Features

She described how accommodative esotropias can be treated successfully with refractive surgery. Aniseikonia cannot be predicted and contact lens trials should be considered for high anisometropes.

Cyclotorsion in high astigmats is also often found postoperatively. Refraction and topographical mapping both monocularly and binocularly can help prevent these errors. Problems with manifest squints, including microtropia, can be avoided by preventing change in ocular dominance. Density of suppression and size of suppression scotoma should also be considered. For problems with incomitancy, Finlay suggests avoiding swapping fixation.

Finally, don’t assume patients are orthophoric. Ensure preoperative refraction does not have refractive control of phoria or prescribed prisms. She would recommend a full orthoptic examination if the patient has history of eye exercises, strabismus surgery, amblyopia therapy or prisms.

Intacs are indicated for patients with clear central corneas who are contact lens intolerant. They are not indicated for corneas under 450µm or over 55D steep. Intacs, as a rule, are inserted into the anterior stroma through a narrow temporal channel incision. Depending on the clinical situation, one or more rings may be used, but it is most typical to use a ring inferiorly, giving a supportive effect. In his study of 100 eyes, 70 per cent showed improved visual outcome, and the majority remained stable for two years postoperatively. It is also possible to combine Intacs with other refractive procedures to improve vision once the patient is stable.

The Law

In one third of these, the claimant had particular risk factors, for which especially careful counselling was warranted. Other cases included claims where there were clear contraindications to surgery (29 per cent), cases where there was surgical error (24 per cent), avoidable delay in instituting medical management for postoperative complications (23 per cent) and a small proportion of cases were precipitated by a second opinion where the clinician giving the opinion was not fully conversant with the facts (4 per cent).

Bailey concluded by saying that the number of claims could be substantially reduced by:

The Artemis means that flap thickness can truly be analysed post-Lasik, and residual stromal bed accurately predicted, meaning safer outcomes for patients.

Screening for ectasia

Professor Colin delivered a talk on post-Lasik ectasia which occurs in anything between one in 10,000 and one in 300 cases, the lower rate for centres where careful screening is carried out and the higher figure where ‘anyone is suitable’.

Treatment options for kerectasia now include Intacs as well as the more conventional refractive corrections and corneal transplants, including lamellar and full thickness grafts. This was followed by a much anticipated and exciting debate on the femtosecond laser microkeratome versus the mechanical microkeratome.

Ventor argued that mechanical microkeratomes caused abrasions, hydrated interfaces, problems with button hole and inconsistent flap dimensions.

With the Intralase there is a smooth plane. The tissue cutting is non-thermal and the flap can be designed in terms of flap direction, hinge angle, position and thickness. Centration can also be changed, and there is standardisation of flap thickness. Induction of root mean square of higher order aberrations was 0.7 with the Hansotome, but only 0.3 with the Intralase. Ventor acknowledged that there were some new complications, however, with the Intralase, such as difficulty uplifting the flap, bubbles under the flap, opacities and keratitis. However, he concluded that its versatility, predictability and stability indicated that it is the microkeratome of the future.

Gartry focused on the long history and evolution of mechanical microkeratomes, claiming that like must be compared with like and the Intralase should only be compared with the most modern design of mechanical keratome. He then focused on the lengthy time it takes to create a flap using the femtosecond, three minutes 10 seconds compared with 30 seconds for the microkeratome. This creates a greater risk of suction loss in addition to other problems. A 13 per cent incidence of DLK with the Intralase has been reported

Other complications include extreme photophobia requiring steroids and gas bubble escape into the anterior chamber. Gartry also argued that with modern microkeratomes, flap thickness was equally predictable. A planned 120µm flap gave a mean of 111µm in 34 cases using the Bausch & Lomb XP, whereas with the Intralase the same gave a thickness of 141.

In summary, Gartry argued that the relative cost of the Intralase was far too great, the treatment time was simply too long and there were too many new, unknown complications. The audience were then asked to vote, and on this time the mechanical microkeratome won.

In the periphery of the cornea, loss of ablation efficiency may form a component of the induction of spherical aberration, but this does not explain the difference in response between surface ablations and Lasik. Furthermore, the artefact in IOP measurement induced by refractive surgery has been assumed to result from a decrease in curvature and thickness during myopic procedures. Clinical evidence points to the fundamental change in biomechanical properties of the cornea with an ablative procedure.

Finally, Dr Roberts mentioned that the ability to measure properties preoperatively offers the possibility to predict the biomechanical response and potentially compensate for it, leading to potential biomechanical customisation in the next generation of refractive surgery.

Contact Lenses

Bloom described the variety of lenses now available. Interestingly, even documenting the uses of silicone hydrogel lenses in reverse as an OK lens, an effect that was found quite by mistake. The importance of thorough topography readings and interpretation was demonstrated. Bloom stressed that OK is a time-consuming method of contact lens correction but can be extremely rewarding for the practitioner.

However, for the majority of patients, post-refractive surgery lens fitting is not so challenging, and may be used simply to balance an intended monovision correction for night driving for example.

Liu closed the meeting and delegates departed homewards loaded with much thought-provoking information.