Languages

Author
About us

share

This article has been read 1378 times
Share this content

Refer this article as: Masayoshi K., Accommodative micro-fluctuations, messages from the ciliary muscle, Points de Vue, International review of Ohthalmic Optics #58, Spring 2008

Accommodative micro-fluctuations, messages from the ciliary muscle

Online publication :
04/2008
Reading time :
5 min

Content

We might think that we are able to focus exactly on any object that we try to watch at a given distance. However, in practice, focusing at the correct distance is extremely rare, as the eye tends to focus slightly too near on distant objects, and slightly too far when at a near distance. In addition, the degree of tension of the ciliary muscle, applied in order to increase the refractive power of the crystalline lens, when one's gaze is fixed on a near point, varies greatly from one individual to the other and is not simply a function of the visual range.

We can have a good idea of the way muscles react under constraint by considering what is happening when we use our arm's strength to lift a load. If the load is light we can lift it comfortably. But if the load is heavy, it becomes difficult to lift, and if we keep holding it with our arms bent, we will then feel a tremor, produced by our muscles under tension. The weight of the load for which this tremor appears varies according to the physical strength, as well as the vitality or tiredness of the subject. A similar process occurs with the ciliary muscle, and the ciliary muscle tremors are defined as Accommodative Micro-Fluctuations. It is possible to represent the objective description and accommodation functional analysis of these tremors in a graph called the Fk-map (fig. 1).

Mapa Fk normal
Fig. 1: Mapa Fk normal

The horizontal axis of the Fk-map represents the distance of the visual target. The vertical axis represents the refractive value of the eye. Accordingly, the length of each vertical bar on the graph figures the refractive response of the subjects' eyes for a given target distance. Bars are then coloured in order to represent the frequency of occurrence of the high-frequency component of the Accommodative Micro-Fluctuations. In other words, the degree of tension of the ciliary muscle is classified according to colour.  A weak tension on the ciliary muscle is figured in green. A strong tension on the ciliary muscle shows in red. The interval in-between these extremes is then indicated by a standardized proportional colour gradation.

For a normal subject, as in figure one, the refractive response of the eye increases as the visual target get closer, but green is the underlying colour for both near and far distances. Looking at a visual target at a distance of approximately 30 centimeters produces a higher ciliary muscle tension, but only by a small amount.

In the case of a presbyopic patient, a typical Fk-map is as in shown figure 2. At a distance of approximately 2 meters, only a limited accommodation occurs, with some ciliary muscle tension, but at closer distance, greater focusing is not possible, and the ciliary muscle is not actively working (fig.  2).

Normal Presbyopia
Fig. 2: Normal Presbyopia

For a patient with a  problem  of  tonicity  of  accommodation, the amount of focusing follows the distance of the visual target, but we can notice than for any focusing distance, there is a strong tension working on the ciliary muscle (fig. 3)

Accommodotonia
Fig. 3: Accommodotonia

In a case of accommodative spasms, there is a strong myopisation of the eye and continuous ciliary muscle tension happens, regardless of the location of the visual target the subject tries to watch (fig. 4).

Accommodation Spasm
Fig. 4: Accommodation Spasm

In a case of Computer Vision Syndrome (CVS) (also called techno- stress ophthalmopathy), the ciliary muscle tension is not strong in response to a distant visual target, but when the subject attempts to watch a near visual target they lapse into an accommodation spasm-like condition. Some CVS patients complain that: «there is no problem in everyday life, but just as I set about doing computer work, eye pain and headaches happen, and I can't continue work». This complaint can be understood through the analysis of Accommodative Micro Fluctuation (fig. 5).

Techno-stress Ophthalmopathy
Fig. 5: Techno-stress Ophthalmopathy

With the observation of Accommodative Micro Fluctuations, accommodation disorders that had not been diagnosed previously can also be detected. Figure 6 is the Fk-map observed in a case of traumatic cervical syndrome resulting from a traffic accident. The patient complained that: «although it isn't that bad when looking at a distance when I try to watch something up close,   my eyes flicker and I have deep eye pain, headaches, and sharp pain in the nape of the neck. I can't read a book nor work». From the Fk-map we can well understand the patient's complaint. When the visual target is distant, the ciliary muscle tension is not so strong. When the visual target draws near, the ciliary muscle tension rises but the focus returns to distant, meaning that the patient focus did not accommodate to the intended distance. When she tried to see at near, it became increasingly difficult to see. Until this case was described, there had been no information about this type of accommodation disorder and it was provisionally referred to as accommodation panic.

Provisional Name : Accommodation Panic
Fig. 6: Provisional Name : Accommodation Panic

Patients that complain of eye fatigue are often complaining of an abnormal condition that can be related to Accommodative Micro Fluctuations. When we take a good look at the Accommodative Micro Fluctuation pattern of patients who consult about what they think to be eye defects, we become able to hear their complaints via the «cries» of the ciliary muscle.

Considering that the prescription of spectacles directly influences the ciliary muscle, we can then improve or preserve the health of our patients by prescribing corrective lenses that are gentle on the ciliary muscle. If we listen carefully to the messages of the ciliary muscle, they will tell us the optimum prescription for  our patients.

REFERENCES

References

References Masayoshi Kajita

Campbell, F.W., Rebsor, J.G. & Westheiroey, G: Fluctuations of accommodation under steady viewing conditions. J.Physiol. 145: 579-585, 1959.

Akihiro SuzumuraDA study of Accommodative Microfluctuation. Journal of Japanese Ophthalmological Society 79: 1257-1271, 1975

Akihiro Suzumura, Akemi KobayashiDA study of clinical diagnosis of Accommodative Microfluctuation. Ophthal. Physiol.Opt. 31: 367-373, 1980

Fuchuan Sun, Stephan Brandy, An Nguyen, Marga- ret Wong and Lawrence Stark: Frequency analysis of accommodation single sinusoids. Ophthal. Physiol. Opt. 9 : 392-397,1989.

Winn B, Pugh JR, Gimartin B, Owens H.: A trail pulse moderates steady-state ocular accommodation. Current Eye Research 9: 971-975, 1990.

Winn  B.,  Pugh  JR,  Gilmartin  B.,  Owens  H.:  The frequency characteristics of accommodative micro- fluctuations for central and peripheral zones of the human crystalline lens. Vision Research 30 : 1093- 1099, 1990.

Barry Winn, Bernard Gilmartin: Current perspective on microfluctuations of accommodation. Ophthal. Physiol. Opt. 12 : 252-256, 1992.

Lyle S.Gray, Barry Winn and Bernard Gilmartin: Effect of target luminance on microfluctuation of accommodation. Ophthal. Physiol.Opt. 13 : 258-265, 1993

Lyle  S.Gray, Barry  Winn and  Bernard  Gilmartin: Accommodative microfluctuation and pupil diameter. Vision Research 33 : 2083-2090, 1993.

Masayoshi Kajita:  Frequency  Analysis of  Accommodative Microfluctuation. Ophthal. Physiol. Opt. 41 : 1418-1422, 1990

Masayoshi Kajita: Clinical Significance of Accommodative Microfluctuation. Jpn. J. Vis. Sci 16 : 107- 113, 1995

Masayoshi Kajita, Yumiko lto, Ayako Yamada, Makiko Watanabe, Keiichiro Kato: Accommodative Micro- fluctuation and Eye Fatigue. Jpn. J. Vis. Sci 17 : 66- 71, 1996

Masayoshi Kajita, Yumiko lto, Kentaro Kobayashi, Makiko Watanabe, Keiichiro Kato: Detection of Resting State of Accommodation by Accommodative Microfluctuation. Journal of Japanese Ophthalmo- logical Society 101(5): 413-416, 1997

Masayoshi Kajita, Accommodative response, and microfluctuation. Ganka 40(2) : 169-177, 1998

Masayoshi Kajita, Makiko Ono, Setsuko Suzuki and Keiichiro Kato: Accommodative Microfluctuation in Asthenopia Caused by Accommodative Spasm. Fukushima

Masayoshi Kajita, Nanako Takahashi, Fumio Takahashi: Dry-Eye and Accommodative Stress-Possibility of their relationships. Japanese Journal of Visual Science 25; 40-45,2004

Masayoshi Kajita, Simulation, and  Psychogenesis visual defect. Japanese Journal of Neuro-ophthalmol. 21; 405-411,2004

Masayoshi Kajita,  Anomalous eye position, and anomalous accommodation. Journal of the Eye 21 (9); 1173-1178,2004 Journal of Medical Science 47(1) : 13-20, 2001

 

Keywords

Languages

Author
About us

share

This article has been read 1378 times
Share this content

Refer this article as: Masayoshi K., Accommodative micro-fluctuations, messages from the ciliary muscle, Points de Vue, International review of Ohthalmic Optics #58, Spring 2008

Continue reading