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This study will include patients who will undergo PRK in both eyes, for each patient each eye will be randomly allocated to one of 2 procedures:
topography-guided ablation in one eye (group I) and Q-factor customized ablation in the other eye (group II).
Alcon/Wavelight Light Laser Technolo¬gie (GmbH, Erlangen, Germany) will be used for photoablation.
The wavelight Topolyzer (Wavelight AG, Erlan¬gen, Germany)and CSO Sirius scheimpflug camera combined with Placido corneal topography (CSO, Florence,Italy) will be used before and 1, 3 and 6 months after PRK. Refrac¬tive visual outcomes and corneal aberration changes will be compared between the two treatment modalities.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| topography guided PRK in one eye | Active Comparator | Topography-guided (placido disk- based) using T-CAT Contoura treatment. |
|
| Q-value adjusted ( custom Q) PRK in the other eye | Active Comparator | The target Q will be estimated according to a nomogram considering the patient's age |
|
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| PRK | Procedure | PRK using Alcon-Wavelight Excimer Laser EX 500 |
|
| Measure | Description | Time Frame |
|---|---|---|
| change in Postoperative spherical equivalent depending on manifest refraction after autorefractometer | 1 , 3 and 6 months postoperative | |
| change in visual acuity using snellen chart | 1 , 3 and 6 months postoperative | |
| change in corneal wavefront aberrations | assessed by topolyzer | 1 , 3 and 6 months postoperative |
| change in Q value anterior at 6mm RMS, RMS of astigmatism, RMS of coma and RMS of spherical aberrations. Strehl ratio : Qvalue,RMS,strehl ratio by CSO Sirius scheimpflug | by CSO Sirius scheimpflug | 1,3 and 6months |
| change in total RMS | by CSO Sirius scheimpflug | 1,3 and 6months |
| change in strehl ratio | by CSO scheimpflug | 1,3 and 6 months |
| change in Q value | assessed by topolyzer | 1,3 and 6 months |
| Measure | Description | Time Frame |
|---|---|---|
| efficacy:ratio of postoperative decimal UDVA to preoperative decimal CDVA | ratio of postoperative decimal UDVA to preoperative decimal CDVA | 6 months |
| contrast sensitivity | cambridge low contrast sensitivity |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Eyecare centre | Maadi | Cairo Governorate | Egypt | |||
| Dar Al Oyun hospital |
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| ID | Term |
|---|---|
| D009216 | Myopia |
| ID | Term |
|---|---|
| D012030 | Refractive Errors |
| D005128 | Eye Diseases |
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| 6 months |
| predictability | eyes within 1.0 D of emmetropia | 6 months |
| safety:ratio of mean preoperative decimal CDVA to mean postoperative decimal CDVA | ratio of mean preoperative decimal CDVA to mean postoperative decimal CDVA | 6 months |
| stability | change of more than 0.5D over | 6 months |
| Giza |
| Egypt |