Corneal Topography Asymmetry Indices Changes After Corneal Refractive Surgery

Retrospectively review the medical records of all patients who underwent refractive surgery referred from the out-patient clinic of Tanta University hospital between September 2015 and September 2020 .

Data collection will include:

Preoperative and postoperative Evaluation: Age, sex, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest and cycloplegic refraction, Slit lamp biomicroscopy, fundus examination.

Data of Corneal Tomography keratometric using Scheimpflug camera (Pentacam Oculus- Germany) :that includes the following indices

1. Average keratometric value (K mean) in diopters
2. Maximum simulated keratometry (Kmax) in diopters
3. Index of Surface Variance (ISV) in microns
4. Index of Vertical Asymmetey (IVA) in microns
5. Radii Minimum (R min) in microns
6. Index of height asymmetry (IHA) in microns
7. Index of height decantation (IHD) in microns
8. Aberration coefficient (ABR)

The data of the pentacam will be collected pre-operative and analyzed at 1 month, 3 months and 6 months with recording of the complications.

• Refractive surgery (Other): Refractive surgery for correction of error of refraction

Primary outcomes

• To evaluate the changes that occur in the corneal indices after corneal refractive surgery either PRK or LASIK. [6 months]: Using the results of measurements of Scheimpflug camera (Pentacam Oculus- Germany) :that includes the following indices 1. Average keratometric value (K mean) in diopters 2. Maximum simulated keratometry (Kmax) in diopters 3. Index of Surface Variance (ISV) in microns 4. Index of Vertical Asymmetey (IVA) in microns 5. Radii Minimum (R min) in microns 6. Index of height asymmetry (IHA) in microns 7. Index of height decantation (IHD) in microns 8. Aberration coefficient (ABR) The numbers from preoperative records will be compared with postoperative records after the refractive surgery is done . All the values will be expressed as mean ± standard deviation and the data will be analyzed as 1 months, 3 months and 6 months after surgery

Sex: All, ages: 19 Years to 35 Years

Inclusion Criteria:

* Patients who underwent refractive surgery either PRK, LASIK with age between 19 and 35 years old

Exclusion Criteria:

* Kertoconus.

  * Corneal scarring.
  * Previous corneal infections.
  * Minimum corneal thickness at the thinnest location less than 400 µm.
  * History of uveitis or ocular allergy.
  * Pre-existing glaucoma.
  * Data not available

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• Results publication: Mohammadi SF, Nabovati P, Mirzajani A, Ashrafi E, Vakilian B. Risk factors of regression and undercorrection in photorefractive keratectomy: a case-control study. Int J Ophthalmol. 2015 Oct 18;8(5):933-7. doi: 10.3980/j.issn.2222-3959.2015.05.14. eCollection 2015. PMID 26558204
• Results publication: Belin MW, Ambrosio R Jr. Corneal ectasia risk score: statistical validity and clinical relevance. J Refract Surg. 2010 Apr;26(4):238-40. doi: 10.3928/1081597X-20100318-01. No abstract available. PMID 20415320