remnants that may cause or exacerbate a hypersensitivity reaction. The condition may be worsened by Nd:YAG capsulotomy. The pathogenesis of localized endophthalmitis has nothing to do with the type of intraocular lens fixation (lens capsular sac or ciliary sulcus); rather, the simple presence of a capsular sac after extracapsular cataract extraction is the prerequisite for the clinical condition.

Anterior chamber lenses. Part II: A laboratory study

ABSTRACT An analysis of 606 surgically removed anterior chamber intraocular lens (IOL) specimens revealed that 351 or 58% of these were smalldiameter, round loop, closed‐loop styles. Because of the extremely high percentage of IOLs with this design received in our laboratory and the correlation of clinical histories with our histopathologic findings, we have concluded that such IOLs do not provide the safety and efficacy achieved by other anterior chamber lens designs. The finely polished, one‐piece, all‐PMMA styles fared well in our study. Although these one‐piece styles comprise well over 50% of the American market share of anterior chamber IOLs, they comprise only 14% of all anterior chamber IOLs accessioned in our laboratory, compared to 58% for closed‐loop designs. We believe that implantation of anterior chamber lenses with small‐diameter, round, closed loops is no longer warranted. Patients in whom these IOLs have already been implanted should be carefully followed. It is our opinion that the FDA should recall or closely monitor all IOLs of this design and that implantation of closed‐loop lenses should be discontinued in the United States. Furthermore, we believe that an IOL deemed to be not medically sound or worthy of implantation in the United States should not be marketed or donated outside of this country.

Anterior segment complications and neovascular glaucoma following implantation of a posterior chamber intraocular lens.

Lens implantation is now a highly successful operation. Although follow-up over 5 to 10 years with posterior chamber lenses is incomplete, the complication rate appears to be as low or lower than other lens styles. We present an exception: a clinicopathologic analysis of a globe, enucleated 4 years postoperatively, which in spite of uneventful implantation of a posterior chamber lens, developed neovascular glaucoma. Microscopic studies suggest several mechanisms for this rare complication including deep erosion of a prolene loop into the ciliary body, anterior segment ischemia, and breakdown of the blood-aqueous barrier. Scanning microscopy showed cracking of this deeply embedded loop, a finding we interpret as possible stress cracking and/or oxidation. The more flexible loops now used in modern lenses may decrease the chance of deep erosion. Implantation of a loop in the capsular bag may minimize the danger of both erosion and loop degradation. Patients should be followed long-term in order to recognize and treat these rare, but potentially disastrous complications.