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Implant KAMRA™ (KAMRA inlay, Acufocus)

KAMRA inlay: definition

The KAMRA is an intra corneal (corneal inlay) implant designed to correct the presbyopia.  It induces an increase in the depth of field of the eye through the formation of a new pupil.

Center excellence acufocus kamraThe technique for correction of presbyopia by the KAMRA inlay was initially made in France exclusively to the Rothschild Foundation, share the choice of American society Acufocus, which wanted its technology to be initially conducted in a centre of excellence, before spreading to other centers selected later. Tens of thousands of implants have been placed in the world over the past 7 years. This technology has been approved by the Food Drug Administration (FDA) in April 2015 @.

The kamra (Acufocus) in short:

-PURPOSE: giving back to the presbyope can perform tasks in near without glasses vision and reading.

-Unilateral procedure: the implant is placed in an eye (eye dominant, generally intended for near vision), under local anesthesia (drop), on an outpatient basis.

-Intervention accessible to presbyopes who have glasses by far)KAMRA at the presby normalsighted) And carriers of an optical defect presbyopes (KAMRA in ametropia presby, who have a default associated with distance vision: myopia, farsighted, astigmatism).

-Minimally invasive procedure (the implant is not placed "in" the eye but in the cornea, which is the transparent outer tunic), adjustable and reversible (the implant can be easily removed at any time).

-Procedure for restoring a good visual acuity of near not corrected without major reduction of Visual acuity by far (joint of far and near Visual acuity improvement is possible in some case).

-Simple and proven optical principle: the principle of this technique is simple and is based on that of the "pinhole" (principle it even taken from the 'camera obscura', designed to the Renaissance and probable ancestor of artificial imaging systems!).

-The placement of the implant is done under local anesthesia, and ambulatory (home) the same day.

-It can be accomplished in presbyopic patients normalsighted (no glasses by far), hypermetropia, or short-sighted.

Presbyopia surgery is a very active field, making the object of (too much?) communications in the media, and sometimes too hasty fads for certain technical novelties. This is mainly related to the fact that the market is very important (all adults from the forties), and a technique even of 'niche' is likely to encounter an absolute number of candidates high. It should be borne in mind that as for other corrections in refractive surgery, the results depend on the careful selection of candidates and the careful execution of the surgical technique. On the technique described below (KAMRA), a detailed preoperative ophthalmologic assessment and respect the guidance is essential for obtaining a good functional result.

Principles of the kamra

The implant KAMRA™ (Acufocus) allows an increase in the depth of field by reduction of the diameter of the pupil of entry of the eye.  It is designed to be inserted into the cornea (in the) stroma), under local anesthesia (drops) and the loss of the vision of some presbyopic patients. It is definitely the device for the correction of presbyopia which the mechanism of action is the simplest (pinhole), and the best known (many imaging instruments were built according to this principle since the 16th century).

Pupillary opening and depth of field

In photography, the beneficial effect of the reduction of the diameter of the diaphragm ("close the diaphragm") on the depth of field is well known and used for objects at different distances are released to the net on the final shot.  In technical language, we play on the increase of the "f-number," which is the ratio between the focal length used (the focal length determines the width of the field of shooting) and the diameter selected for the diaphragm. For a focal length of 50 mm and an aperture of 10 mm, the aperture number is equal to 50/10 = 5 - noted f: 5).

By 'closing' much the diaphragm (ex: f 20), the range of sharpness increases regardless of the focal length, IE objects or characters located at different distances (close and distant plans) will be 'net' on the completed picture.

depth of field kamra

Effect of the closure of the diaphramge on the depth of field. In two shots, the update is performed on the same terminal of Vélib (framed in red). Downstairs, a magnification reveals that the cliché with a closed diaphragm has a superior sharpness for frequent targets. This is the same mechanism that explains the beneficial effect of the kamra on the near vision. It should be noted that this increase in the sharpness of almost does not come at the expense of sharpness by far.

In patients who have a light refractive defect (low myopia, low astigmatism), is often seen as an important myosis improves visual acuity for distance vision uncorrected (the myosis is the reduction of the diameter of the pupil, which gets close to 2mm). The explanation of this phenomenon lies in the reduction of the retinal illuminance task for the same degree of defocus myopic: this reduction is caused by the reduction of the diameter of the entrance pupil that thins the defocalisee light beam.

Thus, pupillary con-necking phenomenon allows the light short-sighted (ex:-0.50 D) to achieve a Visual acuity close to 10/10 in case of intense brightness. When the pupil of these patients has a nearby diameter of 4 mm (lighting 'standard'), the task illumination retinal is "enlarged" because of nearsightedness (light rays converge in front of the retina). This reduces the theoretical resolution of the eye and explains the loss of 5/10 area. In case of intense illumination (ex: outside on a nice summer day), the diameter of the pupil is reduced; This allows to reduce the task of retinal illumination, and to increase the resolving power of the eye that can reach a value close to 10/10.

When the accommodation, pupillary reflex of con-necking occurs: this constriction promotes the vision by the increase in depth of field, but this con-necking is not sufficient, alone, to allow a long-sighted topic to read.

Implant Kamra and retinal blur reduction

The insertion of a device to "Astrophoto" the pupil of less than 2 mm entry could make eye surgery a reduction in retinal blur induced by the lack of accommodation. This idea to presided over the development of an intracorneen implant (also called "inlay") to achieve this goal and intended to be implanted in the eye dominated subjects normalsighted and presbyopic (only one eye is operated). The KAMRA procedure is unilateral.

implant Kamra on depth of field effect

After insertion of the KAMRA inlay retinal blur reduction

 

The kamra allows to reduce the width of the beam of incident rays that penetrate the eye: This allows to reduce the "retinal blur" related to the lack of accommodation.

Photo KAMRA Acufocus

Profile picture of an eye where a KAMRA implant was placed, with schematic representation of the "selection effect" on the incident rays of the implant.

Description of the kamra

The KAMRA inlay is made of a biocompatible synthetic fabric (also used for the realization of vascular prostheses endo). It can be described as a kind of "confetti" very fine (5 micron) whose external diameter is close to 3.5 mm and the internal diameter of 1.6 mm. In addition the center hole (with optical sight), the inlay has of many micro perforations designed to facilitate the passage of the metabolites (nutrients) corneal. The kamra has been the successive improvements, including on its thickness reduction and increase the breakdown of the number of micro perforations.

Implant Kamra (corneal inlay)

Implant Kamra (intra corneal inlay)

Remember that in a subject not far-sighted, accommodation results in increase of the power of the lens, which allows to form a sharp image of the book or read text on the retina. To the presbyter, the accommodation is reduced, and no longer allows to focus the image on the retina (the plan of sharpness is located behind it). On the retina, the image of a point extends which induces a retinal image blur. After insertion of the KAMRA inlay in the cornea)see surgical video of the laying of the kamra), the beam of rays of light défocalisé is finer; the retinal image blur is reduced. Books to read distance vision becomes possible. Distance vision, when the brightness decreases, the pupil dilates beyond the projection of the edges of the inlay which allows the eye to collect more light.

Kamra implant inserted

Clinical experience with the kamra

Our pioneering experience in France (since June 2010) with the KAMRA device is positive, the increase in beach of clear vision for presbyopes find a NET Visual acuity closely while preserving Visual acuity by far, which is the most interesting aspect of this technique, in addition to its reversible appearance (possibility of implant removal). Unlike other techniques like the presby LASIK, the mechanism of action is precise and predictable, and there is no withdrawal of corneal tissue (except in combination with LASIK case). Unlike the IntraCOR, this technique is adjustable and reversible, especially imperfect initial centering case. She also has the advantage of being able to be combined with a correction LASIK (the implant is placed in the interface, the flap, after related to excimer laser vision correction)

OQAS implant KAMRA

The depth of field of the eye with the intra corneal implant increased towards the eye not implemented. The measurement was made with the instrument OQAS (accommodation module)

 

It is easy to perform the inspection and monitoring of the kamra in the biomicroscope.

Implant Kamra (Biomicroscope)

Implant Kamra biomicropscopie (D Gatinel)

Implant KAMRA: cosmetic

If the implant is visible on photographs macro or close-up, on the cosmetic plan, it is impossible to discern the presence of firsthand, and neither look nor its brilliance are changed, because implant color is dark, and located next to the pupil, and even on the iris blue or clear.

cosmetic KAMRA

Cosmetic appearance of a patient whose one eye received an implantation of the KAMRA inlay. Top: photography from the front of the eye who received the implant. It's left eye, whose appearance remains simillaire to that of the right eye (bottom).

KAMRA and associated correction

As reported earlier, in case of the existence of a Visual defect by far associated with presbyopia (ex: myopia, hyperopia, astigmatism) a correction by laser excimer (LASIK) can be performed at the same time (pour corriger le défaut réfractif en vision de loin): the technique is referred to as ' Combined LASIK KAMRA "(CLK).  The kamra is then placed in the interface, and focused on the Visual axis, then the repositioned flap. The other eye may be operated only LASIK in the same sitting, in order to be corrected for the vision by far if necessary.

KAMRA and side effects

Reduction of retinal illuminance can induce a slight reduction in sensitivity to contrast, and as photoablatives surgery (LASIK, eximer laser), the existence of dry eyes post surgery is frequently observed. It involves the prescription of artificial tears in a systematic way in post operative. The drought affects the Visual recovery. "" The instillation of artificial tears helps the patient to relieve symptoms (tingling, foreign body sensation) and also ' clarify ' vision. This treatment should be continued for several months, and may be completed by the placement of tear plugs (devices to increase the contact time of tears with the ocular surface).

Complications

Rare late inflammations have been reported, most were able to be processed by local treatment combining diverse classes of anti inflammatory (eye drops). In the case where the inflammation persists and is accompanied by a change of refraction (hypermetropique ' shift'), the explantation (implant removal) is indicated, and is accompanied by a gradual return to pre-operative vision, pointing out the reversibility of this technique. In some case (absence of inflammation) reprocessing excimer laser may be performed, resoulevant initial flap of LASIK to correct hyperopia induced.

The feeling of a decrease of Visual acuity by far is usual to the immediate course of the surgery: she is multifactorial and is explained by the combination of a dry syndrome, and an irregularity of the epithelial surface. If the Visual discomfort continues, the possibility of an indadapte centering must be mentioned; case of proven shift, refocusing is indicated and can be performed secondarily.

Centering of the kamra

As with all refractive aiming techniques, the the centering quality is an important element for the functional result. The possibility of using the aiming and guidance of the excimer laser system (ex: beam centering for the eye tracker) and adjust the position of the implant necessary are all beneficial aspects in terms of security. There is no common method to identify the Visual axis for an eye given; However, it crosses the corneal plan between the vertex and the projection of the pupillary Center. Adjustment of the focus of the eye tracker on this area allows to check the right positioning of the implant in operating per.

KAMRA technique acufocus

Insertion of the kamra in a patient after correcting the vision of far (sim LASIK technique). flap of LASIK is recline: the eye-tracker of the excimer laser sighting system allows to facilitate good centering of the implant intra corneal (D Gatinel)

In the postoperative period, the image captured by the corneal topographer to compare the position of the kamra with respect to the pupil entrance and the central corneal reflection (vertex).

KAMRA centering

The position of the corneal reflection (vertex) allows to objectify the slightly nasal positioning of the inlay, whose balance was conducted at mid distance between the center of the pupil and corneal reflection (D Gatinel)

 

Balance is an important element towards the functional success: the advantage of additive techniques (such as inlays) is to allow the realization of a re positioning in case of shift (or imperfect centering). The following image to compare the position of the kamra before and after the refocusing on the pupil. Before the re centrement, the patient complained of intermittent perception of a "sail" and vision split in some light environments.

site of the manufacturer: www.kamrainlay.fr

 

KAMRA inlay self-contemplation

The images were obtained with the "Acutarget" system, which allows to measure the position of the kamra the corneal reflection (vertex) and the pupillary circumference (in green). It is recommended to focus the KAMRA inlay on the corneal reflection, or between this reflection and the center of the pupil. The initial position of the implant is too nasal (left image). After the uprising of the flap, the implant is repositioned in more temporal direction. In the postoperative period (right), the position of the inlay is considered satisfactory. The Visual acuity of the patient was improved, and greatly reduced Visual annoyance.

 

 

 

 

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