Contact lenses are medical devices that sit over the eye. They are a great alternative to spectacles and sometimes the only corrective option for people with certain eye conditions like keratoconus. In such cases, spectacles do not provide an optimum vision correction.
A contact lens examination involves several special tests and measurements in addition to a regular eye examination. This helps to check for suitability of contact lenses and help determine the best contact lens type, material and design for the individual requiring one.
A Contactologist who is trained in fitting and dispensing contact lenses performs the contact lens examination. This article describes the components of a contact lens examination.
The contact lens examination involves a comprehensive eye examination to check the overall eye health followed by confirmation of the refractive error. Then special tests and measurements to check for suitability of contact lenses followed by the contact lens trial fitting are done. The following are components of a contact lens examination.
The history in contact lens examination will help the contact lens practitioner understand the individual’s lifestyle and preferences. History about previous contact wear for those who have tried or been wearing contact lenses will also be covered during the history taking.
Questions about any allergies, current medication use, as well as past and current medical history and spectacle correction would be asked.
Comprehensive eye examination
This step is skipped if a comprehensive eye examination has been performed earlier. In this step, the eye’s visual status is assessed, and refraction is done to determine the refractive power of the eyes. This is followed by binocular vision assessment to determine the two eyes’ teaming ability and is then by slit-lamp examination to assess the ocular health.
Contact lens examination
Every eye is different and so are contact lenses. There is no single contact lens that fits all eyes, so the contact lens examination involves specific diagnostic tests that help determine the suitability of lenses.
The following measurements are taken before contact lens trial fitting:
Corneal curvature: The contact lenses are placed over the eye; hence the curvature of the lens should match the curvature of the cornea to ensure optimum fit and comfort for the wearer.
The corneal diameter is also measured by the contact lens practitioner, which helps finalize the size of the contact lens. A keratometer is a simple instrument that measures the corneal curvature over a small region. This measurement is sufficient for fitting the majority of the regular contact lenses. However, a highly irregular cornea requires corneal topography.
The corneal topographers are advanced instruments that map the entire cornea and are a mandatory diagnostic test to fit speciality contact lenses.
Pupil size: The size of the pupil varies under different illumination levels. The pupil size is measured using a special ruler. This aids the practitioner in choosing the size and design of the contact lens.
Tear film assessment: Tear film plays a vital role in contact lens wear. It keeps the cornea and contact lens moist, the lack or deficiency of which could lead to discomfort to the wearer. A pre-existing dry eye could get aggravated with few types of contact lenses. Hence tear film assessment is critical prior to contact lens trial and wear. The contact lens practitioner would perform couple of tests to assess the tear film.
Contact Lens trial: Once all the preliminary examination and measurements of the eye are taken, the next step involves a trial of the contact lenses on the patient’s eyes. The practitioner first decides the material of the contact lens and then chooses a particular brand/design based on the preliminary data collected from the patient, which includes the lifestyle and preferences of the wearer.
Sometimes several lenses are tried before arriving at the final lens material and brand/design. The fit on the eye is assessed under a slit lamp after the wearer has adapted with the contact lens wear.
The entire contact lens trial can last from 30 minutes to a couple of hours depending upon the level of adaptation by the wearer and the type of contact lens used. Speciality contact lens trials usually take a long time during the trial and may last even 4 to 6 hours at times.
Once the fit of the contact lens is satisfactory, the power of the final lens is determined as trial lenses are not available for all refractive powers. The practitioner notes the final contact lens prescription, and an order is placed.
The spectacle and contact lens prescription are not similar and differ in most cases. A contact lens practitioner conducts preliminary examination and tests. They have adequate knowledge and experience to help choose and recommend the right contact lens based on the eye’s condition.
Complex softwares’ are a great help to simulate the fit of a lens even before the actual lens is made. They use the corneal topographer’s data and estimate the fit with excellent accuracy. This method is used for designing most of the speciality lenses.
Contact lens dispensing visit: During the contact lens dispensing visit, the contact lens practitioner teaches the wearer the insertion and removal technique for the contact lens and again assesses the fit of the final lens.
Once the vision and fit of the lens are satisfactory and adequate training of insertion and removal techniques has been given, the final contact lenses are dispensed to the wearer. The practitioner provides special instructions about care and maintenance. The wearer should adhere to these to ensure that the life of the lenses and the health of the eyes are maintained.
Non-compliance to these instructions could lead to problems in the eye and sometimes may lead to adverse reactions too. The use of correct contact lens solution, maintenance of the contact lens cases, and their replacement schedules are given by the practitioner. Every contact lens has a life, and the wearer should adhere to replacement schedules.
Follow-up visits: The contact lens practitioner will schedule a follow-up visit/appointment to check if the contact lenses fit fine and provide optimum vision and comfort to the wearer whilst maintaining the eyes’ health.
Sometimes early changes or reactions to the contact lens or solution could be identified during a follow-up visit, and the contact lens practitioner could suggest alternative options.
It is essential to attend all follow-up visits scheduled by the contact lens practitioner as any problem could be detected at the earliest. A resolution would be provided immediately rather than waiting for the condition to worsen.
Any discomfort, redness, or excessive tearing during contact lens wear should immediately be reported to the eye care practitioner. A poorly fitting lens could damage the eyes in the long run; hence a contact lens examination is critical for every contact lens wearer.
Contact lenses are safe devices and can be worn in all age groups. Schedule an appointment with a contact lens practitioner to help decide and recommend the right pair of contact lenses.