A O S 1998

80

Intraoperative mitomycin C andthe corneal endotheliumR. Sihota, Tarun Sharma and H. C. Agarwal

Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of MedicalSciences, New Delhi, India

ABSTRACT.Purpose: Mitomycin-C (MMC) is a useful adjunct to high risk glaucomasurgery. No clinical data regarding the deleterious effect of mitomycin-C on thecorneal endothelial cells are available.Methods: Thirty eyes of 28 adult patients with high risk glaucomas were ran-domized to three groups. Group-I underwent a trabeculectomy alone, Group II,trabeculectomy with intraoperative 0.2mg/ml MMC and Group III, trabeculec-tomy with intraoperative 0.4mg/ml MMC. Preoperative and 3-month postopera-tive corneal endothelial cell counts were analysed.Results: The percentage cell loss in Group I was 3.73∫2.73%, in Group II13.90∫4.69% and in Group III 14.52∫7.8%. Statistical analysis revealed asignificant difference in cell loss between Group I and Group II and Group Iand Group III, but not between Group II and Group III.Conclusion: There is a significant loss of corneal endothelial cells three monthsafter trabeculectomy with adjunctive MMC.

Key words: mitomycin-C – trabeculectomy – corneal endothelium – cell loss – intra-operative.

Acta Ophthalmol. Scand. 1998: 76: 80–82Copyright c Acta Ophthalmol Scand 1998. ISSN 1395-3907

The intraoperative usefulness of mito-mycin C (MMC) is now estab-

lished, especially for recalcitrant glau-comas. The initial enthusiasm has beentempered by the relatively high incidenceof thin blebs, hypotony, and choroidaldetachments noted by Kitazawa et al.(1993), Wise (1993) and Shields et al.(1993). The long term effects of adjunc-tive MMC are still to be evaluated.

MMC is an antimitotic antibioticwhich could, theoretically, adversely af-fect all cells with which significant con-centrations come into contact. After ap-plication, most surgeons copiously irri-gate the exposed tissues, but a certainamount of the drug does penetrate intothe adjacent tissues. Kawase et al. (1992)have determined that 0.4 mg/ml of MMCapplied beneath a lamellar scleral flap, tothe bed of a trabeculectomy, for 5 min-utes led to a trabecular block concen-tration of 5.4 to 1.2 mg/g in humans. Ex-perimental work has demonstrated the

toxicity of MMC to the corneal endo-thelium (Derick et al. 1991, McDermottet al. 1994). There are, however, no clin-ically controlled studies of the corneal en-dothelium following the intraoperativeuse of MMC.

We have prospectively studied the cor-neal endothelial cell count in patients un-dergoing trabeculectomy alone, with ad-junctive 0.2 mg/ml MMC and 0.4 mg/mlMMC. The control group allowed a com-parative evaluation of the effectivity andthe safety of this potentially toxic adju-vant.

Material and MethodsThirty eyes of consecutive adult patientsadmitted for a high risk glaucomasurgery were enrolled in the study afterclearance from our scientific protocolcommittee. Informed consent was ob-tained. All patients had a thorough pre-

operative examination including visualacuity, slit lamp evaluation, applanationtonometry, gonioscopy, fundus examin-ation and Goldmann perimetry. Centralcorneal endothelial counts were assessedby the contact technique using the AlconPRO corneal endothelial microscope pre-operatively and 3 months postoperativelyby a masked trained technician. Video re-cordings were taken randomly at threepoints on the central cornea, and withthe help of a grid a minimum of threecounts were done, averaged, and multi-plied by 50. Any previous surgery or laserprocedure was specifically noted.

The 30 eyes of these patients were ran-domly assigned to three groups, GroupI undergoing a standard trabeculectomy,Group II a trabeculectomy with intra-operative 0.2 mg/ml of MMC for 4 min-utes, and Group III a trabeculectomywith intraoperative 0.4 mg/ml of MMCfor 4 minutes. The mitomycin C wasmanufactured by Kyowa Company, Ja-pan, and was not cut with mannitol, butcontained sodium chloride. This was di-luted with sterile distilled water. The tra-beculectomy was performed by either oneof two glaucoma specialists, under a lim-bus based conjunctival flap and a halfthickness, 4¿4 mm, lameller scleral flap.

A cellulose sponge surgical spear wascut when dry to a size of 4¿4 mm andMMC of either concentration wasdropped on it till the sponge had ex-panded and the first drop fell out. Thiswas then placed beneath the scleral flapand covered with the conjunctiva, tak-ing care that the cut edge of the con-junctiva did not come into contact withthe sponge. After 4 minutes the spongewas removed and the area of appli-cation was thoroughly irrigated with aminimum of 10ml of Ringer lactatesolution. The area was swabbed dry andsubsequently the trabecular block was

A O S 1998

81

removed. The triangular trabeculectomyflap was closed with three sutures forapposition. No viscoelastic was used inany case. Postoperatively all eyes weretreated with antibiotic-steroid dropsfour times a day.

ResultsThirty eyes of 28 adult patients with highrisk glaucomas were randomly assignedto Group I, undergoing trabeculectomyalone, Group II, trabeculectomy with theintraoperative use of 0.2 mg/ml of mito-mycin C or Group III, trabeculectomywith intraoperative 0.4 mg/ml of mitomy-cin C.

The age of the patients ranged from22–88 years; there were 17 males and 11females. The ocular diagnoses of the 30eyes were chronic angle closure glaucoma(6), aphakic glaucoma (5), uveitic glau-coma (5), concussional glaucoma (4), juv-enile glaucoma (4), open angle glaucoma(3), pseudophakic glaucoma (2) and Co-gan Reese syndrome (1).

There was no significant difference inthe preoperative intraocular pressure orendothelial count between the threegroups (Table 1). Postoperatively at 3months, the drop in the control Group Iwas only 70∫48.3 cells/mm2 as comparedto 265∫88.4 in Group II and 280∫122.9cells/mm2 in Group III. The percentagefall in the three groups was 3.73∫2.73%,13.90∫4.69%, and 14.52∫7.80%, respec-tively. Statistical evaluation by the Twosample ‘t’ test found a statistically sig-nificant difference, p∞0.001, betweenGroup I and II and a significant,

Table 1. Summary of Data(mean∫SD).

Group I Group II Group II(Controls) (0.2 mg/ml MMC) (0.4 mg/ml MMC)nΩ10 eyes nΩ10 eyes nΩ10 eyes

Intra-ocular pressure (mmHg)Preoperative (on pilocarpine) 23.8 28.2 26.42% and Timolol 0.5% ∫2.62 ∫6.2 ∫4.48Postoperative – 3 months 19 12 12.5(off medication) ∫4.81 ∫2.11 ∫3.31Endothelial Cell (Cell mm2)Preoperative 1985 1950 1995

∫242.7 ∫479.6 ∫330.4Postoperative (3 months) 1915 1685 1720

∫269.8 ∫452.8 ∫391Cell loss (3 months) 70 265 280

∫48.3 ∫88.4 ∫12.9Percentage cell loss 3.73 13.90 280(3 months) ∫2.73 ∫88.4 ∫122.9

p∞0.001 difference between Group I andIII. There was no significant differencebetween the two mitomycin groups,Group II and III. A non parametric test,Wilcoxen’s Signed Rank test, was alsodone with a statistically significant differ-ence noted, p∞0.01, between Group Iand II and Group I and III. Again therewas no statistically significant differencebetween Group II and III.

Six eyes had a significantly shallow an-terior chamber for between 2 and 4 weekspostoperatively with peripheral iridocor-neal touch, 1 in Group I, 2 in Group IIand 3 in Group III. Some eyes had ahigher endothelial cell loss than that seenin the rest of the respective groups, i.e.7.69% as compared to a mean of 2.96%in the rest of Group I, 19.43% of 12.52%in Group II and 24.99% of 10.03%. Threeeyes, two in the 0.2mg/ml MMC group(S.No. 1π6) and one in the 0.4 mg/mlMMC group (S.No. 9) had an unrec-ordably low tension with a formed,though shallow anterior chamber depthon the first postoperative day which re-turned to preoperative depth within thefirst week. S.No. 1 in the 0.2 mg/ml grouphad a drop in specular count of 14.58%,the other two lost 10% of their endo-thelial cells. An intraocular pressure ofless than 8 mmHg was seen in five others,S.No. 7 in the control group, S.Nos 2 and7 in the 0.2 mg/ml MMC group andS.Nos 3 and 6 in the 0.4 mg/ml group.There was a significantly higher cell lossin three of these, as compared to others intheir groups. No eye required a surgicalreformation of the anterior chamber.

Prior Nd YAG iridotomy (2 eyes), sur-gical iridectomy (1 eye), trabeculectomy

(5 eyes) and extracapsular cataract ex-traction (4 eyes) did not lead to a greaterendothelial cell loss after this surgery.However, one eye with previous intracap-sular lens extraction showed a cell loss of6.9% in Group I. Another eye that hadan iridencleisis and an intracapsular lensextraction had a loss of 28.57% in GroupIII. An earlier intracapsular lens extrac-tion with an anterior chamber intraocul-ar lens led to a cell loss of 20.0% in oneeye in Group II.

There was no significant difference inthe endothelial cell loss in patients belowand above and the age of 40 years, in anyof the three groups.

DiscussionMitomycin-C is being widely used intra-operatively for intractable and high riskglaucomas. Observations over the lasttwo years have brought to light the rela-tively short term complications of hypo-tony, extremely thin blebs and choroidaldetachment. The long term effects at thearea of application or in surroundingtissues are still being studied.

A chance observation led us to reviewthe literature on MMC and its effects onthe corneal endothelium. A patient withpseudophakic glaucoma developed local-ized corneal thickening and epithelialedema in relation to the area of appli-cation of the mitomycin-C, three monthsafter the surgery. This then led to a gener-alized bullous keratopathy over the nextnine months.

Derick et al. (1991) have shown that anintracameral injection of 50 ml of mito-mycin (0.5 mg/ml of balanced salt solu-tion) led to severe inflammation initially,followed by opacification and thickeningof the cornea within 72 hours. There wasa total absence of corneal endotheliumon histopathology. McDermott et al.(1994) perfused human corneas by in vi-tro specular perfusion technique, withtwo solutions of mitomycin-C for 3hours. 200 mg/ml of MMC led to prompt,sustained corneal swelling, and scanningelectron microscopy showed effacementof intercellular junctions with transcellu-lar vacuole formation. Transmission elec-tron microscopy showed vacuole forma-tion with disruption of intracellular or-ganelles. Corneas perfused with 20 mg/mlof mitomycin-C and BSS plus showed nosignificant change in three hours. Theyconcluded that proper application of in-

A O S 1998

82

traoperative mitomycin-C appears non-toxic.

A short intrascleral exposure to MMCat surgery leads to an inhibition of fi-brosis for at least the 4–6 weeks requiredfor wound healing as evidenced by theavascular, raised blebs produced. Afterintraoperative application of mitomycin-C 0.4 mg/ml for five minutes, Kawase etal. (1992) have shown a significant tra-becular block concentration of the drug.This leads one to the supposition thatsome of the drug is also entering theaqueous and coming into contact withthe endothelium.

The corneal endothelium is relativelyamitotic, but some reparative processesfor cellular DNA are necessary period-ically. The presence of mitomycin gener-ated alkylating agents would be expectedto hinder this, especially if they are pres-ent for a long time. Mitomycin has beenshown to have delayed and cumulativetoxic effects (Smith et al. 1991).

Endothelial cell density and centralcorneal thickness have been studied intrabeculectomies by Fiore et al. (1989)and Smith et al. (1991). Uncomplicatedsurgery was found to produce no signifi-cant change up to 12 weeks postopera-tively. Iridocorneal touch led to a centralendothelial cell loss of 7.1%–11.6%, whilelenticular corneal touch saw a loss ofmore than 50%. Endothelial cell changesare reported to stabilize three monthsafter intraocular surgery (Schutz et al.1986). In trabeculectomies where mito-mycin C has been used the cell loss hasbeen described as 11% at 3 months byPastor et al. (1993) and 8% at 12 monthsafter the surgery by Dreyer et al. (1995).

Our study has demonstrated a statisti-cally significant difference in endothelialcell count between eyes undergoing a con-ventional trabeculectomy and those inwhich additional mitomycin-C is used be-neath the scleral flap. This was borne outby both the statistical analyses per-formed. There was no significant differ-ence between the two MMC groups. Apostoperative shallow anterior chamber

and hypotony could increase the chancesof significant endothelial cell loss. Ourstudy is based on central endothelialcounts, and one could therefore presumethat the effect of mitomycin would begreater near the area of surgery. Periph-eral endothelial counts were performed insome patients, but a repeat count inexactly the same area could not be guar-anteed. A drawback of our study is theduration of follow-up. Our hospital is areferral hospital and most patients find itmore convenient in the long term to goback to the referring ophthalmologistcloser to home. Clinically we have noteda localized triangular area of cornealedema, based on the site of surgery, in apatient who preoperatively had low endo-thelial counts. Over a year this progressedto the formation of a generalized bullouskeratopathy.

This bears out the possibility of a con-tinuing endothelial cell loss due to theknown propensity for delayed changeswith mitomycin-C. This cell loss in anotherwise normal cornea would probablynot cause a bullous keratopathy, but alow endothelial cell count initially couldbe significantly affected by the intra-operative use of mitomycin-C, leading onto a clinically decompensated endo-thelium.

Mitomycin-C produced a central endo-thelial cell loss of around 14% within thefirst three months in our study, but itcould adversely effect reparative pro-cesses in the long term, leading to pro-gressive endothelial cell loss. A longitudi-nal follow-up of these patients is pres-ently being carried out by us.

ReferencesDerick RJ, Pasquale L, Quigley HA, Jampel

H (1991): Potential toxicity of mitomycin-C.Arch Ophthalmol 109: 1635.

Dreyer EB, Chaturvedi N, Zurakowski D(1995): Effects of Mitomycin C and fluoro-uracil supplemented trabeculectomies on theanterior segment. Arch Ophthalmol 113:578–580.

Fiore PM, Richter CU, Arzeno G, Arrigg, CA,Shingleton BJ, Bellows AR and HutchinsonBT (1989): The effect of anterior chamberdepth on endothelial cell count after fil-tration surgery. Arch Ophthalmol 107:1609–1611.

Kawase K, Matsushita H, Yamamoto T andKitazawa Y (1992): Mitomycin concen-tration in rabbit and human ocular tissuesafter topical administration. Ophthal-mology, 99: 203–207.

Kitazawa Y, Suemori-Matsushita H, Yamamo-to I and Kawase K (1993): Low-dose andhigh dose mitomycin trabeculectomy as aninitial surgery in primary open angle glau-coma. Ophthalmology 100: 1624–1628.

McDermott ML, Wang J and Shin DH (1994):Mitomycin-C and the human corneal endo-thelium. Arch Ophthalmol 112: 533–537.

Pastor SA, Williams RD, Hetherington J, Hos-kins HD, Goodman D (1993): Corneal en-dothelial cell loss following trabeculectomywith mitomycin C J Glaucoma 2: 112–114.

Schutz SO, Glasser DB, Matsuda M, Yee RW,Edelhauser HF (1986): Response of cornealendothelium to cataract surgery. ArchOphthalmol 104: 1164–1169.

Shields MB, Scroggs MW, Sloop CM and Sim-mons RB (1993): Clinical and histopath-ologic observations concerning hypotonyafter trabeculectomy with adjunctive mito-mycin-C. Am J Ophthalmol 116: 673–683.

Smith DL, Skuta GL, Lindenmuth KA, MushDC, Bergstrom TJ (1991): The effect ofglaucoma filtering surgery on corneal endo-thelial cell density. Ophthalmic Surg 22:251–255.

Wise JB (1993): Treatment of chronic post fil-tration hypotomy by intrableb injection ofautologous blood. Arch Ophthalmol 111:827–830.

Received on November 7th, 1996.Accepted on June 24th, 1997.

Corresponding author:

Dr. R. SihotaAdditional ProfessorDr. Rajendra Prasad Centre for OphthalmicSciencesAll India Institute of Medical SciencesNew Delhi – 110 029India