Intraocular lenses (IOLs) are used to restore vision after cataract surgery by replacing the crystalline lens. Sir Harold Ridley first proposed using acrylic plastic lenses for cataracts after observing aircraft plastic fragments in soldiers' eyes did not trigger rejection. IOLs are either single or multi-piece, made of acrylic or silicone, and placed in the anterior or posterior chamber of the eye. Their power is calculated using the SRK formula based on axial length and corneal curvature. Complications can include posterior capsular opacification, calcification, and degradation.

1. IOL

2. WHY ?

3. • Crystalline lens contributes approximately +15 to +20
diopters (D) to refractive power of human eye
• A further 43 diopters is provided by the cornea

4. • To restore refractive power of a normal clear lens after
removal of an opacified crystalline lens in cataract surgery

5. HOW ?

6. A pair of thick spectacles

7. Contact lenses

8. Intraocular Lens implant

9. History / Mystery
• During World War II, Sir Harold Ridley, an ophthalmologist
in London,
 saw Royal Air Force casualties with eye injuries
 observed that splinters of acrylic plastic from aircraft
cockpit canopies became lodged in their eyes did not
trigger inflammatory rejection as did glass splinters.
 led him to propose the use of artificial lenses made of
polymethyl methacrylate - PMMA to treat cataracts
• Polymethyl methacrylate (PMMA) lenses were the first
lenses to be used in the human eye (in 1949)

10. Terminologies
• Phakic eye - An eye with a natural crystalline lens
• Pseudophakic eye - without a natural crystalline lens but
with an IOL
• chromophores - UV absorbing compounds, important
element of the IOL optic component.
 protect retina from UV radiation in the 300-400 nm
range, a feature normally provided by the normal
crystalline lens
• Optic - central part overlying the optic axis
• Haptics - peripheral arms used for placement & stabilization

11. Flash quiz
Aphakic eye ?

12. IOL materials
Acrylic lenses Silicone lenses
Composition Acrylic acid Polyorganosilone
Flexibility Foldable, Non foldable All foldable
Refractive index Usually higher Usually lower
Lens thickness Thinner Thicker

13. Lens
Acrylic
Foldable
Hydrophilic Hydrophobic
Rigid
-PMMA
Silicone

15. IOL designs
• According to fixation site, IOLs may be implanted in
anterior or posterior chamber of the eye.
• Anterior chamber lenses placed in anterior chamber angle or
fixated to the iris.
• Posterior chamber lenses fixated within the capsular bag or
the ciliary sulcus
• Usually posterior chamber intraocular lens have a 10°
anterior angulation to keep the optic away from the pupil
• Anterior chamber lenses have posteriorly angulated haptics
to vault the intraocular lens away from pupil

18. IOL designs
IOLs can also be described as
• single-piece (entire lens manufactured from same material)
OR
• multi-piece (generally described as 3-piece lenses, optic lens
from one source and the loops manufactured from a different
material)

19. Intraocular lens optic may be
• monofocal
• multifocal
• toric
• accommodative

20. Flash quiz

21. SRK formula
Power of intraocular lens to be implanted calculated by modified
Sanders–Retzlaff–Kraff (SRK) formula

22. SRK formula
where
• P = power of IOL
• A = constant which is specific for each lens type
• L = axial length of eyeball in mm
determined by A-scan ultrasonography.
• K = average corneal curvature
determined by keratometry
P = A – 2.5L – 0.9K

23. Complications of IOL
• Initial IOLs had complications like uveitis, glaucoma,
hyphema.
• Posterior capsular opacification
 hydrophilic IOLs
 involve the use of intracameral gas
• Calcification
 Silicone lens
 presence of asteroid hyalosis (Ca deposits in vitreous)
• Snow flake degeneration
 PMMA lens
 PMMA degradation slowly by long term UV exposure

26. Flash quiz

32. References
• https://www.ncbi.nlm.nih.gov/books/NBK481726/
• AK Khurana. Comprehensive Ophthalmology.
• Parsons' Diseases of the Eye

33. THANK YOU !