Photorefractive Keratectomy a Predicative Procedure with Mitomycin – C in Myopic Patients. (Case Study)

Objective:To evaluate refractive error status, visual acuity outcome and satisfaction level in patients treated for myopia
with photorefractive keratectomy.
Materials and Methods: This study was carried out from 2012 to 2018 on myopic patients undergoing photorefractive
keratectomy. 42 patients were selected with age range from 21-29 years with mean age of 23.5 years. Out of 42 patients
15 (35.7 %) were male and 27 (64.23%) were female. All these patients had stable refractive error for one year. Proper
informed consent was obtained . Corneal topography was done. Topical alcaine drops were instilled into eyes. Central
optical zone debridement was done with soaked alcohol swab and spatula. Excimer laser were applied according to the
desired level. After laser Mitomycin C was applied for 15 seconds and then thoroughly washed. Bandage contact lens
were applied .Topical antibiotic drops were put in eyes. Patients were put on topical antibiotic /steroid drops for two weeks,
nepafenac for one month and systemic diclofenac for five days. Contact lenses were removed after 4 days. Patients
refractive error status, visual acuity and satisfaction level was recorded after 6 months
Results: Preoperative spherical error was from -2.75 to -7.25 diopters, cylindrical error was - 0.5 to -3.5 D cylinder and
spherical equivalent -2.75 to -8.0 diopters. Post operative spherical error was from -0.25 to -1.0 diopters, cylindrical from
0 to-0.75 diopter cylinder and spherical equivalent from -0.25 to -1.25 diopters. Visual acuity of 6/6 was recorded in 39
( 92.85%) and 6/12 in 3 (7.14%) patients. 37 (88.09%) patients were very satisfied and 5(11.90%) patients were satisfied
from results of laser procedure.
Conclusion: PRK is very effective procedure for correction of myopia .
Key Words. PRK (photorefractive keratectomy) ,V.A (visual acuity), DS (diopter spherical), DC (diopter cylinder).

INTRODUCTION:

Laser surgery is a procedure in which excimerlaser is used to vaporise parts of the cornea in order to reshape it . With reshaping procedure it corrects visual impairment. Now a days it is effective procedure for permanent solution of refractive disorders including myopia, hypermetropia and astigmatism. PRK was  first introduced in 1988 and has been a gold standardtreatment for low to moderate myopia and astigmatism1. Initially some complications of PRK like corneal haze and myopic regression were noted 2,3,4. But acquainting the procedure with safe hands and improving experience these complications were slowlyeliminated and the ophthalmologists considered this procedure as safe, effective and more predictable to correct myopia 5,6. PRK is warding procedure and has excellent safety profile. In the past main drawback of surface corneal ablation was the high of possibility of keratocytes activation leading to haze and regression of refractive outcome.


1.Associate Professor 2. Professor 3. Assistant Professor


For Correspondence: Dr Mohammad Alam Associate Professor
Ophthalmology KMU- IMS KDA Teaching Hospital Kohat. Cell:
03015956974 E.Mail> malamktk@gmail.com


Received: May’2019 Accepted: June’2019


PRK is effective, predicative and rewarding procedure which is stable and safe for the treatment of myopia. It eliminates the long term use of glasses and avoids contact lenses related complications. For good accounting results proper patient selection, refraction, age and topography should be considered.



With continuous research focus on these issues in the last decade PRK outcome have been made good avoiding haze formation and regression particularly with intraoperative use of Mitomycin C 7,8.Mitomycine C acts as alkylating agent inhibiting DNA and protein , Inhibiting proliferation of rapidly growing cells such as fibroblast causing cell apoptosis. Mitomycin C is also being used with encouraging results in other ophthalmic surgical procedures like trabeculectomy, ptreygium,DCR etc 9,10. The objective of this study is to know the refractive error status, visual acuity and patients satisfaction level with PRK for correction of myopia.

MATERIALS AND METHODS:

This study was conducted on myopic patients undergoing PRK with the objective to know the refractive status, VA and patients satisfaction level from 2012 to 2018. Total 42 patients out of which 15 (35.71%) were male and 27 (64.28%) we female(table I)



were included in the study, The age range of patients was from 21 to 29 years with mean age 23.5 years. Informed consents were taken and proper proforma was made for documentation of patients results data. Anterior and posterior segments examination was properly done for any associated pathology. Inclusive criteria:

  • Myopic patients
  • Normal fundi patients
  • Non traumatic eyes
  • Stable refraction for one year
  • Exclusive Criteria:
  • Traumatic eyes
  • Previous surgery
  •  Previous PRK


Preoperative refractive status was checked in the form of spherical, cylindrical and spherical equivalent (table-II).



Corneal topography of all the patients were properly done for elective PRK. During procedure alcaine drops were instilled into the eyes .Epithelial debridement was done with soaked alcohol swab and spatula for clearing of central corneal optical zone of 6mm. PRK was done according to the calibrated need. Mitomycin C drops were put for 15 seconds and then thoroughly washed. Bandage contact lenses were applied. Antibiotic drops were put topically. Antibiotic + steroid topical drops four times a day fortwo weeks were prescribed . Diclofenac sodium tablets were prescribed for 5 days. Artificial tears along with nepafenac were advised for one month. Dark glasses were advised for 2 weeks. Contact lenses were removed after 4 days. Final refractive status, V.A and patients satisfaction level were recorded after 6 months of PRK.

RESULTS:

After 6 months of PRK the refractive status was from -0.25 to -1.0 DS spherical, from 0 to -0.75 DC cylinder and spherical equivalent was from 0 to -1.25DS (table-III)



Post PRK V.A at the end of 6 months was 6/6 in 39 (92.8%) patients and 6/12 in 3 (7.1%) patients (table IV).



Patients satisfaction level at the end of 6 month was observed. 39(92.8%) patients were very satisfied and 3(7.1%) were satisfied(table V).
 


DISCUSSION:

PRK is a very safe and effective procedure for correction of myopia. People opt PRK to get rid of glasses and avoid contact lens related complications. Moreover in social set up patients do not want glasses particularly female patients. This is the reason that mostly female patients undergo this procedure as reflected in our study. Our study demonstrates dramatic decrease in the refractive error of the patients by PRK and improvement in VA without refraction being comparable with national and international studies. Lombardo studies in 2010 has revealed mean spherical error of - 0.11 ± -50D while Diakon has reported it as -0.27± -0.70D which are comparable to our study 11,12.with use of Mitomycin C with PRK for myopia. According to their study after PRK mean diopter spherical equivalent before surgery was -3.40 ± 1.73 and post PRK it was 0.08 ± -0.40 13. Nouman Hashemi et al. study reported post operative refractive status of spherical -0.3 to 1.5 DS, cylindrical -0.8 to -0.6 DC and spherical equivalent of -0.6 to -1.6DS being comparable to our study. This study also reports patients satisfaction level being lesser than our study14. Our study has reported visual equity of 6/6 in 92.85% patients and 6/12 in 7.14% patients after PRK. Tu-Ling, Liu, et al has reported VA of 6/6 in 79.2% patients15. Bradley et al study has shown VA of 6/6 in 81.5% patients16. Chadfen et al reported V.A of 6/6 in 25% patients in high myopia with PRK 17. The variation in results are mostly due to patient selection, experienced refraction assessment and topography and machine use. Moreover age of patients has very important role in final outcome. PRK has shown its efficacy for correction of myopia from low to high myopia 18,19. It is common procedure subjected to affordability. With use of Mitomycin C the haze and regression chances are less.

CONCLUSION:

PRK is effective, predicative, awarding procedure which is stable and safe for the treatment of myopia. It eliminates the long term use of glasses and avoids contact lenses related complications. For goodaccounting results proper patient selection, refraction, age and topography should be considered.

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