Pseudophakic bullous keratopathy

Corneal endothelial cell dysfunction: etiologies and management

A transparent cornea is essential for the formation of a clear image on the retina. The human cornea is arranged into well-organized layers, and each layer plays a significant role in maintaining the transparency and viability of the tissue. The endothelium has both barrier and pump functions, which are important for the maintenance of corneal clarity. Many etiologies, including Fuchs’ endothelial corneal dystrophy, surgical trauma, and congenital hereditary endothelial dystrophy, lead to endothelial cell dysfunction. The main treatment for corneal decompensation is replacement of the abnormal corneal layers with normal donor tissue. Nowadays, the trend is to perform selective endothelial keratoplasty, including Descemet stripping automated endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty, to manage corneal endothelial dysfunction. This selective approach has several advantages over penetrating keratoplasty, including rapid recovery of visual acuity, less likelihood of graft rejection, and better patient satisfaction. However, the global limitation in the supply of donor corneas is becoming an increasing challenge, necessitating alternatives to reduce this demand. Consequently, in vitro expansion of human corneal endothelial cells is evolving as a sustainable choice. This method is intended to prepare corneal endothelial cells in vitro that can be transferred to the eye. Herein, we describe the etiologies and manifestations of human corneal endothelial cell dysfunction. We also summarize the available options for as well as recent developments in the management of corneal endothelial dysfunction.

Transient temperature distribution on the corneal endothelium during ophthalmic phacoemulsification: a numerical simulation using the nodeless variable element

Background: During cataract operation (phacoemulsification), a phaco needle-tip is inserted into the anterior chamber of eye. Then, heat is generated by the oscillation of the phaco needle, which may injury the corneal endothelial cells. There are no data available for temperature responses at the corneal endothelium to heat from the phaco needle during phacoemulsification. Objective: Investigate temperature distribution on the corneal endothelium during ophthalmic phacoemulsification using numerical simulation, and compare the transient temperature response to heat between balanced salt solution (BSS) and ophthalmic viscoelastic device (OVD), Viscoat®. Methods: Heat flux from a phaco needle was measured with thermal properties of BSS and AVS in an experimental setting. Then, nodeless variable finite element method was applied to predict temperature changes in the eye by the phaco needle inserted into the anterior chamber. The transient temperature distribution on the corneal endothelium was calculated at 10, 20, and 30 seconds after heat generation by the needle. Results: The heat generation of phaco needle without sleeve cover was 1.6 kW/m2. The numerical simulation showed that the maximum temperature occurs on the wound location at all times after heat generation by the phaco needle. Especially, at time 30 seconds, it was 49.2 and 41.7°C in BSS and OVD, respectively. The temperature elevation by the phaco needle was lower in OVD than BSS. Conclusion: Phacoemulsification is a heat-generating procedure performed between the anterior chamber structures of eye. During this procedure, OVD may protect the corneal endothelium against heat better than BSS.

Comparisons of Visual and Surgical Outcomes after Reuse or Replacement of Dislocated in-the-Bag Intraocular Lens

Purpose

To compare the visual and surgical outcomes after a reuse or a replacement of a dislocated in-the-bag intraocular lens (IOL).

Methods

This was a retrospective, nonrandomized case series at a single ophthalmological institution. Cases with an in-the-bag dislocation of an IOL were treated by pars plana vitrectomy and the reuse or the replacement of the IOL. The lens was held by intrascleral fixation of the haptics of the IOL under both conditions. The same dislocated IOL was reused in 6 eyes (group A) or it was replaced with another IOL in the other 9 eyes (group B). The pre- and postoperative parameters analyzed included the visual acuity, refractive error, corneal endothelial cell density, and intraocular pressure (IOP).

Results

There was no significant difference between the two groups in the postoperative visual acuity (P = 0.388), refractive error (P = 0.955), IOP (P = 0.529), and endothelial cell loss (P = 0.940). A breakage or a tilting of the IOL was observed and required replacement in three eyes in the reuse group (P = 0.044).

Conclusions

Half of the cases with reused in-the-bag dislocated IOL had a breakage or a tilting of the IOL. The replacement of the in-the-bag dislocated IOL is better than the reuse of the IOL with intrascleral haptics fixation.

Optical System Design for Noncontact, Normal Incidence, THz Imaging of in vivo Human Cornea

Reflection mode Terahertz (THz) imaging of corneal tissue water content (CTWC) is a proposed method for early, accurate detection and study of corneal diseases. Despite promising results from ex vivo and in vivo cornea studies, interpretation of the reflectivity data is confounded by the contact between corneal tissue and dielectric windows used to flatten the imaging field. Herein, we present an optical design for non-contact THz imaging of cornea. A beam scanning methodology performs angular, normal incidence sweeps of a focused beam over the corneal surface while keeping the source, detector, and patient stationary. A quasioptical analysis method is developed to analyze the theoretical resolution and imaging field intensity profile. These results are compared to the electric field distribution computed with a physical optics analysis code. Imaging experiments validate the optical theories behind the design and suggest that quasioptical methods are sufficient for designing of THz corneal imaging systems. Successful imaging operations support the feasibility of non-contact in vivo imaging. We believe that this optical system design will enable the first, clinically relevant, in vivo exploration of CTWC using THz technology.

Contributions of tissue-specific pathologies to corneal injuries following exposure to SM vapor

Corneal injuries resulting from ocular exposure to sulfur mustard (SM) vapor are the most prevalent chemical warfare injury. Ocular exposures exhibit three distinct, dose-dependent clinical trajectories: complete injury resolution, immediate transition to a chronic injury, or apparent recovery followed by the subsequent development of persistent ocular manifestations. These latter two trajectories include a constellation of corneal symptoms that are collectively known as mustard gas keratopathy (MGK). The etiology of MGK is not understood. Here, we synthesize recent findings from in vivo rabbit SM vapor studies, suggesting that tissue-specific damage during the acute injury can decrement the regenerative capacities of corneal endothelium and limbal stem cells, thereby predisposing the cornea to the chronic or delayed forms of MGK. This hypothesis not only provides a mechanism to explain the acute and MGK injuries but also identifies novel therapeutic modalities to mitigate or eliminate the acute and long-term consequences of ocular exposure to SM vapor.

Alternatives to corneal transplantation for the management of bullous keratopathy

PURPOSE OF REVIEW

Corneal transplantation remains the gold-standard treatment for bullous keratopathy patients as it provides symptomatic relief and visual rehabilitation. As corneas are not always available for transplant, alternative treatments have to be considered for alleviation of discomfort and pain.

RECENT FINDINGS

Various treatment options available in such cases include conjunctival flaps, anterior stromal puncture, amniotic membrane transplantation, phototherapeutic keratectomy, bandage contact lenses, and hypertonic saline eye drops. A combination of the above treatments can be employed depending upon the severity of bullous keratopathy and co-existing corneal edema. New potential treatments include collagen cross-linking (CXL), cultured endothelial cell injection, and topical treatment with Rho-associated kinase (ROCK) inhibitor.

SUMMARY

There is a lack of clinical trials comparing the safety and efficacy of the currently available treatment options for the management of bullous keratopathy. The effect of these treatments on subsequent corneal transplant has not been observed. CXL seems to offer short-term benefit for relief of pain. Newer potential treatment modalities such as ROCK inhibitors are claimed to be useful for the reversal of early edema associated with corneal endothelial dysfunction; however, long-term clinical trials are awaited.

Effects of argon laser iridotomy on the corneal endothelium of pigmented rabbit eyes

Purpose

In Asian countries, laser iridotomy for the treatment of angle-closure glaucoma is a common cause of bullous keratopathy, which may be associated with a shallow anterior chamber and dark iris pigmentation in Asians. Several cases of corneal decompensation after argon laser iridotomy have been reported. In the present study, we evaluated the harmful effects of argon laser iridotomy on the corneal endothelium.

Methods

Argon laser iridotomy was performed on the right eyes of pigmented rabbits. Changes in corneal thickness and endothelial cell density after laser iridotomy were evaluated. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed for assessment of corneal endothelial cell apoptosis. Combined staining with alizarin red and trypan blue, as well as a live/dead cell assay, were performed for evaluation of damage to the corneal endothelium induced by laser iridotomy.

Results

Corneal thickness did not change immediately after laser iridotomy; however, a significant increase was observed 24 hours after iridotomy (p = 0.001). The endothelial cell density of laser-treated eyes four days after laser iridotomy was significantly decreased compared with control eyes (p < 0.001). TUNEL staining showed many TUNEL-positive cells in the corneal endothelium and corneal stroma. No endothelial trypan blue-stained cell nuclei were observed after laser iridotomy; however, several large endothelial cells with damaged membrane integrity were observed. The live/dead cell assay clearly showed a large number of dead cells stained red in several areas throughout the entire corneal button 24 hours after iridotomy.

Conclusions

Argon laser iridotomy induces corneal endothelial cell apoptosis in pigmented rabbit eyes, resulting in decreased endothelial cell density.

Tear lipocalin captures exogenous lipid from abnormal corneal surfaces

Purpose. The cornea is protected by apical hydrophilic transmembrane mucins and tears. In pathologic states the mucin barrier is disrupted, creating potential for meibomian lipids to adhere more strongly. Undisplaced lipids create an unwettable surface. The hypothesis that pathologic ocular surfaces alter lipid binding and the ability of tear proteins to remove lipids was tested. Methods. Corneas with pathologic surfaces were studied for lipid adhesion and removal by tears. Capture of fluorescence-labeled phospholipids by human tears was assessed by steady state fluorometry. Tear proteins were separated by gel filtration chromatography and analyzed for bound lipids. Results. Contact angle measurements revealed strong lipid adherence to corneas submerged in buffer. Lower contact angles are observed for lipids on completely de-epithelialized corneas compared with intact corneas (P = 0.04). Lipid removal from these surfaces is greater with whole tears than with tears depleted of tear lipocalin (P < 0.0005). Significantly fewer lipids are captured by tears from Bowman's layer than from epithelial-bearing surfaces (P < 0.025). The only tear component to bind the fluorescence-tagged lipid is tear lipocalin. The histology of a rare case of dry eye disease demonstrates the dominant features of contemporaneous bullous keratopathy. Lipid sequestration from this cornea by tear lipocalin was robust. Conclusions. Lipid is captured by tear lipocalin from corneas with bullous keratopathy and dry eye. Lipid removal is slightly abrogated by greater lipid adhesion to Bowman's layer. Reduced secretion of tear lipocalin documented in dry eye disease could hamper lipid removal and exacerbate ocular surface pathology.

Exfoliative epitheliopathy of bullous keratopathy with breaches in the MUC16 Glycocalyx

PURPOSE

Expression of cellular adhesion molecules is altered in bullous keratopathy. The hypothesis that epithelial alterations in bullous keratopathy compromise the surface of the cornea and its glycocalyx was tested.

METHODS

Studies were performed on eight cases each of pseudophakic bullous keratopathy and healthy corneas. The number of epithelial cell layers was determined with a stereological method of point counting. The minimum distance between points was established by estimates of cell size with variable pressure scanning electron microscopy performed in backscatter mode. The mean number of cell layers with mucin expression was identified by immunohistochemistry with mouse monoclonal antibodies for MUC1 and MUC16. Data were analyzed by Student's t-test if values showed a normal distribution or, alternatively, by the Wilcoxon rank-sum test.

RESULTS

Mean numbers of wing cell and superficial cell layers were lower in bullous keratopathy specimens (1.6 vs. 2.0; P < 0.0001) than in controls (1.1 vs. 1.8; P < 0.000001). The number of exfoliated cell layers evident in sections was increased in the bullous keratopathy specimens compared with controls (0.36 vs. 0.03; P < 0.0001). The number of cell layers decorated with antibodies to MUC16 was lower in bullous keratopathy specimens than in controls (0.5 vs. 1.2; P < 0.025). The reduction of layers expressing MUC1 in bullous keratopathy was not statistically significant.

CONCLUSIONS

Pseudophakic bullous keratopathy manifests an abnormal corneal ocular surface in which superficial cell layers are exfoliated, leaving breaches in the protective MUC16 glycocalyx. The results provide a morphologic correlate for the surface epithelial abnormalities noted clinically in these patients.

Histopathological Diagnosis of Corneal Button Specimens: An Epidemiological Study

PURPOSE

To determine the most common histopathological diagnosis of corneal specimens from penetrating keratoplasty (PKP).

METHODS

The records of 500 corneal specimens submitted to biopsy at the Henry Witelson Ocular Pathology Laboratory, Montreal, Canada, from 1999 to 2004 were reviewed. Age, sex, clinical indications, and histopathological findings were analyzed.

RESULTS

Chronic keratitis (45.6%) was the most common pathological diagnosis, followed by corneal edema (25.8%), dystrophy (12.8%), keratoconus (KC) (9.2%), acute keratitis (5.6%), and degeneration (1.0%). Among the specimens with chronic keratitis, regraft was the most common clinical indication (39.0%). In the group of acute keratitis, ulcerative condition was the leading cause (75,0%). Fuchs' endothelial dystrophy represented 79.7% of the clinical diagnoses in the group of corneal dystrophies. The median patient age was 70-79 years, and the gender distribution was nearly symmetric.

CONCLUSION

The present study is important for determining the most common histopathological diagnoses of corneal button specimens and the correlation with the age, gender, and clinical indications of PKP.

Histopathologic study of changes occurring in eyes with intraocular lens implantation: autopsy eyes, enucleated eyes and corneal buttons

The clinicopathologic findings in 17 eyes which were surgically enucleated or removed at autopsy as well as the histopathology of 72 corneal buttons removed from eyes with intraocular lenses are described. In four of five autopsy eyes the intraocular lens was well tolerated; however, in all cases, changes related to the pseudophakos were found. In seven of 12 surgically enucleated eyes, postsurgical bacterial or fungal endophthalmitis had developed. On histopathological examination, one eye revealed clinically unsuspected endophthalmitis phacoanaphylactica after extracapsular cataract extraction and intraocular lens implantation. In two cases, choroidal melanoma became evident after cataract extraction and insertion of a pseudophakos. In both cases preoperative ultrasonography was limited to A-scan axial measurements. The 72 corneal buttons were removed from patients with pseudophakic bullous keratopathy; histologically the most striking findings were guttata-like changes in 50% of the specimens and retrocorneal membranes in 13.9% of the specimens.

Pseudophakic corneal edema: A review of mechanisms and treatments

PURPOSE

To review the pathological mechanisms and treatments for pseudophakic corneal edema (PCE), one of the most common indications for penetrating keratoplasty.

METHODS

The literature was examined for the molecular biology associated with PCE and for the surgical and medical treatments for this disorder.

RESULTS

The incidence of PCE has recently been decreasing because of improved surgical instrumentation, including improvements in intraocular lens designs that cause less trauma to the corneal endothelium. Extracellular matrix and growth factor abnormalities occur in PCE corneas and recently, the role of aquaporins, which are involved in the regulation of fluid movement across cells, has been investigated.

CONCLUSIONS

Although newer treatment options have been suggested, penetrating keratoplasty still remains the most definitive treatment and has the highest success rate.

Symptomatic management of postoperative bullous keratopathy with nonpreserved human amniotic membrane

PURPOSE

To report the results of the management of painfully symptomatic postoperative bullous keratopathy (PBK) by performing a nonpreserved human amniotic membrane (NP-AMT) transplantation in nine eyes with poor visual potential.

METHODS

A prospective, comparative, nonrandomized management of symptomatic PBK was done by performing a complete corneal de-epithelialization followed by a NP-AMT transplantation (NP-AMT group) or no NP-AMT transplantation (control group). We evaluated time for re-epithelialization, patient's symptoms, and appearance of new bullae.

RESULTS

In the NP-AMT group, mean follow-up time was 40 weeks. Mean re-epithelialization time was 11.2 days. Symptoms of PBK resolved completely in eight patients (88%), who were asymptomatic and showing very quiet eyes from postoperative day 1, and resolved partially in one patient in whom we observed barely symptomatic bullae at the peripheral NP-AMT border (sixth postoperative week) and an asymptomatic one at the corneal center under the NP-AMT (seventh postoperative week). In the control group, mean follow-up time was 18 weeks; there were recurrences of symptomatic bullae in four of five patients at a mean time of 6.3 days.

CONCLUSIONS

NP-AMT is a good alternative for the management of painful PBK in eyes with poor visual potential; NP-AMT is widely available, the technique is easy to perform, and it has good results from both the symptomatic and esthetic standpoint.

Changing indications for penetrating keratoplasty in Taiwan from 1987 to 1999

PURPOSE

To determine the leading indications for penetrating keratoplasty and to identify changing trends in these indications during the past 12 years.

METHODS

We retrospectively performed a chart review of the hospital records of all patients undergoing penetrating keratoplasty at the National Taiwan University Hospital during a 12-year period (1987-1999). When possible, the clinical indication was corroborated by the pathologic report.

RESULTS

A total of 770 corneal transplants were performed. The leading indications for penetrating keratoplasty. in order of decreasing frequency, were corneal scars (27.9%), regraft (21.0%), acute necrotizing and ulcerative keratitis (17.9%), pseudophakic or aphakic bullous keratopathy (17.6%), Fuchs' dystrophy (4.5%), and keratoconus (2.5%). A trend of increasing frequency of regraft and acute necrotizing and ulcerative keratitis, a decreasing frequency of corneal scar, and an initially decreasing then increasing frequency of pseudophakic and aphakic bullous keratopathy were found during the 12-year study period. Acute necrotizing and ulcerative keratitis was found to be the most frequent indication for regraft.

CONCLUSION

In this series, corneal scars, regraft, and acute necrotizing and ulcerative keratitis were the leading indications for penetrating keratoplasty. A changing incidence of pseudophakic and aphakic bullous keratopathy noted during the study period was related to the type of intraocular lens implanted and the method of cataract surgery performed. This study found a comparatively high frequency of acute necrotizing and ulcerative keratitis and an extremely low frequency of keratoconus compared with previous reports.

Intraocular lens complications requiring removal or exchange

Intraocular lens (IOL)-related complications are caused primarily by mechanical trauma, inflammatory or infectious complications, or optical problems. Complications may occur at the time of surgery or be the result of an ongoing postoperative process. Mechanical and inflammatory injury may produce corneal decompensation, cystoid macular edema, hyphema, uveitis, and glaucoma, causing reduced vision and in some cases chronic pain. Optical problems may be due to a wrong power of the IOL or to postoperative decentration or dislocation of the lens. Ophthalmologists should be aware of the indications for IOL removal or exchange in those patients who have ongoing IOL-induced injury or impairment. Removal or exchange of an IOL frequently involves a complex decision-making process and is often associated with immense technical challenge. Various medical and surgical treatments may be tried to correct IOL problems before the decision is made to remove or exchange the lens.

Ulcerative keratitis in bullous keratopathy

PURPOSE

The authors review a large series of patients with bullous keratopathy (BK) to analyze the frequency of ulcerative keratitis, and determine the contributory roles of bullae, bandage soft contact lenses, steroids, and prophylactic antibiotics.

METHODS

A retrospective review of all cases of pseudophakic or aphakic bullous keratopathy presenting to the cornea service between January 1, 1986 and September 1, 1995 was performed. The influence of time, bullae, bandage contact lenses, steroids, and prophylactic antibiotics was evaluated by actuarial methods and multivariate analysis.

RESULTS

Nine hundred eighteen patients were included in this study, 44 (4.7%) of whom had infectious or inflammatory complications; 813 cases were available for statistical analysis. Steroids (P < 0.0001), bandage soft contact lens use (P = 0.004), and bullae (P = 0.01) had statistically significant independent effect on the risk of developing ulcerative keratitis, and the combination of steroids and bandage lenses yielded the highest risk (P < 0.001). Propylactic antibiotic use paradoxically had a statistically significant association with ulcerative keratitis in these patients (P = 0.01). Increasing BK time was also associated with ulcer development, and the risk remained relatively constant over the 60 months of the study. Streptococcus was the most frequent organism cultured.

CONCLUSIONS

Ulcerative keratitis developed in 4.7% of patients with bullous keratopathy. Prolonged BK time alone was a risk factor for infection. The strongest single additional risk factor for ulcer development was steroid use, followed by bandage soft contact lens use, and their simultaneous use had the greatest effect. The presence of bullae was also a risk factor for infection, and prophylactic antibiotic use did not prevent ulcer development.

Intraocular complications associated with the Dubroff anterior chamber lens

We examined a series of 53 consecutive eyes form which Dubroff-style anterior chamber lenses were explanted. The mean time from implantation to explantation was 46.21 months (range six to 99 months). Problems leading to explantation included bullous keratopathy (83%), glaucoma (51%), chronic cystoid macular edema (40%), and iritis (13%). Molteno valves were required in 9% of eyes. Progressive anterior synechias resulted in intraocular lens displacement against the cornea in 19%. The Dubroff lenses caused problems similar to those previously observed with closed-loop anterior chamber lenses but had a higher incidence of severe glaucoma and progressive peripheral anterior synechias.

The effects of denatured sodium hyaluronate on the corneal endothelium in cats

In an in vivo cat model, wide-field specular microscopy and scanning electron microscopy were used to observe whether heat-denatured sodium hyaluronate causes cell damage to the corneal endothelium. The endothelial cell toxicities of various drugs, including 0.01% benzalkonium chloride, 0.2% chlorhexidine digluconate, and 0.5% lidocaine, mixed with intact or untreated sodium hyaluronate were also investigated. Neither heat-denatured nor intact or untreated sodium hyaluronate alone had any adverse effect on the corneal endothelium in cats, whereas 0.01% benzalkonium chloride and 0.2% chlorhexidine digluconate, mixed with sodium hyaluronate, caused substantial endothelial morphologic changes, which resulted in corneal edema. By comparison, 0.5% lidocaine with sodium hyaluronate was found to have minimal effect on the corneal endothelium in cats. These findings indicate that some chemical contaminant with sodium hyaluronate, not heat-denatured sodium hyaluronate, induces an immediate onset of pseudophakic bullous keratopathy.

Experimental evaluation of a phakic anterior chamber implant in a primate model. Part II. Pathology

Anterior chamber intraocular lenses were implanted in 50 phakic primate eyes and followed by serial histopathology for two years. Significant observations included corneal endothelial alterations, haptic erosion into and encapsulation by peripheral iris and ciliary body, and chronic low grade inflammation.

Experimental evaluation of a phakic anterior chamber implant in a primate model. Part I. Clinical observations

Anterior chamber intraocular lenses were implanted in phakic cynomolgus monkey eyes and followed clinically over two years. Significant observations included erosion and/or uveal envelopment of the haptic and a decrease in endothelial cell counts. There was good positional stability, no significant inflammation, initial ocular hypotension that returned to normal intraocular pressure, and no evidence of cataracts or cystoid macular edema.

Implantation of scleral-fixated posterior chamber intraocular lenses

A surgical technique for implanting a posterior chamber intraocular lens (IOL) in eyes without capsular or zonular support is presented. A 10-0 polypropylene suture attached to a standard needle is tied to the apex of each haptic and passed transclerally through the ciliary sulcus to secure the haptics at the 3 o'clock and 9 o'clock meridians. This technique produced good visual results in six aphakic patients who were contact lens intolerant, two patients in whom capsular or zonular rupture at the time of cataract surgery precluded standard nonsuture fixation techniques, one patient who had intracapsular cataract extraction for a subluxated, cataractous lens, and one patient who had secondary IOL implantation in combination with penetrating keratoplasty for aphakic bullous keratopathy. Advantages over other techniques of posterior chamber lens implantation in the absence of capsular support include technical ease, avoidance of iris fixation, and more precise placement of scleral fixation sutures, thus minimizing IOL decentration.

Indications for and outcomes of repeat penetrating keratoplasty

We reviewed data on 150 repeat corneal transplants performed between 1983 and 1988 at Wills Eye Hospital. Minimal postoperative follow-up was six months. The most common diagnoses before regraft were pseudophakic bullous keratopathy (29 of 150), aphakic bullous keratopathy (28 of 150), Fuchs' dystrophy (21 of 150), failed graft (17 of 150), and keratoconus (14 of 150). Herpes simplex keratitis, interstitial keratitis, chemical burns, traumatic scars, and corneal dystrophies accounted for most of the remaining regrafts. Of the 150 regrafts, 39 (26%) failed during the study period. Almost half of the regraft failures occurred within six months, and over four fifths occurred within 18 months. Of the 111 eyes with clear grafts, final visual acuity data were available for 68 eyes (minimal follow-up, two years; mean, 3.3 years). A best-corrected visual acuity of 20/20 to 20/40 (22 of 68) or 20/50 to 20/100 (27 of 68) was achieved in most patients.

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.

Complications of sulcus-supported intraocular lenses with iris sutures, implanted during penetrating keratoplasty after intracapsular cataract extraction

In a retrospective study, the authors analyzed visual results and postoperative complications in a series of 14 consecutive patients who had undergone penetrating keratoplasty and implantation of a posterior chamber intraocular lens (PC IOL) in the absence of the posterior capsule. Seven patients suffered from aphakic bullous keratopathy and seven from pseudophakic bullous keratopathy. Postoperative follow-up was 7.6 months on the average. Best-corrected postoperative visual acuity was 20/60 or better in four cases and 20/200 or better in eight. Glaucoma was present before surgery in four eyes, which persisted in all cases and developed in four new cases. Results of gonioscopic examination showed the postoperative development of goniosynechiae in four eyes. Pseudophakodonesis of various extent was present in ten eyes. Preoperatively, cystoid macular edema was diagnosed angiographically in one case. It did not improve after surgery and was seen in three additional eyes postoperatively. Causes for postoperative visual acuity lower than 20/200 were cystoid macular edema in three cases, graft rejection in one case, central retinal scar in one case, and optic nerve atrophy in one case. A distortion of the pupil was seen in three eyes in miosis and in four additional eyes in mydriasis. Corneal thickness as well as anterior chamber depth were within normal limits. Fluorophotometric evaluation of the blood-aqueous barrier showed values comparable with those obtained after intracapsular cataract extraction and implantation of an iris-fixated IOL. Despite the relatively good visual results, the high postoperative incidence of cystoid macular edema and/or glaucoma may discourage the use of this technique.

Graft failure after penetrating keratoplasty

Despite the improving results that have been noted with penetrating keratoplasty, graft failure remains a significant problem. The causes of graft failure are quite varied. Primary donor failure, surgical complications, intraocular lens complications, persistent epithelial defects, allograft rejection, infection, glaucoma, trauma, and recurrences of primary corneal dystrophies are common etiologies. In this article, a critical review of the available literature concerned with the factors influencing the many causes of graft failure and their management is provided.

Natural history of cystoid macular edema in pseudophakic bullous keratopathy

A retrospective review of 25 consecutive patients having penetrating keratoplasty (PKP) with the preoperative diagnoses of pseudophakic bullous keratopathy (PBK) and cystoid macular edema (CME) was undertaken to analyze the natural history of preoperative CME following keratoplasty. Follow-up ranged from 13 to 54 months with a mean of 27 months. All patients had intraocular lens exchanges with 24 receiving posterior chamber lenses; 23 had lenses sutured to the posterior iris. Sixteen patients (64%) recovered a visual acuity of 20/40 or better. The average time for visual recovery to 20/40 was nine months with a range of two to 45 months. Eighteen (72%) had resolution of angiographic CME. Three patients previously diagnosed as having chronic CME recovered visual acuity of 20/40 or better. Cases of PBK with CME may have an excellent visual prognosis if the IOL is managed properly at the time of PKP.

Results of penetrating keratoplasty for pseudophakic bullous keratopathy with the exchange of an intraocular lens

We report on 29 consecutive patients with pseudophakic bullous keratopathy who underwent in one eye penetrating keratoplasty with an exchange of the original intraocular lens for a Pearce tripod posterior chamber lens, and who were available for a follow up of at least 12 months. The average interval between cataract extraction with lens implantation and the appearance of bullous keratopathy was five and a half years (range 10 months to 16 years). The mean follow-up period after penetrating keratoplasty was 36 months (range 12 to 56 months). The corneal graft remained clear in 22 (76%) eyes. One year after the operation 45% of the eyes had a vision of 20/40 or better, and 20% had visual acuities between 20/40 and 20/100. The remaining 31% had a vision of 20/100 or less (one unknown). Nine eyes (31%) had cystoid macular oedema or macular degeneration. 45% of the eyes had a refraction within approximately 2 dioptres of emmetropia. In patients with pseudophakic corneal oedema we continue to exchange the intraocular lens by a Pearce tripod posterior chamber lens sutured to the iris when it is necessary to remove the lens.

Visual results of suture-fixated posterior chamber lenses during penetrating keratoplasty

Between August 12, 1982, and June 30, 1987, 233 consecutive eyes had posterior chamber intraocular lenses (PC IOLs) suture-fixated to the posterior aspect of the iris during penetrating keratoplasty (PKP). In all cases, insufficient capsular material was present to provide adequate fixation for the implant. Lenses were placed in 72 aphakic eyes as a secondary implant, and 159 lenses were placed after removal of another implant. Follow-up ranged from 1 year to 68 months with 59.5% of patients achieving visual acuity of 20/40 or better, and 74% of 20/80 or better. Suture-fixating a PC IOL to the iris offers multiple advantages over placement of an anterior chamber lens during PKP. The complication rate appears low, and long-term problems with glaucoma and recurrent corneal decompensation should be reduced.

Retention of iris supported intraocular lenses at the time of penetrating keratoplasty for pseudophakic corneal oedema

The long-term follow-up of patients undergoing penetrating keratoplasty for pseudophakic corneal oedema is reported. The cause and frequency of corneal decompensation following intracapsular cataract extraction with insertion of an iris supported lens was assessed and found to be unrelated to the implant in the majority of cases. The most common cause of decompensation was endothelial touch during the cataract extraction. In all eyes the intraocular lens was retained at the time of penetrating keratoplasty. The hazards of removal of the lens are discussed and the recommendations made that lenses be retained when penetrating keratoplasty is undertaken for pseudophakic corneal oedema, other than in exceptional cases.

Penetrating keratoplasty for pseudophakic bullous keratopathy. Management of the intraocular lens

Management of the intraocular lens (IOL) at the time of penetrating keratoplasty (PK) for pseudophakic bullous keratopathy has been based on lens-related factors and coexisting anterior segment abnormalities. The authors reviewed the results of PK for 102 cases of pseudophakic bullous keratopathy (43 anterior chamber, 50 iris-supported, and 9 posterior chamber) with respect to: (1) the type of IOL, (2) coexisting abnormalities, and (3) management of the IOL at surgery. Graft failure after 2 years of follow-up was: (1) retained iris-supported IOLs, 9%; (2) retained anterior chamber IOLs, 60%; (3) retained posterior chamber intraocular lenses (PC IOL), 0%; (4) removed IOLs, 9%; and (5) exchanged IOLs, 20%. After 5 years of follow-up, 13 of 13 PKs with retained closed-loop anterior chamber IOLs had failed. Visual results were best in eyes with retained iris-supported, rigid anterior chamber or PC IOLs and when the IOL was removed without replacement. The authors recommend that closed-loop anterior chamber lenses and unstable lenses of any type be removed or exchanged and that well-fixated PC IOLs and iris-clip IOLs be retained at the time of PK for pseudophakic bullous keratopathy.

Visual results after keratoplasty in patients with posterior chamber intraocular lenses

We performed penetrating keratoplasty in 20 consecutive patients who had posterior chamber intraocular lenses and who developed pseudophakic bullous keratopathy. All patients received 8.0-mm grafts placed in 7.5-mm recipient beds. None of the intraocular lenses were removed. Final visual acuity was 20/40 or better in eight (40%) and 20/80 or better in 15 (75%) of the patients. Senile macular degeneration (one case), corneal graft rejection (two cases), and wound infection (one case) contributed to poor visual results in the remaining patients.

Results of anterior segment reconstruction for aphakic and pseudophakic corneal edema

The authors studied prospectively 59 eyes with corneal edema after cataract surgery that required reconstructive surgery; penetrating keratoplasty in 59 (100%), anterior vitrectomy in 42 (71%), intraocular lens removal or exchange in 33 (56%), gonioplasty in 32 (54%), and iridoplasty in 30 (51%). With an average follow-up of 9.9 months, the corneal transplant was clear in 56 eyes (95%). The corrected visual acuity was improved in 49 eyes (83%) and was the same in seven eyes (12%). Intraocular pressure was less than or equal to 21 mmHg in 47 eyes (80%) and 22 to 29 mmHg in nine eyes (15%). The peripheral anterior synechiae score was the same or improved in 56 eyes (95%). Cystoid macular edema was absent to mild in 52 eyes (88%). Anterior segment reconstruction improved both anatomic integrity and visual acuity of most eyes without increasing complications.

Bullous keratopathy: a study of endothelial cell morphology in patients undergoing cataract surgery

Preoperative and postoperative endothelial cell morphology was examined in three types of patients participating in a randomised, controlled trial of cataract surgery. The first sustained modest endothelial cell loss and served as controls, the second and third sustained high cell loss, but only the latter progressed to bullous keratopathy. The technique of examining endothelial cell morphology is described and its validity assessed. Measures of cell area, number of sides, side length, and variation in cell size and cell shape were utilised. No significant differences were found between the three groups by any of the preoperative morphological measures. Furthermore, postoperative values of variation in cell shape and cell size did not differ significantly between the groups. No evidence was found in our patients to support the hypothesis that eyes at particular risk of developing bullous keratopathy may be differentiated on the basis of their preoperative or early postoperative endothelial cell morphology.

Penetrating keratoplasty for pseudophakic bullous keratopathy after extracapsular cataract extraction

Seventeen women underwent simple penetrating keratoplasty for pseudophakic bullous keratopathy after extracapsular cataract extraction. Corneal edema occurred an average of eight months after cataract surgery (range, zero to 32 months). Of 17 corneal grafts, 16 (94%) have remained clear during an average follow-up period of 14 months (range, two to 32 months). One eye had a nonimmunologic graft failure. Of 16 eyes with clear grafts, 14 (87%) achieved a visual acuity of 20/40 or better after surgery. Two eyes with a visual acuity of 20/50 and 20/200 had opacified posterior capsules and one demonstrated age-related macular degeneration. One eye with a postoperative visual acuity of 20/40 demonstrated cystoid macular edema. Fifteen of 17 contralateral eyes showed slit-lamp evidence of endothelial dystrophy.

Indications for penetrating keratoplasty: a clinicopathological review of 511 corneal specimens

During the four-and-a-half year period from January 1982 to June 1986, 511 penetrating keratoplasty specimens were submitted to the Pathology Department of The Royal Victorian Eye and Ear Hospital. Seventy per cent were from patients of the RVEEH and the remainder were submitted from outside the Hospital. The cases were classified both clinically and pathologically. The most frequent diagnosis was keratoconus, followed by scarring, regrafts, bullous keratopathy, acute or chronic ulceration, corneal dystrophies and a small miscellaneous group. Post-herpetic scarring was the most common cause of scarring. Bullous keratopathy was usually aphakic in origin in 1982, but after 1983 pseudophakic bullous keratopathy (PBK) was the most common cause of bullous keratopathy. Acute ulceration was usually bacterial in origin, not infrequently with hypopyon.