Ophthalmology Lectures: PTK is one of the theraputic modalities of the cornea ..what is it ? indication & complication..

1. Excimer Laser
Phototherapeutic
Keratectomy
(PTK)
Dr.Diyar j.k.

2. PatientSelection

3. Is that cornea would be a good candidate
• The best candidates for excimer laser PTK are eyes
with anterior corneal pathology (top 10−15%) and
certain elevated lesions
• 2 question to ask ..
• How much of theeye problem is due to the cornea ?
• A second question to address is whether a PTK
procedure is the best one to attempt to improve the
situation …?

4. C/I
• eyes with deep corneal pathology in which removal of
greater than 20– 30% of the corneal thickness would
be required to clear the bulk of the opacity.
• eyes with areas of significant corneal thinning in the
ablation zone are not good candidates for PTK

5. Is that eye would be a good candidate
• the eye is likely to heal well after PTK .. ?
• Uncontrolled ocular disease such as uveitis,
blepharitis or severe dry eyes and any condition
thought to adversely affect corneal healing

6. Is that body would be a good candidate
 uncontrolled DM, an immunocompromised host,
Patients with collagen vascular disorders may
have difficulty with healing of the corneal surface.
 Patients with immune deficiencies, whether from a
systemic disease or systemic immunomodulating
medications, may be at increased risk of infection

7. patient's goals & Expectation
• Patients should be given appropriate expectations
regarding the PTK procedure, postoperative
management and clinical outcomes, including thefact
thatmany conditions treated with PTK (e.g. corneal
dystrophies) will recur with time
• surgeon’s goal of PTK is typically a smoother, more
regular cornea, but not necessarily crystal clarity

8. • A complete ophthalmologic examination.
• The size, depth, density and location of the corneal
pathology shouldbe determined in addition to the
corneal thickness in that area.
• Checking visual acuit with a hard contact lens over-
refraction can help determine whether poor vision is
due primarily to corneal irregularity or primarily to
opacity

9. Ancillary testing
• Computerized corneal topography is an excellent way
to evaluate the regularity of the corneal curvature.
Significant corneal irregularity due to superficial
pathology can severely decrease visual acuity,
• Ultrasound biomicroscopy (UBM) which uses high-
frequency ultrasound to image the anterior 4–5 mm of
the eye. It provides fairly high-definition images of the
entire cornea
• Anterior segment OCT used to obtain highly detailed
views of the entire cornea. Fourier and spectral
domain OCT, these systems will allow the
physician to determine better the depth and
density of corneal abnormalities.

11. Indication
PTK can be used to treat
two types of corneal
abnormalities: opacities
and irregularities

12. FDA-approved indications for PTK include:
(1) superficial corneal dystrophies (including granular
lattice and Reis−Bücklers dystrophies)
(2) epithelial basement membrane dystrophy and
irregular corneal surfaces (e.g. secondary to Salzmann's
nodular degeneration, keratoconus nodules or other
irregular surfaces).
(3) corneal scars and opacities (e.g. due to trauma,
surgery, infection and degeneration).

13. Masking Agent
Commonly used masking fluids are artificial tear substances.
Kornmehl et al. compared artificial tear substances of varying
viscosity with saline and a nonfluid control. solutions of
moderate viscosity yielded a smoother surface than more
viscous artificial tears, and markedly better results than the
nonviscous saline solution. All fluids outperformed the nonfluid
control. A subsequent study found good results with a
preparation of 0.25% sodium hyaluronate.

14. Techniques
Smooth opacities

15. Rough or elevated opacities

16. Recurrent erosions

17. ADVANTAGE
• Is the precision with which the excimer laser removes
tissue. One laser pulse excises approximately 0.25 µm
of tissue, or about 1/2000 of the corneal thickness
• Is the control the physician has during the surgery.
• Microkeratome and femtosecond laser generally
cannot remove very thin sheets of corneal tissue
Disadvantage
it does not discriminate between abnormal and normal
tissue. When the excimer laser is used to remove
tissue, once it has ablated the pathologic cornea,
it continues to remove normal underlying
tissue

18. Complications
• Pain
• Poor epithelial healing, Haze/scar (MMC)
• Infection
• Induced hyperopia (common),Induced myopia (less
common), Induced regular and irregular astigmatism
Decreased uncorrected and best-corrected vision.
• Recurrence of herpes simplex virus infection.
• Recurrence of the condition (especially stromal
dystrophies, Salzmann's nodular degeneration,
keratoconus nodules)
• Graft rejection/failure .

19. Antihyperopiatreatment
• Amm and Duncker reported that, of 45 patients
treated, all refractions remained stable after PTK for
recurrent erosions, whereas after treatment for
corneal scars, anterior stromal dystrophies, or
surface irregularities, 40.6% of patients developed a
hyperopic shift, 9% developed a myopic shift, and
40.6% remained stable. Deeper ablations were
associated with a greater likelihood of hyperopic
shift.

20. Other techniques
• Topography-Based
Ablations
• Femtosecond laser-
assisted phototherapeutic
keratectomy for the
treatment of dense corneal
scarring

21. Discussion
• PTK can cause ectasia..?
• Hx of PTK in cataractus patient..which formula for IOL
calculation is used..?
• “Shooting the blue” PTK for keratoconus