Important consideration for cataract surgery in keratoconus patients including preoperative, intraoperative and postoperative.

1. Cataract surgery in keratoconus
patients: Important considerations
Dr Haitham Al-Mahrouqi, BMedSc(Hons), MBChB, OMSB, ABHS
Department of Ophthalmology, Al-Nahdha Hospital

2. Financial interests
• Nil

3. Cataract in keratoconus patients
• Keratoconus patients are more prone to develop cataract/glaucoma
given the use of steroids (allergy), ICL and corneal transplants.
• No data in the literature on the true prevalence of cataract in
keratoconus patients.

4. STOP!
• Before cataract surgery is considered:
• Ensure the stability of the disease
• Assess the CDVA using RGP to eliminate the reduction in vision due to the
corneal component.

5. Problems encountered
1. Biometry
2. Intraoperative consideration
3. Which IOL
4. Post operative visual rehabilitation

6. 1. Biometry: K-readings
Anterior curvature
• In cases of irregular astigmatism, K-readings are often inaccurate.
• The sim-k should be estimated from many points on the cornea.
IOLmaster 500, 6 point
measurement of K-values

7. 1. Biometry: K-readings
Posterior curvature
• Conventional biometers including IOLmaster 500 and Lenstar 900
only estimate the total corneal power from the anterior curvature.
• Assume a constant relationship between the anterior and
posterior corneal curvature (Rpos/Rant: 82% and thus use
n=1.3375).
• In normal population, the posterior corneal curvature contributes
about 0.5D cylinder against-the-rule. However this is not the case
with keratoconus.
Douglas D. Koch, Shazia F. Ali, Mitchell P. Weikert, Mariko Shirayama, Richard Jenkins, Li Wang,Contribution of posterior corneal astigmatism to total corneal
astigmatism, Journal of Cataract & Refractive Surgery, Volume 38, Issue 12, 2012

8. 1. Biometry: K-readings
Estimated lens position
• Standard IOL calculation formulae estimate the ELP from the K-
readings.

9. 1. Biometry: K-readings
Ocular surface of keratoconus patients
• Keratoconus patients have:
• Abnormal TFBUT
• Abnormal epithelium and epithelial profile
• Lower corneal sensation
Dogru, Murat et al. Ophthalmology, Volume 110, Issue 6, 1110 - 1118

10. 1. Biometry: K-readings
Device limitations
• Poor repeatability of the devices when K-max > 55D
Hashemi H, Yekta A, Khabazkhoob M. Effect of keratoconus grades on repeatability of keratometry readings:
comparison of 5 devices. J Cataract Refract Surg. 2015;41(5):1065e1072.

11. Refractive outcome of cataract surgery in
keratoconus patients
• 92 eyes, K-readings obtained mostly using IOLmaster 500.
• Median biometry prediction error (BPE) using the actual K-readings:
• Mean K <55 = negligible (range +3 to -3)
• Mean K > 55 = 6.8D (mostly hyperopic)
If standard Ks were used in KC with Mean K >55D, BPE = 0.5D
Br J Ophthalmol. 2014 Mar;98(3):361-4

12. 1. Biometry: Practical solutions
• Ensure stability of KC
• Ocular surface rehabilitation
• Measure K-readings using scheimpflug /SS-OCT devices which
takes into account the posterior corneal curvature and incorporate
the K-readings in new formulas like Holladay II or Barret true K
formulas. Otherwise use SRK-II formula.
• Use actual K readings only if mean K < 55D, otherwise use
standard K of 43.25D. Target at least -1.5D myopia.

13. 2. Intraoperative consideration
Problems
• Due to the irregular astigmatism/scarring, visibility may be poor
during surgery.
• The surgical induced astigmatism may be unpredictable in already
weak corneas
• Wounds may be leaky

14. 2. Intraoperative consideration: Practical
solutions
• RGP lens OR viscoelastic may be used to improve visibility during
surgery
• Use scleral tunnel whenever possible. Otherwise place the main
incision superiorly away from the cone.
• Suture the main wound at the end of surgery (leave suture for 3
months!).

15. 3. Which IOL to use
Problems
• Advanced keratoconus patients have irregular astigmatism
which may not be corrected with simple spherocylindrical
lenses. Hence, problems with toric lenses
• Keratoconus patients are more likely to suffer from higher order
aberrations*. Hence, problems with multifocal/EDOF lenses
• Keratoconus patients may need corneal transplants in the
future.
*Hefner-Shahar H, Erdinest N. Highorder Aberrations in Keratoconus. Int J Kerat Ect Cor Dis 2016;5(3):128-131.

16. 3. Which IOL to use: Practical solutions
• Use monofocal lenses whenever possible
• Use toric lenses only if the astigmatism is regular in the center
of the cornea (or regularized using rings) and the patient is
unlikely to need a corneal transplant or RGP lens. A good way is
trial with astigmatic glasses.
• Avoid multifocal lenses.

17. 4. Post operative visual rehabilitation
Problems
• Refractive surprises are common in keratoconus patients
• Given the irregular astigmatism, toric IOLs may not be possible
Br J Ophthalmol. 2014 Mar;98(3):361-4

18. 4. Post operative visual rehabilitation:
Practical solutions
• Warn patients about refractive surprises
• Modalities to improve vision:
• Glasses
• RGP
• Corneal ring segments
• Refractive surgery
Avoid LRIs!

19. Thank you