Refractive surprise

1. Refractive surprise

2. CASE PRESENTATION
Ramadan Elgohary
Ophthalmology resident
Al Azhar university hospitals

3. Case presentation
•History of Present Illness: A 59-year-old male patient
presented with poor vision at far but good vision at near
one month following uncomplicated cataract surgery OD.
•Chief Complaint: Blurry vision in the right eye (OD)
following cataract surgery.
•Medical History:
•
Benign prostatic hypertrophy
•
Chronic obstructive pulmonary disease
•
Low back pain
•
Hyperlipidemia

4. Case presentation
•Past Ocular History:
• Uncomplicated cataract surgery OD for posterior
subcapsular cataract with target at plano.
•Medications:
•
Indomethacin
•
History of Flomax (tamsulosin) use for
approximately two months prior.
•Allergies: No known drug allergies.

5. Case presentation
•Ocular Exam:
•Visual Acuity, with best correction:
o OD: o.o5 with PH improvement to 0.4
o OS: 0.7 with PH improvement to 0.9
•Manifest Refraction
o OD: -5.75/-1.25x170 0.8→
o OS: -0. 5 sph → 0.9
•Intraocular Pressure 16 mm Hg OU
•Pupils: No RAPD.
•Motility: Full OU.
•Anterior segment exam:
o OD: well positioned PC IOL with no capsular block
o OS:. Lens with trace nuclear sclerosis.
•Dilated fundus exam (DFE):
o C/D: 0.3 OU, healthy nerves. Macula, vasculature and periphery normal OU.

6. Case presentation
•The patient was noted to have significant cataract in the right
eye and had cataract surgery OD a few weeks ago.
•His cataract surgery OD was uncomplicated. The IOL was
placed in the bag.
• He presented for his one month post-operative visit
complaining of blurry far vision.
•The posterior chamber lens was centered and clear, there was
no evidence of capsular block or sulcus placement of the IOL
which could have lead to a myopic shift.
•He had no evidence of cystoid macular edema which could
lead to a hyperopic shift.
•This guide us to a review of the lens calculations

7. Case presentation

8. Case presentation
•The axial eye length measurements used for the lens
calculations were taken from an A-scan that was done
preoperatively.
•Measurements of the right eye are very irregular and
range from 22.30 to 24.52.
• These variable values were averaged to generate the
axial eye length of 22.90 mm OD.

9. Case presentation

10. How to manage???
• Glasses.
• Contact lens.
• IOL exchange.
• Piggyback IOL.
• Corneal refractive surgery.

11. Why The Surprise?
• Correct patient / Correct lens
• Long or short eye
• Proper IOL formula
• Data inserted correctly
• Previous refractive surgery

12. Source of error????
• Errors are possible in contact biometry due to the excess
indentation of the cornea (compression of 0.5 mm can
cause error of −1.25D.).
• Off‑axis measurement, if the probe is not perpendicular
also causes errors (0.5 mm off axis gives +1.25 D error).
• Always measure both eyes and repeat if axial length
difference between two eyes is >0.3 mm or if
consecutive measurements differ by more than 0.2 mm.

13. optical biometry
• Operator independent as it is noncontact.
• No risk of transmission of infections between
patients
• Rapid and ease of use.
• IOL Master 1999,
• lenstar 2008
• Disadvantages of optical biometry devices:
Axial length measurements are not possible in
mature or dense subcapsular cataracts

14. optical biometry

15. optical biometry
• Differences between IOL Master and lenstar[1]
• ACD: Lenstar measures ACD from corneal
endothelium to anterior lens surface while IOL
Master measures it from corneal epithelium to
anterior lens surface.
• Lenstar measures more parameters such as CCT,
retinal thickness, and pupil size/centricity
• Lenstar takes twice as much time as IOL Master
for measurements.

16. Which formulae to use??
• Axial length (mm) Formula used
<20 Holladay II
20-22 Hoffer Q
22-24.5 SRK/T, Hoffer Q, Holladay average
24.5-26 Holladay I

17. Treatment option for refractive surprise?

18. lens‑based procedures
• (piggyback IOL and IOL exchange)
• Indications and advantages
• Correction of large residual refractive spherical errors
• Lens‑based procedures do not change the corneal
refractive power as they do not alter the corneal surface
• The original cataract wound can be reopened and used
to implant the IOL soon after initial surgery
• Useful for surgeons who do not have an excimer laser in
their hospital.

19. IOL exchange
• If the IOL to be removed is foldable, it can be removed
after cutting or unfolding it through 2.8–3 mm incision.[
• It is preferable to do IOL exchange early within 2 weeks
before the capsular bag has fibrosed.

20. IOL exchange
risks associated with explantation

21. Piggyback IOL
• Piggyback technique involves the implantation of the
second IOL in the posterior chamber (sulcus), over the
first IOL (in the bag).
• It is an easier procedure than IOL exchange,especially if
the capsular bag has fibrosed as the risks associated
with explantation are avoided.

22. Piggyback IOL
One of the simplest formulas to calculate for piggyback IOL
is:
•Postoperative myopia = spherical equivalent (sphere +half cylinder)
•Postoperative hyperopia = spherical equivalent × 1.5
•Complications:
Interface membrane can develop between the two
IOLs.
Treatment involves a surgical wash or YAG).

23. Corneal Based Laser Refractive Surgery‑
• Advantages
• Avoids additional intraocular surgical procedures
• Better accuracy especially for the correction of residual cylinders
• A recent study using LASIK to correct residual
refractive error after cataract surgery found 92.85%
eyes achieved a final spherical equivalent within ±
0.5D and 100% eyes within ± 1D.
• LASIK is easier in eyes with previous YAG
capsulotomy done; where lens exchange is risky
and difficult.

24. Corneal Based Laser Refractive Surgery‑
Limitations of laser in situ keratomileusis
• Correction of high residual refractive
errors will depend on corneal thickness
• Availability of excimer laser with the
cataract surgeon
• Higher cost.

25. Corneal Based Laser Refractive Surgery‑
• How Long Do You Wait?
• • PRK can be done anytime
• • LASIK – When is the incision stable?
• – Nobody knows for sure
• – Marked elevation in IOP from microkeratome
• – Wait at least 6 weeks and probably 3 months
• – If unacceptable to patient then PRK

26. TAKE HOME MASSAGE
• LASIK is the most accurate procedure to correct residual refractive
error after cataract surgery.
• Lens based procedures, such as IOL exchange or piggyback lens‑
implantation, are also possible alternatives in cases with extreme
ametropia, corneal abnormalities, or in situations where excimer
laser is not available.
• Piggyback IOL is a safer and more accurate method than IOL
exchange