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As we strive to make science education more inclusive, more research is needed to fully understand gender gaps in academic performance and in-class participation in the life sciences. Studies suggest that male voices dominate introductory biology courses, but no studies have been done on upper-level courses. Results on achievement gender gaps in biology vary and often conflict, and no studies have been done on the correlation between participation and academic performance gaps. We observed 34 life sciences courses at all levels at a large private university. Overall, males were more likely to participate than their female peers, but these gender gaps varied from class to class. Females participated more in classes in which the instructor called on most hands that were raised or in classes with more females in attendance. Performance gender gaps also varied by classroom, but female final course grades were as much as 0.2 SD higher in classes with a female instructor and/or a female student majority. Gender gaps in participation and final course grades were positively correlated, but this could be solely because female students are more likely to both participate more and earn higher grades in classes with many females in attendance.

Providing students with one-on-one interaction with instructors is a big challenge in large courses. One solution is to have students interact with their peers during class. Reciprocal peer tutoring (RPT) is a more involved interaction that requires peers to alternate the roles of "teacher" and "student." Theoretically, advantages for peer tutoring include the verbalization and questioning of information and the scaffolded exploration of material through social and cognitive interaction. Studies on RPT vary in their execution, but most require elaborate planning and take up valuable class time. We tested the effectiveness of a "teach and question" (TQ) assignment that required student pairs to engage in RPT regularly outside class. A quasi-experimental design was implemented: one section of a general biology course completed TQ assignments, while another section completed a substitute assignment requiring individuals to review course material. The TQ section outperformed the other section by ∼6% on exams. Session recordings were coded to investigate correlation between TQ quality and student performance. Asking more questions was the characteristic that best predicted exam performance, and this was more predictive than most aspects of the course. We propose the TQ as an easy assignment to implement with large performance gains.

Purpose: To analyze the results of intraocular pressure (IOP) reduction by diode laser contact cyclophotocoagulation ("cyclodiode") in cases of advanced glaucoma refractory to alternative treatments., Methods: Two hundred and ten eyes of 195 patients, ages 1 to 89 years (mean, 51 years) were followed for 3 to 30 months (mean, 10 months) after cyclodiode treatment., Results: More than one treatment was given in 102 eyes (49%), and the overall mean number of treatments given per eye was 1.75 (range, 2-5). Mean pretreatment IOP was 34.1 mmHg (+/-10.6 mmHg). At last follow-up, mean IOP was 20.1 mmHg (+/-9.3 mmHg), and mean total medications was reduced from 2.3 to 1.7. Mean final IOP was lowest in patients with silicone oil glaucoma (17.3 mmHg), and the mean reduction in IOP was greatest in patients with neovascular glaucoma (23.9 mmHg). At last follow-up, visual acuity was worse than before treatment in 29% of eyes, unchanged in 60%, and better in 11%. Overall success rate (IOP < 22 mmHg) was 66% at a mean follow-up of 10 months. Phthisis occurred in one eye (0.5%), and chronic hypotony (0 mmHg < IOP < 5 mmHg for > 3 months) in a further two eyes (1%). Corneal graft decompensation followed treatment in two eyes, macular pucker occurred in one eye, and combined hyphema/vitreous hemorrhage in one patient., Conclusions: Diode laser cycloablation is relatively safe and effective at controlling IOP in eyes with advanced refractory glaucoma in the short and medium term. With the treatment parameters used, multiple applications may be needed.

Background: Granular corneal dystrophy is a rare indication for corneal transplantation. Both penetrating and lamellar keratoplasty have been recommended, but because granular corneal dystrophy is known to recur within the donor material and multiple grafts may be necessary, the best surgical option has not been clearly established. The cellular cause of the dystrophy is unknown and the authors hypothesized that the rate and pattern of recurrence within lamellar and penetrating grafts might give clues to its etiology., Methods: The authors compared the visual outcome, rate, and pattern of recurrence after 20 penetrating keratoplasties and 11 lamellar keratoplasties for granular corneal dystrophy., Results: Penetrating keratoplasty and lamellar keratoplasty have a good visual outcome in granular corneal dystrophy. Visual acuities after both procedures were not statistically different. Recurrence of the dystrophy within the graft material was almost universal within 4 years. It first appeared centrally and superficially, occasionally adopting a vortex pattern suggesting epithelial involvement. The recurrence-free interval was independent of size and type of graft performed., Conclusion: The authors recommend lamellar keratoplasty as a primary procedure in managing visually disabling granular corneal dystrophy if the deposits are limited to the superficial cornea. This is particularly applicable in younger patients in whom multiple procedures may be necessary over a lifetime due to recurrence of the dystrophy, and the lower morbidity rate associated with lamellar keratoplasty becomes appreciable. Although granular corneal dystrophy generally is classified as a stromal dystrophy, the pattern of recurrence is more consistent with an epithelial or tear-borne abnormality than a disease of the stromal keratocyte.

The use of subconjunctival 5-fluorouracil (5-FU) in the first weeks after filtration surgery may ensure long-term bleb survival despite a continuing proliferative stimulus such as in eyes with neovascular glaucoma. In addition, long-term side effects may occur, such as increasing bleb thinning. To ascertain the long-term effects of 5-FU and sodium butyrate, an agent with differentiating and antiproliferative properties, we exposed proliferating human Tenon's capsule fibroblasts to different concentrations of the drugs. The cells were exposed to 5-FU for 1-12 d. The cells were subsequently observed for up to 30 d. Cell proliferation was assessed using cell counting and bromodeoxyuridine uptake, and cell viability was assessed with trypan blue uptake. 5-FU and sodium butyrate inhibited fibroblast proliferation during the treatment period. Higher concentrations of 5-FU (100 and 1000 micrograms/ml) for as little as 1 d resulted in no significant increase in the number of fibroblasts for at least 29 d after treatment was stopped, despite continued stimulation with serum. When treatment with sodium butyrate was stopped, there was greater recovery of proliferation. At a constant concentration of 1000 micrograms/ml of 5-FU for 3 or more days, or a concentration of 100 mmol/l sodium butyrate for 12 d, the entire fibroblast population gradually died over the 30 d period. Thus, short-term treatment with 5-FU may result in long-term inhibition of proliferation of fibroblasts. Long-term inhibition depends on the duration of treatment or on the concentration of 5-FU. Short-term treatment may be affecting the ability of the tissues at the bleb site to heal in the long term. Different dosage regimens may have advantages and are discussed.

The results of penetrating keratoplasty following trabeculectomy in 26 eyes where there was coexistent corneal disease and glaucoma are presented. Patients were aged 16-80 years at the time of drainage surgery (mean = 51 years) and there was a mean of 33.5 months between trabeculectomy and keratoplasty. The mean pressure fell from 35.3 mm Hg prior to trabeculectomy to 14.9 mm Hg at the time of keratoplasty and 20 mm Hg 12 months after keratoplasty. There was a 0.45 probability of maintaining normal intraocular pressure with medication at 5 years after keratoplasty; and a similar graft survival probability. The probability of maintaining both a clear graft and a normal pressure was only 0.27 at 5 years. In another 22 eyes combined trabeculectomy and penetrating keratoplasty was performed. Patients' ages ranged from 21-82 years (mean 55) at surgery, and 73% were aphakic. The intraocular pressure dropped from a mean of 28.9 mm Hg preoperatively to 14 mm Hg at 12 months. There was a 5 year probability of 0.7 of maintaining a clear graft but if both a clear graft and normal intraocular pressure are considered then the probability falls to 0.5 at 5 years. The hazard ratio for intraocular pressure control and graft survival between the two groups suggests that combined surgery may offer a better prognosis.

Three hundred and thirty-five eyes of 210 patients with congenital glaucoma due to trabecular dysgenesis were treated by goniotomy as the primary procedure in infancy. In 313 eyes (93.5%) glaucoma was controlled at one year following surgery. Using Kaplan Meier actuarial survival analysis we found that eyes controlled in infancy by one or more goniotomies are at risk of relapse of glaucoma for at least 15 years although 93% of eyes are still controlled five years after the initial surgery. Patients whose symptoms of congenital glaucoma presented at birth were more likely to relapse than those whose symptoms developed in the first few months of life. Eyes requiring multiple goniotomies in infancy were more likely to relapse than those controlled by a single procedure.

Of a series of 201 corneal transplants for keratoconus over a 20-year period, 42 grafts (39 eyes of 38 patients) required further surgery because of intolerable astigmatism (range, -3 diopters [D] to -18 D; mean, 8.9 D). Relaxing incisions, compressive resuturing, and augmented relaxing incisions were the techniques used. All procedures resulted in a similar mean reduction in cylinder -3.6 to 5 D, but the outcome with augmented relaxing incisions was less predictable. Six grafts required two or more procedures for a satisfactory outcome. All patients had corrected visual acuity of 20/30 or better after surgery, and 75% had visual acuity of 20/20 or better. The cumulative time until 90% of the grafts had useful vision was 32 months after refractive surgery. Relaxing incisions offer the prospect of more rapid visual rehabilitation than compressive resuturing.

The effects of different doses of beta radiation from a strontium-90 source on the proliferation of human Tenon's capsule fibroblasts were studied. The cultured fibroblasts were exposed to doses of 100, 250, 500, 750, 1000, 1500, and 3000 rads, and cell numbers were counted at days 3, 7, and 14. Treatment inhibited the proliferation of the fibroblasts. At seven days the cells exposed to 3000 rads showed a decrease relative to the starting cell numbers, and at 14 days the cells exposed to 1500 and 3000 rads showed a decrease in cell numbers. The doses of radiation which inhibited cell proliferation more than 50% (at day 7 and 14) and yet did not cause a decrease in the cell population were 500, 750, and 1000 rads. beta Radiation reduces the proliferation of human Tenon's capsule fibroblasts, and at higher doses this effect may be more pronounced one and two weeks after irradiation.

Sixty-six eyes with congenital glaucoma were subjected to trabeculectomy between July 1975 and June 1989 are presented. Thirty-one were treated with beta irradiation at the time of surgery with a strontium-90 applicator; 35 were not treated with beta irradiation. The usual dose was 750 rad. Analysis was limited to three years because of the shorter follow-up of the irradiated eyes. Failure in the two groups was compared statistically. When failure was categorised as IOP greater than 21 mm Hg, beta irradiation was found to be significantly protective with an adjusted risk ratio of 0.31 (95% confidence interval 0.11-0.90, p less than 0.05). Failure categorised as the need for additional medical treatment or further surgery showed significant protection with an adjusted risk ratio of 0.33 (confidence interval 0.12-0.94, p less than 0.05). Multiple regression models were used for the analysis of intraocular pressure; beta irradiation was associated with a significantly lower IOP at six months, one year, and three years (p less than 0.05). Other factors identified as being associated with a reduced failure rate or lower IOP were: no previous topical glaucoma medications: age over seven years; lack of previous surgery involving the conjunctiva. The results indicate that beta irradiation may have a beneficial effect on the prognosis of trabeculectomy in children with congenital glaucoma. However, because of the retrospective and observational nature of the study, the results must be regarded as tentative.

An infant with congenital hypertrichosis lanuginosa (CHL) and congenital glaucoma is presented. Both conditions are rare and have not been previously reported to occur in association.

Penetrating keratoplasty was performed as an emergency procedure in 52 eyes which had perforated from acute microbial keratitis and in a further 11 where perforation had not yet occurred. The results are compared with those of keratoplasty in 33 non-infected perforations and 20 eyes where there had been microbial keratitis which had responded to medical therapy leaving a scarred cornea. This latter group had both a better five year survival (90%) compared to all the others (51%), p less than 0.05, and achieved significantly better visual acuities, p less than 0.005.

One hundred and forty acute corneal rejection episodes in 94 patients were studied retrospectively. Sixteen episodes in 15 eyes were associated with raised intraocular pressure (IOP) on admission, three of whom had had previously elevated IOP. At six weeks, six (37.5%) still required hypotensive therapy. Five eyes with raised IOP at rejection had lost vision at six weeks. Five of the six eyes with graft failure at review had raised IOP either pre-graft, at rejection or at follow-up. Eyes grafted for herpes simplex keratitis with hypertensive rejection episodes had a higher mean admission IOP, with a more short-lived rise than other eyes.

A 60-year-old woman receiving prednisolone therapy for Sjögren's syndrome presented with corneal perforation. Therapeutic penetrating keratoplasty was performed, but no causative organism was identified. Focal inflammatory infiltrates in both donor and host cornea and anterior uveitis developed postoperatively. Five months later the inflammation rapidly became much worse, with fulminating abscesses, and the eye was eviscerated because of severe endophthalmitis. Nocardia organisms were identified in the cornea, conjunctiva and vitreous by means of acridine orange and modified Ziehl-Neelsen stains. The infection produced both suppurative and granulomatous inflammation. Reexamination of the penetrating keratoplasty specimen with a modified Ziehl-Neelsen stain revealed a few Nocardia organisms, which suggested that infection had occurred at the time of corneal perforation.

We report the results, over a 20 year period up to 1989, of 201 penetrating keratoplasties in 198 eyes of 158 patients. The five year graft survival was 97%. A corrected visual acuity of 6/12 or better was attained by 91%. The mean spherical equivalent refraction on removal of sutures was -2.68 Ds and the mean cylindrical correction was -5.56 Ds. The cumulative time to dispensing final refractive correction was 38 months for 90% of patients. Rejection episodes occurred in 20% of grafts and were associated with loosening of sutures and bilateral grafts. Atopic patients (28%) were not at greater risk from rejection. Graft refractive surgery was undertaken in 18% and, of these, 55% achieved 6/12 vision or better with an refractive correction which could be dispensed and tolerated within 6 months.

Graft survival has been evaluated for patients who underwent subsequent intraocular surgery (extra-capsular cataract surgery or trabeculectomy) between 1983 and 1989. The patients were different from the majority of keratoplasty patients as evidenced by the indications for keratoplasty; corneal perforation was the indication in 24% of cases. Perforated and inflamed eyes were treated aggressively at the time of the acute event, including emergency keratoplasty and intensive topical steroids. Visco-elastic fluids were routinely used during secondary surgery and topical steroids were administered intensively post-operatively. The incidence of post-operative graft rejection was low (less than 14%). Rejection episodes were diagnosed early, prior to the appearance of a Khodadoust line, and were treated aggressively with intensive topical steroids. Glaucoma which was not controlled by topical therapy was surgically managed by trabeculectomy in the first instance. If this failed, tube drainage was performed and long-term topical steroids were administered. The only risk factor identified was uncontrolled glaucoma, P = 0.1. The probability of graft survival (at five years) was 0.83 after cataract surgery and 0.62 after trabeculectomy, but wide confidence limits indicate the difference is not significant.

Thirty cases of microbial keratitis after penetrating keratoplasty were reviewed to examine the associated risk factors, the spectrum of pathogens and the prognosis for graft survival and visual outcome. The indications for keratoplasty in this group differed markedly from those for all corneal grafts performed with a much higher incidence of previous microbial keratitis and of herpes simplex keratitis. A positive culture was obtained in 93% of cases and in contrast to microbial keratitis overall, Gram positive organisms predominated particularly streptococcus pneumoniae and staphylococcus aureus. Risk factors identified were loose or broken sutures, graft decompensation and a poor ocular surface environment. There was a poor prognosis for graft survival with only 23% of cases retaining a clear graft. Overall 53% of cases were regrafted.

The results of 99 second grafts in individual eyes are reported. The five-year survival of these grafts was 49%. Allograft rejection was responsible for the majority of failures, but recurrence of host disease and endothelial decompensation were also important. Glaucoma was an important complication in 38% of eyes. Only 12 eyes in the series had no significant complication and 18 eyes achieved a corrected visual acuity of 6/12 or better.

The recurrence of macular corneal dystrophy within a corneal graft has been described in a number of case reports. In this study, we reviewed 41 transplants in 31 eyes of 16 patients undergoing keratoplasty for macular corneal dystrophy confirmed by histopathological examination. The follow-up time ranged between 25 and 408 months from initial diagnosis. Six eyes of four patients had repeat keratoplasty because of clinical recurrence and visual impairment. Pathological confirmation was available in five of the six eyes. Peripheral clinical recurrence was observed in two more eyes. The size of the graft used was inversely related to the recurrence.

We produced experimental immune reactions by exchanging peripheral corneal transplants between rabbits. Clobetasone butyrate 0.1% and dexamethasone phosphate 0.1% eye drops were equally effective in delaying corneal allograft rejection.

Minor and major deficiencies of enzymes affecting galactose metabolism may be associated with cataracts of early onset. Results are presented for 10 such families with minor enzymatic disorders. Expression of the major disorders probably involves galactitol accumulation and osmotic lens damage but this mechanism is not obviously associated with minor disorders. The observed incidence of minor incomplete enzymatic disorders of galactose metabolism in families with an incidence of cataracts of early onset may be at least partly incidental.

A previously reported cohort of patients was reviewed after mean follow-up of 10.9 years. The overall probability of survival was 45%, but first grafts had a greater probability of survival than second (P = 0.12) or further (P = 0.19) grafts. Preoperative active keratitis adversely affected survival (P = 0.123). The major cause of failure was graft rejection. Regrafts were more likely to fail from rejection episodes (P = 0.0005). Antiviral prophylaxis improved the outcome for rejection (P = 0.005) and reduced the incidence of HSK recurrence complicating rejection. Suppurative keratitis occurred in 12.4% of grafts as a complication of epitheliopathy including HSK recurrence. The outcome in these cases was particularly poor. Loose continuous graft sutures resulted in graft failure in 10.6% of grafts which may be improved by using interrupted suturing. Our results suggest the longterm prognosis for grafting in herpes simplex keratitis are not as good as may have been predicted from previous analyses.

Seventeen grafts of 10 mm in diameter or larger have been performed on 16 eyes of 15 patients. The major indications for surgery were infections or perforations or both. Follow-up has ranged from 8-54 months (mean 26.4). The 4 year survival probability was 0.64. Although the procedure was successful in saving all but one eye and restored useful vision in the majority, complications including cataract, glaucoma, graft rejection episodes and infections were encountered. The management of these complications is described. At final review, 13 eyes had clear grafts including those in whom regraft had been performed. These results have only been achieved by close co-operation between patients and the medical team responsible for their care.

A case of reduplication of the lens with uveal coloboma is described. This is a rare condition and, unlike the two previously reported cases, the other ocular structures and adnexae appeared normal.

Graft survival in a previously reported cohort of patients recruited between 1967 and 1978 (10.6 years' mean follow-up) was reviewed and compared with that for a cohort recruited between 1979 and 1987 (3.8 years' mean follow-up). This allowed analysis of improved graft survival due to changes in management, introduced after critical review of the first group in 1978. The salient changes included transition from intracapsular to extracapsular cataract surgery (P = 0.001) and treatment of rejection episodes with antiviral prophylaxis. Extracapsular cataract surgery improved graft survival (P = 0.07) benefiting inflamed eyes which more frequently required concomitant surgery (P = 0.005). Survival of rejection episodes was improved by antiviral prophylaxis (P = 0.02), and the incidence of recurrent keratitis was reduced (P = 0.0005). The complete and prompt removal of loose sutures improved graft survival (P = 0.025). Long-term survival of first grafts was 70%, and management changes improved overall survival (P = 0.036) despite an increased number of eyes (P = 0.05) grafted when inflamed.

The endothelium of the normal corneas of 67 human subjects was studied in vivo with the specular microscope in order to quantify the method as a means of sampling the cell density of the tissue. It was found that (1) axial cell counts of the endothelium are reproducible in the same cornea after an interval of time; (2) the cell counts of the centre and periphery of the same cornea are similar; (3) the axial cell counts of pairs of eyes are similar; and (4) there is a gradual reduction of cell number with increasing age. The significance of these data is discussed.

One hundred thirty-two penetrating keratoplasties (91 patients) for herpetic keratoplasty were reviewed retrospectively. The overall survival rate of clear keratoplasties to two years was 64% and to five years was 62%. The significant prognostic factors were preoperative ocular inflammatory status and degree of corneal vascularization. The two-year survival rate of a clear keratoplasty was 69% where eyes were inflamed at the time of surgery, compared with 44% in actively inflamed eyes. Allograft rejection, the major cause of a clouded herpetic keratoplasty, increased in frequency with increasing corneal vascularization. Antiviral cover was not used with routine postoperative steroids or with steroid intensive therapy for rejection. Epithelial herpetic recurrences occurred in 32% of eyes undergoing allograft rejection within four months of initiation of treatment for rejection. This is compared with otherwise uncomplicated keratoplasties where the epithelial recurrence rate was 6% at four months, on high-dose postoperative corticosteroid therapy without antiviral cover.

We used the photodynamic inactivation technique with proflavine as the photoactive dye to treat herpetic epithelial keratitis in a preliminary study of patients who had idoxuridine toxicity or resistance. A comparative study with idoxuridine in treating dendritic ulcerations of the cornea showed a good therapeutic effect. But the investigation was suspended when adverse reactions, consisting of a generalized epithelial keratitis and an anterior uveitis, possibly of phototoxic origin, developed in a few patients receiving treatment. The ulcers treated by photodynamic inactivation apparently healed by a process of "debridement" followed by subsequent re-epithelialization.

We present our evaluation of the McCarey-Kaufman (M-K) method of corneal storage. Sixty-six rabbit corneas were stored in the M-K medium at 4 C for periods of four, eight, and 12 days. Endothelial viability was assessed, using the specular microscope, the phenomenon of temperature reversal, and known inhibitors of endothelial cell function. Our results support those of McCarey and Kaufman, who showed that rabbit corneas will remain viable when stored by this technique. We were unable to support the contention that M-K medium-stored corneas are functionally superior to those corneas stored in moist chambers in the conventional manner. An unsuccessful attempt was made to correlate the function of the endothelium with either its morphological appearance as seen through the specular microscope or changes in ultrastructure as shown by transmission electron microscopy.

The endothelial function of rabbit corneas stored in modified tissue culture medium (McCarey-Kaufman medium) for periods of 4, 8, or 12 days was studied after penetrating keratoplasty using the specular microscope and the response to temperature reversal. Our results indicate that rabbit donor corneas stored in McCarey-Kaufman (M-K) medium are suitable for penetrating keratoplasty after storage periods as long as 12 days. The limitations of using graft clarity or the morphologic appearance of the endothelium as an index of the success of a penetrating keratoplasty in the rabbit are discussed.

This study includes the fourteen Icelanders who had penetrating keratoplasty for macular corneal dystrophy during 1974 through 1988, and a further five patients whose deterioration of vision has so far not led to surgery. The clinical presentation, mode of inheritance and the course of the disease were similar to those seen in other studies. The genealogical part of this study indicates that the gene responsible for the disease was already present in Iceland in the 18th century. Though consanguinity, as usually defined, was found to be uncommon, the relatively small pool of genes in the Icelandic population which numbers at present about 250,000 has led to higher prevalence of macular corneal dystrophy than elsewhere. The histopathological findings concur with the conventional description of macular corneal dystrophy, with the exception of two patients with unusually severe photophobia. In these two cases, electron microscopy revealed that the most anteriorly situated deposits were sometimes associated with increased electron-density of small clusters of basal epithelial cells in the overlying epithelium, such cells also being reduced in size and exhibiting few organelles other than swollen mitochondria.

A series of 20 patients who developed severe post-keratoplasty glaucoma unresponsive to medical therapy and trabeculecetomy were treated using silicone drainage tubing and an anterior encircling gutter. The results indicate a four year probability of maintaining vision and normal intraocular pressure (less than 21 mmHg) of 0.68. In contrast, an earlier series of 13 patients receiving cycloablation with cryotherapy did significantly worse.

The results of 35 consecutive trabeculectomies in eyes developing medically uncontrollable glaucoma following penetrating keratoplasty are presented, with a mean follow-up of 3 years from the time of drainage surgery. Five eyes remained phakic until trabeculectomy was performed. Additional medical therapy was necessary to control the intraocular pressure in 32 eyes, which therefore were considered to have failed to be controlled by trabeculectomy and 90% of these failed within 6 months of filtration surgery. Despite additional medical therapy, in 17 eyes, further drainage surgery was required and 90% of this surgery took place within the first 14 months. Adverse prognostic factors were multiple grafts and synechiae closure of the drainage angle.

Corneal graft survival in rabbits was significantly (P less than 0 . 001) prolonged by topical treatment to the recipient eye with cyclosporin A 1% in arachis oil applied five times daily for 4 weeks. No graft was rejected whilst treatment was maintained but all grafts subsequently underwent rejection by the 64th postoperative day. All animals in a simultaneous control group in this fully masked study developed allograft reactions by the 23rd day. No local or systemic side-effects attributable to cyclosporin A were observed. It is believed that this is the first report of inhibition of an allograft reaction by cyclosporin A applied topically.

The ultrasonic radiation utilised in phacoemulsification procedures for the removal of cataractous lenses results in the widespread production of discrete lesions in the corneal endothelium. The morphology of this induced damage has been examined in rabbit and man using both scanning and transmission electron microscopy. The illustrated results are related to both the duration of the ultrasonic exposure and to the mechanisms of damage.

The responses of corneal endothelium to a 2-minute exposure of ultrasound from a clinical phacoemulsification device have been studied by specular microscopy and both scanning and transmission electron microscope. Healing of lesions occurred in two ways, and these were related to lesion size. Small lesions healed by a process of rosette formation, and large lesions were repaired by a process of endothelial dedifferentiation and migration. All damaged areas were re-covered with endothelial cells within 24 hours of exposure, and at this time corneal thickness had returned to control levels. The implications are discussed in relation to the phacoemulsification procedure.