Effect of 1 % Sodium Hyoluronote (Healon®) on a Nonregeneroting (Feline) Corneal Endothelium Charles F. Bahn,* Robert Grosserode,f^: David C. Musch,f Joseph Feder,f§ Roger F. Meyer, f Donald K. MacCallum.f John H. Lillie,f and Norman M. Rich* A series of experiments were performed to investigate the effect of 1% sodium hyaluronate (Healon®) on the nonregenerating corneal endothelium of the cat. Aqueous humor replacement with 1% sodium hyaluronate resulted in mild, transient elevations of intraocular pressure compared to eyes that were injected with balanced salt solution. Sodium hyaluronate 1% protected the feline endothelium against cell loss incurred by contact with hyaluronate-coated intraocular lenses compared to endothelial contact with lenses that were not coated with sodium hyaluronate. The use of intraoperative 1% sodium hyal- uronate, however, did not protect against endothelial cell loss incurred by penetrating keratoplasty or prevent subsequent skin graft-induced corneal homograft rejections. Homograft rejections were milder, however, in some eyes that received grafts coated with 1% sodium hyaluronate. Image analysis of pho- tographs of trypan blue- and alizarin red-stained corneal buttons after trephining, stretching of Descemet's membrane, rubbing against iris-lens preparations, or immediately after penetrating keratoplasty dem- onstrated that the stretching of the posterior cornea is an important cause of endothelial damage that would not be protected against by a viscoelastic coating. Invest Ophthalmol Vis Sci 27:1485-1494,1986 Sodium hyaluronate is a viscoelastic glycosamino- and corneal endothelial cell replacement with cultured glycan that can coat and protect the corneal endothe- endothelium.8'9 To investigate the potential protective lium against surgical trauma in rabbits1 and humans.2 effect of a viscoelastic glycosaminoglycan on the non- The cat is a more clinically applicable model of the regenerating corneal endothelium of the cat, we per- corneal endothelium than the rabbit, however, because formed a series of experiments to investigate 1 % sodium the endothelium of the cat, like that of man, heals pri- hyaluronate (HealonR; Pharmacia, Piscataway, NJ). marily by hypertrophy and sliding of remaining cells Specifically, we wished to determine: (1) if aqueous rather than mitosis.3 The feline species has been useful humor replacement with 1% sodium hyaluronate re- in the investigation of infant4 and adult5 penetrating sults in toxicity to the corneal endothelium, (2) if 1% keratoplasties, induced corneal transplant rejections,6'7 sodium hyaluronate protects the corneal endothelium against trauma associated with contact with intraocular From the *Department of Surgery, Divisions of Ophthalmology lenses, and (3) if 1% sodium hyaluronate protects the (CFB) and Vascular Surgery (NMR), Uniformed Services University endothelium against trauma associated with penetrat- of the Health Sciences, Bethesda, Maryland, and the fDepartment ing keratoplasty and subsequent induced corneal graft of Ophthalmology (DCM, RG, JF, RFM) and Anatomy and Cell rejection. Because 1% sodium hyaluronate did not Biology (DKM, JHL), University of Michigan, Ann Arbor, Michigan. protect against endothelial cell loss incurred by pene- t Present address: 3747 Sunset Lane, Antioch, California. trating keratoplasty, we performed an additional series § Presently an Ophthalmology Resident at Northwestern Univer- sity, Chicago, Illinois. of experiments to investigate the roles of trephining, Supported by fellowships and grants from The National Eye In- corneal rubbing against the iris and lens, and corneal stitute (EY 05576), the University of Michigan Biomedical Research stretching from suturing as causes of endothelial dam- Council, the Uniformed Services University of the Health Sciences age during penetrating keratoplasty. (R09052), and Research to Prevent Blindness, Inc. Presented in part at the Association For Research in Vision and Ophthalmology (ARVO) meeting, Sarasota, Florida, May, 1983. Materials and Methods Submitted for publication: January 16, 1986. Reprint requests: Charles F. Bahn, MD, Major, USAF, MC, As- The following groups of experiments were performed sistant Professor of Surgery (Ophthalmology), Uniformed Services (specific procedures are detailed subsequently). University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814. The opinions or assertions contained herein are the private views Group 1: Aqueous Replacement of the authors and are not to be construed as an endorsement for a product or supplier, or as official, or as reflecting the views of the Nine adult cats received unilateral aqueous humor Department of Defense or the Air Force. replacement with 1% sodium hyaluronate (Healon®, 1485 Downloaded from iovs.arvojournals.org on 10/02/2021 1486 INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE / October 1986 Vol. 27 Pharmacia, Piscataway, NJ). Contralateral control eyes 3C. Ten animals received unilateral phakic rota- received aqueous humor replacement with balanced tional autografts. Contralateral eyes received "fresh" salt solution. Intraocular pressures were measured at exchange homografts, performed between pairs of an- 1 and 12 hr after the aqueous replacement procedure, imals. The endothelial surfaces of half of the autografts and paired experimental and control eyes were sub- and half of the exchange homografts were coated with sequently examined clinically each day for 7 days and 1% sodium hyaluronate, and the remaining grafts were then weekly until sacrifice. Selected pairs of experi- performed without 1% sodium hyaluronate. Eyes were mental and control eyes were examined histologically examined clinically each week for 6 weeks after kera- on days 1 (N = two pairs), 2 (N = two pairs), 5 (N toplasty. = two pairs), and 6 weeks (N = three pairs) after 3D. Ten animals each received a unilateral corneal aqueous replacement. homograft that had been maintained in M-K medium for 48 hr at 7°C prior to surgery. Contralateral eyes received uncultured homografts that were exchanged Group 2: Intraocular Lens Induced between pairs of animals. The endothelial surfaces of Endothelial Trauma half of the grafts were coated with 1 % sodium hyal- Three adult cats received unilateral endothelial uronate during surgery, and the remaining grafts were trauma by contact with intraocular lenses coated with performed without 1% sodium hyaluronate. Eyes were 1% sodium hyaluronate. Control contralateral eyes examined clinically each week for 12 weeks after ker- were similarly traumatized by lenses, but without so- atoplasty. dium hyaluronate. Eyes were examined clinically each 3E. To determine if reduced endothelial cell loss day for 7 days and then weekly for 6 weeks. (antigen shedding) or altered antigen processing asso- ciated with intraoperative 1% sodium hyaluronate might affect the incidence or clinical manifestations of Group 3: Penetrating Keratoplasties corneal graft rejection, exchange homografts (of groups Thirty-eight adult cats received consecutive bilateral 3C and 3D) were induced to reject by performing ex- penetrating keratoplasties, performed by three surgeons change full thickness skin grafts between matched cor- (from most experienced to least experienced, surgeon neal donor pairs 6 and 12 weeks after keratoplasty. 1 = 10 grafts, surgeon 2 = 51 grafts, surgeon 3=15 Eyes were examined clinically each week for 8 weeks grafts). Half of the eyes (N = 38) received donor corneas after skin grafting. with a generous endothelial coating of 1% sodium hy- aluronate. The other half received uncoated donor Group 4: Morphological Evaluation of corneas. Categories of transplants included phakic (N Traumatized Corneas = 28) and aphakic (N = 18) rotational autografts, "cul- tured" homografts that were stored in McCarey-Kauf- Coating the endothelium of corneas with 1% sodium man (M-K) medium at 7°C for 48 hr prior to surgery hyaluronate did not protect against endothelial cell loss (N = 10), and uncultured homografts that were ex- after penetrating keratoplasty (see below). To further changed between pairs of animals (N = 20). These evaluate this finding, various types of trauma that a penetrating keratoplasties were performed specifically viscoelastic substance might or might not protect as follows. against were analyzed. Endothelial damage from rub- 3A. Nine animals received unilateral rotational au- bing of the cornea against other anterior ocular struc- tografts with an endothelial coating of 1% sodium hy- tures (iris, lens, anterior vitreous), for example, should aluronate, and contralateral control rotational auto- be reduced by a viscoelastic coating. Endothelial dam- grafts without sodium hyaluronate. Eyes were exam- age from stretching, as might occur during suturing, ined clinically each postoperative day for 1 week and should not be reduced by a viscoelastic coating. Tre- then weekly until sacrifice. Paired control and exper- phining, rubbing of the endothelial surface across an imental eyes were examined histologically on days 1 iris-lens preparation, stretching of Descemet's mem- (N = three pairs), 7 (N = two pairs), 14 (N = one pair), brane, and suturing during keratoplasty were each and 4 months (three pairs) postoperatively. evaluated as sources of trauma that might contribute 3B. Nine animals underwent bilateral extracapsular to endothelial cell loss associated with penetrating ker- lensectomies followed 16 weeks later by unilateral ro- atoplasty. The following specific categories of corneas tational