Utilizing know-how to handle corneal challenges earlier than cataract surgical procedure

Topography makes use of reflection-based know-how to calculate keratometry values, whereas tomography scans the cornea with know-how like Scheimpflug images and optical coherence tomography. (Picture Credit score: Adobe Inventory/jayznynism)

Reviewed by Joshua Teichman, MD, MPH, FRCSC

Cataract surgeons ought to develop into properly acquainted with applied sciences that seize topography and tomography of the cornea, in line with Joshua Teichman, MD, MPH, FRCSC, codirector of the cornea, exterior illness and refractive surgical procedure fellowship and assistant professor within the Division of Ophthalmology and Imaginative and prescient Sciences on the College of Toronto, Trillium Well being Companions, Prism Eye Institute, and the Laser Centre Oakville in Ontario, Canada.

Teichman not too long ago spoke on the Toronto Cataract Course, the place he mentioned preoperative assessments previous to cataract surgical procedure that target the cornea and underlined that completely different applied sciences serve completely different functions in these assessments.

Teichman differentiated between the operate of topography and tomography as they apply to cataract surgical procedure. He defined that topography makes use of reflection-based know-how to calculate keratometry values, whereas tomography scans the cornea (much like how an imaging modality would) with know-how like Scheimpflug images and optical coherence tomography. “Tomographers measure elevation after which calculate the corneal data from this knowledge” Teichman mentioned.

When clinicians see a affected person, they’ve to verify issues line up by way of affected person data, the date of the take a look at, the attention examined, high quality indicators, in addition to guaranteeing maps and scales are appropriate, in line with Teichman. He additionally pressured the significance of inspecting the rings picture, stating “rubbish in, rubbish out.”

“You must have a scientific method,” he mentioned. “If you happen to change the scales so [they’re] 1 / 4 of a diopter, all of your sufferers will seem to have keratoconus. If you happen to change it to 2 diopters, everybody goes to seem to have a standard cornea.”

Clinicians additionally want to concentrate on whether or not they’re utilizing an absolute or relative scale, Teichman added. It’s crucial that clinicians confirm their scales and step sizes, overview the values, and examine outcomes with handbook or automated keratometry, biometry, the contralateral eye, and with earlier maps, Teichman mentioned.

Contact lens use

Artifacts similar to eye dryness and get in touch with lens put on might affect the topography and tomography measurements, Teichman defined. The presence of dryness can manifest as irregular mires, knowledge gaps, and/or current as flat areas. “Make sure that [contact lenses] are out [of the eyes] on the time of testing, which can sound apparent however is just not at all times,” he mentioned.

By way of when sufferers ought to take away their contact lenses earlier than having their corneas evaluated previous to cataract surgical procedure, that call should be tailor-made to the affected person and contemplate elements such because the length of contact lens put on and whether or not a affected person wears comfortable or inflexible contact lenses, Teichman mentioned. “You must determine on how lengthy [contact lenses] ought to be out [of the eyes] earlier than testing,” he mentioned, noting a basic information for comfortable contact lenses is from a number of days to 2 weeks, and for inflexible lenses is anyplace from 2 weeks in complete to 1 month per decade of damage.

“When you’ve got a 20-year-old [patient with keratoconus, they] gained’t should have [contact lenses] out very lengthy. [However], when you’ve got a 70-year-old affected person who has been carrying inflexible contact lenses for 50 years, that’s a very long time,” he mentioned.

Maps and lesions

One of many key maps that ought to be employed in preoperative evaluation is the axial or sagittal map, which measures the corneal curvature and relates corneal energy to corneal form. One other is the instantaneous or tangential map, which helps to raised localize lesions, Teichman defined.

Clinicians have to replicate on the goal of the evaluation, similar to whether or not they wish to detect keratoconus, Teichman mentioned. “In case you are screening for keratoconus, you may wish to use an elevation-based machine,” he mentioned.

The presence of epithelial basement membrane dystrophy or Salzmann nodules can even have an effect on outcomes with topography, tomography, and finally outcomes of cataract surgical procedure, in line with Teichman. “Pretreat with a superficial keratectomy,” Teichman mentioned.

It’s essential to concentrate on the assorted lesions or displays that may have an effect on topography show, in line with Teichman. Pterygium is one other frequent discovering previous to cataract surgical procedure and ought to be eliminated previous to surgical procedure, with adequate time al- situated to allow the cornea to normalize previous to repeat testing, he added.

Teichman additionally talked about the significance of imaging sufferers with corneal scars or trauma earlier than cataract surgical procedure. Though many sufferers might have irregular corneas, some might have first rate regularity within the central zone and sufficiently common astigmatism, such {that a} toric IOL might enhance their postoperative outcomes.

Furthermore, Teichman mentioned the assorted challenges in IOL choice in sufferers with keratoconus and the assorted strategies one can use to goal for one of the best outcomes in these difficult eyes.

“Sufferers might also overlook to say they’ve had earlier refractive surgical procedure, and the topography could be your security internet,” he mentioned. “Furthermore, they might not bear in mind [whether] they had been myopic or hyperopic prior. The maps can help with this.”

Clinicians ought to take the chance to customise their printouts for their very own medical makes use of, in line with Teichman. “Don’t let the producer determine [what is displayed on your overview],” Teichman mentioned. “Concentrate on the artifacts. Actually know your scans, your maps, your scales, and management the know-how—not the opposite method round. Customise your show and skim the manuals.”

Joshua Teichman, MD, MPH, FRCSC
P: 905-456-3937
Teichman is an advisory board member for Aequus Prescription drugs Inc; Alcon; Allergan; Labtician Théa; Novartis; Santen Pharmaceutical Co, Ltd; Shire plc; and Solar Pharmaceutical Industries Restricted. He’s a advisor for Aequus Prescription drugs Inc, Alcon, Allergan, Bausch + Lomb, and Novartis. He receives analysis assist from Bausch + Lomb.