Corneal thickness changes after high-risk penetrating keratoplasty. Collaborative Corneal Transplantation Study Group

OBJECTIVE

To determine whether ultrasonic measurements of corneal thickness are of prognostic value after high-risk penetrating keratoplasty.

DESIGN

A prospective, multicenter, randomized trial.

PATIENTS

Four hundred fifty patients at high risk for graft failure because of previous immunologic graft failure or because of two or more quadrants of stromal vascularization. Patients underwent surgery and were treated according to a specific protocol and observed at frequent intervals.

INTERVENTION

At each postoperative visit, ultrasonic measurement of central corneal thickness was performed and the corneal status was determined by biomicroscopic examination.

MAIN OUTCOME MEASURE

Graft failure owing to immunologic or nonimmunologic causes.

RESULTS

Corneal thickness stabilized by 3 months at a median thickness of 0.54 mm. The range of corneal thicknesses in patients with corneal grafts judged to be clear was large. In 49% of eyes, development of an allograft reaction episode was accompanied by an increase in corneal thickness of at least 10%; the greater the increase in thickness, the more likely the graft would fail. Clear grafts with central thicknesses of 0.59 mm or greater at 1, 3, or 6 months had a much greater risk of failure than those with thicknesses of less than 0.59 mm.

CONCLUSION

Corneal thickness measurements after high-risk penetrating keratoplasty are of prognostic value.

Surgical management of subluxed posterior-chamber intraocular lenses

OBJECTIVE

To formulate a systematic approach to the surgical management of subluxed posterior-chamber intraocular lenses (IOLs).

DESIGN

We reviewed the records of 31 consecutive patients who underwent anterior-segment surgery for IOL subluxation. Presumed anatomic causes of IOL subluxation were identified in 28 cases (90%). Three surgical procedures were used to correct the implant subluxation: modified McCannel sutures (19 eyes), IOL exchange (eight eyes), or IOL rotation (four eyes).

RESULTS

Twenty-nine (94%) of the 31 patients obtained a postoperative visual acuity of 20/40 or better. Surgical complications included persistent vitreous in the anterior chamber (three cases), progressive capsular opacification (two cases), and anterior chamber and vitreous hemorrhage (one case).

CONCLUSIONS

Our results show that, by implementing a planned surgical approach, subluxed posterior-chamber IOLs can be safely and effectively managed.

High-frequency ultrasound quantitative analyses of corneal scarring following excimer laser keratectomy

OBJECTIVE

To report objective grading and analysis of excimer laser-induced scarring using high-frequency ultrasound.

METHODS

High-frequency ultrasound (50 MHz) corneal examination was performed on eight New Zealand white rabbits at different time points (10, 17, 24, and 74 days following phototherapeutic keratectomy). We used biometry and signal-processing techniques to determine corneal, epithelial, and scar thicknesses and to quantify the acoustic backscatter.

RESULTS

Excimer laser-induced scarring showed an irregularly distributed acoustic hyperreflectivity that decreased through day 74. Corneal thickness remained reduced after ablation (mean, 318 microns compared with 419 microns for controls). Epithelial thickness averaged 62 microns and scar thickness, 87 microns. Scar peak and average anterior stroma acoustic backscatter ratios decreased from day 10 to day 74 (19.65 to 2.76, and 6.42 to 1.32, respectively). Histopathologic study showed increased keratocyte activity at early time points that correlated with acoustic backscatter ratios and imaging pattern.

CONCLUSIONS

High-frequency ultrasound signal processing is a noninvasive method that quantitatively grades excimer laser-induced corneal scarring.

Visual function after surgery for early cataract

Glare disability and contrast sensitivity loss can be present in cataract patients with minimally reduced visual acuity. Objective and subjective visual function was analyzed in 72 patients (mean visual acuity = 20/40) before and after cataract surgery. Following surgery, most subjects regained normal function in all tests. Improvement in contrast sensitivity and reduction of glare disability were independent of preoperative visual acuity. Subjective improvement in visual function was predicted by acuity and contrast sensitivity tests.

Oil-drop cataracts

The oil-drop cataract is a common yet often overlooked cause of progressive vision loss. Although the nuclear change can be subtle on slitlamp biomicroscopic examination, retinoscopy reveals the classic oil droplet silhouetted against the red reflex. We present seven patients with oil-drop cataracts referred for neuro-ophthalmologic evaluation because of unexplained vision loss. All had been evaluated by multiple physicians and had had extensive diagnostic testing. The patients were between 36 and 69 years old with visual acuities from 20/20 to 20/400. The neuro-ophthalmologic evaluation in all patients was normal except for lenticular nuclear changes, best appreciated with retinoscopy.

Clinical experience with N-butyl cyanoacrylate (Nexacryl) tissue adhesive

BACKGROUND

To investigate the indications, outcomes, and complications of N-butyl cyanoacrylate tissue adhesive for ocular clinical use. This tissue adhesive is under investigation by the Food and Drug Administration.

METHODS

N-butyl cyanoacrylate was used as an investigational device on 44 patients at the authors' institution over a 2-year period. The charts of these patients were reviewed.

RESULTS

The indications for glue application included corneal perforation (19 eyes), descemetoceles (9 eyes), leaking filtering blebs (6 eyes), stromal thinning (5 eyes), wound leaks (4 eyes), and exposure keratopathy (1 eye). A bandage contact lens was used over the dried tissue adhesive in 38 of the 44 eyes. Length of glue adherence ranged from 1 to 660 days (mean, 72 days). Outcome was penetrating keratoplasty (19 eyes), no further intervention (14 eyes), enucleation (4 eyes), surgical revision of a filter (2 eyes), scleral patch graft (1 eye), conjunctival transplant (1 eye), failed tarsorrhaphy (1 eye), suturing of wound (1 eye), and a lamellar graft (1 eye). Vision improved in 52% (23/44) of eyes.

CONCLUSION

This tissue adhesive may soon be available to all ophthalmologists, and the authors' experience demonstrates that it is an effective method of temporary or permanent closure of an impending or frank perforation.

Comparison of acuity, contrast sensitivity, and disability glare before and after cataract surgery

We assessed vision before and after uncomplicated extracapsular cataract extraction and intraocular lens implantation in 72 symptomatic patients with acuity equal to or better than 20/80 and no other ocular abnormality. Contrast sensitivity was measured with the Pelli-Robson Letter Chart (Metropia Ltd, Cambridge, England) and disability glare was measured under daytime conditions with the Brightness Acuity Tester (Mentor O&O Inc, Norwell, Mass) and under nighttime conditions with a computer-controlled video display. Prior to surgery there was significant disability glare that was not correlated with acuity. There was also a loss in contrast sensitivity that was moderately correlated with acuity (r = -.43; P < .001). Following surgery, most patients' scores returned to normal on all tests. Improvement in disability glare and contrast sensitivity was independent of improvement in acuity. Furthermore, patients with the poorest preoperative vision were as likely to regain normal function after surgery as those with the best preoperative vision.

Combined trabeculectomy, cataract extraction, and foldable lens implantation

The efficacy of foldable silicone intraocular lenses in combined glaucoma/cataract surgery was retrospectively analyzed in 19 consecutive operations. Preoperatively all patients were receiving medical treatment for glaucoma; 21% had intraocular pressures above 21 mm Hg despite the medical therapy. Postoperatively, reduction of intraocular pressure to 21 mm Hg or less was achieved in 84% of eyes, with 58% requiring no antiglaucoma medications. Mean improvement of Snellen visual acuity was 4.9 lines; 84% of eyes achieved a final acuity of 20/40 or better. Median follow-up was 59 weeks (range 25 to 88 weeks). Thirteen eyes (68%) had a filtration bleb present when last examined. These preliminary results suggest that foldable silicone IOLs are an effective alternative to poly(methyl methacrylate) lenses in combined glaucoma/cataract surgery.

The effect of early cataracts on glare and contrast sensitivity. A pilot study

To establish the effect of cataracts on glare and contrast sensitivity, we graded type and amount of lens opacity in 110 subjects who underwent two glare tests (Brightness Acuity Tester and Berkeley glare test) and two contrast sensitivity tests (a sine-wave test and Pelli-Robson chart). Twenty-seven subjects (25%) had clear lenses (mean visual acuity of 20/20) and 83 subjects (75%) had early lens opacities (mean visual acuity of 20/40) in otherwise normal eyes. Multiple regression techniques were used to control for the effects of age and visual acuity. Glare test scores were significantly lower for nearly all patients with lens opacities than for patients with clear lenses and were the lowest for patients with lenses with posterior subcapsular opacity. Contrast sensitivity scores were lower for all patients with lens opacities than for patients with clear lenses at high frequencies only; all lens opacity groups scores similarly with each other. These results indicate reduced visual function among patients with cataracts whose visual acuity is only minimally impaired.

Rotation of posterior chamber intraocular lenses for management of lens-associated recurring hyphemas

Management of recurring hyphemas associated with posterior chamber intraocular lenses may include a combination of medical, laser, and surgical modalities. Miotic and laser therapies have often failed, and surgical treatment has primarily relied on removal of the offending lens. We describe herein a method for rotation of the intraocular lens that provides an effective means of preventing one form of recurrent intraocular hemorrhage.

Clinical follow-up of 193-nm ArF excimer laser photokeratectomy

The excimer laser has been undergoing rapid development for clinical use since the early 1980s. The authors report 2-year follow-up results from studies in 31 eyes (15 women and 14 men) to evaluate the excimer laser in performing photokeratectomy. Patients were divided into two groups: 27 eyes (group 1) underwent phototherapeutic keratectomy, and 4 eyes (group 2) underwent photorefractive keratectomy. Visual function improved in 21 of 27 eyes in group 1 and in 2 of 4 eyes in group 2. Complications were minimal and manageable. The authors describe a procedure to minimize induced hyperopia in phototherapeutic keratectomy patients, and, although not statistically significant, less induced hyperopia was noted in these patients. Photokeratectomy may be an alternative to penetrating or lamellar keratoplasty and more invasive refractive procedures, but the long-term effects must be carefully observed.

Mooren's ulcer and evidence of stromal graft rejection after penetrating keratoplasty

A Mooren's ulcer developed in a 6-year-old girl after a penetrating keratoplasty for Peters' anomaly. A destructive, circumferential, and centripetal stromal ulceration recurred despite conjunctival resection, corneal gluing, topical and systemic administration of corticosteroids, and repeat graftings. Results of a systemic and a rheumatologic examination were unremarkable. Histopathologic evaluations of donor grafts consistently disclosed a lymphocytic and a plasma cell infiltrate. Indirect immunofluorescent staining using a normal donor cornea substrate was positive at the level of Bowman's membrane and stroma. The patient's lymphocytes were stimulated by a partially purified bovine corneal antigen and a positive antibody titer was found in the patient's sera to the same corneal antigen. These results suggest humoral and cell-mediated immune mechanisms can be involved in the initiation and perpetuation of a stromal rejection process after penetrating keratoplasty.

Worldwide legal requirements for obtaining corneas: 1990

Cornea transplantation offers the hope of restoring useful vision to millions of individuals worldwide. Yet it is widely used only in certain countries. While a lack of the necessary economic and technical infrastructure is the primary reason in many countries, the legal and social systems pose a similar obstacle in many other more prosperous countries. This article reviews the current laws governing organ and tissue donation throughout the world and distinguishes those that are most successful in obtaining tissue for transplantation.

Visual correction following penetrating keratoplasty

Postoperative visual correction following penetrating keratoplasty usually includes spectacles, but for some patients optimal vision may be obtained using contact lenses. We studied 126 eyes of 101 patients undergoing penetrating keratoplasty to determine the frequency of postoperative contact-lens use, its clinical associations, its effect on the risk of corneal graft rejection, and its potential effects on topical medications. A total of 20 patients (16%) wore contact lenses postoperatively for maximal optical correction. Among eyes with good macular potential, 17 of 63 (27%) wore contact lenses. Contact-lens wear did not preclude the use of chronic postoperative topical medications, nor did it increase the risk of corneal graft rejection. We conclude that contact lenses may be useful for optimizing vision after penetrating keratoplasty, especially when macular potential is good.

Corneal wound healing after 193-nm excimer laser keratectomy

As part of a human trial of phototherapeutic keratectomy, we performed anterior keratectomy using excimer laser 193-nm ablation on patients with superficial corneal opacities. We examined the ultrastructural changes in the corneas of four patients who underwent penetrating keratoplasty 6 to 15 months after excimer laser ablation. The four cases included macular dystrophy, recurrent keratoconus in a graft, and corneal scarring (two eyes). Light microscopy showed epithelial thickening, absence of Bowman's layer, and superficial stromal scarring in the area of ablation. Ultrastructural study showed that the epithelial basement membrane had focal discontinuities. At the margin of the ablation superficial collagen bundles terminated abruptly in a steplike configuration. The anterior stroma was scarred, with loss of lamellar structure and an increase in number of fibrocytes. The laser-induced scar was 10 to 15 microns thick in the two eyes without a stromal scar before laser ablation. The stroma underlying the scarred areas and that in the untreated area appeared normal. Linear collagen-like fibers were present in the posterior aspect of Descemet's membrane. Laser-induced scarring may be an important factor in limiting visual improvement in patients undergoing phototherapeutic keratectomy.

Subregions of differing refractive power within the clear zone after experimental radial keratotomy

After radial keratotomy (RK), some patients experience a mild decrease in best corrected visual acuity, visual distortion, or monocular diplopia. These optical effects of radial keratotomy are best explained by subregions of different refractive powers within the surgery-free clear zone. To investigate the topography of the clear zone, we performed four- and eight-incision radial keratotomy in eight cadaver eyes. After radial keratotomy, we found subregions within the clear zone of two types: 1) small, very flat regions at the ends of the radial incisions (seven of eight eyes), and 2) a series of concentric rings centered on the visual axis with a continuously progressive decline in refractive power toward the periphery of the clear zone (all eyes). The clear zone after radial keratotomy is often nipple-shaped, with a more myopic segment centrally and a more hyperopic region near the periphery of the clear zone.

Modulation of corneal wound healing after excimer laser keratomileusis using topical mitomycin C and steroids

A 193-nm excimer laser system was used to create deep stromal ablations in seven New Zealand white rabbits and shallow ablations in three. Eyes were randomized for treatment with topical mitomycin C, steroids, and erythromycin; topical steroids and erythromycin; or topical erythromycin only. All treatment regimens were instituted twice daily for 14 days. All eyes reepithelialized normally within 3 to 5 days. During 10 weeks of follow-up, all eyes developed moderate reticular subepithelial haze without significant differences among treatment groups. Results of light, fluorescence, and electron microscopic examination showed anterior stromal scarring and markedly reduced new subepithelial collagen formation in the group treated with mitomycin C, corticosteroids, and erythromycin. Focal abnormalities of Descemet's membrane and endothelial abnormalities were present in all treatment groups. Combination therapy with topical steroids, mitomycin C, and erythromycin to control the corneal wound healing response after refractive laser surgery appears promising and warrants further study.

Natural history of corneal astigmatism after cataract surgery

Little information on the natural course of corneal astigmatism following cataract surgery exists. We report a prospective, computerized analysis of postoperative astigmatism, based on keratometry measurements, of 137 cases of extracapsular cataract extraction with intraocular lens implantation performed by one surgeon. No sutures were cut postoperatively. Surgery induced 1.44 diopters (D) of with-the-rule astigmatism at one month, which declined at a rate of 0.77 D and 0.35 D per month for the next two months, respectively, with a more gradual decline thereafter. The mean surgically induced astigmatism at the last postoperative visit ranged from 0.29 D at six months (minimum follow-up) to 1.23 D at 48 months; both were against-the-rule. Mean follow-up was 28.92 months. These findings may be technique specific and suggest that (1) corneal curvature continues to change slowly even two to four years postoperatively; (2) most patients develop against-the-rule astigmatism, thus more with-the-rule astigmatism is desirable in the early postoperative period; (3) selective suture removal is necessary only when significantly more than 3.00 D of surgically induced with-the-rule astigmatism is present.