NCLE Exam Prep Part 1 out 4 Questions With Correct Answers

HYDROGEL - Answer Soft contacts are manufactured from hydrogel Due to the high water content there are often fluctuations in vision. Benefits of soft contact lenses: - Answer •Comfort •Shorter adjustment period •More comfortable in dusty environments •Sports. Excellent for athletics because soft lenses will not fall out of the eye •Good alternative to eyewear for patient with minor corrections characteristics of contact lens materials - Answer •Percentage of water content •The oxygen permeability •How well the material defends against deposits •Thickness •Lens edge • Lens color/tint •Design parameters •Length of wear •Replacement intervals SILICONE HYDROGEL - Answer •higher oxygen permeability. More oxygen than "hydrogel CLS. •Extended & continuous wear-approved for wear at all times for up to 30 days. standards. FDA approves 20 days, recommendation is to remove the lenses briefly every 7 days. •increased comfort and performance ALLERGIC RESPONSE TO SILICONE HYDROGEL LENSES - Answer allow more oxygen however, the added silicone can reduce the surface wettability of the lenses. people with marginal dry eyes might notice dryness and discomfort from silicone hydrogel lenses. This dryness-related discomfort can be mistaken as symptomatic of an allergy CONTRAINDICATIONS FOR SOFT LENSES - Answer •Irregular astigmatism-Although and comfort may be good, satisfactory visual acuity may not be achieved •liquid or gas in the air, the lenses will absorb them and become tainted. •Giant papillary conjunctivitis (GPC) type of conjunctivitis that is caused by wearing dirty soft contacts. Papillae bumps) will show up over the tarsal conjunctiva in the upper eyelids. If a patient develops this one time, then likely to develop it again, the patient should be a re-fit with rigid lens. •dry environment, will dehydrate more quickly. •irregularities or bumps on the sclera and/or bulbar conjunctiva may not be able to wear soft lenses. Increasing tear exchange in GP lenses to increase oxygen - Answer •Reduce the overall lens diameter • Flatten the peripheral curves •Decrease the optic zone optic zone - Answer the chord diameter over which the base curve extends on the posterior surface of the contact lens. It is described in millimeters (mm) of diameter. Secondary or Intermediate Curves - Answer Secondary curves are between the base curve and the peripheral curve on the posterior lens surface. secondary curve is usually 0.70 mm to 1.50 mm flatter than the base curve radius (average 1.0 khe lons to better align with the flatter portion of the cornea adjacent to the optical zone. Totel diameter - Answer determined by adding the CPC and the secondary curves together, As seen in the photo, the CPC is pumerically counted once while each peripheral number is counted twice. If you draw in imaginary line borizontally through the lens, it will appear that the peripheral curves lie on each side of the CPC. Blending - Answer the treatment given to the sharp junctions created by the differences in the radii of curvature between the base curve, the secondary curve, and the peripheral curve. Blends can be light, medium or heavy. anterior optical zone - Answer radius is the curvature on the anterior (front) lens surface which determines the refractive power of the lens. This curve may also be referred to as the power curve or the lenticular cap. Like the posterior optical zone, the anterior OZ has both a radius of curvature (power) and a diameter which are measured in millimeters. lens edge - Answer the most peripheral portion of the lens and represents the junction between the anterior and posterior surfaces. The edge can be divided into three zones: - Answer The Anterior Zone is the edge in contact with the upper lid during the blink cycle. Its function is to minimize lid irritation during the blink. The Posterior Zone is a small reverse curve placed on the posterior lens surface to flare the edge away for the cornea. The Edge Apex is the junction between the anterior and posterior zones. This junction must be well rounded to minimize lid awareness during the blink. Orbit: - Answer The bony cavity containing the eyeball and its adnexa. Globe: - Answer A round body; eyeball. Cornea: - Answer clear surface on the front of the eye that covers the iris and pupil. It lets light into the eye. radius of curvature of the front surface: 7.7mm radius of curvature of the back surface: 6.8mm. The center thickness is about 0.5mm. At the edges, it is about 1.0mm in thickness. An average cornea has a diameter of 11.5 horizontally mm and 11.2 mm vertically