main-banner

NAVIGATION FOR TORIC IOLs, ICLs & ADD-ONs

 
The toric lenses are one of the important developments in recent years, with the most easily obtained happy patients. [1]
Although 35% of cataract patients remains with astigmatism of more than 1.50 diopters and 2% have more than 4.00 diopters [2] [3] [4], the percentage of toric lenses in Germany is <2% and in Europe <8%, globally still relatively low. [5]
The intraoperative aberrometry promises a better predictability of refraktion results and patient satisfaction at a reasonable additional cost level for the surgical team.

Remaining cylinder after astigmatism correction
For the toric and multifocal lenses every deviation concerning the diopters and position of the lens impacts patients satisfaction with the surgical result: per 1° deviation from the planned position decreases the corrective effect of a toric IOL by 3.5%.  At 10° deviation results in a loss of 35%, which is particularly problematic at high cylinder. [1] [6] [7]
Due to the modern haptic designs the postoperative lens rotation with tIOLs is not very important for the ultimate result. [8] [9] The intraocular positioning is the important determinant of patient satisfaction today. In a study at the University of Maastricht the error after manual axis marking with 4.9 ± 2.1 ° (n = 40) is indicated. [9]

Effort and precision of the axis marking
The highest accuracy, but also a lot of effort, can be reached by the marking with the slit lamp. The axis marker in the surgery room by swing markeur implies a lack of head fixation and is inaccurate.
Color markings carry the risk that the paint on the conjunctiva passes out of form or bleaches intraoperatively so that the precise positioning of the toric lens is difficult to impossible. This is especially true for the femtosecond laser.
In principle
the preoperative axis marking shows no surgically induced refractive changes (CIA).

Virtual cylinder axis marking
To increase the precision of the positioning of toric intraocular lenses there are now different surgical assistance systems available. Basically, the video overlay systems for intraoperative marking of preoperative detected cylinder axis differ from the intraoperative wavefront aberrometers. For the video overlay systems there is an inecactness concerning the preoperative ceratography axis marking and in the operating result. [10] [6]
Eye tracker and video overlay systems use reference points on the pupil, blood vessels in the conjunctiva or manual markers. Intraoperative mydriasis, a bleeding or a small image section affects the reliability of the axis marking for tIOL implantation.
Reliability of the virtual axis marking by intraoperative aberrometry only requires transparency of the dioptric apparatus. Intraoperative measurement excludes a confusion of preoperative patient data.

Accuracy of the virtual cylinder axis marking
Because of the patients lying position the intraoperative aberrometry determination and correction of corneal cylinder is without inaccurateness by cyclorotation. Also a surgically induced astigmatism (CIA) will be detected by the intraoperative aberrometry. For all these reasons, intraoperative aberrometry and virtual cylinder axis marking promises a higher accuracy and improved predictability of refraktion results.

Intraoperative visualization and minimizing the residual cylinder
The intraoperative aberrometry at the pseudophakic eye makes the residual cylinder visible and optimizable for the surgeon. Thus probably the greatest predictability of refraction results will be achieved.

Research & Development
Our R&D effort tries to achive the best simulation possible of the refraktion result and the transformation of the measurement value into concret medical advices for the surgeon. We try to implement a surgical navigation system for refractiv cataract- and lense surgery with high level of automatization.


Continue with  pfeil gruenCORNEA SURGERY

 

Literature

[1]

M. Tetz, R. Menapace und S. Schmickler, „Come and See Meeting,“ Horn, 2011.

[2]

K. Hoffer, „Biometry of 7,500 cataractous eyes,“ Am J Ophthalmol, pp. 90:360-8, 1980.

[3]

C. Hoffmann, „Analysis of biometry and prevalence data for corneal astigmatism in 23239 eyes,“ J Cataract Refract Surg, Bd. 36, pp. 1479-1485, 2010.

[4]

S. U. E. B. Ninn-Pedersen K, „ Cataract patients in a defined Swedish population 1986-1990. II. Preoperative observations,“ Acta Ophthalmol (Copenh) , pp. 72:10-5., 1994.

[5]

M. Wenzel, T. Kohnen, A. Scharrer und e. al., „Ambulate Intraokularchirurgie 2011: Ergebnisse der Umfrage von BDOC, BVA, DGII und DOG,“ Ophthalmo-Chirurgie, Nr. 24, pp. 205-214, 2012.

[6]

N. Morlet, J. Minassian und J. Dart, „Astigmatism and the analysis of its surgical correction,“ Br. J Ophthalmol, pp. 1127-1138, 2001.

[7]

W. Maloney, L. Grindle, D. Sanders und D. Pearcy, „Astigmatism control of the cataract surgeon: a comprehensive review of surgically tailored astigmatism reduction (STAR),“ J Cataract Refract Surg, pp. 15: 45-54, 1989.

[8]

G. Gerten und O. Kermani, „Toric IOLs for Astigmatic Correction,“ Cataract Refract Surg. Today Europe, p. 47, 11 2006.

[9]

N. Visser und T. Berendschot, „Accuracy of toric intraocular lens implantation in cataract and refractive surgery,“ J Cataract Refract Surg., 2011.

[10]

C. Kent, „37 Ways to Get Great Outcomes with Torics,“ Review of Ophthalmology, p. 26, 1 2012.