Ординатура / Офтальмология / Английские материалы / Manual of Practical Cataract Surgery_Sundararajan_2009

Capsulorhexis in Detail 89

Repeat capsulorhex is from left side — Clockwise Rotation Flap magnified

Make a small side incision raise the flap → pull the free flap all around from the existing

Figs 4.7A to I

gets extended sometimes creating a tear at posterior capsule producing vitreous disturbance and nucleus or IOL drop.

Creation of Cystitome

The routine practice of bending the needle (26 gauge) to 45 to 60 degree can be followed and done as usual.

90 Manual of Practical Cataract Surgery

Tip of the needle is bent at 90 degree either at the hub of the beveled edge or at the base.

The 90 degree bent - tip of the needle, if used to fold the flap and to push the anterior capsular flap to create a circular capsulorhexis with a clear-cut margin, it usually creates a puncture of the flap and tears jeopardizing the procedure.

Instead, if the tip is bent for 45 to 60 degrees and used carefully, to push or pull the flap, with the help of the slope in the tip, puncturing and tearing can very well be prevented.

COMPLICATIONS

The beginners while doing capsulorhexis, they fail to achieve the satisfactory size, of the hole and the shape.. Sometimes it becomes irregular.

In order to rectify this unfortunate attempt, the surgeon can re-create a circular rhexis, starting from the edge of it at 3 or 9 O’clock positions or at any suitable position of surgeons choice. and convenience, by creating a free flap from the edge of failed rhexis by doing a U shaped or lower half of C and develop a circular rhexis - as suggested in the picture.

This can also be done with the same needle or utrtas forceps.

For a capsulorhexis using a forceps ( for beginners)

Catch hold of the free flap (after an initial puncture) of anterior capsule at or near the peripheral edge with the forceps of surgeons choice and tear carefully round, millimeter by millimeter carefully, till you complete a circular tear.

The same principle is applicable to other methods also (Follow the legends already available).

Understanding the

Basics of Strabismus

PREFACE TO STRABISMUS

As everybody is interested in learning phaco and microphaco, and the concentration is diverted towards that line, only a little interest is shown to squint or strabismus

Infact, in some centres, the subject is totally eliminated.

Hence, I have made an attempt to simplify the subject and express the importance so that everybody can easily understand the subject.

It is not my intention to deal elaborately about the details of each and every part of this subject as it is an annexe part of the origional manual phaco.

For further detailed knowledge about this subject, the readers are requested to refer appropriate text books and other referances to update their knowledge.

The Author

Understanding the Basics of Strabismus 93

On reading the above classification, the reader or the student will understand that there is definitely a relationship between refractive error, accommodation, and convergence.

Basic

•Eso means deviation of the eye towards the nose.

•Exo means deviation of the eye towards the earlobe.

94 Manual of Practical Cataract Surgery

•Phorias means a tendency of the eye to deviate.

•Tropias means already deviated, developed, established, manifested.

if untreated->sustained contraction of ciliary muscles (changes the lens curvature)

(Accommodation)

Convergence.

=refractive errors(hypermetropia) → accommodation → convergence.

One dioptre of hypermetropia produces one diopter of accommodation which in turn produces two meter angles of convergence.

The refractive error namely hypermetropia (if uncorrected) produces sustained contraction of ciliary muscles (accommodation) which is also always associated with a determined amount of convergence.

This is due to a simultaneous stimulation of the the visual cortex whenever the accommodation reflex is stimulated i.e., accommodative stimulus acts as a trigger mechanism->stimulates->convergence.

ACCOMMODATION

Is a process by which the lens changes its focus from distance to near and viceversa. The ciliary muscles through its zonules are attached to the equator of the lens. There are three types of muscles viz., circular, longitudinal and meridional (oblique) muscles.

The rays or objects from infinite are parallel rays when accommodation is at rest, falls on the light sensitive layers

Understanding the Basics of Strabismus 95

of the retina after converging by the lens. When the object comes closer and closer, the rays becomes divergent. And so they fall behind the light sensitive layers of retina. One diopter of hypermetropia creates one diopter of accommodation, which in turn creates two meter angles of convergence--one meter angle for each eye. Although the incident-infinite distant rays(objects) are parallel, the emergent rays from the eyes should have a wider field in each eye having an overlaping of the two fields producing binocular single vision.

This binocular single vision consists of three processes viz.

1.Simultaneous perception.

2.Fusion.

3.Stereopsis (depth perception)

For this, both eyes should have an acceptably good vision, having a simultaneous perception,to fuse the two objects having stereopsis (depth perception).

The process of accommodation varies as the child grows old. At the age of 10 yrs the accommodation is at 7 inches, which recedes to 22 inches at the age of 40, and recedes more and more as the age advances.

In case the individual is hypermetropic, even for distance (infinite), the ciliary muscles are in a state of sustained contraction, producing pain, headache, and eye-strain.

If circular muscles are acting, there will be pain around the eye. When radial or longitudinal muscles are acting, the pain will be radiating to the back of the head. Possibly there may be a relationship of oblique muscles to that of astigmatism. This is an unauthorised deduction. There is an associated convergence in relation to the accommodation.

Accommodation and convergence are both reflex processes which has the control at the area no. 17 to 19.of visual cortex.

96 Manual of Practical Cataract Surgery

Nerve Pathways

Accommodation and convergence have different nerve pathways. This is also important to know where the level of lesion is.

The accommodation may fail, paralyse, or may become insufficient in certain conditions and similarly spasm of accommodation may also occur.

Cycloplegia or Paralysis of Accommodation

The following are the conditions where it occurs:

a.Cycloplegic drugs -may be unilateral or bilateral.

b.3rd nerve paralysis or paresis.

c.Alcoholism, diabetes, neurological disorders.

d.Sexually transmitted diseases

e.Diphtheria, syphillis etc.

f.Myopia - defect is not noticed.

g.Hypermetropia -both distance and near vision are affected.

h.Emmetropia-only near vision alone is affected.

Insufficiency of accommodation is seen in presbyopia due to normal physiologically related conditions, ageing, glaucoma, eye strain, due to excessive near work. Spasm of accommodation may occur due to use of miotic drugs. Uncorrected refractive errors, insufficient illumination, anxiety, and tension. Use of drugs-atropine, can abolish the spasm of accommodation and pain also.

HETEROPHORIA

Phorias may be eso, exo, hyper, hypo, and cyclo. The causes of—

98 Manual of Practical Cataract Surgery

SYMPTOMS

Depends on decompensation.

Sometimes larger phorias may not produce symptoms. But smaller phorias can cause severe symptoms. People who do more close works may produce more symptoms than others like farmers.

Symptoms in uncompensated phorias patients may produce:

1.Symptoms of muscles fatigue like headache or aching pains, which disappears on closing one eye.

2.Difficulty in changing focusnear to distance and vice versa.

3.Photophobiawhich disappears using dark glasses or relieved by closing one eye.

Symptoms due to difficulty to maintain binocular vision:

1.Blurring of letters.

2.Intermittant diplopia (due to temporary deviation of visual axis).

3.Intermittant squint which is noticed by friends.

Symptoms due to defective postural sensations:

•Transmitted from ocular muscles due to alteration of muscles.

•Tones-like landing of aircrafts or during playing games.

Eye Examinations

1.Vision(both distance and near vision) in both eyes.

2.Cycloplegic refraction and correction with spectacles. Hypermetropia must be fully corrected as this is closely