Page 14 - NAME OF CONDITION: REFRACTIVE ERRORS

• One should not sleep overnight with the regular daily wear contact lens on. The
oxygen supply to the cornea is totally cut off during sleep by the contact lens. The

oxygen deprived cornea is liable to damage and ulceration.
• The eyes should be periodically examined by an eye care professional to look for any

infections or corneal damage, possible due to contact lens wear.
The latest innovation in the field is extended wear contact lenses which can be used over a
longer period of time. Wearing of contact lenses during waking and sleeping hours, i.e.,
continuous 24 hour wear for a specified number of days. NOTE: The FDA recommends no
longer than six (6) consecutive nights wear for traditional extended-wear lenses. These
lenses allow free passage of oxygen through them to the cornea, but even they must be
used with care.

Refractive Surgery for Myopia, Astigmatism and Hyperopia

Refractive surgery may be considered when a patient wishes to be less dependent on
eyeglasses or contact lenses, or when there are occupational or cosmetic reasons not to
wear eyeglasses.
Patient expectation will be the main pillar around which all the other structures of the

preoperative examinations should be built. The motives for desiring refractive surgery
should be carefully discussed with the patient by the surgeon. Individuals who expect only
6/6 and nothing less should be discouraged from having refractive surgery, while patients
motivated by a desire to reduce their dependence on glasses or contact lenses, will be good
candidates.

Keratorefractive surgery can be applied to a broad range of refractive errors, but in some
circumstances, the surgeon may consider an intraocular procedure like the placement of
an intraocular lens (IOL) implant, either in front of the crystalline lens (phakic IOL) or in
place of the crystalline lens (refractive lens exchange).

Preoperative evaluation
1. Patients to discontinue contact lenses at least 1 week before surgery because of the
possibility of contact lens induced corneal warpage. Toric soft contact lenses and rigid
contact lenses should be discontinued for a longer period (atleast 2 weeks) because

they are associated with a greater potential for corneal warpage and refractive
instability.
2. Visual acuity without correction
3. Manifest, and where appropriate, cycloplegic refraction: The stability of the refraction
should be well documented. If the patient is seen for the first time, it may be prudent
to ask for his previous refraction powers and compare with the present
4. Detailed anterior and posterior segment evaluation: A thorough anterior segment
evaluation before and after pupillary dilation is crucial. Potential anatomical problems

like a prominent brow, narrow palpebral fissure and peripheral vascular pannus should
be looked for, since these may pose problems during microkeratome operation. As the

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