Anterior chamber lenses. Part II: A laboratory study

Anterior chamber lenses. Part II: A laboratory study David J. Apple, M.D. Manfred R. Tetz, M .D. Steven O. Hansen, M.D. Beth R. Pfeffer, M.D. Scott C. Richards, M.D. Richard B. Park, B.S. Gregory W. Ellis, M.D. Alan S. Crandall , M.D. Dolores Kavka-Van Norman, M.S. Randall J. Olson, M.D .. Salt Lake City, Utah

AB TRA T An anal i of606 urgicall remo ed anterior chamb r intra cular len (IOL) 'pecimen re ealed that 351 or 5 % of the wer malldiameter round loop clo ed-loop tyle. Becau e of the extremel high percentage of IOL ,ith thi de ign recei ed in our laborator and the correlation of clinical hi tori with our hi topathologic findin ,we ha e concluded that uch IOL do not provide the afety and efficac achieved by other ant rior chamber len de igns. The finel poli hed one-piece all-PMMA tyle fared well in our tud . Although the e one-piece tyle compri ewell 0 er 50~ of the merican market hare of anterior chamber IOL the compri e only 14~ of all anterior chamber IOL acce ioned in our laborator , compared to 5 % for clo ed-loop de ign . We b lie e that implantation of anterior chamber len e with small-diameter round clo ed loops i no longer warranted. Patient in whom the IOL have alread been implanted hould b carefull followed. It i our opinion that the FDA hould recall or clo el monitor all IOL of thi de ign and that implantation of clo ed-loop len e hould b di continued in the United tate. Furthermore we belie e that an IOL deemed to be not medicall ound or worth of implantation in the United tate hould not b marketed or donated out id of thi countr. Key Word: ant rio1' chamb l' I ns, A xibl In , intra ular I n manufa turing d ~ t , pol m th 1m tha I' lat ri id I n

The large number of anterior chamber lens designs available todayl makes it clear that the ideal lens design has not yet been agreed upon. It is difficult for many implant surgeons, particularly those who perform relatively few anterior chamber implantations, to decide on the safest and most optimal design. Many times intraocular lenses (IOLs) are chosen because of sales

pressure from company representatives, some of whom frankly know very little about their product. Lenses are sometimes even purchased (or forced upon the physician) without regard to quality by nonmedical personnel such as purchasing agents, business managers, or administrators. Too often the individual responsible for the acquisition of IOLs is not informed

From the Departments of Ophthalmology and Pathology, University of Utah Health Sciences Center, Salt Lake City. Supported in part by grants or awards from the American Society of Cataract and Refractive Surgery, Fairfax, Virginia , and the Marriner S. Eccles Foundation , Salt Lake City, Utah. Presented in part at the Annual Meeting of the Canadian Implant Association, Montreal, June 1986; the Welsh Cataract Congress, Houston , September 1986; a hearing of the FDA Ophthalmic Devices Panel , Washington, D.C., October 1986. Reprint requests to David J Apple, M.D., Ophthalmology, AB420, University of Utah HSC, 50 North Medical Drive, Salt Lake City, Utah 84132.

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or is misinformed. More attention is sometimes paid to IOL price, bulk sales, and "package deals" than to lens quality. The FDA has long sought an accurate means of comparing the number of anterior chamber IOLrelated complications associated with each lens design with the total number of implantations of each respective style. The goal of obtaining both a necessary "numerator" (number of complications nationwide with each lens design) and a usable "denominator" (total number of implantations of each lens design) has been an elusive one. The FDA has had difficulties because many adverse reactions are not reported by physicians to the responsible IOL manufacturer. This fact applies whether the offending IOL has actually been removed or is left within the diseased eye. We can confirm this lack of reporting by comparing the number of specimens in our laboratory series with adverse reaction data reported by some IOL companies. A cross-check shows that clinical data from the majority of cases in which explanted IOLs were sent to our Center for analysis have not been reported to the various official channels as requested by the FDA. This frankly suggests that many physicians are skeptical about the sincerity of the response they receive from some of the IOL companies. In addition, we are aware that all IOL companies have simply not been frank with the FDA regarding some of the adverse reaction information given to them by physicians. Policies vary from company to company; most respond rapidly and with integrity, but some companies, if they are not pressured, are not prone to do so. In the study summarized in this section, we have attempted to gain some insight into the complication rates of each anterior chamber lens design submitted to our Center for analysis. We have compared the number of explanted lenses (the numerator) with the best available estimates of the market share percentage for each lens (the denominator). We do not claim absolute statistical significance for this study. Compared to the several hundred thousand anterior chamber IOLs implanted over the past 3.5 years, the 606 lenses we have collected over four years are a relatively small number. However, our series has provided the largest available data base for clinic'opathological analysis of anterior chamber IOLs. The total number of specimens in our series is now large enough to enable us to make some meaningful comparisons. Several obvious trends are indicated by our findings. In November 1986, we completed an analysis of the IOL specimens sent to our laboratory. We compared the number of accessioned anterior chamber IOLs in our series, all from cases with clinically documented IOL-related problems, to the percentage of market share for each lens at the time of the study. The spe176

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cimens included in the study were received from late 1982 to 1986. The goal of this study was to obtain information about which anterior chamber lens designs appear to cause the lowest incidence of complications and which appear to cause the highest complication rate and require explantation most frequently. ANALYSIS OF 606 REMOVED ANTERIOR CHAMBER LENSES As of October 1986, we had analyzed 1,122 surgically removed IOLs and enucleated globes containing IOLs (Figure 1). All 1,122 specimens were from patients with documented clinical complications that required surgical intervention. The lens types were received in the following ratio: Explanted IOLs Anterior chamber

Number Received 606

Percentage 54.0

Posterior chamber

228

20.3

Iris fixation

288

25.7

1,122

100

Total

These specimens were obtained from ophthalmologists nationwide and were sent to us without solicitation. Therefore, the series did not have any known geographical bias that might skew the random nature of the study. Only 8% of the lenses were submitted by the implant surgeon; 92% were removed by a consulting physician. Most were sent directly to us and some specimens were forwarded to us by the American Society of Cataract and Refractive Surgery, Fairfax, Virginia. Most of the IOLs were removed because of such ocular complications as uveitis, pseudophakic bullous keratopathy, cystoid macular edema, secondary glaucoma, hemorrhage, uveal chafing syndromes (e.g., UGH syndrome), opacification of the media, and lens malposition. Thirty-two cases were globes with IOLs in which the postimplantation complications were severe 1122 EXPLANTEO INTRAOCULAR LENSES IFL (288)

o CHAMBER POSTERIOR •

ACL(606)

Fig. 1.

IRIS FIXATION

[] ANTERIOR CHAMBER

(Apple) Graph showing the types of removed IOLs accessioned at the Center for Intraocular Lens Research. University of Utah Health Sciences Center, from late 1982 through October 1986.

REFRACT SURG-VOL 13. MARCH 1987

enough to require enucleation. Examples of two especially severe cases are illustrated in Figures 2 and 3. This series does not include 296 globes with IOLs that were obtained at autopsy and sent to our laboratory during this period. We emphasize that all specimens in this study were from complicated clinical cases. The percentage of each IOL design of the total anterior chamber IOLs is shown in Table 1. The number of accessioned specimens of each lens design is

Table 1. Number and percentage of each IOL style accessioned of 606 total anterior chamber lenses submitted to the Center for Intraocular Lens Research through October 1986. Style Leiske

16.5

27.2

98

16.2

Stahleflex

58

9.6

Choyce (unlicensed)

,54

8.9

Kelman Omnifit and AC-21

40

6.6

Hessburg

30

.5.0

Kelman II

29

4.8

Choyce (licensed)

26

4.3

Multiflex and Feaster

23

3.8

Tennant Anchor

15

2.5

Dubroff (licensed)

14

2.3

Pannu

10

1.7

Miscellaneous AC styles

(Apple) Gross photograph of the external aspect of the anterior segment of a globe that was enucleated because of IOL-related complications. The Optical Radiation Corporation Stableflex model 11 lens that was implanted caused corneal decompensation and melting. As seen in this photograph, the cornea perforated and the IOL extruded from the eye.

z .... ...J

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(Apple) Gross photograph ofthe eviscerated globe of a 16year-old boy. The patient received an Optical Radiation Corporation Stableflex model 11 lens after removal of congenital cataracts at the age of 14. Multiple complications ensued, including incarceration ofloops into iris and ciliary body tissues, inflammation, and retinal detachment. An evisceration procedure was performed on the phthisical eye two years postimplantation.

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9

1.5

35

5.8

shown in Figure 4. There is a significant trend evident in this graph that warrants special mention. Although strict statistical significance is not intended, 351 (black bars in graph) of the 606 anterior chamber IOLs had closed, small-diameter, round loops. These lenses represented 31.3% of all IOL types received and 58.0% of all anterior chamber lenses accessioned in our laboratory. The most commonly received lenses of this

....enen

Fig. 3.

Percentage

Azar 91Z

Simcoe

Fig. 2.

Number Received

165 150 135 120 105 90 75 60 45 30 15 0

Fig. 4.

606 EXPlANTED ANTER lOR CHAMBER IOl's

165

o NUMBER OF LENSES 98

58

54

40

(Apple) Graph showing the number of explanted anterior chamber lenses of each design received at the Center for Intraocular Lens Research from late 1982 through October 1986. Note that small-diameter, round loop, closedloop IOLs of each design are represented by darkened bars on the graph. These lens designs comprise 58% of the 606 explanted anterior chamber lenses received in our series.

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design were the Surgidev model 10 Leiske lens (Figure 5A) and lenses of similar design (Figures 5B and 5C), the IOLAB Azar 91Z lens, the Optical Radiation Corporation model 11 Stableflex lens (Figures 2, 3, and 6), and the Pharmacia-Intermedics model 24 Hessburg lens (Figure 7). After we documented the raw number of each accessioned IOL design (Figure 4), we compared the rate of IOL removal with the average market share of each lens design (Figure 8) according to the following equation: Ratio = Number of explanted ante rior chamber IOLs received Percentage of market share

The market share percentages were obtained from surveys available to the entire IOL industry. We cannot

Fig. 5A.

Fig . 5B.

178

Fig ..5C.

(Apple) Scanning electron micrograph of another c1osedloop anterior chamber l ens (3 M Corporation mode l 70), with curved polypropylene closed-loop fixation elements. This le ns demonstrates many of th e design deficiencies seen in other dosed-loop IOLs. One loop (arrow) required severance from the optic during explantation (original magnification X 10).

Fig. 6.

(Apple) Fifty-eight (58) Optical Radiation Corporation model 11 Stable fl ex IOLs were accessioned in ou r laboratory through October 1986. The Stableflex lens is composed of an optic with four pairs of extruded PM MA loops. When inserted into the eye, the loop pairs often adhere to make contact with the opposite pair (as see n in this photograph) or sometimes overlap. This adh erence in effect changes the mechanical properties of the lens , essentially creating an IOL with two large dosed loops. This can modify th e lens's vaulting characteristics within the eye and may a lso occasionally lead to lens instability. In our opinion and in th e opinion of many surgeons , this is the most difficult lens to remove without causing excessive tissue damage (original magnification X 20).

(Apple) One hundred sixty five (16.5) Leiske lenses and variations of this design were accessioned in our laboratory. As shown in lhble 1,27.2% of the anterior chamber le nses in our study we re Le iske le nses or variations of this style.

(Apple) Scanning electron micrograph of a CooperVision-Cilco Optiflex IOL. This is a one-piece, dosed-loop anterior chamber lens that, although similar in general configuration to th e Leiske lens, is much more rigid (original magnification X 15).

J CATARACT REFRACT

SURG-VOL 13, MARCH 1987

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0 .4

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NOTE: The calculations .,er~ bQ~d on surgically (fmov«l antlrior cllomb" tOLs accessioned in our laboratory from 1983 to actour 1986. This grOllP jncludu onl, top B AC IOLs still sold todoy (all above 4% mark.,t shorr J.

,It,

Fig. 8. Fig. 7.

(Apple) Thirty (30) Intermedics style 24 Hessburg anterior chamber lenses were accessioned in our lahoratorv through October 1986. This SEM shows that the lens i~ adequate in manufacturing quality. However, the same design problems that plagued other closed-loop anterior chamber lenses caused occasional complications. Note the inflammatory debris localized at the loop-optic junction. The loop seen in the upper left is intact but the opposite loop had to be severed during removal ofthe lens (original magnification x 15).

personally confirm the accuracy of the market share data, but we do know that it is purchased from a firm that sells this information to most lens manufacturers for significant sums. We can only assume that since the IOL companies rely on this information, it must be reasonably accurate. The dates on the market share data correlate well with the time of implantation and with removal of most of the lenses in our series. Over 50% of all explanted IOLs are removed by 18 months following implantation, and 80% or more within three years. Many well~known anterior chamber lens styles are not mentioned in the graphs shown in Figures 8 and 9. Instead, they fall into the miscellaneous category of Figure 4 because the number ofaccessioned specimens and the market share were too small to provide meaningful data. Figure 8 provides additional information that we believe makes the raw numbers listed in Figure 4 and in Table 1 more meaningful. This graph shows a ratio based on the number of most commonly accessioned anterior chamber lenses received in our laboratory divided by the percentage of market share for each lens. This ratio, termed ratio 1 , e.g., 12:1 for the Leiske style IOL, is an abstract number. The numerator plotted on the ordinate or Y-axis is based on the number of each lens design catalogued in our series. J CATARACT

(Apple) Bar graph showing ratios based on the number of anterior chamber lenses accessioned in our laboratory compared to the percentage of market share for these lenses during the past three years. Details of this graph and an explanation of ratio l and ratio 2 are explained in the text (pages 178 to 180).

The denominator is the average market share percentage for each model. The higher the ratio on the graph, the more lenses from complicated cases were received in the laboratory as compared to the percentage of market share. Figure 8 shows that the lenses with the highest ratio are the Surgidev style 10 Leiske lens and closely related designs (Figures 5A and 5B). The Choyce-style lenses rank second, but we wish to emphasize that only one third of these are well polished, licensed Choyce lenses. As Figure 4 and Table 1 show, two thirds (54 of the total of 80) are actually the poorly manufactured copies made by several American companies, primarily in the mid-1970s. Third on the list is the Optical Radiation Corporation Stableflex model 11 lens. One can carry the calculations further by observing how each IOL fared with respect to the theoretical expected number of complications based on the percentage of market share. Ratio 2 on the abscissa or X-axis of the curve is based on a numerator that itself is a fraction, i.e., the number of each style of anterior chamber lens received in our laboratory divided by the total number (606) of anterior chamber lenses received in our laboratory. This is the same fraction used to compute the percentages listed in Table 1. This numerator is then divided by the total percentage of market share of each lens, and this calculation indicates the expected incidence of complication rate of each IOL design. A ratio of 1:1 would indicate the expected number of complications if all lenses were of equal

REFRACT SURG-VOL 13, MARCH 1987

179

I

12

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LEISKE STYLE

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0 .6

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0.8

1 .0

1.2

1.4

1.6

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RATIOZ ('/,AC 10L', / '10 MARKET SHARE) NOTE' Th, calculotions .er, based on surgically retnO¥.d anterior chamber IOLs occ,ssionN

4-"

in our loborotory from 1983 to October 1986. This Group includes 01111 the top B AC IOLs sri" sold todoy (all above morlf,t shor' J.

Fig. 9.

(Apple) This bar graph is similar to that seen in Figure 8, but the list is confined to the eight most commonly implanted anterior chamber lenses in use as oflate 1986. We have arbitrarily chosen those IOLs with a mid-1986 market share above 4%. These IOLs fall into three distinct groups: (1) lenses with the highest incidence of complications compared to percentage of market share at the top and upper right end of the scale; (2) a lens in the middle ()f the graph; (3) lenses with the lowest incidence of complications compared to percentage of market share at the lower left of the scale. We wish to emphasize that two thirds of the Choyce-style lenses are the unlicensed, poorly manufactured copies of Choyce's design. The Pharmacia-Intermedics model 44B Dubroff lens is situated in an intermediate position on the scale. All the IOLs shown in the box at the lower left are flexible, one-piece, all-PMMA designs. The term "Omnifit" connotes the trade name of the IOLAB-Precision Cos met version of the Kelman modern tripod lens. The Allergan Medical Optics AC-21 lens has a similar configuration and should be included here.

quality. A hypothetical example: If we had received 61 of a given lens in our laboratory, which is approximately 10% of the total number of 606 anterior chamber lenses, this would give a numerator of 10%. If this particular lens had 10% of the market share, the rati0 2 would be 10% divided by 10%, or 1:1, thus connoting an expected number of complications for that particular lens. A lens that shows a ratio greater than 1: 1 would be predicted to have a higher than expected incidence of complications. For example, the Leiske-style lenses, for which the value of rati0 2 on the abscissa approaches 2:1, would be expected to have a much higher complication rate than the group oflenses on the lower left of the graph. Any ratio less than one on the abscissa would connote a lower than expected incidence of complications. For example, if a hypothetical lens had 5% of complications but 20% of market share, the ratio would 180

J CATARACT

be only 1:4 or 0.25 and the bar would terminate far to the left of 1:0 on the graph. Figure 9 is a similar graph. To focus on what is of most practical importance for contemporary surgeons, we have considered only lenses that are most commonly implanted today-lenses that as of mid to late 1986 had more than 4% of the market share in the American market. Note that the lenses are grouped into three basic categories: 1. The lenses with a high relative ratio of complicated cases (number of accessioned IOLs divided by market share) are in the box at the top of the graph. The three IOLs in this group are the Leiske lens and its variations, several Choyce-like lenses (one-third licensed, two-thirds unlicensed), and the Stableflex lens. 2. The Pharmacia-Intermedics Dubroff lens is situated in an intermediate position. 3. The four lenses situated on the lower left of the graph enjoy a position connoting both a low ratio l on the ordinate and a low ratio" on the abscissa. Viewed from any perspective, thes~ latter IOLs represent a group in which a lower number and incidence of complications appears evident. The Azar 91Z and the Surgidev style 63 lens (see asterisks in Figures 8 and 9) cannot be included in the bar graphs since they have been removed from the market and therefore no market-share information is available. However, the problems encountered with these lenses are relevant to this discussion because many of these lenses remain in patients' eyes and these cases require intensive follow-up. These IOLs must therefore be considered in this report and in our schema. Much of the information in our study had been made known to the involved IOL companies many months prior to this study, indeed long before the major FDA Ophthalmic Devices Panel meeting on anterior chamber IOLs on October 20, 1986, and our letter to the editor on this topic that appeared in the Archives of Ophthalmology in January 1987. 2 For example, our initial report on 44 explanted Surgidev style 10 Leiske IOLs and similar lens designs produced by other manufacturers was published in July 1985. 3 No action was taken at that time; as of October 1986, we had accessioned 165 lenses of this design. We received no indication that the manufacturer planned any corrective action with this IOL during this period. The Surgidev style 10 Leiske lens was finally placed on core status by the FDA soon after the October 20th hearing (FDA letter, December 18, 1986). At the time of this writing (early 1987), we have no indication that sales of this IOL have been terminated. In a 1984 publication ,4 the histopathologic and SEM findings of 18 Azar 91Z lenses (accessioned in our laboratory beginning in early 1983) were reported. IOLAB Corporation acted in a responsible manner to

REFRACT SURG-VOL 13, MARCH 1987

the rapidly accumulating clinical and pathological data concerning this lens and withdrew it from the market in August 1983. As of October 1986, we had received 98 of these IOLs, indicating that complications from these lenses, most of which were implanted in 1982 and 1983, still occasionally surface. We first communicated our deep concern about the Optical Radiation Corporation model 11 Stableflex lens to executives and other representatives of the company in April 1985, almost two years ago. Our report discussing 28 removed model 11 Stableflex lenses was published in May 1986. 5 As of October 1986, we had accessioned 58 of these IOLs. The most common problems caused by this IOL are uveitis and corneal decompensation (Figure 2). This lens has had the greatest percentage increase in our accession rate during the last year of our study. Despite multiple discussions and correspondence with the company representatives to express our concern about this lel1s, the company did nothing to correct this problem. Only after the FDA placed this lens on core status following the October 20, 1986, hearing (FDA letter, December 18, 1986) was any remedial action taken. At the time of this writing (early 1987), we have been informed that company representatives are removing this lens from office and hospital inventories. We have received 30 removed model 24 Hessburg IOLs, which is also a closed-loop design. The market share of this IOL is now below 4% and it is therefore not considered in the graph shown in Figure 9. One of the most serious problems with all smalldiameter, round loop, anterior chamber IOLs is the difficulty in removal. Evidence of this clinical problem was verified in our histopathologic and scanning electron microscopic analyses. This difficulty was caused in most cases by incarceration of the small-diameter round loops within synechias in the anterior chamber angle and on the iris root. When removal is necessary, this encapsulation often requires excessive cutting of the loops and/or surrounding tissues. Based on our clinicopathological analyses, the Optical Radiation Corporation's model 11 Stableflex lens is undoubtedly the most difficult anterior chamber lens to remove surgically. The fact that this lens has four loop pairs means that eight loops may become incarcerated in angle recess tissue. In many instances, IOL removal is required for reasons other than problems with the implant itself, such as ocular trauma. However, in our opinion, even in these cases the excessive difficulties often encountered during removal, documented by the explanting surgeons' clinical records and our SEM analyses, represent inherent design defects. As a basic prerequisite for IOL manufacture, the designer should anticipate that removal may be necessary. Any lens should be designed to permit the J CATARACT

surgical removal procedure to be performed with the least possible damage to the delicate tissues of the eye.

WHAT ARE THE "BEST" ANTERIOR CHAMBER LENSES?

Individual surgeons often understandably develop a "rapport" with a given surgical technique and particular lens design. One develops experience and expertise in inserting that lens. The conscientious surgeon follows his or her patients carefully over the long term to evaluate the results of the surgical procedure. Assuming that financial considerations about which lens to implant do not cloud one's judgment and that such a choice is not dictated by policies not directly concerned with the patients' welfare (e.g., pressure from buying groups and governmental or hospital bureaucracies), we feel that it is certainly appropriate for a surgeon to stand by what is best for him or her. In the case of anterior chamber lenses, which are now implanted rather infrequently, it is often more difficult for a surgeon to evaluate the long-term results. Follow-up of patients can be difficult for many reasons, including the increased mobility of our population. Two articles by Beehler6 ,7 emphasize the need for long-term follow-up. Almost any well-implanted IOL will show good initial results. In early 1984, Beehler6 reported favorably on the use of the Stableflex lens after a short-term follow-up. Subsequently, he implanted 500 more of these lenses. He has recently reported that over the past two years an unusually large number of these patients have developed corneal decompensation. 7 It is therefore clear that with passage of time, as the complications slowly emerged, his opinion of this lens changed. He stated that "in view of the high incidence of corneal decompensation with this lens, I now recommend one of the other flexible anterior chamber lenses when AC lenses are indicated."7 This contribution by Dr. Beehler demonstrates that the true safety and efficacy of a lens can only be determined after careful and thorough, long-term follow-up. In addition to good clinical follow-up, it is also useful to obtain ancillary information, such as we provide from our clinicopathologic studies, to build a more informed base from which to make correct decisions. This is one of the purposes of this paper: not to dictate to physicians what to do, not to provide a Mondaymorning postmortem on the success or failure of implantations, but to disseminate the data we acquire through our research to assist the surgeon in making well-informed decisions. The conclusions presented in this section are based on what we believe are objective, scientific studies. We have remained independent in order to avoid bias toward or against any particular surgeon or lens manufacturer. Our Center has no proprietary interest

REFRACT SURG-VOL 13, MARCH 1987

181

in any of the IOLs discussed in this report. The comments to follow represent the opinions of the director of the Center for Intraocular Lens Research and are based on the best information available to us as of January 1987. The definition of what might be termed the "best" anterior chamber lens has changed through several generations of IOLs. For each individual surgeon , the best lens is probably the one that has continued to serve him or her well, based on patient follow-up and evaluation over the long term. As noted in the introduction, the term "best" is relative. The history of IOLs has shown that what is considered best today may be obsolete tomorrow. It is reasonable for a surgeon to continue using an IOL if complications are minimal, but at the same time one should continuously stay informed about new research findings that may alert one to possible defects in any given lens-defects that may cause late-onset complications even years after implantation-as has often been the case. Unfortunately, there has been a time lag in the dissemination of such vital information. However, as the recent volatile changes in the anterior chamber IOL marke t indicate , such delays can be shortened. The recent FDA actions changing the status of several anterior chamber IOLs has been extremely helpful in this respect. Surgeons and patients now expect high quality results from implantation surgery. A "good" success rate for the 1950s was perhaps around 50%, for the 1970s approximately 70% to 90%, but in the mid-1980s we expect to have a success rate of at least 90% or more, particularly in uncomplicated cases . We are aware of the limitations of our studv and acknowledge that we do not have all the an;wers. However, during the past two years, the number of specimens received in our laboratory has increased exponentially and much information has been gained through our analyses. We feel confident that our data can be used to identify definite trends in the complication rate for each lens design, and in many instances, to pinpoint the pathogenesis of specific complications. We assume that each anterior chamber lens style is implanted in both complicated and uncomplicated cases in approximately equal proportions. This assumption becomes more valid as the number of specimens in our series increases. We are therefore able to factor out these variables in reaching our conclusions. Our comparison of anterior chamber lenses is intended as exactly that-a direct comparison of one lens design to other designs. For this discussion, we have divided anterior chamber lenses into five groups. Group 1: Small-Diameter, Round Loop, Closed-Loop Anterior Chamber Lens Designs Although we do not claim statistical significance for 182

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our series, there is enough evidence to lead us to predict (1) a higher than acceptable rate of complications and (2) inordinate difficulties with lens removal in many cases with the small-diameter, round loop, closed-loop IOL designs. The main reasons for these conclusions have been discussed and illustrated in Part 1 of this studyl and are summarized in Table 2. Table 2. A pathologist's view of inherent design and manufacturing Raws in small-diameter, round-loop, closed-loop anterior chamber lenses. 1. May be difficult to size.

2. May have inappropriate vault and compression ratios. If a lens is compressed, it may vault anteriorly or posteriorly; either type of response can cause deleterious effects. There is no "give" to the IOL as is the case with the more flexible styles. 3. May cause "cheese-cutter" effect, particularly if the lens is too large. Subsequent e rosion and chafing may cause uveitis and subsequent CME and PBK. 4.. S6me lenses may have large contact zone over broad areas of the

angle with the potential for secondary glaucoma. .5. The poorly finish ed, sharp edges in some, but certainly not all, models can cause chafing, leading to various sequelae such as uveitis or the UG H syndrome. 6. Synechial formation around the small-diameter loops may make the lens difficult to remove when necessary. Tearing of ocular tissues and hemorrhage are common results of removal surgery if great care is not taken during the surgery.

Our clinicopathologic studies lead us to believe that implantation of anterior chamber lenses with closed, small-diameter, round 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 all IOLs of this design and that implantation of closed-loop lenses should be discontinued in the United States. As pre viously stated, as of December 1986 the FDA has placed some IOLs of this design back on core investigational status. We also feel strongly that distribution of closed-loop design IOLs in other countries is not justified. Indeed, should any lens deemed not medically sound or worthy of implantation in the United States be used in IOL surgery elsewhere?

Group 2: Flexible, Open-Loop, One-Piece, All-PMMA Anterior Chamber Lenses With Haptic or Footplate Design The graphs in Figures 8 and 9 show that lenses of this basic design are in a favorable location on our schema. No matter how we analyze the data, the lenses in this group have been shown to have the lowest complication rate per percentage of market share. Figures 10 to 13 illustrate lenses in this group and Table 3 summarizes many of the features that form the basis of our conclusions about this lens design.

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Fig. 10.

(Apple) Scanning e el ctron micrograph of a Kelman flexible, three-point fixation anterior chamber lens , the IOLAB-Precision Cosmet design . Compare this lens with the Allergan Medical Optics model AC-21 illllstl'ated in Figure 18B, Part I (original magnification X 10).

We have compared the findings from our series of 606 anterior chamber IOLs from known complicated cases with our separate study of296 autopsy eyes, 82 of which contained anterior chamber IOLs from autopsy eyes accessioned as of October 1986. Many of the postmorte m eyes had pathological lesions that were often not clinically documented. This comparison also provides significant evidence that one-piece, allPMMA anterior chamber lens designs with fully integrated haptic or footplate fixation elements are better suited for anterior chamber angle implantation. For example, an analysis of the postmortem eyes that were implanted with such lenses showed a generally lower incidence of tissue erosion , iris tuck, uveal chafing, smoldering inflammatory reactions, lens malposition, and disturbance of adjacent tissue. In other words , most of these IOL designs, when examined by both gross and microscopic techniques, typically show a more "physiological" fit within the eye. One fact that will withstand form al statistical scrutiny: Although the flexible , one-piece, all-PMMA anterior chamber lenses now possess well over 50% of the anterior chamber lens market share, only 14% (85 IOLs) of the 606 anterior chamber specimens received in our laboratory from complicated cases were this design. In striking contrast, 58% of the 606 anterior chamber specimens were closed-loop IOLs of the typ e listed in Group l. J CATARACT

Fig. 11.

(Apple) Scanning electron micrograph of a flexible, onepiece , all-PMMA CooperVision-Cilco Kelman Multiflex lens. Note that the sites of four-point haptic fixation are separated b y aconcave shaft (arrows) in relation to th e angle recess contact. The high quality of surface and edge finish attainable with tumble polishing is evident (original magnification x 10).

Fig . 12 .

(A pple) Scanning electron micrograph of a Feaster lens, manufactured by Coburn , shows another excellent example of a well-manufactured flexible, one-piece, allPMMA anterior chamber IOL. The fixation elements of this lens are convex (arrows) so a relatively broad arc of contact with the angle recess occurs. Thus far this lens has provided excellent results (original magnification x 15).

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Fig. 13.

(Apple) Scanning electron micrograph ofa one-piece. allPMMA Allergan Medical Optics Simcoe C-loop ante rim chamber lens. Like the Feaster lens (Figure 12). this C-loop design is convex in the angle recess (arrO\\'s) and provides a broad arc of contact . in contrast to point fixation IOLs. To date there have been fe\'" complicatiolls reported with this de sign. The high finish quality of this lens and other similar all-PMMA IOLs is produced hy tumble-polishing techniques (o riginal magnification X 10).

Since one-piece, flexible, open-loop anterior chamber lenses have the largest anterior chamber IOL market share, not only in the United States but also in Europe, the relatively small number received to date for analysis in our laboratory speaks very well for this general design. Our results in this study permit us to be optimistic about the success rate with these IOLs. The modern one-piece all-PMMA anterior chamber IOLs combine in many ways the proven advantages of the Choyce-style footplate or haptic with enhanced flexibility (Figures 14, 15A, and 15B). A one-piece lens can be manufactured so that it is suffiCiently sturdy to maintain its orginal design and vault. However, two-piece or multiple-piece IOLs, with separate extruded polymer loops staked into holes at the optic edge , may be subject to pressures that may change the loop angulation at the loop-optic junction. Any change in the vault of the IOL loop makes it probable that contact by IOL components will occur either anteriorly on the cornea or posteriorly on the iris. Perhaps more importantly, most one-piece IOLs are beau tifully finished by modern tumbling techniques , thereby providing a smooth, rounded surface at points of contact with delicate uveal tissues. Although PMMA is classified as a glass-like polymer, the danger ofin vivo PMMA fracture , a rare problem in earlier years,S has bee n largely solved by improved lens design and manufacturing. These one-piece IOLs, particularly those with a footplate design, are usually much easier

Table 3. A pathologist's view of open-loop, one-piece, Hexible anterior chambel' lenses of the mid-1980s. 1. Most present-day lenses now have an excellent finish with highly polished smooth surfaces and rounded edges (easily accomplished with tumble-polishing techniques) . Tissue contact lw any component of th e IOL (optic. haptic , or loop) is much gentler with less possibility of chafing damage . 2. Sizing is less critical with flexible open-loop designs. 3. In contrast to a closed-loop anterior chamber IOL . th e vault engineered into a well-designed open-loop le ns is maintained even under high compression . This minimizes IOL touch against the cornea or posterior touch against the iris.

4. Point-fixation is possible since haptics may only subtend small areas of the angle outflow structures. The C-Ioop or convex broad arc configuration has not yet been shown to cause serious problems. However, furth er follow-up studies are warranted.

5. Most of these open-loop IOL designs are much easier to re move.

if necessary, especially those with Choyce-like haptic or footplate designs. The well-polished surfaces are usually not completely surrounded by goniosynechias or "cocoon" membranes and will usually slide out without undue difficulty or excessive tissue damage.

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Fig. 14.

(Apple) Scanning electron micrograph of a C hoyce Mark IX rigid anterior chamber IOL. This lens is mainly distinguishable from the Mark VIII by two holes drilled in the optic. This one-piece , all-PMMA lens is finely finished because of tumble polishing. Notice the four characteristic broad haptics (o riginal magnification X 10).

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Fig. 15B.

Fig. 15A.

(Apple) Scanning electron micrograph of th e recently introduced IOLAB Surefit 85J lens . This design graphically represents a synthesis of ideas and innovations, including several concepts of Peter Choyce anel Charles Kelman. This lens and variations made b\' several companies, including Pharmacia-Inte rm edic~ , Alcon, and Surgidev, among others, combine th e best features of th e Choyce four-point footplate fixation with desirable flexibility. The le ns has a Choyce-like lens shape with "cut outs" (arrows) between the optic anel th e haptics, which allows for appropriate flexibility and a gentle and physiological fit in the an terior chamber angle recess . If removal of the lens is necessary. the solid , spatula-like footpl ates usuall y slide easily out of th e angle recess . Note that th e haptics contain no positioning holes, a factor that is important when removal is necessary. Such holes may become incarcerated in the tissues of the angle recess and thus make removal ofthe IOL more difficult. Like almost all onepiece IOLs today, this lens is carefully manufactured and the surfaces are finished smoothly with tumblepolishing techniques (original magnification X 10).

to explant, if removal is necessary, than IOLs with small-diameter, round loops-both closed-loop and open-loop designs. Our data up to now strongly indicate that the modern, flexible, one-piece, all-PMMA lens designs with various modifications and refinements, introduced by Kelman and others, are generally safer and more efficacious than most other anterior chamber lens deSigns available today.

Croup 3: Rigid Anterior Chamber Lenses

Some of the original rigid anterior chamber IOLs, such as the various Choyce lenses used through many generations, have provided excellent results and are J CATARACT

(Apple) A recently manufactured Surgidev Corporation lens similar in design to the IOLAB Surefit shown in Figure 15A. This lens is in the testing stage (original magnification x 10).

still successful if correctly sized. However, there is little doubt in the minds of most surgeons that the flexibility built into the modern generation of anterior chambe r lenses has brought us one step closer to finding the ideal anterior chamber lens design. The problem of sizing has been greatly reduced, although not eliminated , thus decreasing postoperative IOLrelated complications. In the opinion of most surgeons, mode rn flexible anterior chamber lenses have replaced most rigid styles as the lenses of choice. The contribution of Peter Choyce with his innovative lens design should not be dismissed or forgotten. In many respects, some of the features that we include in our definition of a "best" anterior chamber lens are derived from the basic Choyce designs , particularly the Mark VIII and Mark IX lenses (Figure 14), with the added feature of flexibility (Figures 15A and 15B). The fact that the use of rigid anterior chamber lenses is steadily decreasing is not a reflection on Choyce's designs, but is simply the res ult of a natural and desirable evolutionary process.

Croup 4: Small Diameter, Round-Loop, Open-Loop Anterior Chamber Lenses

In this category we include a group of anterior cham ber lenses of varying designs, some uniplanar and some vaulted anteriorly. Most of these IOLs have a relatively low market share and are therefore difficult to evaluate in our study. Most lenses of this design have two-piece or multiple components with round, smalldiameter loops of either extruded PM MA or polypropylene that are staked. in holes drilled into the lens

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optic. The obvious major difference between these designs and the closed-loop IOLs of Group 2 is their open-loop configuration. Our laboratory findings show that this latter configuration is clearly preferable. Examples are the Pharmacia-Intermedics Dubroff model44B lens, the CooperVision-Cilco Novaflex style 680, the Copeland Radial lens model R03, and the Americal Shepard lens model 115. An inherent problem with all two-piece or multiplepiece IOL designs is that the loops have to be staked into the optic; in essence, modified sutures are attached to the lens. If the loops are bent or distorted at the loop-optic junction, significant changes in the anterior-posterior vault can occur. For example, external pressures from rubbing the eye may push the IOL posteriorly against the iris and pressure from behind the lens may push the lens forward. This may occasionally lead to the problem of corneal touch. The Pharmacia-Intermedics Dubroff model44B lens is the only IOL in this category shown in the bar graphs (Figures 8 and 9). This is because it is the only lens that we have received in sufficient numbers in our laboratory to evaluate and that has a large enough market share to make a meaningful comparison. This lens assumes an intermediate position in our schema. As we have previously emphasized, the Pharmacia-Intermedics Dubroff model 44B lens should be carefully distinguished from the inferior and ill-conceived copy of this design, the Surgidev style 63 lens. l Although these IOLs are not closed loop in configuration, the loops are basically small diameter, round sutures and are therefore susceptible to erosion into the angle. This may lead to synechial formation and encapsulation and incarceration of the peripheral portions of the loops. The entire length of the loop shafts, as they course between the optic and the angle recess, frequently rests in close approximation to or directly on the iris surface. Small-diameter, round loops in this position can cause a "cheese-cutter" effect, not only at their termination site at the angle recess but also more centrally, along the anterior surface of the mid-peripheral iris. The complications caused by this contact with the motile portions of the iris and the anterior cham ber angle recess are identical to those we have observed with closed-loop anterior chamber IOLs. It makes little difference whether the loops exert a compressive force directly on the face of the anterior chamber angle recess of the ciliary body, on the iris root, or more centrally in the mid-periphery of the iris or peripupillary zone of the iris. These sites all represent areas where a potential of excessive and deleterious uveal contact can occur. An anteriorly vaulted IOL, particularly a lens with smoothly finished loops or shafts (Figures 10 to 15B) that are broader or of slightly larger diameter than the standard sutures used with most 186

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looped IOLs would have less propensity toward this "cheese-cutter" effect on the iris. We do feel that at least some anterior vaulting built into anterior chamber IOLs is useful. Since some smalldiameter, round loop, open loop IOLs are uniplanar and are not vaulted, this lack might be considered an inherent design defect. However, according to our analyses to date, all of these lenses are now carefully manufactured with smooth surface and edge finish. No untoward incidence of complications that can be directly attributed solely to the uniplanar design has been detected. This comment does not apply to uniplanar lenses with poor quality finish. The status of the open-loop IOL designs in this group is inconclusive in terms of our objective laboratory findings. At this time it is difficult to form definitive conclusions about this particular group of IOLs either because we do not have sufficient numbers of accessioned specimens, the individual market shares of most are very low (hence available clinicopathologic data are difficult to obtain), or because some of these IOLs have been introduced so recently that insufficient follow-up data are available. However, the complications that have been clinically and pathologically documented in our series, although not of a sufficient incidence to lead to a general condemnation of this style, suggests the need for continued analyses and caution in choosing such IOL designs for implantation. If a surgeon is conducting a good patient follow-up and is satisfied with his or her results, particularly over the long term, continued use may be warranted. However, we do feel that patients implanted with small-diameter, open-loop anterior chamber IOLs should be carefully followed until a more definitive answer can be found.

Group 5: Lenses Designed for the Posterior Chamber, Placed in the Anterior Chamber Our findings regarding the status of the open, multiple-loop IOLs described in Group 4 were inconclusive, but we have no hesitation in expressing a strong objection to the implantation into the anterior chamber ofIOLs specifically designed for the posterior chamber. Unfortunately, this practice appears to be more common than literature reports would indicate. We agree with the literal definition of a posterior chamber lens: an IOL that is specifically designed and manufactured to be implanted in the posterior chamber only. Examples of these IOLs include, of course, the classic three-piece Shearing, Simcoe, Sinskey, and Kratz lens designs and numerous one-piece and multiplepiece variations. Most are flexible styles with polypropylene or extruded PMMA loops attached by insertion into a hole drilled into the optic. Most are engineered for placement in the larger space of the posterior chamber and generally have a lO-degree angulation. SeRG-VOL 13, MARCH 1987

Until recently, little attention was paid by most manufacturers to careful surface polishing of the optic and loop-optic junctions of posterior chamber le nse s. The implantation site for these IOLs is posterior to the iris surface and away from the delicate tissues of the anterior segment. In general, finish quality of posterior chamber IOLs is important but not as critical as with anterior chamber IOLs. We have seen numerous cases of severe complications caused by use of standard posterior chamber IOLs in the anterior chamber; for example, Figures 16 to 18. The lens in Figure 16 happens to be a Simcoe C-loop IOL , originally designed for posterior chamber implantation . The IOL in Figure 16 should not be confused with the more recently introduced Simcoe one-piece, allPMMA, C-loop anterior chamber IOL. This le ns, which was indeed specifically designed for placement in the anterior chamber, has satisfactory finish quality and the complication rate thus far seems to be lo'vv (Figures 8 and 9). Very few of these IOLs have had to be removed because of complications. Figures 17A to 17C also illustrate the proble ms caused by implantation of a posterior chamber IOL in the anterior chamber. In this case , astandard Shearing J-Ioop IOL was inserted into this chamber. The le ns loops eroded extensively into the uveal tissues (Figure 17B). A severe inflammation developed. A d ense secondarv membrane formed on the surface of the iris and exte;1ded over the optic, causing a "cocoon-like" opacification (Figure 17C). A total retinal detachment also occurred (Figure 17A). Some posterior chamber lenses have been only slightly modified for anterior chamber implantation. Examples of this type of variation are the 3M Corporation models 30 and 34 Sheets lenses. These IOLs have had an excellent success record for many years when fixated as originally intended behind the iris, usually in the lens capsular sac . The minor alterations made in this design (3M Corporation model 78 lens) to modify it for use in the anterior chamber are not adequate to make it safe or efficacious for placement in the anterior chamber. Since the Sheets design and its variations are closed-loop IOLs, when it is located in the confines of the anterior chamber it has the potential to create any or all of the problems associated with a closed-loop lens design (Figure 18; Table 2). There are several IOL designs marketed as "universal" lenses. It is claimed that these IOLs are safe for implantation in both the anterior and posterior chambers. Indeed, such IOLs as the Feaster Dualens have provided excellent results to date following both anterior and posterior chamber implantation. Our data are insufficient, however, to comment definitively regarding the suitability of any "universal" lens for either implantation site. The number of

Fig. 16.

(Apple) Gross photograph of a standard two-piece Simcoe C -Ioop posterior chamber lens with polypropylene loops. which was implanted in the anterior chamber of a 76-year-old man. The patie nt rapidly developed uveitis and PBK. Removal of the lens and penetrating keratoplasty were required 18 months postoperatively.

explanted specimens of this design are too few for us to discuss meaningfully the safety and efficacy of these IOLs. Because there is a significant difference in th e anatomic configuration of these two compartments of the eye, we have strong reservations about this hypothesis.

Fig. 17A.

(Apple) Low power overview of an enucleated globe into which an IOLAB Shearing-style J-Ioop posterior chamber l ens was implanted in the anterior chamber of a 71-year-old woman. Several complications ensued and th e eye became blind and painful. Enucleation was required for phthisis bulbi approximately two years postoperatively. A total funnel-shaped retinal detachment is shown in this photograph. A serous sub retinal transudate is present beneath the atrophic retina (H and E stain, original magnification X I).

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Fig. 17B.

Fig. 18.

(Apple) Photomicrograph of the anterior aspect of the globe in Figure 17A, showing the lens loop fixation site (arrow) of this posterior chamber IOL that had heen intentionally implanted in the antedor chamber. !';ote that the loop has eroded deeply into the stroma and muscle of the ciliary body. A dense fibrous me mbrane (arrowheads) is present on the anterior surface of the iris and along the loop and engulfs the lens optic. The ante rior chamber contains a dens e proteinaceous transudate (H and E stain, original magnification x 20).

(Apple) Scanning electron micrograph of an explanted Sheets closed-loop model 78 lens. The 3M Corporation modified their Sheets closed-loop posterior chamber lens for implantation in the antedor chamber. When this modified lens is implanted in the anterior chamber, the same problems occur that we have documented with any other small-diameter, round loop, closed-loop anterior chamber lens. Note that both loops required extensive cutting during removal. The original Sheets posterior chamber lenses (3M Corporation models .30 and 34 Sheets lenses) have provided excellent results f()r man\' years with posterior chamber fixation (original magnification x 10).

CONCLUSION Figure 1 documents that 54% of all explanted IOLs received in our ophthalmic pathology laboratory have been anterior chamber lenses. Some of these lenses were manufactured after 1975 (most after 1980) and all were explanted because of IOL-related complications. HiS

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Fig. 17C.

(Appl e) Photomicrograph of another section of the same eye showing a cut that includes th e left portion of the site of the lens optic. The optic used in this IOL is th e same design as the sharp-edged optic of th e Azar 91Z lens. A "cocoon" me mbrane courses along the ante rior surhlce of the iris and encloses the margins of the optic (arrows). This growth around the optic caused complete opacification of th e media (H and E stain , original magnification x 30).

The ratio of anterior chamber lenses to posterior cham ber lenses and iris support lenses has remained relatively constant since we began receiving specimens in late 1982. Anterior chamber lenses have been accessioned at a rate approximately two and one-half times that of posterior chamber IOLs (54% compared to 20% accessioned posterior chamber IOLs). Since over 80% of all implantations performed in the United States today involve posterior chamber IOLs, i.e., a greater than four to one ratio over anterior chamber lenses , the implication is that anterior chamber IOLs are removed at a 2.5 x 4, or a ten-fold, rate over posterior chamber IOLs. Without careful reflection , one could therefore hastily infer that anterior chamber IOLs in general may be as much as ten times more apt to cause complications than posterior chamber lenses. For several reasons this is an unreasonable and inaccurate conclusion . Some physicians have incorrectly interpreted our findings in this fashion , obviously forgetting or ignoring the many factors that modify such an inference. One should recall that many anterior chamber lens implantations are associated with complicated cases, e. g., cases with intraoperative complications, patients with preexisting ocular disease, or patients who have had previous surgery. There is a wide variation in surgical techniques and expertise, particularly when using the older intracapsular cataract extraction methods. In many instances, the complications that are often publiCized are caused by the inferior quality lenses we have considered in this article, There is no doubt that if the questionable IOLs that make up a SURG-VOL 13, MARCH 1987

large percentage of our series were eliminated, the overall complication rate for anterior chamber IOLs would be greatly reduced. Most published clinical data do support the impression of the majority of surgeons that posterior cham ber IOLs appear to provide better results and improved visual rehabilitation over the long term. It is rare to find a knowledgeable person who would question the immense success of modern posterior chamber IOLs. Having made this statement, however, one should not completely overlook the significant number of surgeons who have extensive experience with anterior chamber lens implantation as a primary procedure and who continue to report excellent results. A comprehensive poll of these surgeons as to their choice of lenses would be beneficial. Most physicians with whom we have discussed this topic have stated a preference for the one-piece designs. Follow-up time for patients implanted with today's high quality finish anterior chamber or posterior chamber IOLs is still relatively short. It might surprise the reader to note that even though the posterior chamber IOLs of Pearce, Harris, Shearing, Simcoe, and many others-the concepts and designs that revolutionized the specialty of IOL surgery-were introduced as early as the mid-1970s, truly high volume, nationwide implantation of these posterior chamber IOLs did not really gain impetus until well after 1980. The modified J-Ioop designs, the styles most commonly implanted today, were introduced by Sinskey and Kratz in 1980. Thus, the major transition to modern posterior chamber IOL surgery really occurred between 1980 (15% posterior chamber implantations) and late 1985 (83% posterior chamber implantations). Many of the modern anterior chamber lens designs, notably some of the best flexible Kelman lenses, were introduced during this same period. It may come as a surprise that when speaking in terms of a large volume of patients and noting that many of the patients implanted with the very early lenses are now deceased, the follow-up times of both anterior and posterior lens types in use today are roughly similar. We now have a baseline time frame, for practical purposes beginning around 1980 to 1982, from which we can evaluate large numbers of these patients. In addition, since each year younger patients are being implanted with IOLs, we will now have the opportunity for much longer follow-up studies with all lens types. Since we should now be removing the poor quality anterior chamber lenses from our inventories, we feel that further objective and comparative follow-up of present-day high quality anterior and posterior chamber lens implantation results will be extremely useful. The implantation of IOLs into the posterior chamber, regardless of design (e.g., present standard IOLs, soft

material IOLs, disc IOLs, injectable lenses), is a concept that will probably never be surpassed. However, as better anterior chamber lenses continue to become available and are used in their appropriate implantation site, postoperative results will be much better and the negative perception of anterior chamber lenses that we now possess will probably diminish. We emphasize that any movement to condemn all anterior chamber lenses universally appears premature and unwarranted. The reasons and indications for the occasional need to implant an anterior chamber lens are well known by implant surgeons. The main focus of this paper has been to point out that many of the adverse reactions reported with anterior chamber lenses must be considered in light of two facts: (1) Most anterior chamber IOLs are now implanted in complicated cases; (2) many physicians, both in clinical practice and in previous case reports, have failed to differentiate between anterior chamber IOLs that were well designed and those that have the negative features we have covered in this article. Such a lack of specificity about lens design has negatively biased earlier reports toward all anterior chamber IOLs. We will always have a need for anterior chamber lenses. It is therefore important that we continue to improve and develop new lens designs of the highest quality to fill this need. ACKNOWLEDGMENTS We are grateful for the valuable assistance of Lou H. Allred and Danine B. Davis in editing and typing the manuscript and li)r the technical assistance of Bryan Timmins in preparing the illustrations. The authors have no proprietary interest in any IOL design or lens company. This statement also applies to the Center for Intraocular Lens Research and the Departments of Ophthalmology and Pathology, University of Utah Health Sciences Center, Salt Lake City. REFERENCES 1. Apple DJ, Brems RN, Park RB, Kavka-Van Norman D, et al: Anterior chamber lenses. Part I: Complications and pathology and a review of designs. ] Cataract Refract Surg 13:157-174, 1987 2. Apple DJ, Olson RJ: Closed loop anterior chamber lenses. Arch Ophthalmol 105:19-20, 1987 3. Reidy JJ, Apple DJ, Googe JM, Richey MA, et al: An analysis of semiflexible, closed-loop anterior chamber intraocular lenses. Am Intraocular Implant Soc] 11:344-352, 1985 4. Mamalis N, Apple DJ, Brady SE, Notz RG, et al: Pathological and scanning electron microscopic evaluation of the 91Z intraocular lens. Am Intra-Ocular Implant Soc] 10:191-199, 1984 5. Isenberg RA, Apple DJ, Reidy JJ, Richards SC, et al: Histopathologic and scanning electron microscopic study of one type of intraocular lens. Arch Ophthalmol 104:683-686, 1986 6. Beehler CC: A review of 100 cases of flexible anterior chamber lens implantation. Am Intra-Ocular Implant Soc] 10:188-190, 1984 7. Beehler CC: Follow-up on the Stableflex lens. ] Cataract Refract Surg 13:84, 1987 8. Park SB, Kratz RP, Olson PF, Pfeffer BR, et al: In vivo fracture of an extruded polymethylmethacrylate intraocular lens loop. ] Cataract Refract Surg 13: 194-197, 1987

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