Ask The Experts
Dr Lampros Lamprogiannis asks for a step-by-step approach to phacoemulsification in high hyperopes.
Lampros Lamprogiannis, Fellow in Ophthalmology, Epsom and St Helier University Hospitals, London, UK.
Can you describe your step-by-step approach to phacoemulsification in high hyperopes?
Cyres K Mehta
Surgical Director and Chief, International Eye Centre, Mumbai, India
Phacoemulsification in small eyes, with short axial lengths less than 22mm and accompanying hyperopia of 3.00D or more, present a unique set of challenges. The anterior chamber (AC) can be quite shallow. Here, cataract formation can cause the lens to swell and further occlude the angles. Intraocular lens (IOL) power calculation is performed on the IOLMaster® 700 (Zeiss), using both the Haigis suite and the Hoffer Q formulas which are more accurate in short eyes.
Make sure to measure intraocular pressure (IOP) on the table, as dilation of the pupil frequently leads to elevated IOP. Here we can pretreat with 100cc 20% Mannitol, fast IV in five minutes, wait for 30 minutes and then start the case when IOP is controlled.
Make sure your tunnels are long enough to prevent iris prolapse. Use high molecular weight dispersive viscoelastic e.g Viscoat, to give you adequate space in the AC, remembering that in a shallower AC the phaco tip is likely to be closer to the endothelium.
If you cannot get enough space in the AC, a simple technique is to do a small 25/27G transconjunctival vitrectomy at a high cut rate for just a few seconds, which will lead to the chamber deepening substantially.
Once adequate AC depth is achieved, we proceed with regular phaco using the ‘lens salute’ technique and torsional phaco in ultrashort pulses.
Noel Alpins AM
The risk of small incision cataract surgery and phacoemulsification in high hyperopia is mainly related to the small size of the eye and reduced space in the AC for the safe removal of the lens.
In the planning of the lens power, whatever formula is normally applied, additional weight should be given to the value obtained with the Hoffer formula, which has greater accuracy in shorter axial lengths.
Also preoperatively, to obtain a soft eye and greater compliance of the AC to ‘expand’ with fluid irrigation, then 350-500ml of Mannitol 20% should be administered IV starting 60 minutes prior to the procedure. Also, a Honan balloon should be applied at 35mm for six minutes to reduce intraocular volume and avoid the complication of high IOP occurring with shallow or flat AC during surgery.
With this preparation, normal phaco parameters can be applied, which for sculpting is a 50% torsional power 55mm, IOP and vacuum 85mmHg, flow 22cm/minute with an effective bottle height of 75cm, which may be increased by 5-10cm if needed.
A 2.2mm diamond blade incision is made in clear corneas, but sometimes this may need to be enlarged at the time of implant insertion because of the thickness of the foldable lens. Care is taken with the hydrodissection to avoid forward prolapse of the nucleus or over-hydration.
Using a technique of mini-chop after a central gutter, ultrasound time would average at a CDE time of seven seconds. Removal of viscoelastic should be complete. The incision is sealed by insufflation and seal confirmed with fluorescein.
Consultant Ophthalmologist, Vista Vision Centre, Verona, Italy
1. Preoperative evaluation is the most important step for success.
Anterior chamber depth (ACD) is particularly important. If less than 2mm, the eye probably is affected by angle-closure glaucoma, while if it is more than 2mm, there is usually no risk for glaucoma and mydriasis will be wider and safe.
Shallow chambers are an indication for femtosecond laser capsulotomy, as forceps capsulorhexis requires some additional room and heavy viscoelastic injection. ACD will also affect IOL power calculation, and IOL powers in excess of 50D may be expected in high hyperopes with deep AC.
In addition, the risk for choroidal thickening/haemorrhage suggests general anaesthesia in older patients. I avoid local anaesthesia in these eyes, because of the possible induction of positive posterior pressure.
2. IOP during lens removal should be strictly controlled.
High hyperopes benefit from forced infusion, both with fluid and with vacuum pumps. However, an excessive pressure might force some fluid into the vitreous cavity through the zonules, eventually causing AC shallowing with impossible IOL insertion. For this reason a feedback system like that implemented in recent machines is particularly helpful.
3. IOL selection.
The selected IOL should be easy to implant through small pupils/capsulotomies. Rigid hydrophobic lenses may not be the best option. Multifocal IOLs in the presence of a large angle Kappa should be avoided.