Myopia - Treatment or management 5/5

Treatment or management of Myopia:

a. Optical Correction: 

• Optical correction contain:
• i. Spectacles: Concave lens
• ii. Contact Leses
• Whether spectacles or contact lenses are preferable in a given case depends:
• Patient age,
• Motivation for wearing contact lenses, 
• Compliance with contact lens care procedures, 
• Corneal physiology, and 
• Financial considerations.

b. Medical (Pharmaceutical):

• Cycloplegic agents are sometimes used to reduce accommodative response as part of the treatment of pseudomyopia.
• Some studies have reported that daily topical administration of atropine139-142 and cyclopentolate142 reduces myopia progression rates in children with youth-onset myopia.
• Problems associated with cycloplegic agents are:
• Risks associated with chronic cycloplegia, 
• Light sensitivity due to pupillary dilation, 
• High plus lens additions(2.5D), 
• Retinal adverse effects.

c. Vision Therapy:

• Unaided visual acuity can be improved in patients with myopia using vision therapy, but myopia does not appear to be reduced, it reduce myopic progressionrates.
• Vision therapy to reduce accommodative response is often provided for pseudomyopia.
• Auditory biofeedback has also been used successfully in the treatment of pseudomyopia.

d. Orthokeratology:

• Orthokeratology is generally performed only on adults.
• In Orthokeratology a series of contact lenses, over a period of weeks or months, to flatten the cornea and reduce myopia.
• Studies shows that orthokeratology with standard rigid contact lenses can reduce upto 3D and average reduction 0.75D to 1D
• However, studies suggest that refractive error shifts toward the original baseline in patients who stop wearing contact lenses.

e. Refractive Surgery

I. Corneal Based:

1. Radial keratotomy (RK):

• A spoke-like radial pattern of incisions in the paracentral cornea leaving central 4mm
• When incisions heals it makes the central cornea flattens.
• The amount of resultant refractive change depends on the size of the optical zone and the number and depth of the incisions.
• It can correct Upto 2-6D.
• Complications of RK include 
• Diurnal variation of refraction and visual acuity, 
• Glare, 
• Monocular diplopia, 
• A presumably permanent reduction in best corrected visual acuity, 
• Increased astigmatism, 
• Irregular astigmatism, 
• Induced anisometropia, and 
• A gradual shift toward hyperopia that continues for months or years after the surgical procedure

2. Photorefractive keratectomy (PRK):

• Central optical zone of anterior corneal stroma is photo alated using excimer laser to cause flatening of cornea.
• It can correct upto mild to moderate myopia (2-6D)
• Complication include: 
• Corneal haze, 
• Corneal complications, 
• Reduced contrast sensitivity, 
• Glare and perceived distortion.

3. Cryolathe keratomileusis:

• A section of corneal stroma is removed, frozen, and shaped on a lathe to minus power.
• It is then replaced in the cornea to reduce corneal power. Cryolathe keratomileusis is used for more severe myopia.

4. Automated lamellar keratomileusis (ALK):

• A layer of corneal epithelium and superficial stroma of predetermined thickness is removed with a microkeratome except for a small attachment to the cornea.
• The microkeratome is then used to remove a specific amount of corneal stroma to flatten the cornea after which, the flap of superficial corneal tissue is replaced.

5. Laser in situ keratomileusis (LASIK):

• LASIK is similar to ALK, except that corneal stromal tissue is removed by a laser rather than by microkeratome
• A layer of corneal epithelium and superficial stroma of predetermined thickness is removed with a microkeratome except for a small attachment to the cornea.
• Excimer Laser is then used to remove a specific amount of corneal stroma to flatten the cornea after which, the flap of superficial corneal tissue is replaced.
• Advance Technology in LASIK:
• Customize LASIK or C-LASIK: 
• Based on Wavefront technology 
• It can correct spherical, cylindricaland aberrations of eye.
• Provides vision beyond 6/6, e,g. 6/5 or 6/4
• Epi LASIK or E-LASIK:
• Only remove the epithelial sheet using "Epiedge Epikeratome"
• Then Excimer Laser is then used to remove a specific amount of corneal stroma to flatten the cornea
• It Prevents complication related to stromal flap.

6. Intra-corneal Ring Implantation (ICR):

• Ring implanted in 2/3 stromal depth cause cornea flatten.
• It can correct upto 12D

II. Lenticular Based:

1. Extraction of Clear Crystalline lens:

• Remove the crystalline lens and an artificial Intra Ocular Lens (IOL) is implanted
• It's a reversible procedure and can correct upto 16-20D

III. Others:

Phakic Intaocualr Lens:

• Implantable collamer lens (ICL) is implanted in the anterior chamber and posterior chamber anterior to crystalline lens.

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