Phakic anterior chamber intraocular lenses

Meridional differences in internal dimensions of the anterior segment in human eyes evaluated with 2 imaging systems

PURPOSE

To evaluate meridional differences in angle-to-angle (A-A) and sulcus-to-sulcus (S-S) dimensions in human eyes using very high frequency ultrasound (VHF US) and anterior segment optical coherence tomography (AS-OCT).

SETTING

John A. Moran Eye Center, University of Utah, USA; Berlin Eye Research Institute, Germany; Quattroelle Centri Oftalmochirurgici, Italy.

METHODS

Human autopsy eyes were fixated to special eye holders and had anterior segment scanning using 50 MHz ultrasound (Artemis, Ultralink) (20 eyes) and AS-OCT (SL-OCT, Heidelberg Engineering) (24 eyes). Seventy-three eyes (58 patients) also had anterior segment scanning using the same systems (Artemis, 50 eyes; SL-OCT, 23 eyes). Four meridians were evaluated in each eye. The A-A dimensions were measured by VHF US and AS-OCT. The S-S dimensions were also measured by VHF US. Statistical analyses were done with the Huynh-Feldt test.

RESULTS

In the autopsy-eye study, the differences in A-A and S-S dimensions between the 4 meridians in eyes analyzed with VHF US were statistically significant (P=.002 and P=.009, respectively). The differences in A-A dimensions in eyes analyzed with the AS-OCT were also significant (P=.005). The same findings were observed in the clinical study (VHF US, P=.001 for A-A and P<.001 for S-S; AS-OCT, P<.001 for A-A).

CONCLUSIONS

This study suggests that the internal geometry of the anterior segment of human eyes does not constitute a circle. This may have significant relevance for the accurate sizing of phakic intraocular lenses.

Phakic Intraocular Lenses

An analytical review of the data available in the field of phakic intraocular lens implantation was conducted. Particular attention was paid to the more critical issues of intraocular lens sizing and safety guidelines. A comprehensive, competitive analysis of different implantation sites, intraocular lens model designs, and safety guidelines has been included. Specialized biometry techniques, such as very high frequency ultrasound and Scheimpflug imaging, have been reviewed, and a critical review of commercial claims regarding intraocular lens technologies has been included. Clinical studies of phakic intraocular lenses demonstrate increasing promise for the correction of refractive errors not amenable to mainstream excimer laser refractive surgery. The main issues currently revolve around adequate lens design (VHF ultrasound study suggests that custom-design and sizing may be the most effective and safest approach for every phakic IOL model), because these devices will be required to remain physiologically inert and anatomically compatible with internal ocular structures and relations for several decades. The possibility of safe removing or exchanging the IOL should remain a feasible option over time. It is of utmost importance that we continue to critically evaluate current encouraging short-term outcomes, which are being extrapolated to the longer term by ongoing high resolution imaging and monitoring of the anatomical and functional relations of implanted phakic IOLs.

New intraocular lens technology

PURPOSE

To review the current status of phakic intraocular lenses (IOLs), intraocular treatment of presbyopia, and IOLs that filter some blue light.

DESIGN

Review of current information on the subject from numerous sources.

METHODS

Medline search and Internet search engines on the topics of phakic IOLs, presbyopia or multifocal IOLs, and blue light and macular degeneration.

RESULTS

An iris fixated phakic IOLs is now approved in the United States (US). There are concerns for corneal endothelial stability and late dislocation. Other approaches include anterior chamber fixation with concerns of corneal endothelial stability and pupil elongation, and posterior chamber fixation with concerns of cataract formation, IOL dislocation, and pigment dispersion. Intraocular treatment of presbyopia includes monovision, multifocal, and accommodative IOLs. Which approach is superior today is still not clear. There are IOLs designed to block some blue light to potentially lessen the risk of age-related macular degeneration (ARMD). While there is presumptive evidence of this, no definitive study shows such a correlation. Color perception issues are unlikely to be a problem. While decreased scotopic vision has been proposed, there is no study that proves this is an issue of clinical significance.

CONCLUSIONS

The IOL field is dynamic with many new choices. Phakic IOLs and treatment of presbyopia will be an increasingly important part of ophthalmology; however, there are important unresolved issues. With better evidence that blue light is an important variable in ARMD, such an approach could rapidly become the standard.

Professor Peter Choyce: an early pioneer of intraocular lenses and corneal/refractive surgery

Professor Peter Choyce, FRCS, DOMS, MS, was one of the pioneers of intraocular lens implant surgery. He developed an interest in artificial lens implantation following cataract surgery, a procedure that was widely criticized by the ophthalmic establishment in the UK, Europe, North America and other countries. Owing to the opposition to the intraocular lenses, Peter Choyce together with Sir Harold Ridley co-founded the International Intraocular Implant Club in 1966, which was responsible for the gradual acceptance of artificial lens implantation. Peter Choyce developed several models of intraocular lens, but did not patent the majority of them. The Choyce Mark IX, manufactured by Rayner Intraocular Lenses, became the first US Food and Drug Administration-approved intraocular lens in 1981. A review of Peter Choyce's record confirms a significant number of original innovations in the field of anterior segment surgery, including many procedures taken for granted today, but not associated with his name. These include early work on both kerato- and intraocular lens-refractive procedures, keratoprosthesis, pioneering paediatric implant procedures and others. Unfortunately his tenacious adherence to anterior chamber lens technology, while in general clinically sound, caused many to question his influence and hence he remained poorly understood even until after his death. He passed away on 8 August 2001 after a long fight with colon cancer. In this article, we provide evidence and elaborate Peter Choyce's accomplishments, which places him as one of the most innovative ophthalmologist in his surgical field in the twentieth century.

Refractive Surgery Survey 2001

In February 2001, a questionnaire on the practice of refractive surgery was sent worldwide to all 8196 members of the American Society of Cataract and Refractive Surgery; 1511 responses (18.4%) were received. Although laser in situ keratomileusis (LASIK) was the most common refractive procedure reported, phakic intraocular lenses, clear lens extraction, and photorefractive keratectomy were also widespread. Nineteen percent of the respondents said they had had refractive surgery, and that group reported performing significantly more procedures than those who had not had a refractive procedure (P < .0001). The most common complication of LASIK was dry eyes, occurring in more than half of the cases in one fourth of the practices; however, only 30% of surgeons said they perform a Schirmer test before surgery. High-volume surgeons reported seeing fewer cases of flap striae (P = .002) and slipped flaps (P = .02) than low-volume surgeons. Seventy-seven percent said that wavefront LASIK ablation will increase the quality of vision and of those already performing wavefront ablation, 92% stated they believe it will improve outcomes.