Rigid Gas Permeable Lenses Overview

Evaluating lens damage through observing tearing and irritation.

Allow a minimum of 10 minutes to observe lens settling (tear/comfort).

Evaluate lens positioning by observing pupil position and movement while blinking.

Classify lid-lens relationships as attached to the upper lid, extra-palpebral, or inter-palpebral.

Assess lens movement during natural blinking and external movement of the lens using lid.

Describe lens movement during blinking, noting speed, direction and smoothness (flat vs steep).

Visualize the fluorescein pattern on the superior conjunctiva to assess lens clearance.

Adjust lens centration if it is off center, using appropriate aids.

Small, fluid-filled sacs in the cornea, often from lens wear or inflammation, that can affect vision if numerous.

Epithelial microcysts can be caused by various factors like lens wear, dry eye, inflammation, or hypoxia (lack of oxygen).

A whitish, rounded deposit on the back surface of the cornea, appearing new and gradually turning orange/brown, often due to lens wear.

A small, irregular, dark, and transient zone on the cornea due to corneal edema and fluid buildup, often related to lens wear and oxygen deprivation.

Endothelial blebs are temporary, whereas corneal guttata are permanent, both appearing as dark zones on the corneal surface.

The main objectives of an RGP consultation are to gather patient information, assess suitability for RGP lenses, and plan the fitting process. This includes understanding patient history (prior contact lens wear, eye health), evaluating their expectations for vision, comfort, and health, and gathering preliminary data.

During an initial RGP assessment, essential information needs to be collected to evaluate the patient's candidacy for RGP lenses and plan the fitting process. These include their refractive error, corneal curvature measurements (Keratometry or K-readings), pupil size, horizontal visible iris diameter (HVID), palpebral aperture, and eye opening height.

Once the decision to proceed with RGP lenses is made, specific parameters need to be determined. These parameters include the lens type (e.g., materials, design), price, lens care routine, and any additional information needed for the lens order.

The first time the patient receives their RGP lenses, the focus is on proper lens assessment, education, and a planned adaptation schedule. This includes reviewing the patient's history, verifying their visual acuity, checking their eye opening height, assessing the delivered lenses, giving clear instructions on lens insertion and removal, detailing lens care and maintenance, and setting a tailored wearing schedule.

The adaptation period for RGP lenses is crucial for the success of the fitting. It's a gradual process that involves increasing wearing time over several days and weeks. The schedule should be individualized based on the patient's response and can be adjusted based on the presence of normal or abnormal symptoms.

The power of a rigid gas permeable contact lens, determined by the lens's base curve (BC) and its desired sphere power. This power is crucial for correcting refractive errors.

The cylindrical component of an RGP lens power, used to correct astigmatism and achieve optimal vision especially in cases of corneal astigmatism.

The cylindrical power of the cornea measured by a keratometer, this value is crucial for determining the required toricity of the RGP lens.

The spherical component of an RGP lens power, used to correct myopia or hyperopia. It is often adjusted based on the toricity to achieve optimal vision.

The ability of an RGP lens to bend or flex under pressure (like eyelid force). This can benefit the fit and comfort, allowing for a thinner lens.

The ability of an RGP lens to remain centered and stable on the eye, influenced by eyelid forces, surface tension, and lens design. Stability is key for optimal vision.

The thin liquid film that forms between the edge of the RGP lens and the eye, influenced by edge clearance and surface tension. A good meniscus improves lens stability.

The space between the edge of the RGP lens and the eye, affecting lens stability and comfort. A wider clearance promotes better surface tension and stability.

A lens design where the central curve is steeper than the peripheral corneal curve, often used for keratoconus.

A lens design where the central curve is flatter than the peripheral corneal curve, used for irregular corneas.

A fitting method for corneal lenses that involves gradually flattening the lens until it nearly touches the cornea.

The space between the lens edge and the limbus (edge of the cornea) during lens fitting.

The scleral lens should rest evenly on the conjunctiva (white part) without blanching (turning white).

A tinted contact lens designed to enhance or alter the appearance of a normal eye.

A tinted lens used to improve the appearance and potentially correct vision for a disfigured eye.

A general term encompassing both cosmetic and prosthetic contact lenses.

A condition where endothelial cells in the cornea vary in size, with a higher ratio of small to large cells compared to normal. This can be linked to contact lens wear, increasing age, and corneal surgeries.

A condition caused by insufficient oxygen supply to the cornea due to prolonged contact lens wear, leading to corneal edema, epithelial cell death, and desquamation.

A condition characterized by changes in corneal curvature (flattening or steepening) caused by prolonged wear of poorly fitted rigid gas permeable (RGP) lenses.

Signs of Overwear Syndrome include hyperemia (redness), lid edema, central corneal clouding, central corneal punctuate staining, and corneal distortion.

Symptoms of Overwear Syndrome can include severe ocular pain, excessive lacrimation, foreign body sensation, lens intolerance, photophobia, and blurred vision.

Overwear Syndrome requires immediate cessation of lens wear, pain management, antibiotic treatment, and patient education. Refitting with a higher Dk/t lens or a different type of lens (RGP) may be necessary.

Management of Corneal Warpage Syndrome involves ceasing contact lens wear and possibly lens refitting.

Risk factors for Endothelial Polymegethism include increasing age, contact lens wear with low Dk/t, and corneal surgical procedures.