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IN a few short years, the EPCO 2000 software program has become an essential tool for researchers looking at the influence of IOL edge design and other factors on the development of posterior chamber opacification (PCO).

German ophthalmic surgeons Manfred Tetz MD and Christophe Nimsgern MD designed the Windows-based program to provide quantitative analysis of digitised retro-illumination slit-lamp photographs. The program allows the user to mark and score opacified areas behind the IOL.

Dr Tetz presented a clinical study during the annual meeting of the American Society of Cataract and Refractive Surgery in which the program played an important role. The prospective, randomised, multicentre trial considered the influence of IOL design on the development of PCO.

The study compared the incidence of PCO after 12 months in two IOLs - the single-piece Acrysof SA30AL and the multi-piece MA30BA. Researchers used the EPCO 2000 program to analyse images acquired from 41 patients at three, six and 12 months.
At one year, both IOL types showed low levels of PCO growth, with a mean total PCO score of 10.7%. The single piece IOL had the lower score at 6.6%, compared with 13.3% for the multi-piece IOL.

“The results suggest that small variations in IOL design can have an early postoperative impact on PCO development,” Dr Tetz noted.
The EPCO 2000 analysis failed to uncover a negative effect associated with the bulky haptic of the one-piece IOL. Such an effect had been predicted by Japanese researcher Okihiro Nishi MD in a recent publication.
A recent study by Gerd Auffarth MD and colleagues (Ophthalmology 2003; 110:772-780) used the EPCO 2000 programme to compare PCO rates in a prospective comparison of round and sharp edged IOLs.

They compared outcomes in 121 eyes of 121 patients who received one of six IOLs - Corneal ACR6, Alcon Acrysof, Allergan AR40, Pharmacia 811 one-piece PMMA lens and Pharmacia 911A silicone IOL. The mean follow-up period was 14 months.
The researchers used the program to evaluate the morphology of PCO in the entire optic and 3.0mm central area in each case. The program revealed that the highest PCO rates occurred with round-edge designs such as the Corneal ACR6 and the Allergan AR40. PCO rates were significantly lower for the sharp-edged Alcon and Pharmacia IOLs.

The initial analysis indicated that the Alcon IOLs appeared to have more PCO when the capsulorhexis rim was not covering the optic edge. Accordingly, the researchers conducted another study of 53 eyes of 46 patients who had received Alcon Acrysof IOLs. With nearly three years of follow-up, the researchers noted a statistically significant negative correlation between PCO and overlapping of the rim.

“The sharp edge IOL types (Alcon Acrysof and Pharmacia 911A) resulted in significantly lower PCO values. We saw no significant difference between the two sharp edge IOLs. The analysis revealed that overlapping of capsulorhexis rim and anterior IOL optic surface by more than 20% resulted in significantly lower PCO values with the Acrysof IOL,” the researchers note.

The EPCO 2000 system is not the only method available for PCO analysis, but it may be the most accurate and easy to use, another recent study suggests (Aslam et al BJO 2002; 86:1181-1186).
Scottish researchers recently compared different systems now in use for the analysis of PCO.

Analysis of PCO
“Accurate PCO analysis is important for measuring the effect of treatments that aim to reduce PCO such as intraoperative pharmaceutical treatments or varying types of surgery. It is also an important tool for comparing rates of PCO between many available lenses and the rates of progression with lenses over time,” the researchers say.
Current systems available for measuring PCO range from simple slit lamp analysis and subjective grading to more complex computerised methods of analysis. The optimal system should quantify PCO objectively, with results that correlate well with changes in vision.

The ideal system should be sensitive enough to pick up small difference in PCO progression, yet specific enough to compensate for artefacts such as lens edge.
Visual acuity testing and keeping track of the incidence of YAG surgery required after cataract surgery are two methods that provide some idea of postoperative PCO development. However, visual acuity can be affected by many factors other than PCO. The YAG-surgery metric is useful, but is subject to many secondary factors such as economics and practice patterns of specific surgeons.

Subjective slit lamp grading of PCO, typically on a 0-3 scale, is still widely used. However, that approach is not quantitative and is subject to observer bias. It also does not lend itself well to following progression of PCO over time, the researchers note.
The Scheimpflug system is a far more high-tech approach. The system utilises the EAS-1000 anterior eye segment analysis system (Nidek), equipped to perform densitometry and light scattering intensity. That system has been shown to be efficient and reliable. However, this approach requires equipment that is not readily available in many ophthalmology departments.

The EPCO 2000 digital photo acquisition system, in contrast, only requires equipment that is typically available in any ophthalmology department. The images can be acquired at a slit lamp equipped with a digital camera, or scanned from film if necessary. The system offers rapid access to the images with minimal observer bias. It has shown itself capable of detecting and following early PCO progression

Merging
A newer feature of the EPCO 2000 system allows merging of two images of the same capsule, with illumination reflections in opposite halves of the image. Merging the two images removes any reflective aberrations.
The Scottish team comments that EPCO 2000 has become “the new standard benchmark system for comparison of PCO rates”.

“After several years of hard work and improvements to the software itself, it is a very satisfying feeling to see EPCO2000 spreading all over the world. It is now in use throughout Europe, Asia and the United States. A number of independent research groups have evaluated the programme and confirmed its reliability,” Christophe Nimsgern MD, one of the developers of the system, told EuroTimes.

He noted that an update to the current version of EPCO 2000 is in the works. The main functions will remain more or less the same, while the usability and stability of the program will be optimised. More information is available online at www.epco2000.de.

Manfred Tetz MD
Universitats-Augenklinik Charite, Berlin, Germany
Email: mtetz@charite.de

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