Corneal Allogenic Intrastromal
Ring Segment (CAIRS) combined
with Contact Lens-Assisted
Corneal Cross-Linking (CACXL)
for a patient with keratoconus:
Slit lamp picture showing
intrastromal segments together
with excellent improvement in
topography and other parameters seen
In no field other than ophthalmology must there be such constant and rapid explosion of new innovations and technology holding the potential for dramatic change. The eye being an organ that is easy to evaluate subjectively and providing the access required to assess objectively, its various parts lends to it the enviable position of being among the front runners as far as new innovations and technology is concerned.
Machine driven: Newer fluidics such as Active Fluidics (Alcon Centurion Vision System), Fusion Fluidics (AMO Whitestar Signature System) and Adaptive Fluidics (B&L Stellaris Elite) have all but removed surge and made chamber stability a reality. Together with power modulations, newer probe designs and better foot-pedal controls, these increase the safety, ease and speed of cataract surgery.
Hypersonic vitrectomy (Vitesse, B+L), with a cut rate of 1.7 million cpm, can liquefy and aspirate vitreous. Therefore, in case of a posterior capsular rent, one need not change probes but can continue on with vitrectomy, switching safely and seamlessly between phacoemulsification and vitreous cutting. YAG nanolasers use less energy and cause less endothelial damage than conventional phaco and can also remove the laminin layer from the capsule to prevent capsular opacification.
Lasers: Improvements in femtosecond laser-assisted cataract surgery (FLACS) include more precise cuts, better sealing reverse geometry side cuts, topographic integration, iris registration and capsular nubs for astigmatism management via incisions and toric IOLs as well as wireless integration for better workflow. The Zepto capsulotomy system (Mynosys) and the CapsuLaser (Excel-Lens) are accurate rhexis systems that give a stronger rim because of hardened edges. Laser capsulotomies prevent asymmetric capsular contraction and IOL tilt secondary to asymmetric rhexis and can even make possible posterior capsule capture through precise posterior capsulorhexis.
Image-guidance systems: Surgical accuracy is further increased by iris registration and intraoperative overlay technologies such as Callisto Eye (Carl Zeiss Meditec AG) or Verion (Alcon), which help rhexis sizing and centration; axis, length and optic zone size of astigmatic cuts; IOL centration with respect to pupil etc.
Intraoperative aberrometry with the ORA (Wavetec Vision) and HOLOS IntraOp (Clarity Medical Systems) help in refining decision-making in complex situations such as post-LASIK eyes, presbyopic IOLs, toric IOL alignment and placement of limbal-relaxing incisions. Integration of various technologies such as ORA and Verion through VerifEye Lynk (Alcon) helps make these user-friendly.
However, these technologies may not be as useful in routine eyes because of measurement variability. TrueVision 3D Surgical allows stereoscopic surgery, helps intraoperative alignment and allows better ergonomics by allowing the surgeon to sit up straight while operating. The intraoperative OCT is another diagnostic tool that has proven helpful.
Newer IOLs: Piggyback IOLs, toric IOLs and presbyopia-correcting IOLs are exciting innovations. The latter includes pseudoaccommodative IOLs such as multifocals, trifocals, extended depth of focus and small-aperture IOLs; partially accommodative IOLs including the single- and dual-optics IOLs as well as accommodative IOLs – both in-the-bag as well as sulcus-implanted IOLs.
Adjustable IOLs allow for postoperative adjustments in power. These include the Light Adjustable Lens (Calhoun Vision) and multi-component IOLs such as Precisight (IVO) and Harmoni (ClarVista Medical). Refractive indexing utilises femtosecond laser to create patterns in the IOL to correct myopia, hyperopia, astigmatism and higher-order aberrations. New IOL power-calculating formulae are also equally important.
Techniques: Intrascleral haptic fixation has gained traction via the glued IOL and Yamane techniques. The Jacob paperclip capsule stabilizer (Morcher GmbH) developed by the author is an effective means of achieving sutureless trans-scleral fixation of the capsular bag in subluxated cataracts and IOLs. The B-HEX Pupil Expander (Med Invent Devices), HumanOptics artificial iris implant and the various MIGS devices are other useful innovations.
Dropless cataract surgery with intra-cameral, intra-canalicular or punctal plug-based therapeutic sustained-release drug delivery system is another advance to look forward to.
Preoperative Diagnostics: Newer devices such as the Pentacam AXL provide complete data including axial length and anterior and posterior corneal data and is helpful for toric IOL power calculation with greater accuracy. Angle alpha and kappa measurements are provided, which are useful for both refractive and premium IOL decision-making.
Investigations for the ocular surface such as tear osmolarity, MMP-9 and other inflammatory markers as well as new treatment modalities such as the LipiFlow Thermal Pulsation system are useful.
Small-incision lenticule extraction (SMILE): With lack of a flap, less incidence of flap-related complications, better retention of biomechanical strength, less dry eye, better and faster recovery of corneal sensation as well as proven predictability, efficacy and safety, SMILE® is establishing itself as a superior means of refractive correction, gaining popularity with both surgeons and patients. Less dependence on external influences such as room temperature and humidity, corneal hydration and other factors together with faster workflow are added advantages over LASIK.
Disadvantages at present, however, include lack of cyclotorsional adjustment and hyperopia treatment.
Presbyopia-correcting alternatives: Other than presbyopia-correcting IOLs, synthetic corneal inlays, multifocal LASIK (presbyLASIK), femtosecond laser-assisted intracorneal ring pattern application (IntraCor) and scleral implants, new entrants include electrostimulation of the ciliary muscle, pharmacological approaches in the form of presbyopia correcting eye drops and PEARL (PrEsbyopic Allogenic Refractive Lenticule) – a SMILE lenticule-based procedure developed by the author.
Refractive correction of keratoconus: This has received plenty of focus recently, with a goal of providing better quality of vision in keratoconic patients. Phakic toric implants in younger and toric IOLs in older patients as well as topography-guided excimer laser smoothening with corneal cross-linking and topography-guided differential cross-linking are some advances.
Two new techniques pioneered by the author – Corneal Allogenic Intrastromal Ring Segments (CAIRS) and Contact Lens-Assisted CXL (CACXL) – provide good refractive improvement and stabilisation even in thin keratoconic corneas. CAIRS behave like Intacs but avoid all complications associated with implantation of synthetic material within the cornea as it is prepared from donor corneal tissue.
Diagnostics: There has been tremendous improvement in diagnostics with better topographic abilities, posterior corneal evaluation, aberrometry, very high-frequency digital ultrasound or OCT-aided epithelial mapping, laser interferometry, OCT, corneal biomechanical analysis using new machines and new indices as well as the concept of Percentage Tissue Altered (PTA) are exciting new advances and concepts.
Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India and can be reached at email@example.com.