Related Experiment Video
Updated: Jul 13, 2026
05:46
Correction of Presbyopia by Monocular Bi-Aspheric Ablation Profile
Published on: September 20, 2024
Three different techniques for photorefractive keratectomy for mixed astigmatism
Leopoldo Spadea1, Laura D'Alessandri, Stefano Necozione
1Department of Ophthalmology, University of L'Aquila, L'Aquila, Italy.
Summary
Photorefractive keratectomy (PRK) is effective for correcting mixed astigmatism. All three tested PRK techniques demonstrated similar safety, efficacy, and predictability in this study.
Area of Science:
- Ophthalmology
- Refractive Surgery
Background:
- Mixed astigmatism presents a unique challenge in refractive correction.
- Photorefractive keratectomy (PRK) is a common excimer laser procedure for vision correction.
Purpose of the Study:
- To compare the efficacy and safety of three distinct PRK techniques for correcting mixed astigmatism.
Main Methods:
- Sixty eyes with mixed astigmatism underwent PRK using three techniques: (A) combined myopic spherical/hyperopic cylindrical, (B) combined cross-cylinder/spherical equivalent, and (C) topography-supported customized ablation (TOSCA).
- Outcomes were assessed 12 months postoperatively, evaluating uncorrected visual acuity (UCVA) and refractive outcomes (de focus equivalent - DE).
Main Results:
- All techniques achieved good visual outcomes, with 90% of eyes in the TOSCA group (C) achieving UCVA of 20/40 or better.
- Mean postoperative DE was comparable across groups: 0.45 D (A), 0.55 D (B), and 0.38 D (C).
- No significant complications or substantial loss of spectacle-corrected visual acuity were observed in any group.
Conclusions:
- PRK is a safe and effective method for correcting mixed astigmatism.
- The three evaluated PRK techniques demonstrated comparable clinical outcomes in terms of efficacy, safety, and predictability.
Related Concept Videos
01:28Angle Closure Glaucoma: Treatment
Angle-closure glaucoma, or closed-angle glaucoma, is an eye condition where the iris bulges out and blocks the iridocorneal angle, resulting in a buildup of aqueous humor and increased intraocular pressure. Immediate medical attention is necessary due to the sudden onset of symptoms. The treatment for angle-closure glaucoma includes short-term and long-term approaches. Short-term treatment involves using eye drops like pilocarpine to lower intraocular pressure by increasing aqueous humor...
01:16Focusing of Light in the Eye
Light rays enter the eye through the cornea, a transparent dome-shaped tissue that is the eye's outermost layer. The cornea bends or refracts, light rays traveling to the pupil. The shape of the cornea determines how much of the light is bent and whether the image will be focused correctly on the retina at the back of the eye. Once the light has passed through both refraction layers, it converges into a single focal point onto a small area. This is where photoreceptors start transforming...