Exploring Laser Eye Treatments Based on Eye Anatomy

Lasers have been used in ophthalmology since the inception of lasers as a concept. Modern day lasers are used commonly to eliminate eye numbers and that’s how generally people know about laser eye treatments. Depending on the purpose and part of the eye where we do lasers, we can distinguish them into procedures as described below:

Diagnostic Use of Lasers:

Lasers are crucial in diagnosing various eye conditions, particularly in confocal scanning laser ophthalmoscopy (CSLO). CSLO is employed to scan the optic nerve in cases of glaucoma, confirming and tracking its progression. The Optical Coherence Tomography (OCT) test, used for scanning the retina in cases of diabetes, retinal swellings, and optic nerve issues, also incorporates laser technology. The wavelength of lasers varies depending on the specific plane of the eye being scanned.

Therapeutic Use of Lasers

Anterior Segment of the Eye:

• Cornea: LASIK / Laser Surgery: This is the most commonly performed laser eye surgery in ophthalmology. Here, a laser is used to reshape the cornea which is the frontmost transparent part of the eye. The laser basically reshapes the cornea by chipping a certain thickness of it in such a way that your eye number is reduced. Thus, one must have sufficient corneal thickness to safely undergo laser eye surgery to eliminate eye prescription. There are different procedures under this refractive surgery section using lasers where the steps may vary but the basic principle of eliminating eye number remains constant.
• Glaucoma: Certain laser wavelengths are used to treat glaucoma by photodisruption of iris to create a small opening which reduces the intraocular pressure (IOP) in glaucoma patients.
• Cataract Surgery: It is the most common vision corrective surgery that is performed across the globe. With the advent of newer technology, it is possible to incorporate lasers while performing cataract surgeries as well. What usually happens in a cataract surgery is that the surgeon enters the eye and opens up the bag in which the cataractous lens is present and then cuts the lens into small pieces to emulsify and suck it out of the back. This process involves excessive manipulation of the eye, thus to bypass this, lasers are used to make the opening and the outline of cuts on cataractous lens without entering the eye. Later the surgeon enters the eye to just emulsify, suck the lens out and to implant the IOL. Studies have reported improved and speedy recovery of these patients. 
• Post Capsular Opacification: After cataract surgery, the artificial lens (IOL) is implanted in the bag in which the previous cataractous lens was present. The IOL takes the support of this bag to be in its desired place to give the perfect vision to the patient. Although cataract is removed, there still are Lens Epithelial Cells (LEC) in the bag which may start to migrate towards the IOL and start accumulating behind the lens causing the bag to turn opaque thereby decreasing the vision. This can be treated using an Nd – YAG laser, by an OPD procedure known as Nd – Yag Capsulotomy where the surgeon simply shoots laser lights to burst open the opacity which makes the vision clear again for the patient.

Posterior Segment of the Eye:

• Retinal Breaks: As the name suggests, these are small breaks noted in the retina which is the back portion of the eye. These breaks can lead to severe conditions known as retinal detachments or may allow fluid infusion in the retina causing reduced vision. These breaks are thus important to be sealed off using a laser.
• Lattice Degenerations: These are weak spots noted in the peripheral retina of patients having glasses prescription with high minus number. These lattice degenerations can turn into breaks and eventually detachments if not treated on time. Again, to strengthen the retinal tissue, your eye doctor uses a laser to seal these weak spots. This procedure is known as Retinal Barrage Laser.

Proliferative Diabetic Retinopathy: Diabetes particularly affects the small blood vessels in the retina which puts an oxidative stress on the eye. This leads to activation of Vascular Endothelial Growth Factor (VEGF) which is responsible for creating weak blood vessels with poor cell support which means these blood vessels can burst anytime causing multiple hemorrhages in the retina or even in the vitreous humor in the posterior segment. Thus, retinal lasers are used to destroy these leaky blood vessels so that the bleeding stops, a procedure known as Retinal Photocoagulation.

The following Flowchart from eOphtha helps to summarize the above information: