Journal of Refractive Surgery

Topical Diclofenac Following Excimer Laser: Effect on Corneal Sensitivity and Wound Healing in Rabbits

Nissim Loya, MD; Sharon Bassage, MS; Sharadini Vyas, MD; Manuel del Cerro, MD; Steve B Park, MD; James V Aquavella, MD

Abstract

ABSTRACT

BACKGROUND: Diclofenac is a nonsteroidal antiinflammatory drug (NSAJD) that is widely used systemically and topically. We studied the effect of diclofenac on corneal reepithelialization and corneal sensitivity after excimer laser treatment in rabbits.

METHODS: Twelve New Zealand white rabbits were divided into four groups (A, B, C, and D). Groups A and B received diclofenac four times and eight times daily, respectively, following a central 5 -millimeter epithelial debridement. Groups C (control) and D (diclofenac four times daily) underwent excimer laser ablation (30-micrometer depth) following manual debridement. Wound healing was compared between groups A and B and groups C and D. Sensitivity was recorded preoperatively and postoperatively 1 to 5 and 14 days in groups C and D until normal values were reestablished.

RESULTS: Total time for corneal wound healing and epithelial migration rates was not delayed in any group receiving diclofenac (A, B, and D). Sensitivity after laser ablation reached a minimum of 15% to 20% in both groups C and D by day 2 and returned to normal (100%) by day 8. The decrease in sensitivity between group C, the controls, and group D, receiving diclofenac four times daily, was not statistically significant.

CONCLUSIONS: Diclofenac can be used up to eight times daily in the rabbit without causing changes in corneal wound healing or epithelial migration rate. There was no significant, long-term reduction of sensitivity, and recovery was not affected by diclofenac. [J Refract Corneal Surg. 1994;10:423-427.!

RESUME

INTRODUCTION: Le diclofenac est une médication anti-inflammatoire non stéroithenne largement utilisée par voie générale et locale. Nous avons étudié les effets du diclofenac sur la répithélialisation cornéenne et la sensibilité cornéenne après laser excimer chez le lapin.

METHODES: Les lapins NZW (n = 12) étaient répartis en 4 groupes (A, B, C, et D). Les groupes A et B ont reçu du collyre diclofenac respectivement 4 fois et 8 fois par jour après grattage epithelial mécanique central sur 5 mm de diamètre. Les groupes C (contrôle) et D (diclofenac 4 fois par jour) ont subi une photo-ablation au laser excimer (à la profondeur de 30 microns) après un grattage epithelial manuel. La cicatrisation a été comparée entre les groupes A et B et les groupes C et D. La sensibilité était notée avant intervention et après intervention, les 1er, 5 ème et 14 ème jours dans les groupes C et D jusqu'au retour aux valeurs normales.

RESULTATS: Le temps de cicatrisation cornéenne et de répithélialisation n'était pas retardé dans aucun groupe recevant le diclofenac (A, B, et D), La sensibilité cornéenne après l'ablation au laser excimer a atteint un minimum de 15 à 20% dans les deux groupes C et D au deuxième jour avec retour à la normale au 8 ème jour 100%. La réduction de la sensibilité entre le groupe C, les contrôles et le groupe D recevant du diclofenac 4 fois par jour n'était pas statistiquement significative.

CONCLUSIONS: Le diclofenac peut être utilisé jusqufà 8 fois par jour chez le lapin, sans altérer la cicatrisation cornéenne ou Ia rapidité d'épithéiialisation. L'application locale de diclofenac est connue pour réduire la douleur après laser excimer. Dans notre étude, il n'y a pas eu de réduction significative à long terme de la sensibilité cornéenne et la récupération n'a pas été altérée par le diclofenac. Ceci implique que la sensibilité à l'effleurement et la douleur sont transportés par des fibres nerveuses différentes de la cornée et que le diclofenac n'affecte pas les fibres de la sensibilité à l'effleurement. (Translation by Jean-Jacques Saragoussi, Paris, France.)

Abstract

ABSTRACT

BACKGROUND: Diclofenac is a nonsteroidal antiinflammatory drug (NSAJD) that is widely used systemically and topically. We studied the effect of diclofenac on corneal reepithelialization and corneal sensitivity after excimer laser treatment in rabbits.

METHODS: Twelve New Zealand white rabbits were divided into four groups (A, B, C, and D). Groups A and B received diclofenac four times and eight times daily, respectively, following a central 5 -millimeter epithelial debridement. Groups C (control) and D (diclofenac four times daily) underwent excimer laser ablation (30-micrometer depth) following manual debridement. Wound healing was compared between groups A and B and groups C and D. Sensitivity was recorded preoperatively and postoperatively 1 to 5 and 14 days in groups C and D until normal values were reestablished.

RESULTS: Total time for corneal wound healing and epithelial migration rates was not delayed in any group receiving diclofenac (A, B, and D). Sensitivity after laser ablation reached a minimum of 15% to 20% in both groups C and D by day 2 and returned to normal (100%) by day 8. The decrease in sensitivity between group C, the controls, and group D, receiving diclofenac four times daily, was not statistically significant.

CONCLUSIONS: Diclofenac can be used up to eight times daily in the rabbit without causing changes in corneal wound healing or epithelial migration rate. There was no significant, long-term reduction of sensitivity, and recovery was not affected by diclofenac. [J Refract Corneal Surg. 1994;10:423-427.!

RESUME

INTRODUCTION: Le diclofenac est une médication anti-inflammatoire non stéroithenne largement utilisée par voie générale et locale. Nous avons étudié les effets du diclofenac sur la répithélialisation cornéenne et la sensibilité cornéenne après laser excimer chez le lapin.

METHODES: Les lapins NZW (n = 12) étaient répartis en 4 groupes (A, B, C, et D). Les groupes A et B ont reçu du collyre diclofenac respectivement 4 fois et 8 fois par jour après grattage epithelial mécanique central sur 5 mm de diamètre. Les groupes C (contrôle) et D (diclofenac 4 fois par jour) ont subi une photo-ablation au laser excimer (à la profondeur de 30 microns) après un grattage epithelial manuel. La cicatrisation a été comparée entre les groupes A et B et les groupes C et D. La sensibilité était notée avant intervention et après intervention, les 1er, 5 ème et 14 ème jours dans les groupes C et D jusqu'au retour aux valeurs normales.

RESULTATS: Le temps de cicatrisation cornéenne et de répithélialisation n'était pas retardé dans aucun groupe recevant le diclofenac (A, B, et D), La sensibilité cornéenne après l'ablation au laser excimer a atteint un minimum de 15 à 20% dans les deux groupes C et D au deuxième jour avec retour à la normale au 8 ème jour 100%. La réduction de la sensibilité entre le groupe C, les contrôles et le groupe D recevant du diclofenac 4 fois par jour n'était pas statistiquement significative.

CONCLUSIONS: Le diclofenac peut être utilisé jusqufà 8 fois par jour chez le lapin, sans altérer la cicatrisation cornéenne ou Ia rapidité d'épithéiialisation. L'application locale de diclofenac est connue pour réduire la douleur après laser excimer. Dans notre étude, il n'y a pas eu de réduction significative à long terme de la sensibilité cornéenne et la récupération n'a pas été altérée par le diclofenac. Ceci implique que la sensibilité à l'effleurement et la douleur sont transportés par des fibres nerveuses différentes de la cornée et que le diclofenac n'affecte pas les fibres de la sensibilité à l'effleurement. (Translation by Jean-Jacques Saragoussi, Paris, France.)

Diclofenac is a nonsteroidal antiinflammatory drug (NSAID) that is widely used systemically as an analgesic agent to alleviate acute or chronic pain and inflammation associated with a variety of disorders.1

Topical diclofenac has been shown to be an effective drug in nonimmunogenic traumatic ocular inflammation such as after cataract removal24 or after argon laser trabeculoplasty inflammation.5 Recently, it has also been reported that the application of diclofenac drops immediately after excimer laser treatment decreases pain, especially after photorefractive keratectomy.6

The purpose of this study is to evaluate the effect of topical diclofenac sodium 0. 1% (Voltaren Ophthalmic, Ciba Vision, Atlanta, Ga) on rabbit cornea reepithelialization following excimer laser treatment and manual debridement, and to evaluate the effects of the drug on corneal sensitivity after excimer laser surgery.

METHODS

We used 12 adult female New Zealand white rabbits which were treated in accordance with the AEVO resolution on the Use of Animals in Research. All rabbits were fully anesthetized before the procedures using intramuscular ketamine HCl, 44 mg/kg (Parke-Davis,- Morris Plains, NJ) and Xylazine, 5 mg/kg (Mobay Corp, Shawnee, Kan). Additionally, they received topical proparacaine 0.5% for local anesthesia as needed.

Measurement of Reepithelialization

To study the rate of reepithelialization following both manual debridement and laser surgery, a total of 12 rabbits were equally divided into four groups (A, B, C, and D). Following manual debridement, experimental group A received diclofenac four times daily and experimental group B, eight times daily. Following the 30-micrometer excimer laser ablation, control group C received no drug and experimental group D, received diclofenac four times daily. The drug doses were kept constant between the left and right eyes within each group and all eyes were independently measured and monitored throughout the healing phase. This was done to avoid any effects of systemic absorption of the diclofenac which might influence the wound healing in either eye. A 5-millimeter diameter trephine mark was placed on the central cornea of all 24 eyes to outline a wound margin. The epithelium was then manually debrided using a curette; the cornea was gently rinsed with phosphate buffered saline then checked for size and completeness using fluorescein stain and photographs of the defect area at 0, 24, 36, and 48 hours or until complete closure. All photographs were taken at a fixed focus length using TMAX ASA 400 black and white film (Eastman Kodak Co, Rochester, NY). Using the photographic negatives from the wound healing, outlines of the stained areas were traced onto plain white paper, then using the Zeiss MOP-3 image analyzer (New York, NY), automatically measured for diameter (mm) and area (mmp 2).

Manual Debridement of Epithelium

To study the effects of topical diclofenac on reepithelialization following manual debridement, the animals in groups A and B underwent identical 5-millimeter debridement procedures as described above. Postoperatively, the six eyes in group A received topical diclofenac (0.1%) four times daily and the six eyes in group B received drops eight times daily until complete closure. Clinical observations of both groups for corneal haze or inflammation were completed.

Excimer Laser Ablation

To study the effects of diclofenac on reepithelialization following excimer laser surgery (VISX Twenty-Twenty, Sunnyvale, Calif), the corneal epithelium underwent manual debridement as described above, prior to excimer laser treatment. Laser parameters of a 5-millimeter diameter ablation zone, 30-micrometer stromal ablation depth, 5 Hz frequency, and 160 µm/cmp 2 fluence were utilized. Animals were randomly selected and put into two groups. The six eyes in group C were used as controls in which no drops were administered, and the six eyes in group D received topical diclofenac (0.1%) four times daily until complete wound closure following laser ablation. Both groups C and D were evaluated for corneal wound healing and sensitivity.

Analysis of Epithelial Wound-Healing Kinetics

The estimated healing time and estimated migration rate required for total wound closure was calculated by extrapolation of the best fit regression lines during the linear healing phase to 100% closure. Analysis of epithelial wound healing reveals that it was not a linear process. That is, there was no significant change in the decrease of wound radius during the first 4 hours and between 30 and 45 hours of healing. The time period between 10 to 30 hours healed at a much faster rate indicating that the migration rate of epithelial cells cannot be interpreted with simple kinetics.7 Therefore, the analysis of wound closure consisted of the evaluation of linear regression of the decrease in wound radius between 10 and 30 hours (µm/hr).

Corneal Sensitivity After Laser Treatment

Central corneal sensitivity was measured in both groups C and. D prior to laser treatment and at postoperative days 1, 2, 3, 4, 5, and 14. Sensitivity was measured using a Cochet-Bonnet aesthesiometer starting at a 60-millimeter length according to the method of de Leeuw and Chan.8 In short, for each 5.0-millimeter segment, the cornea was gently touched with a slight bend in the nylon. Ten measurements were done and the frequencies of blinks counted. When the rabbit responded to 50% of the stimulation, this was defined as its frequency of sensitivity. When a blink reflex could not be elicited with a thread length of 5.0 mm, the result was recorded as zero (0) corneal sensitivity. The percent sensitivity of group A was plotted against group B, at all time points using paired ¿-tests ( ± SEM).

RESULTS

Reepithelialization: Manual Debridement

After manual deepithelialization of the cornea, eyes that received diclofenac four times daily (group A) healed within 53.8 (±5.3 SEM) hours with an estimated migration rate (EMR) of 61.7 ^m/hr and in those eyes that received diclofenac eight times daily (group B) healed within 47.8 ( ± 2.2 SEM) hours with an estimated migration rate of 67.8 µm/hr. There was no significant difference in either the total time of healing (p = .34) or the decrease of wound radius (p = .63) between the study groups A and B. Neither group showed significant clinical signs of inflammation or irritation throughout the wound-healing process.

Reepithelialization: After Excimer Laser Treatment

Using the same analysis of wound healing as in the manually and debrided corneas, we found a similar epithelial migration pattern to be true in those eyes that underwent excimer laser treatment following epithelial debridement. The estimated healing time in the control eyes (group C) was 51.2 ( ± 3.2 SEM) hours with an estimated migration rate of 70.8 µm/hr and estimated healing time of the diclofenac eyes (group D) was 51.7 (±2.8 SEM) hours with an estimated migration rate of 68.9 µm/hr. No significant difference was found in the healing rate of those animals receiving diclofenac four times daily after excimer laser treatment as compared to the controls (p = .91) (Table 1).

Sensitivity: After Excimer Laser Treatment

By day 2 postoperatively, the sensitivity decreased in both the control eyes (group C) and the group receiving diclofenac four times daily (group D) to approximately 20% of normal baseline. It returned to normal by day 8 in both groups with a slight hypersensitivity by day 14. Sensitivity remained near normal thereafter. Although the trend of sensitivity following excimer laser treatment indicates that there was a decrease in sensitivity in the eyes receiving diclofenac four times daily as compared to the control eyes, it is not statistically significant at any time point, p > .50 (Figure).

DISCUSSION

The surgical technique of excimer laser ablation is undergoing clinical investigation to ascertain its ability to correct refractive errors (photorefractive keratectomy),9 to remove superficial corneal opacities,10 and to smooth the anterior corneal surface (phototherapeutic keratectomy).11 Mechanical removal of the corneal epithelium prior to the laser treatment is standard procedure and causes a significant abrasion postoperatively. The rapid and complete reepithelialization of the cornea following trauma or surgery is essential since the corneal epithelium forms a functional barrier between the tears and the intraocular environment.12 Delay in epithelial wound closure prolongs visual restoration and places the cornea at risk for microbial infection.

Table

Table 1Effects of Diclofenac on Reepithelialization After Excimer Laser Photorefractive Keratectomy in RabbitsFigure: Change in corneal sensitivity following excimer ablation and postoperative diclofenac treatment as a function of time for 14 days.

Table 1

Effects of Diclofenac on Reepithelialization After Excimer Laser Photorefractive Keratectomy in Rabbits

Figure: Change in corneal sensitivity following excimer ablation and postoperative diclofenac treatment as a function of time for 14 days.

Our study indicates that diclofenac given four times or eight times daily does not delay rabbit corneal reepithelialization following a 5-millimeter diameter manual debridement. Our results also show that diclofenac administered four times daily following an excimer laser ablation does not delay reepithelialization as compared to the controls. Additionally, we compared our current data with historical controls on wound healing after manual debridement using no drugs. This data has been collected from previous studies completed in our laboratory.13,14 All wound-healing research in our laboratory employs the same procedure; adult female New Zealand White rabbits (3.0 kg) are anesthetized, the central visual axis demarcated with a 5-millimeter trephine, and manually debrided with a curette. The estimated migration rate was reproducible for the rabbit using no postoperative dings and was in agreement with data reported by others.15,16 The estimated healing time for normal healing is 48.3 hours ( ±3.1 SEM) with an estimated migration rate of 58.4 µG?/hr. We found no differences in the healing time for complete closure using the diclofenac drug as compared to normal healing without drugs (Table 2). Our findings of the time of reepithelialization after excimer laser treatment are similar to those published by others.16

Table

Table 2Effects of Diclofenac on Reepithelialization Following Manual Epithelial Removal in Rabbits

Table 2

Effects of Diclofenac on Reepithelialization Following Manual Epithelial Removal in Rabbits

During photorefractive keratectomy, a central corneal ablation is performed over a manuallydeepthelialized cornea removing Bowman's layer in the ablated area. Nerve endings are thus damaged during this procedure. While reasons for the decrease in sensitivity postoperatively may include damage to the corneal subepithelial nerve plexus, there are other factors to be considered including neurotrophic growth factors and the effect of neurotransmitters on the damaged tissue.3 Following central corneal wounding, nerve regeneration originates from the subepithelial plexus outside the wound area mainly as distinct single neurites and fine axons (leashes).8 Immunohistochemical studies have shown that tactile sensitivity rapidly recovers to 60% of levels that existed before wounding from 2.5 to 4 weeks, which correlates with the regrowth of a near normal intraepithelial nerve network with terminal endings throughout the regenerated epithelium.8,17

Corneal sensitivity is mediated by sensory stromal nerves that originate from the ciliary nerves and eventually penetrate Bowman's layer. The cornea is very sensitive and has sensations of not only heat and cold but also light touch and pain which are reported to be carried by different nerve fibers.18-21

In both the control (group C) and diclofenac (group D) after-laser-treatment groups, corneal sensitivity decreased immediately after treatment. Unexpectedly, sensitivity reached a minimum (10% to 20%) at day 3 in both groups C and D compared to the typical maximum pain reported clinically in humans. This decrease was not significantly different between either group. Since there is no difference in corneal sensitivity with or without the administration of diclofenac, this may suggest a selective effect on pain fibers of diclofenac rather than light touch nerve fibers of the cornea following the laser treatment. This does not imply that diclofenac has no effect on pain postoperatively; we know it does.1"5 It indicates again that light touch and pain may be carried by different nerve fibers of the cornea. Sensitivity recovered to 100% within 8 days in both groups which shows that diclofenac did not affect the temporary recovery of tactile corneal sensitivity.

Usual therapy after excimer laser treatment consists of corticosteroid drops and analgesics for severe pain during the first 24 to 48 hours postoperatively.22 Recently, it was reported6 that the use of diclofenac drops reduces pain in patients immediately after laser treatment. Diclofenac, an NSAID that has been used systemically for its antiinflammatory and analgesic effect for many years, is an inhibitor of the synthesis of prostaglandins. These mediators are known to sensitize pain receptors after mechanical and chemical stimulation.18 Although the action of diclofenac within the corneal nerve plexus is unclear, it may contribute to pain control and prostaglandin inhibition by selectively interfering with the subepithelial nerve plexus, especially following excimer laser surgery.

In view of our results, diclofenac may prove valuable in other forms of ocular surgery such as cataract extraction and argon laser trabeculoplasty. The use of a nonsteroidal agent when compared to corticosteriods could be beneficial in reduction or elimination of corticosteroid-related complications given the known ocular side effects of corticosteroid drops.23

REFERENCES

1. Kantor TG. Use of diclofenac in analgesia. Am J Med. 1986;80:4B(suppl)64-69.

2. Vickers FF, McGuigan LJB, Ford C, Wysowsky H, Mellars K, Koester J, Ahmed M. The effect of diclofenac sodium on the treatment of postoperative inflammation. Invest Ophthalmol Vis Sci. 1991;32(suppl):793.

3. Kraff MC, Sanders DR, McGuigan L, Raanan MG. Inhibition of blood-aqueous humor barrier breakdown with diclofenac. A fluorophotometric study. Arch Ophthalmol. 1990; 108: 380-383.

4. Araie M, Sawa M, Takase M. Topical flurbiprofen and diclofenac suppress blood-aqueous barrier breakdown in cataract surgery: a fluorophotometric study. Jpn J Ophthalmol. 1983;27:535-542.

5. Herbort CP, Mermoud A, Schnyder C, Pittet N. Antiinflammatory effect of diclofenac drops after argon laser trabeculoplasty. Arch Ophthalmol. 1993;111:481-483.

6. Sher NA, Frantz JM, Talley A, Ostrov C, Doughman D, Carpel E, Lane SS, Parker P, Lindstrom RL. Controlling ocular pain after excimer laser PRK. Proceedings of the Third American-International Congress on Cataract, IOL and Refractive Surgery, abstract. 1993:25.

7. Crosson CE, Klyce SD, Beuerman RW. Epithelial wound closure in the rabbit cornea. A biphasic process. Invest Ophthalmol Vis Sci. 1986;27:464-473.

8. de Leeuw AM, Chan KY. Corneal nerve regeneration. Correlation between morphology and restoration of sensitivity. Invest Ophthalmol Vis Sci. 1989;30:1980-1990.

9. Sher NA, Chen V, Bowers RA, Frantz JM, Brown DC, Eiferman R, Lane SS, PArker P, Ostrov C, Doughman D, Carpel E, Zabel R, Gothard T, Lindstrom RL. The use of the 193 nm excimer laser for myopic photorefractive keratectomy in sighted eyes. A multicenter study. Arch Ophthalmol. 1991;109:1525-1530.

10. Stark WJ, Chamon W, Kamp MT, Enger CL, Renes EV, Gottsch JD. Clinical follow up of 193 µ?? ArFl excimer laser photokeratectomy. Ophthalmology. 1992;99:805-812.

11. Kornmehl EW, Steinert RF, Puliafito CA. A comparative study of masking fluids for excimer laser phototherapeutic keratectomy. ArcA, Ophthalmol. 1991;109:860-863.

12. Marshal WS, Klyce SD. Cellular and paracellular pathway resistances in the tight Cl secreting epithelium of the rabbit cornea. J Membr Biol. 1983;73:275.

13. Ishikawa T, del Cerro M, Liang F, Kim JC, Aquavella JV. Hypersensitivity following excimer laser ablation through the corneal epithelium. J Refract Corneal Surg. 1992;8: 466-474.

14. Ishikawa T, del Cerro M, Liang F, Loya N, Aquavella J. Corneal sensitivity and nerve regeneration following excimer laser ablation. In Press. Cornea. 1994.

15. Kwok LS, Madigan M. A new analysis of wound closure kinematics in the cat and rabbit corneal epithelium. Clinical and Experimental Optometry. 1986;69:4-12.

16. Hanna KD, Pouliquen Y, Waring GO ??, Savoldelli M, Cotter J, Morton K, Menasche M. Corneal stromal wound healing in rabbits after 193-nm excimer laser surface ablation. Arch Ophthalmol. 1989;107:895-901.

17. Chan KY, Jones RR, Bark DH, Swift J, Parker JA, Haschke RH. Release of neuronotrophic factor from rabbit corneal epithelial wound healing and nerve regeneration. Exp Eve Res. 1987;45:633-646.

18. Schimmelpfennig B. Nerve structures in human central corneal epithelium. Graefes Arch Clin Exp Ophthalmol. 1982;218:14-20.

19. Millodot M. A review of research on the sensitivity of the cornea. Ophthalmic Physiol Opt. 1984;4:305-318.

20. Beuerman RW, Tanelian DL. Corneal pain evoked by thermal stimulation. Pain. 1979;7:1-14.

21. Rozsa AJ, Beuerman RW. Density and organization of free nerve endings in the corneal epithelium of the rabbit. Pain. 1982;14:105-120.

22. McDonald MB, Leach DH. Myopic photorefractive keratectomy: U.S. experience. In: Thompson F, McDonnell P, eds. Color Atlas I Text of Excimer Laser Surgery. New York, NY: Igaku-shoin Medical Publishers Ine; 1993:37-51.

23. Havener WH. Corticosteroid therapy. In: Klein EA, eds. Ocular Pharmacology. 5th ed. St Louis, Mo: CV Mosby Co; 1984:433-500.

Table 1

Effects of Diclofenac on Reepithelialization After Excimer Laser Photorefractive Keratectomy in Rabbits

Figure: Change in corneal sensitivity following excimer ablation and postoperative diclofenac treatment as a function of time for 14 days.

Table 2

Effects of Diclofenac on Reepithelialization Following Manual Epithelial Removal in Rabbits

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