Peripheral corneal desiccation (PCD) or 3 and 9 o’clock staining is the horizontal drying of the cornea and/or on the adjacent conjunctiva displaying a hallmark fluorescein stain. Both types cause mostly conjunctival redness and, sometimes, conjunctival oedema. The common subjective symptoms vary from slight foreign body sensation to pain but can also include tearing and dryness symptoms. The more the staining is located on the cornea, the more likely there are to be prevailing subjective symptoms.
Aetiology of 3 and 9 o’clock staining
The major causes of 3 and 9 o’clock staining include poor tear film, OSD (ocular surface disease), inadequate peripheral lens design, and decentred lenses. Patients prone to staining have higher levels of bulbar conjunctival hyperaemia, poor tear film integrity, poor lens centration, and insufficient edge clearance. Chronic 3 and 9 o’clock staining with an RGP corneal lens may lead to vascularised limbal keratitis (VLK).
Management of 3 and 9 o’clock staining
In all cases with 3 and 9 o’clock staining, the eye care practitioner needs to consider different causes. Often this typical staining is multifactorial, consequently making it more difficult to solve. Treatment with lubricating drops should be initiated if a tear abnormality is one of the predominant factors. The design of the contact lens can be modified to enhance wetting and decrease staining. Generally, solutions include thinning the edges, changing the lens diameter back surface design, material components, and the movement of the lens. Remember that by increasing the total diameter, the sagittal depth increases and effectively steepens the fit. As a result, the contact lens has a strong likelihood of binding to the eye, and for this reason, the peripheral curve must be adjusted. Flattening the peripheral curve radius (PCR) and/or increasing the curve width will increase edge clearance. When you make a design change, make it a significant one where; lens diameter ≥ 0.3mm; thickness ≥0.03mm; peripheral curve radius/width ≥1.0/0.2mm. In addition, blinking exercises are encouraged. These changes will bring about: a dramatic decrease in redness of the conjunctiva, no corneal staining, and occasional trace conjunctival staining.
When RGP lenses fail, fit high-DK gas permeable scleral lenses. Scleral lenses will increase lubrication to the entire cornea, provide good movement, acceptable centration and overall lens stability. The patient should report an improvement in comfort. With this lens the conjunctival hyperaemia decreases after 1 week. The wearing time increases to up to 16 hours a day, and the foreign body sensation and dryness symptoms disappears almost completely.
- Patients suffering from increased 3 and 9 o’clock staining have decreased wearing time and marked red eyes in the horizontal meridian.
- The corneal staining location correlates perfectly with the increased focal redness on the conjunctiva.
- The pattern of staining suggests exposure-related desiccation.
- Look for significant nasal and temporal corneal staining abutting the tight peripheral curves with minimal edge lift. Also, it is usually confined to areas of the cornea at the 3 and 9 o’clock positions which are not covered by the contact lens and upper lid.
- Significant conjunctival staining is a potential indicator that in all likelihood the 3 and 9 o’ clock staining would be present because of exposure that extends to the conjunctiva. Scleral lenses are chosen because of RGP contact lens intolerance and working environment.
- Tear film quality and contact lens design are key factors in 3 and 9 o’clock staining troubleshooting.
- A modified, well-fitted lens provides stable comfort for up to 16 hours daily.
- Scleral lenses can be an option when RGPs fail. Additionally, by lubricating the surface, the staining resolves rapidly and the prominent vessels eventually ghost and disappear. There is no need to employ any topical steroids for these patients.
- Living in or relocating to a high altitude climate extremely arid conditions exacerbates 3 and 9 o‘clock staining.
Three and 9 o’ clock staining is drying of the cornea/conjunctiva horizontally arising from inferior contact lens decentration, poor tear film, or inadequate lens design. Patients report increasing redness and lens intolerance. Improving contact lens centration, peripheral curve design and blink exercises are some effective measures.
- Hom MM. Manual of contact lens prescribing and fitting. Boston: Butterworth-Heinemann, 1997. 302, 336.
- Mandell RB. Contact lens practice. 4th ed. Chicago: Charles C Thomas Publisher, 1988. 242, 407.