Highlights of The Annual Meeting of The United Kingdom and Ireland Society of Cataract and Refractive Surgery

by Gerry Harnisch

The United Kingdom and Ireland Society of Cataract and Refractive Surgeons (UKISCRS) convened its annual conference recently in Chester, UK. Presenters discussed numerous clinical topics including the use of disposable instrumentation in laser photolysis, sutureless synthetic keratophakia with intracorneal lenses and erbium laser phacoemulsification.

Disposable Instrumentation in Laser Photolysis Increases Safety
Dodick laser photolysis using disposable hand piece aspiration is suitable for soft to medium cataracts and the next generation of intraocular lenses. This approach reduces the cost and enhances the safety of small incision cataract surgery, reported Clive Peckar, MD, of the Department of Ophthalmology, Warrington Hospital, Warrington, UK.
Dodick laser photolysis utilises a Neodymium YAG pulse with a wavelength of 1064 nanometres and a duration of seven nanoseconds. Low energy application transmits seven millijoules per pulse while high-energy application transmits ten millijoules per pulse. Each hand piece delivers a total of 1500 laser pulses at a frequency of 1-20 per second. The system has a plasma screen display and uses a micron quartz laser fibre with a 1mm tip that does not require cooling. A 0.9mm tip is in development.

"All laser approaches to cataract surgery today produce no clinically significant heat. This allows us to split infusion from the emulsifying needle and remove cataracts through two paracentesis type small incisions," commented Dr. Peckar.
Dodick laser photolysis allows small incisions of 1.0 mm or less to pursue endocapsular cataract surgery and increases the safety of cataract surgery. It also utilises more ergonometric and reliable probes while reducing the cost of small incision cataract surgery, he noted, adding:

"The use of a completely disposable lightweight handpiece and fibre for small incision cataract surgery is of great interest in the current environment surrounding Creutzfeldt-Jakob Disease."

Sutureless Synthetic Keratophakia Effective in Hyperopia
The PermaVision® intracorneal lens (Anamed Inc.) for correcting hyperopia for refractive errors up to +6.0 dioptres produces large effective optical zones according to Sheraz Daya, MD, Centre for Sight, Queen Victoria Hospital, East Grinstead, UK
Dr. Daya presented data from five eyes in four patients who were enrolled in a long term, multicentre, multinational clinical study of PermaVision® lenses in hyperopia from +1.5 to +6.0 dioptres. All five eyes showed "dramatic" improvement in the convex spherical lens prescription and in visual acuity at one month following the keratophakia procedure, he said.

Decentration occurred in two eyes a week after surgery. In one eye this required removal of the lens eight weeks following the procedure.

"The issue of decentration can be solved by using a smaller lens, changing the orientation of the lens or modifying the operating regimen," said Dr. Daya. The problem of incorrect orientation of the lens can also be addressed by the use of a new delivery device that has recently become available, he added.
The problem of transient haze can be solved by ensuring that there is a pristine interface between the lens and the cornea, making certain that the orientation of the lens is correct and ensuring that the lenses are designed with thin edges to prevent the formation of cellular deposits, he noted.

Mastering the IOL Master
Careful use of the IOL Master, a non-contact optical interferometer designed to measure the axial length of the eye, produces reproducible measurements with a minimum of effort, reported by Marie Restori, MD, Moorfields Eye Hospital, London, UK.

The IOL Master system also incorporates devices for measuring the anterior chamber depth and corneal curvature. It includes software that permits calculations of lens implant power using a selection of formulae.
"IOL Master enables reproducible measurements with minimum skill. The system easily measures eyes with posterior staphylomata, pseudophakia, non-macular fixation and nystagmus as well as eyes filled with silicone oil," she said.

For eyes with non-standard proportions, Dr. Restori suggested the use of a formula that includes the pre-operative anterior chamber depth. Limitations of the system include measurements in eyes with dense cataracts or other ocular opacity, central lens opacities and gross astigmatism as well as the assessment of the anterior chamber depth in pseudophakic or aphakic eyes, she noted.

Proper care in the pre-operative stage can help minimize mistakes with the IOL Master, she emphasized. She presented two cases of errors she had encountered. In the first case, a glaucoma patient who had undergone cataract surgery and implantation of an intraocular lens was found to have a post-operative refractive error of - 4.0 dioptres.

Repeat IOL Master measurements were found to be correct but the anterior chamber depth was shallower following surgery compared with that before the operation.
"The intraocular lens was exchanged as the lens haptic was shown to be bent, thereby pushing the iris forward," explained Dr. Restori.

In the second case, the patient was found to have a post-operative refractive error of - 9.0 dioptres while the target was - 2.0 dioptres. Repeat IOL Master measurements were found to be correct but the explanted lens was shown to have been incorrectly labeled as 17.5 dioptres instead of 27.0 dioptres.

Incremental Improvements with Erbium Laser Phaco
Although there have been no major breakthroughs in the last two years in
erbium laser phacoemulsification, subtle improvements continue to come along, reported Dr Norbert Körber of the Outpatient Eye Surgery Centre, Köln, Germany.

"More flexible laser fibres and hand pieces with better ergonomics are now available. In addition, the advent of three port laser phaco allows better micro incisions, excellent mobility of the laser probe in the anterior chamber and the option to implant an intraocular lens via a microcartridge, although it does not shorten nucleus ablation times," he noted.

Dr Körber presented data showing that erbium laser phacoemulsification utilises substantially lower applications of energy compared with ultrasound laser phaco. In a series of 669 eyes with a nuclear hardness of grades 0-IV inclusive, a mean energy application of 0.9 to 331.6 joules was required with erbium laser phaco. In contrast, a mean energy application of 26.7 to 10,757 joules was required for ultrasound laser phaco in 232 eyes with the same range of nuclear hardness, he said.

Erbium laser phaco also involves a lower loss of corneal endothelial cells compared with ultrasound laser phaco, Dr. Körber reported. He cited an international prospective study by Franchini in 1999 that included 35 eyes and involved measuring the corneal endothelial cell count both pre-operatively and 4 months post-operatively. The corneal endothelial cell loss was 5.15% with erbium laser phaco and 6.19% with ultrasound laser phaco. Another study by Höh in 1997 showed a corneal endothelial cell loss of 1% and 12% with erbium laser phaco and ultrasound laser phaco respectively, he noted.

Erbium laser phaco also has some disadvantages. These include reduced manipulative dexterity in handling of the instrument due to the utilisation of a very rigid laser fibre. Erbium laser phaco also requires a greater nucleus ablation time than ultrasound laser phaco and this renders the former technique unsafe for a nuclear hardness of grade IV, he noted.