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Biomedical subjects

M H Friedlander

Publications and source records attributed to M H Friedlander.

At least 37 records · Page 2Linked to original sources
PubMed1983

The ultrastructure of well-healed lenticules in keratomileusis.

Two well-healed hyperopic keratomileusis homoplastica lenticules, one 4 years old, the other 5 months old, were removed from the same patient following postoperative complications of triplopia and aniseikonia. The lenticules were examined by light and electron microscopy. Both lenticules were repopulated with keratocytes throughout the lamellae. Degenerated keratocytes were observed in the 5-month-old lenticule and recipient stroma, and in the 4-year-old lenticule; no degenerated keratocytes were seen in the recipient stroma of the 4-year-old lenticule. These findings may have resulted from toxic constituents of the solutions used to preserve the donor cornea. The basement membrane was thickened in both lenticules. The epithelial cell layer was irregular in the periphery of the lenticule where Bowman's membrane was disrupted. These findings suggest that careful surgical technique that minimizes damage to Bowman's layer and basement membrane may promote more rapid epithelial healing. The histologic results suggest that the cause of this patient's triplopia was irregular astigmatism.

Aniseikonia↗
PubMed1983

Epikeratophakia: the surgical correction of aphakia. Update: 1982.

Sixty-five epikeratophakia procedures have been performed in 63 patients; visual acuity data have been tabulated on 31 patients with 4 to 30 months follow-up. Patients with more than a year of follow-up showed stable keratometry readings. Early patients achieved 70% of the predicted dioptric correction; more recent patients have achieved 87% with improvements in the lathing procedure, tissue handling, and surgical technique. Visual acuities improve with time. At any given time after surgery, acuities measured with a hard contact lens are better than those measured with spectacles; the decrease in spectacle acuity is probably a result of irregular refraction at the graft surface. The gap between contact lens and spectacle acuity decreases with time. A number of patients achieve postoperative visual acuities better than their preoperative acuities, and most achieve final spectacle acuities within a line or two of their preoperative acuities.

Aphakia, Postcataract↗
PubMed1983

Update on keratophakia.

Visual results are reported for 23 cases of keratophakia for the correction of surgical aphakia followed from 12 to 48 months. Seventeen of the 23 patients had final visual acuities of 20/40 or better. The average residual visual overrefraction was 1.87 +/- 1.79 diopters (mean +/- SE), with an increase of postoperative astigmatism of 1.70 +/- 1.33 diopters. Complications included interface deposits and peripheral epithelial deposits that did not interfere with vision. One patient had an anterior chamber penetration and subsequent penetrating keratoplasty, and two patients had lenticules removed because of corneal edema secondary to increased intraocular pressure. The major disadvantages of keratophakia are the complexity of the procedure and the time required (4 to 6 months) to achieve best-corrected spectacle visual acuity. However, because this procedure is extraocular, it is a better choice than secondary intraocular lens implantation for patients who are unilaterally aphakic and for the young patient.

Aphakia, Postcataract↗
PubMed1982

Epikeratophakia -- the surgical correction of aphakia. Update 1981.

Epikeratophakia grafts used to rehabilitate vision in adult monocular aphakic patients intolerate of contact lens correction or not candidates for IOLs were studied prospectively. Thirty-two patients who entered this study between its inception in February 1980 through February 1981 were followed for at least eight months. Patients with normal visual potential before surgery had average visual acuities with spectacle overcorrection of 20/50 at four months, 20/40 at eight months, and 20/30 at one year. Few long-term complications were seen. Empirical modification of the lathing process has decreased the undercorrection from the 5.5 diopters seen in the early patients to the 1.0 diopter seen in the more recent patients. Problems with predictability are related to the behavior of preserved corneal tissue during the lathing and the healing of these lamellar grafts. This procedure is intended for aphakic patients of whom IOL and contact lens correction is not possible.

Adult↗
PubMed1981

Keratocyte survival in keratophakia lenticules.

Keratocyte survival in corneal lenticules preparing by cryolathing was evaluated using the vital stain, nitroblue tetrazolium. A comparison was made between lenticules inserted in the recipient cornea immediately after grinding and those inserted after one week of storage in either glycerin or liquid nitrogen. In all three groups, no viable keratocytes stained in the donor lenticule at one or three days after surgery. Ten days after insertion, however, all three groups showed a few staining cells within the body of the lenticule, suggesting beginning repopulation of the donor collagenous framework with viable cells from the host. Since the donor keratocytes are dead, healing of keratophakia lenticules is not influenced adversely by storing the donor material. Thus, keratophakia lenticules could be prepared in advance of surgery and stored in glycerin or liquid nitrogen until needed.

Animals↗
PubMed1981

Epikeratophakia: the surgical correction of aphakia. III. Preliminary results of a prospective clinical trial.

Epikeratophakia is a newly developed, investigational form of refractive corneal surgery for the correction of aphakic vision. The procedure involves the removal of the corneal epithelium from the recipient eye and the suturing of a prelathed lamellar donor corneal graft onto the surface of the recipient cornea. We initiated a prospective clinical trial of epikeratophakia in comparison with keratomileusis; however, only 14 patients were randomized between the two procedures, after which the protocol was modified to eliminate the keratomileusis procedure. subsequently, all patients who entered into the study underwent epikeratophakia. The limited comparative study showed that epikeratophakia was at least as effective as keratomileusis in terms of visual potential and visual recovery. The major problem encountered was undercorrection, which was largely eliminated by the use of donor tissue larger in diamter than the recipient bed. Three months postoperatively, five of seven patients undergoing epikeratophakia had 20/50 or better visual acuity with spectacle overcorrection.

Adolescent↗
PubMed1981

A prospective study of the use of hyperopic epikeratophakia grafts for the correction of aphakia in adults.

The results of a prospective clinical study of hyperopic epikeratophakia grafts for the visual rehabilitation of aphakic patients are presented. Visual acuity data are given for 21 aphakic patients who have been followed for up to six months postoperatively. With spectacle overrefraction, on the average, patients were within three lines of their preoperative potential vision at three months postoperative and within two lines at six months postoperative. Three months postoperatively, two patients achieved visual acuities of 20/20, and 57% had 20/40 or better with spectacle overcorrection. Six months postoperatively, three patients achieved best-corrected visual acuities of 20/20, and 80% had best-corrected visual acuities of 20/40 or better.

Adult↗
PubMed1981

Clinical results of keratophakia and keratomileusis.

Thirteen keratophakia patients were followed for 13 to 35 months. Eighteen cases of hyperopic keratomileusis or hyperopic keratomileusis using preserved corneal tissue were followed for 2 to 30 months. All 13 patients who underwent keratophakia achieved 20/50 or better acuity. All seven patients having hyperopic keratomileusis achieved 20/60 or better acuity. Eight of the 11 patients who had hyperopic keratomileusis using donor corneal tissue achieved 20/60 or better acuity. The preservation of lenticules after lathing did not adversely affect the correlation between predicted and observed dioptric corrections. There was a statistically significant correlation between predicted and observed dioptric corrections. There was a statistically significant correlation between predicted and observed dioptric correction measured at the corneal surface when the lenticule was lathed from fresh tissue (hyperopic keratomileusis) or from relatively fresh tissue (keratophakia). However, we found that there was poor correlation between the predicted and observed corrections when the lenticule was lathed from donor tissue that had been cryopreserved for long periods of time (hyperopic keratomileusis with preserved corneal tissue).

Aphakia↗
PubMed1980

Keratophakia using preserved lenticules.

Using cats as an experimental model, we compared the clarity of fresh, glycerine-preserved and nitrogen-preserved lenticules (corneal stromal implants) in keratophakia. No difference in final clarity was observed and the change in corneal curvature was maintained. In six patients freshly cut lenticules were used; in nine patients liquid nitrogen-preserved lenticules were used. Again, no difference in final clarity or correction was noted. The use of preserved, precut tissue in keratophakia will make this technique available to the general ophthalmic surgeon.

Animals↗
PubMedDate not supplied

Radial and astigmatic keratotomy experience by residents and fellows at a teaching institution.

PURPOSE: To retrospectively study 30 cases of radial and astigmatic keratotomy performed by third-year ophthalmology residents and cornea fellows. SETTING: Tulane University Medical Center, New Orleans, Louisiana. METHODS: Patients were selected based on correction for stable myopia without or with astigmatism. Four or eight radial incisions were made using the Russian (uphill) method. The astigmatic cuts were straight transverse. RESULTS: Uncorrected visual acuity postoperatively was 20/40 or better in 28 eyes (93%). Two patients(visual acuity 20/50 and 20/70) were scheduled for secondary procedures but were lost to follow-up. Complications included three microperforations without sequelae. CONCLUSION: Radial and astigmatic keratotomy to correct myopia or myopia with astigmatism can be safe and effective in the hands of a beginning surgeon.

Adolescent↗
PubMedDate not supplied

The use of epikeratophakia grafts in pediatric monocular aphakia.

Epikeratophakia is a form of refractive surgery in which the recipient's epithelium is removed and a pre-shaped donor lenticule is sutured to the patient's cornea. Seventeen patients ranging in age from two months to 6.6 years received 19 epikeratophakia grafts for the correction of aphakic vision. The correction provided by the graft in combination with vigorous amblyopia therapy has yielded some improvement in vision in the 12 patients with successful grafts. This procedure may be particularly suitable for pediatric aphakic patients because it is extraocular and reversible and may be employed as a secondary procedure or in conjunction with cataract extraction. Only with longer follow-up of these and additional patients can these preliminary results be validated and the risk/benefit ratio of this procedure be assessed.

Aphakia, Postcataract↗
PubMedDate not supplied

Quantitative measurement of wound spreading in radial keratotomy.

BACKGROUND: Many studies of radial keratotomy have been performed, however quantitative laboratory evaluation of the biomechanics of this procedure is still incomplete. Furthermore, most measurements of strain in the past have utilized strip testing, thus destroying the normal physiological structure and water balance of the cornea. METHODS: We report on a membrane inflation method of wound spreading in intact human corneas using the Baribeau Micronscope. RESULTS: We measured a secant elastic modulus of 7.58 x 10(6) N/m2 between 25 and 100 mm Hg. The spreading of radial keratotomy incisions as a function of intraocular pressure showed a maximum spreading of approximately 50 mu at 25 mm Hg at a radius of 3.50 mm from the optical center. A slight increase in spreading was observed in proceeding from a single to four radial incisions. CONCLUSIONS: Quantitative measurement of wound spreading is an important parameter of radial keratotomy and can provide important information regarding opposing theories of the biomechanics of this operation.

Biomechanical Phenomena↗
PubMedDate not supplied

Corneal allograft rejection.

Corneal allograft rejection remains the major impediment to the success of the most commonly performed solid tissue transplant. Immunologic mechanisms, particularly cellular immunity, appear to be responsible for the majority of cases of graft failure. While the prognosis for dystrophic and noninflammatory conditions is highly favorable, the failure rate in vascularized corneas can be as high as 60%. Considerable interest in the HLA system has led to a greater understanding of the distributions of these major histocompatibility antigens in the cornea. It is generally believed that tissue typing and matching class I and class II HLA antigens will result in a higher success rate for corneal transplantation. Other strategies for reducing graft-host disparity, such as decreasing the antigen load, interfering with clonal expansion, and utilizing new forms of immunotherapy, will undoubtedly contribute to better survival of corneal transplants.

Animals↗
PubMedDate not supplied

Corneal flattening by shallow circular trephination in human eye bank eyes.

Recent reports documenting central keratometric changes after removal of failed epikeratoplasty lenticules, compared to preoperative keratometry measurements, suggest that the annular corneal wound alters corneal curvature. Central corneal steepening has also been reported following circular and hexagonal keratotomy. We performed standard epikeratoplasty trephination with a Hessburg-Barron suction trephine followed by a peripheral lamellar spreading keratotomy on seven human eye bank eyes to determine the effect of these incisions on corneal topography. In seven human eye bank eyes, the mean acute central keratometric flattening from the shallow trephine incision was 2.81 D (SD 2.28, P = .017), with no significant change in keratometry due to peripheral lamellar spreading (P = .916). Computerized numeric and three-dimensional graphic analysis of the keratographs demonstrated this central topographic flattening. Further studies are needed to investigate the reversibility of host corneal changes induced by epikeratoplasty procedures.

Cornea↗
PubMedDate not supplied

Corneal steepening in human eye bank eyes by combined hexagonal and transverse keratotomy.

An interrupted 5 mm diameter hexagonal keratotomy was modified to include six paracentral transverse incisions to augment the central corneal steepening. This combined modified-hexagonal and transverse (or hexagonal-transverse) keratotomy was performed on human eye bank eyes to an estimated 85% corneal depth yielding a mean of 7.50 +/- 1.69 diopter increase in central keratometric power (P less than .001); this finding was confirmed by keratography. These results encourage further studies of this procedure and its potential to surgically correct mild amounts of hyperopia.

Analog-Digital Conversion↗