Latest in refractive surgery and more highlight DOC conference

Despite world events, attendance was high at this increasingly international surgical meeting.

NUREMBERG — The 16th Annual Meeting of the German Ophthalmic Surgeons welcomed nearly 4,000 participants to this year’s International Symposium.

According to DOC president Dr. Med. Armin Scharrer, the DOC is the largest ophthalmologic conference in Europe. This year’s meeting’s attendees came from five continents and represented 52 countries. The attendance of DOC and its relevance continues to increase, Prof. Scharrer said, as the meeting has expanded from a national into an international event, featuring speakers from all over the world.

Highlights from this year’s meeting included a mix of wavefront technology, new and advanced techniques for LASIK, the latest imaging equipment, updates on other refractive procedures and more.

The following meeting coverage was first published on OSNSuperSite.com as the events took place during the DOC. Look for further updates from the meeting in future issues, and visit OSNSuperSite.com for live daily coverage of upcoming major ophthalmic meetings.

Ridley Lecture

Magnetic resonance tomography can be a helpful test for definitive diagnosis in neuro-ophthalmic conditions where functional tests alone are not enough, according to a speaker here.

“There is no doubt that that magnetic resonance tomography (MRT) has extended our ‘field of vision’ so to speak,” said Prof. Dr. med. Guntram Kommerell. “But you must also understand the limitations of this new technique.”

Prof. Kommerell, a neuro-ophthalmologist from Freiburg, Germany, delivered the Ridley Lecture here, on the topic of on neuro-ophthalmology in the age of MRT.

Prof. Scharrer introduced the speaker with mock disbelief.

“A Ridley Lecture to be read by a neuro-ophthalmologist?” Prof. Scharrer said. “This is a wide span, between microsurgery and a scientist who works in a field which seems strangely a bit off.”

But Prof. Kommerell noted that Prof. Harold Ridley, for whom the lecture is named, understood that ophthalmic surgery is only part of ophthalmology.

Prof. Kommerell explained that MRT can help to arrive at a diagnosis when functional tests do not tell the whole story.

He described the case of a patient with pituitary adenoma with typical preoperative defects on perimetry. Postoperatively the left eye was blind, but the right eye was relatively unaffected; function was fully preserved, Prof. Kommerell said. Ophthalmologists continued to see the patient during the follow-up period, and because there was preserved function no one saw any reason for neuroradiological diagnosis.

“But when a computer tomogram was made after some time, it was seen that a recurrence of the pituitary adenoma had in fact occurred,” Prof. Kommerell said. “Was this a surprise? Not really, because one thing is for sure; in a position where the optic nerve is already atrophic and when no functioning fibers exist, a recurrence won’t be detected.”

A relapse can be identified by further deterioration of visual function, Prof. Kommerell said. He concluded that visual field is a sensitive indicator only during initial diagnosis, not later during follow-up. That is when MRT is needed, he said.

However, there are limitations to even this technology, and MRT coupled with functional tests still may not be enough. He presented another case example confirming the limitations of MRT.

A female patient was referred to a neurologist with bilateral loss of visual field. The neurosurgeon was ready to operate for pituitary adenoma, but Prof. Kommerell said he saw that the temporal defects in this patient also affected the nasal segments, which is typical of refractive scotoma.

“Perimetry was not mapped correctly because of ectasia of the bulb,” Prof. Kommerell said. “For necessary examination you need to examine from the direction where you see the losses. We found that you needed –7 D in order to get a clear image of the fundus.”

Prof. Kommerell said he told the neurologist about his findings and the neurologist agreed that it does happen every now and again, that the pituitary was as large as he had found it, but without the presence of adenoma. But this patient, according to the neurologist, had been referred for temporal visual defects.

“So this was an ophthalmologic misinterpretation, and this actually led the neurologist on the wrong track,” Prof. Kommerell said. “The compression of vision, part of it can only be diagnosed with the help of a corresponding MRT plus characteristic impairments of function. These two really belong together.”

The benefit of MRT, Prof. Kommerell said, is that MRT can show a tumor recurrence even in “silent” areas of the visual pathway.

“However, it cannot tell us if the optic nerve is under compression,” he said. “MRT can show the cause or motility disturbances, but only if you ask adequate questions. It will not supply any information in the case of functional disturbances.”

LASIK re-treatment

Calculating residual stromal thickness is an essential component of an examination for LASIK enhancement surgery, according to a physician speaking here. The current best means of estimating residual stromal thickness is to measure the original flap thickness and to use the appropriate calculation method, said Perry S. Binder, MD.

“What is the safe residual stromal thickness we must have?” Dr. Binder asked. “If you look in the literature, some say it has to be more than 250 µm, others say 200 µm, some say you can’t go below 50% of the corneal thickness, others say you can’t remove more than 18% of the corneal depth, but nobody really knows. This is all theoretical material.”

According to Dr. Binder, the importance of calculating residual corneal thickness is to determine whether sufficient tissue remains after ablation to minimize the risk of ectasia and avoid structural weakening.

Dr. Binder and colleagues conducted a retrospective, comparative, interventional case study of 6,235 eyes with ultrasonic measurements performed during LASIK surgery. Ultrasonic corneal pachymetry was performed immediately before and after flap creation and immediately after laser ablation during primary procedures and after enhancements. The study included 647 enhancements.

Dr. Binder said that, using the residual stromal thickness measured at enhancement as the actual residual stromal thickness, measurements of residual stromal thickness performed immediately following laser ablation overestimated residual thickness due to laser-induced stromal dehydration and microkeratome effects. He said estimates of residual stromal thickness using a standard flap thickness or estimated flap thickness were less accurate predictors of residual stromal thickness compared to use of the theoretical laser resection with a measured flap thickness or a modified flap thickness subtracted from the postop corneal thickness, which provided the best estimates of residual stromal thickness.

“We want to understand the potential causes of ectasia,” he said. “One needs to define the parameters that are most likely responsible: flap thickness, the resection of the laser and residual stromal thickness.”

Wavefront for myopia

Wavefront-adjusted LASIK using the Allegretto excimer laser can successfully treat mild to moderate myopia with and without astigmatism, according to a presentation here.

“The predictability of the nomogram is not yet perfect, but the predictability is really high,” said Tobias Neuhann, MD.

Dr. Neuhann and colleagues in Munich evaluated the effectiveness and safety of LASIK using the WaveLight Allegretto small-spot, 0.95-mm scanning excimer laser to correct low and moderate levels of myopia and astigmatism.

“The Allegretto, simply speaking, is a logical advanced development of the well-known lasers,” Dr. Neuhann said. “What is important in the Allegretto, and what helps you to get better results, is the integrated slit lamp. You also use this lamp for intra- and postoperative examinations directly on the patients. Also, the deep measuring unit is important. Additionally, you can vacuum off the ablated tissue right at the site of action.”

A consecutive series of 507 eyes with myopia of –0.5 D to –10 D and cylinder of less than 3 D were enrolled in this single-center prospective clinical trial. The patients were treated with LASIK and followed for up to 12 months. The Bausch & Lomb Hansatome microkeratome with a 160-µm thickness plate and the Allegretto WaveLight excimer laser with new software for stromal ablation were used in all procedures. Re-treatments or enhancements were excluded from the study.

Twelve months after LASIK, the mean postop manifest spherical equivalent was +0.16 D ± 0.82 D, compared with a preop mean of –4.76 ± 1.83 D. The corrected visual acuity was 20/30 or better in 92% of eyes and 20/20 or better in 83.9%. A total of 98.2% were within ± 1 D of emmetropia, and 78% were within ± 0.5 D.

The refractions were generally stable after 1 month, and the change in refraction between postop examinations was within ± 0.5 D in 96% of eyes. An increase of one or two lines of acuity was seen in 36.91%.

Ophthalmic pathology

Ophthalmic pathology may be a neglected subspecialty at the present time, but it is not dead yet, according to a world-renowned ophthalmic pathologist.

During his fifth presentation of the keynote lecture to the meeting of the German Ophthalmic Surgeons here, David J. Apple, MD, discussed the rapid decline in interest in ocular pathology and speculated on whether the lapse was to be temporary or everlasting. Dr. Apple based his comments on his 30 years of experience directing a successful pathology laboratory and biodevice research center.

According to Dr. Apple, today the profession’s needs are mostly in the areas of research ocular pathology, biomedical engineering and biodevices research, the latter being most crucial for ophthalmology. Many pathology laboratories throughout the world have not kept pace with changes in these areas, he said, and some authorities have declared that ocular pathology is a “dying specialty.” This opinion is based on reasons including a general resistance to change, financial need, lack of support from department chairmen and administrators and failure of pathologists to re-educate themselves regarding modern needs.

“In my opinion, routine descriptive pathology, which has been practiced since an early time, is seriously wounded,” Dr. Apple said. “It will never come back full time. Financially it will not work, and there are too many important things for the future to do. However, if leaders recognize this and give support to pathologists, and let them work with industry, they will turn out to be very successful, and the subspecialty of ocular pathology will indeed survive.”

Among the problems faced by pathologists, perhaps financial dilemmas are the most obvious, Dr. Apple said. Many chairmen of departments of ophthalmology do not support ocular pathology due to the pathologist’s lack of money-making capabilities for the department. There is also a lack of financial grant support for this type of research. To illustrate this, Dr. Apple drew on his personal experience of applying for federal grants in 1984 when he first started working with IOLs. He said he applied to the National Institutes of Health for funding.

“They told me very quickly ‘no,’ I couldn’t have one,” Dr. Apple recalled. “The reasons were because they thought we would not get enough specimens, but they also said that IOLs would not last long. With regard to the number of specimens, as of now we have 17,500, including about 10,000 explants and about 7,000 autopsy eyes.”

Dr. Apple added that academic pathologists must have the ability and willingness to work with the private and corporate sectors. They must also be willing to learn and apply the modern techniques necessary to carry on high-quality biomedical research and provide meaningful contributions to clinical ophthalmology and society. It is time for the leaders in ophthalmology to recognize the potential consequences of allowing further decline in this field, he said.

Epi-LASIK

Mechanical separation of the epithelium before laser ablation may be preferable to the use of alcohol to loosen the epithelium, according to one speaker.

Studies show that mechanical manipulation of the corneal surface tissue does not affect normal cell morphology as does separation using two different alcohol concentrations, said Ioannis G. Pallikaris, MD, who gave the Innovator’s Lecture here.

“Epi-LASIK is a treatment method where the preparation of an epithelial flap occurs without the use of alcohol, but by purely mechanical means,” Prof. Pallikaris said. “The epithelium is separated by a subepithelial separator, similar to a keratome. Microscopy shows a very nice demarcation between what is being separated.”

Prof. Pallikaris described a study in which 10 eyes of 10 patients underwent de-epithelialization using two techniques: six eyes had the epithelial layer mechanically separated with a customized instrument, and four underwent conventional laser epithelial keratomileusis (LASEK) with alcohol concentrations of 15% and 30%.

He said patients undergoing the LASEK procedure have a lower rate of haze than those undergoing photorefractive keratectomy, but alcohol toxicity remains problematic. Toxicity is dependent upon the alcohol dose and time of application, Prof. Pallikaris said.

A published study indicates that 80% alcohol for 20 seconds is sufficient to dissect the epithelium, he said, while another study shows that 18% alcohol requires a maximum exposure time of 40 seconds for patients with firm epithelial layers.

Prof. Pallikaris performs the separation at the stromal surface. He said epi-LASIK has been studied in human eyes as well as in rabbits. The eyes were followed for 24 hours and longer. Prof. Pallikaris reported that the epithelial cells seemed to be vital without any obvious morphological changes. The epithelial flap retained its normal multilayer structure.