Corneal endothelial loss with new intraocular lenses

Analysis of aqueous humor calcium and phosphate from cataract eyes with and without diabetes mellitus

Purpose

To compare the levels of calcium and phosphorus in the aqueous humor and serum of diabetics and non-diabetics.

Methods

We divided patients into two groups: seventy-six non-diabetic cataract patients and fifty-two diabetic cataract patients. The diabetic group was divided again into three subgroups: twenty-six patients with no diabetic retinopathy, thirteen patients with non-proliferative diabetic retinopathy, and thirteen patients with proliferative diabetic retinopathy. The authors compared the levels of calcium and phosphorus in the serum and aqueous humor of cataract patients. Statistic analysis was performed to form two comparisons: 1) a comparison between non-diabetics and diabetics and 2) a comparison among non-diabetics and the three subgroups of diabetics.

Results

In serum, calcium levels did not statistically differ between non-diabetics and diabetics. The phosphorus level was also not significantly different. In the aqueous humor, however, while calcium levels did not differ significantly, the phosphorus levels in diabetics were considerably higher than those in non-diabetics. When non-diabetics were compared to the three diabetic subgroups, calcium levels did not differ in serum or aqueous humor, but the phosphorus levels in diabetics with proliferative diabetic retinopathy were significantly higher than those in non-diabetics, diabetics without diabetic retinopathy, and diabetics with non-proliferative diabetic retinopathy.

Conclusions

The level of phosphorus in the aqueous humor and serum of diabetics was significantly increased, especially in diabetics with proliferative diabetic retinopathy. This result may be related to hydrophilic acrylic IOL opacification. Future studies regarding the pathogenic role of a high concentration of aqueous humor and serum phosphorus are required.

Corneal endothelial cell damage from glaucoma drainage device materials

PURPOSE

To compare the level of endothelial damage caused by contact with materials used in contemporary glaucoma drainage devices and a phosphorylcholine polymer-coated PMMA (PC-PMMA). METHODS Standard-sized discs of silicone, PMMA (polymethylmethacrylate), and PC-PMMA (n = 6) were gently lowered onto cultured bovine corneal endothelial (BCE) monolayers using a vacuum suction device. A 2.4-g stainless steel cloning ring weight was then placed on top of each disc. The weights and discs were removed using a vacuum suction device and forceps after 5 minutes of contact. A 0.4% trypan blue solution was used to stain the cell monolayer to visualize the area of cell damage. The total area of damage in each well (including the area stripped of cells) was measured using an image processor and expressed as a percentage of the total disc area to derive a damage coefficient for each material. Damage coefficients for different materials were compared using Bonferroni corrected analysis of variance (ANOVA).

RESULTS

Percentage of areas of damage (mean +/- SD) after standardized contact were as follows: PMMA, 5.95 +/- 4.60%; silicone, 3.08 +/- 2.68%; PC-PMMA, 0.15 +/- 0.25%. PMMA caused marked endothelial cell damage. PC-PMMA discs produced a significantly lower level (p = 0.04) of endothelial cell trauma.

CONCLUSION

Our results suggest that PC coating technology may be effective in reducing the rate of corneal endothelial failure following GDD implantation.

Posterior capsule opacification and lens epithelial cell layer formation: Hydroview hydrogel versus AcrySof acrylic intraocular lenses

PURPOSE

To quantitatively compare the incidence of visually significant posterior capsule opacification (PCO) and lens epithelial cell (LEC) layer formation on the anterior surface of Hydroview hydrogel and AcrySof acrylic foldable intraocular lenses (IOLs) after implantation.

SETTING

Single-surgeon ophthalmology practice, Orange Base Hospital, and Dudley Private Hospital, Orange, New South Wales, Australia.

METHODS

This retrospective study comprised 166 eyes of 150 patients (after exclusions) who had cataract extraction and insertion of a foldable IOL in the capsular bag by a single surgeon using a standardized phacoemulsification technique from December 1997 to September 1998. The mean follow-up was 13.1 months (range 6.0 to 23.6 months). The eyes were divided into 2 groups based on the type of IOL implanted: Storz Hydroview H60M (81 eyes) or Alcon AcrySof MA30BA (85 eyes). A neodymium:YAG posterior capsule laser capsulotomy (PC YAG) was performed for an objective decrease in Snellen best corrected visual acuity (BCVA) of more than 1 line, significant visual symptoms, or both. This was used as a measure of visually significant PCO. An Nd:YAG anterior surface clearance (ASC YAG) was done for LEC layer formation anterior to the IOL to better visualize or facilitate treatment of PCO. The rates of PC YAG and ASC YAG after Hydroview and AcrySof IOL implantation were statistically compared.

RESULTS

Forty-five eyes (55.6%) in the Hydroview IOL group and 3 eyes (3.5%) in the AcrySof IOL group required a PC YAG; the risk difference was 52.0% (P <.001). An ASC YAG was required in 27 eyes (33.3%) in the Hydroview group and 1 eye (1.2%) in the AcrySof group; the risk difference was 32.2% (P <.001). Survival analysis demonstrated that the only independent predictor of the incidence of PC YAG and ASC YAG over time was IOL type, with the Hydroview IOL group having a statistically significantly higher incidence of both procedures.

CONCLUSION

There was a greater incidence of visually significant PCO and LEC layer formation on the anterior surface of Hydroview IOLs than of AcrySof IOLs.

12 year results of a prospective trial comparing poly(methyl methacrylate) and poly(hydroxyethyl methacrylate) intraocular lenses

PURPOSE

To compare long-term biocompatibility of single-piece poly(methyl methacrylate) (PMMA) and poly(hydroxyethyl methacrylate) (P-HEMA) intraocular lenses (IOLs).

SETTING

District General Hospital, United Kingdom.

METHODS

In a prospective trial of 250 eyes that had uncomplicated extracapsular cataract extraction, 2 groups of 125 eyes each were matched for age and sex. One group received single-piece looped PMMA IOLs and the other, single-piece solid-haptic P-HEMA IOLs. In all eyes, the IOLs were implanted in the capsular bag at the time of surgery using the envelope technique.

RESULTS

Twelve years after surgery, 75 eyes were available for examination. In the PMMA group (40 eyes), 50% had a visual acuity of 20/20 and 50% had intact capsules, many of them with a degree of fibrosis. In the P-HEMA group (35 eyes), 71% had an acuity of 20/20 and 80% had intact capsules (P = .0085).

CONCLUSION

In the long term, biocompatibility was better in the P-HEMA group than in the PMMA group.

Posterior capsule opacification and capsulotomy rates with taco-style hydrogel intraocular lenses

PURPOSE

To evaluate posterior capsule opacification (PCO) formation and neodymium: YAG (Nd:YAG) laser capsulotomy results in eyes with an logel intraocular lens (IOL).

SETTING

First University Hospital, Vienna, Austria.

METHODS

A retrospective study was done of 108 eyes with one of three types of an logel IOL that had decreased vision from PCO and required posterior capsule discission.

RESULTS

In general, in eyes with sulcus-placed IOLs, a Soemmering's ring formed and the capsulorhexis rim tightly adhered to the posterior capsule, sealing the capsular bag periphery. Elschnig pearls had broken the barrier, invading the retrolental space. In eyes with bag-placed IOLs, there was a gap between the IOL and posterior capsule in which Elschnig pearls had accumulated. This gap frequently extended beneath the flanges to the periphery of the capsular bag, allowing residual lens epithelial cells to proliferate and migrate centrally.

CONCLUSION

The logel lenses led to a high incidence of regeneratory PCO within the gap between the lens and capsule that might be the result of the properties of the lens' hydrogel material rather than its design.

Four year follow-up of the MemoryLens

PURPOSE

To determine whether the long-term results of implantation of thermoelastic MemoryLens intraocular lenses (IOLs) are comparable to those of conventional poly(methyl methacrylate) (PMMA) IOLs.

SETTING

St. Elisabeth Hospital, Dillingen, Germany.

METHODS

This retrospective study compared visual acuity, astigmatism, lens decentration, biocompatibility, and posterior capsule opacification in 36 eyes with a MemoryLens with those in 36 eyes with a conventional PMMA IOL over 4 years. The MemoryLenses were implanted in 1991 after cataract extraction by phacoemulsification.

RESULTS

Four years postoperatively, best corrected visual acuity was 20/20 to 20/25 in 63.9% of the MemoryLens group and 55.6% of the PMMA group. Mean astigmatism was 0.84 diopters (D) in the MemoryLens group and 1.20 D in the PMMA group. No cellular precipitates, as evaluated by biomicroscopy, or lens decentration greater than 0.5 mm were found in either group. Posterior capsule opacification, which developed in 22.2% in the MemoryLens group and 38.9% in the PMMA group, was treated with a neodymium: YAG laser capsulotomy.

CONCLUSION

The MemoryLens allows small incision cataract surgery and long-term results that compare favorably with those of PMMA IOLs.

Comparison of the postoperative inflammatory response in the normal eye with heparin-surface-modified and poly(methyl methacrylate) intraocular lenses

Evidence that poly(methyl methacrylate) (PMMA) is not inert in the eye has led to the introduction of intraocular lens (IOL) surface modification. In this prospective, double-blind, randomized study, we evaluated the effects of heparin surface modification (HSM) on anterior segment inflammation for one year after endocapsular cataract surgery. Fifty-four eyes were randomized to receive an HSM IOL (29 eyes) or a PMMA IOL (25 eyes) and were assessed postoperatively by corneal endothelial photography, laser flare and cell measurements, fluorophotometry, and IOL surface specular microscopy. Corneal endothelial loss, mean aqueous flare and cells, and fluorophotometry did not differ significantly between the groups, although fewer eyes in the HSM group had high flare values on the first postoperative day. The number of giant cells was significantly less in the HSM group for up to one year after surgery. Although there was no statistical difference in overall visual outcome, more patients in the HSM group (17%, 5/29) achieved a postoperative visual acuity of 20/15 than in the PMMA group (0). These results demonstrate that HSM enhances IOL biocompatibility and these effects are detectable in the low-risk, normal eye.

Preliminary results with a new hydrogel intraocular lens

The merits of hydrogel as an intraocular lens material are that it is soft, foldable, hydrophilic, autoclavable and more biocompatible than polymethylmethacrylate (PMMA). Twenty eyes were implanted with a new hydrogel design after phacoemulsification. Fifty per cent achieved a corrected acuity of 6/5 and all achieved 6/9 with correction. Results confirmed an excellent biocompatibility of the material but two cases of asymptomatic decentration indicated the occasional instability within the capsular sac. For best results the hydrogel requires an intact capsulorrhexis with a diameter between 4.5 and 5.0 mm.

Evaluation of 100 consecutive IOGEL 1003 foldable bag-style lenses implanted through a self-sealing tunnel incision

The IOGEL 1003 hydrogel lens, designed for better capsular bag fit, was implanted in 100 consecutive eyes. We evaluated the visual and morphological results obtained with a mean follow-up of six months. Visual acuity was within Food and Drug Administration standards; however, morphological results were less satisfactory. Decentration of 1 mm or more occurred in 24% of the cases. Higher diopter lenses required a minimum incision size of 4 mm and tended to tear when folded. Once in the eye, they regularly came in contact with the iris. A gap between the posterior optic surface and capsule occurred in 61% of eyes. Within the short follow-up period, 9% of eyes required YAG discission because of Elschnig pearl formation. In conclusion, the newer IOGEL 1003 lens performed no better than earlier IOGEL lens models when placed in the bag, and the possible benefit of decreasing posterior lens subluxation after early YAG capsulotomy is offset by the disadvantages.

Adherence of human lens epithelial cells to conventional poly(methyl methacrylate), heparin-surface-modified, and polyHema lenses

We developed an in vitro model to assess the adherence of human lens epithelial cells to three types of intraocular lenses: poly(methyl methacrylate) (PMMA), heparin-surface-modified PMMA (HSM-PMMA), and polyHema. Lenses were incubated with a fixed number of human lens epithelial cells. Adherent cells were counted after 72 hours in culture. Scanning electron microscopy showed significantly fewer cells adhering to the HSM-PMMA and polyHema lenses than to the PMMA lenses (P < .01). Repeat experiments on cell lines established from different donors confirmed these findings.

Exchange of IOGEL hydrogel one-piece foldable intraocular lens for bag-fixated J-loop poly(methyl methacrylate) intraocular lens

In 1990, IOGEL lenses placed in the capsular bag were reported to displace into the vitreous after neodymium:YAG (Nd:YAG) laser capsulotomy. We exchanged a bag-placed IOGEL lens in one patient after erroneous biometry and capsular opacification. The technique and results of lens explantation, aspiration of Elschnig pearls, and in-the-bag implantation of a modified J-loop poly(methyl methacrylate) (PMMA) lens are demonstrated. Removal of the soft and nonadhesive IOGEL lens was easy. The capsule pockets held patent by the flanges of the taco-style IOGEL lens allowed for easy insertion and bag fixation of the J-style loops. Visual acuity improved from 20/60 to 20/20. Centration of the exchange IOL was satisfactory. In a series of 61 Nd:YAG laser posterior capsulotomies, we did not observe the reported tendency of IOGEL lenses to luxate posteriorly. Therefore, we recommend Nd:YAG discission of the posterior capsule as the preferred approach to posterior capsule opacification with IOGEL lenses. However, the technical ease of the technique makes the explantation and replacement of IOGEL lenses by a bag-fixated PMMA IOL a valid option to correct an erroneous biometry.

Evaluation of 200 consecutive IOGEL 1103 capsular-bag lenses implanted through a small incision

We evaluated 200 consecutive IOGEL 1103 capsular bag intraocular lenses. We performed a 5 to 6 mm capsulorhexis and inserted the intraocular lens (IOL) through a 3.5 to 4.0 mm scleral tunnel with a Faulkner folder. Twenty-two cases were combined with trabeculectomy and ten with keratoplasty using a temporary keratoprosthesis. Mean follow-up was six months. The implant centered well and resisted capsular shrinkage. Iris touch to the optic was rare and did not provoke persistent pigment dispersion. In one third of the cases a cleft was discernible between the posterior convex IOL surface and the extended capsule despite thorough aspiration of viscoelastic and debris from the retrolental space. In 8% of cases, white flakes of unknown origin were observed at the IOL-capsule interface. In cases associated with pre-existing iritis or intraoperative iris trauma (iris manipulation, iridectomy, or synechiolysis in glaucoma patients), fibrin exudation as well as iridocapsular synechial formation and macrophage precipitation often ensued. Cellular precipitates, as evaluated by biomicroscopy and specular microscopy, were less pronounced and more transient than on poly(methyl methacrylate) IOLs. Best case visual acuity results were comparable to those with conventional implants; all eyes attained 20/40 or better and 97% achieved 20/25 or better. The 1103 was easier to implant through a capsulorhexis opening and suited the dimensions of the capsular bag better than the PC-12 model.

In vitro and in vivo evaluation of a hydrophilized silicone intraocular lens

The surface of a silicone-disc intraocular lens (IOL) was hydrophilized by plasma etching (oxygen plasma) and compared to an untreated but otherwise identical IOL. Various methods of surface analysis were used to characterize the modification (e.g., X-ray photoelectron spectroscopy, contact angle estimation). A cytotoxic effect of the modified surface was excluded by cell culture experiments evaluating cell spreading, cell morphology, DNA and protein synthesis. In vivo experiments on rabbits indicated that the postoperative foreign-body reaction was not significantly affected by the hydrophilization of the IOL surface. Throughout the entire follow-up (12 weeks) we found less induced posterior synechias in the eyes with hydrophilized lenses than in those with untreated lenses (P = .009). While the IOL dislocations out of the capsular bag and the posterior capsular opacification rate did not differ significantly between the two groups of eyes, we did see special patterns of posterior capsular opacification on the posterior capsules of eyes with the hydrophilized IOL.

A comparison of 141 polymacon (Iogel) and 140 poly(methyl methacrylate) intraocular lens implants

In a prospective controlled trial 290 consecutive patients were randomly allocated a polymacon or a poly(methyl methacrylate) (PMMA) intraocular lens. Early Treatment of Diabetic Retinopathy Study (ETDRS) acuity charts gave similar results with both lenses. However Pelli-Robson contrast sensitivity charts gave a better result with PMMA lenses. Polymacon lenses appeared to remain free of any adhesions after implantation raising the question of long term stability. Four patients experienced problems related to this, three involved total lens dislocation. Seven patients developed early 'fibrin' membranes coating the polymacon lens, of which three were florid.

Animal model experimentation using the expansile hydrogel intraocular lens

To determine the biocompatibility of the expansile hydrogel intraocular lens, a two-year animal study was undertaken. After phacoemulsification, hydrogel expansile intraocular lenses were implanted in four Dutch-belted rabbit eyes. Slitlamp examinations revealed minimal anterior chamber reaction and lens synechias. Gross pathology and histology demonstrated hyperplastic residual cortex, but confirmed our clinical impression that the lenses were well tolerated. Electron diffraction energy dispersive X-ray microanalysis revealed deposition of aluminum, silicon, magnesium, and calcium, but there was no evidence of matrix penetration.

Lens epithelial cells adhere less to HEMA than to PMMA intraocular lenses

Following cataract surgery proliferation of residual lens epithelial cells may occur causing secondary opacification and loss of visual acuity. Using an in vitro system the abilities of bovine and porcine lens epithelial cells to adhere to two types of intraocular lens have been assessed. Lens epithelial cells adhere significantly less to lenses composed of poly 2 hydroxyethylmethacrylate (HEMA) than to polymethylmethacrylate (PMMA).

Early results with the 8 mm and 9 mm HEMA disc intraocular lens

This study presents our experience with 34 HEMA disc intraocular lenses implanted in the capsular bag. Despite the small number of cases and the relatively short mean postoperative follow-up of nine months, the results show a low incidence of uveitis and capsular fibrosis and excellent biocompatibility. The following complications were observed: four luxations of the 8 mm lens and one of the 9 mm lens in the anterior chamber. A visual acuity of 20/20 to 20/40 was obtained in 32 patients (94%).

Evaluation of 150 consecutive cases of poly HEMA posterior chamber lenses implanted in the bag using a small-incision technique

We report the results of 150 capsular bag implantations of the IOGEL PC-12 hydrogel lens. Mean follow-up was seven months. Following capsulorhexis and phacoemulsification, a Faulkner folder was used to insert the lens through a 3.5 mm to 4.0 mm scleral tunnel incision. Initially, a number of surgical complications were encountered. Because of increasing experience and modified instrumentation and technique, these did not occur in the later cases. Visual results were good, all eyes gaining a best case visual acuity of 20/40 or better and 97% achieving 20/25 or better. Morphological results were satisfactory. Generally the lenses remained centered and at a distance from the iris. Retention of viscoelastic substance or debris between the lens and the posterior capsule, occasionally observed at the start of the series, has been avoided by retrolental aspiration. Persistent pigment dispersion, which was observed when the lens had been implanted in the sulcus, was not seen. Tolerance of the lens material was generally satisfactory. There were six cases (4%) of fibrinoid uveitis, which is a relatively high incidence. From our experience and results we conclude that this implantation procedure allowed controlled insertion and placement of the IOGEL lens, provided that adequate instrumentation and technique was used; visual performance was comparable to that of poly(methyl methacrylate) lenses; capsular bag fixation furnished satisfactory morphological results, provided an adequately shaped capsulorhexis was performed.

Laser-induced damage to transparent polymers: chemical effect of short-pulsed (Q-switched) Nd:YAG laser radiation on ophthalmic acrylic biomaterials. I. A review

The use of short-pulsed lasers in ophthalmic surgery inspired and called for research on the damage inflicted by the laser radiation upon the acrylic polymers from which artificial intraocular lenses are made. The possible release of toxic monomers by laser-induced depolymerization is of great concern but past investigations of this phenomenon have been very limited. The present knowledge of various types of laser-induced damage to transparent polymers is reviewed with particular emphasis on the acrylic materials and intraocular lenses.

The corneal endothelium

The endothelium is a monolayer of cells on the posterior corneal surface that transports water from the stroma into the anterior chamber. This movement of water counters a natural tendency for the stroma to swell and is necessary to maintain a transparent cornea. Embryologic studies, in particular the demonstration of the derivation of the endothelium from the neural crest, have provided insight into the factors that govern the response of this tissue to disease. In some species the endothelium can regenerate after injury, but in man cellular enlargement is the main mechanism of repair after cell loss. A clinical estimate of endothelial cell density and function is provided by specular microscopy, fluorophotometry and pachymetry. In this paper we review the development, structure and function of the corneal endothelium, and then consider the pathological processes that can affect this tissue.

Modified triple procedure using a temporary keratoprosthesis for closed-system, small-incision cataract surgery

In patients with corneal disease and cataract, the combined surgical approach yields quick rehabilitation and excellent visual results. Working on an open eye for cataract removal and posterior chamber lens implantation, however, makes the procedure risky and difficult. Using a temporary keratoprosthesis and a small-incision technique, surgery can be performed in a fully closed system, optimizing the safety and precision of the procedure.

Results of the intercapsular technique with the IOGEL lens

Standard biconvex 12 mm diameter IOGEL PC-1 hydrogel intraocular lenses were inserted into the eyes of 55 patients using intercapsular in-the-bag placement and extracapsular ciliary sulcus placement. All patients had senile cataracts. Endothelial specular microscopic assessment was performed preoperatively and postoperatively at six and 12 months. Viscoelastic agents were not used in any of the cases and upper haptic positioning was achieved with dialing and irrigation and iris retraction in each group, respectively. Major complications in both groups were iridocapsular synechias. This resulted in dislocation of a single haptic into the anterior chamber angle in one ciliary-sulcus-placed lens and in an updrawn pupil in one of the intercapsular cases. Pigment dispersion syndrome occurred in one case with a ciliary-sulcus-placed lens. In one case in each group a Nd:YAG laser posterior capsulotomy was performed. Whereas the visual results in each group were similar, the percentage cell loss was significantly greater in the group with lenses in the ciliary sulcus at six months postoperatively. The lower cell loss in the intercapsular group was attributed to the protective effect of the anterior capsule on the endothelium during the major intraocular manipulations.

Advantages and limitations of current soft intraocular lenses

We report our clinical experience with six soft intraocular lenses: (1) STAAR silicone, (2) CooperVision/Schlegel silicone, (3) IOLAB silicone, (4) Allergan Medical Optics (AMO) silicone, (5) Fyodorov silicone, and (6) Alcon hydrogel (IOGEL). We found that these soft intraocular lenses have several common design problems. The single-size design of five of the six soft lenses can lead to a windshield-wiper decentration effect in lenses too small for larger eyes. We observed several instances in which the one-piece lenses became decentered, subluxed, and vaulted anteriorly against the iris or posteriorly away from the iris as postoperative capsulozonular changes occurred. We found that the insertion methods for these soft lenses need refining to reduce the risk of intraocular damage and wound stretching if the lenses are to be folded and inserted through a small 3.0 mm to 3.5 mm incision. The surface and physical characteristics of these lenses may also require further study. We observed folding grooves, sebacium deposits, and rust from the insertion instrument on some lenses inside the postoperative eye and pigment dispersion associated with hydrogel lenses. We conclude that small diameter polymethylmethacrylate implants are the best choice for small incision cataract surgery at this time.

Hydrogel intraocular lens experience with endocapsular implantation

The experience is presented of three independent surgeons using Hydrogel posterior chamber intraocular lenses in a combined series of 157 endocapsular cataract extractions. One hundred and fifty of these eyes were examined after a minimum follow-up period of one year and 92.0% achieved visual acuity of 6/12 or better, and 98.6% achieved this if pre-existing pathology was excluded. Insertion of this lens has proved to be simple, the adaptions of technique required are described and the complications are presented and analysed.

Capsular bag implantation of the hydrogel lens

Fifty hydrogel lenses were implanted in the capsular bag. Six months after surgery, 96% of eyes had visual acuities of 20/30 and 40% had acuities of 20/15. The age range of patients was 65 to 92 years (mean 76 years). Such visual satisfaction is rarely achieved in this age group and appeared to be related to the low incidence of uveitis and capsular fibrosis associated with these lenses. Excellent lens centration was maintained in 82% of eyes. Despite the small number of cases and short follow-up, these preliminary results merit attention from the medical profession.

Multicenter trial of an intraocular hydrogel lens implant

Several features suggest that hydrogels may have potential advantages as an intraocular lens material. The IOGEL lens is a single piece hydrogel composed of 38% poly HEMA. Clinical experience with the IOGEL lens in Australia has been published, and the safety and efficacy of the lens is currently being investigated in a multicenter trial in Europe, the U.S.A., Canada, Australia, and Japan. This is the first large-scale study of a hydrogel implant. The IOGEL lens clinical study was initiated in May 1986 in Europe, in September 1986 in the U.S.A., and in November 1986 in Canada and Australia. The enrollment progress in May 1987 showed that 501 cases had been implanted in Europe, Canada, and Australia and 100 cases in the U.S.A. The visual acuity outcome is equivalent to that reported in the literature. Patients in the multinational trial achieved 20/40 or better in 86% of cases and in 96% of cases excluding unrelated pathologies. Although hydrogels have only had limited use in the clinical situation, the results of this study suggest that the IOGEL lens is a viable alternative to polymethylmethacrylate lens implants.

Soft intraocular lenses

An in-depth review of the current status of soft intraocular lenses (IOLs) is presented. We have outlined the historical aspects of IOL development from polymethylmethacrylate material to newer soft polymers such as silicones and hydrogels. Chemical, physical, and biomaterial properties as well as the advantages and disadvantages of these materials and lenses are discussed. Clinical results from international investigators are presented, along with some thoughts about future trends in small incision cataract surgery and IOL substitutes.

Early experience with soft hydrogel lens implants

A new material which more closely mimics the properties of living tissue than polymethylmethacrylate is under investigation. Twelve hydrogel lenses were placed into the ciliary sulcus following the standard nucleus extraction technique and 38 were placed into the lens capsule using the endocapsular technique. Six months following surgery 66 per cent of sulcus fixated lenses were found to have both haptics in the sulcus and 76 per cent of capsule fixated lenses were found to have both haptics encapsulated. The hydrogel lens was found to be well tolerated within the eye with 32 per cent of eyes achieving a visual acuity of 6/5 and 94 per cent achieving 6/12 or better.

Clinical results of hydrogel lens implantation

Polymethylmethacrylate has proven to be a useful intraocular lens (IOL) implant material and remains the most widely used material for the fabrication of IOLs. Complications, however, from IOL implantation still occur. A hydrogel lens has been designed for posterior chamber placement. A clinical study from August 1983 to June 1985 was undertaken to determine the safety and efficacy of this new lens manufactured from 38% poly HEMA. The noninflammatory postoperative complications were limited to lens decentration and opacification of the lens capsule. Three cases of posterior capsule opacification required YAG laser capsulotomy. Laser capsulotomy is feasible and the lens appeared to be more resistant to damage from the YAG laser than polymethylmethacrylate lenses. In general, the material appeared to be well tolerated and there have been no cases of persistent iritis or clinically detectable cystoid macular edema. If the visual acuity outcome by age decade for all patients irrespective of follow-up time is considered, 92% of patients achieved 20/40 or better corrected visual acuity.

Long term observations on an anterior chamber Ridley intraocular lens

In 1965 the patient, aged 6, sustained a perforating eye injury which was repaired and a traumatic cataract was aspirated within five weeks. Five years later a Ridley Mk 2 A/C intraocular lens was inserted. Several episodes of blunt trauma occurred over a three year period following this procedure. This paper reports the clinical, corneal pachometric and specular microscopic findings of both traumatized and normal fellow eyes 18 years after the initial incident. The corneal endothelial mosaic of the traumatized right eye was very irregular in the vicinity of the initial site of perforation. These marked variations in cell size and shape were less apparent at peripheral corneal areas. The estimated cell loss to the traumatized eye was in the region of 74% although in spite of this corneal function was maintained. The effects of trauma on the corneal endothelium are discussed and a brief review of the literature presented.

Early experience with STAAR silicone elastic lens implants

Silicone elastic intraocular lens implants (STAAR Model B) were implanted in 18 human eyes following extracapsular cataract extraction by phacoemulsification. Visual acuity of 20/40 or better was obtained in 17 eyes which had no preexisting pathology. Implants decentered and tilted in five of six eyes in which implants were placed in the bag. This was the only significant complication observed and is prevented by avoiding in-the-bag placement of the implant.